Meeting Abstract

8.2  Friday, Jan. 4  The effect of thermal stress and hypoxia on the hyperiid amphipod Phronima ELDER, L*; SEIBEL, B; Univ. of Rhode Island; Univ. of Rhode Island

Hyperiid amphipods in the Eastern Tropical Pacific migrate across a temperature gradient of 10 degrees or more and spend daytime at oxygen levels less than 5µM. To determine if these current conditions are physiologically demanding, oxygen consumption, lactate accumulation and HSP 70 expression were measured in the hyperiid amphipod Phronima. Thermal stress experiments were conducted at 23ºC, the approximate maximum surface temperature in the region, with recovery at 10-20ºC or further thermal stress up to 29ºC. Separate respiration experiments were performed under conditions equivalent to day and nighttime exposure, 10°C hypoxia (1% O2), and 20°C normoxia (21% O2). Oxygen consumption decreased from 2.82 µM O2/g*h in normoxia to 1.82 µM O2/g*h in hypoxia. The Q10 (a measure of temperature dependence of metabolism) is approximately 2 between 10 and 20°C. L-lactate, an index of anaerobic ATP production, was significantly higher, in hypoxic (8.92 ± 1.33 mmol/L Lactate), compared to normoxic, (3.47 ± .47 mmol/L lactate) specimens. In hypoxic conditions lactate accumulation increased at higher temperatures, and was elevated after 24hrs at 23ºC even in oxygen saturated conditions. These data indicate that amphipods are near maximum thermal levels and approaching critical oxygen levels during their current migration. Climate change is predicted to cause an increase in oceanic temperatures and decease in oceanic oxygen levels. Ecological implications of these changes will be discussed.