Most of the Earth Is Covered with Water• Aquatic life zones

– Saltwater: marine • Oceans and estuaries• Coastlands and shorelines• Coral reefs• Mangrove forests

– Freshwater• Lakes• Rivers and streams• Inland wetlands

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Two Major types of Aquatic Zones• The world’s salt water and freshwater

aquatic system accounts for 71% of the earth’s surface.

• Scarcity of Water

But Not a Drop to Drink

Aquatic Ecosystems

• Aquatic ecosystems are defined by their salinity, chemistry, geography, depth, flow, light conditions, and water temperature.

• The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems

• Each ecosystem has its own properties and organisms.

How much water is there?

Marine and freshwater biomes contain many different types of habitats, from forest bogs to

abyssal zones in the deep oceans.

Freshwater Communitiesponds and lakes

• Littoral zone are shallow zones near the shore- aquatic plants live along various predatory insects, amphibians and small fish.

• Limnetic zone refers to the area farthest away from shore but at the surface- floating algae, zooplankton and fish

• Profundal zone is a deep-water zone that is below the limits of effective light penetration- bacteria and worm-like organisms eat debris on lakes bottom

• Flowing-water ecosystems- Rivers and streams: organisms are adapted to seasonal change in water levels and rate of flow. Many have adaptations that help them avoid being washed downstream.

• Wetland communities- swamps, marshes, bogs, and other communities- very productive

Wetland communities

Marsh

Bogs in TundraWetlands

Salinity

• Seawater contains a variety of dissolved solids– Solutes

• Salinity is measured:– Conductivity of Cl-

– Refractometer

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How Salinity Affects Marine Organisms

• Most marine animals are adapted to a narrow salinity range• Changes is salinity affect organisms through osmosis

• Hypertonic: water will flow into it across a semipermeable membrane

• Hypotonic: water will leave the solution

Varying salinities determine the

distribution and abundance of

aquatic organisms around the world

How pH Affects Marine Organisms

pH is one of the stable measurements in

seawater. Ocean water has an excellent

buffering system with the interaction of

carbon dioxide and water so that it is

generally always at a pH of 7.5 to 8.5.

• Shallow Ocean Water communities- small area but it is inhabited by a large number of species.

• Fish are sensitive to changes in pH and would experience a decrease in numbers if a shift in the pH of the water occurred. – Intertidal- adapted to change in temperature, salinity

and exposure to air during the tidal changes. Adapted to cling to rocks

– Coral reef community- most diverse occurs in shallow tropic waters

– Coastal zones of cooler waters – the world’s greatest fisheries

Estuaries and Coastal Wetlands Are Highly Productive

• Important ecological and economic services– Coastal aquatic systems maintain water quality by

filtering• Toxic pollutants• Excess plant nutrients• Sediments

– Absorb other pollutants – Provide food, timber, fuelwood, and habitats– Reduce storm damage and coast erosion

Coastal Zone

• The coastal zone makes up less than 10% of the world’s ocean but contains 90% of all marine species.

• Warm, nutrient rich, shallow water • Extends from high tide mark to edge of the

continental shelf• High productivity because of ample sunlight

and plant nutrients flowing from the land

Coastal Ecosystems • Estuaries- where the river meets the sea.

– Temperature and salinity levels vary greatly • daily rhythms of the tides • seasonal variations in the flow of freshwater

• Coastal wetlands lands covered with water all or part of the year– River mouths, inlets, bays, sounds, mangroves and saltwater

marshes

• Mangrove Swamps trees that can tolerate salt – Extensive roots that stabilize the substrate– Provides a nursery grounds for many invertebrates and fish

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Mangroves

Coral reefs

Reefs, and Mangroves

Communities at the surface of the Open Sea

• Diverse community of plankton (bacteria, algae, fish larvae, and small invertebrates)• Phytoplankton are primary producers

that rely on the sun to carry out photosynthesis.

• Zooplankton are a major source of food for small and large marine organisms

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The Great Plankton Race!

The Secret Life of Plankton

Diatom

Open Ocean• Water beyond the continental shelf• Light zones: Euphotic, Disphotic, Aphotic• Depth Zones: epipelagic, mesopelagic,

bathypelagic, abyssolpelagic, hadalpelagic• Average primary productivity and NPP per

unit of area are quite low except at an upwelling

• Upwelling- where currents bring nutrients from the bottom to the surface where there is light

High tideLow tide

Coastal Zone

EstuarineZone

Continentalshelf

Open Ocean ZoneSea level

Sun

Epipelagic Zone

Bathyal Zone

Abyssal Zone

Depth inmeters

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50

100

200

Eu

ph

oti

c

500

1,000

1,500

2,000

3,000

4,000

5,000

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Ap

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Ocean Zones© 2004 Brooks/Cole – Thomson Learning

Benthic Division

Pelagic Division

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Three layers of aquatic life zones • Euphotic zone-photosynthesis occurs

– Dissolved oxygen high in the surface layer

– CO2 levels are low

Disphotic zone- some light but not enough for photosynthesis “twilight zone”

Aphotic Zone- No light - Lower levels of oxygen - No photosynthesis - CO2 levels are high due to anaerobic

respiration.

Light Absorption in the Ocean

• Total darkness, cold and under great amounts of pressure.

• Diverse community of invertebrates and fishes.

• Hydrothermal Vents- community that relies on bacteria that chemosynthesis

• Some rely on Bioluminescence

Communities at the ocean depths

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What kinds of organisms live in Aquatic Zones?

• Plankton- drifters/floaters can not swim against a current include Phytoplankton, zooplankton to large jellyfish.

• Nekton- swimmers include fish, turtles, and whales• Benthos- live in/on the bottom includes most

invertebrates • Decomposers-break down the organic compounds

in the dead bodies and wastes of aquatic organisms into simple nutrients compounds for use by producers includes bacteria and Fungi.

• Key factors in the distribution of organisms– Temperature– Dissolved oxygen content– Availability of food– Availability of light and nutrients needed for

photosynthesis in the euphotic, or photic, zone

Temperature• At lower latitudes there is a capture of heat and at

higher latitudes there is a loss of heat– This creates a temperature gradient for surface waters– Surface waters will fluctuate wildly at the mid-

latitudes and almost remain constant at the poles and equator

How do these guys

differ?

Ocean surface temperature strongly correlates with latitude.

• Isotherms (lines of equal temperature) generally trend east-west except where deflected by currents.

• Ocean currents carry warm water poleward on the western side of ocean basins and cooler water equatorward on the eastern side of the ocean.

• Insolation and ocean-surface water temperature vary with the season.

• Ocean temperature is highest in the tropics (25oC) and decreases poleward.

Insolation = amount of light striking Earth

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Dissolved Oxygen (DO) Content

• Amount of oxygen gas dissolved in a given volume of water at a particular temperature and pressure.– Limiting factor of

aquatic ecosystem

• Dissolved inorganic carbon in the oceans is 50 – 60 x greater than in the atmosphere

• A small change in the ocean carbon cycle can result in a substantial change in the concentration of CO2 in the atmosphere

• Solubility of CO2 increases with decreasing temperature solubility pump transfers CO2 to the deep sea during formation of cold deep water at high latitudes. (Link to physical process part of circulation)

• At the same time, the biological pump removes carbon from surface waters by settling of organic and inorganic carbon derived from biological production in the deep sea (link to biological process)