Responses of the infaunal peracarid Monokalliapseudes schubarti (Tanaidacea: Kalliapseudidae) to a bottom trawling disturbance and seasonality in an estuary of southern Brazil

Abstract

ABSTRACTThe tanaid Monokalliapseudes schubarti is one of the dominant macrobenthic species in the shallow mudflats of southern Brazil. This species plays an important role in local trophic webs as a primary consumer and as a prey. This work investigated (1) the temporal variations in the population densities and structure of M. schubarti in the Patos Lagoon Estuary and (2) the potential impacts of shrimp trawling on the population densities, population structure and vertical stratification of the species in shallow areas of the estuary. The species exhibited significant temporal variability in its total densities and population structure, with a reproductive period observed during late summer and autumn, following an increase in salinity within the estuary. There were significant differences in M. schubarti densities, which appeared to be associated with variations in sediment texture and salinity. No well-defined pattern of trawling impact was identified; however, after high-impact trawling, decreases in the abundance of males and juveniles in the sediment superficial layer were recorded, and ovigerous females disappeared from the sampled area with relatively higher percentages of medium sand. Changes in the densities of different morphological categories observed after trawling were likely due to mortality, resuspension or rapid movement deeper into their tubes.