DEP Invoice or Financial Record, September 30, 2001

NYC 9/11 Public Portal Document

OBSERVATORY

Nurit Karlin

By HENRY FOUNTAIN

From Dust to Red Tide Blooms of toxic algae, the phe­ nomenon known as red. tide, can kill fish, contaminate shellfish and make people ill. What brings on this sudden propagation of al­ gae is not completely known, al­ though water temperatures play a role in many cases. Now, researchers in Florida have imcovered a trigger for red tides along the state’s Gulf Coast, and lit com^s from Africa. The researchers say that clouds of dust from the Sahara provide a spike of nutrients in the Gulf of Mexico, unleashing a chain of events that can cause an algal bloom. The scientists, from the Univer- sity-of South Florida and other institutions, used satellite images and ground-based measurements to track large dust clouds — es- sentially, fine particles of soil — from the Sahara in June 1999. Carried by trade winds at alti­ tudes of up to 10,000 feet, the clouds took about two weeks to reach the Gulf of Mexico. One of the major elements in soil is iron, so as the dust settled in the gulf, iron concentrations in the water increased threefold. This, researchers say, caused the population of a particular nitro­ gen-fixing bacteria in the water to increase as welL The additional bacteria increased the amount of usable nitrogen in the water, and the nitrogen caused the algae to proliferate (much as nontoxic al­ gae proliferates in a lake or stream polluted by nitrogen­ based fertilizers). The researchers, who reported on their work in the journal Lim­ nology and Oceanography, say that- understanding this trigger mechanism may help in forecast­ ing algal blooms. —---- ----------------------------------------------------- ---- '■

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