HALPIN*, P. M.; MENGE, B. A.; HOFMANN, G. E.; Univ. of California, Santa Barbara; Oregon State Univ.; Univ. of California, Santa Barbara: Fine-scale temporal and spatial variation in the heat shock response of mussels in nature

One of the potential effects of global climate change is the increase of thermal stresses on organisms. Ecologists and physiologists are challenged to more completely understand how the heat shock response (HSR) is expressed and modulated in natural populations. We investigated the HSR in a competitively dominant, community-structuring organism, the mussel Mytilus californianus in two experiments at Strawberry Hill, Oregon. In the first, mussels were transplanted between upper intertidal (high thermal stress) and lower intertidal areas (low thermal stress) in the spring and collected in the summer and compared with the natural mussel population. The temperature at which mussels induced synthesis of Hsp70 was assayed in vitro on live tissue. In the second, mussels were collected on a 24-48 hr frequency from April-June from the low and upper intertidal areas in order to gain insight into how the HSR develops over time under field conditions as temperatures increase during the spring. Gill tissue was analyzed for total pool of Hsp70 and ubiquitin conjugates, which ?tag? damaged proteins for destruction by the cell. Temperature loggers that effectively mimic the thermal properties of mussels and record temperature at 10 minute intervals were deployed in upper and lower intertidal areas. Results indicate that mussels alter the temperature at which Hsps are produced in a habitat and time dependent manner.