RE: fried clams & red tide
Red Tide is the result of an algae bloom. The algae is harmless to the clams but toxic to humans
Not every plant poisoning is caused by a large, terrestrial plant. Several microscopic marine algae are notoriously poisonous to hapless humans who consume them in shellfish.
These Algae are tiny, single-celled plants that, like plants on land, capture and use the sun's energy to grow. The growth of algae is an essential life process, as it is the first step in transferring solar energy into aquatic food webs. The huge variety of marine algae are typically subject to annual cycles of growth & decay. These organisms thrive and multiply principally during the spring and summer, in response to increased light intensity and favourable levels of salinity & nutrients in ocean water. During the growth period, or bloom, each single algae cell may replicate itself one million times in two to three weeks.
During the reproductive riot of the bloom, warm, shallow seawater tends to become discoloured by the sheer concentration of algae seeking the sunlight. This discolouration is a result of the various pigments the plants use to trap sunlight; depending on the species of algae present, the water may reflect pink, violet, orange, yellow, blue, green, brown, or red. Since red is the most common pigment, the phenomenon has come to be called Red Tide.
Most species contributing to algal blooms are harmless, BUT (another big but!) some species are poisonous to animals which feed upon them directly or indirectly. Some of the toxins these species produce are seriously toxic. Often, the algae themselves are unaffected, as are the filter feeders, especially shellfish, for whom micro-algae are the principal diet. However, to carnivores further up the food chain, including humans, these toxins are potentially FATAL.
THE GUTS AND INTESTINAL TRACT of shellfish and fish which have consumed toxic algae accumulate and store the toxins. As a result, fish, provided they are gutted in the usual manner, are not a threat; nor, ironically, are scallops- a shellfish whose "meats"- the muscles that open and close its shell- are the only parts harvested for food. All other infected shellfish, however- especially mussels, oysters & clams.