Original paper

Small-scale detritus-invertebrate interactions: influence of detrital biofilm composition on development and reproduction in a meiofaunal copepod

Brown, R.J. Rundle

Abstract

Microbial biofilms improve the quality and palatability of coarse particulate organic matter (CPOM) for freshwater invertebrates, but small-scale interactions between CPOM-associated biofilms and meiofauna are poorly understood. The aim of this work was to investigate whether the composition of biofilms attached to leaf litter influenced development (from nauplius to adult) and reproduction (embryonic developmental time and number of broods, eggs and nauplii per female) of the meiofaunal copepod Bryocamptus zschokkei. Biofilm composition was varied by allowing growth on different species of leaf (beech, Fagus sylvatica vs. oak, Quercus robur) and for different periods of time (beech leaves conditioned for 2 vs. 6 weeks). Despite significant differences in biofilm composition between oak and beech leaves (greater microbial colonisation and bacterial densities on the former), there was no significant difference in the development or reproduction of B. zschokkei fed on these biofilms. There were, however, significant differences in copepod reproduction between leaves conditioned for different times. Hatching success was significantly higher on leaves conditioned for 6 compared with 2 weeks, reflecting increased diatom densities on the former and suggesting that micro-algae may be an important food source to ovigerous females. Conversely, copepodid development was significantly slower on leaves conditioned for 6 compared with 2 weeks, reflecting the significantly lower bacterial densities on the latter; bacteria are likely to be a major component of the diet of smaller copepod life stages. These data suggest that small-scale changes in the composition of microbial biofilms can have a significant and complex influence on the life-history characteristics of B. zschokkei, and such meiofauna-detritus interactions may have important implications for the trophic dynamics of streams.

Keywords

copepodfood qualitybiofilmconditioninglife history