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Aquatic ecosystem
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ecosystems, surface, salinity, organisms, source, production, seawater.
An aquatic ecosystem is an ecosystem located in water bodies. Communities of organisms dependant on each other and on their environment live in equatic ecosystems. The two main types of equatic ecosystems are marine ecosystems and freshwater ecosystems. Marine _______ cover approximately 71% of the Earth’s _______ and cotain 97 % of the planet’s water. They generate 32% of the world’s net primary________. They are distinguished from freshwater ecosystems by the presence of dissolved compounds, especially salts, in the water. Approximately 85% of the dissolved materials in seawater are sodium and chlorine. _____ has an average _______ of 35 parts per thousands of water. Actual salinity varies among different marine ecosystems. Marine ecosystems can be devided into the following zones: oceanic (the relatively shallow part of the ocean that lies over the continental shelf); profundal (bottom or deep water); benthic (bottom substrates); intertidal (the area between high and low tides); estuaries; salt marshes; coral reefs; and hydrothermal vents (where chemosynthetic sulfur bacteria form the food base). Classes of ________ found in marine ecosystems include brown algae, dinoflagellates, corals, cephalopods, echinoderms and sharks. Fish caught in marine ecosystems are the biggest _______ of commercial foods obtained from wild populations.
Water, reservoirs, sediments, species, rivers, fish, activity.
Freshwater
Freshwater ecosystems cover 0.8% of the Earth’s surface and contain 0,009% of its total ______. They generate nearly 3% of its net primary production. Freshwater ecosystems contain 41% of the world’s known fish _______. There are three basic types of freshwater ecosystems:
Lentic – slow-moving water, including pools, ponds and lakes.
Lotic – rapidly moving water, such as streams and rivers.
Wetlands – areas where the soil is saturated or inundated for at least part of the time (nearshore shallow waters).
Riparian – areas of land bordering a body of water.
Two important subclasses of lakes are ponds, which typically are small lakes that integrade with wetlands and water ______. Many lakes and bays whithin them gradually become enriched by nutrients and fill in with ogranic _______, a process called eutrophication. Eutrophication is accelerated by human ________ within the water catchment area of the lake. The major zones in river ecosystems are determined by the river bed’s gradient or by the velocity of the current. Faster moving turbulent water typically contains greater concentrations of dissolved oxygen, which supports greater biodiversity than the slow moving water of pools. These distinctions form the basis for the dicision of rivers into upland and lowland _______. The food base of streams within forests is mostly derived from the trees, but wider streams get the majority of their food base from algae. Anadromous ____ are also an important source of nutrients. Environmental threats to rivers include loss of water, dams, chemical pollution and introduced species.
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