Impacts of an invasion by green crab Carcinus maenas on the intertidal food web of a Patagonian rocky shore, Argentina

Abstract

The green crab Carcinus maenas (L., 1758) is a highly invasivespecies that has altered various coastal marine ecosystems worldwide.Green crabs were first found on the Argentinian Patagonian coast in2001 and were detected in Golfo Nuevo (Chubut, Argentina) in 2015. Inthis study, we described a rocky intertidal food web in the GolfoNuevo and evaluated the effect of green crab invasion on the network.We assembled the intertidal food web from a compilation of dietstudies and compared 2 scenarios: pre-invasion (without green crab)and post-invasion (with green crab). We calculated several structuralnetwork metrics to compare the scenarios. The green crab waspositioned as a top predator in the intertidal food web, consumingprey from different trophic levels and exhibiting the capacity toexert top-down control. Green crab presence altered the structure andstability of the food web. Additionally, we evaluated the effect ofpotential competitive interactions between native species and thegreen crab on the food web. Possible competitive interactionsincreased the effect the green crab had on the structure of the foodweb. Our results show that green crab invasion decreased food webstability by reducing the capacity of the food web to contain small-and long-range disturbances. These results contribute to theassessment and monitoring of the possible effects of other factors ofglobal change. The system is less stable than before green crabinvasion, and the drastic changes in community composition alreadyrecorded in rocky intertidal ecosystems in Patagonia are more likelyto amplify through the food web.