MEPS 539:33-46 (2015)  -  DOI: https://doi.org/10.3354/meps11473

ABSTRACT: We investigated the relationship between functional diversity and secondary production in an estuarine system subjected to anthropogenic impacts and climate events. Data consisted of a 14 yr long study of benthic invertebrate production from a seagrass bed and a sandflat. We used generalized linear models to test whether secondary production was explained by a functional identity effect (dominant traits in the community), by a complementarity effect (dissimilarity in trait measurements) or by their combined effects. From a priori correlations among community-weighted means for all traits, we identified 3 main life-history groups in the estuarine communities, reflecting different strategies to cope with disturbance and resulting in different production levels: species with an opportunist strategy, large slow-growing species and species with attributes providing higher competitive advantages, such as high mobility and omnivore feeding. The functional identity effect, also known as mass ratio hypothesis, was tested with a model combining these life-history groups. Overall, the functional identity/mass ratio effect model best explained variability in secondary production compared to the complementarity and combined effects models. In general, species with an opportunist strategy had higher production. These species explained a higher proportion of the production changes during the study period than the other 2 life-history groups. Nevertheless, this type of production, sustained by large numbers of small opportunist species with a rapid completion of their life cycle, may contribute towards an impoverishment of overall ecosystem functioning. In addition, we discuss the variation of all functional diversity measurements for the sites along the study period and relative to the changes in production.

KEY WORDS: Secondary production · Functional diversity · Benthic community · Estuarine environments · Mass ratio hypothesis