Maine fishermen seem to be out of the woods and back on the open water. After a spring and early summer of massive red tides, shellfishing restrictions are easing again in the land of the summer dollar. Frantic restaurateurs are breathing a bit easier, the state's fishing communities are not drinking quite so heavily, and Senators Snowe and Collins no longer make the evening news for their courageous anti-red tide rhetoric.

Now that the coast is clear, let's have a look at the instant replay.

Red tides, like so many annoyances for us higher orders, are caused by some very basic critters having a career year. Back in May, New England's latest red tide started as its other's have: an alga, the dinoflagellate Alexandrium tamarense, realized conditions were perfect for starting a new family. Sometimes this can be a result of human sewage or agricultural fertilizer runoff providing lots of food. Other times, like this year, it's simply a question of run-of-the-mill algae cysts getting blown in shore by a storm and swirled about with warmish water and lots of other nutrients.

This May, the A. tamarense set about reproducing and didn't stop until its numbers were concentrated in the thousands of millions per milliliter. It's a unicellular algae, but that's still some impressive reproduction. This density is how the name red tide came about. You get that much algae together and the water looks red. Indeed, there are those who speculate that when the water flowed red with blood in Egypt as the plagues were visited upon Ramases, the Nile was really experiencing a rather robust red tide.

The problem with all these algae, aside from being groddy and making the locals think that the waterways are running with blood, is three-fold. One, algae have a short lifespan and will die, sink, decompose, and become food for all kinds of bacteria. Two, this process consumes a lot of oxygen and fish kills can result as cod are asphyxiated by the thousand. Third, and most relevantly here, some of these algal blooms produce neurotoxins. Nobody likes toxins.

Actually, shellfish don't mind them at all. Enter the hazards of the food chain. Shellfish are filter feeders and as they strain through the water, scoping for phytoplankton and other delicious treats, they take in the toxins created by the booming dinoflagellate population. A good-sized oyster can sift through seven gallons of water in an hour. If there are 20 million algae per milliliter in that water, that oyster is sucking in an ocean of toxins.

When humans eat such an oyster, the food poisoning can be severe. Although Maine has not documented a fatal case in the 50 years it's been tracking this sort of thing, the potential to die from eating toxic shellfish exists. At least theoretically, paralytic shellfish poisoning or PSP (Do the people at Sony know about this?) is the cause. The neurotoxins inhibit movement of ions across membranes, which can strip a body of muscle control. Lips go numb, speech becomes incoherent, and movement uncoordinated. During a red tide, a few clams can affect a person a lot like a few drinks. Too many and the lungs stop working. The diner could be dead in twelve hours. Take that, summer people.

That's the doom-and-gloom, worst-case, God-wants-you-to-let-his-people-go scenario. In practice, it's really a financial hardship for the people who make their living collecting shellfish. Red tides are not hard to spot, and although animals can be contaminated before and after the bloom, the authorities know how to close down toxic beds and no one wants to be the fishmonger selling poisoned food. Actual food poisoning during a red tide is limited.

Happily, the real star of the Maine pier, the lobster, is unaffected. The lobster is carnivorous and hasn't time to sit about filtering lots of water hoping to eat some plankton. She remains nontoxic and very popular with the out-of-towners, although during flare-ups of PSP it's not uncommon for the cautious to avoid any food that comes out of the ocean.

Dinoflagellates are also a source of bioluminescence. The coast of Maine always has some of these algae around and its undeveloped shores reveal glittery, magical water for those willing to go wading at night. The effect is not dissimilar to rubbing a blanket against itself in the dark and watching the static electricity light show. Only this phosphorescence is underwater. During a red tide, bioluminescence, like the neurotoxins, becomes much more prevalent. So my family is not pulling any mussels from the rocks along the coast, but they have all been telling me that the nightswimming is a shimmering, fairy-dust thing of wonder. And the summer people probably don't even know about it.

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