Effects of temperature on chronic hypoxia tolerance in the non-indigenous brown mussel, Perna perna (Bivalvia: Mytilidae) from the Texas Gulf of Mexico

Effects of temperature (15 degrees, 20 degrees and 25 degrees C), O-2 partial pressure (P-O2=0, 1, 2, 4, and 6 kPa), and individual size (12-79 mm shell length; SL) on survivorship of specimens of the non-indigenous, marine, brown mussel, Perna perna, from Texas were investigated to assess its potential distribution in North America. Its hypoxia tolerance was temperature-dependent, survivorship being significantly extended at lower temperatures under all tested lethal P-O2. Incipient tolerated P-O2 was >= 4 and >= 6 kPa at 15 and 20 degrees C, respectively, with > 50% mortality occurring at 25 degrees C at all tested levels of hypoxia. P-O2 had less of an effect on survival of hypoxia than temperature. At 25 degrees C, survivorship was not different over a P-O2 range of 0-2 kPa and increased only at 4 and 6 kPa. Survivorship was size-dependent. Median survival times increased with increasing SL in anoxia and P-O2=1 kPa, but at 2, 4 and 6 kPa, smaller individuals survived longer than larger individuals. With tolerance levels similar to other estuarine bivalve species, P. perna should withstand hypoxia encountered in estuarine environments. Thus, its restriction to intertidal rocky shores may be due to other parameters, particularly its relatively low temperature tolerance.