Partitioning of production and respiration among size groups of organisms in an intertidal benthic community

Published data on production of natural populations of benthic organisms were used to derive allometric equations relating annual production per unit biomass (P: B ratio) to mean individual body mass (time and biomass weighted) in the population on which production was measured. Separate equations were derived for meiofauna and macrofauna. Since no published data on production and size-structure in natural bacterial populations were found, P:B ratios for bacteria were calculated by extrapolation from an all-inclusive regression. In situ respiration was then calculated from production assuming the two to be approximately equal over an annual cycle for bacteria and benthc microalgae, and using an empirical relation between annual respiration and production in marine benthic animals for meiofauna and macrofauna. Monthly observations of benthic biomass spectra at Pecks Cove, an intertidal site in the upper Bay of Fundy, were used to estimate production and respiration in bacteria, microalgae, meiofauna, and macrofauna from the allometric equations. These estimates compared well with measured production for Corophjum volutator and Macoma balthjca, the 2 dominant macrofaunal species, and w ~ t h gross primary production by benthic microalgae, but not with total community respiration as measured by sediment oxygen consumption. Calculated values for production by bactena were of an expected magnitude ~f between 1 and 10 O/O of the total biomass was assumed to be active. The contribution of meiofauna and macrofauna to total community production (8 to 19 %, depending on the assumphon for bacterial achvity) was d~sproportionately small compared to their relahve biomass (47 to 52 %, also depending on what proportion of bacterial biomass was considered to be actlve). Estimates of respiration were much higher than measured rates of sediment oxygen consurnphon (2.5 to 5.5 times), although both followed closely sirmlar seasonal trends. Bacterial produchon in nature must be directly measured before the validity of our calculations can be assessed. However, we conclude that it 1s possible to obtain reasonable estimates of annual production and its distribution among slze groups in natural benthic comn~unities of eukaryotic organisms using allometric P : B scal~ng.