Environmental and spatial effects on coastal stream fishes in the Atlantic rain forest

Abstract

Contemporary and historical factors influence assemblage structure. The environmental and spatial influences acting on fish organization of rain forest coastal streams in the Atlantic rain forest of Brazil were examined. Fish (and functional traits such as morphology, diet, velocity preference, body size), environmental variables (pH, water conductivity, dissolved oxygen, temperature, stream width, flow, depth, substrate), and altitude were measured from 59 stream reaches. Asymmetric eigenvector maps were used to model the spatial structure considering direction of fish movements. Elevation played an important role-fish abundance, biomass, and richness all decrease with increasing elevation. Fish communities are influenced by both environmental and spatial factors, but downstream movements were shown to be more important in explaining the observed spatial variation than were bidirectional and upstream movements. Spatial factors, as well as environmental variables influenced by the spatial structure, explained most of the variation in fish assemblages. The strong spatial structuring is probably attributable to asymmetric dispersal limitation along the altitudinal profile: Dispersal is likely to be more limiting moving upstream than downstream. These fish assemblages reflect scale-dependent processes: At the stream-reach scale, fish respond to local environmental filters (habitat structure, water chemistry, and food supply), which are in turn influenced by a larger scale, namely the altitudinal gradient expected in steep coastal mountains. Thus, environmental drivers are not independent of spatial factors, and the effects of local factors can be confounded across the altitudinal gradient. These results may have implications for conservation, because downstream reaches are often neglected in management and conservation plans.Abstract in Portuguese is available with online material. K E Y W O R D Saltitude, asymmetric eigenvector maps, dispersal limitation, environmental filtering, fish metacommunities, fish movement, tropical streams conservation, variation partitioning

Environmental diagnosis of water quality in situ and ex situ in streams in Upper Paraná River Basin, Brazil

“…However, Piravevê had a lower proportion of agriculture and a higher proportion of pasture areas in relation to the other streams. The replacement of vegetation cover around aquatic environments by agricultural areas is a major environmental problem, mainly because water bodies are unprotected from pollutants (Gonçalves et al 2019). Dense vegetation cover has a barrier function, dampening the transport of sediments and pollutants into the stream during periods of increased rainfall, thus avoiding silting and imbalance in the structure and functioning of the ecosystem (Castro and Souza 2013;dos Santos et al 2020).…”

“…In this sense, the fragility of the vegetation around the streams leaves the environment more exposed and vulnerable to contaminants, compromising the health of aquatic biota, especially the sh. Several studies have reported the serious consequences of reducing plant cover for the health of aquatic organisms, which may cause a reduction in species due to the degradation of environmental quality (Viana et al 2018(Viana et al , 2019Ribeiro Junior et al 2018;Gonçalves et al 2019).…”

“…Zhang et al (2019) highlighted that evaluating native sh species in situ in aquatic environments not only re ects toxic impacts, but also reveal their ability to adapt to unfavorable conditions in the environment. Several anthropic activities alter land use near aquatic environments, reducing the connection between riparian vegetation cover and the aquatic environment (Gonçalves et al 2019).…”

“…The changes in the landscape around rivers and streams lead to the formation of homogeneous and unhealthy vegetation, which directly affects and reduces local biodiversity that depend on good environmental quality for its maintenance (Roa-Fuenteset al 2019;Zeni et al 2019). Being that, habitat fragmentation is considered one of the main threats to biodiversity (Zeni et al 2019;Gonçalves et al 2019).…”

Ichthyofauna of Tributary Streams of the Cinzas River Basin, Paranapanema River, Brazil

“…The impacts of anthropogenic activities have resulted in severe damage to Neotropical aquatic ecosystems, significantly affecting hydrology and local biological diversity (Lobo et al 2015, Gonçalves et al 2019. The sequence in the streams' structure can be broken due to anthropic interferences, capable of generating discontinuities in diversity patterns (Walker et al 2019).…”