Trophic dynamics of two omnivorous shrimps in the middle Paraná River

Abstract

Abstract The study of the relative importance of different sources of resources in freshwater food webs is key to understanding ecosystem functioning. The shrimps Macrobrachium borellii and Palaemon argentinus are sympatric species that, given their abundance, are important components in the trophic webs of the Paraná River. This river presents a vast floodplain dominated by C3 plants, which in periods of high water (HW), is available as a trophic resource for aquatic organisms. Both M. borellii and P. argentinus are omnivorous consumers and mobile swimmers, so they may play an important role in the incorporation of these terrestrial resources into the aquatic trophic webs during HW. In the present study, we aimed to estimate the relative contribution of trophic web sources using stable isotope analysis (SIA) of muscle and hepatopancreas and stomach content analysis (SCA). The trophic strategy, niche breadth and niche overlap of both shrimp species throughout the hydrosedimentological cycle were also analyzed. The results indicate that both species can consume C3 plants and that, unlike P. argentinus, M. borellii rapidly exploits the available C3 plants during HW. On the other hand, the niche breadth of M. borellii is generally larger than that of P. argentinus, while the niche overlap between both species is smaller during LW. The results obtained highlight the role of shrimp in aquatic food webs, as they can exploit C3 carbon sources during HW and make it available to other aquatic consumers, thus playing a key role in connecting floodplain primary production and water bodies.