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AQUATIC ECOSYSTEMS CHAPTER 7. ocean. freshwater. saltwater. plankton. nekton. benthos. upwelling. swamps. wetland. littoral zone. benthic zone. estuary. lake. algal bloom. river. salt marsh. B a r r i e r I s l a n d. eutrophication. coral reef. salinity. - PowerPoint PPT Presentation
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estuary
upwelling
salt marsh
wetland
benthos
B a r r i e r I s l a n d
plankton
swamps
nekton
lake benthic zone
saltwater
littoral zone
eutrophication
freshwater
algal bloom
coral reef
ocean
salinity
river
AQUATIC ECOSYSTEMS
CHAPTER 7
Freshwater Ecosystems
...determine where Org livesin the water.
• Temp
• Sunlight
• O2
• Nutrients
TYPES of ORGS
• Plankton (phyto - & zoo -)– Float near surface– Principal food source in aquatic ecosystems
• Nekton– Free-swimming orgs: fish, turtles, whales...
• Benthos– Bottom-dwellers: mussels, worms, barnacles...
TYPES of FW Ecosystems
• Lakes
• Ponds
• Wetlands
• Rivers
• Streams
LIFE in a LAKE...
• LITTORAL ZONE– Near shore– Nutrient-rich– Abundant/diverse life
due to sunlight (photosynthesis)
• BENTHIC ZONE– Lake bottom – no light
for photosynthesis– Dead & decaying orgs– Decomposers, insect
larvae, clams...carp.
...depends on the amount of sunlight available!
Eutrophication• “Increase in amount of nutrients in
aquatic ecosystem.”
• Nutrients cause plants & algae to increase...
• Bacteria increase as dead plant matter grows...bacteria use up dissolved O2...
• O2 - loving organisms die off.
• Lakes naturally become eutrophic over time....
...but the process can be accelerated by sewer system or agricultural runoff that places fertilizer (and I use the term loosely!) into lakes & ponds.
FW WETLANDS
• “Areas of land periodically covered with water.”
• MARSHES: contain non-woody plants (cattails, reeds, rushes)
• SWAMPS: woody plants (trees, shrubs)
Marshes• Characterized by low, flat land...little
water movement...some “brackish,” some saltier.
• Flat-billed fowl (ducks, grebes) adapted for skimming insects off surface; those with spear-like beaks (herons) suited to grasping small fish & digging for buried frogs.
• Florida Everglades: largest freshwater wetland in U.S.
Swamps
• Flat, poorly drained land; woody shrubs or water-loving trees.
• Snakes...bullfrogs...alligators!
Freshwater WETLANDS provide important environmental functions:
• Act as filters or sponges to absorb & remove pollutants from groundwater; improve water quality of lakes/reservoirs downstream.
• Control flooding by absorbing extra water from rivers & hurricane storm surges...saving urban/residential areas from damage.
• Habitat for migratory waterfowl...spawning grounds for game fish...cranberries!
• Buffer zones to protect against shoreline erosion.
...they used to be wastelands...
• For decades, it was believed they were just breeding grounds for mosquitoes...
• Millions of acres were “recovered” via drainage, filling in, clearing...
• Now (thanks to envi sci!) they are protected by government...their destruction is prohibited.
Rivers• Rivers have been long used as free water
sources for industry (and dumping grounds...)
• Toxins have killed off much river life and made river fish inedible...city & farm runoff put pesticides & other poisons in rivers.
• Dams alter ecosystems in and around rivers.
Marine Ecosystems
Estuaries• “Freshwater source (river) mixes with
saltwater source (ocean).”
• Currents cause nutrient trap to form @ bottom. Sunlight penetrates shallow waters.
• Rich nutrients/photosynthesis make estuaries some of the most biologically productive ecosystems on the planet.
• Protected from waves by peninsula/barrier islands.
Estuary Life
• Plants & plankton fish dolphins, manatees, seals et al...abundant food web.
• Oysters, barnacles, clams (filter feeders)
• Orgs are able to tolerate varying salinity
• Humans love estuaries too...
Threats to Estuaries
• Of the 10 largest urban areas on the planet, 6 are built on estuaries: – Tokyo– New York City– Shanghai– Buenos Aires– Rio de Janeiro– Bombay
Threats to Estuaries
• California: estuaries filled in with waste & used as building sites.
• Rivers carry pollutants downstream to estuary (sewage, ag waste, pesticides, toxic chemicals)
Chesapeake Bay
Barrier Islands
• Formed by rising sea levels (over the past 15,000 years)
• Long, narrow sand ridges parallel to coastline, 3 to 30 km out.
• Protect mainland & coastal wetlands from storms & waves.
• ...don’t spend a lot of $ buying a home on ‘em...
Sanibel Island
Southern Rhode Island
Coral Reefs
• Limestone ridges built by photosynthetic algae & skeletons of coral polyps.
• Found only in clear, warm, shallow saltwater.
• Among the most diverse ecosystems on planet (thousands of species).
• Convoluted shape provides habitats for fish, snails, clams, sponges...
Coral Reefs
• 27% of world’s coral reefs in danger...
• Oil spills...sewage...pesticides...silt runoff...overfishing...– If water gets too warm/too cold...– If fresh water drains onto reef...– If water gets too muddy/polluted...
• Reefs are fragile, they grow too slowly to repair themselves in time...
Great Barrier Reef
Oceans
• “Usable” sunlight penetrates to only 100 m depth...
• ...most ocean life thus located in shallow coastal areas, not in open oceans.– Seaweed, algae, plankton...inverts & fish that
feed on them are concentrated near-shore.
• Many different “minisystems” exist...
• Open oceans are possibly the least productive of all ecosystems.
UPWELLING
• @ coastlines: surface currents carry water away from shore...
• Deeper, nutrient rich bottom water “wells up”to fill in...
• Phytoplankton love it...fish come for phytoplankton...humans come for fish...it’s all good?
Threats to Oceans
• Fertilizer runoff from shore causes algal bloom...some are poisonous!
• Industrial waste & sewage = coastal pollution.
• Overfishing is destroying some fish populations...
• Stupid fishing methods are murdering innocent creatures...