Meeting Abstract
Unprecedented increases in atmospheric carbon dioxide over the past century have resulted in a global reduction of seawater pH, or ocean acidification (OA). To date, the majority of studies on biological responses to OA involve short-term experiments where a single life stage is exposed to seawater chemistries predicted to occur in the future. Few studies address the influence of long-term acclimation and the potential for adaptive evolution to OA. I performed multigenerational experiments on the harpacticoid copepod Tigriopus californicus to investigate long-term responses to increased acidity. I collected copepods from supralittoral splash pools at four geographically isolated sites on San Juan Island, WA to maximize potential genetic variation in laboratory cultures. Reproductive F0 females from each population were allocated to three pH treatments: 8.0 (control), 7.5, and 7.0. To elucidate the effects of historic pH exposure on current performance, F1 reproductive females were split into three groups: one group kept in the same treatment and the other two groups transplanted into the other two treatments. The copepods were maintained in these treatments through the F2 generation (experimentation on subsequent generations is ongoing). For each generation and population, I quantified survivorship, fecundity, development time, and morphology. Preliminary data show that fecundity is reduced in the 7.0 pH treatment. This suggests that responses to low pH may involve changes in energetics and resource allocation. There seems to be no effect on adult survivorship, which is not surprising considering the extreme abiotic conditions in the splash pool habitats of T. californicus. Differences in responses among populations were also observed. Thus, there may be local adaptation to different environmental conditions within isolated habitats on San Juan Island.
