Testing the effects of nutrient additions on mudflat macroinfaunal assemblages in the presence and absence of shorebird predators

Abstract

An issue that is of increasing concern worldwide relates to the possibility that areas subject to conservation agreements, owing to the resident and migratory bird populations they support, will be adversely affected by attempts to reduce organic inputs into nearshore environments. In the present study, we investigated the effects of nutrient additions and shorebird exclusion on the infaunal assemblages of an intertidal mudflat. Where responses to nutrient additions were observed they only occurred in the high-dose treatments, indicating that a high nutrient loading is required before infaunal responses are initiated at this site. There was no evidence to support the idea that nutrient additions would only stimulate macroinfaunal assemblages where shorebird foraging was reduced. Instead, nutrient additions were detectable separately from any effects of shorebird predation and, contrary to expectations, appeared to be of more importance than shorebird predation in this environment. There was also no evidence to suggest that shorebird predation has a strong interaction with the infaunal prey assemblage and, although further studies will be needed to support this statement, it is possible that moderate changes in nutrient status will not impact on the shorebird populations at this site.