Effects of nitrate on the interactions of the tadpoles of two ranids (Rana clamitans and R. catesbeiana)

Abstract

Nitrogen pollution as a result of agricultural runoff and atmospheric deposition is a major challenge to aquatic ecosystems, and is likely to increase in the future. Nitrogenous pollutants are potential stressors of amphibian larvae through their toxicological impacts on individuals; however, they may also increase primary productivity. We examined how such an anthropogenic stressor could influence the interactions between two potentially competing species of tadpoles (Rana clamitans and R. catesbeiana). In a 42 d mesocosm experiment, R. catesbeiana survival, but not final mass, was reduced by nitrate addition. Rana catesbeiana survival was lower when in competition with R. clamitans than when only experiencing intraspecific competition. For R. clamitans, survival was not affected by nitrate addition or competition type. Rana clamitans in nitrate addition mesocosms were heavier than tadpoles from no nitrate mesocosms, and were heavier in intraspecific than in interspecific mesocosms. Our results suggest that nitrate can influence the performance of amphibian larvae, and that its effects could have complex effects on aquatic ecosystems.

Intraspecific Differences in Responses of Marsh Frog (Pelophylax ridibundus) Tadpoles Exposed to Environmentally Relevant and Acute Levels of Ammonium Nitrate Fertilizer

“…Such high concentrations can lead to the inhibition of growth and mortality and cause deformities in amphibian tadpoles (e.g., Hamer et al 2004, Smith et al 2005, Orton et al 2006, Oromi et al 2009). It should also be noted that there are known synergistic effects of fertilizers with other chemicals aCorresponding author; E-Mail: kutrup@ktu.edu.tr…”

Altered Ovarian Steroids in Xenopus Laevis Exposed to Environmentally Relevant Concentrations of Nitrate

“…The ovarian responses associated with nitrate exposure observed in X. laevis might not reflect the responses of other anurans, because different species have been shown to have variable responses and tolerance to nitrate exposure (Johansson et al, 1991; < Vaala et al, 2004;Smith et al, 2005). More research is required to determine whether other species exhibit altered gonadal steroid synthesis when exposed to nitrate as shown in X. laevis.…”

“…Numerous investigations of tadpoles exposed to environmentally relevant concentrations of nitrate have demonstrated altered behaviors (Hecnar, 1995;, movement patterns (Xu and Oldham, 1997), growth rates, development (Baker andWaights, 1993, 1994;Edwards et al, 2006), gonadal morphology (Orten et al, 2006), and mortality rates Smith et al, 2005Smith et al, , 2006. However, the effects of nitrate on endocrine function of adult frogs remain unknown.…”

Efeitos letais e subletais da poluição por nitrogênio em larvas de anuros

“…Essa concentração é nada menos que 35 vezes inferior a maior concentração sem efeito observado para essa espécie nos bioensaios de 96 horas (350 mg N-amônio/L). E apesar das baixas concentrações de N-amônio que manipulei não terem afetado as larvas de R. ornata e P. cuvieri, diversos trabalhos sugerem que concentrações iguais ou até mesmos inferiores dessa forma de nitrogênio podem ser prejudiciais aos anfíbios (Schuytema & Nebeker, 1999b;Hamer et al, 2004;Marco & OrtizSantaliestra, 2009 (Smith et al, 2005), 25 mg N-nitrato/L não afetaram os girinos de Hyla regilla e Bufo boreas , e nem mesmo 30 mg N-nitrato/L afetaram a sobrevivência de Bufo terrestris (Edwards et al, 2006). Não surpreende portanto que a toxicidade do íon nitrato seja tradicionalmente considerada irrelevante ecologicamente (Russo, 1985).…”

“…Todavia, é importante ter em mente que é impossível avaliar com precisão os efeitos da poluição por N natureza a partir de experimentos de laboratório (Ortiz et al, 2004). Por exemplo, baixas concentrações de compostos nitrogenados na natureza podem ser benéficas para consumidores primários, como os girinos, devido ao aumento da produtividade primária (Smith et al, 2005). Por outro lado, concentrações consideradas inofensivas em testes de laboratório podem tornar-se prejudiciais na natureza devido a sinergismos com outros fatores físicos, químicos e/ou biológicos (veja na revisão feita por Marco & Ortiz-Santaliestra, no prelo).…”