Effects of ammonium sulfate on stress physiology and innate immunity of Western mosquitofish ( Gambusia affinis )
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Effects of ammonium sulfate on stress physiology and innate immunity of Western mosquitofish (Gambusia affinis) Elyse Schnabel & Travis E. Wilcoxen
Received: 22 November 2019 / Accepted: 29 July 2020 # Springer Nature B.V. 2020
Abstract Fertilizers increase yield of crops but may have unintended negative effects on fish as a byproduct of runoff into bodies of freshwater. The objective of this study was to determine if environmentally relevant concentrations of an ammonium fertilizer impacts stress and innate immunity in Western mosquitofish (Gambusia affinis). The mosquitofish were exposed to different concentrations of ammonium sulfate fertilizer: 0 ppm, 40 ppm, and 80 ppm. To test the effects of ammonium sulfate on stress physiology, cortisol released into water by individual fish was collected after 1 week of exposure and again after 2 weeks of exposure and quantified with an enzyme immunoassay. Cortisol levels in the 0ppm group were not significantly different over the course of the study, but we found a significant increase in cortisol levels in the fish exposed to 40 ppm and 80 ppm. We found reduced survival in fish from the 40 ppm and 80 ppm of ammonium sulfate groups compared with the 0-ppm group. We also used blood samples to complete a lysozyme assay as a measure of innate immune defense. Higher concentrations of ammonium sulfate correlated with significantly lower lysozyme activity in the fish. Overall, our results suggest that relatively low amounts of ammonium sulfate runoff into bodies of water are likely to have negative sublethal and lethal effects on small fishes.
E. Schnabel : T. E. Wilcoxen (*) Biology Department, Millikin University, 1184 West Main Street, Decatur, IL 62522, USA e-mail: [email protected]
Keywords Aquatic toxicology . Cortisol . Fish . Lysozyme
Introduction Ammonium sulfate (AS) fertilizer is an inorganic fertilizer that contains the necessary nitrogen and sulfur nutrients for plant growth, and is more efficient to use than some other fertilizers because it is water-soluble (Chien et al. 2011). With the application of AS to soil, soil pH decreases linearly, calcium and magnesium saturations decrease with increasing nitrogenous rates, which results in a greater crop yield (Fageria et al. 2010). It is common for fertilizers to run off the land and leak into nearby bodies of water by drainage, leaching, and flow (Savci 2012). With nitrogen-based fertilizers, the water can become polluted with nitrogen (Philips et al. 2002), having a negative impact on aquatic vertebrate life (Russo 1985; Lewis and Morris 1986; Eddy and Williams 1987; Richardson 1997; Constable et al. 2003; Jensen 2003). Inorganic nitrogen increases the acidification in freshwater ecosystems (Camargo and Alonso 2006). Grindley (1946) reported toxicity of environmentally relevant levels of ammonium sulfate on rainbow trout and minnow species in controlled laboratory conditions. Additionally, contaminants, such as ammonia, can act as environmental stressors to fish (Brown 1993). The mild reactions that numero
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