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

Abstract

The green crabCarcinus maenas(L., 1758) is a highly invasive species that has altered various coastal marine ecosystems worldwide. Green crabs were first found on the Argentinian Patagonian coast in 2001 and were detected in Golfo Nuevo (Chubut, Argentina) in 2015. In this study, we described a rocky intertidal food web in the Golfo Nuevo and evaluated the effect of green crab invasion on the network. We assembled the intertidal food web from a compilation of diet studies and compared 2 scenarios: pre-invasion (without green crab) and post-invasion (with green crab). We calculated several structural network metrics to compare the scenarios. The green crab was positioned as a top predator in the intertidal food web, consuming prey from different trophic levels and exhibiting the capacity to exert top-down control. Green crab presence altered the structure and stability of the food web. Additionally, we evaluated the effect of potential competitive interactions between native species and the green crab on the food web. Possible competitive interactions increased the effect the green crab had on the structure of the food web. Our results show that green crab invasion decreased food web stability by reducing the capacity of the food web to contain small- and long-range disturbances. These results contribute to the assessment and monitoring of the possible effects of other factors of global change. The system is less stable than before green crab invasion, and the drastic changes in community composition already recorded in rocky intertidal ecosystems in Patagonia are more likely to amplify through the food web.