AQUATIC ECOLOGY AND LIMNOLOGY

IKENWEIWE Bolatito Nafisat

SENIOR LECTURERSENIOR LECTURERDEPARTMENT OF AQUACULTURE AND

FISHERIES MANAGEMENTUNIVERSITY OF AGRICULTURE, ABEOKUTA

AQUATIC ECOLOGY AND LIMNOLOGYAQUATIC ECOLOGY AND LIMNOLOGY

titobola2007@yahoo.com, , 0803377026508033770265

AQUATIC ECOLOGY AND LIMNOLOGY

FIS 703

(3 Units)

Course outline

• Classification of aquatic systems. 

• Physio-Chemical parameters of aquatic environment plankton and benthos. 

• Primary and Secondary Production,

• energy budget

The basic needs of aquatic biota?

• Carbondioxide • Oxygen• Sunlight• Nutrients- food &

minerals

Types of Aquatic Ecosystems

• Freshwater Ecosystems– Standing Water- lakes &

ponds– Moving Water- rivers &

streams• Transitional Communities

– Estuaries– Wetlands- bogs/fens,

swamps, marshes• Marine Ecosystems

– Shorelines– Barrier Islands– Coral Reefs– Open Ocean

FreshwaterFreshwater contribute about 0.31% and many of the large rivers of the world lie in the tropical and sub-tropical zones

Transitional Communities

• ESTUARIES• Where freshwater dumps

into ocean• Brackish (less salty than

seawater)• Has rich sediments that

often form deltas• Productive & biodiverse• Organisms adapted to

varying levels of salinity as tide ebbs & flows

• “Nursery” for larval forms of many aquatic species of commercial fish & shellfish

Transitional Communities

• WETLANDS• Land saturated at least part of

the year• Swamps- have trees like bald

cypress; high productivity• Marshes- no trees; tall

grasses; high productivity• Bogs/Fens- may or may not

have trees; waterlogged soil with lots of peat; low productivity– Fens- fed by groundwater &

surface runoff– Bogs- fed by precipitation

Bog

Fen

Swamp

Marine Ecosystems

• SHORELINES• Rocky coasts- great density &

diversity attached to solid rock surface

• Sandy beaches- burrowing animals

• Threats- due to hotels, restaurants, homes on beach, more plant life destroyed, destabilizing soil, susceptible to wind & water erosion

• Insurance high; danger of hurricanes, erosion

• Build sea walls to protect people but changes & endangers shoreline habitat

MARINE

• Oceans,

• Seas, and

• Other saline water – They all constitutes 97.69% and few usually

contains higher nutrient concentrations than the sea water

Universal solvent

• Water is a universal solvent. • There are also a number of minor constituents in

solution,• variety of colloidal materials, both inorganic and organic. • Several gases are also found in natural water.• Water contains larger or smaller concentration of all

elements found in the earth crust and in the atmosphere.• Furthermore, most of the organic compounds

synthesized by living organisms may be found in water.

Dissolved gases

The gases that can be found in dissolved form in water include:

• oxygen,

• carbon dioxide,

• nitrogen,

• ammonia,

• hydrogen sulphate and

• methane

Mineral constituents

Mineral constituents of water include calcium, magnesium, sodium, potassium, iron, manganese, aluminium, zinc, copper, molybdenum, sulphur, chlorine, fluorine, iodine, boron and silicon. These elements are usually present as ions or complex organic or inorganic molecules.

Soluble Organic Matter

Water soluble organic matter include: • sugar, fatty acids, • humic acids, tannin, • vitamins, amino acids, • peptides, protein, • plant pigments, urea and• many other biochemical compounds

Suspended Inorganic Matters

The suspended inorganic matters include:

• colloidal clay and

• coarse suspension of soil particles.

Colloidal or suspended particles are:

• remains of organism in various stages of decay,

• living phytoplankton, zooplankton, fungi and bacteria

TYPES OF WATERTYPES OF WATER

Lotic i.e flowing water

Lentic i.e. static or stagnant water

LIMNOLOGY

LIMNOLOGY

•LIMNO means lake,

• LOGY means study

It is the study of fresh water habitat which involves the study of physical chemical and biological as well as geographical location (longitude and latitude) characteristics of fresh water environment.

LIMNOLOGYLIMNOLOGY

Limnology is divided into two:

• Lentic water which is static, water lakes and pond

• Lotic water which is flowing, streams and rivers

PHYSICAL LIMNOLOGYThese include:

• Temperature, Light, • Turbidity (colour), Viscosity, • Water density, • Water current (speed and direction), • Depth, • Amount of suspended/floating/sinking

organisms, and• Physical nature of substance (atoms).

TEMPERATURE

Temperature is defined as the degree of hotness or coldness.

Effects of temperature

• Affect states of water (solid, liquid and gas).

• Temperature also affect dissolved gas e.g. amount of soluble salt in water increases as temperature increases

• Affect biology of aquatic organisms.

• Difficult to transfer fish geographically except when water is heated artificially in cold region

• It also affect solubility e.g. in warm water, fertilizer dissolved faster, herbicides act quicker, rotenone degrades faster and rate of oxygen consumption by decaying manure is greater.

Effects of temperature cont’d

MetabolismIn high temperature rate of metabolism is increase, hence increase growth as the organisms require more than enough food to supply energy with which to compensate the high metabolic rate

Effects of temperature cont’d

Reproduction• Tropical fish would breed only at

temperature greater than 20oC. Embryo develops into fingerling slow at low temperature of less than 20oC.

• At high temperature (30oC) some aquatic organism hibernate in mud, under stones

• zooplankton lay eggs with cyst preparing for drought.

Effects of temperature cont’d

Thermal stratification and mixing• Water is divided into 1,2, or 3 parts. Upper

part warmer, lower part colder and temperature decreases with depth,

• Dividing water into Epilimnion, Hypolimnion and middle Metalimnion with a a sharp change in temperature called Thermocline.

• At high temperature water become lighter, less dense and mixing (upwelling is increase).

• Even at different part of a river e.g. edges are warmer, lighter, cooler and denser towards middle.

• Shallow depth at the edge with low volume i.e. horizontal zonation.

VARIATIONS IN WATER

TEMPERATUREThe variation in temperature of

water bodies are:• Partial variation in temperature

• Diurnal variation

• Seasonal variation

WATER STRATIFICATION (THERMAL)

Due to temperature difference, Lentic water is divide into three layers,

• Epilimnion, • Hypolimnion and • Metalimnion

UPWELLING

Upwelling is caused as a result of thermal stratification

Classification of Upwelling

Upwelling classified on the basis of number of times to occur includes:

• MONOMICTIC - upwelling occur once in a year e.g. in Nigeria, it occur during rain of July - Oct.

• DIMITIC - upwelling that occurs twice in a year. During rain and harmatan e.g. North Nigeria

• POLYMICTIC - upwelling occurring several times in a year. Most ideal for aquaculture.

• MEROMICTIC - uncompleted upwelling only some partial, not reach lower part

• HOLOMICTIC - complete mixing of both lower and upper part

Measurement of temperature

• Simple mercury in glass thermometer that ranges between 0oC-50oC e.g. reversing thermometer and thermogram can be used to measure temperature of 1000km away on satellite.

Electrical thermometer operated using batteries and resistance wire with amount of current to temperature

Temperature can also be measured using:

DENSITY

• Density is mass per unit volume (g/cm3).

• Closely related to viscosity and specific gravity. Viscosity is the relative amount of water molecules in relation to one another.

• Water density affect movement of organisms. Organisms can move on dense water than on light water by floating.

Density and Temperature

Density is also affected by temperature, increase in temperature result in low density though to a maximum temperature of 4oC when it is constant

Water Density and Water Density and SalinitySalinity

Water density is also affect by salinity (amount of salt in water).

Water containing high salt concentration has increase water density compared with water with low salt concentration.

Measurement of Measurement of DensityDensity

Density can be determined by using:

• Hydrometer

• Specific gravity bottle

LIGHT/WATER TRANSPARENCY

This is the amount of light entering the water

Factors Affecting Water Factors Affecting Water TransparencyTransparency

• Light intensity

• Angle of incident ray

• Geographical area (higher in the tropics)

• Time of the day

• Water movement

• Season

• Water quality

TURBIDITY

Amount of suspended solids in water

Effect of TurbidityEffect of Turbidity

When light penetrated water, suspended solid absorb/reflect light rays reducing amount of light going beyond them.

Thus, the more dissolved solid, the more turbid water and the less light penetrate it.

Effects of Light IntensityEffects of Light Intensity

• Embryo activity• Breeding period • Visibility• Avoidance of enemies

Light intensity affectLight intensity affect :

Effects of light intensity cont’d

At optimum light intensity

• Higher photosynthesis thus dissolved oxygen released into the atmosphere and carbon dioxide is removed

• More nutrients NO3-, PO4-, etc are utilized thus pH becomes greater (alkali) as all the acidic CO2 are used up.

Measurement of water transparency

• PHOTOMETER which convert radiant energy of light into electric energy and recorded.

• SECCHI DISC measure light depth penetration.

WATER COLOUR

•True water colour is caused by the amount of substance in solution/ colloidal suspension in it.

• colour result from unabsorbed light ray.

The main reason the ocean is blue is that water itself is a blue-colored chemical. Optical scattering from water molecules provides a second source of the blue color, but colored light caused by scattering only becomes significant with extremely pure water

WATER DEPTH

Depth shows relative distance between the beds of water to the overlain shallow water.

• Light penetration• Thermal stratification • Volume • Photosynthesis and • Distribution of organism in the

water body

Water Depth is related to:

CHEMICAL LIMINOLOGYCHEMICAL LIMINOLOGY

• DISSOLVED OXYGEN • SALINITY• HYDROGEN ION CONCENTRATION• CARBON DIOXIDE• ALKALINITY• NITROGEN• SULPHUR • SILICON

Involves:Involves:

DISOLVED DISOLVED OXYGENOXYGEN

• It is important in the tropics due to relatively high temperature which allow low dissolved oxygen.

• At high temperature, metabolic activity rate increase at each 10oC hence more oxygen is required whereas low dissolved oxygen is available.

SOURCES OF DO

• from atmosphere, air by simple diffusion into surface water.

• photosynthesis - green plants, all bacteria, phytoplankton and higher plants

• oxidation processes which is a chemical process e.g. Fe2+ Fe3+,

• NH3 O2, NO2 NO3; CCO2/CO3; P PO4-

Factors Affecting DO Factors Affecting DO Concentration In WaterConcentration In Water

• There are variety of factors which affect dissolved oxygen in water either positively or negatively.

• Some of these factors are listed below.

These factors include:

• Temperature

• Diurnal variation

• Atmospheric pressure. Low pressure gives low DO

• Altitude. At higher up the mountain, temperature is low and DO is high.

• Water movement

Factors Affecting DO Conc. In Water Factors Affecting DO Conc. In Water (cont’d)(cont’d)

• Photosynthetic activities during the day time • respiration • Organic concentration• Presence of suspended materials which intercept

with light penetration• Water chemistry- chemical reaction due to

oxidation of Fe2+, NH3, C and P • High salinity also result in low dissolved oxygen

e.g. 20mg salt decreases oxygen by 0.008mg/threshold.

Variation in DOVariation in DO

Observed variation in DO can be described as:

• Diurnal (day and night)• Seasonal (dry and wet seasons)• In running water (rivers and

stream, due to water movement, mixing occur, hence high DO)

• Spatial variation-(upper and lower parts; deep and shallow water)

• Thermal stratification: In deeper water bodies, occasionally mixing increases DO at onset of thermal stratification, hypolim has high dissolved oxygen and latter falls.

DISSOLVED OXYGEN AND FISH DISSOLVED OXYGEN AND FISH CULTURECULTURE

• In good water quality

NH3 NO3,

C CO2/CO3,

P PO4

• Thus, help to sanitized the water, converting some toxic substances into useful ones.

• In high DO, fish feed well and the rate of metabolism increases resulting in growth.

• In low DO, there is low metabolic rate, fish feed poorly and result in low growth as it waste energy gasping for oxygen

• Pathogenic bacteria, fungi, leeches thrive well

• Disease outbreak is encouraged leaving damage on fish skin

In Low DO:In Low DO:

Super saturation of dissolved oxygen causes fish mortality

This result because of gas bubble disease in young fish. As a result of excess oxygen in their blood

AERATING THE WATER TO INCREASE DOAERATING THE WATER TO INCREASE DO

• Using aerators to pump air into water

• Water agitators act like propellers • Some paddle like• Allow water to drop from a shower-

like tap into the water body.

• Using oxygen meter, (in mg/litre or percentage oxygen saturation)

• WINKLER'S THMETRIC method

• TITRATION

DETERMINATION OF O2 LEVEL

If one spit on water and the spit remain intact without mixing, it implies low oxygen concentration. If water body is stirred and it foams, it implies pollution and low oxygen concentration

SALINITY

Salinity

It is the amount of dissolved salt in water in parts per thousand use

• salinity is the amount of salt dissolved in one litre of water.

• Fresh water has little salt (<0.05% of salt in one litre), marine = 20-37%, brackish = 5-20%.

Based on salt content Water bodies are classified as:–hyposaline,

–mesosaline, and

–hypersaline.

EFFECTS OF SALINITY

• Salinity affect productivity • Excess salt results in water

pollution• Osmoregulation: In fresh water,

organisms spend more energy to control osmoregulation.

• Increase in salinity affect organism’s distribution (fresh and marine water).

• Salinity also affects biology of organism in water.

Variation in Variation in salinitysalinity

• Seasonal variation–Raining season–Dry season

• Spatial variation–low in areas with lot of rain – high in place with little or no rain

•Water body–lakes are greatly saline–saline in standing water bodies is greater than that of flowing river

Factors Affecting Factors Affecting SalinitySalinity

• Temperature

• Rainfall

• Organisms– certain mollusks and fishes absorb salt to

make their body shell

• Decaying organisms

• Man

• Geochemistry of the bed rock

MEASUREMENT OF MEASUREMENT OF SALINITYSALINITY

• Evaporated at temperature of 60-80oC (not use in fresh water)

• Measuring the amount of chlorine using salt meter

• using titration method -titrate AgNO3 + saline water using K2Cr2O7 (chromate) as indicator

SALT CONCENTRATION AND SALT CONCENTRATION AND CONDUCTIVITYCONDUCTIVITY

• Electrical conductivity is determined based on number of charge.

• The more the salt, the greater the charges

• Using two electrodes with conductivity meter, current is measured in mho/cm or ohm-1/cm.

HYDROGEN ION CONCENTRATION (pH)HYDROGEN ION CONCENTRATION (pH)

• This is the degree of acidity or alkalinity of water.

• It ranges from 1-14 (1-6.9 is acidic, 7.0 is neutral, 7.1-14 is alkaline).

•pH also reflects presence of salts in water

•Rain water contains CO2 which form carbonic acid and makes the water more acidic i.e. low pH.

•Urban water contain sulphur compounds which form H2SO4 with water

•Urban water also contain heavy metals, divalent elements e.g. Ca, Mg, which is alkali.

VARIATIONS IN pHVARIATIONS IN pH

•Diurnal variation

•Bed rock

•Productivity

lime is added to water to regulate its pH.

MEASUREMENT OF pHMEASUREMENT OF pH

• using pH meter

• pH solutions e.g. methyl red

• pH paper • Litmus paper dips in water

CARBON DIOXIDECARBON DIOXIDE (CO2)

• This is the dissolved carbon dioxide in water

• Concentration of carbon dioxide depends on photosynthetic and respiratory activities in water

PHOSPHORUSPHOSPHORUS

• Phosphorus is one of the key metabolic nutrient

• Its presence regulate phytoplankton and plant product

• Presence of H3PO4 IONIZABLE ORGANIC phosphates from effluents, soluble organic phosphorus.

NITROGENNITROGEN

• Most Nitrogen in organic matter exist as acids in CHON which are de-aminated to give NH3.

• Nitrogen undergoes ammonification to release NH3 into environment by a heterotrophic process i.e aerobic/anaerobic release NH4

+ used by aquatic plants.

Sources of Sources of NitrogenNitrogen

• Biological,

• Meteorological and • Industrial.

• When Nitrogen is used in fertilizing the pond, When Nitrogen is used in fertilizing the pond, the concentration declines quickly the concentration declines quickly

• Must have been absorb by plants which release Must have been absorb by plants which release it to bottom mud when dead.it to bottom mud when dead.

• denitrified in hypolimnion plus mud.denitrified in hypolimnion plus mud.

• absorb by mud.absorb by mud.

• loss through volatilization of NHloss through volatilization of NH33 during high during high

pH in the afternoon.pH in the afternoon.

PRIMARY PRODUCTIVITY

This is the synthesis of organic materials from inorganic materials, needed for the sustenance of an ecosystem.

This is the synthesis of organic materials from inorganic materials, needed for the sustenance of an ecosystem.

Primary Production Cont’d

• Primary production set in energy into the ecosystem.

• The producers are the chlorophyll bearing algae, macrophyte, autotrophic bacteria and other phytoplankton.

• Chemoautotrophic bacteria can be responsible for up to 25% of the primary production.

Further Readings

• Water Quality Textbook by Boyd and Lichtopler

• Ikenweiwe, N.B, D. Odulate, B. Adigun (2011) Ichthyology and Limnology: Tools In Fisheries Management Fisheries Management. United Kingdom. Lap Lambert Academic Publishing. ISBN: 978-3-8433-9364-5. Available online at http://dnb.b-nb.de 127 pages

• Ikenweiwe B. and S. Otubusin (2010). Limnology and Plankton Abundance. Germany. Verlag Publisher. ISBN- 10: 3639253167, ISBN-13: 9783639253160 (Available online at http://www.researchbooks.org/3639253167/LIMNOLOGY-PLANKTON-ABUNDANCE-FISH-PRODUCTION/). 249 pages.

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