Salinized rivers: degraded systems or new habitats for salt-tolerant faunas?

Abstract

Anthropogenic salinization of rivers is an emerging issue of global concern, with significant adverse effects on biodiversity and ecosystem functioning. Impacts of freshwater salinization on biota are strongly mediated by evolutionary history, as this is a major factor determining species physiological salinity tolerance. Freshwater insects dominate most flowing waters, and the common lotic insect orders Ephemeroptera (mayflies), Plecoptera (stoneflies) and Trichoptera (caddisflies) are particularly salt-sensitive. Tolerances of existing taxa, rapid adaption, colonization by novel taxa (from naturally saline environments) and interactions between species will be key drivers of assemblages in saline lotic systems. Here we outline a conceptual framework predicting how communities may change in salinizing rivers. We envision that a relatively small number of taxa will be saline-tolerant and able to colonize salinized rivers (e.g. most naturally saline habitats are lentic; thus potential colonizers would need to adapt to lotic environments), leading to depauperate communities in these environments.

Synthesizing the role of epigenetics in the response and adaptation of species to climate change in freshwater ecosystems

“…Climate change is transforming the composition, biodiversity and functioning of numerous freshwater ecosystems (Cañedo‐Argüelles et al., ; Carpenter et al., ; Williams, ; Woodward et al., , ), as examined and revised by several authors (see Table for a synthesis of their major conclusions). Warmer temperatures, greater variability of precipitation and higher water salinities have been highlighted as the most important derived stressors for freshwater ecosystems (Cañedo‐Argüelles et al., ; Carpenter et al., ; Dudgeon et al., ; Kefford et al., ).…”

“…Mainly provoked by sea level rising, the salinization of freshwater ecosystems should have severe impacts on freshwater biodiversity, as it affects the survival and reproduction of several species which are typically poorly tolerant to variations in salts concentration (Carpenter et al., ; Gonçalves, Castro, Pardal, & Gonçalves, ; Martínez‐Jerónimo & Martínez‐Jerónimo, ; Mimura, ; Woodward et al., ). Even relatively small changes in salinity have been argued or shown to have an impact on freshwater and brackish ecosystems by depleting biodiversity and changing their dynamics and functioning (Cañedo‐Argüelles et al., ; Kefford et al., ; Loureiro, Pereira, Pedrosa, Gonçalves, & Castro, ).…”

Salinization triggers a trophic cascade in experimental freshwater communities with varying food‐chain length

“…The scope of most studies examines short-term single or multiple species toxicity tests. Salinization can also act as an environmental filter by altering community structure toward salt-tolerant species in wetland (Petranka and Doyle 2010, Van Meter et al 2011b, Van Meter and Swan 2014, and lotic ecosystems (Cañedo-Argüelles et al 2016b, Kefford et al 2016, Wallace and Biastoch 2016. Petranka and Francis (2013) showed chloride levels >246 mg Cl − /L caused the collapse of zooplankton communities, subsequently decreasing growth of larval salamander predators (Ambystoma maculatum).…”

Interacting stressors and the potential for adaptation in a changing world: responses of populations and individuals

“…Populations may vary in their resiliency due to different evolutionary histories of exposure to the stressors [57–60], and the importance of evolutionary processes, including local adaptation, in this context is beginning to be realized [7,55,56,59,61]. While population-level responses give insight to the current mean response of the population, individual-level responses (i.e.…”