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Effect of Hypo-osmotic Stress on Mortality and Regulation of Volume, Osmolality, and Magnesium Ion Concentrations in the Sea Anemone Metridium senile in South Slough, Coos Bay, Oregon
(University of Oregon, 2009-12) Austin, Heather L. (Heather Lara), 1984-
The sea anemone Metridium senile occurs along a salinity gradient in the South Slough Estuary, Oregon, where it is subjected to frequent and sometimes large fluctuations in salinity. This study determined how hypo-osmotic stress contributes to the survival and distribution of this population. In the laboratory, chronic exposure ofM. senile to 50% and 75% seawater for twenty-eight days resulted in partial regulation of volume and magnesium ions. Anemones transplanted to the field exhibited increased mortality and partial regulation of volume, osmolality, and magnesium ions with decreased salinity during the wet season (December-February) and less regulation during the dry season (June-August). This pattern of physiological tolerance coincides with observed trends of seasonal abundance and distribution. Previous studies describe M senile as a marine osmoconformer, however this estuarine population is able to withstand moderate hypo-osmotic stress through partial regulation of tissue osmolality and magnesium ions.