Are in situ weight-specific growth rates body-size independent in marine planktonic copepods? A re-analysis of the global syntheses and a new empirical model

Abstract

The dependency of in situ weight-specific growth rates of marine copepods upon individual body size (weight) was examined by compiling literature values. Two predictive models were compared to the compiled values, one in which weight-specific growth rate of individuals is dependent upon hod! size and temperature, and another in which weight-specific growth rate is dcpendent upon temperaturv but independent of indlvldual body size. By comparing pred~ctions from thc models with the compiled values, it is sho\vn that the former model is a better pred~ctor of weight-specific growth rates foi-manne copepods undcr most conditions. Temperature and body weight are of influence upon we~qht-specific growth rates for the whole data set (which includes adult, juvenile and mixed growth types), rates declining with increasing size. Allometric scaling coeff~cients of b = 0.581 to 0.737 were found when adult weight-specific fecundity and juvenile weight-spec~fic growth are considered together. while the significant relationships give b values of 0.706 and 0.739 when juvenile growth was considered alone. These are similar to those describing other metabolic rates. No significant relationship was found for weight-specific fecundity and body weight, although the data set was very limited. Copepod generation times were shown to b e weight dependent when compared to the combined geometric mean of e g g and adult weights rather than adult weight alone. By combining data from the literature, a new globally applicable empirical equation was constructed which allows predictions of the weight-specific growth rates of copepods from body weight and temperature. Given that many mesoand macrozooplankton samples are dominated by copepods, it is suggested that this equation may b e the most appropriate for estimat~on of growth and production for suites of such organisms when there is a lack of growth rate data available