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Tainted bass a warning for all of us

March 10, 1989

What a winter for the Everglades. First the sawgrass catches fire, and now the fish are contaminated.

Health agencies have warned anglers not to eat any largemouth bass or warmouth caught in Conservation Areas 2 and 3. They've also suggested reduced consumption of bass pulled out of the Loxahatchee National Wildlife Refuge.

The reason: Samples of these fish show high and potentially harmful levels of mercury.

Such a warning is unprecedented for any freshwater species in Florida. When bass (the state fish) are in jeopardy, it's a startling signal that something very bad is happening out in the black muck of the Glades.

The story goes way beyond the culinary concerns of weekend fishermen. What's happening—invisibly, bewilderingly—is the poisoning of the source of our water and of the food chain that it supports. Animals that ingest mercury don't necessarily die, but they sometimes stop reproducing.

The sprawl of the contamination is boggling. They're not talking about a backyard pond or a patch of marsh or even a whole creek. The danger zone encompasses more than 1,200 square miles of vital watershed.

Tainted bass have been found as far north as Loxahatchee and as far south as the L-67 canal in Dade. The fish, about 70 in all, were collected with electronic stunning gear. They weighed between 2 and 8 pounds each. Experts were shocked at the amounts of mercury discovered.

The government considers any level exceeding 0.5 parts per million to be cause for concern. Anything over 1.5 is unfit for human consumption.

No wonder health workers were alarmed, then, when one of the sample Everglades bass tested at 4.4 parts mercury per million. Some sites yielded fish with levels averaging 2.5.

Much has been made of these statistics because people want to know how much mercury is safe to eat. Fact: Bass aren't supposed to have heavy metals in their flesh.

In humans, mercury poisoning can damage the central nervous system.The most famous and tragic outbreak occurred in the 19505, when mercury-laden effluent from a factory contaminated the fish in Minamata Bay, Japan. Thousands of people who ate the fish suffered severe mercury poisoning that led to blindness, paralysis and birth defects. More than 300 died.

The Everglades scenario is not so extreme. The average person would have to eat a mess of tainted bass to be affected, but the health risk is larger for pregnant women and nursing mothers.

Actually, the edibility of these fish is the least of concerns. The more urgent riddle is where the pollution is coming from and what it portends for the ecology of South Florida.

"There is no theory at this point," says Frank Morello, a biologist with the Game and Fresh Water Fish Commission. "It's just a mystery."

The possibilities are far-ranging. Mercury can travel airborne from coal-burning power plants. It's also a common residue of agricultural fungicides, which have been known to be flushed into the Glades.

Over time mercury accumulates in living tissue, and the high levels found in the bass suggest a serious long-term pollution. Sediment samples might provide some clues, if not answers. The trick is tracing the source of this slop and identifying the offenders.

In a way, the invisible nature of the mercury threat makes it easy to underestimate. It's not like a red tide or a chemical spill. You won't see lots of bloated bass or dead panfish floating around the docks; in fact, you won't see much of anything.

A sudden fish kill looks more dramatic, but it tends to be brief and contained. The slow poisoning of an entire ecosystem is more sinister and potentially more catastrophic.

The hushed beauty of the Everglades is deceiving. It is so rich with life that we naturally assume all the life to be healthy.

For now, mercury and all, there are plenty of lunker largemouth bass to be caught. But the way it's going, someday we'll be fishing for them with magnets instead of worms.


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