UPPER TEMPERATURE LIMITS IN MARINE BENTHIC SPECIES: A MACROPHYSIOLOGICALVIEW

Abstract : Defining species' upper temperature limits with ecological relevance is important in the context of environmental change. The approach used here is to draw the relationship between rates of temperature change and upper temperature limits in order to evaluate the acclimation temperature (Ta). This is a new approach to the integration of time and temperature in the evaluation of temperature limits. Using data previously published for different temperate and Antarctic marine environments. We calculated Ta at a macrophysiological scale, which allowed us to calculate a new index: the excess acclimatory capacity (EAC). This index is defined as the maximum environmental temperature increase which organisms in a given environment can cope with (calculated as the difference between maximum acclimation temperature and maximum habitat temperature). It provides a measure of how close a species/ assemblage/ fauna are to their limits and hence their vulnerability to environmental warming. In contrast to data for terrestrial environments showing that tropical species have less physiological flexibility than those from temperate or polar habitats, results here for marine environments shows a less clear pattern. The smallest EAC value here, was for the Peru upwelling system. The method applied here, relating temperature limits to rate of experimental warming, has potential for wide application in the identification of faunas with little excess acclimatory capacity to survive environmental warming.