Aquatic Ecosystems. Characteristics of Aquatic Ecosystems Fundamental Division: freshwater vs. saltwater –Salinity=amount of dissolved salts in water(*limiting

Aquatic EcosystemsAquatic Ecosystems

Characteristics of Aquatic Characteristics of Aquatic EcosystemsEcosystems

• Fundamental Division: freshwater vs. saltwater– Salinity=amount of dissolved salts in water(*limiting

factor which restricts population growth, distribution, or abundance of an organism

• Dissolved oxygen• Light penetration• Temperature• pH• Presence/absence of currents/waves

Three Main Categories of Three Main Categories of OrganismsOrganisms

• Plankton

• Nekton

• Benthos

PlanktonPlankton

• Free-floating

• Small, microscopic

• At the mercy of the current (feeble swimmers)

• Daily vertical migration

PlanktonPlankton

• 2 major categories– Phytoplankton-photosynthetic, algae,

cyanobacteria (blue-green algae)• Producers that form the base of the food chain

– Zooplankton-non-photosynthetic, include protozoa, tiny crustaceans, larval forms of many organisms, feed on phytoplankton, eaten by newly hatched fish/small organisms

• PhytoplanktonZooplankton

NektonNekton

• Larger, stronger swimmers

• Fish, turtles, whales

BenthosBenthos

• Bottom dwellers– Fixed in place (coral, sponges, barnacles)– Burrow in sand (worms, clams)– Walk on bottom (crayfish, brittle stars)

BenthosBenthos

Freshwater EcosystemsFreshwater Ecosystems

• Rivers and Streams

• Lakes and Ponds

• Wetlands

• Estuaries

Rivers and Streams (flowing water)Rivers and Streams (flowing water)

• Conditions vary from source (where it begins) to its mouth (the body of water it empties into)– Headwater streams– Downstream

Headwater Streams CharacteristicsHeadwater Streams Characteristics

• Cold, fast-moving, shallow, highly oxygenated

• Blackfly larva (suckers to adhere to rocks), water-penny (flat to fit under rocks), and brown trout (muscular, streamlined bodies to swim against current)

• 99% of energy comes from detritus, leaves and debris that falls into water

Headwater StreamHeadwater Stream

Black Fly Larva and Water PennyBlack Fly Larva and Water Penny

Downstream CharacteristicsDownstream Characteristics

• Wider, slower current, cloudy because suspended particles begin to fall out, deeper, less oxygenated

• Groundwater upwellings that moderate temperature

• Organisms are similar to lake/pond

• Depend less on detritus because more photosynthesis occurs here

DownstreamDownstream

Human Impact on Moving WaterHuman Impact on Moving Water

• Pollution-dumping raw sewage, PCB’s, mercury, lead, animal waste, medical waste

• Dams-upstream flooding damages terrestrial habitats; downstream becomes only a trickle of water damaging stream ecosystem

• Thermal pollution-water is used to cool factory machinery and then released back into the river increasing temperature and killing some organisms

Lakes and Ponds (limnology is the Lakes and Ponds (limnology is the study of freshwater lakes)study of freshwater lakes)

• Three zones– Littoral zone– Limnetic zone– Profundal zone

Littoral ZoneLittoral Zone

• Shallow water near shore with emergent vegetation (cattails, reeds, etc)

• **most productive because most photosynthesis occurs here and nutrients from the surrounding area “fall into” the shallow water

• Wildlife-fish, frogs, tadpoles, turtles, crayfish, insect larvae, bass, carp, perch

Littoral ZoneLittoral Zone

Limnetic ZoneLimnetic Zone

• Open water away from shore

• Extends to where sunlight penetrates

• Main organisms are plankton

• Larger fish species

Profundal Zone (only large lakes)Profundal Zone (only large lakes)

• Deepest zone, no algae, no light

• Anaerobic bacteria because no oxygen

• Mineral rich because decomposed organic nutrients are not absorbed by producers to enter the food web

Lake ZonationLake Zonation

Lake ZonationLake Zonation

Seasonal Thermal StratificationSeasonal Thermal Stratification

• Temperature changes sharply with depth (where sunlight penetrates)

• Summer: surface water heats up (becomes less dense) and deeper water is cooler so is more dense, creating a thermocline (temperature transition), more dissolved O2 at cooler depths affecting fish distribution

Summer StratificationSummer Stratification


• Fall: falling temperatures cause a mixing of the water layers known as fall turnover.– Surface water cools becomes more dense,

sinks and displaces warmer water underneath– This happens until a uniform temp. is reached


• Winter: surface water cools below 4oC (greatest density of water) and ice (0oC) forms at the surface, creating another thermocline

Seasonal Thermal StratificationSeasonal Thermal Stratification• Spring Turnover: occurs as ice melts, temp.

of water increases to 4oC at which time it sinks down (greatest density)

• Layers mix until a uniform temperature is reached

• ***turnovers (fall and spring) are really important because the cycle nutrients and oxygenated water, algal bloom usually follows

Lake LayersLake Layers

• Seasonal stratification:– Epilimnion (on top of thermocline)– Hypolimnion-below the thermocline (where

nutrients and oxygen are)

Lake through SeasonsLake through Seasons

Lake TypesLake Types

• Oligotrophic-newly formed, nutrient poor, liitle life, very clear

• Eutrophic-older lakes with high nitrates and phosphates, a lot of plant life, usually murky

• Mesotrophic-in between stages



• Meromictic Lake-very deep, doesn’t turn over so nutrients don’t cycle, not a lot of life

Freshwater WetlandsFreshwater Wetlands

• Covered by shallow water at least part of the year

• Soils are waterlogged and anaerobic• Soils are rich in organic matter (little to no

decomposition)• Marshes-grasslike/plants dominant• Swamps-woody trees and shrubs• Animals found:migratory birds, beavers, otters,

muskrat, fish


• Ecological Benefits– Help control flooding by holding excess water

(Hurricane Katrina)– Most important role is to cleanse and purify

water by trapping and holding pollutants– Now protected by laws


EstuariesEstuaries

• Where saltwater and freshwater mix (usually at river mouths)

• Water fluctuates with tides

• Salinity fluctuates with tidal cycles, time of year, precipitation, and gradual changes from river to ocean

• Among the most fertile ecosystems

Estuary ProductivityEstuary Productivity

• Nutrients are transported from land and streams that flow into the river

• Tidal action circulates nutrients and removes wastes

• Shallow; high level of light penetration

• Plants photosynthesize and trap detritus

• Nurseries for fish and shellfish (blue crab, shrimp)

Types of EstuariesTypes of Estuaries

• Temperate estuaries-salt marshes

• Tropical-mangroves– Nesting sites for pelicans, egrets, heron– Mangrove roots stabilize soil, prevent erosion,

and provide a barrier against oceans during storms

Estuary From SpaceEstuary From Space

MangroveMangrove

Marine EcosystemsMarine Ecosystems

• Average depth 2.2 miles and some trenches up to 7 miles

• Tides and currents; gravitational pulls of the sun and moon produces 2 high tides and 2 low tides a day

• Height of tide varies with season, topography, phase of moon (full=highest)

• Divided into life zones

Marine EcosystemsMarine Ecosystems

• Life Zones:– Intertidal– Benthic– Euphotic– Bathyal– Abyssal

Intertidal ZoneIntertidal Zone

• Shoreline between high tide and low tide

• Highly productive (increased light, nutrients, oxygen), but stressful– Sandy: constantly shifting ground, engulfed by

sand– Rocky: exposed to submersion-high tide,

exposed to air-low tide, inhabitants usually have an anchor and a way of sealing moisture in

Intertidal ZoneIntertidal Zone

Benthic ZoneBenthic Zone

• Ocean floor-sand and mud

• Clams, worms, bacteria

• Bottom dwellers

Euphotic ZoneEuphotic Zone

• Supports photosynthesis of phytoplankton

• Low nutrient levels

• High levels of dissolved oxygen

• Large, fast swimming predators: swordfish, sharks, blue fin tuna

Euphotic ZoneEuphotic Zone

Bathyal ZoneBathyal Zone

• Dimly lit middle zone with no photosynthesis

• Organisms are adapted to darkness and scarcity of food; ex. Dragonfish has a red light under its eyes to detect prey

• Zooplankton migrate here during the day

• Giant squid, gulper eel, angler fish

Bathyal ZoneBathyal Zone

Abyssal ZoneAbyssal Zone

• Extends from 2.5-3.7 miles (4000-6000 m)

• Little dissolved oxygen

• Cold and dark

• Hydrothermal vents: sulfur chemosynthetic bacteria, blood red tube worms, clams, mussels, barnacles feed on bacteria that can reproduce at very high temperatures

Hydrothermal VentHydrothermal Vent

Shallow Marine EcosystemsShallow Marine Ecosystems

• Sea grasses/flowering plants adapted to complete immersion (turtle grass, manatee grass)

• Turtles, temperate manatees, wading birds, ducks, geese

Kelp EcosystemsKelp Ecosystems

• Largest brown algae, can reach a length of approximately 200 ft.

• Found in cooler water temps.

• Photosynthetic

• Habitat for tubeworms, sponges, sea cucumbers, clams, crabs, fish, sea otters, sea urchins

Kelp EcosystemsKelp Ecosystems

Coral ReefsCoral Reefs

• Coral is a symbiotic relationship with photosynthetic algae (zooxanthellae) and polyps (related to the jellyfish)

• The polyps secrete layers of calcium carbonate that protects their soft bodies, creating the reef

• Found in warmer water• Living portions must grow where light

penetrates


• Polyps stinging tentacles paralyze zooplankton

• Grow VERY slowly

• Most diverse of all water ecosystems

• Protect shoreline from erosion

• Home to 65% marine fish species although it’s only 1% of the ocean floor

• Supports many fish and tourism industries


• 3 Types of Reefs– Fringing– Atoll– Barrier

Fringing ReefFringing Reef

• Directly attached to the shore

Fringing ReefFringing Reef

AtollAtoll

• Circular reef that surrounds a lagoon

Barrier ReefBarrier Reef

• A lagoon separates this reef from land (Great Barrier Reef=1200 miles)

Human Impacts on Coral ReefsHuman Impacts on Coral Reefs

• Deforestation-more run-off now that isn’t held by tree roots, washing more fresh silt into ocean suffocating the reef

• Sewage• Oil spills• Tourism damages/kills coral• Coral bleaching-algae leave the coral,

leaving them colorless and unable to grow or repair themselves, causing death

Coral BleachingCoral Bleaching

Documents

Aquatic Ecosystems. Characteristics of Aquatic Ecosystems Fundamental Division: freshwater vs. saltwater –Salinity=amount of dissolved salts in water(*limiting