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Even when nutrient concentrations are higher in the rivers

2006-11-08 18:35:23 · 4 answers · asked by peternguyen0072002 1 in Environment

4 answers

A concise, easily understood article on eutrophication is posted at the first link below. However, I think more information is justified owing to the importance of this problem. I can recall my old German university professor (pre-global warming awareness days) state that "Eutrophication will ultimately be the biggest problem faced by man." Eutrophication happens when water oxygen levels drop below that which can sustain life. The ever-growing "dead zones" in the ocean, lakes, and estuaries seems to point to to this as a "right up there" environmental problem. As ever more fertilizer-intensive farming is adopted on an ever wider area to feed a growing world population, this problem is bound to intensify.

So much for the introduction. As long as oxygen levels are high enough to maintain life, eutrophication will not occur. Thus, a fast -moving river will mix air with the water, allowing a higher nutrient level without eutrophication. Whenever high nutrient water comes to rest and lacks mixing is where you are most likely to find eutrophication problems. That is why even heavily polluted rivers may not have a problem in their estuary if there is sufficient mixing of ocean water and the high nutrient fresh water. Of course, frequently the rivers are so heavily laden that their nutrients overwhelm the ability of the ocean to absorb them, leading to "dead zones" such as the one at the mouth of the Mississippi River.

One last note. Many rivers that flow out of eutrophic lakes can carry very low oxygen levels and the undesirable by-products of eutrophication, such as toxic algae, downstream where they can have extreme consequences, particularly under low flow conditions. The Klamath River in Northern California has had major salmon mortality linked in part to this problem, particularly in juvenile fish. This has led to the closure of a large part of the Pacific coast to salmon fishing in the last few years. Dam removal is being pursued as a mitigation measure. You can read more about it at the role that dams play in eutrophication at the second link below.

This is a long answer to a short question, but because this is such a crucial global problem that isn't talked about enough I thought I'd just volunteer more background.

2006-11-09 07:14:48 · answer #1 · answered by gordon B 3 · 0 0

Estuaries don't necessarily need to be stagnant. The Hudson River is an example of an estuary, sometimes brackish water (a mix of salt and freshwater) appears 150 miles from the Bay in New York City. But it is true that moving water does indeed hinder any eutrophication. The minerals and nutrients are constantly moving.

2006-11-09 01:02:37 · answer #2 · answered by Phantom 3 · 0 0

Rivers and streams are moving bodies of water which tend to purge itself of contaminates. Where lakes and estuaries are stationary bodies of water so they do not get the self purging effects rivers do.

2006-11-08 18:43:36 · answer #3 · answered by JUAN FRAN$$$ 7 · 0 0

Stagnant water in lakes & estuaries.
Rivers have running water.

2006-11-08 18:37:59 · answer #4 · answered by love_2b_curious 6 · 0 0

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