Feeding niche preference of the mudsnail Peringia ulvae

The feeding behaviour of Peringia ulvae was studied with the aim of assessing its preferential feeding niche (habit) as well as its potential role in controlling or preventing the occurrence of macroalgal blooms. Both these aspects were studied in the Mondego estuary because of the clear long-lasting eutrophication process that favours the growth of two opportunistic macroalgae, Gracilaria spp. and Ulva spp., over the local beds of the macrophyte Zostera nolteii, which is another potential food source. All three species, both with and without periphyton, were used as a single food source in feeding experiments to assess different feeding parameters of the gastropod. Sediment with microphytobenthos was used together with the latter three species in feeding niche preference experiments. None of the food types provided were resistant to grazing. Higher levels of grazing occurred on Ulva spp. (apical parts) and Z. nolteii, both with periphyton. The presence of periphyton did not change grazing rates. When a choice between each food type was offered, the sediment was clearly the feeding niche preferred by the snails. As P. ulvae spent more time on the sediment (preferred feeding niche), the hypothesis that it has a role in preventing macroalgal blooms was not supported.