MEPS 345:129-140 (2007)  -  DOI: https://doi.org/10.3354/meps06951

ABSTRACT: Environmental stress and productivity models for community dynamics assume that the ecological responses of species are based on sub-organismal (physiological, cellular, molecular) mechanisms. Early tests of these models did not incorporate evaluation of physiological responses. Advances in remote sensing and molecular biology now allow more mechanistic and integrative approaches. In this study, we employed between-zone translocation experiments to test the effects of environmental stress and feeding time on the zonation of 2 species of mussel on rocky shores in New Zealand. Response variables were survival, shell growth, relative tissue mass, and short-term capacity for protein synthesis (indexed by RNA:DNA ratios). We predicted that the ecological and physiological performance of both mussels should increase with depth on the vertical tidal axis, but that the low-zone-dominant Perna canaliculus should perform relatively better than the mid-zone-dominant Mytilus galloprovincialis lower on the shore and at the more wave-exposed site. In contrast, we predicted that mid-zone-dominant M. galloprovincialis should perform relatively better than P. canaliculus higher on the shore and at the less wave-exposed site. Collectively, the ecological and molecular responses supported many, but not all of our predictions. As expected, P. canaliculus out- performed M. galloprovincialis in the more wave-swept and lower shore habitats, and showed lower tolerance of the stressful conditions that prevail higher on the shore, suggesting that the zonation pattern was based on differential responses to stress and food environments.

KEY WORDS: Mussels · New Zealand · Zonation · Eco-physiology · Field experiments · Molecular indices