"Dark Tides, Ill Winds"

Part 3 on Altered Oceans

...About 60,000 people in the United States are poisoned each year by algae blooms. Most get sick by eating fish and shellfish that concentrate neurotoxins from the vast quantities of algae they consume.

The Centers for Disease Control and Prevention estimates that only 2% to 10% of all cases are reported to health authorities — usually those that involve numbness, paralysis, coma or other severe symptoms. Cases of nausea, cramping and diarrhea tend to go unreported.

Estimates of algae-related illness don't include the many thousands of people in Florida and other Gulf Coast states who suffer from inhaling airborne brevetoxin.

Nearly every coastal region has outbreaks of harmful algae or bacteria.

...When you look at it statistically, red tides are 10 times more abundant than they were 50 years ago," Brand said. Once, "the peak time was in the fall…. Now we have blooms continuing on and lasting into the winter and spring."

The highest concentrations of algae, he said, were along heavily developed shorelines and around the mouths of rivers that disgorge nutrient-laden waters from sugar-cane fields and sediment from phosphate mines.

Brand said that was no coincidence. It reflects "a huge increase in sewage, runoff from lawns and golf courses, mining and agriculture," he said.

...Red tides have become a staple of the daily reports on surf conditions posted on the lifeguard tower. The sign read: "Some Red Tide = Coughs. Sneezes. Dead Fishes." A few extra words were scribbled in chalk in the margin: "Can't do anything about [it]."

Some of the toxins:

Saxitoxin accumulates in mussels, clams, oysters and other shellfish, as well as in sardines, herring and puffer fish, without harming them. The toxin can poison seabirds, marine mammals and humans who eat contaminated fish or shellfish.

Domoic acid accumulates in clams, mussels, oysters, crabs, anchovies and sardines. It can sicken or kill seabirds, sea otters, sea lions, dolphins, whales and humans.

Brevetoxin accumulates in shellfish and sea grasses without harming them, but it poisons fish, manatees, dolphins, sea turtles and seabirds, as well as humans who inhale the neurotoxin or eat contaminated seafood.

Ciguatoxin is picked up by smaller algae-eating fish and passed up the food chain to predators such as barracuda, snapper, jacks, grouper and kingfish. Although the toxin doesn't appear to harm these fish, it can sicken people who eat them.

Sources: "Harmful Algal Research and Response: A National Environmental Science Strategy 2005-2015," Bigelow Laboratory for Ocean Science, Woods Hole Oceanographic Institution. Graphics reporting by Kenneth R. Weiss.