Evidence of long-term changes in the distribution of key intertidal species

World Congress of Malacology, Ponta Delgada, July 22-28, 2013.

Globally, changes are occurring in the biogeochemistry and ecology of the oceans, which may influence the physiology, phenology, and species distribution. Biological communities are reacting to climate change through changes in the abundance and phenology of the organisms and through the poleward shift in species distribution. Rocky shores are relatively simple ecosystems, which makes them an excellent model system for the understanding of the consequences of climate change. This study aims to examine the evidence of long-term changes on the distribution of key intertidal species in the Azores. Grey literature and unpublished data collected in the late 1980’s by Stephen J. Hawkins and his colleagues in the island of São Miguel (Azores) was compared to data collected in 2012. Whilst most taxa sampled in 1988 were still present during 2012, there were changes in species distribution. In general, there was an overall decrease in the abundance of organisms that was more pronounced on the sheltered area. In addition, there was generally a shift upwards of the vertical distribution of taxa that was more pronounced on the exposed area. These changes are temptatively interpreted as a consequence of increased temperatures and wave action (both predicted by climate change scenarios). This study also suggests that there may be interactive effects between environmental processes affecting species distributions. In addition, there was evidence that processes operating at large temporal scales may indirectly influence the distribution of species via changes in the abundance of their competitors.