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 Section 1

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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• temperature, sunlight, oxygen, and nutrients determine organisms

• organisms grouped by location and adaptations.

Characteristics of Aquatic Ecosystems

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• 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.

Groups

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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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• 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.

Life in a Lake

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• in regions where lakes partially amphibians burrow into the littoral mud to avoid freezing

Life in a Lake

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A Lake Ecosystem

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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).

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Freshwater Wetlands

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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.

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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.