Fresh water ecosystems include:
- Flowing Water:
Typically, rills join to form gullies, which join to form streams, which join to form a river.
Rivers can also begin as springs or seepage or outlets of ponds/lakes, for example:
Eventually. . .
Within a stream or river,
- are also known as rapids or white water. Riffles are the sites of primary production. Typically, organisms attach to the substrate to avoid being swept away by the current. Riffle areas have a high O2 content because of the churning.
- are the sites of decomposition. They serve as catch basins for organic materials and produce the CO2 used by the producers in the next riffle.
- silt and debris
- are carried downstream and deposited in slow-moving areas.
- are those parts of the stream or river channel used at high tide or after spring rains, etc.
- Still water:
Still water includes ponds and lakes.
Often, these have an autumnal temperature change or turnover as the upper water cools, becomes more dense, and sinks. Simultaneously, the lower water (now warmer) rises.
In midsummer, a lake has the typical epi-, meta-, and hypolimnion layers and other zones, as previously discussed, and the temperature in the epi- and hypolimnion are fairly constant. The temperature in the metalimnion changes with depth (there is a thermocline).
Wetlands are areas that range alone a gradient from permanently flooded to periodically saturated soil that supports hydrophytic plants.
Types of wetlands include
- where there is much emergent vegetation (cattails, etc.). A marsh is a wet prairie.
- which are wooded wetland (such as cypress or mangrove swamps).
- which can range from a filled-in lake to a mat of accumulated organic material with much water. Bogs depend heavily on precipitation to supply nutrients, so they usually are low in mineral salts and are acidic.
Salt concentration is a limiting factor for organisms which live in salt water. While open sea contains about 35 ppt of salt, estuary areas contain much less, and the concentration is more variable.
Oceans have a temperature gradient or thermocline like lakes, and overall water temperature is also based on latitude (arctic vs equatorial).
Water pressure increases with depth.
- Regions or zones of the ocean include
- pelagic zone
- which includes all the water and may be further subdivided as with the lake, but different names are used for the same things.
- The photic zone is the epilimnion, and photosynthesis occurs here. Seaweeds such as kelp, sea turtles, porpoise, numerous fish, sharks, crustaceans, and corals all live here.
Here are some of Jeff Gordon’s videos of various SCUBA dives:
- The mesopelagic zone is the metalimnion, which has a thermocline, and not much seasonal variation in temperature.
is the hypolimnion where there is total darkness, low temperature, and high pressure.
- benthic zone
- which is divided into the continental shelf or
and deeper water or the oceanic zone.
- intertidal zone
- which is the shoreline area between high and low tide. Organisms living in these areas must be able to tolerate changes/fluctuations in the amount of water.
- which is the area where fresh and salt water mix (at the end of a river). Organisms in an estuary must adjust to variable salt concentrations.
- tidal marsh
- which is an estuary with a large number of plants
Copyright © 1999 by J. Stein Carter. All rights reserved.
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