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Dryad

Prominent grazing rates and feeding preferences of an abundant exotic benthic herbivore in the western Mediterranean Sea

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Dec 11, 2024 version files 25.30 KB

Abstract

Exotic herbivores can exert profound impacts on terrestrial communities, but their ecological effects on marine habitats are not sufficiently quantified. The exotic crab Percnon gibbesi, which is spreading throughout the Mediterranean Sea, grazes almost exclusively on benthic macrophytes, providing an opportunity to study the potential impacts of herbivores in the marine realm. Here, we first quantified the abundance of P. gibbesi in the Balearic Islands in 2023 (67 individuals 100 m-2), which was approximately 33 times greater than that recorded previously. We then performed a feeding preference experiment using common native and invasive macroalgae from the Mediterranean Sea. The per capita grazing rate of P. gibbesi (average 3.83 WW g crab -1 day-1) was higher than that recorded for most native herbivorous species in the Mediterranean. The estimated daily grazing rates for P. gibbesi average 23.98 kg WW macroalgae ha-1 d-1, value that corresponds to an average of 5.58% of the total macroalgae production in this area. Our experiment revealed clear preferences of P. gibbesi for three species of macroalgae, which were not explained by the nutritional content. Overall, our results indicate that the ecological impacts of this exotic herbivore on Mediterranean communities could be substantial and, until now, unreported.