11

CHAPTER 3CHAPTER 3

LIFE IN WATERLIFE IN WATER

22

Hydrological CycleHydrological Cycle

– Over 71% of the earth’s surface is covered with water. Over 71% of the earth’s surface is covered with water. Oceans contain over 97% of the water in the biosphere, Oceans contain over 97% of the water in the biosphere, less than 1% is fresh water.less than 1% is fresh water.

– Hydrological Cycle: process of exchange water among Hydrological Cycle: process of exchange water among various “reservoirs”.various “reservoirs”.

– The hydrological cycle is solar driven, with different The hydrological cycle is solar driven, with different turnover time for various reservoirs.turnover time for various reservoirs.

– Turnover time: Time require for the entire volume of Turnover time: Time require for the entire volume of particular reservoirs to be renewed. Size, rates effect particular reservoirs to be renewed. Size, rates effect Turnover.Turnover.

– Turns over time for atmosphere is about 9 days, Turns over time for atmosphere is about 9 days, renewal time for river water 12 to 20 days, Oceans renewal time for river water 12 to 20 days, Oceans 3,100 years. 3,100 years.

33Fig. 3.2Fig. 3.2

44

Natural History of aquatic environmentNatural History of aquatic environment– Biology of aquatic environments corresponds Biology of aquatic environments corresponds

broadly to variations in physical factors such as broadly to variations in physical factors such as light, temperature, water movement, and light, temperature, water movement, and chemical factors such as salinity and oxygen.chemical factors such as salinity and oxygen.

– World oceans covers over 360 million km² and World oceans covers over 360 million km² and consists of one continuous interconnected consists of one continuous interconnected mass of water.mass of water.

– Three major ocean basins: Pacific, Atlantic and Three major ocean basins: Pacific, Atlantic and Indian. Each with several smaller seas along its Indian. Each with several smaller seas along its margins.margins.

– Depth of Pacific (Average 4,000 m), Atlantic Depth of Pacific (Average 4,000 m), Atlantic and Indian (Average 3,900 m). Marianas trench and Indian (Average 3,900 m). Marianas trench at Pacific (10,000 m), deepest than Mount at Pacific (10,000 m), deepest than Mount Everest more than 2 km. Everest more than 2 km.

– Oceans are divided into vertical and horizontal Oceans are divided into vertical and horizontal zones. zones.

55Fig. 3.5Fig. 3.5

66Fig. 3.6Fig. 3.6

77

Physical ConditionsPhysical Conditions– LightLight

Approximately 80% of solar energy is absorbed in the first Approximately 80% of solar energy is absorbed in the first 10 m.10 m.

Within the visible range, red, orange, yellow and green are Within the visible range, red, orange, yellow and green are absorbed, while blue wave most likely to scattered, thus absorbed, while blue wave most likely to scattered, thus color of the sea is blue.color of the sea is blue.

Within 10 m different color is seen, while below 50 to 60 m Within 10 m different color is seen, while below 50 to 60 m it is blue color.it is blue color.

Light penetration (see fig.3.6).Light penetration (see fig.3.6).– Temperature Temperature

Sunlight absorbed by water increase Sunlight absorbed by water increase kinetic state, or kinetic state, or velocity of motion.velocity of motion.

Thermocline: a layer of water through which temperature Thermocline: a layer of water through which temperature change rapidly.change rapidly.

Thermal stratification: Layering of waters column by Thermal stratification: Layering of waters column by temperature.temperature.

Lowest temperature -1.5°C around the Antarctic, the Lowest temperature -1.5°C around the Antarctic, the highest average surface temperature a bit over 27°C near highest average surface temperature a bit over 27°C near the equator.the equator.

Maximum annual variation in surface temperature Maximum annual variation in surface temperature approximately 7 to 9°C .approximately 7 to 9°C .

The greatest stability just 100 m depth is less 1°C.The greatest stability just 100 m depth is less 1°C.

88

– Water movementWater movement Current transport nutrients, oxygen, and heat.Current transport nutrients, oxygen, and heat. Formation of circulation systems called “Formation of circulation systems called “gyersgyers” in which wind-” in which wind-

driven surface currents.driven surface currents. Circulation system move to right in the Northern Hemisphere, Circulation system move to right in the Northern Hemisphere,

while left in the Southern Hemisphere (Fig 3.5). while left in the Southern Hemisphere (Fig 3.5). Deep water may also moves to the surface in a process called Deep water may also moves to the surface in a process called

“Upwelling”.“Upwelling”. Different density and movement effect behavior and Different density and movement effect behavior and

distribution of marine organisms. distribution of marine organisms.

– SalinitySalinity Salinity: amount of salt dissolved in water.Salinity: amount of salt dissolved in water. Salinity varies from 34‰ to 36.5 ‰, with highest in Salinity varies from 34‰ to 36.5 ‰, with highest in

subtropical 20 to 30 N and S altitude.subtropical 20 to 30 N and S altitude. The relative proportions of major ions Na, Mg and Cl are The relative proportions of major ions Na, Mg and Cl are

approximately constant. approximately constant.

99

– OxygenOxygen Oxygen present in water with various concentation.Oxygen present in water with various concentation. 1 Liter of sea water approximately contains a maximum 1 Liter of sea water approximately contains a maximum

of about 9 ml, comparing to 200 ml in 1 L of air.of about 9 ml, comparing to 200 ml in 1 L of air. Typically oxygen concentration is highest near surface Typically oxygen concentration is highest near surface

and decrease progressively with depth. and decrease progressively with depth. The minimum oxygen concentration is found at 1,000 The minimum oxygen concentration is found at 1,000

m. m.

– Biology Biology Photosynthetic organisms (Phytoplankton) found in Photosynthetic organisms (Phytoplankton) found in

euphotic zone.euphotic zone. Zooplankton:Zooplankton: small animals drifting with sea current.small animals drifting with sea current. Chemosynthetic organisms in deep sea around thermal Chemosynthetic organisms in deep sea around thermal

vents.vents. Oceans consist the highest animal phyla especially Oceans consist the highest animal phyla especially

endemic one. endemic one.

1010

Fig. 3.9Fig. 3.9

1111

Life in Shallow Marine Water: Kelp Forests Life in Shallow Marine Water: Kelp Forests and Coral Gardenand Coral Garden

Shallow waters along the continents and around islands support high Shallow waters along the continents and around islands support high marine diversity and biomass. marine diversity and biomass.

At temperate latitude and over a solid bottom At temperate latitude and over a solid bottom brown seaweed (Kelp). Kelp structure (canopy, stems or stipes, and holdfasts) (fig 3.14) At the equator coral reefs confined between 30° N and S latitude. Categories of coral reefs : Fringing reefs, Barrier reefs, and atolls. (Fig

3.13). Distinctive habitats associated with coral reefs including:

– reef crest: Corals grow in the surge zone created by waves coming from the open sea, and extend to a depth of about 15 m.

– Buttress zone: Coral formation alternate with sand-bottomed canyons.

– Lagoon : found behind the reef crest that contains numerous small coral reefs called patch reefs and sea grass beds.

– Sea grass : plants found at the bottom of shallow waters.

1212Fig. 3.12Fig. 3.12

1313

Fig. 3.13Fig. 3.13

1414

Fig. 3.14Fig. 3.14

1515

– Physical conditionsPhysical conditions Sufficient light penetration is needed for seaweed and Sufficient light penetration is needed for seaweed and

reef-building coral. Depth of penetration from few reef-building coral. Depth of penetration from few meters to 100m.meters to 100m.

Temperature limits the distribution of both kelp and Temperature limits the distribution of both kelp and coral. coral.

– Kelp : below 10°C in winter and rise above 20°C in Kelp : below 10°C in winter and rise above 20°C in summer.summer.

– Coral : above 18°C to 20°C (average 23-25°C), sensitive Coral : above 18°C to 20°C (average 23-25°C), sensitive to higher temp, and lethal above 29°C.to higher temp, and lethal above 29°C.

Water moves continuously within the coral reefs and Water moves continuously within the coral reefs and kelp by oceanic currents.kelp by oceanic currents.

– Biological productivity of coral and kelp depend on the Biological productivity of coral and kelp depend on the flushing action of currents.flushing action of currents.

Corals and kelp depend on flushing action of the Corals and kelp depend on flushing action of the current.current.

Hurricanes could detached current or kelp from their Hurricanes could detached current or kelp from their locations, which may effect their long-term survival. locations, which may effect their long-term survival.

1616

– ConditionsConditions Corals grow only in fairly stable salinity, heavy rains Corals grow only in fairly stable salinity, heavy rains

or runoff from river reduce salinity below 27% can be or runoff from river reduce salinity below 27% can be lethal.lethal.

Kelps forest appears more tolerance to freshwater Kelps forest appears more tolerance to freshwater runoff near shore.runoff near shore.

Coral reefs and kelp beds found where water is well Coral reefs and kelp beds found where water is well oxygenated.oxygenated.

Coral reefs are effected by predatory crownof-thorn Coral reefs are effected by predatory crownof-thorn sea star, which eat corals.sea star, which eat corals.

Algae population compete for space with coral and Algae population compete for space with coral and kelp.kelp.

Coral species compete among themselves for space.Coral species compete among themselves for space. High species diversity of corals (over 600) that High species diversity of corals (over 600) that

support tremendous species of marine organisms and support tremendous species of marine organisms and fishes.fishes.

Human influence and practices on coral reefs ????. Human influence and practices on coral reefs ????.

1717

Marine Shores: Life between high and low Marine Shores: Life between high and low tidestides

The shores are most dynamic environments (tides, waves, light, The shores are most dynamic environments (tides, waves, light, splashes, erosion, depositions… ect).splashes, erosion, depositions… ect).

Intertidal zone: area covered by waves at high tide and exposed to Intertidal zone: area covered by waves at high tide and exposed to air at low tides.air at low tides.

Intertidal zone can be divided into several vertical zones Intertidal zone can be divided into several vertical zones (Supratidal fringe or splash zone, upper intertidal zone, middle, (Supratidal fringe or splash zone, upper intertidal zone, middle, lower, and subtidal) Fig. 3.17.lower, and subtidal) Fig. 3.17.

Intertidal zone exposed to air temperature, especially supratidal Intertidal zone exposed to air temperature, especially supratidal and upper, thus extremes temperatures(0-40 °C) effect organisms and upper, thus extremes temperatures(0-40 °C) effect organisms living in tide pools.living in tide pools.

Most two water movements effecting organisms are :Most two water movements effecting organisms are :– Semidiurnal (two high tides each day)Semidiurnal (two high tides each day)– Diurnal (Single high and low tide each day)Diurnal (Single high and low tide each day)– Spring tides (High tide at full moon)Spring tides (High tide at full moon)– Neap tides (High tide when moon and sun aligned )Neap tides (High tide when moon and sun aligned )

Organisms effected by exposed frequently to air, currents, Organisms effected by exposed frequently to air, currents, splashes. splashes.

1818Fig. 3.17Fig. 3.17

1919

– ConditionsConditions Salinity is varied especially at isolated pools within Salinity is varied especially at isolated pools within

intertidal zone.intertidal zone. Oxygen does not generally limit the distribution of Oxygen does not generally limit the distribution of

organisms because: organisms because: – Organisms exposed to air at low tide.Organisms exposed to air at low tide.– Waves mixes oxygen thoroughly.Waves mixes oxygen thoroughly.

Interstatial water within the sediment maybe low Interstatial water within the sediment maybe low along the muddy, sandy shores.along the muddy, sandy shores.

Zonation of species: Distribution of species within the Zonation of species: Distribution of species within the intertidal zone according to their adaptations to intertidal zone according to their adaptations to exposed environmental conditions.exposed environmental conditions.

Substrates effect on distributions (muddy, sandy and Substrates effect on distributions (muddy, sandy and rocky) as organisms adapt to live in it.rocky) as organisms adapt to live in it.

Human used the intertidal zone as source of food, Human used the intertidal zone as source of food, recreation, education , and research.recreation, education , and research.

2020

Estuaries, Salt Marshes, and Mangrove Estuaries, Salt Marshes, and Mangrove ForestForest

Estuaries: area where sea meet the river.Estuaries: area where sea meet the river. Mangroves forest: low laying area with mangrove trees. Fig. Mangroves forest: low laying area with mangrove trees. Fig.

3.22, 3.253.22, 3.25 Salt marshes: area of low-lying cost usually dominated by Salt marshes: area of low-lying cost usually dominated by

herbaceous plants and concentrated in sandy shores, and herbaceous plants and concentrated in sandy shores, and found from temperate to high latitude. Fig 3.24found from temperate to high latitude. Fig 3.24

ConditionsConditions– Currents is the heart of the estuaries and mangrove forest. Currents is the heart of the estuaries and mangrove forest. – Since salt marshes and mangrove effected by tide fluctuations. Since salt marshes and mangrove effected by tide fluctuations.

Hence, organisms in these environments are exposed to high Hence, organisms in these environments are exposed to high variations of light.variations of light.

– Water is turbid, suspended fine organic and inorganic matters.Water is turbid, suspended fine organic and inorganic matters.– Temperature is varies within the water, as it is shallow and Temperature is varies within the water, as it is shallow and

could reach 40°C. could reach 40°C. – Salinity fluctuate widely, evaporation and fresh water vs. sea.Salinity fluctuate widely, evaporation and fresh water vs. sea.– Fluctuation of salinity according to distance sea. Fig 3.26. Fluctuation of salinity according to distance sea. Fig 3.26. – Human influence, discharge of sewage, heavy metals, and Human influence, discharge of sewage, heavy metals, and

oxygen depletion. oxygen depletion.

2121

Fig. 3.22Fig. 3.22

2222Fig. 3.24Fig. 3.24

2323

Fig. 3.25Fig. 3.25

2424Fig. 3.26Fig. 3.26

2525

Rivers and Streams: Life Blood and Pulse of Rivers and Streams: Life Blood and Pulse of the Continentsthe Continents

Human history, ecology, and economy. (Nile, Tigris, …ect).Human history, ecology, and economy. (Nile, Tigris, …ect). Nonequilibrial theory, one of the newest branches of theoretical Nonequilibrial theory, one of the newest branches of theoretical

ecology: focuses on the river dynamic.ecology: focuses on the river dynamic. Rivers drain most of the landscapes of the world (rain-river basin, Rivers drain most of the landscapes of the world (rain-river basin,

drainage net work).drainage net work). River and streams can be divided along three dimensions. Fig River and streams can be divided along three dimensions. Fig

3.30.3.30. They can be divided along their They can be divided along their lengthslengths into: pools, runs, riffle and into: pools, runs, riffle and

rapid.rapid. River can be divided across their River can be divided across their widthwidth into: wetted channels and into: wetted channels and

active channels. active channels. A wetted channel contain water even during low conditions.A wetted channel contain water even during low conditions. Active channel which extends out from one or both sides of wetted Active channel which extends out from one or both sides of wetted

channel, may be dry during part of the year but is inundated channel, may be dry during part of the year but is inundated annually during high flows. annually during high flows.

Riparian zone: a transition between the aquatic environment of Riparian zone: a transition between the aquatic environment of the river and upland terrestrial environment. the river and upland terrestrial environment.

2626

Rivers and streams can be divided vertically into: Rivers and streams can be divided vertically into: water surface, water surface, the water column and bottom or benthic zone.the water column and bottom or benthic zone.

HyporheicHyporheic zonezone: : below the benthicbelow the benthic zonezone as it is transition between as it is transition between areas of surface water flow and groundwater.areas of surface water flow and groundwater.

Phreatic zone: area below the hyporheic zone which contain Phreatic zone: area below the hyporheic zone which contain groundwater.groundwater.

Each parts of a river or stream is physically and chemically Each parts of a river or stream is physically and chemically distinctive environments supporting different organisms.distinctive environments supporting different organisms.

ConditionsConditions– Streams Light influence according to: penetration and light intensity.Streams Light influence according to: penetration and light intensity.

– Generally streams are more turbid than lakes because Generally streams are more turbid than lakes because Rivers are more contacts with landscape (washing materials).Rivers are more contacts with landscape (washing materials). Erode bottoms and suspend bottom sediments.Erode bottoms and suspend bottom sediments.

– Temperature is close to air temperatures (0-30°C).Temperature is close to air temperatures (0-30°C).

– River is continuous movement of water. Different flow according to the River is continuous movement of water. Different flow according to the zones (pool, riffle….).zones (pool, riffle….).

– River discharge: amount of water carried by river.River discharge: amount of water carried by river.

– Streams and rivers could be “flashy” in arid and semiarid regions.Streams and rivers could be “flashy” in arid and semiarid regions. – Industrial discharge effect river or stream organisms. Industrial discharge effect river or stream organisms.

2727Fig. 3.30Fig. 3.30

2828

– Salinity in the rivers influenced by annual rainfall and leached Salinity in the rivers influenced by annual rainfall and leached soluble materials from the basin. Salinity ranges 10-100 folds. soluble materials from the basin. Salinity ranges 10-100 folds. Fig 3.33.Fig 3.33.

– Oxygen is inversely with temperature.Oxygen is inversely with temperature.– Organisms tolerate oxygen deficiencies are varied and Organisms tolerate oxygen deficiencies are varied and

distribution is based on that along the river or the stream.distribution is based on that along the river or the stream.– Number of fish species in tropical rivers is much higher than in Number of fish species in tropical rivers is much higher than in

temperate rivers.temperate rivers.– The organisms in the river changes from head-waters to The organisms in the river changes from head-waters to

mouth.mouth.– River continuum concept: Concept in which suggest that in River continuum concept: Concept in which suggest that in

temperate regions, leaves and other plant parts are often the temperate regions, leaves and other plant parts are often the major source of energy available to the stream ecosystem.major source of energy available to the stream ecosystem.

– According to this concept : Coarse particulate organic matter According to this concept : Coarse particulate organic matter (CPOM) attacked by microbes, then shredded by invertebrates, (CPOM) attacked by microbes, then shredded by invertebrates, to form fine particulate organic matter (FPOM).to form fine particulate organic matter (FPOM).

– In large rivers the major source of energy is FPOM, and in some In large rivers the major source of energy is FPOM, and in some rivers phytoplankton.rivers phytoplankton.

– Most of invertebrates of streams and rivers live or in the Most of invertebrates of streams and rivers live or in the sediments. Fig 3.34 .sediments. Fig 3.34 .

– Human influence on pollution, irrigation, transportation and Human influence on pollution, irrigation, transportation and recovery. recovery.

2929Fig. 3.33Fig. 3.33

3030

Fig. 3.34Fig. 3.34

3131

Lakes: Small SeasLakes: Small Seas Lakes are simply basins in the landscape that collect water.Lakes are simply basins in the landscape that collect water. 20% of fresh water is in lake Baikal. 20% of fresh water is in lake Baikal. Littoral zone: Shallowest water along the lake shore where rooted Littoral zone: Shallowest water along the lake shore where rooted

aquatic plant may grow. aquatic plant may grow. Limnetic zone: Zone beyond the littoral zone in the open lake.Limnetic zone: Zone beyond the littoral zone in the open lake. Lakes are generally divided vertically into three main depth zones:Lakes are generally divided vertically into three main depth zones:

– Epilimnion: the warm surface layerEpilimnion: the warm surface layer– Thermocline or metalimnion: a layer which temperature substantially with Thermocline or metalimnion: a layer which temperature substantially with

depth, generally about 1°C per meter of depth.depth, generally about 1°C per meter of depth.– Hypolimnion: lower layer below thermocline where water is cold and dark.Hypolimnion: lower layer below thermocline where water is cold and dark.

ConditionsConditions– Color of the lake depend on light absorption within the lake.Color of the lake depend on light absorption within the lake.– Lakes becomes thermally stratified as they heated. Fig 3.38Lakes becomes thermally stratified as they heated. Fig 3.38– Wind-driven mixing process through seasons.Wind-driven mixing process through seasons.– Oxygen depletion when decomposition occurs.Oxygen depletion when decomposition occurs.– Oligotrophic: well mixed lake with low biological productivity.Oligotrophic: well mixed lake with low biological productivity.– Eutrophic: low oxygen with high biological productivity.Eutrophic: low oxygen with high biological productivity.

3232

Fig. 3.37Fig. 3.37

3333Fig. 3.38Fig. 3.38

3434Fig. 3.39Fig. 3.39