Search

Environmental influences on species' functional traits are important ecological issues to assess biodiversity. Relationships among fish abundance, their functional traits, and environmental conditions across different levels of anthropogenic impacts in a tropical Brazilian river were evaluated. We combined RLQ and fourth-corner methods, utilizing local environmental variables and the Human Footprint Index (HFI) as a human activities indicator. Three HFI levels (High, Intermediate, and Low) and short-term (1993–2009) impact changes at each location were assigned. Fish with internal fertilization and small body sizes were strongly associated with high HFI scores. Grass-dominated riparian areas were common in altered locations, whereas less altered localities exhibited the riparian cover dominated by trees. Highly altered areas showed high HFI, grass-covered riparian zones, and small-sized species with internal fertilization (e.g., Cyprinodontiformes like Poecilia vivipara, Poecilia reticulata, and Phalloceros caudimaculatus). In contrast, less altered areas had tree-lined riparian zones and medium to large-sized species with external fertilization and diverse traits. Underlying deterministic processes shape species distribution, tied to environment and traits. Filtering of traits in the most altered locations may favor small-sized species with internal fertilization. This approach, utilizing HFI and local variables to assess trait–environment relationships of riverine fish, facilitates understanding organisms' responses to environmental constraints. [ABSTRACT FROM AUTHOR]

As human-induced environmental changes reduce niche opportunities from global to local scales, permanent shifts in species traits alter ecosystem processes. Disentangling multiscale mechanisms driving temporal changes in coastal fish biodiversity is thus critical to conservation aims. From seasonal to multiyear periods, we investigated how local environmental variation and landscape features shape temporal beta diversity (abundance-based and trait-based dissimilarities, and their components of replacement and nestedness) per zones in bays and coastal lagoons, Southeastern Brazil. At larger temporal dimensions, unaccounted processes in individual systems influenced primarily taxonomic dissimilarity, whereas functional responses to variation in marine influence varied between types of system and zones. From 2 years to seasons, taxonomic and functional dissimilarities decreased with abundance-based species replacement, and both trait-based components, respectively. Replacement processes were primarily related to marine influence (transparency, salinity, pH, and tidal phase) at larger temporal dimensions, and habitat availability (mangroves and nearby estuaries) and complexity (forest cover and landscape urbanization) in seasons. Seasonal variations in tidal phase (lower) and pH (higher), respectively, promoted taxonomic (abundance gradients) and functional (fish trait loss) nestedness under shorter environmental gradients. Spatial and temporal balances between marine influence, habitat quality, and seascape connectivity drive temporal dissimilarities in coastal fish assemblages. [ABSTRACT FROM AUTHOR]

Shallow coastal habitats are ruled by fluctuating environmental conditions, which lead to shifts in fish communities. Functional groups of habitat use and trophic strategy were used to address the responses of fish composition and diversity, since comparisons of rich tropical systems are often complex through species-based approaches. We hypothesized that fish groups will have specific affinities in response to the prevailing environmental conditions, especially those reflecting the prevalence of oceanic or estuarine conditions, where guilds of habitat use would perform better as indicators. Despite the importance of other environmental factors (i.e. temperature and transparency), salinity was the key structuring factor irrespective of the coastal lagoon. Although harbouring the greatest biomass of piscivores, the harsh environmental conditions at Araruama lagoon were related to low diversity. A great number of indicator species, typically of marine affinity, was found at the Saquarema lagoon, probably due to the continuous and broad connection to the sea leading to the predominance of euhaline conditions. Despite the presence of non-native species (i.e. Oreochromis niloticus), the Maricá lagoon function as an important refuge for freshwater groups. Our results stressed the key role played by coastal lagoons of varied water conditions in supporting fish diversity at regional levels. [ABSTRACT FROM AUTHOR]

Coastal ecosystems can vary considerably in their habitat characteristics and environmental conditions, resulting in divergent fish community structures. However, comparisons among coastal systems, such as oceanic beaches, bays and coastal lagoons, have not been thoroughly evaluated. We test the hypothesis that coastal systems that differ in wave exposure, habitat structure, salinity gradients and productivity show different assemblages and feeding guilds. The fish assemblages were significantly different among the systems. The bays had the largest number of species, whereas the lagoons had the highest numerical abundance and biomass. The planktivorous guild dominated in numerical abundance in all systems, whereas the opportunists dominated in biomass. The benthivores contributed greatly in abundance to the bays, the opportunists to the coastal lagoons, and the hyperbenthivores to the oceanic beaches. Water transparency and temperature explained a small portion of the variation in the community structure. This study highlighted the complex role that local factors have on the distribution of fishes at the species and trophic levels. These approaches were efficient to describe the structure and functioning of the assemblages in these different coastal systems. This should be viewed as essential for any comparisons of coastal systems, and in particular for conservation planning. [ABSTRACT FROM AUTHOR]

Coastal lagoons are naturally stressed systems and experience changes in environmental conditions because freshwater inputs change environmental variables, mainly the salinity. We hypothesized that fish assemblages would change in structure and richness in three tropical lagoons that had different salinity ranges (a hyperhaline lagoon, 36-54; a euhaline lagoon, 16-40; and a mesohaline lagoon, 8-34). The assemblage structure differed among the three lagoons, and changed seasonally only in the mesohaline lagoon with the biomass being comparatively higher in summer than that in winter. The four environmental variables (salinity, temperature, turbidity and depth) explained a significant proportion of the variance, with salinity having the most significant effect (≈ 10% of the explained variation) on fish assemblage structure. The mesohaline lagoon, with the widest salinity range (from estuarine to marine conditions) and more loads of nutrient brought by small rivers' inflows, was the most abundant (in fish number and biomass) system. The euhaline lagoon, with a salinity range closest to marine conditions, had the highest species richness as opposed to the hyperhaline lagoon that appeared to limit species abundance and richness, probably due to the stress of high salinity. [ABSTRACT FROM AUTHOR]