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Climate change is predicted to lead to more extreme weather events, including changes to storm frequency, intensity and location. Yet the ecological responses to storms are incompletely understood for sandy shorelines, the globe’s longest land-ocean interface. Here we document how storms of different magnitude impacted the invertebrate assemblages on a tidal flat in Brazil. We specifically tested the relationships between wave energy and spatial heterogeneity, both for habitat properties (habitat heterogeneity) and fauna (β-diversity), predicting that larger storms redistribute sediments and hence lead to spatially less variable faunal assemblages. The sediment matrix tended to become less heterogeneous across the flat after high-energy wave events, whereas β-diversity increased after storms. This higher β-diversity was primarily driven by species losses. Significantly fewer species at a significantly lower density occurred within days to weeks after storms. Negative density and biomass responses to storm events were most prominent in crustaceans. Invertebrate assemblages appeared to recover within a short time (weeks to months) after storms, highlighting that most species typical of sedimentary shorelines are, to some degree, resilient to short-term changes in wave energy. Given that storm frequency and intensity are predicted to change in the coming decades, identifying properties that determine resilience and recovery of ecosystems constitute a research priority for sedimentary shorelines and beyond.

Sediment characteristics, especially grain size, are usually considered the most important variables affecting Uca distribution, mainly due to its close relationship with mouth appendage morphology. The aim of this study was to verify, from an assemblage perspective, if sediment is the most important variable affecting Uca species distribution, and if mouth appendage morphology (setae type and curvature) would be related to habitat occupancy. Niche metrics and null model approaches were used to assess and test the hypothesis. The relevance of spoon-tipped setae curvature to Uca distribution was verified for the first time. A fragmented mangrove area was divided into seven subareas, and sampling of crabs and environmental variables took place in June and November 2010. Of 10 species recorded for Brazil, seven were found in the study area: U. burgersi, U. cumulanta, U. leptodactyla, U. maracoani, U. rapax, U. thayeri and U. uruguayensis. Multivariate analysis showed that sediment grain size and the presence of vegetation were the most important variables explaining distribution, reinforcing results commonly obtained by univariate approaches. The overlap of habitat occupancy was generally low and no relationship between mouth appendages was found with breadth and overlap measures. Contrary to predictions, most non-random overlap values were lower than expected by chance, suggesting that interspecific competition might influence species distribution. Also, variables such as the presence of vegetation are important and influence crab distribution, limiting the potential distribution that would be predicted by mouth adaptations alone. Thus, the use of these adaptations as surrogates of fiddler crab distribution is not recommended.

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Variation partitioning is an important tool to investigate the importance of spatial structure to species distribution in communities, but its use is lacking in marine ecosystems. The influence of rare species and the level of taxonomic resolution are important features to be considered when planning sampling designs and efforts for community studies. We tested the significance of spatial and environmental components to species distribution of a polychaete community, considering how the results varied among models with increasingly rare species (and contrasting metrics), and among models with distinct taxonomic levels. For all models evaluated, both spatial and environmental components significantly explained the structure of species distribution. However, spatial processes explained a higher percentage of variance than environmental ones in almost all models. The inclusion of rare species did not influence the outcome in most models, with the exception of a Chi‐square distance model with all species included. Family taxonomic level was sufficient to detect the relative contribution of both components, but the number of environmental variables included in the model was higher for the genus level. The influence of rare species was related to the metric applied to the analysis. If weight to rare species is not desirable, the use of a few dominant species coupled with the Hellinger function can provide a good surrogate to the whole sampled community in variation partition analysis. The genus level is suggested as an appropriate taxonomic level with which to evaluate the relevance of spatial and environmental components in polychaete community studies.

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Polychaetes are important components of trophic webs in sandy beaches, mainly due to their abundance and diversity of feeding modes, acting as detritivores or primary/secondary consumers. We characterized diets of several polychaete species from intertidal sandy beaches by gut content evaluation. Diet breadth (Levins Index) was calculated for each species to evaluate the influence of different feeding strategies on this metric. Diatom composition was also assessed to verify the relevance of microphtyobenthic primary production to macrobenthic feeding on sandy beaches and its relationship with feeding strategies. A total of 2583 guts from 17 species were evaluated. Diet information is compared with literature, and added to taxa with previously unknown feeding habit. Diet breadths were generally low, but surface deposit feeders had the highest values. Scolelepis squamata guts were dominated by foraminfera, which may either be an specialization or local conditions. Subsurface deposit feeders usually had few items and lower breadths, highlighting the importance of organic matter to this guild. Diatoms were frequently found, and benthic were more frequently consumed than planktonic ones. The high numbers of benthic diatoms found for some species highlight the importance local food sources to sandy beach food webs.

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