Relationships Between Environmental Conditions And Fish Assemblages In Tropical Savanna Headwater Streams

Abstract

Riparian vegetation plays an important role in providing energy to small watercourses and maintaining ecological processes through organic matter input and together with hydrological and geomorphological watercourse characteristics influence on fish assemblages. The goal of this paper was partitioning and quantifying the influence of riparian zone (type of riverbank substrate, bank slope, type of riparian vegetation cover and percentage of riparian vegetation cover on the main channel), physical habitat (stream channel width and depth, type of substrate and aquatic habitat in channel, water velocity and organic matter), water quality (turbidity, temperature, conductivity, pH, dissolved oxygen and chlorophyll concentration) and spatial variables (linear distances between sampled points) on fish assemblages (richness and abundance per species) in headwater streams of the Upper Paraná River basin, Central Brazil. For this purpose, it was performed a variation partitioning analysis between riparian, physical habitat, water and spatial variables sets and a Redundancy Analysis to quantify the influence of variables on the fish assemblages. Only the physical habitat and water quality variables influenced the fish assemblages (richness and abundance per species). Freshwater fish assemblages are structured by variables related to both water quality and riparian vegetation 1-6. In this sense, warmer waters exhibit higher fish abundance and biomass while highly oxygenated waters may lead to greater species diversity 7-9. Riparian vegetation is a transitional semiterrestrial system 10 that provides energy in watercourses through the input of organic matter 2. Leaves deposited on the watercourse bed contribute indirectly to fish food because they act as a substrate for numerous microorganisms 11 and insects 12,13. In addition, riparian trees and roots restrict channel widening, cause channel deepening and add coarse woody debris favoring fish concealment and channel complexity. The influences of water and riparian vegetation on fish assemblages are not independent 2,10,14,15 ; that is, riparian vegetation may directly or indirectly influence water variables 16. For example, water temperature is directly influenced by riparian vegetation, which regulates the watercourse insolation level 17,18 and influences primary production 19. Conversely, channel depth and substrate heterogeneity are indirectly influenced by riparian vegetation because the riparian zone regulates the entry of sediment that can be deposited into the watercourse 10,20,21. Another factor that should not be neglected is the spatial factor (e.g., the river network), which includes geographical barriers that hamper or prevent species migration between locations. Abundance and richness are diversity metrics that are spatially structured 22-28. Spatial factors are a consequence of the geological and local climatic influence on the streams in a river network 29-31 and the position of the watercourse along a longitudinal gradient (upstream-downstream 32) for the 1 st...

Partitioning Among Niche and Neutral Explanations for Metacommunity Patterns in Cerrado Stream Fish Communities

“…However the ichthyofauna show a greater correlation with environmental conditions than spatial processes, suggesting that Species Sorting is the key mechanism in structuring fish communities (37% of the metacommunity analyzed by Cottenie [3] show this result). This result does not rule out the occurrence of dispersion [3,7,47–49], but reinforces the idea that dispersion occurs locally and weakly (negative relation with the spatial eigenvectors maps).…”

“…The interaction of space (dispersion) and environment in the structuring of metacommunities is attributed solely to the Mass Effects model [2]. However is it not possible to separate these two mechanisms, and metacommunities that are related to space and environment are understood as interaction between Species-Sorting and Mass Effects [3,47–49]. This interaction was found in 29% (46) of the communities analyzed by Cottenie [3] and also found for Amazonian fish [7,47–49].…”

“…However is it not possible to separate these two mechanisms, and metacommunities that are related to space and environment are understood as interaction between Species-Sorting and Mass Effects [3,47–49]. This interaction was found in 29% (46) of the communities analyzed by Cottenie [3] and also found for Amazonian fish [7,47–49]. However the ichthyofauna show a greater correlation with environmental conditions than spatial processes, suggesting that Species Sorting is the key mechanism in structuring fish communities (37% of the metacommunity analyzed by Cottenie [3] show this result).…”

What controls fish functional diversity patterns in Colombian Andean streams?

“…It is well known that in aquatic ecosystems, temperature, hydraulic, physical and chemical conditions influence fish dispersal and species diversity (Buisson et al., 2008). Freshwater fish assemblages are structured by variables related to water quality, riparian vegetation (Teresa & Romero, 2010) and physical habitat (Vieira & Tejerina‐Garro, 2020). For example, riparian vegetation provides energy to the system because the input of organic matter deposited (e.g.…”

Elements of fish metacommunity structure in Neotropical freshwater streams

“…A sampled stream was included in the database if it met the following requirements: (a) fish collection was carried out in a 1st-3rd order stream; (b) the sampled stream stretch was >50 m and georeferenced; (c) the fish sampling method used was electric fishing, trawl nets, and/or hand nets; (d) sampling comprised of a single sample site per stream; (e) a stream-specific species list was available; (f) environmental variables (turbidity, conductivity, pH, dissolved oxygen, water velocity, stream channel depth and width) were measured in situ at three or more points in each stream; (g) fish sampling, transport, and preservation of sampled specimens were authorized by the Sistema de Autorização e Informação em Biodiversidade (SISBIO), Instituto Chico Mendes de Conservação da Biodiversidade, Ministerio do Meio Ambiente; and (h) streams were located in the same type of vegetation cover (the Brazilian savannah called Cerrado Biome, in this case). Constraining the data for streams under the same vegetation condition ensured that the features linked to vegetation type, such as substrate and temperature, are unlikely to differ greatly, so decreasing the amount of variability(Vieira & Tejerina-Garro, 2020). The fish fauna dataset is available at: https://doi.org/10.5061/dryad.m63xs j3z7.Using the specialized literature, component species were classified by trophic guild (detritivores, insectivores, and omnivores).…”