Metabolic rates and energy content of deep-sea benthic decapod crustaceans in the western Mediterranean Sea

Abstract

A total of 23 species of deep-sea benthic decapod crustaceans were collected in the Catalan Sea (western Mediterranean) at different depths (200–1250 m) but at the same environmental temperature (13°C) in winter 1992 and winter 1993. Studies on oxygen consumption and energy content were carried out on crustaceans exhibiting two life strategies: nektobenthic species (benthic species with a slight locomotory ability) and benthic-endobenthic species (strictly benthic species). The two deep-sea life styles were associated with two different patterns of metabolic rate and energy content. On the whole, metabolic rates, energy contents, and organic matter contents were higher for the nektobenthic life strategy than for the benthic-endobenthic life strategy. When results were related to depth of maximum abundance of the species consid-ered, it appeared that the nektobenthic species in the upper slope community (200–450 m depth) had a significantly lower energy content (as kJ g -1 of ash-free dry mass) than the nektobenthic species in the middle slope community (550–1250 m depth), but no significant trend was found when the energy content was expressed as a function of wet mass. The benthic-endobenthic species exhibited a significant decrease in metabolic rates, an increase in energy content (when expressed as a function of ash-free dry mass), no significant trend in energy content (as a function of wet mass) and a significant increase in water content with increasing depth over the two depth strata considered (200–450 and 550–1250 m). It was concluded that the lower metabolic rates of deeper-living benthic-endobenthic species, when compared to the shallower-living species, were the result of general locomotory reduction. It is likely that the shallower-living species rely more heavily on visual predation than the deeperliving species (light-limited environment), and this fact is discussed as an explanation of the general metabolic reduction for the benthic-endobenthic Mediterranean species along the depth gradient considered in the present study (200–1250 m).