Monitoring wetland water quality related to livestock grazing in amphibian habitats

Kelly L Smalling,Chauncey W Anderson,Luke R Iwanowicz,Christopher A Pearl,Michael J Adams,Jennifer C Rowe,Brome Mccreary,Carrie E Givens

doi:10.1007/s10661-020-08838-6

Kelly L Smalling, Chauncey W Anderson + Show 6 more

Open Access

https://doi.org/10.1007/s10661-020-08838-6

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Abstract

Land use alteration such as livestock grazing can affect water quality in habitats of at-risk wildlife species. Data from managed wetlands are needed to understand levels of exposure for aquatic life stages and monitor grazing-related changes afield. We quantified spatial and temporal variation in water quality in wetlands occupied by threatened Oregon spotted frog (Rana pretiosa) at Klamath Marsh National Wildlife Refuge in Oregon, United States (US). We used analyses for censored data to evaluate the importance of habitat type and grazing history in predicting concentrations of nutrients, turbidity, fecal indicator bacteria (FIB; total coliforms, Escherichia coli (E. coli), and enterococci), and estrogenicity, an indicator of estrogenic activity. Nutrients (orthophosphate and ammonia) and enterococci varied over time and space, while E. coli, total coliforms, turbidity, and estrogenicity were more strongly associated with local livestock grazing metrics. Turbidity was correlated with several grazing-related constituents and may be particularly useful for monitoring water quality in landscapes with livestock use. Concentrations of orthophosphate and estrogenicity were elevated at several sites relative to published health benchmarks, and their potential effects on Rana pretiosa warrant further investigation. Our data provided an initial assessment of potential exposure of amphibians to grazing-related constituents in western US wetlands. Increased monitoring of surface water quality and amphibian population status in combination with controlled laboratory toxicity studies could help inform future research and targeted management strategies for wetlands with both grazing and amphibians of conservation concern.

Highlights

Livestock grazing is one of the most common land uses globally (Bigelow and Borchers 2012) and in the western United States (US), grazing is widespread across a broad range of landscapes and wildlife habitats (Fleischner 1994)
We focused our water quality assessment on constituents that have been used previously in other grazing studies and have the potential to adversely affect R. pretiosa and other amphibian species including nutrients, turbidity, fecal indicator bacteria (FIB; total coliforms, Escherichia coli (E. coli), and enterococci), and estrogenicity
The relationship between grazing and FIB found here is consistent with other studies (e.g., Canals et al 2011; Roche et al 2013), and points to bacteria as an informative parameter for monitoring, especially given it may be less prone to within-wetland processes such as denitrification or biotic utilization of organic nitrogen that can mask inputs and result in low concentrations of nutrients (Hopkinson 1992)

Summary

Introduction

Livestock grazing is one of the most common land uses globally (Bigelow and Borchers 2012) and in the western United States (US), grazing is widespread across a broad range of landscapes and wildlife habitats (Fleischner 1994). Species relying on aquatic habitats in grazed landscapes, such as amphibians, show diverse responses to grazing pressures (Howell et al 2019). Habitat loss and alteration are primary drivers of declines (Collins and Storfer 2003), yet in areas where water is scarce, stock ponds, wetlands, and small streams used by cattle can provide essential aquatic habitat (Knutson et al 2004). Water quality changes associated with grazing (i.e., increased nitrate or sediment loads, reduced dissolved oxygen, introduction of steroid hormones) have potential to alter amphibian abundance, growth, species richness, sex ratios, behavior, and parasite communities (Marco et al 1999; Johnson and Chase 2004; Kolodziej and Sedlak 2007; Burton et al 2009; Lambert et al 2015; Babini et al 2016). In some systems, the addition of nutrients can benefit amphibians via increased habitat productivity and resource allocation (Plăiaşu et al 2010)

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