Intraspecific diet shift of Macoma balthica during community reassembly in an estuarine intertidal flat Francesca Rossi a, * , Jack J. Middelburg b, c a ECOLAG UMR 5119e University of Montpellier II, Place E. Bataillon, Montpellier 34000, France b Netherlands Institute of Ecology (NIOO-KNAW), Centre for Estuarine and Marine Ecology, P.O. Box 140, 4400 AC Yerseke, The Netherlands c Faculty of Geosciences, Utrecht University, P.O. Box 80.021, 3508 TA Utrecht, The Netherlands article info Article history: Received 9 August 2010 Accepted 14 February 2011 Available online 24 February 2011 Keywords: trait plasticity ecological succession feeding behaviour food webs hypoxia tidal flats abstract During community reassembly, consumers may express adaptive feeding behaviour in response to the presence of other species or according to their development. During the community reassembly after hypoxia of a temperate estuarine intertidal area, we quantified the microphytobenthos contribution to the diet of the three numerically dominant macrofauna consumers, using 13 C-carbon tracing experi- ments. We then explored the relationships between their size and the microphytobenthos contribution to their diet. The polychaetes Hediste diversicolor and Pygospio elegans did not show a clear pattern of diet shift. Conversely, at a late stage of community reassembly, there was a dramatic decrease in the contribution of benthic microalgae to the diet of the clam Macoma balthica within the juvenile specimens (5 mm), which were recolonising the sediment. The contribution of microphytobenthos decreased with the size (r ¼0.81, n ¼ 18) and the largest juveniles incorporated benthic microalgal carbon similarly to their co-specific adults found in the undisturbed areas. Including both juveniles and adults, the size-diet relationship of M. balthica followed an inverse logarithmic curve during community reassembly. Such shape differed from the linear relationship based on the natural abundance of stable carbon isotope as previously collected in the undisturbed surroundings. Our study provides evidence of diet shift during community reassembly and suggests that such diet shift might follow both consumer development in the recolonising areas and other processes related to successional stages. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Many organisms express variability in morphological and behavioural traits in response to biotic and abiotic aspects of their environments (Agrawal, 2001; Piersma and Drent, 2003; Valladares et al., 2006). For example, on the marine rocky shores, the barnacle Balanus glandula may modify the form of the cirrus in response to wave exposure (Marchinsko, 2003). This variability may occur within the lifespan of a single individual or across generations (Miner et al., 2005). Considerable morphological and behavioural changes may also take place during individual development (Hentschel, 1998). In turn, the altered traits may greatly change the ecological role that species play in the community and in the ecosystem, by modifying species interactions and, as a conse- quence, community dynamics (Bolker et al., 2003; Werner and Peacor, 2003). Changes in feeding behaviour, for instance, may alter the strength of trophic interactions and thus food web dynamics (Cohen et al., 1993; Abrams, 1995). Moreover, they can modify species contribution to carbon and nutrient cycles, by regulating resource uptake and resource-niche complementarity (Miner et al., 2005). Information on diet shift may thus critically increase the precision and accuracy of ecosystem models that attempt to predict how species diversity may affect ecosystem functioning (Miner et al., 2005; Thuiller et al., 2005; Valladares et al., 2006). Changes in the feeding behaviour may often occur in the marine coastal environment, where both invertebrates and fish may vary their food intake in response to biological interactions (e. g. predation, availability of food) or to variable physical conditions such as hydrodynamics (Marchinsko, 2003) and during develop- ment (Olson, 1996; Hentschel, 1998; Huss et al., 2008). The mac- rofauna consumers inhabiting estuarine and marine sediments may, for instance, change feeding behaviour both during develop- ment (Hentschel, 1998; Rossi et al., 2004) and in response to a variety of ecological processes (Taghon et al., 1980; Marsh and Tenore, 1990; Skilleter and Peterson, 1994; Ferner and Jumars, 1999). Macrofauna consumers play a fundamental functional role * Corresponding author. E-mail address: francesca.rossi@univ-montp2.fr (F. Rossi). Contents lists available at ScienceDirect Estuarine, Coastal and Shelf Science journal homepage: www.elsevier.com/locate/ecss 0272-7714/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.ecss.2011.02.008 Estuarine, Coastal and Shelf Science 92 (2011) 496e501