The effects of habitat heterogeneity at distinct spatial scales on hard-bottom-associated communities

Abstract

For marine benthic communities, environmental heterogeneity at small spatial scales are mostly due to biologically produced habitat heterogeneity and biotic interactions, while at larger spatial scales environmental factors may prevails over biotic features. In this study, we investigated how community structure and 3-diversity of hard-bottom-associated meio-and macrofauna varied in relation to small-scale (cm-m) changes in biological substrate (an algae "turf" dominated by the macroalgae Gdidium sp., the macroalgae Caulerpa racemosa and the sponge Hymeniacidon heliaphile) in a rocky shore and in relation to larger-scale (10's m) changes in environmental conditions of the same biological substrate (the macroalgae Bostrychin sp) in different habitats (rocky shore vs. mangrove roots). Results showed that both substrate identity and the surrounding environment were important in structuring the smaller-sized meiofauna, particularly the nematode assemblages, whereas the larger and more motile macrofauna was influenced only by larger-scale changes in the surrounding ecosystem. This implies that the macrofauna explores the environment in a larger spatial scale compared to the meiofauna, suggesting that effects of spatial heterogeneity on communities are dependent on organism size and mobility. Changes in taxa composition between environments and substrates highlight the importance of habitat diversity at different scales for maintaining the diversity of the associated fauna.