Respiration in marine pelagic copepods: a global-bathymetric model

Historical global respiration datasets of epipelagic copepods and recent bathymetric respiration datasets of mesopelagic, upper- and lower-bathypelagic and abyssopelagic copepods were combined to build a global-bathymetric respiration model by adopting 2 regression models (theoretical and empirical ones). Designated independent variables including body mass (expressed as dry mass, carbon or nitrogen), habitat temperature, ambient oxygen saturation and the depth of occurrence were all significant, accounting for 72 to 80% in the variation in these respiration data. Both theoretical and empirical regression models yielded similar results, but the latter was sensitive to the choice of body mass. The mechanisms leading to a negative effect of depth and a positive effect of oxygen saturation on respiration rates are thought to be due to 'predation-mediated selection' and the lack of specialized respiratory organs (i.e. oxygen diffusion through the body surface), respectively.