Change in beta diversity of riverine fish during and after supra-seasonal drought

Abstract

Context A core theme in ecohydrology is understanding how hydrology affects spatial variation in the composition of species assemblages (i.e., beta diversity). However, most empirical evidence is from research in upland rivers spanning small spatial extents. Relatively little is known of the consequences of hydrological variation for beta diversity across multiple spatial scales in lowland rivers. Objectives We sought to examine how spatial variation in hydrology and fish beta diversity within and among rivers changed over time in response to intensification and cessation of hydrological drought. Methods We used monitoring data of fish assemblages, coupled with hydrological and biophysical data, to test how spatial variation in hydrology and multiple components of fish beta diversity in lowland rivers of the Murray—Darling Basin (Australia) varied across spatial scales during contrasting hydrological phases. Results Spatial variation in hydrology among rivers declined with increasing duration of drought before increasing during a return to above-average flows. Spatial variation in hydrology within rivers did not show consistent changes between hydrological phases. Beta diversity among and within rivers showed variable, river-specific changes among hydrological phases for both incidence- and abundance-based components of assemblage composition. Conclusions Inconsistent hydrology—beta diversity patterns found here suggest that mechanisms and outcomes of drought and flooding impacts to beta diversity are context-dependent and not broadly generalisable. Our findings indicate that hydrological fluctuations occurring in the Murray—Darling Basin in the period analysed here did not cause significant or consistent homogenisation or differentiation of freshwater fish assemblages.

Regional Diversity Trends of Nearshore Fish Assemblages of the Upper San Francisco Estuary

“…Freshwater inflow is one major environmental factor that can affect many abiotic and biotic factors regulating fish beta diversity in estuarine systems. Past studies have documented that high inflow can increase hydrological connectivity, enhance dispersal, homogenize environmental conditions, and often results in decreased fish beta diversity (De Macedo-Soares et al 2010;Rolls et al 2022). Results from our study concur with these findings as because regional beta diversity significantly declined as inflow levels increased, and was primarily driven by decreases in balanced variation in species abundance, suggesting that a reduction in environmental filtering processes was the primary driver.…”

Wild Foods Are Positively Associated with Diet Diversity and Child Growth in a Protected Forest Area of Madagascar

“…Suboptimal WASH conditions can suppress child growth through increases in enteric infection [ 67 ]. Further, drought concentrates the pathogen load in river systems and impedes river discharge with effects on beta diversity [ 68 ]. More research is needed to understand the full picture of freshwater fisheries, WASH, and river ecosystem fragility in this site.…”

Aspects of flow variability and spatial context predict temporal beta diversity in river metacommunities

“…Overall, our results indicate that temporal beta diversity of freshwater benthic macroinvertebrates may be strongly shaped by both long-term hydrological context and spatial context, and that these factors may serve as better predictors of long term community variability than variability in point estimates of environmental measurements. Recent research on flow variability has emphasized extreme flow events such as drought and floods as well as intermittency in driving community patterns (Datry et al 2014, Schneck et al 2017, Saffarinia et al 2022, Rolls et al 2022). In our study, the principal component axis with strong loadings for the magnitude and rates at which the hydrograph rises or falls showed the strongest predictive ability of temporal beta diversity.…”