Aquatic EcologyAquatic Ecology

Chapter 7Chapter 7

Types of aquatic life zones:Types of aquatic life zones:

Saltwater or marine Saltwater or marine Estuaries, coastlines, Estuaries, coastlines,

coral reefs, coastal coral reefs, coastal marshes, mangrove marshes, mangrove swamps, and oceansswamps, and oceans

FreshwaterFreshwater Lakes and ponds, Lakes and ponds,

streams and rivers, streams and rivers, and inland wetlandsand inland wetlands

Major types of organismsMajor types of organisms Phytoplankton – plant planktonPhytoplankton – plant plankton

Free-floating microscopic Free-floating microscopic cyanobacteria and algaecyanobacteria and algae

• The producers and the basis The producers and the basis of the food chainof the food chain

Zooplankton – animal planktonZooplankton – animal plankton Nonphotosynthetic herbivores Nonphotosynthetic herbivores

that feed on phytoplanktonthat feed on phytoplankton Secondary consumers that Secondary consumers that

feed on other zooplanktonfeed on other zooplankton• Range from single-celled Range from single-celled

protozoa to large protozoa to large invertebrates such as jellyfish.invertebrates such as jellyfish.

NektonNekton Fish, turtles, and whalesFish, turtles, and whales

Benthos Benthos Bottom-dwellers – barnacles & Bottom-dwellers – barnacles &

oysters that anchor to one oysters that anchor to one spotspot

Worms – burrow into sand or Worms – burrow into sand or mudmud

Lobsters and crabs – walk on Lobsters and crabs – walk on the bottomthe bottom

Some are filter-feedersSome are filter-feeders Decomposers Decomposers

Bacteria that break down Bacteria that break down organic compoundsorganic compounds

Key Characteristics of aquatic Key Characteristics of aquatic organismsorganisms

Less pronounced and fixed physical Less pronounced and fixed physical boundaries; therefore difficult to count and boundaries; therefore difficult to count and manage populationsmanage populations

More complex and longer food chainsMore complex and longer food chains More difficult to monitor and study More difficult to monitor and study

because of their size and they are hidden because of their size and they are hidden from view.from view.

Limiting FactorsLimiting Factors

Aquatic life zones are divided into three Aquatic life zones are divided into three layers – surface, middle, and bottomlayers – surface, middle, and bottom

Factors are:Factors are: TemperatureTemperature Access to Access to sunlightsunlight for photosynthesis for photosynthesis Dissolved oxygenDissolved oxygen (DO) content (DO) content Availability of Availability of nutrients nutrients such as carbon (COsuch as carbon (CO22),), nitrogen (NOnitrogen (NO33), and phosphorus (PO), and phosphorus (PO44) for ) for

producersproducers

Photosynthesis can take place only as deep as Photosynthesis can take place only as deep as light can penetrate (euphotic zone)light can penetrate (euphotic zone)

Oxygen gets in from photosynthesis and Oxygen gets in from photosynthesis and diffusion for air and is removed by aerobic diffusion for air and is removed by aerobic respiration (includes decomposition)respiration (includes decomposition) OO22 can vary greatly in aquatic ecosystems can vary greatly in aquatic ecosystems Most aquatic organisms cannot survive below 5 ppm Most aquatic organisms cannot survive below 5 ppm

of DOof DO DO and CODO and CO22 concentrations vary with depth concentrations vary with depth

Why are oceans important?Why are oceans important?

Cover 71% of earth’s surfaceCover 71% of earth’s surface Contain about 250,000 known speciesContain about 250,000 known species Provide many ecological and economic Provide many ecological and economic

servicesservices Less that 5% has been explored and Less that 5% has been explored and

mappedmapped

Coastal zoneCoastal zone

Warm,nutrient-Warm,nutrient-rich,shallow water that rich,shallow water that extends from the high tide extends from the high tide mark to the margin of the mark to the margin of the continental shelfcontinental shelf

makes up less than 10% makes up less than 10% of ocean but contains of ocean but contains 90% of all marine species 90% of all marine species and is especially and is especially important to commercial important to commercial fisheries.fisheries.

Gets:Gets: Sunlight and nutrientsSunlight and nutrients

Estuaries – a partially enclosed area where Estuaries – a partially enclosed area where seawater mixes with fresh waterseawater mixes with fresh water An ecotoneAn ecotone

Coastal Wetlands – covered by water all or part Coastal Wetlands – covered by water all or part of the yearof the year river mouths, inlets, bays, sounds, mangrove river mouths, inlets, bays, sounds, mangrove

swamps, and salt marshesswamps, and salt marshes Temperature and salinity vary widely Temperature and salinity vary widely

Tides, seasonal variation in water flow, unpredictable Tides, seasonal variation in water flow, unpredictable flows after heavy rains and floodsflows after heavy rains and floods

VERY PRODUCTIVE AREAS!VERY PRODUCTIVE AREAS!

Intertidal zone – area of Intertidal zone – area of shoreline between high shoreline between high and low tidesand low tides

Very stressful zone for Very stressful zone for organisms:organisms:

Wave stressWave stress Immersed during high tides Immersed during high tides

and dry during low tidesand dry during low tides Changing levels of salinityChanging levels of salinity Organisms usually cling to Organisms usually cling to

something, dig or hide in something, dig or hide in shells.shells.

Barrier IslandsBarrier Islands Long, thin, low Long, thin, low

offshore islands of offshore islands of sedement that sedement that generally run parallel generally run parallel to shoreto shore

Help protect mainlandHelp protect mainland Constantly shiftConstantly shift

Coral reefsCoral reefs

Form in clear, warm, coastal waters in tropics and Form in clear, warm, coastal waters in tropics and subtropicssubtropics

Have many types of organismsHave many types of organisms Attached – corals, algae, and spongesAttached – corals, algae, and sponges FishesFishes Small organisms that bore into or attach themselves to coralSmall organisms that bore into or attach themselves to coral

Easily damaged, grow slowly, can survive only in clear, Easily damaged, grow slowly, can survive only in clear, shallow, warm watershallow, warm water

Have been harmed by global warmingHave been harmed by global warming They face many threats from pollution and other human They face many threats from pollution and other human

activities.activities.

Open SeaOpen Sea Beyond the continental Beyond the continental

shelfshelf Euphotic zone: lighted Euphotic zone: lighted

upper areaupper area PhotosynthesisPhotosynthesis Low nutrient levelsLow nutrient levels High DOHigh DO

Bathyl zone: dimly lit Bathyl zone: dimly lit middle zonemiddle zone

No photosynthesisNo photosynthesis Abyssal zone: dark lower Abyssal zone: dark lower

zonezone Very coldVery cold Little DOLittle DO Many nutrientsMany nutrients

Some open sea organismsSome open sea organisms

Deposit feedersDeposit feeders Take mud into their Take mud into their

bodies and extract bodies and extract nutrients from itnutrients from it

Filter feedersFilter feeders Pass water through or Pass water through or

over their bodies and over their bodies and extract nutrients from itextract nutrients from it

Average primary Average primary productivity & NPP productivity & NPP are low.are low.

Human ImpactHuman Impact

Losing coastal areas to developmentLosing coastal areas to development Housing, marinas, golf coursesHousing, marinas, golf courses

Filling in for agricultureFilling in for agriculture Much beach erosion due to development Much beach erosion due to development

and rising sea levelsand rising sea levels Dredging and heavy nets used in trawling Dredging and heavy nets used in trawling

is destroying bottom habitatsis destroying bottom habitats Coral reefs are being severely damagedCoral reefs are being severely damaged

Freshwater life zonesFreshwater life zones

Found where water with a dissolved salt Found where water with a dissolved salt concentration of less than 1% by volume either concentration of less than 1% by volume either accumulates or flows through the surfaces of accumulates or flows through the surfaces of terrestrial biomes.terrestrial biomes. Standing water – lakes, ponds, inland wetlandsStanding water – lakes, ponds, inland wetlands Flowing water – streams and riversFlowing water – streams and rivers

Covers less than 1% of the earth’s surface but Covers less than 1% of the earth’s surface but ecologically and economically importantecologically and economically important

Are very closely connected to terrestrial biomes Are very closely connected to terrestrial biomes due to nutrient run-offdue to nutrient run-off

Life zonesLife zones Ponds – shallow – light often penetrates to the Ponds – shallow – light often penetrates to the

bottom – usually have only one zonebottom – usually have only one zone Lakes – deeper – generally consist of four zones Lakes – deeper – generally consist of four zones

– defined by depth and distance from shore– defined by depth and distance from shore Littoral zone – shallow water near shore where rooted Littoral zone – shallow water near shore where rooted

plants growplants grow Limnetic zone – open sunlit water away from shore – Limnetic zone – open sunlit water away from shore –

as deep as sunlight penetratesas deep as sunlight penetrates Profundal zone – deep open water that receives no Profundal zone – deep open water that receives no

sunlight – cool so although oxygen is low, some fish sunlight – cool so although oxygen is low, some fish live here.live here.

Benthic zone – bottom of lake – cool temperatures Benthic zone – bottom of lake – cool temperatures and low oxygenand low oxygen

Freshwater Systems

Ecological Services Economic Services

• Climate moderation

• Nutrient cycling

• Waste treatment and dilution

• Flood control

• Groundwater recharge

• Habitats for aquatic and terrestrial species

• Genetic resources and biodiversity

• Scientific information

• Food

• Drinking water

• Irrigation water

• Hydroelectricity

• Transportation corridors

• Recreation

• Employment

© 2004 Brooks/Cole – Thomson Learning

Eutrophication – the natural ageing Eutrophication – the natural ageing of a lakeof a lake

Classify lakes according to nutrient content and Classify lakes according to nutrient content and primary productivityprimary productivity

OLIGOTROPHIC LAKE – low nutrientsOLIGOTROPHIC LAKE – low nutrients Geographically youngGeographically young DeepDeep Blue in colorBlue in color ColderColder Low populations of phytoplanktonLow populations of phytoplankton More desirable fish – bass and troutMore desirable fish – bass and trout Low NPPLow NPP

EUTROPHIC LAKE – many nutrientsEUTROPHIC LAKE – many nutrients Old lakeOld lake ShallowShallow Green or brown in color (algae)Green or brown in color (algae) WarmerWarmer Algal blooms are commonAlgal blooms are common Less desirable types of fish – catfish, carpLess desirable types of fish – catfish, carp High NPPHigh NPP

FigurFigure 7-e 7-2121

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Sunlight

Little shore vegetation

Limnetic zone

Profundalzone

Oligotrophic lake

Low concentration of nutrients and plankton

Sparse fish population

Narrow littoral zone

Sleepily sloping shorelines

Sand, gravel, rock bottom

Sunlight

Much shore vegetation

Limnetic zone

Profundalzone

Eutrophic lake

High concentration of nutrients and plankton

Dense fish population

Widelittoral zone

Gentlysloping shorelines

Silt, sand, clay bottom

Cultural EutrophicationCultural Eutrophication

Humans add nutrients from the Humans add nutrients from the atmosphere, urban, and agricultural areas atmosphere, urban, and agricultural areas accelerate eutrophication.accelerate eutrophication.

SEASONAL CHANGES IN LAKESSEASONAL CHANGES IN LAKES

Occurs in temperate lakeOccurs in temperate lake Makes use of the property of water that it Makes use of the property of water that it

is less dense as a solid (0is less dense as a solid (0ooC) then it is at a C) then it is at a liquid (4liquid (4ooC);therefore ice floats on water.C);therefore ice floats on water.

This causes THERMAL STRATIFICATION This causes THERMAL STRATIFICATION of deep lakesof deep lakes

SummerSummer

Lakes have three distinct layers:Lakes have three distinct layers: EPILIMNION – upper layer of warm water high levels of EPILIMNION – upper layer of warm water high levels of

DODO THERMOCLINE – layer where the temperature changes THERMOCLINE – layer where the temperature changes

with depth – usually 1with depth – usually 1ooC/meter increase in depth – C/meter increase in depth – moderate oxygen – during summer acts as a barrier moderate oxygen – during summer acts as a barrier between epilimnion and hypolimnionbetween epilimnion and hypolimnion

HYPOLIMNION – bottom layer of cold, dense water – HYPOLIMNION – bottom layer of cold, dense water – low DOlow DO

To keep cool fish would be at the bottom but low DO To keep cool fish would be at the bottom but low DO therethere

Fall OverturnFall Overturn

Water begans to cool, becomes more Water begans to cool, becomes more dense and sinks to the bottom dense and sinks to the bottom

The thermocline disappearsThe thermocline disappears Water mixes – nutrients are carried to the Water mixes – nutrients are carried to the

top and oxygen to the bottom. Fish can be top and oxygen to the bottom. Fish can be found at all depthsfound at all depths

WinterWinter

Lake separates into layers again due to Lake separates into layers again due to difference in density.difference in density.

Warmest (4Warmest (4ooC)water is at the bottomC)water is at the bottom Thermocline is reversedThermocline is reversed Coldest water is at the top and freezes Coldest water is at the top and freezes

forming ice which insulates and protects forming ice which insulates and protects the lake.the lake.

Spring overturnSpring overturn

Water begins to warm upWater begins to warm up Wind blows causing vertical currentsWind blows causing vertical currents Lake overturns again bring nutrients to the Lake overturns again bring nutrients to the

top and oxygen to the bottomtop and oxygen to the bottom

Characteristics of FreshwaterCharacteristics of Freshwater

Surface water forms when precipitation Surface water forms when precipitation that does not sink into the ground or that does not sink into the ground or evaporate becomes run-offevaporate becomes run-off

Watershed – the land area that delivers Watershed – the land area that delivers run-off, sediment, and dissolved run-off, sediment, and dissolved substances to a stream.substances to a stream.

Streams join together to form riversStreams join together to form rivers Rivers flow downhill to the oceanRivers flow downhill to the ocean

Inland wetlands – land covered with water Inland wetlands – land covered with water all or part of the year located away from all or part of the year located away from the oceanthe ocean Marshes – have a few treesMarshes – have a few trees Swamps –dominated by trees and shrubsSwamps –dominated by trees and shrubs Prairie potholes – depressions formed by Prairie potholes – depressions formed by

glaciersglaciers Floodplains – receive water during heavy Floodplains – receive water during heavy

rains or floodsrains or floods Bogs and fens – waterlogged peaty areasBogs and fens – waterlogged peaty areas

Human impactHuman impact

60% of the world’s largest rivers are 60% of the world’s largest rivers are fragmented by dams – destroys wildlife fragmented by dams – destroys wildlife and reduces water flowand reduces water flow

Flood control levees and dikes – destroy Flood control levees and dikes – destroy habitats, disconnect rivers from habitats, disconnect rivers from floodplains,and eliminate wetlandsfloodplains,and eliminate wetlands

In U.S. 53% of the wetlands have been In U.S. 53% of the wetlands have been drained or filled to grow crops – this has drained or filled to grow crops – this has increased floodingincreased flooding