Determination of the Cell Concentration of the Red Tide Organism, Ptychodiscus Brevis, Required to Kill the Pinfish Lagodon Rhomboides
Jessop, Laura L.
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The marine dinoflagellate, Ptychodiscus brevis, is reponsible for Florida's red tides and produces a variety of toxins. The two major toxins produced are neurotoxins which cause massive fish kills, neurotoxic shellfish poisoning (NSP), and respiratory irritation in man when present in large concentrations such as those present during a red tide. The toxins have a heterocyclic fused ring system differing only at one terminus, which exhibits either an aldehyde function (T-Ald) or an alcohol function (T-Alc). Recent experiments show that the toxins cause sodium channels in nerve membranes to open, causing membrane depolarization and neuromuscular blocks. Few experiments have been done to determine the toxicity of these toxins on marine organisms. This study proposed to determine the cell concentration of P. brevis cells necessary to kill a sample of pinfish, Laqodon rhomboides, in 24 hours. Three bioassays were run using dilutions of P. brevis between 300,000 cells/l and 2,000,000 cell/l. Results showed that the pinfish died at concentrations of 1,000,000 cells/l and higher only when the P. brevis cells were lysed, thus releasing their toxins directly into the water. When the cells did not lyse, the pinfish could survive concentrations as high as 1,500,000 cells/l. The toxic concentration of P. brevis for L. rhomboides was found to be between 1,000,000 cells/l and 1,500,000 cells/l.