title: First respiration estimates of cold-seep vesicomyid bivalves from in situ total oxygen uptake measurements.
abstract: Vesicomyid bivalves are one of the most abundant symbiont-bearing species inhabiting deep-sea reducing ecosystems. Nevertheless, except for the hydrothermal vent clam Calyptogena magnifica, their metabolic rates have not been documented, and only assessed with ex situ experiments. In this study, gathering benthic chamber measurements and biomass estimation, we give the first in situ assessment of the respiration rate of these bivalves. The giant pockmark Regab, located at 3160m depth along the Congo-Angola margin, is a cold-seep site characterised by dense assemblages of two species of vesicomyids: Christineconcha regab and Laubiericoncha chuni with high dominance of C. regab. Two sites with dense aggregates of vesicomyids were selected to measure total oxygen uptake (TOU), and methane fluxes using IFREMER's benthic chamber CALMAR deployed by the ROV Quest 4000 (MARUM). Photographs were taken and bivalves were sampled using blade corers to estimate density and biomass. Total oxygen uptake was higher at Site 2 compared to Site 1 (respectively 492 mmol.m(-2).d(-1) and 332 mmol.m(-2).d(-1)). However, given vesicomyid densities and biomass, mean oxygen consumption rates were similar at both sites (1.9 to 2.5 μmol.g total dry mass(-1).h(-1) at the Site 1 and 1.8 to 2.3 μmol.g total dry mass(-1).h(-1) at Site 2). These respiration rates are higher than published ex situ estimates for cold-seep or hydrothermal vent bivalves. Although methane fluxes at the base of sulphide production were clearly higher at Site 2 (14.6 mmol.m(-2).d(-1)) than at Site 1 (0.3 mmol.m(-2).d(-1)), they do not seem to influence the respiration rates of these bivalves associated to sulphide-oxidizing symbionts.
authors.affiliation: IFREMER Centre de Brest, Unité Étude des Écosystèmes Profonds, 29280 Plouzané, France. carole.decker@ifremer.fr
authors.forename: Carole
authors.initials: C
authors.lastname: Decker
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Caprais
authors.forename: Alexis
authors.initials: A
authors.lastname: Khripounoff
authors.forename: Karine
authors.initials: K
authors.lastname: Olu
mesh_terms: D000818:Animals; D001267:Atlantic Ocean; D018533:Biomass; D049872:Bivalvia / Q000378:metabolism*; D003080:Cold Temperature; D017753:Ecosystem; D007700:Kinetics; D016014:Linear Models; D008697:Methane / Q000378:metabolism; D010101:Oxygen Consumption / Q000502:physiology*; D013440:Sulfides / Q000378:metabolism
chemical_list: D013440:Sulfides; D008697:Methane