Coastal geomorphology and oceanographic features shape subtidal benthic communities in management areas of central Chile

Abstract

Abstract The spatial variation in community structure among 30 areas for the management and exploitation of benthic resources (AMEBRs) in central Chile was assessed from surveys conducted during the same spring–summer season. One hundred taxa identified in the subtidal surveys were grouped into 10 functional groups. The influence and relative importance of external factors over benthic associations were assessed through nonmetric multidimensional scaling (NMDS) and path analysis. Three main categories of external factors were considered: ‘terrain traits’ (e.g. coastline exposure), ‘surface‐ocean conditions’ (e.g. sea surface temperature, SST), and ‘fishery‐related variables’ (e.g. cumulative landings). The NMDS revealed a strong association between benthic community structure and both terrain and surface‐ocean conditions (42% of variance explained by permutational multivariate analysis of variance), but not with fishery‐related variables. Assemblages typical of rocky substrates were associated with larger seasonal fluctuations in SST and surface chlorophyll a. The presence of soft‐bottom functional groups was associated with higher levels of surface fluorescence and larger seasonal fluctuations in a satellite‐derived proxy for river‐plume influence (nLw645). A path analysis model for hard‐bottom communities reached a 49% goodness of fit (GOF), with the presence of epifaunal filter‐feeders, grazers, predators, and scavengers being significantly correlated with leathery and corticated foliose algae, which in turn depend on the fraction of rocky substrate in the AMEBR; the fraction of rocky substrate is positively correlated with coastline exposure. The model for soft‐bottom communities reached a 52% GOF with the presence of infaunal filter‐feeders and epifaunal detritivores depending directly on SST and surface chlorophyll a. The fishery‐related variables considered in the model had no apparent effect on the structure of either type of subtidal community. These results provide a hierarchy of physical–biological associations determining the functional composition of subtidal benthic communities in management areas along central Chile. This knowledge may improve future assessments of ecosystem response to changes in environmental conditions and management strategies.