The Algal bloom reference article from the English Wikipedia on 24-Jul-2004
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Algal bloom

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A "red tide" resulting from a dinoflagellate bloom discoloring the water on the right

An algal bloom is a relatively rapid increase in the population of (usually) phytoplankton algae in an aquatic system. Typically only one or a few species are involved and the bloom is recognized by discoloration of the water resulting from the high density of pigmented cells. Colors observed are green, yellowish-brown, or red.

The excessive growth of algae may disrupt higher links of the local food web. Algae that die and sink to the bottom stimulate growth of decomposers, especially bacteria. Decomposition can result in the depletion of oxygen in the deeper water layers, and these conditions may result in fish kills or replacement with less valuable species more tolerant of higher phosphorus and lower oxygen levels. Deoxygenation also may cause chemical changes in the mud on the bottom, lowering the Redox value of the sediment, releasing chemicals and toxic gases. All these changes further accelerate the eutrophication of the aquatic ecosystem.

Table of contents
1 Red tide
2 Black water
3 External link

Red tide

The so-called red tide is an example of a naturally occurring marine algal bloom. Red tide is caused by species of dinoflagellates, often present in sufficient numbers (thousands or millions of cells per liter) to turn the water red or brown.

Coastal pollution produced by humans appears to be a causal factor in red tides in some parts of the world, but red tides also occur in places where there are no associated human activities. Some red tides produce large quantities of toxins, which kill fish and are accumulated by filter feeders, like shellfish. This bioaccumulation of toxins is why one must be careful eating shellfish collected at certain times of the year.

Black water

So-called black water is a dark discoloration of sea water, first described off the Florida coast in 2002. Although fisherman in Florida have complained and requested that the "government do something", scientists say that black water results from a non-toxic algal bloom, probably of diatoms.

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