Biology » Ecology and the Biosphere » Aquatic Biomes

Summarizing Aquatic Biomes


Aquatic ecosystems include both saltwater and freshwater biomes. The abiotic factors important for the structuring of aquatic ecosystems can be different than those seen in terrestrial systems. Sunlight is a driving force behind the structure of forests and also is an important factor in bodies of water, especially those that are very deep, because of the role of photosynthesis in sustaining certain organisms. Density and temperature shape the structure of aquatic systems. Oceans may be thought of as consisting of different zones based on water depth and distance from the shoreline and light penetrance. Different kinds of organisms are adapted to the conditions found in each zone. Coral reefs are unique marine ecosystems that are home to a wide variety of species. Estuaries are found where rivers meet the ocean; their shallow waters provide nourishment and shelter for young crustaceans, mollusks, fishes, and many other species. Freshwater biomes include lakes, ponds, rivers, streams, and wetlands. Bogs are an interesting type of wetland characterized by standing water, lower pH, and a lack of nitrogen.


abyssal zone

deepest part of the ocean at depths of 4000 m or greater

algal bloom

rapid increase of algae in an aquatic system

aphotic zone

part of the ocean where no light penetrates

benthic realm

(also, benthic zone) part of the ocean that extends along the ocean bottom from the shoreline to the deepest parts of the ocean floor


width of a river or stream from one bank to the other bank

coral reef

ocean ridges formed by marine invertebrates living in warm, shallow waters within the photic zone


invertebrates found within the calcium carbonate substrate of coral reefs

ecosystem services

human benefits and services provided by natural ecosystems

emergent vegetation

wetland plants that are rooted in the soil but have portions of leaves, stems, and flowers extending above the water’s surface


biomes where a source of fresh water, such as a river, meets the ocean

intertidal zone

part of the ocean that is closest to land; parts extend above the water at low tide

neritic zone

part of the ocean that extends from low tide to the edge of the continental shelf

oceanic zone

part of the ocean that begins offshore where the water measures 200 m deep or deeper

pelagic realm

(also, pelagic zone) open ocean waters that are not close to the bottom or near the shore

photic zone

portion of the ocean that light can penetrate


animal species that eats plankton


animal species that hunt and are carnivores or “flesh eaters”


type of free-floating marine seaweed

source water

point of origin of a river or stream

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