Aquatic Biomes and Ecology Module Overview

Aquatic Biomes and Ecology 

As the universal solvent, this compound makes up the largest part of the biosphere and is the common link between the five biomes. Water covers nearly 75% of the Earth's surface. Aquatic region habitats comprise numerous species of plants and animals, both large and small. In fact, this is where life began billions of years ago when amino acids first started to come together. Without water, most life forms would be unable to sustain themselves and the Earth would be a barren, desert-like place. Although water temperatures can vary widely, aquatic areas tend to be more humid and the air temperature on the cooler side. The aquatic biome can be broken down into two basic regions, freshwater (i.e. ponds and rivers) and marine (i.e. oceans and estuaries).

Essential Questions

• What is the importance of water and the hydrologic cycle to ecosystems, human health, and economic pursuits?
• Can you describe the major types of freshwater and marine ecosystems?
• Can you discuss how we use water and alter freshwater systems?
• What is the distribution of global freshwater?
• Can you assess problems of water supply and propose solutions to address the depletion of fresh water?

 

Key Terms

Albedo: the luminosity shining from a reflective surface. Earthshine is one type. About 1/3 of the sun's radiation is reflected back into space, with the remaining 42% warming the land and air and 23% moving water through the hydrologic cycle. See Emissivity.

Algae: primarily marine organisms, single-celled or multicellular, that use chlorophyll to feed, like plants, but lack the roots, leaves, flowers, etc. of true plants.

Algae Bloom: the explosion of a phytoplankton population, sometimes because of incoming pollutants that artificially enrich the waters with nutrients. See Eutrophication and Red Tide.

Artesian: water pushed upward by the hydrostatic pressure of a confined aquifer. Overuse of artesian wells lowers the water table and sometimes makes nearby land sink (subsidence).

Aquaculture: growing and harvesting fish and shellfish in land-­‐based ponds. Relative protein yields often exceed those of land cropping by 4-­‐20 times. Ponds attract beneficial wildlife, cool the surrounding areas, reflect sunlight, draw birds, and make convenient places for growing rice and other moisture-­‐ loving plants. See also Hydroponics.

Aquifer: an underground layer of sand or rock that contains usable water. Can be unconfined (down to the first impervious rock layer) or confined (between the first and the second layers). See Artesian.

Benthic: organisms living on the seafloor. Littoral benthos occupies the space from the high-­‐water spring tide mark to 200 meters down. Deep-sea benthos lives below that.

Blue-­‐Green Algae: the old term for Cyanobacteria.

Brackish Water: water contaminated by salt, but with a salinity lower than 35 parts per thousand. See Brine.

Braided Stream: a watery network of twisting, sediment-bearing channels. Found atop alluvial fans.

Breaker: a wave that collapses forward near the shoreline as the shoaling sea bottom makes it top-heavy. It collapses when the ratio of its height to its wavelength passes 1:7.

Brine: seawater with a salinity greater than 35 parts per thousand. Brine is often made salty by evaporation.

Coral: marine invertebrates that secret a calcium carbonate exoskeleton and live symbiotically with algae, with the algae providing nutrients like carbon and the coral nitrogen, phosphorous, and an abode. Corals are perforate (porous skeleton) or imperforate (solid skeleton). Colonial corals live in deep water, and reef-building corals in warm, shallow water where their zooxanthellae algae can receive sunlight. When corals die, their outer skeletons remain, growing the reefs layer upon layer (see Atoll). As of the second millennium, two-fifths of the world's coral had disappeared due to industrial pollution, and all of the remainders is under threat.

Coral Bleaching: where coral loses their colorful symbiotic algae. This happens when carbon dioxide (a greenhouse gas) enters the water, cutting down reef production and leaving existing reefs vulnerable to erosion.

Cordgrass: several plant species living in brackish or saline estuarine marshes; below them are tidal mudflats, and above the salt marshes. Cordgrass produces five to ten times as much nutriment and oxygen as a comparable acreage of wheat. Very useful for tidal marsh restoration because its roots hold the mud in place as the plant brackets incoming waves while filtering them for nutrients.

Cyanobacteria: bacteria that photosynthesize. They were among the first living things on Earth. The food-making chloroplast of plants is actually a cyanobacterium imported long ago.

Emergent Wetlands: those whose vegetation is partly above water and rooted below it.

Estuarine Zone: an estuary--a watery coastal conflux where the tide meets river-- plus the surrounding wetlands (intertidal, salt marshes, lagoons, bay mouths, etc.) Thick with nutrients and organic matter, such zones are the highest producers in the ecosphere. Eliminating one removes the grasses needed by local fish, shrimps, snails, and other protein-rich organisms, deprives the are of a pollutant scrubber, and removes a key flood-control device. With strong-arm help from the Army Corps of Engineers, about half of the estuaries in the U.S. have been destroyed by dredging and filling and other forms of "development." 95% are gone in California. See Wetland.

Eustacy: sea-level changes due to seawater volume changes in the oceans.

Euphotic Zone: the zone of water penetrable by sunlight.

Eutrophic: productive; applies to habitats rich in nutrients and organic material.

Eutrophication: a gradual nutrient enrichment that increases organic matter production, as with a lake that absorbs waves of nutrient runoffs.

Eurybathic: able to tolerate different depths in water (like a sperm whale, which can ride on the surface or dive deeply). Contrast with Stenobathic.

Gaia Hypothesis: formulated by James Lovelock (1959) and further developed by Lynn Margulis, the scientific hypothesis that the Earth and its systems work as a self-regulating whole to maintain the biosphere through systemic feedback loops. The hypothesis was invented to answer the question of how certain environmental variables (gasses in the atmosphere, ocean salinity levels) that should be unstable remain in equilibrium.

Headwaters: the higher end of a stream's drainage.

High Moor: a bog whose vegetation is low in nutrients.

Stenobathic: able to tolerate only small changes in water depth (see Eurybathic).

Stenothermic: tolerating only a small range of temperature change.

Watersheds: We all live in a watershed -- the area that drains to a common waterway, such as a stream, lake, estuary, wetland, aquifer, or even the ocean -- and our individual actions can directly affect it. Working together using a watershed approach will help protect our nation's water resources.

Wetlands: Wetlands are areas where water covers the soil or is present either at or near the surface of the soil all year or for varying periods of time during the year, including during the growing season. This page provides links to basic information on the importance of wetlands, and about EPA's programs to protect them.

 

Review these terms below.

 

 

RESOURCES IN THIS MODULE ARE OPEN EDUCATIONAL RESOURCES (OER) OR CREATED BY GAVS UNLESS OTHERWISE NOTED. SOME IMAGES USED UNDER SUBSCRIPTION.