Marine pollution effects on the southern surf crab Ovalipes trimaculatus (Crustacea: Brachyura: Polybiidae) in Patagonia Argentina

•We described the effect of marine pollution on a subtidal keystone species.•Sites comprised high, moderate and non detected marine pollution in Patagonia.•As predicted, the southern surf crab was overtly harmed by marine pollution.•Ovalipes trimaculatus could be used as indicator of marine pollution.•Fluctuating asymmetry is a simple and cost-effective biomonitoring system.

We compared the carapace shape and thickness as well as the energy density of Ovalipes trimaculatus inhabiting areas comprising a gradient of marine pollution: high, moderate and undetected, in the Nuevo gulf (Patagonia Argentina). The carapace shape was evaluated by means of individual asymmetry scores (=fluctuating asymmetry) whereas the carapace thickness was assessed by measuring the carapace dry weight. The energy density was analyzed through its negative relationship with water content in muscle tissue. The individual asymmetry scores as well as the percentage of water content in muscle tissue were proportional to the marine pollution gradient, whereas the carapaces thickness did not differ among sampling sites. Our results are consistent with previous findings and demonstrate the direct effect of marine pollution on other taxa different from gastropods, cephalopods and polyplacophora and add to long-standing concerns about detrimental effects caused by marine pollution on the benthic community of the Nuevo gulf.