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Water Ecosystems. 1.03 Explain why an ecosystem can support a variety of organisms. Temperature and precipitation differ among ecosystems on land. For Earth’s watery ecosystems, the main difference is saltiness.
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Water Ecosystems 1.03 Explain why an ecosystem can support a variety of organisms.
Temperature and precipitation differ among ecosystems on land. For Earth’s watery ecosystems, the main difference is saltiness. • Lakes, streams, rivers, ponds, and certain marshes, swamps, and bogs tend to have little salt in them. They’re all freshwater ecosystems. Oceans and seas are saltwater ecosystems.
In fresh water or salt water, organisms can be divided into three main categories. 1. Plankton - organisms that float on the water. 2. Nekton - organisms that swim through the water. 3. Benthos - are bottom-dwelling organisms.
Plankton • Plankton consist of any drifting organisms (animals, plants, or bacteria) that inhabit the water near the shore. Plankton are defined by their ecological niche. (Niche – The role of an organism in a community.) They provide a crucial source of food to larger, more familiar aquatic organisms such as fish.
Nekton • Nekton - the larger, aquatic, free-swimming animal life having movements that are largely independent of currents and waves, including squids, fishes, and whales.
Benthos • Benthos - all the plants and animals living on or closely associated with the bottom of a body of water, esp. the ocean.
Freshwater Organisms • Many plants live in the shallow waters of lakes, ponds, and other bodies of fresh water. Cattails are tall plants with flat leaves and elongated flowering spikes that grow best when rooted directly in water.
Bur Reeds are marsh inhabiting plants, some growing along the muddy shores of ponds or streams, while other species are strictly aquatic, growing in the water with floating leaves. Wild rice has long, dark brown or black, nutty-flavored seeds and live near water or marshes. Wild rice is not actually a rice but a cereal grain.
The Arrowhead Plant is a commonly cultivated species, being used as a houseplant since the late 19th century.
Freshwater Organisms (Cont.) • Also in a pond or freshwater source, you might also spot a frog, a turtle, or maybe a crayfish. Frog Turtle Crayfish
Freshwater Organisms (Cont.) • Farther out, where the water gets deeper, are microscopic plankton like algae and protozoa. Algae Protozoa
Saltwater Organisms • Like the freshwater ecosystem, the marine, or ocean, ecosystem is divided into several sections. • The shallowest is the intertidal zone. There the ocean floor is covered and uncovered as the tide goes in and out. Crabs burrow into the sand so they won’t be washed away. Mussels and barnacles attach themselves to rocks.
Saltwater Organisms (Cont.) • The open ocean is divided into two regions. The first region is up to 200 m (656 ft) deep. In this upper region are many kinds of fish and whales. The world’s largest animals--the 150-ton blue whales--live here. • The lower region goes from 200 m (656 ft) to the ocean bottom--perhaps 10.5 km (6.5 mi) down. At depths greater than about 1,000 m (3,281 ft), there is no sunlight. It is completely black!
Saltwater Organisms (Cont.) • Photosynthetic organisms, like algae, can only live where there is sunlight. They are found in the intertidal zone and in waters up to about 100 m (328 ft) deep. Many fantastic creatures live on the dark ocean bottom. Some of these fish “light up” like underwater fireflies. Other bottom-dwelling fish are blind. There are even bacteria that live in boiling water where fiery lava seeps out of the sea floor.
Can Humans Change Water Ecosystems? • People started hunting whales for their meat and oil at least 4,000 years ago. However, back then oceans held so many whales that hunting didn’t have much effect on their populations. • By 1850 American whalers alone accounted for the killing of 10,000 a year. • In 1962 alone 66,000 whales were killed. The whales could not reproduce fast enough to replace those that were being killed. • Many whale species became threatened with extinction.
In 1971 the United States banned its citizens from whaling for profit or even buying products made from whales. By the 1990s the IWC had succeeded in getting whaling countries to reduce or stop hunting threatened whales.
