Biological consequences of global warming: does sea surface temperature affect cetacean distribution in the western Ligurian Sea?

Abstract

The aim of this study was to assess if sea surface temperature does affect cetacean distribution in the western Ligurian Sea. Relationships with temperature were investigated for: striped dolphin (Stenella coeruleoalba), fin whale (Balaenoptera physalus) and sperm whale (Physeter macrocephalus). Remotely sensed sea surface temperature (SST) data were studied. A series of 20 monthly images (i.e. June to September monthly images from 1996 to 2000) was considered. Concurrently, distribution data collected during shipboard summer surveys, and covering an area of about 20,000 km2 in the western Ligurian Sea, were analysed. The relationship between the three species presence and SST was investigated by using a grid of 3 × 3 nautical mile cell units. For every cell the SST mean, standard deviation, coefficient of variance and the deviation from the monthly average were calculated. Finally, binary logistic regression functions allowed to assess significant (P < 0.05) relationships with temperature in these species. These logistic models, were able to predict 60–78% of the species presence(1)/absence(0) cells, and suggest the need for further investigations spanning longer time periods to assess how the global climate change has been changing and will change in the future cetacean distribution in the western Ligurian Sea.