Lesson 6.3 Aquatic Ecosystems

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

What are the basic needs of aquatic life?

• CO 2 • O 2 • Sunlight • Nutrients- food & minerals

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Salinity:

Describing Aquatic Ecosystems

• Amount of dissolved salt present in water • Salt water, fresh water, or brackish •

Photosynthesis:

• • Light availability Depth & water clarity •

Flowing or standing water

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Zones:

photic, aphotic, benthic

Types of Aquatic Ecosystems

• Freshwater Ecosystems –

Standing Water-

lakes & ponds –

Moving Water-

streams rivers & • 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 O 2 ; trout; streamlined plants

Standing water-

lower elevations; warmer; less O 2 ; bass, amphibians; cattails, rushes

Freshwater Ecosystems: Ponds, Lakes, Inland Seas

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Horizontal zones

: littoral and limnetic

• • • • •

How is a lake stratified and what

Epilimnion-

lives in each level?

upper layer of warm water; high light & O 2 ; ex: water striders, phyto- & zooplankton, fish

Thermocline

(mesolimnion); middle layer; medium light & O 2 ; ex: phyto- & zooplankton, fish

Hypolimnion-

lower layer of cold water; lower light & O 2 ; ex: fish

Benthos-

bottom level; no light & little O 2 ; ex: anaerobic bacteria, leeches; insect larvae

Littoral-

near the shoreline; cattails, rushes, amphibians, etc.

Lesson 6.3 Aquatic Ecosystems

Freshwater Ecosystems:

•

Wetlands

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.

Lesson 6.3 Aquatic Ecosystems Freshwater Ecosystems: Rivers and Streams

• 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

Everglades, Florida, wetlands

Did You Know?

Salt marshes and mangrove forests are two of the most productive ecosystems on Earth.

Lesson 6.3 Aquatic Ecosystems

Oceans

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

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

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Horizontal ocean zones:

intertidal, neritic, open ocean •

Vertical ocean zones:

photic, aphotic, benthic Did You Know?

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

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Intertidal:

Ocean Ecosystems

Highly diverse; extreme range of temperature, moisture, and salinity • •

Neritic:

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

Open ocean:

Low productivity due to low light penetration; phytoplankton base of food chain; deep sea organisms and hydrothermal vent communities Did You Know?

Over 90% of ocean water on Earth is in the open ocean zone.

What factors influence the availability of those basic needs?

• Substances dissolved in water Nitrates, phosphates, potassium, O 2 • 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

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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

productivity - may or may not have trees; waterlogged soil with lots of peat; low – Fens- fed by groundwater & surface runoff – Bogs- fed by precipitation Swamp Marsh Bog Fen

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 H aquifers.

2 O time to percolate thru soil & replenish underground Threats- artificial eutrophication (see slide 13), draining, sedimentation via construction “Nature’s Septic Tank”

Marine Ecosystems

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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

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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

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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