Analytical successional tools of fouling communities submitted to different light effects

The present study uses transition matrices to compare successional processes (colonization, disturbance, persistence and replacement) of fouling communities submitted to different light effects on Cabo Frio Island, a seasonal upwelling region. Twelve functional groups were identified, and differences in the transition probabilities shown by the matrices suggest a preference for the replacement property of functional groups, which indicates the facilitation successional mechanism. The probability of colonization of these groups differed according to the direction of the substrate, which caused a negative effect of light reduction on algae with a greater probability of disturbance (sensu species replacement), which is typical of a more stressful environment. Species of the same functional group replace each other through competition and herbivory, which promotes the distinction between earlier and later groups on the successional process. Successional trajectories evaluated through global transition matrices change at each time step because they depend on the species turnover rate, and therefore, they are informative of the changing processes of the community. The probabilistic rate of changes related to successional processes may be used to evaluate future conditions of fouling communities, and the deterministic components and stochastic elements will render these communities self-organizable

Latitudinal gradients in Atlantic reef fish communities: trophic structure and spatial use patterns

Trophic strategies and spatial use habits were investigated in reef fish communities. The results supported the hypothesis of differential use of food resources among tropical and higher latitude reef fishes, i.e. the number of species and relative abundance of fishes relying on relatively low-quality food significantly decreased from tropical to temperate latitudes. The species : genus ratio of low-quality food consumers increased toward the tropics, and was higher than the overall ratio considering all fishes in the assemblages. This supports the view that higher speciation rates occurred among this guild of fishes in warm waters. It was also demonstrated that density of herbivorous fishes (the dominant group relying on low-quality food resources) in the western Atlantic decreased from tropical to temperate latitudes. Spatial use and mobility varied with latitude and consequently reef type and complexity. Fishes with small-size home ranges predominated on tropical coral reefs. # 2004 The Fisheries Society of the British Isle

Nycthemeral and Monthly Occupation of the Fish Assemblage on a Sheltered Beach of Baía Norte, Florianópolis, Santa Catarina State, Brazil

Interpreting fish community records is challenging for several reasons, including the lack of past ichthyofauna data, the cyclical temporal variations in the community, and the methodology employed, which usually underestimates fish assemblages. The objective of this study was to describe short-scale and meso-scale (nycthemeral period and months, respectively) temporal variations in the ichthyofauna composition and structure of a sheltered beach of Baía Norte (Florianópolis, Santa Catarina state, Brazil), using a capéchade net. Samples were collected monthly for a period of 48 hours. During the period from December 2010 to November 2011, a total of 19,302 individuals belonging to 89 species and 39 families were captured. The number of individuals that were sampled during the day and/or night was dependent on the sampling month. On average, the daytime assemblage was more abundant and different in structure and composition than the nighttime assemblage. Of the eight species that had the highest Index of Relative Importance (%IRI), five had higher variations (ANOVA F) between the day and night than between the months. This finding reinforced the need for sampling during both the day and night. The capéchade net effectively captured demersal and pelagic individuals in a broad range of sizes

Benthic estuarine communities in Brazil: moving forward to long term studies to assess climate change impacts

Abstract Estuaries are unique coastal ecosystems that sustain and provide essential ecological services for mankind. Estuarine ecosystems include a variety of habitats with their own sediment-fauna dynamics, all of them globally undergoing alteration or threatened by human activities. Mangrove forests, saltmarshes, tidal flats and other confined estuarine systems are under increasing stress due to human activities leading to habitat and species loss. Combined changes in estuarine hydromorphology and in climate pose severe threats to estuarine ecosystems on a global scale. The ReBentos network is the first integrated attempt in Brazil to monitor estuarine changes in the long term to detect and assess the effects of global warming. This paper is an initial effort of ReBentos to review current knowledge on benthic estuarine ecology in Brazil. We herein present and synthesize all published work on Brazilian estuaries that has focused on the description of benthic communities and related ecological processes. We then use current data on Brazilian estuaries and present recommendations for future studies to address climate change effects, suggesting trends for possible future research and stressing the need for long-term datasets and international partnerships

Macroinvertebrates as indicators of human disturbances on sandy beaches: A global review

Sandy beaches are ecosystems under increasing human pressure that require efficient management and conservation strategies. Resident macroinvertebrates usually respond to disturbances by changing their behaviour and abundance, and therefore they may be used as indicator species using simple and low-cost monitoring strategies. We synthesize information from the scientific literature on the use of sandy beach macroinvertebrates as indicators of human disturbances operating at local scales. Response ratios were applied to perform a meta-analysis supported by empirical data to objectively assess the magnitude of human disturbances on beach fauna. The “compare and contrast” approach represented some 80% of the studies. Gradient assessments were performed by 16% of the studies, though without determining thresholds of disturbance. Long-term monitoring (encompassing more than two years) was the general approach used in studies about harvesting, but it was not used when assessing other type of disturbances. Causality relationships and mechanisms underlying impacts were rarely assessed. Useful indicators to specific human disturbances were: 1) ghost crabs, which indicate the negative effects of vehicle traffic and nourishment; 2) talitrids as indicators of trampling and mechanical cleaning; and 3) clams as indicators of harvesting. As beaches are affected by multiple stressors acting simultaneously, the relative importance of each one has been difficult to reveal. It remains a priority to identify how different human disturbances are affecting macroinvertebrates under a range of diffuse impacts. Such results would allow for the depiction of patterns and future studies should prioritize gradient analyses and manipulative experiments to provide thresholds of specific stressors and mechanisms of impacts