Conservation of Conservation of Aquatic Aquatic EcosystemsEcosystems

Class 10Class 10

Presentation 2Presentation 2

Why aquatic ecosystems?Why aquatic ecosystems? 71% of earth covered by water71% of earth covered by water Fresh water systems compared to marine and Fresh water systems compared to marine and

terrestrial ecosystems most impacted by terrestrial ecosystems most impacted by humanshumans

Marine fish harvests have reached maxMarine fish harvests have reached max Huge decline in large fish numbers (sharks, Huge decline in large fish numbers (sharks,

barracuda, marlin etc)barracuda, marlin etc) Useful source of food, medicine, energy, Useful source of food, medicine, energy,

minerals.minerals. Marine biota very diverse:only 5% of animal Marine biota very diverse:only 5% of animal

phyla inhabit only land vs. 64% of animal phyla phyla inhabit only land vs. 64% of animal phyla inhabit seasinhabit seas

Unusual factUnusual fact

Nearly half of the photosynthesis Nearly half of the photosynthesis in the world is accounted for in a in the world is accounted for in a microscopic organism found on the microscopic organism found on the first 200 m of ocean surface: first 200 m of ocean surface: Prochlorococcus Prochlorococcus

Over 20,000 in each drop of sea Over 20,000 in each drop of sea waterwater

Only discovered in 1988Only discovered in 1988Berkeley Lab

Habitat features important for Habitat features important for fresh water systemsfresh water systems

Substrate:Substrate: sand & silt: poorest habitat, because sand & silt: poorest habitat, because

few attachments sites for few attachments sites for periphytonperiphyton and consumers and consumers

Boulders, rocks, gravel: better Boulders, rocks, gravel: better because larger surface area, more because larger surface area, more attachment sites, provide cover, attachment sites, provide cover, refuge, diverts force of moving water.refuge, diverts force of moving water.

Other habitat features Other habitat features important for fresh water important for fresh water systemssystems

Shore vegetation: siltation, water Shore vegetation: siltation, water seepage, climateseepage, climate

Topography, climate, parent Topography, climate, parent material, soil type, material, soil type,

Fresh water Fresh water

Lotic systems: flowing water ecosystemsLotic systems: flowing water ecosystems 2 dominant habitat features:2 dominant habitat features:

RifflesRiffles: sites of primary production, have : sites of primary production, have periphytonperiphyton: which are a community of : which are a community of organisms composed of diatoms, blue-green, organisms composed of diatoms, blue-green, & green algae, & aquatic mosses. Periphyton & green algae, & aquatic mosses. Periphyton is ephemeral moves down streamis ephemeral moves down stream

PoolsPools: catch basins below riffles, lower : catch basins below riffles, lower water flow, biomass accumulates, water flow, biomass accumulates, consumers accumulateconsumers accumulate

UBC Photo

Fresh water: Lentic Fresh water: Lentic systemssystems

Lake habitatLake habitat Little affected by internal currentsLittle affected by internal currents More by prevailing windsMore by prevailing winds Cells of water set in motion by wind, important for Cells of water set in motion by wind, important for

transport of food & heat vertically in water columntransport of food & heat vertically in water column Water density changes with tempWater density changes with temp Mobile aquatic organisms move with changes in Mobile aquatic organisms move with changes in

temp and water density like terrestrial organisms temp and water density like terrestrial organisms move to changes in vegetation cover.move to changes in vegetation cover.

Organisms move to different parts that allow them Organisms move to different parts that allow them to benefit in growth, reproduction and survivalto benefit in growth, reproduction and survival

Fresh water: Wetland Fresh water: Wetland systemssystems

Defined as “transitional between terrestrial Defined as “transitional between terrestrial and aquatic systems where the water table and aquatic systems where the water table is at or near the surface or land is covered is at or near the surface or land is covered by shallow water”by shallow water”

Cover about 6% of earth, but Cover about 6% of earth, but disproportionate amount of benefits disproportionate amount of benefits (hunting, fishing, trapping, timber, water, (hunting, fishing, trapping, timber, water, agriculture)agriculture)

Disproportionate amount of threatened and Disproportionate amount of threatened and endangered spp are wetland dependent endangered spp are wetland dependent

Conservation challenges: Conservation challenges: freshwater systemsfreshwater systems

Affected by:Affected by: Physical alteration (dams, channels, Physical alteration (dams, channels,

developmentdevelopment Chemical alteration: nutrients, Chemical alteration: nutrients,

pollutionpollution Introduction of exotic organismsIntroduction of exotic organisms

FutureFuture

Improve productivity of water useImprove productivity of water use Change our goal from use of water Change our goal from use of water

to improved social and individual to improved social and individual well-being per unit of water usedwell-being per unit of water used

This means using market and This means using market and regulations to cause change.regulations to cause change.

Eutrophication: Effects of Eutrophication: Effects of nutrientsnutrients

Most important nutrient: phosphorusMost important nutrient: phosphorus Chain reaction: Chain reaction: Increase in biomass of attached algae & Increase in biomass of attached algae &

submersed macrophytes, they then decrease as submersed macrophytes, they then decrease as blue green algae and phytoplankton increase blue green algae and phytoplankton increase and block light. Dead organisms use oxygen, and block light. Dead organisms use oxygen, result in fish kills, but minnows and carp increase result in fish kills, but minnows and carp increase initially, reducing zooplankton, which causes initially, reducing zooplankton, which causes increase in phytoplankton, further reducing light. increase in phytoplankton, further reducing light.

Result: biological community altered, water quality Result: biological community altered, water quality declines (less valuable for drinking, recreation declines (less valuable for drinking, recreation and food) and food)

AcidificationAcidification Lower pH results in lower reproduction by Lower pH results in lower reproduction by

fishes, amphibians & aquatic invertebrates, fishes, amphibians & aquatic invertebrates, also direct mortalityalso direct mortality

Lower pH causes changes in ions, esp. Al, Pb, Lower pH causes changes in ions, esp. Al, Pb, and Cd. They precipitate out at low pHs. Al and Cd. They precipitate out at low pHs. Al can bind to gills of fish killing them.can bind to gills of fish killing them.

Al can bind to P as it precipitates, making it Al can bind to P as it precipitates, making it less available as a nutrient for organisms.less available as a nutrient for organisms.

Lower fish population can result in increase Lower fish population can result in increase in invertebrate population released from in invertebrate population released from predation.predation.

Marine ecosystemsMarine ecosystems

Coral ReefsCoral Reefs: combine elements of : combine elements of structure, nutrients (esp. Ca), water quality structure, nutrients (esp. Ca), water quality and light to create favourable environment and light to create favourable environment for lifefor life

Hydrothermal ventsHydrothermal vents: unique environment : unique environment and life forms (some very ancient)and life forms (some very ancient)

Benthic (sea bottom) communitiesBenthic (sea bottom) communities: : sediment grain size related directly to sediment grain size related directly to diversity of organisms, structure in soft diversity of organisms, structure in soft sediments important for diversity of life.sediments important for diversity of life.

Causes of marine habitat Causes of marine habitat degradationdegradation

Physical structure change:Physical structure change: Use of dynamite on coral reefsUse of dynamite on coral reefs Bottom trawling nets: more complex Bottom trawling nets: more complex

habitat is more severely affected.habitat is more severely affected. Mariculture, land developmentMariculture, land development Land events: sedimentationLand events: sedimentation

Causes of marine habitat Causes of marine habitat degradationdegradation

ChemicalChemical EutrophicationEutrophication Pollutants, pesticides, radioactive wastePollutants, pesticides, radioactive waste Mariculture, some changes direct: waste, Mariculture, some changes direct: waste,

disease; others indirect: genetic (out disease; others indirect: genetic (out breeding depression of escaped farmed breeding depression of escaped farmed salmon), change in predator population: salmon), change in predator population: sea star and mussel cultivation)sea star and mussel cultivation)

Human caused changes in Human caused changes in populationpopulation

Over harvest: directOver harvest: direct Over harvest indirect: affect on Over harvest indirect: affect on

other organisms when foundation other organisms when foundation spp reduced drastically: e.g. sea spp reduced drastically: e.g. sea otterotter

Trophic effects and Trophic effects and interconnections new area of studyinterconnections new area of study

PastPast

Seas were common property, Seas were common property, countries competed for fish countries competed for fish thousands of miles from homethousands of miles from home

1982 UN adopted Convention on 1982 UN adopted Convention on the Law of the Sea, allowing coastal the Law of the Sea, allowing coastal countries to claim 200 nautical mile countries to claim 200 nautical mile exclusive economic zone, included exclusive economic zone, included most continental shelvesmost continental shelves

PastPast This placed responsibility of control on This placed responsibility of control on

coastal country.coastal country. Most used subsidies to grow fishing industryMost used subsidies to grow fishing industry Convention called for allowing other Convention called for allowing other

countries access to resources not used by countries access to resources not used by local country: resulted in push by local local country: resulted in push by local countries to use all available fish resourcescountries to use all available fish resources

Over fishing warnings did not occur because Over fishing warnings did not occur because we did not understand threshold effects, we did not understand threshold effects, poor population modelling, cheating on poor population modelling, cheating on regulations and lying on fish catch statisticsregulations and lying on fish catch statistics

Recent problemsRecent problems

Fishing down the food webFishing down the food web Table fish (cod, snapper, tuna) usually Table fish (cod, snapper, tuna) usually

feed on small pelagic fish (herring, feed on small pelagic fish (herring, anchovies, sardines) (trophic level anchovies, sardines) (trophic level 3.5-4.5)3.5-4.5)

However, very large quantities of However, very large quantities of small pelagic fish (trophic level 3) small pelagic fish (trophic level 3) being caught to provide feed for being caught to provide feed for animals and farmed fishanimals and farmed fish

FutureFuture

Focus on herbivorous fish for farming: Focus on herbivorous fish for farming: tilapia, mussels, clamstilapia, mussels, clams

Ecosystem based management like in Ecosystem based management like in forestry: understand resilience and forestry: understand resilience and resistance: phase out fishing gear that resistance: phase out fishing gear that destroys habitat, implement marine destroys habitat, implement marine reserves, abolish subsidies, enforce reserves, abolish subsidies, enforce gear used to reduce by-catch, reduce gear used to reduce by-catch, reduce fishing fleet fishing fleet