Anthropocene breakdown of predator-prey interactions in the northern Adriatic Sea

Abstract

Predation can play an important role in shaping marine ecosystems, but we often lack long-term baseline data that would allow for tracking how predator-prey interactions have responded to increasing anthropogenic impact. Here, we assess temporal changes in benthic community composition and interactions between drilling predatory gastropods and their molluscan prey using the Holocene fossil record of the northern Adriatic Sea (NAS), a shallow shelf characterized by a long history of human transformation of coastal and deltaic ecosystems. Molluscan assemblages differ between the Isonzo and Po prodeltas but both regions show consistent temporal trends in the abundance of dominant species. Samples of mollusc prey collected at high stratigraphic resolution indicate that drilling frequencies have drastically declined in the prodelta of the Po River since the mid-20th century, while a weaker trend in more condensed sediments of the Isonzo delta is not statistically significant. The decrease in drilling predation intensity and the community turnover is related to the loss of predatory gastropods, decreased abundance of preferred and increased abundance of less-preferred prey organisms, and a rapidly progressing infaunalization observed in the northern Adriatic basin during the most recent decades. Our results align with data showing the substantial depletion of marine resources at higher trophic levels in the NAS and indicate that the strong simplification of the food web since the late 19th century accelerated since the mid-20th century.