Transcript Aquatic Ecosystems Section 1

Aquatic Ecosystems
Section 1
Objectives
• Describe the factors that determine where an organism
lives in an aquatic ecosystem.
• Describe the littoral zone and the benthic zone that
make up a lake or pond.
• Describe two environmental functions of wetlands.
• Describe one threat against river ecosystems.
Aquatic Ecosystems
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Freshwater Ecosystems
• ponds, lakes, streams, rivers, and wetlands.
• wetlands - areas of land that are periodically under
water or whose soil contains a great deal of moisture.
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Characteristics of Aquatic Ecosystems
• temperature, sunlight, oxygen, and nutrients determine
organisms
• organisms grouped by location and adaptations.
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Groups
• Plankton - mass of mostly microscopic organisms that
float or drift freely in the water, include zooplankton
phytoplankton.
• Nekton - swim actively in open water
• Benthos - bottom-dwelling organisms, often attached to
hard surfaces.
Aquatic Ecosystems
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Lakes, Ponds
• lakes, ponds, form naturally where groundwater reaches
the Earth’s surface.
• artificial lakes used for power, irrigation, water storage,
and recreation.
• structured into horizontal and vertical zones that depend
on the amount of sunlight available.
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Life in a Lake
• littoral zone - shallow zone with light, plant and aquatic
life diverse and abundant.
• some plants rooted in the mud with upper leaves,
stems above water or floating leaves.
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Life in a Lake
• deep areas have to little light for photosynthesis.
• bacteria, fish adapted to cooler, darker water
• benthic zone - region near the bottom of a pond, lake or
ocean inhabited by decomposers, insect larvae, and
clams.
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Life in a Lake
• in regions where lakes partially amphibians burrow into
the littoral mud to avoid freezing
Aquatic Ecosystems
A Lake Ecosystem
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Aquatic Ecosystems
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How Nutrients Affect Lakes
• Eutrophication - increase amount of nutrients, such as
nitrates, in an aquatic ecosystem.
• amount of plants and algae grow, so the number of
bacteria feeding decaying organisms grows.
– use the oxygen reducing amount
– kills oxygen loving organisms.
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How Nutrients Affect Lakes
• lake with large amounts of plant growth eutrophic
• naturally become eutrophic over time
• eutrophication can be accelerated by runoff, that can
carry sewage, fertilizers, or animal wastes into water
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Freshwater Wetlands
• areas of land covered with fresh water for part of the
year.
• two main types
– marshes contain nonwoody plants
– swamps dominated by woody plants.
• most freshwater wetlands located in the southeastern
United States, largest (Florida Everglades).
Aquatic Ecosystems
Freshwater Wetlands
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Aquatic Ecosystems
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Freshwater Wetlands
• perform several important environmental functions.
– act like filters or sponges that absorb and remove
pollutants from the water.
– control flooding by absorbing extra water when rivers
overflow.
– provide a home for native and migratory wildlife
– feeding, spawning area for many freshwater game
fish.
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Marshes
• occur on low, flat lands with little water movement.
• plant roots in sediments, leaves out on surface of the
water year-round.
• Marshes characterized salinity.
– brackish: slightly salty
– salt marshes: saltier water.
Aquatic Ecosystems
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Marshes
• benthic zones nutrient rich with plants, decomposers,
and scavengers.
– water fowl, birds - adapted for fish and insects
– migratory birds from temperate and tropical habitats.
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Swamps
• occur on flat, poorly drained land
• often near streams dominated by woody shrubs, water
loving trees
• ideal habitat for amphibians
•
birds attracted to hollow trees near or over the water
• reptiles are the predators
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Human Impact on Wetlands
• previously considered wastelands, breeding grounds for
insects.
– many drained, filled, and cleared for development
laws now protect many wetlands
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Rivers
• at headwaters- usually cold, full of oxygen, runs swiftly
through shallow riverbed
• as flows down (mountain), may broaden, become
warmer, wider, slower, decrease in oxygen.
• change with the land and climate through which it flows
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Life in a River
• near the headwater, mosses anchor to rocks
– trout, minnows adapted to the cold, oxygen rich
water
• farther downstream, plankton float in the warmer, calmer
waters.
– plants set roots in sediment
– catfish and carp live in these calmer waters.
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Rivers in Danger
• Industries use river water in manufacturing processes,
for waste disposal
• used to dispose sewage and garbage.
– polluted rivers with toxins, made river fish inedible.
• runoff from the land puts pesticides, poisons into rivers
and coats riverbeds with toxic sediments.