Summary of Symposium on the Alexandrium fundyense Red Tide of 2005
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Summary of Symposium on the Alexandrium fundyense Red Tide of 2005
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    Alexandrium fundyense is a dinoflagellate that produces a toxin that can concentrate in the tissue of shellfish and cause paralytic shellfish poisoning (PSP) in humans who eat the shellfish. Animals such as marine mammals and birds can also be poisoned. A. fundyense and A. tamarense both occur in the Gulf of Maine, but for convenience, the name A. fundyense is commonly used for both (only specialized studies can differentiate them; they have similar toxicity). Also, for readability parts of this report may simply refer to the genus name Alexandrium. Blooms of A. fundyense are commonly called red tide, though the water rarely is discolored during blooms of this species. A. fundyense cysts in sediments germinate to yield motile cells when environmental conditions are favorable. An internal clock also regulates A. fundyense germination. Motile cells divide in favorable conditions of light, temperature and nutrients, doubling every 1.5-2 days under optimal conditions. When conditions are unfavorable for growth, e.g. depleted nutrients, gametes are formed, fuse, develop into a zygote and then into a cyst. The cysts fall to the ocean floor where they may remain dormant for many years. In the Gulf of Maine, there appears to be a positive relationship between the number of cysts in the sediments and the size of the blooms. A. fundyense has historically bloomed in the Bay of Fundy, but blooms were not known to occur in the southwestern Gulf of Maine, including Massachusetts Bay, until 1972 when a slow-moving tropical storm apparently transported cells down the coast, presumably from the Bay of Fundy. Following the 1972 bloom, recurrent annual outbreaks occurred in northern Massachusetts, New Hampshire, and western Maine through to the present. Farther south, in Massachusetts Bay, shellfish toxicity was frequent from 1972-1993 but nearly absent from 1994-2004 (despite recurrent toxicity in western Maine and New Hampshire). The Maine coastal current moves from the Bay of Fundy area south, and into and around Massachusetts Bay (currents not shown in Figure 2). The presence or absence of A. fundyense blooms in the western part of the Gulf of Maine and western Massachusetts Bay is related, in part to: 1) upwelling and downwelling events that are driven by wind direction, duration, and strength; 2) river runoff that brings freshwater, stratification, and nutrients; and 3) the abundance of cysts in sediments. Circulation, wind, and river runoff were favorable to bloom development in 2005, including two or more Nor'easter storms that pushed waters onshore. In addition, cysts were very abundant in offshore sediments.
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