Meeting Abstract

10.2  Monday, Jan. 4  Broad salinity tolerances of the invasive clam Nuttallia obscurata DONOVAN, D.A.*; ELSASSER, P.A.; WITTES, J.W.; Western Washington University; Western Washington University; Swarthmore College, Pennsylvania donovan@biol.wwu.edu

Nuttallia obscurata was introduced from the Western to the Eastern Pacific Ocean in the late 1980s and has spread rapidly through the Puget Sound and Straight of Georgia. It is commonly found living high in the intertidal zone and in regions of varying salinity. We investigated how N. obscurata responds to hyposmotic, hyperosmotic, and thermal stress in order to investigate whether broad physiological tolerances play a key role in its success as an invasive species. Clams were acutely exposed to salinities ranging from 1 ppt to 60 ppt at 10 ^oC and 20 ^oC and mortality was monitored for two months. Both salinity and temperature significantly affected mortality, although mean survival of clams held at 1 – 50 ppt at 10 ^oC was greater than 45 days. In a similar experiment, gill tissue was excised and acutely exposed to 1 – 60 ppt at 10 ^oC and 20 ^oC and mortality was monitored over two weeks. Both salinity and temperature significantly affected tissue mortality, and there was no interaction between the two variables. However, the gill tissue was surprisingly tolerant of very low salinities. At 10 ^oC, gill tissue was able to survive for two weeks at salinities ranging from 1 – 30 ppt. These results are supported by data showing that N. obscurata osmoconforms at salinities ranging from 10-50 ppt and osmoregulates at 1 and 5 ppt, and that gill tissue hydration remains relatively stable over the range of salinities.