Sediment Transport and Deposition Algae, Phytoplankton and Chlorophyll SHARE88 14 14 00Water quality testing is an important part of environmental monitoring. When water quality is poor, it affects not only aquatic life but thesurrounding ecosystem as well.These sections detail all of the parameters that affect the quality of water in the environment. These properties can be physical, chemical or biologicalfactors. Physical properties of water quality include temperature and turbidity. Chemical characteristics involve parameters such as pH and dissolvedoxygen. Biological indicators of water quality include algae and phytoplankton. These parameters are relevant not only to surface water studies ofthe ocean, lakes and rivers, but to groundwater and industrial processes as well.Water quality monitoring can help researchers predict and learn from natural processes in the environment and determine human impacts on anecosystem. These measurement efforts can also assist in restoration projects or ensure environmental standards are being met.The following chapters will discuss each water quality parameter specifically. Each page defines what the parameter is, where it comes from and whyit is important to measure.Water Quality ChaptersAlgae, Phytoplankton and ChlorophyllCDOMConductivity, Salinity and Total Dissolved SolidsDissolved OxygenNutrients: Phosphorus and Nitrogen as Nitrate and AmmoniaWater QualityTo search type and hit enterWater Quality - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/ 1 / 80 Sediment Transport and Deposition Algae, Phytoplankton and Chlorophyll Water quality affects the surrounding environment.pHPhotosynthetically Active Radiation and Solar RadiationTurbidity, Total Suspended Solids and ClarityWater TemperatureMeasurement methods and technology can be found in the section: Methods and Equipment.Parameters ParametersHydrology HydrologyWater Quality Water QualityAlgae, Phytoplankton and Chlorophyll Algae, Phytoplankton and ChlorophyllConductivity, Salinity & Total Dissolved Solids Conductivity, Salinity & Total Dissolved SolidsDissolved Oxygen Dissolved OxygenpH of Water pH of WaterPhotosynthetically Active Radiation and Solar Radiation Photosynthetically Active Radiation and Solar RadiationTurbidity, Total Suspended Solids & Water Clarity Turbidity, Total Suspended Solids & Water ClarityWater Temperature Water TemperatureWeather and Atmosphere Weather and AtmosphereWater Quality - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/ 2 / 80 Water Quality EquipmentGet Discount CodeMethods and Equipment Methods and EquipmentMonitoring Applications Monitoring ApplicationsReferences References2015 FONDRIEST ENVIRONMENTAL INC. | QUESTIONS? CALL 888.426.2151 OR EMAIL 2015 FONDRIEST ENVIRONMENTAL INC. | QUESTIONS? CALL 888.426.2151 OR EMAIL 2015 FONDRIEST ENVIRONMENTAL INC. | QUESTIONS? CALL 888.426.2151 OR EMAIL CUSTOMERCARE@FONDRIEST.COMCUSTOMERCARE@FONDRIEST.COMCUSTOMERCARE@FONDRIEST.COMWater Quality - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/ 3 / 80 Water Quality Conductivity, Salinity & Total Dissolved Solids SHARE66 14 14 55Chapter Overview:What are Algae?What are Phytoplankton?MicroalgaeCyanobacteria: Blue-Green AlgaeWhat is Chlorophyll?Other Color PigmentsWhat is Photosynthesis?Underwater PhotosynthesisWhat affects Photosynthesis?Why are Phytoplankton Important?Oceanic Food WebOxygen ProductionCarbon Fixation and the ClimateTypical Levels and Factors that Influence ProductivitySunlight InfluenceNutrient InfluenceTypical Freshwater LevelsAlgae, Phytoplankton and ChlorophyllTo search type and hit enterAlgae, Phytoplankton and Chlorophyll - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/algae-phytoplankton-chlorophyll/ 4 / 80Algae are sometimes considered protists, while other times they are classifiedas plants or choromists. Phytoplankton are made up of single-celled algae andcyanobacteria.Typical Saltwater LevelsConsequences of Unusual LevelsAlgal Blooms and Red TidesWhat Causes an Algal Bloom?Red TidesToxinsFilamentous AlgaeOxygen Depletion and Fish KillsHow do you Measure Phytoplankton?Measuring ChlorophyllMeasuring Blue-Green AlgaePhytoplankton and Algae Measurement MethodsChlorophyll SensorsApplications What are Algae?Algae are aquatic, plant-like organisms. They encompass a variety of simple structures, from single-celled phytoplankton floating in the water, tolarge seaweeds (macroalgae) attached to the ocean floor. Algae can be found residing in oceans, lakes, rivers, ponds and even in snow, anywhereon Earth.So what makes algae only plant-like, instead of plants? While algae are often called primitive plants, other terms, like protists, can be used. Protistmay be a more accurate term, particularly for the single-celled phytoplankton. However, larger, more complex algae, including kelp and chara, areoften mistaken for submerged plants.The difference between these seaweeds and submerged plants is in their structure. Macroalgae are simpler, and attach themselves to the seabedwith a holdfast instead of true roots. Aquatic plants, whether floating, submerged, or emergent (starting in the water and growing out) havespecialized parts such as roots, stems and leaves. Most plants also have vascular structures (xylem and phloem), which carry nutrients throughoutthe plant. While algae contain chlorophyll (like plants), they do not have these specialized structures.As algae can be single-celled, filamentous (string-like) or plant-like, they areoften difficult to classify. Most organizations group algae by their primarycolor (green, red, or brown), though this creates more problems than itsolves. The various species of algae are vastly different from each other,not only in pigmentation, but in cellular structure, complexity, and chosenenvironment. As such, algal taxonomy is still under debate, with someorganizations classifying algae under different kingdoms, including Plantae,Protozoa and Chromista. While the overarching kingdom classificationis not always agreed upon, the species, genus, family, class and phylum ofeach alga generally are.To further complicate this nomenclature, single-celled algae often fall underthe broad category of phytoplankton. What are phytoplankton?Phytoplankton are microorganisms that drift about in water. They aresingle-celled, but at times they can grow in colonies large enough to beseen by the human eye. Phytoplankton are photosynthetic, meaning they have the ability to use sunlight to convert carbon dioxide and waterinto energy. While they are plant-like in this ability, phytoplankton are not plants. The term single-celled plants is a misnomer, and should not beused. Instead, phytoplankton can be divided into two classes, algae and cyanobacteria. These two classes have the common ability ofphotosynthesis, but have different physical structures. Regardless of their taxonomy, all phytoplankton contain at least one form of chlorophyll(chlorophyll A) and thus can conduct photosynthesis for energy.Phytoplankton, both algae and cyanobacteria, can be found in fresh or saltwater. As they need light to photosynthesize, phytoplankton in anyenvironment will float near the top of the water, where sunlight reaches. Most freshwater phytoplankton are made up of green algae andcyanobacteria, also known as blue-green algae. Marine phytoplankton are mainly comprised of microalgae known as dinoflagellates and diatoms,though other algae and cyanobacteria can be present. Dinoflagellates have some autonomous movement due to their tail (flagella), but diatoms24843844,54,6,8,9616111013101312Algae, Phytoplankton and Chlorophyll - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/algae-phytoplankton-chlorophyll/ 5 / 80are at the mercy of the ocean currents. MicroalgaeThere are thousands of species of planktonic algae, or microalgae, floating in water all over the world. Green algae, diatoms and dinoflagellates are themost well-known, though other microalgae species include coccolithophores, cryptomonads, golden algae, yellow-green algae and euglenoids.There are so many diatoms drifting in the oceans that their photosynthetic processes produce about half of Earths oxygen. While diatoms anddinoflagellates are forms of planktonic algae, they can be incorrectly classified as red or brown algae. Red and brown algae are not consideredphytoplankton as they are not free-floating. True red and brown algae are rarely single-celled, and remain attached to rock or other structuresinstead of drifting at the surface. Multicellular green algae is also not considered phytoplankton for the same reasons. To be considered aphytoplankton, the algae needs to use chlorophyll A in photosynthesis, be single-celled or colonial (a group of single-cells), and live and die floating inthe water, not attached to any substrate.Phytoplankton come in many different structures, but all except for cyanobacteria are algae. Collage adapted from drawings andmicrographs by Sally Bensusen, NASA EOS Project Science Office Cyanobacteria: Blue-Green AlgaeDespite their ability to conduct photosynthesis for energy, blue-green algae are a type of bacteria. This means that they are single-celled,prokaryotic (simple) organisms. Prokaryotic means that the cyanobacteria do not have a nucleus or other membrane-bound organelles within theircell wall.Cyanobacteria are the only bacteria that contain chlorophyll A, a chemical required for oxygenic photosynthesis (the same process used by plantsand algae). This process uses carbon dioxide, water and sunlight to produce oxygen and glucose (sugars) for energy. Chlorophyll A is used tocapture the energy from sunlight to help this process. Other bacteria can be considered photosynthesizing organisms, but they follow a differentprocess known as bacterial photosynthesis, or anoxygenic photosynthesis. This process uses bacteriochlorophyll instead of chlorophyll A. Thesebacteria cells use carbon dioxide and hydrogen sulfide (instead of water) to manufacture sugars. Bacteria cannot use oxygen in photosynthesis, andtherefore produce energy anaerobically (without oxygen). Cyanobacteria and other phytoplankton photosynthesize as plants do, and producethe same sugar and oxygen for use in cellular respiration.In 2011, Lake Erie experienced the worst blue-green algae bloom in decades (Photo Credit: MERIS/NASA; processed byNOAA/NOS/NCCOS )121991,17151,1414 1918Algae, Phytoplankton and Chlorophyll - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/algae-phytoplankton-chlorophyll/ 6 / 80The different forms of chlorophyll absorb slightly different wavelengthsfor more efficient photosynthesis.Each pigment absorbs and reflects different wavelengths, butthey all act as accessory pigments to chlorophyll A inphotosynthesis.In addition to chlorophyll A, blue-green algae also contain the pigments phycoerythrin and phycocyanin, which give the bacteria their bluish tint(hence the name, blue-green algae). Despite not having a nucleus, these microorganisms do contain an internal sac called a gas vacuole that helpsthem to float near the surface of the water. What is chlorophyll?Chlorophyll is a color pigment found in plants, algae and phytoplankton. This molecule is used in photosynthesis, as a photoreceptor.Photoreceptors absorb light energy, and chlorophyll specifically absorbs energy from sunlight. Chlorophyll makes plants and algae appear greenbecause it reflects the green wavelengths found in sunlight, while absorbing all other colors.However, chlorophyll is not actually a single molecule. There are 6 different chlorophylls that have been identified. The different forms (A, B, C, D,E and F) each reflect slightly different ranges of green wavelengths. Chlorophyll A is the primary molecule responsible for photosynthesis. Thatmeans that chlorophyll A is found in every single photosynthesizing organism, from land plants to algae and cyanobacteria. The additionalchlorophyll forms are accessory pigments, and are associated with different groups of plants and algae and play a role in their taxonomic confusion.These other chlorophylls still absorb sunlight, and thus assist in photosynthesis. As accessory pigments, they transfer any energy that theyabsorb to the primary chlorophyll A instead of directly participating in the process.Chlorophyll B is mainly found in land plants, aquatic plants and green algae. Inmost of these organisms, the ratio of chlorophyll A to chlorophyll B is 3:1. Dueto the presence of this molecule, some organizations will group the green algaeinto the Plant Kingdom. Chlorophyll C is found in red algae, brown algae, anddinoflagellates. This has lead to their classification under the KingdomChromista. Chlorophyll D is a minor pigment found in some red algae, while therare Chlorophyll E has been found in yellow-green algae. Chlorophyll F wasrecently discovered in some cyanobacteria near Australia. Each of theseaccessory pigments will strongly absorb different wavelengths, so their presencemakes photosynthesis more efficient. Other Color PigmentsChlorophyll is not the only photosynthetic pigment found in algae andphytoplankton. There are also carotenoids,and phycobilins (biliproteins). These accessory pigments are responsible for other organism colors, suchas yellow, red, blue and brown. Like chlorophylls B, C, D, E and F, these molecules improve light energy absorption, but they are not a primary partof photosynthesis. Carotenoids can be found in nearly every phytoplankton species, and reflect yellow, orange and/or red light. There are twophycobilins found in phytoplankton: phycoerythrin and phycocyanin. Phycocyanin reflects blue light and is responsible for cyanobacterias commonname blue-green algae. Phycoerythrin reflects red light, and can be found in red algae and cyanobacteria.Some algae will appear green despite the presence of these accessory pigments. Just asin plants, the chlorophyll in algae has a stronger relative absorption than the othermolecules. Like a dominant trait, the more intense, reflected green wavelengths canmask the other, less-reflected colors. In green algae, chlorophyll is also found at ahigher concentration relative to the accessory pigments. When the accessory pigmentsare more concentrated (such as in red algae, brown algae and cyanobacteria), the othercolors can be seen. What is Photosynthesis?Photosynthesis is the process by which organisms use sunlight to produce sugars forenergy. Plants, algae and cyanobacteria all conduct oxygenic photosynthesis. Thatmeans they require carbon dioxide, water, and sunlight (solar energy is collected bychlorophyll A). Plants and phytoplankton use these three ingredients to produce glucose(sugar) and oxygen. This sugar is used in the metabolic processes of the organism, andthe oxygen, produced as a byproduct, is essential to nearly all other life, underwater and on land.151320151,221,151201,2112115422201520231,141,24Algae, Phytoplankton and Chlorophyll - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/algae-phytoplankton-chlorophyll/ 7 / 80Blue and red light are used more efficiently in photosynthesis.Temperature affects the photosynthetic rates of different algae.Photosynthesis uses water, carbon dioxide and sunlight to produceenergy and oxygen. Underwater PhotosynthesisPhytoplankton drifting about below the surface of the water still carry out photosynthesis. This process can occur as long as enough light is availablefor the chlorophyll and other pigments to absorb. In the ocean, light can reach as far as 200m below the surface. This region where sunlight canreach is known as the euphotic zone. Phytoplankton and other algae can be found throughout this zone. What Affects Photosynthesis?As light is required for photosynthesis to occur, the amount of light available will affect this process. Photosynthetic production peaks during the dayand declines after dark. However, not all light can be used for photosynthesis. Only the visible light range (blue to red) is consideredphotosynthetically active radiation. Ultraviolet light has too much energy for photosynthesis, and infrared light does not have enough. Ifphytoplankton are exposed to too much UV light, the excessive solar energy can break molecular bonds and destroy the organisms DNA.Within the visible light spectrum, chlorophyll strongly absorbs red and blue lightwhile reflecting green light. This is why phytoplankton, particularlycyanobacteria, can thrive at the bottom of the euphotic (sunlit) zone, whereonly blue light can reach. As blue light is both high in energy and stronglyabsorbed by chlorophyll, it can be used effectively in photosynthesis.Turbidity, or the presence of suspended particles in the water, affects theamount of light that reaches into the water. The more sediment and otherparticles in the water, the less light will be able to penetrate. With less lightavailable, photosynthetic production will decrease. In turbid water,photosynthesis is more likely to occur at the waters surface than on thelakebed, as more light is available. .Watertemperature willalso affectphotosynthesisrates. As a chemical reaction, photosynthesis is initiated and sped up by heat. Asphotosynthesis production increases, so will phytoplankton reproduction rates.This factors into the large, seasonal swings of phytoplankton populations.However, the extent to which temperature affects photosynthesis in algae andcyanobacteria is dependent on the species. For all phytoplankton, photosyntheticproduction will increase with the temperature, though each organism has a slightlydifferent optimum temperature range. When this optimum temperature isexceeded, photosynthetic activity will in turn be reduced. Too much heat willdenature (break down) the enzymes used during the process, slowing downphotosynthesis instead of speeding it up. Why are Phytoplankton Important?Microscopic phytoplankton play some of the biggest roles in climate control, oxygen supply and food production. These single-celled organisms areresponsible for more than 40% of Earths photosynthetic production. That process uses up carbon dioxide, which helps regulate CO2 levels in theatmosphere, and produces oxygen for other organisms to live. 25241274811 2613131262828Algae, Phytoplankton and Chlorophyll - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/algae-phytoplankton-chlorophyll/ 8 / 80Phytoplankton create their own energy from sunlight. All otherorganisms consume them, whether directly or indirectly as acarbon source.Plants, algae and cyanobacteria all engage in oxygenic photosythesis(top equation), which means that they require water and releaseoxygen. Precambrian bacteria used hydrogen sulfide instead of water(bottom equation) and did not release oxygen as a byproduct. Oceanic Food WebPhytoplankton make up the foundation of the oceanic food web. A food web is acomplex net of organisms and food chains (who-eats-who). To survive, every livingthing needs organic carbon. Organic carbon can be found in many different thingsincluding sugars (glucose = C6H12O6), plants and animals. Phytoplankton producetheir required sugar through photosynthesis. As they are able to produce their ownenergy with the help of light, they are considered autotrophic (self-feeding).Phytoplankton and other autotrophs are called primary producers, and make up thebottom of the food web. These organisms are called primary because all otherorganisms rely on them (directly or indirectly) as a food source.Phytoplankton are generally consumed by zooplankton and small marine organismslike krill. These creatures are then consumed by larger marine organisms, such as fish. This chain continues up to apex predators, including sharks, polar bears andhumans. Oxygen ProductionDuring the photosynthetic process, phytoplankton produce oxygen as abyproduct. Due to their vast and widespread populations, algae and cyanobacteriaare responsible for approximately half of all the oxygen found in the ocean and in our atmosphere. Thus oceanic lifeforms not only feed off thephytoplankton, but also require the dissolved oxygen they produce to live.Before plants, algae and phytoplankton used water for photosynthesis, bacteriaused H2S and other organic compounds to fix CO2. Early cyanobacteria werethe first organism to use water to fix carbon. The use of H2O introduced freeoxygen (O2) into the environment as a byproduct. The start of oxygenicphotosynthesis was a turning point for Earths history. This process slowlychanged the inert Precambrian atmosphere into the oxygen-rich environmentknown today. Though microscopic, early cyanobacteria have made apermanent impact on the Earths environment. Carbon Fixation and the ClimateIn addition to providing food and oxygen for nearly all life on Earth,phytoplankton help to regulate inorganic carbon (carbon dioxide) in theatmosphere. During photosynthesis, carbon dioxide and water molecules areused to make sugar for energy. The process of incorporating inorganic carbon into organic carbon (glucose and other biologically usefulcompounds) is called carbon fixation, and is part of the biological carbon pump.As carbon fixation and oxygen production are part of the same process, the extent of phytoplanktons participation is on the same scale.Phytoplankton consume a similar amount of carbon dioxide as all land plants combined. While phytoplankton can pull carbon dioxide from theatmosphere or the ocean, it will have a similar effect. CO2 that is taken from the water is replaced by CO2 from the atmosphere, thanks to Henryslaw (the dissolved gas content of water is proportional to the percentage of gas in the air above it. This consumption helps keep carbon dioxidelevels in check, reducing its presence as a greenhouse gas.When carbon dioxide is consumed, the carbon molecules become incorporated intothe phytoplanktons structure, allowing the organism to function and grow. If thephytoplankton is not eaten by another organism (passing on the carbon up thefood chain), then it will sink into the ocean when it dies. As with other detritus (non-living organic material), the phytoplankton will be decomposed by bacteria, and thecarbon is either released back into the ocean as dissolved carbon dioxide oreventually deposited into the seafloor sediment. Thanks to phytoplankton, thisbiological carbon pump removes approximately 10 trillion kilograms (10 gigatonnes)of carbon from the atmosphere every year, transferring it to the ocean depths.In climate terms, this process helps to maintain global surface temperatures.29112929,3010313131171111322811331111Algae, Phytoplankton and Chlorophyll - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/algae-phytoplankton-chlorophyll/ 9 / 80Algae and cyanobacteria help to regulate the climate by fixingcarbon dioxide from the atmosphere. This carbon is thenconsumed or decomposed by other organisms, making its waythrough the cycle until it is released as dissolved carbon dioxide inwater or deposited in sediment.Dissolved oxygen concentrations will increase during the day dueto photosynthesis production and decline at night after the sunsets and the phytoplankton engage in respiration instead.Eutrophication is caused by an increase in nutrient levels. This canlead to an algal bloom and can cause low levels of dissolvedoxygen.Without this cycle, atmospheric CO2 would rise approximately 200 ppm (currentlevels are around 400 ppm). Even small changes in phytoplankton populationscould have an effect on the atmosphere and world climate. Typical Levels and Factors that InfluenceProductivityPhytoplankton populations and their subsequent photosynthetic productivity will fluctuate due to a number of factors, most of which are part ofseasonal changes. The largest influence on phytoplankton levels is nutrient scarcity. While sunlight levels affect productivity, nutrient levelsaffect phytoplankton growth and populations. While any one phytoplankton only lives for a few days, a population boom can last for weeks underthe right conditions.As phytoplankton populations grow and shrink seasonally, typical concentrations vary not only by location but from month to month. Expectedlevels should be based on local, seasonal data from previous years. While changes within the same calendar year are normal, populations should stayconsistent with previous seasonal fluctuations from year to year. If phytoplankton concentrations are abnormally high or low for a season, it mayindicate other water quality concerns that should be addressed. Sunlight InfluencePhytoplankton require sunlight for photosynthesis. If sunlight is limited, phytoplankton productivity will decrease. This can be seen in a daily cycle asoxygen levels fluctuate with light levels throughout the day. However, if sunlight is unavailable or minimal for an extended period of time, aquatic lifewill consume dissolved oxygen quicker than phytoplankton can restore it, leading to a plummet in dissolved oxygen levels. Phytoplankton areresponsible for much of the dissolved oxygen found in surface waters. As oxygen is required for fish and other aquatic organisms, a decrease inphotosynthesis productivity is detrimental to aquatic populations. Without phytoplankton, the oxygen supply of the ocean would be cut in half. Inboth fresh and saltwater, a lengthy decrease in phytoplanktonic productivity can lead to a fish kill (massive fish die-off).Although phytoplankton require sunlight for photosynthesis and oxygen production,too much light can be harmful to photosynthetic production. Ultraviolet light from thesun can damage the phytoplanktons DNA, inhibiting the photosynthetic pathway.On very bright days, UV-B radiation can diminish photosynthesis by 8.2%. This iswhy photosynthesis rates peak during the morning, and decrease at noon (when theradiation levels are highest). Nutrient InfluenceWhile phytoplankton rely on photosynthesis to produce sugar for energy, they stillneed other nutrients to grow and reproduce. These nutrients are typicallyphosphorus, nitrogen and iron, though some species also require silicon, calciumand other trace metals. The more nutrients (particularly phosphorus) that arepresent in a body of water, the more algae and phytoplankton that will grow. Anincrease in the nutrient concentration of a body of water is called eutrophication.Eutrophication is often an indicator of agricultural runoff, which can raisephosphorus and nitrogen concentrations to very high levels. If there are too manynutrients, the algae will form a bloom, which can be very detrimental to water qualityand aquatic health.The lack of iron in the open ocean limits phytoplankton growth. Nitrogen andphosphorus are also scarce away from coastlines, and can be limiting factors as well. However, ocean circulation can cause an upwelling, which moves deep, nutrient-rich water up into the photic (sunlight zone), replacing the nutrient-depleted surfacewater. Upwelling, seasonal ice melts and agricultural runoff can all increase nutrientlevels, leading to an increase in phytoplankton populations. 33,341130 131130110135351711,137137101330Algae, Phytoplankton and Chlorophyll - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/algae-phytoplankton-chlorophyll/ 10 / 80Typical Freshwater LevelsIn temperate fresh waters, growth is limited in winter because light and temperatures are low. A large increase in the spring normally occurs as lightconditions improve and water begins to mix. In the summer, phytoplankton flourish until the nutrient supply begins to run low. In tropical lakes,the phytoplankton distribution is fairly constant throughout the year and seasonal population changes are often very small. In temperate andsubpolar waters, the seasonal fluctuations are normally fairly large. Fluctuations in population also occur if agricultural runoff brings additionalnutrients into a body of water. Typical Saltwater LevelsSaltwater phytoplankton can be found all over the world, living in the photic (sunlit zone) of the ocean. Cyanobacteria prefer to live near the bottomof this zone, closest to the nutrient-rich deep water while still receiving enough sunlight for photosynthesis. However, in any marine environment,phytoplankton populations vary not only by season but by region.Phytoplankton can be found along coastline and areas of upwelling. Data: Average chlorophyll concentration July 2002- May 2010,MODIS,(Photo Credit: NASA, Jesse Allen & Robert Simmon)Algae blooms can occur near the poles in the spring, when there is plenty of sunlight and the melting sea ice leaves behind nutrient-rich freshwater. This melting process also fuels the oceanic convection, or circulation. In coastal and open-ocean environments, oceanic circulation isresponsible for phytoplankton concentrations.This circulation can cause upwelling (bringing nutrient-rich water to the surface) and instigates phytoplankton transportation. Like sea ice melting,upwelling is a seasonal occurrence. The extent and location of upwells are based on wind patterns, which cause currents across the globe. Surfacewater is carried away from coastlines by currents, and is replaced by cold, nutrient-rich water from below.In many coastal regions, southerly winds cause this coastal upwelling in late summer and autumn. As upwelling brings nutrient-rich water up to thesurface, phytoplankton blooms often appear at this time. Oceanic circulation and upwelling ensures that the coastal environments have the highestrates of primary production in the ocean. Tides, flooding and currents all encourage higher nutrient levels in the photic zone. Consequences of Unusual LevelsPhytoplankton are an important aspect of a healthy body of water. Algae and cyanobacteria help to provide oxygen and food for aquatic organisms. As a key component, an imbalance of phytoplankton levels can cause major problems. If too many nutrients are available, it can trigger an algalbloom. Algal blooms and overproduction of phytoplankton can cause toxic red tides and fish kills. On the other hand, phytoplanktonicproductivity can be limited by a lack of required reactants such as sunlight. This decrease in productivity can also lead to fish kills. Algal Blooms and Red TidesAn algal bloom is a sudden increase in the concentration of phytoplankton. During a bloom, clear water can become covered with phytoplanktonwithin days. These algal blooms can grow large enough to be seen from a satellite, covering hundreds of square kilometers. Algal blooms comein many colors from green to red, brown, blue, white or purple.11130 3811373613 131212339 1143Algae, Phytoplankton and Chlorophyll - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/algae-phytoplankton-chlorophyll/ 11 / 80Mussels, clams and other mollusks can accumulate toxinsfrom phytoplankton.Under the right conditions, algal blooms can last one week to an entire summer, despite the short, few-day life span of phytoplankton. A singlebloom will only last one to two weeks, as the phytoplankton population will die without the proper oxygen and nutrient levels. However, if the waterconditions stay favorable, successive blooms can occur and appear to be one continuous population. Algal blooms are most common in latesummer and early fall. What Causes an Algal Bloom?There are several causes that can contribute to an algal bloom. These blooms can occur seasonally, after an upwelling of nutrient-rich water, or dueto pollution such as agricultural runoff. In both cases, the water becomes saturated with nutrients, creating an ideal environment for phytoplanktonproductivity. Even natural causes can trigger an algal bloom, such as a rainstorm followed by warm, sunny weather. Rain can contribute runoff,or encourage the mixing of nutrient-depleted and nutrient-rich layers of water. When nutrient levels rise, phytoplankton growth is no longernutrient-limited and a bloom may occur. Red TidesIf a phytoplankton concentration stays steady after the initial bloom, it may become a red tide. While some blooms are harmless, others mayproduce toxins that endanger aquatic life and humans. This harmful algal bloom is known as a red tide. While red tides specifically refer to harmfulalgal blooms (HABs), they are often simply associated with the discoloration due to a large concentration of phytoplankton. Although known asa red tide, the discoloration from a harmful algal bloom is not always red. The color of the tide depends on the pigments present in thephytoplankton. In some cases, the bloom cannot be seen by the human eye, though it is still releasing toxins.Red tides and the toxins they release can have a direct or indirect impact on the health of humans and other organisms. Some species ofphytoplankton can suffocate fish during a bloom by clogging or irritating the fishes gills, preventing them from taking in oxygen. These harmfulalgal blooms can also cause shellfish poisoning in humans and other adverse effects. Even during non-toxic algal blooms, the aquatic environmentcan be compromised. Massive levels of phytoplankton respiration and decomposition can reduce dissolved oxygen to unsustainable levels, resultingin the deaths of other aquatic creatures. ToxinsThe phytoplankton that cause a red tide are usually comprised of dinoflagellates, diatoms or cyanobacteria. Certain species of these phytoplanktoncan contain harmful toxins that can affect humans and other animals. At normal levels, heterotrophic bacteria in the water break down the toxins inthese organisms before they can become dangerous. When an algal bloom appears, the concentration of toxins increases faster than the bacteriacan break it down.Some of these toxins cause mild problems if consumed by humans, such as headaches andupset stomachs, while others can cause serious neurological and hepatic symptoms that canlead to death. These effects can be caused by direct or indirect contact with an algal bloom.Direct exposure can occur from swimming or drinking affected water. Indirect contact canoccur from eating animals that have been exposed to the toxic bloom, particularly shellfish.Shellfish are susceptible to toxins because they are filter feeders. Filter feeders ingest food bytaking up the water surrounding them and then filtering out what they do not wish to ingest. This method accumulates toxins inside the shellfish system. Organisms that eat the shellfish(including humans) are consuming the concentrated toxins, which can reach deadly levels. Filamentous Algal BloomFilamentous algae is a collection of microscopic algae that clumps together in strings and mats at the surface of the water. These accumulationscan vary from a small, woolly patch near shore to a widespread, slimy green covering. Filamentous algae are often referred to as pond scum, andappear in eutrophic (nutrient-rich) bodies of water. More often than not, filamentous algae are more of a nuisance than a danger. They aresomewhat more controllable in that the algae clumps can be physically removed from the water. While large filamentous algal blooms will stopsunlight from penetrating the water and reaching submerged plants, the biggest threat associated with them is oxygen depletion. 113936 11336,4336 4336131351515252777,4444Algae, Phytoplankton and Chlorophyll - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/algae-phytoplankton-chlorophyll/ 12 / 80 Oxygen Depletion and Fish KillsIf an algal bloom appears, a fish kill can occur shortly thereafter due to the environmental stresses caused by the bloom. A fish kill, also known as afish die-off is when a large concentration of fish die. The most common cause of this event is lack of oxygen.If a phytoplankton population grows to an excessive amount, the amount of usable oxygen inthe water can be depleted. Oxygen depletion has two algal-bloom-related causes: respirationand decomposition. Algae and cyanobacteria consume oxygen at night (respiration) whenthere is not light for photosynthesis. If there is a bloom, the phytoplankton and other aquaticorganisms (like fish) can consume more oxygen than is produced. Likewise, if large portions ofthe algal bloom die off at once, bacteria will start to consume oxygen in order to decomposethe dead algae. This can reduce oxygen concentrations to below sustainable levels. If oxygenlevels get too low, fish and other aquatic creatures may die. How do you Measure Phytoplankton?While phytoplankton concentrations can be measured by sampling, this can be difficult andtime-consuming. Plankton nets do not always catch the smallest of phytoplankton, and do not provide an accurate estimate of water volume.Box or tube traps offer an exact volume, but require lab sedimentation or settling chambers to concentrate the algae population for counting.Furthermore, phytoplankton can be found at multiple depths in the water column, which requires multiple sampling efforts and risks missing layers ofphytoplankton in between sample depths. The main advantage of sampling phytoplankton is the ability to analyze and identify the species present. Measuring ChlorophyllAn easier and more efficient method is to use a chlorophyll sensor. As all phytoplankton have chlorophyll A, a chlorophyll sensor can be used todetect these organisms in-situ. In addition to providing immediate data, it can be used for continuous or long-term monitoring and recording.However, as a chlorophyll sensor assumes all algae and cyanobacteria have the same levels of chlorophyll A, it only provides a rough estimate ofbiomass. It also cannot be used to identify specific species.Even with its limitations, in-situ chlorophyll measurements are recommended in Standard Methods for the Examination of Water and Wastewater toestimate algal populations. Chlorophyll sensors are also an in-situ method for determining the trophic state (nutrient-rich, stable, or nutrient-poor)of an aquatic system. A high chlorophyll measurement is an indicator of eutrophication.Chlorophyll is measured in micrograms per liter (g/l). Chlorophyll sensors rely on fluorescence to estimate phytoplankton levels based on chlorophyllconcentrations in a sample of water. Fluorescence means that when the chlorophyll is exposed to a high-energy wavelength (approximately 470nm), it emits a lower energy light (650-700 nm). This returned light can then be measured to determine how much chlorophyll is in the water,which in turn estimates the phytoplankton concentration. These estimates are then used to develop parameter limits for bodies of water. As anexample, the New Hampshire Department of Environmental Services provides the following chlorophyll guidelines for river quality: a chlorophyllmeasurement below 7 g/l is within a desirable range. 7-15 g/l is less than desirable, while over 15 g/l is considered problematic. Measuring Blue-Green AlgaeBlue-green algae, or cyanobacteria, are the only phytoplankton that contain phycocyanin and phycoerythrin, making the pigments good indicatorsof the amount of cyanobacteria in a body of water. While chlorophyll measurements can be used to estimate entire phytoplankton populations enmasse, the accessory pigments phycocyanin and phycoerythrin can be measured to estimate cyanobacteria concentrations specifically. Marinecyanobacteria have higher levels of phycoerythrin, while freshwater species have dominating amounts of phycocyanin.Like chlorophyll sensors, blue-green algae sensors rely on fluorescence to detect the pigment concentration. Phycoerythrin sensors use awavelength around 540 nm, while phycocyanin sensors emit a wavelength at 600 nm. Due to the differences in secondary pigmentconcentrations between species, it is recommended to use the phycocyanin BGA sensor in freshwater applications, and the phycoerythrin BGAsensor in saltwater.Cite this work:Fitch, Katie and Christine Kemker. Algae, Phytoplankton and Chlorophyll. Fundamentals of Environmental Measurements. Fondriest Environmental,45454444404140414141324747474215495049,50Algae, Phytoplankton and Chlorophyll - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/algae-phytoplankton-chlorophyll/ 13 / 80 Most Popular MeterGet Discount Code Water Quality Conductivity, Salinity & Total Dissolved Solids Inc. 22 Oct. 2014. Web. < http://www.fondriest.com/environmental-measurements/parameters/water-quality/algae-phytoplankton-and-chlorophyll>. Additional Resources:Measurement MethodsChlorophyll SensorsApplicationsReferences1 COMMENTStudy: Algal Blooms Optimize Conditions To Support Growth - Lake Scientist[] lakes may not be as simple as cutting phosphorus loads from runoff, according to WYSO public radio. Algae, the researchers found,appear to be able to make use of nutrient deposits buried in sediments long []JANUARY 22, 2015 AT 3:18 PMParameters ParametersHydrology HydrologyWater Quality Water QualityAlgae, Phytoplankton and Chlorophyll Algae, Phytoplankton and ChlorophyllConductivity, Salinity & Total Dissolved Solids Conductivity, Salinity & Total Dissolved SolidsDissolved Oxygen Dissolved OxygenpH of Water pH of WaterPhotosynthetically Active Radiation and Solar Radiation Photosynthetically Active Radiation and Solar RadiationTurbidity, Total Suspended Solids & Water Clarity Turbidity, Total Suspended Solids & Water ClarityWater Temperature Water TemperatureWeather and Atmosphere Weather and AtmosphereMethods and Equipment Methods and EquipmentMonitoring Applications Monitoring ApplicationsReferences References2015 FONDRIEST ENVIRONMENTAL INC. | QUESTIONS? CALL 888.426.2151 OR EMAIL 2015 FONDRIEST ENVIRONMENTAL INC. | QUESTIONS? 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CALL 888.426.2151 OR EMAIL CUSTOMERCARE@FONDRIEST.COMCUSTOMERCARE@FONDRIEST.COMCUSTOMERCARE@FONDRIEST.COMAlgae, Phytoplankton and Chlorophyll - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/algae-phytoplankton-chlorophyll/ 14 / 80 Conductivity, Salinity & Total Dissolved Solids pH of Water SHARE20 20 70 70 15 15Section OverviewWhat is Dissolved OxygenDissolved Oxygen and Aquatic LifeWhere Does Dissolved Oxygen Come From Dissolved Oxygen From PhotosynthesisDissolved Oxygen Saturation What Affects Oxygen Solubility How Water Can be More Than 100% SaturatedTypical Dissolved Oxygen Levels Freshwater Organisms and DO Requirements Saltwater Organisms and DO RequirementsConsequences of Unusual Dissolved Oxygen Levels Fish Kills Gas Bubble Disease Dead ZonesDissolved Oxygen and Water Column Stratification Lake Stratification Oceanic StratificationDissolved OxygenTo search type and hit enterDissolved Oxygen - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/dissolved-oxygen/ 15 / 80Dissolved oxygen is important to manyforms of aquatic life. Estuary StratificationDissolved Oxygen Units of MeasurementCalculating DO from % Air SaturationDissolved Oxygen Measurement MethodsDissolved Oxygen Sensor TechnologiesApplications What is Dissolved Oxygen?Dissolved oxygen refers to the level of free, non-compound oxygen present in water or other liquids. It is an important parameter in assessing waterquality because of its influence on the organisms living within a body of water. In limnology (the study of lakes), dissolved oxygen is an essentialfactor second only to water itself .A dissolved oxygen level that is too high or too low can harm aquatic life and affect water quality.Non-compound oxygen, or free oxygen (O2), is oxygen that is not bonded to any other element. Dissolved oxygen is the presence of these freeO2 molecules within water.The bonded oxygen molecule in water (H2O) is in a compound and does not count toward dissolved oxygen levels. Onecan imagine that free oxygen molecules dissolve in water much the way salt or sugar does when it is stirred .Non-bonded oxygen molecules in water Dissolved Oxygen and Aquatic LifeDissolved oxygen is necessary to many forms of life including fish, invertebrates, bacteria and plants. Theseorganisms use oxygen in respiration, similar to organisms on land. Fish and crustaceans obtain oxygen forrespiration through their gills, while plant life and phytoplankton require dissolved oxygen for respirationwhen there is no light for photosynthesis. The amount of dissolved oxygen needed varies from creatureto creature. Bottom feeders, crabs, oysters and worms need minimal amounts of oxygen (1-6 mg/L), whileshallow water fish need higher levels (4-15 mg/L) .Microbes such as bacteria and fungi also require dissolved oxygen. These organisms use DO to decomposeorganic material at the bottom of a body of water. Microbial decomposition is an important contributor tonutrient recycling. However, if there is an excess of decaying organic material (from dying algae and otherorganisms), in a body of water with infrequent or no turnover (also known as stratification), the oxygen atlower water levels will get used up quicker. Where Does DO Come From?Dissolved oxygen enters water through theair or as a plant byproduct. From the air,oxygen can slowly diffuse across thewaters surface from the surroundingatmosphere, or be mixed in quickly throughaeration, whether natural or man-made.The aeration of water can be caused bywind (creating waves), rapids, waterfalls,ground water discharge or other forms of47Dissolved Oxygen - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/dissolved-oxygen/ 16 / 80How dissolved oxygen enters waterDissolved oxygen can enter the water as a byproduct ofphotosynthesis.Not all water depths reach 100% air saturationrunning water. Man-made causes ofaeration vary from an aquarium air pumpto a hand-turned waterwheel to a largedam.Dissolved oxygen is also produced as awaste product of photosynthesis fromphytoplankton, algae, seaweed and otheraquatic plants. Dissolved Oxygen from PhotosynthesisWhile most photosynthesis takes place at the surface (by shallow water plants andalgae), a large portion of the process takes place underwater (by seaweed, sub-surface algae and phytoplankton). Light can penetrate water, though the depththat it can reach varies due to dissolved solids and other light-scattering elementspresent in the water.Depth also affects the wavelengths available to plants, withred being absorbed quickly and blue light being visible past 100 m. In clear water,there is no longer enough light for photosynthesis to occur beyond 200 m, andaquatic plants no longer grow. In turbid water, this photic (light-penetrating) zone isoften much shallower.Regardless of wavelengths available, the cycle doesnt change. In addition to theneeded light, CO2 is readily absorbed by water (its about 200 times more solublethan oxygen) and the oxygen produced as a byproduct remains dissolved inwater . The basic reaction of aquatic photosynthesis remains:CO2 + H2O (CH2O) + O2As aquatic photosynthesis is light-dependent, the dissolved oxygen produced willpeak during daylight hours and decline at night. Dissolved Oxygen SaturationIn a stable body of water with no stratification, dissolved oxygen will remain at100% air saturation. 100% air saturation means that the water is holding as manydissolved gas molecules as it can in equilibrium. At equilibrium, the percentage ofeach gas in the water would be equivalent to the percentage of that gas in theatmosphere i.e. its partial pressure . The water will slowly absorb oxygen andother gasses from the atmosphere until it reaches equilibrium at complete saturation. This process is sped up by wind-driven waves and other sources of aeration .In deeper waters, DO can remain below 100% due to the respiration of aquaticorganisms and microbial decomposition. These deeper levels of water often do notreach 100% air saturation equilibrium because they are not shallow enough to beaffected by the waves and photosynthesis at the surface . This water is below aninvisible boundary called the thermocline (the depth at which water temperaturebegins to decline). What Affects Oxygen Solubility?810Dissolved Oxygen - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/dissolved-oxygen/ 17 / 80Dissolved oxygen concentrations decrease as temperatureincreasesDissolved oxygen concentrations decrease as altitude increases(pressure decreases)Henrys law determining the dissolved oxygen concentration at 20degrees C and 100% air saturation (1 kg water = 1 L water)Two bodies of water that are both 100% air-saturated do not necessarily have thesame concentration of dissolved oxygen. The actual amount of dissolved oxygen(in mg/L) will vary depending on temperature, pressure and salinity .First, the solubility of oxygen decreases as temperature increases . This means thatwarmer surface water requires less dissolved oxygen to reach 100% air saturationthan does deeper, cooler water. For example, at sea level (1 atm or 760 mmHg) and4C (39F), 100% air-saturated water would hold 10.92 mg/L of dissolved oxygen. But if the temperature were raised to room temperature, 21C (70F), therewould only be 8.68 mg/L DO at 100% air saturation .Second dissolved oxygen decreases exponentially as salt levels increase . That iswhy, at the same pressure and temperature, saltwater holds about 20% lessdissolved oxygen than freshwater .Third, dissolvedoxygen will increaseas pressureincreases . This is true of both atmospheric and hydrostatic pressures. Water atlower altitudes can hold more dissolved oxygen than water at higher altitudes. Thisrelationship also explains the potential for supersaturation of waters below thethermocline at greater hydrostatic pressures, water can hold more dissolvedoxygen without it escaping . Gas saturation decreases by 10% per meter increasein depth due to hydrostatic pressure . This means that if the concentration ofdissolved oxygen is at 100% air saturation at the surface, it would only be at 70%air saturation three meters below the surface.In summary, colder, deeper fresh waters have the capability to hold higherconcentrations of dissolved oxygen, but due to microbial decomposition, lack ofatmospheric contact for diffusion and the absence of photosynthesis, actual DOlevels are often far below 100% saturation . Warm, shallow saltwater reaches100% air saturation at a lower concentration, but can often achieve levels over100% due to photosynthesis and aeration. Shallow waters also remain closer to 100% saturation due to atmospheric contact and constant diffusion .If there is a significant occurrence of photosynthesis or a rapid temperature change, the water can achieve DO levels over 100% air saturation. Atthese levels, the dissolved oxygen will dissipate into the surrounding water and air until it levels out at 100% . How Can Water be More than 100% Saturated?100% air saturation is the equilibrium point for gases in water. This is because gasmolecules diffuse between the atmosphere and the waters surface. According toHenrys Law, the dissolved oxygen content of water is proportional to the percentof oxygen (partial pressure) in the air above it. As oxygen in the atmosphere isabout 20.3%, the partial pressure of oxygen at sea level (1 atm) is 0.203 atm. Thusthe amount of dissolved oxygen at 100% saturation at sea level at 20 C is 9.03mg/L .The equation shows that water will remain at 100% air saturation at equilibrium.However, there are several factors that can affect this. Aquatic respiration anddecomposition lower DO concentrations, while rapid aeration and photosynthesiscan contribute to supersaturation. During the process of photosynthesis, oxygen isproduced as a waste product. This adds to the dissolved oxygen concentration inthe water, potentially bringing it above 100% saturation . In addition, theequalization of water is a slow process (except in highly agitated or aeratedsituations). This means that dissolved oxygen levels can easily be more than 100%air saturation during the day in photosynthetically active bodies of water .13Dissolved Oxygen - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/dissolved-oxygen/ 18 / 80Supersaturation of water can be caused by rapidaeration from a dam.Dissolved oxygen concentrations can fluctuate daily and seasonally.Dissolved oxygen often reaches over 100% air saturation due tophotosynthesis activity during the day.Supersaturation caused by rapid aeration is often seen beside hydro-power dams and largewaterfalls . Unlike small rapids and waves, the water flowing over a dam or waterfall trapsand carries air with it, which is then plunged into the water. At greater depths and thus greaterhydrostatic pressures, this entrained air is forced into solution, potentially raising saturationlevels over 100% .Rapid temperature changes can also create DO readings greater than 100% . As watertemperature rises, oxygen solubility decreases. On a cool summer night, a lakes temperaturemight be 60 F. At 100% air saturation, this lakes dissolved oxygen levels would be at 9.66mg/L. When the sun rises and warms up the lake to 70 F, 100% air saturation should equateto 8.68 mg/L DO . But if there is no wind to move the equilibration along, the lake will stillcontain that initial 9.66 mg/L DO, an air saturation of 111%. Typical Dissolved Oxygen LevelsDissolved oxygen concentrations are constantly affected bydiffusion and aeration, photosynthesis, respiration anddecomposition. While water equilibrates toward 100% airsaturation, dissolved oxygen levels will also fluctuate withtemperature, salinity and pressure changes . As such, dissolvedoxygen levels can range from less than 1 mg/L to more than 20mg/L depending on how all of these factors interact. Infreshwater systems such as lakes, rivers and streams, dissolvedoxygen concentrations will vary by season, location and waterdepth.Freshwater Fluctuations: Example 1In the Pompton River in New Jersey, mean dissolved oxygenconcentrations range from 12-13 mg/L in winter and drop to 6-9 mg/L in the summer. That same river shows daily fluctuationsof up to 3 mg/Ldue to photosynthesis production.Dissolved oxygen levels often stratify in the winter and summer, turning over in the spring and fall as lake temperatures align.Freshwater Fluctuations: Example 2Studies at Crooked Lake in Indiana show dissolved oxygen concentrations vary by season and depth from 12 mg/L (surface, winter) to 0 mg/L (32m depth, late summer), with full lake turnovers in spring and fall equalizing DO levels around 11 mg/L for all depths .Dissolved Oxygen - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/dissolved-oxygen/ 19 / 80In rivers and streams, dissolved oxygen concentrations aredependent on temperature.Rivers and streams tend to stay near or slightly above 100% air saturation due torelatively large surface areas, aeration from rapids, and groundwater discharge,which means that their dissolved oxygen concentrations will depend on the watertemperature . While groundwater usually has low DO levels, groundwater-fedstreams can hold more oxygen due to the influx of colder water and the mixing itcauses . Standard Methods for the Examination of Water and Wastewater definesdissolved oxygen in streams as the sum of photosynthetic byproducts, respiration,re-aeration, accrual from groundwater inflow and surface runoff .Saltwater holds less oxygen than freshwater, so oceanic DO concentrations tend tobe lower than those of freshwater. In the ocean, surface water mean annual DOconcentrations range from 9 mg/L near the poles down to 4 mg/L near the equatorwith lower DO levels at further depths. There are lower dissolved oxygenconcentrations near the equator because salinity is higher .Dissolved oxygen levels at the oceans surface: (data: World Ocean Atlas 2009; photo credit: Plumbago; Wikipedia Commons)Some states have Water Quality Standard Acts, requiring minimum concentrations of dissolved oxygen; in Michigan, these minimums are 7 mg/L forcold-water fisheries and 5 mg/L for warm-water fish; in Colorado, Class 1 Cold Water Aquatic Life needs 6 mg/L, and Class 1 Warm WaterAquatic Life requires DO levels of at least 5 mg/L. In order to mimic ideal environmental systems, freshwater tanks ideally need around 8 mg/L DOfor optimum growth and marine tank requirements range from 6-7 mg/L DO based on the salinity level . In other words, dissolved oxygen shouldbe near 100% air saturation. Examples of Freshwater Organisms and Dissolved Oxygen RequirementsColdwater fish like trout and salmon are most affected by low dissolved oxygen levels. The mean DOlevel for adult salmonids is 6.5 mg/L, and the minimum is 4 mg/L . These fish generally attempt toavoid areas where dissolved oxygen is less than 5 mg/L and will begin to die if exposed to DO levels lessthan 3 mg/L for more than a couple days . For salmon and trout eggs, dissolved oxygen levels below11 mg/L will delay their hatching, and below 8 mg/L will impair their growth and lower their survivalrates. When dissolved oxygen falls below 6 mg/L (considered normal for most other fish), the vastmajority of trout and salmon eggs will die. Bluegill, Largemouth Bass, White Perch, and Yellow Perch are considered warmwater fish and depend ondissolved oxygenlevels above 5 mg/L . They will avoid areas where DO levels are below 3 mg/L, butgenerally do not begin to suffer fatalities due to oxygen depletion until levels fall below 2 mg/L. The1715192122Dissolved Oxygen - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/dissolved-oxygen/ 20 / 80Minimum dissolved oxygen requirements offreshwater fishMinimum dissolved oxygen requirements ofsaltwater fishmean DO levels should remain near 5.5 mg/L for optimum growth and survival .Walleye also prefer levels over 5 mg/L, though they can survive at 2 mg/L DO levels for a short time.Muskie need levels over 3 mg/L for both adults and eggs . Carp are hardier, and while they can enjoydissolved oxygen levels above 5 mg/L, they easily tolerate levels below 2 mg/L and can survive at levelsbelow 1 mg/L .The freshwater fish most tolerant to DO levels include fathead minnows and northern pike. Northernpike can survive at dissolved oxygen concentrations as low as 0.1 mg/L for several days, and at 1.5mg/L for an infinite amount of time . Fathead minnows can survive at 1 mg/L for an extended periodwith only minimal effects on reproduction and growth.As for bottom-dwelling microbes, DO changes dont bother them much. If all the oxygen at their waterlevel gets used up, bacteria will start using nitrate to decompose organic matter, a process known asdenitrification. If all of the nitrogen is spent, they will begin reducing sulfate . If organic matteraccumulates faster than it decomposes, sediment at the bottom of a lake simply becomes enriched bythe organic material. . Examples of Saltwater Organisms and Dissolved Oxygen RequirementsSaltwater fish and organisms have a higher tolerance for low dissolved oxygen concentrations assaltwater has a lower 100% air saturation than freshwater. In general, dissolved oxygen levels are about20% less in seawater than in freshwater .This does not mean that saltwater fish can live without dissolved oxygen completely. Striped bass, whiteperch and American shad need DO levels over 5 mg/L to grow and thrive. The red hake is alsoextremely sensitive to dissolved oxygen levels, abandoning its preferred habitat near the seafloor ifconcentrations fall below 4.2 mg/L .The dissolved oxygen requirements of open-ocean and deep-ocean fish are a bit harder to track, butthere have been some studies in the area. Billfish swim in areas with a minimum of 3.5 mg/L DO, whilemarlins and sailfish will dive to depths with DO concentrations of 1.5 mg/L . Likewise, white sharks arealso limited in dive depths due to dissolved oxygen levels (above 1.5 mg/L), though many other sharkshave been found in areas of low DO . Tracked swordfish show a preference for shallow water duringthe day, basking in oxygenated water (7.7 mg/L) after diving to depths with concentrations around 2.5mg/L . Albacore tuna live in mid-ocean levels, and require a minimum of 2.5 mg/L , while halibut canmaintain a minimum DO tolerance threshold of 1 mg/L .Many tropical saltwater fish, including clown fish, angel fish and groupers require higher levels of DO,such as those surrounding coral reefs. Coral reefs are found in the euphotic zone (where lightpenetrates the water usually not deeper than 70 m). Higher dissolved oxygen concentrations aregenerally found around coral reefs due to photosynthesis and aeration from eddies and breaking waves . These DO levels can fluctuate from 4-15 mg/L, though they usually remain around5-8 mg/L,cycling between day photosynthesis production and night plant respiration . In terms of air saturation,this means that dissolved oxygen near coral reefs can easily range from 40-200% .Crustaceans such as crabs and lobsters are benthic (bottom-dwelling) organisms, but still requireminimum levels of dissolved oxygen. Depending on the species, minimum DO requirements can range from 4 mg/L to 1 mg/L . Despite beingbottom dwellers, mussels, oysters and clams also require a minimum of 1-2 mg/L of dissolved oxygen, which is why they are found in shallower,coastal waters that receive oxygen from the atmosphere and photosynthetic sources. Consequences of Unusual DO LevelsIf dissolved oxygen concentrations drop below a certain level, fish mortality rates will rise. Sensitive freshwater fish like salmon cant even reproduceat levels below 6 mg/L . In the ocean, coastal fish begin to avoid areas where DO is below 3.7 mg/L, with specific species abandoning an areacompletely when levels fall below 3.5 mg/L . Below 2.0 mg/L, invertebrates also leave and below 1 mg/L even benthic organisms show reducedgrowth and survival rates . Fish kill / WinterkillA fishkill occurs when a large number of fish in an area of water die off. It can be species-based or a water-wide mortality. Fish kills can occur for anumber of reasons, but low dissolved oxygen is often a factor. A winterkill is a fish kill caused by prolonged reduction in dissolved oxygen due to iceor snow cover on a lake or pond .29Dissolved Oxygen - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/dissolved-oxygen/ 21 / 80Dissolved oxygen depletion is the most commoncause of fish killsSockeye salmon with gas bubblediseaseWhen a body of water is overproductive, the oxygen in the water may get used up faster thanit can be replenished.This occurs when a body of water is overstocked with organisms or ifthere is a large algal bloom die-off.Fish kills are more common in eutrophic lakes: lakes with high concentrations of nutrients(particularly phosphorus and nitrogen). High levels of nutrients fuel algae blooms, which caninitially boost dissolved oxygen levels. But more algae means more plant respiration, drawing onDO, and when the algae die, bacterial decomposition spikes, using up most or all of the dissolvedoxygen available. This creates an anoxic, or oxygen-depleted, environment where fish andother organisms cannot survive. Such nutrient levels can occur naturally, but are more oftencaused by pollution from fertilizer runoff or poorly treated wastewater.Winterkills occur when respiration from fish, plants and other organisms is greater than theoxygen production by photosynthesis . They occur when the water is covered by ice, and socannot receive oxygen by diffusion from the atmosphere. If the ice is then covered by snow,photosynthesis also cannot occur, and the algae will depend entirely on respiration or die off. Inthese situations, fish, plants and decomposition are all using up the dissolved oxygen, and itcannot be replenished, resulting in a winter fish kill. The shallower the water, and the more productive (high levels of organisms) the water, thegreater the likelihood of a winterkill . Gas Bubble DiseaseJust as low dissolved oxygen can cause problems, so too can high concentrations. Supersaturated water cancause gas bubble disease in fish and invertebrates . Significant death rates occur when dissolved oxygenremains above 115%-120% air saturation for a period of time. Total mortality occurs in young salmon and troutin under three days at 120% dissolved oxygen saturation . Invertebrates, while also affected by gas bubbledisease, can usually tolerate higher levels of supersaturation than fish .Extended periods of supersaturation can occur in highly aerated waters, often near hydropower dams andwaterfalls, or due to excessive photosynthetic activity. Algae blooms can cause air saturations of over 100% dueto large amounts of oxygen as a photosynthetic byproduct. This is often coupled with higher watertemperatures, which also affects saturation. At higher temperatures, water becomes 100% saturated at lowerconcentrations, so higher dissolved oxygen concentrations mean even higher air saturation levels. Dead ZonesA dead zone is an area of water with little to no dissolved oxygen present. They are so named because aquatic organisms cannot survive there.Dead zones often occur near heavy human populations, such as estuaries and coastal areas off the Gulf of Mexico, the North Sea, the Baltic Sea,and the East China Sea. They can occur in large lakes and rivers as well, but are more well known in the oceanic context.Hypoxic and anoxic zones around the world (photo credit: NASA)Dissolved Oxygen - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/dissolved-oxygen/ 22 / 80Lake stratificationThese zones are usually a result of a fertilizer-fueled algae and phytoplankton growth boom. When the algae and phytoplankton die, the microbes atthe seafloor use up the oxygen decomposing the organic matter . These anoxic conditions are usually stratified, occurring only in the lower layersof the water. While some fish and other organisms can escape, shellfish, young fish and eggs usually die .Naturally occurring hypoxic (low oxygen) conditions are not considered dead zones. The local aquatic life (including benthic organisms) haveadjusted to the recurring low-oxygen conditions, so the adverse effects of a dead zone (mass fish kills, sudden disappearance of aquatic organisms,and growth/development problems in fish and invertebrates) do not occur .Such naturally occurring zones frequently occur in deep lake basins and lower ocean levels due to water column stratification. Dissolved Oxygen and Water Column StratificationStratification separates a body of water into layers. This layering can be based on temperature or dissolved substances (namely salt and oxygen)with both factors often playing a role. The stratification of water has been commonly studied in lakes, though it also occurs in the ocean. It can alsooccur in rivers if pools are deep enough and in estuaries where there is a significant division between freshwater and saltwater sources. Lake StratificationThe uppermost layer of a lake, known as the epilimnion, is exposed to solar radiation and contact withthe atmosphere, keeping it warmer. The depth of the epilimnion is dependent on the temperatureexchange, usually determined by water clarity and depth of mixing (usually initiated by wind) . Withinthis upper layer, algae and phytoplankton engage in photosynthesis. Between the contact with the air,potential for aeration and the byproducts of photosynthesis, dissolved oxygen in the epilimnion remainsnear 100% saturation. The exact levels of DO vary depending on the temperature of the water, theamount of photosynthesis occurring and the quantity of dissolved oxygen used for respiration byaquatic life.Below the epilimnion is the metalimnion, a transitional layer that fluctuates in thickness and temperature.The boundary between the epilimnion and metalimnion is called the thermocline the point at whichwater temperature begins to steadily drop off . Here, two different outcomes can occur. If light canpenetrate beyond the thermocline and photosynthesis occurs in this strata, the metalimnion canachieve an oxygen maximum . This means that the dissolved oxygen level will be higher in themetalimnion than in the epilimnion. But in eutrophic or nutrient-rich lakes, the respiration of organismscan deplete dissolved oxygen levels, creating a metalimnetic oxygen minimum.The next layer is the hypolimnion. If the hypolimnion is deep enough to never mix with the upperlayers, it is known as the monimolimnion. The hypolimnion is separated from the upper layers by thechemocline or halocline. These clines mark the boundary between oxic and anoxic water and salinitygradients, respectively. .While lab conditions would conclude that at colder temperatures and higherpressures water can hold more dissolved oxygen, this is not always the result. In the hypolimnion,bacteria and fungi use dissolved oxygen to decompose organic material. This organic material comesfrom dead algae and other organisms that sink to the bottom. The dissolved oxygen used indecomposition is not replaced there is no atmospheric contact, aeration or photosynthesis to restoreDO levels in the hypolimnion . Thus the process of decomposition uses up all of the oxygen within this layer.If the lake in question is a holomictic mixing lake, all the layers mix at least once per year (usually spring and fall) when lake strata temperaturesalign. This turnover redistributes dissolved oxygen throughout all the layers and the process begins again. Ocean StratificationDissolved Oxygen - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/dissolved-oxygen/ 23 / 80Stratification in the oceanDissolved oxygen levels decrease at thethermoclineDissolved oxygen levels are bordered byhaloclinesDissolved oxygen levels change with thepycnclinesDissolved oxygen stratification in an estuary is dependent on salinity (expressed in PSU).Stratification in the ocean is both horizontal and vertical. The littoral, or coastal areais most affected by estuaries and other inflow sources.It tends to be shallow andtidal with fluctuating dissolved oxygen levels. The sublittoral, also known as theneritic or demersal zone, is considered a coastal zone as well. In this zone, dissolvedoxygen concentrations may vary but they do not fluctuate as much as they do inthe littoral zone.This is the zone where many coral reefs grow, and DO levels remain near 100% airsaturation due to eddies, breaking waves and photosynthesis. This zone is alsowhere most oceanic benthic (bottom-dwelling) organisms exist. Oceanic benthic fishdo not live at the greatest depths of the ocean. They dwell at the seafloor near tocoasts and oceanic shelves while remaining in the upper levels of the ocean.Beyond the demersal zone are the bathyal, abyssal and hadal plains, which are fairlysimilar in terms of consistently low DO.In the open ocean, there are five major vertical strata: epipelagic, mesopelagic,bathypelagic, abyssopelagic, and hadalpelagic. The exact definitions and depthsare subjective, but the following information is generally agreed upon. The epipelagicis also known as the surface layer or photic zone (where light penetrates). This is thelayer with the highest levels of dissolved oxygen due to wave action andphotosynthesis. The epipelagic generally reaches to 200 m and is bordered by acollection of clines.These clines can overlap or exist at separatedepths. Much like in a lake, the thermoclinedivides oceanic strata by temperature. The halocline divides by salinity levels and the pycnocline dividesstrata by density . Each of these clines can affect the amount of dissolved oxygen the ocean strata canhold.The mesopelagic, meaning twilight zone, stretches from 200-1000 m. Depending on water clarity, some light may filter through,but there is not enough for photosynthesis to occur. Within thisstrata, the oxygen minimum zone (OMZ) can occur. The OMZdevelops because organisms use the oxygen for respiration, but itis too deep to be replenished by photosynthetic oxygenbyproducts or aeration from waves. This zone tends to existaround a depth of 500 m. The mesopelagic zone is bordered bychemoclines (clines based on chemistry levels, e.g. oxygen and salinity) on both sides, reflecting differentdissolved oxygen and salinity levels between the strata.Below the mesopelagic is the aphotic zone(s). These strata havelower dissolved oxygen levels than the surface water becausephotosynthesis does not occur but can have higher levels than theOMZ because less respiration occurs.The bathypelagic, midnight zone exists between 1000-4000 m, and many creatures can still live here. Thebottom layer of the ocean is the abyssopelagic, which exists below 4000 m. The hadopelagic is the name forthe zone of deep ocean trenches that open below the abyssal plain, such as the Mariana Trench. Estuary StratificationEstuary stratificationsare based on salinitydistributions. Because saltwater holds less dissolved oxygen thanfreshwater, this can affect aquatic organism distribution. Thestronger the river flow, the higher the oxygen concentrations.This stratification can be horizontal, with DO levels dropping frominland to open ocean, or vertical, with the fresh, oxygenatedriver water floating over the low DO seawater. When thestratification is clearly defined, a pycnocline divides the fresherwater from the salt water, contributing to separate dissolvedoxygen concentrations in each strata. 45Dissolved Oxygen - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/dissolved-oxygen/ 24 / 80Dissolved oxygen unit conversions at 21 Celsius (70 F) and 1atmosphere (760 mmHg)Dissolved Oxygen Units and ReportingDissolved oxygen is usually reported in milligrams per liter (mg/L) or as a percent ofair saturation. However, some studies will report DO in parts per million (ppm) or inmicromoles (umol). 1 mg/L is equal to 1 ppm. The relationship between mg/L and %air saturation has been discussed above, and varies with temperature, pressure andsalinity of the water. One micromole of oxygen is equal to 0.022391 milligrams, andthis unit is commonly used in oceanic studies. Thus 100 umol/L O2 is equal to 2.2mg/L O2. Calculating DO from % Air SaturationTo calculate dissolved oxygen concentrations from air saturation, it is necessary toknow the temperature and salinity of the sample. Barometric pressure has alreadybeen accounted for as the partial pressure of oxygen contributes to the percent airsaturation. Salinity and temperature can then be used in Henrys Law to calculatewhat the DO concentration would be at 100% air saturation. However, it is easierto use an oxygen solubility chart. These charts show the dissolved oxygen concentration at 100% air saturation at varying temperatures, andsalinities. This value can then be multiplied by the measured percent air saturation to calculate the dissolved oxygen concentration O2 mg/L = (Measured % DO)*(DO value from chart at temperature and salinity)Example:70% DO measured35 ppt salinity15C.70 * 8.135 = 5.69 mg/L DO7107.Dissolved Oxygen - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/dissolved-oxygen/ 25 / 80 Conductivity, Salinity & Total Dissolved Solids pH of Water Cite this work:Kemker, Christine. Dissolved Oxygen. Fundamentals of Environmental Measurements. Fondriest Environmental, Inc. 19 Nov. 2013. Web. .Additional Resources:Measurement MethodsDissolved Oxygen SensorsDissolved Oxygen MetersApplicationsReferences1 COMMENTDissolved Oxygen - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/dissolved-oxygen/ 26 / 80 Most Popular DO MeterGet Discount CodeThe science behind Eutrophication (Allow me to digress) | Commercial Farming[] 2. http://www.fondriest.com/environmental-measurements/parameters/water-quality/dissolved-oxygen/ []MARCH 2, 2015 AT 3:45 PMParameters ParametersHydrology HydrologyWater Quality Water QualityAlgae, Phytoplankton and Chlorophyll Algae, Phytoplankton and ChlorophyllConductivity, Salinity & Total Dissolved Solids Conductivity, Salinity & Total Dissolved SolidsDissolved Oxygen Dissolved OxygenpH of Water pH of WaterPhotosynthetically Active Radiation and Solar Radiation Photosynthetically Active Radiation and Solar RadiationTurbidity, Total Suspended Solids & Water Clarity Turbidity, Total Suspended Solids & Water ClarityWater Temperature Water TemperatureWeather and Atmosphere Weather and AtmosphereMethods and Equipment Methods and EquipmentMonitoring Applications Monitoring ApplicationsReferences References2015 FONDRIEST ENVIRONMENTAL INC. | QUESTIONS? CALL 888.426.2151 OR EMAIL 2015 FONDRIEST ENVIRONMENTAL INC. | QUESTIONS? CALL 888.426.2151 OR EMAIL 2015 FONDRIEST ENVIRONMENTAL INC. | QUESTIONS? CALL 888.426.2151 OR EMAIL CUSTOMERCARE@FONDRIEST.COMCUSTOMERCARE@FONDRIEST.COMCUSTOMERCARE@FONDRIEST.COMDissolved Oxygen - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/dissolved-oxygen/ 27 / 80 Dissolved Oxygen Photosynthetically Active Radiation and Solar Radiation SHARE17 17 45 45 67 67Chapter OverviewWhat is pHAcids and Bases Acidic, Basic or AlkalineAlkalinity and the pH of WaterpH Units of MeasurementWhy is pH ImportantFactors that Influence the pH of Water Carbon Dioxide and pH Natural pH Influences Manmade pH InfluencesTypical pH LevelsUnusual Levels and Consequences Alkaline and Acid Lakes Ocean AcidificationpH Measurement MethodspH SensorsApplicationspH of WaterTo search type and hit enterpH of Water - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/ph/ 28 / 80Acid-base pairs can neutralize each other likeH+ and OH- do in this equation. What is pH?pH is a determined value based on a defined scale, similar to temperature. This means that pH of water is not a physical parameter that can bemeasured as a concentration or in a quantity. Instead, it is a figure between 0 and 14 defining how acidic or basic a body of water is along alogarithmic scale . The lower the number, the more acidic the water is. The higher the number, the more basic it is. A pH of 7 is considered neutral.The logarithmic scale means that each number below 7 is 10 times more acidic than the previous number when counting down. Likewise, whencounting up above 7, each number is 10 times more basic than the previous number .The logarithmic scale of pH means that as pH increases, the H+ concentration will decrease by a power of 10. Thus at a pH of 0, H+has a concentration of 1 M. At a pH of 7, this decreases to 0.0000001 M. At a pH of 14, there is only 0.00000000000001 M H+.pH stands for the power of hydrogen . The numerical value of pH is determined by the molar concentration of hydrogen ions (H+) . This is doneby taking the negative logarithm of the H+ concentration (-log(H+)). For example, if a solution has a H+ concentration of 10M, the pH of thesolution will be -log(10 ), which equals 3.This determination is due to the effect of hydrogen ions (H+) and hydroxyl ions (OH-) on pH. The higher the H+ concentration, the lower the pH,and the higher the OH- concentration, the higher the pH. At a neutral pH of 7 (pure water), the concentration of both H+ ions and OH- ions is 10M. Thus the ions H+ and OH- are always paired as the concentration of one increases, the other will decrease; regardless of pH, the sum of theions will always equal 10 M . Due to this influence, H+ and OH- are related to the basic definitions of acids and bases. Acids and BasesAs an operational definition, an acid is a substance that will decrease pH when added to pure water. Inthe same manner, a base is a substance that will increase the pH of water. To further define thesesubstances, Arrhenius determined in 1884 that an acid will release a hydrogen ion (H+) as it dissolves inwater, and a base will release a hydroxyl ion (OH-) in water. However, there are some substances thatfit the operational definition (altering pH), without fitting the Arrhenius definition (releasing an ion). Toaccount for this, Bronsted and Lowry redefined acids and bases; an acid releases a hydrogen ion orproton (equivalent to H+) and a base accepts a hydrogen ion or proton. This means that acids andbases can cancel each other out, as shown in the water equation to the right. Basic or AlkalineThe terms alkalineand basic meanapproximately thesame thing. By theBronsted-Lowrydefinition, basicdescribes anysubstance thatreduces the-3-3pH of Water - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/ph/ 29 / 80Common examples of alkalis include milk of magnesia Mg(OH)2, caustic potash KOH,slaked lime/limewater Ca(OH)2, and caustic soda (lye) NaOH.Alkalinity and pH are directly related at 100% air saturation.pH values are determined on a logarithmicscale.hydrogen ionconcentration andincreases the pH ofwater, or in otherwords, a base.Alkaline comes fromalkali, which refersto ionic compounds(salts) containing alkali metal or alkaline earth metal elements that form hydroxide ions when dissolved in water. Alkali salts are very common anddissolve easily. Due to the hydroxide ions they produce (which increase pH), all alkalis are bases. Some sources define any soluble base as an alkali.As such, soluble bases can be described as basic or alkaline. However, insoluble bases (such as copper oxide) should only be described as basic,not alkaline. Alkalinity and the pH of WaterAlkalinity does not refer to alkalis as alkaline does. While alkalinity and pH are closelyrelated, there are distinct differences. The alkalinity of water or a solution is thequantitative capacity of that solution to buffer or neutralize an acid. In other words,alkalinity is a measurement of waters ability to resist changes in pH. This term is usedinterchangeably with acid-neutralizing capacity (ANC). If a body of water has a highalkalinity, it can limit pH changes due to acid rain, pollution or other factors. Thealkalinity of a stream or other body of water is increased by carbonate-rich soils(carbonates and bicarbonates) such as limestone, and decreased by sewage outflowand aerobic respiration. Due to the presence of carbonates, alkalinity is more closelyrelated to hardness than to pH (though there are still distinct differences). However,changes in pH can also affect alkalinity levels (as pH lowers, the buffering capacity ofwater lowers as well). pH and alkalinity are directly related when water is at 100%air saturation.The alkalinity of water also plays an important role in daily pH levels. The process ofphotosynthesis by algae and plants uses hydrogen, thus increasing pH levels .Likewise, respiration and decomposition can lower pH levels. Most bodies of waterare able to buffer these changes due to their alkalinity, so small or localized fluctuations are quickly modified and may be difficult to detect . pH and Alkalinity UnitspH values are reported as a number between 0 and 14 as a standard pH unit. This unit is equivalent tothe negative logarithm of the hydrogen ion molar concentration (-log(H+)) in the solution. Dependingon the accuracy of the measurement, the pH value can be carried out to one or two decimal places.However, because the pH scale is logarithmic, attempting to average two pH values would bemathematically incorrect. If an average value is required, it can be reported as a median or a range, notas a simple calculation .Alkalinity can be reported as mg/L or microequivalents per liter (meq/L). When in mg/L, it refers tocarbonate (CO3 ), bicarbonate (HCO3 ) or calcium carbonate (CaCO3) concentrations, though calciumcarbonate is most common .1 mg/L alkalinity as CaCO3 = 0.01998 meg/L alkalinity1 mg/L alkalinity as CaCO3 = 0.5995 mg/L alkalinity as CO31 mg/L alkalinity as CaCO3 = 1.2192 mg/L alkalinity as HCO3 Why is pH Important?If the pH of water is too high or too low, the aquatic organismsliving within it will die. pH can also affect the solubility and toxicityof chemicals and heavy metals in the water . The majority of2- 2-pH of Water - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/ph/ 30 / 80Aquatic pH levels. The optimum pH levels for fish are from 6.5 to 9.0. Outside ofoptimum ranges, organisms can become stressed or die.An minor increase in pH levels can cause a oligotrophic (rich indissolved oxygen) lake to become eutrophic (lacking dissolvedoxygen).pH levels can fluctuate daily due to photosynthesis and respirationin the water. The degree of change depends on the alkalinity ofthe water.aquatic creatures prefer a pH range of 6.5-9.0, though somecan live in water with pH levels outside of this range.As pH levels move away from this range (up or down) it canstress animal systems and reduce hatching and survival rates.The further outside of the optimum pH range a value is, thehigher the mortality rates. The more sensitive a species, themore affected it is by changes in pH. In addition to biologicaleffects, extreme pH levels usually increase the solubility ofelements and compounds, making toxic chemicals moremobile and increasing the risk of absorption by aquatic life .Aquatic species are not the only ones affected by pH. Whilehumans have a higher tolerance for pH levels (drinkable levelsrange from 4-11 with minimal gastrointestinal irritation), thereare still concerns . pH values greater than 11 can cause skin and eye irritations, as does a pH below 4. A pH value below 2.5 will cause irreversibledamage to skin and organ linings . Lower pH levels increase the risk of mobilized toxic metals that can be absorbed, even by humans, and levelsabove 8.0 cannot be effectively disinfected with chlorine, causing other indirect risks . In addition, pH levels outside of 6.5-9.5 can damage andcorrode pipes and other systems, further increasing heavy metal toxicity.Even minor pH changes can have long-term effects. A slight change in the pH ofwater can increase the solubility of phosphorus and other nutrients making themmore accessible for plant growth . In an oligotrophic lake, or a lake low in plantnutrients and high in dissolved oxygen levels, this can cause a chain reaction. Withmore accessible nutrients, aquatic plants and algae thrive, increasing the demand fordissolved oxygen. This creates a eutrophic lake, rich in nutrients and plant life butlow in dissolved oxygen concentrations. In a eutrophic lake, other organisms living inthe water will become stressed, even if pH levels remained within the optimumrange. Factors that Influence the pH of WaterThere are many factors that can affect pH in water, both natural and man-made.Most natural changes occur due to interactions with surrounding rock (particularly carbonate forms) and other materials. pH can also fluctuate withprecipitation (especially acid rain) and wastewater or mining discharges . In addition, CO2 concentrations can influence pH levels. Carbon Dioxide and pHCarbon dioxide is the most common cause of acidity in water . Photosynthesis,respiration and decomposition all contribute to pH fluctuations due to theirinfluences on CO2 levels. The extremity of these changes depends on the alkalinityof the water, but there are often noticeable diurnal (daily) variations . This influenceis more measurable in bodies of water with high rates of respiration anddecomposition.While carbon dioxide exists in water in a dissolved state (like oxygen), it can alsoreact with water to form carbonic acid:CO2 + H2O H2CO3H2CO3 can then lose one or both of its hydrogen ions:H2CO3 HCO3+ H+ . HCO3 CO3 + H+The released hydrogen ions decrease the pH of water . However, this equation canoperate in both directions depending on the current pH level, working as its ownbuffering system. At a higher pH, this bicarbonate system will shift to the left,and CO3will pick up a free hydrogen ion.This reaction is usually minimal as H2CO3 has a low solubility constant (Henrys Law) . However, as CO2 levels increase around the world, theamount of dissolved CO2 also increases, and the equation will be carried out from left to right. This increases H2CO3, which decreases pH. The effectis becoming more evident in oceanic pH studies over time. 2- 2-pH of Water - Environmental Measurement Systems 7/28/2015http://www.fondriest.com/environmental-measurements/parameters/water-quality/ph/ 31 / 80Carbon dioxide in the atmosphere decreasesthe pH of precipitation.Lightning can lower the pH of rain.Decomposing pine needles candecrease pH.Pollution in the air, soil or directly in thewater can all affect pH.pH_ch