Predicting metabolic rates of calanoid copepods

• Three different approaches were tested to estimate copepod metabolism.
• ETS activities provided good estimates of respiration rates.
• Copepod in situ metabolic rates lie between standard respiration and ETS activities
• Depth and general activity were significant factors explaining respiration rates.
• For meaningful interpretations copepods' life history traits have to be considered.

Respiration rates and electron transport system (ETS) activities were measured in dominant copepod species from the northern Benguela upwelling system in January–February 2011 to assess the accuracy of the ETS assay in predicting in vivo respiration rates. Individual respiration rates varied from 0.06 to 1.60 μL O2 h− 1 ind− 1, while ETS activities converted to oxygen consumption ranged from 0.14 to 4.46 μL O2 h− 1 ind− 1. ETS activities were significantly correlated with respiration rates (r2 = 0.79, p = 0.0001). R:ETS ratios were lowest in slow-moving Eucalanidae (0.11) and highest in diapausing Calanoides carinatus copepodids CV (0.76) while fast-moving copepods showed intermediate R:ETS (0.23–0.37). 82% of the variance of respiration rates could be explained by differences in dry mass, temperature and the activity level of different copepod species. Three regression equations were derived to calculate respiration rates for diapausing, slow- and fast-moving copepods, respectively, based on parameters such as body mass and temperature. Thus, knowledge about the activity level and behavioral characteristics of copepod species can significantly increase the predictive accuracy of metabolic models, which will help to better understand and quantify the impact of copepods on nutrient and carbon fluxes in marine ecosystems.