Lesson 6.3 Aquatic Ecosystems

75% of Earth’s surface is covered by water.

What are the basic needs of aquatic life?

• CO2

• O2

• Sunlight• Nutrients- food &

minerals

Describing Aquatic Ecosystems

•Salinity: • Amount of dissolved salt present in

water

• Salt water, fresh water, or brackish

•Photosynthesis:• Light availability

• Depth & water clarity

• Flowing or standing water

• Zones: photic, aphotic, benthic

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

Freshwater Ecosystems

• Usually 0.005% salt– Some exceptions:

• Great Salt Lakes-

5-27% salt• Dead Sea- 30% salt

• Moving water- high elevations; cold; high O2; trout; streamlined plants

• Standing water- lower elevations; warmer; less O2; bass, amphibians; cattails, rushes

Freshwater Ecosystems: Ponds, Lakes, Inland Seas

•Horizontal zones: littoral and limnetic

How is a lake stratified and what lives in each level?

• Epilimnion- upper layer of warm water; high light & O2; ex: water striders, phyto- & zooplankton, fish

• Thermocline (mesolimnion); middle layer; medium light & O2; ex: phyto- & zooplankton, fish

• Hypolimnion- lower layer of cold water; lower light & O2; ex: fish

• Benthos- bottom level; no light & little O2; ex: anaerobic bacteria, leeches; insect larvae

• Littoral- near the shoreline; cattails, rushes, amphibians, etc.

Freshwater Ecosystems: Wetlands

Lesson 6.3 Aquatic Ecosystems

• Areas of land flooded with water at least part of the year

• Marshes, swamps, bogs, and fens

• Prevent flooding, recharge aquifers, filter pollutants, and provide habitats.

Freshwater Ecosystems: Rivers and Streams

Lesson 6.3 Aquatic Ecosystems

• Bodies of surface water that flow downhill, eventually reaching an ocean or inland sea

• Watershed: area of land drained by a river and its tributaries

• Characteristics, such as dissolved oxygen, temperature, water speed, organisms, and others, change from source to mouth.

Estuaries• Where river flows into the ocean or an

inland sea

• Prevent flooding and soil erosion as well as provide habitats.

• Coastal estuaries

• brackish; organisms must tolerate wide salinity and temperature ranges

• home to salt marshes & mangrove forests

Did You Know? Salt marshes and mangrove forests are two of the most productive ecosystems on Earth.

Did You Know? Salt marshes and mangrove forests are two of the most productive ecosystems on Earth.

Everglades, Florida, wetlands

OceansLesson 6.3 Aquatic Ecosystems

• Currents are driven by water temperature and density differences, wind, and gravity.

• Surface winds and heating generate vertical currents that transport nutrients and oxygen.

Did You Know? If the water in the oceans evaporated, a 60 m (200 ft) deep layer of salt would be left behind.

Did You Know? If the water in the oceans evaporated, a 60 m (200 ft) deep layer of salt would be left behind.

• Horizontal ocean zones: intertidal, neritic, open ocean

• Vertical ocean zones: photic, aphotic, benthic

Ocean Ecosystems• Intertidal: Highly diverse; extreme range of temperature,

moisture, and salinity

• Neritic: Productive kelp forests and coral reefs provide habitats and help protect shorelines from erosion.

Did You Know? Over 90% of ocean water on Earth is in the open ocean zone.

Did You Know? Over 90% of ocean water on Earth is in the open ocean zone.

• Open ocean: Low productivity due to low light penetration; phytoplankton base of food chain; deep sea organisms and hydrothermal vent communities

What factors influence the availability of those basic needs?

• Substances dissolved in water- Nitrates, phosphates, potassium, O2

• Suspended matter- (silt, algae) can affect light penetration

• Depth• Temperature• Rate of flow• Bottom characteristics (muddy,

sandy, or rocky)• Internal convection currents• Connection to or isolation from

other aquatic ecosystems.

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

Marsh

Swamp

Importance of Wetlands• Highly productive- get lots of

sunlight, ↑ plants =↑ animals

• Nesting, breeding ground for migratory birds

• Slows flooding by absorbing runoff• Silt settles, making water clearer &

nutrient rich• Trap & filter water• Natural chemical rxns neutralize

and detoxify pollutants• Gives H2O time to percolate thru

soil & replenish underground aquifers.

• Threats- artificial eutrophication (see slide 13), draining, sedimentation via construction

• “Nature’s Septic Tank”

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 Ecosystems

• BARRIER ISLANDS• Low, narrow offshore

islands• Protect inland shores

from storms• Beauty attracts

developers = developers destroy land

• New coastal zoning laws protect future development

MARINE ECOSYSTEMS

• CORAL REEFS• Clear, warm shallow seas• Made up of accumulated

calcareous (made of calcium) skeletons of coral animals

• Formation depends on light penetration.

• Have a symbiotic relationship with algae

• Very diverse, abundant (rainforests of sea)

• Threats- destructive fishing (cyanide & dynamite to stun fish), pet trade; about 3/4ths have been destroyed

What factors can alter aquatic ecosystems?

• Natural Succession- normal cycle of pond becoming forest

• Artificial Succession- humans add N & P to water via fertilizer & sewage causing succession to happen faster = EUTROPHICATION

What factors can alter aquatic ecosystems?

• Humans!– Find food– Recreation– Waste disposal– Cooling of power

plants– Transportation– Dams, canals