Living under Ulva canopy: The case of the scavenger snail Buccinastrum deforme in a eutrophic macrotidal bay in Patagonia (Argentina)

Eutrophication results in macroalgal blooms with usually negative effects on the marine communities; nevertheless, positive and neutral effects have also been reported. We hypothesized that the macroalgal canopy plays an important role in secondary consumers like the scavenger snail Buccinastrum deforme through amelioration of physical stress and through carrion retention below the canopy. We evaluated if the canopy provided by Ulva spp. affected the habitat conditions and population traits of B. deforme in a macrotidal coastal system of North Patagonia. Our results indicated that the Ulva canopy was associated with lower desiccation, a higher abundance of crab carrions, and with larger and heavier snails. We did not, however, find differences in the sex ratio, the juvenile, and total density of B. deforme between microhabitats with and without an Ulva canopy. These results suggest that macroalgal canopy of Ulva has a modest ecological effect on B. deforme.