Dried and salted: Cumulative impacts of diminished flows and salinization on Lower Pecos River food webs

Abstract

The Lower Pecos River in New Mexico and Texas, USA has experienced salinization due to exacerbation of natural saline inputs by flow alteration and irrigation practices. This situation is most pronounced in the Permian Basin region, where the negative impacts on biodiversity, particularly for the fish fauna, have been well documented. Less is known, however, about how aquatic food webs have been affected by diminished flows and salinization in the Pecos and other dryland rivers. Here, we provide a synthesis of the cumulative impacts on food web processes and trophic structure based on our work in the Lower Pecos and on research in other river systems exposed to these stressors. Impacts range from diminished availability of terrestrial basal resources to shortened food chains due to the absence of large-bodied, piscivorous fishes. Importantly, where fresh discharge from remaining springs flows into tributaries and the main stem, trophic diversity is bolstered in the Lower Pecos. This highlights the need to preserve these vital flow and resource inputs, and it provides support for the idea that flow-regime restoration in the Lower Pecos would improve ecosystem function.