Jan. 10, 2003 With fewer than 300 northern right whales remaining, the seriously endangered species may face yet another obstacle to recovery. The right whale is regularly exposed to the neurotoxins responsible for paralytic shellfish poisoning (PSP) through feeding on contaminated zooplankton. These toxins could affect respiratory capabilities, feeding behavior, and ultimately the reproduction condition of the whale population.
In the current issue of the journal Harmful Algae, a team of scientists, led by University of Rhode Island Graduate School of Oceanography (GSO) biologist Edward Durbin, describes how north Atlantic right whales, feeding in Grand Manan Basin in the lower Bay of Fundy in late summer, are exposed to PSP toxins from feeding directly on the contaminated copepod Calanus finmarchicus.
Other members of the scientific team include Gregory Teegarden, St. Joseph's College, Standish, ME; Robert Campbell, GSO; Allan Cembella, Institute for Marine Biosciences, Halifax, Nova Scotia, Canada; and Mark F. Baumgartner and Bruce R. Mate, College of Oceanic and Atmospheric Sciences, Oregon State University.
The scientists estimated that the toxin ingestion rates of right whales in Grand Manan Basin are substantial and are similar to the estimated minimum lethal oral dose for humans.
"While there is no direct evidence of PSP toxin-related deaths of right whales," said Durbin, "we suggest that during their prolonged summer feeding period in this region, they would be experiencing chronic exposure to PSP toxins."
The toxins are potent sodium-channel blockers in muscles and membranes and affect nerve function. Initial symptoms of PSP toxicity include parethesia and numbness and a weakening of muscles. In high doses, the PSP toxicity syndrome in mammals is characterized by respiratory difficulties, which may cause death in the absence of ventilatory support.
"Although PSP toxins do not tend to accumulate in most mammalian tissues, chronic effects of repeated PSP toxin exposure will be seen in measures of diving capabilities, including dive times, swimming speeds while at depth, and frequency of dives," added Durbin.
"Impaired diving capabilities in right whales would lead to reduced ingestion rates and may be a possible explanation for their poorer condition and reduced calving rates despite the high concentrations of copepods in Grand Manan Basin."
Other effects of toxin ingestion on "whale fitness" may be greater susceptibility to disease, reproductive failure, disruption of migration and mechanical damage, e.g., by collisions with ships or fouling in nets and other fishing gear. For example, recovery from dives during periods of PSP exposure would likely be longer than normal, and increased time at the surface would increase a whale's chances of being hit by a ship.
"The significance of ingested PSP toxins on the survival of right whales should not be underestimated," said Durbin. "Few studies have been done on the effects of these toxins on higher mammals, and none on the effects in whales. Our findings are the first to suggest that physiological impairment due to exposure to high dosages of PSP toxins through the food chain may compromise the health of a population."
This research project was supported by the National Science Foundation, the National Oceanic and Atmospheric Administration, the Office of Naval Research, the NASA Space Grant and Earth System Science Programs, Oregon State Marine Mammal Endowment, and the National Marine Fisheries Service.
The URI Graduate School of Oceanography is one of the country's largest marine science education programs, and one of the world's foremost marine research institutions. Founded in 1961 in Narragansett, RI, GSO serves a community of scientists who are researching the causes of and solutions to such problems as acid rain, harmful algal blooms, global warming, air and water pollution, oil spills, overfishing, and coastal erosion. GSO is home to the Coastal Institute, the Coastal Resources Center, Rhode Island Sea Grant, the Institute for Archaeological Oceanography, and the National Sea Grant Library.
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