The importance of shell debris for within-patch heterogeneity and disturbance-recovery dynamics of intertidal macrofauna

Abstract

Shell debris increases habitat diversity and ecological heterogeneity, stabilizing sediments and providing substrate for encrusting and epifaunal animals and protection against predation. However, how shell debris influences disturbance-recovery dynamics in different habitats has not been evaluated. We experimentally tested the effects of shell debris on early colonization of macroinvertebrates into defaunated patches across 12 sites along a mud-to-sand gradient. The addition of shell debris enhanced species richness compared to plots without shells and increased variability in the local contributions to beta-diversity, mostly at the muddier sites. The variation in the strength of these effects along the mud gradient highlights the effects of shell debris on community structure and how the muddying of coastal sediments shifts species composition. Loss of shellfish and burying of shells with elevated rates of sedimentation diminishes the role of small-scale sediment heterogeneity for sustaining beta-diversity in low-energy environments.