Are meiofauna a standard meal for macroinvertebrates and juvenile fish?

Abstract

Due to the lack of empirical data, meiofauna are often underestimated as prey for freshwater animals and are commonly regarded as trophic dead ends. Here we present a synthesis of recent evidence showing that meiofauna are significant as prey, not only for many benthic macroinvertebrates (chironomids, shrimps, and flatworms) but also for juveniles of widespread freshwater bottom-feeding fish species (e.g., carps, gudgeons, catfish). In this review, we focus on the following questions: (1) Which groups consume meiofauna? (2) In what amounts are meiofauna ingested? (3) Does predatory feeding behavior influence natural meiofaunal communities? (4) Are meiofauna organisms actively ingested or are they bycatch? To answer these questions, we focused on studies that included gut/feces analyses of potential predators and empirical investigations conducted in the laboratory (e.g., functional response experiments and microcosm studies) and in the field (enclosure/exclosure settings). We were able to demonstrate that meiofauna taxa are consumed in high numbers by a wide range of larger organisms. This predation can significantly shape meiofaunal communities, by reducing the abundance, biomass, and production of certain members of the investigated assemblages. However, in most cases, it remains unclear if there is an active predation of meiofauna or a passive ingestion by unselective feeding.