Non-lethal human disturbances are often drivers of change in animal population and community structure. To gauge their severity, short-term behaviour (e.g. avoidance and habituation) has been argued to be a sensitive measure. However, many of these behavioural changes may occur only if disturbance-free habitat is readily accessible. In coral-reef fish, we tested whether human disturbances from intensive (i.e. loud music, swimming, snorkelling, splashing and fish feeding by numerous visitors) tourist visitations resulted in assemblage structure shifts led by shortterm behaviour. We monitored fish assemblage before, during and after tourist visitations to monitor changes associated with behaviour. Additionally, we monitored two adjacent reefs not visited by tourists because of difficult approach by boat. We posited that if short-term benefits of relocating to disturbance-free habitat outweigh the costs of tolerating disturbances, fish assemblage structure should shift along with tourist visitation levels. By contrast, if sensitive species are unable or unwilling to relocate, we predicted greater levels of assemblage heterogeneity between the visited and control reefs. Our results showed that in situ human visitations led to significant shifts in assemblage structure, resulting from short-term behavioural changes. Additionally, we showed significant between-reefs differences, whereby control reefs were characterised by higher species richness, larger fish sizes and variations in relative trophic guild prevalence. Our results suggest that short-term relocations to adjacent disturbance-free reefs may not mitigate the effects of human disturbances.
Consequences of reef phase shifts on fish communities remain poorly understood. Studies on the causes, effects and consequences of phase shifts on reef fish communities have only been considered for coral-to-macroalgae shifts. Therefore, there is a large information gap regarding the consequences of novel phase shifts and how these kinds of phase shifts impact on fish assemblages. This study aimed to compare the fish assemblages on reefs under normal conditions (relatively high cover of corals) to those which have shifted to a dominance of the zoantharian Palythoa cf. variabilis on coral reefs in Todos os Santos Bay (TSB), Brazilian eastern coast. We examined eight reefs, where we estimated cover of corals and P. cf. variabilis and coral reef fish richness, abundance and body size. Fish richness differed significantly between normal reefs (48 species) and phase-shift reefs (38 species), a 20% reduction in species. However there was no difference in fish abundance between normal and phase shift reefs. One fish species, Chaetodon striatus, was significantly less abundant on normal reefs. The differences in fish assemblages between different reef phases was due to differences in trophic groups of fish; on normal reefs carnivorous fishes were more abundant, while on phase shift reefs mobile invertivores dominated.
Studies in microbiology have long been mostly restricted to small spatial scales. However, recent technological advances, such as new sequencing methodologies, have ushered an era of large-scale sequencing of environmental DNA data from multiple biomes worldwide. These global datasets can now be used to explore long standing questions of microbial ecology. New methodological approaches and concepts are being developed to study such large-scale patterns in microbial communities, resulting in new perspectives that represent a significant advances for both microbiology and macroecology. Here, we identify and review important conceptual, computational, and methodological challenges and opportunities in microbial macroecology. Specifically, we discuss the challenges of handling and analyzing large amounts of microbiome data to understand taxa distribution and co-occurrence patterns. We also discuss approaches for modeling microbial communities based on environmental data, including information on biological interactions to make full use of available Big Data. Finally, we summarize the methods presented in a general approach aimed to aid microbiologists in addressing fundamental questions in microbial macroecology, including classical propositions (such as "everything is everywhere, but the environment selects") as well as applied ecological problems, such as those posed by human induced global environmental changes.
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