#RED TIDE GRAPH OCCURRENCE PSP#
A seven-month closure on the harvest of Atlantic surf clams was necessary because this species tends to retain the PSP toxin for a long period of time, often months after the algae bloom has subsided. Red tide occurrences and hypoxia are the problems in the worldwide sea and lakes but they are not settled. Record levels of toxicity were measured at several New Hampshire monitoring stations, and many areas were closed for harvesting for most of May, June and July. One of the worst outbreaks of PSP in New England occurred in the spring/summer of 2005, causing widespread closures of recreational and commercial shellfish areas in Maine, New Hampshire and Massachusetts. A red tide blooms off the coast of Texas. The name red tide comes from the fact that overgrowth of algae can cause the color of the water to turn red, as well as green or brown. A red tide occurs when certain types of algae plant-like organisms that live in the watergrow out of control.
High levels of toxin and harvesting closures do not occur every year, but they do occur. Red tides can be hazardous to human health and sea life. Because PSP toxin levels can change very rapidly over the course of just a few days, waters may be closed for lower, but rising, amounts of toxin. New Hampshire shellfish waters are closed for harvesting when the PSP toxin levels in blue mussels reach the regulatory threshold of 80 micrograms of toxin per 100 grams of mussel tissue. The cycle repeats itself the following spring, when the cysts germinate into free-swimming, reproducing cells. The dinoflagellate genus Alexandrium often forms red tides. By the end of autumn, the Alexandrium cells settle in offshore ocean sediments in the form of cysts, where they lie dormant for the winter. Key Words: harmful algal bloom nitrogen nutrient phosphate protist red tide. George Island this week confirmed the presence of red tide after dozens of reports of fish kills and respiratory irritation, according to the Florida Fish. The nearest SST data from the red tide occurrence area were extracted. If weather patterns move these offshore blooms closer to the shore, filter-feeding shellfish in recreational and commercial harvesting areas can accumulate dangerous levels of PSP toxin, making harvest closures necessary. If water conditions are ideal, the cells of the toxic alga reproduce, and growth is exponential – a single cell can result in the reproduction of several hundred cells in just a few weeks. Other water conditions such as low salinity and warmer temperatures, which often develop following springtime rains, snowmelt, and warmer air temperatures, are also associated with blooms. Off the coastlines of Maine, New Hampshire and Massachusetts, Alexandrium blooms typically occur in the spring and early summer, in response to increased sunlight and nutrients. Various species of the Alexandrium alga cause PSP in the Gulf of Maine. Florida red tide is a higher-than-normal concentration of a naturally occurring, microscopic algae called Karenia brevis, often abbreviated as K. Although there are several species of marine algae that can cause a variety of illnesses, the main illness of concern in New England coastal waters is paralytic shellfish poisoning, or PSP.
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