Meeting Abstract
Increasing atmospheric CO2 in recent decades has caused increases in global temperatures and a reduction in seawater pH, so-called ocean acidification (OA). Physiological costs of responding to OA when the tide is in may compromise the ability of rocky shore organisms to mount effective thermal defenses when the tide is out, or may increase their susceptibility to other risk factors (e.g., reduced shell thickness can lead to increased threat of predation). Predicted changes in air and sea surface temperatures and ocean carbon chemistry over the next century are therefore expected to have dramatic effects on population dynamics, species interactions, and the structure of ecological communities. Our ability to effectively predict the consequences of co-occurring stressors on local community structure and associated ecosystem functions hinges on the development of realistic models of organismal responses to these perturbations, particularly models based on studies done in natural systems. During bouts of strong upwelling, nearshore and shallow intertidal areas in northern California can experience extended periods of acidified and hypoxic waters due to a relatively narrow continental shelf. To assess the potential effects of OA and thermal stress on intertidal communities in the field, we examined individual- and population-level changes of key calcifying species and their predators at multiple study sites along a 360 km section of coast that vary in their exposure to upwelling events and high temperature stress. Our data suggest that energetic subsidies associated with upwelling events in the field may currently overwhelm potential negative OA and temperature effects predicted from laboratory studies.
