Small-scale spatial structure of Baltic Sea zoobenthos—inferring processes from patterns

In this study, we describe small-scale (6 cm–5 m) spatial patterns of four dominating infaunal taxa in the northern Baltic Sea, with the objective to construct hypotheses about pattern-generating processes . Two neighbouring sites, differing in their physical environment, were extensively sampled, and the distributions of adults and juveniles were analysed with spatial autocorrelograms. Relationships between taxa and size classes were studied with correlations at different scales. As similar spatial patterns and correlations appeared at both sites, this suggests that biotic interactions rather than physical factors were responsible for the patterns. We found that several taxa exhibited patchy distributions at the studied scales. In the case of juvenile Monoporeia affinis (Amphipoda) and juvenile Corophium volutator (Amphipoda), we propose that positive intragroup interactions were responsible for the patterns. The correlation analyses suggested that areas with high densities of adult Macoma balthica (Bivalvia) were avoided by juvenile conspecifics and adults of M. affinis and C. volutator, probably because adult M. balthica reduced the amount of detritus in the surficial sediment.