Response to Schmidt. Pesticides, mortality and population growth rate

Sih, Andrew; Kerby, Jake; Bell, Alison M.; Relyea, Rick A.

doi:10.1016/j.tree.2004.06.011

Cited by 9 publications

(6 citation statements)

References 14 publications

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“…2005) or, alternatively, modelling the impacts of the mortality using life‐table response experiments (Caswell 2001), extrapolation to future population‐level impacts will remain conjecture. At the same time, it is important to appreciate that assessing the impacts of pesticides on population dynamics is not a trivial task and has thus far only been carried out (to our knowledge) on species with very short generation times (Sih et al. 2004).…”

Section: Unexplored Research Areasmentioning

confidence: 99%

Assessing the ecology in ecotoxicology: a review and synthesis in freshwater systems

2006

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The field of ecotoxicology is experiencing a surge in attention among ecologists as we gain a deeper appreciation for how contaminants can impact natural ecosystems. This interest is particularly strong in aquatic systems where many non-target organisms experience pesticides. In this article, we assess how pesticides affect freshwater systems by applying the conceptual framework of density-and trait-mediated indirect effects from the field of basic ecology. We demonstrate the utility of this framework for understanding the conditions under which pesticides affect species interactions, communities and ecosystems. Through the integration of laboratory toxicity tests and this ecological framework, ecotoxicologists should be better able to identify the mechanisms through which pesticides affect communities and ecosystems. We also identify several areas of research that are in critical need of empirical attention including synergistic effects between pesticides and natural stressors, the importance of pesticides on community assembly via habitat preferences and oviposition effects, the timing and frequency of pesticide applications, pesticide effects on population dynamics, the evolution of pesticide resistance in non-target organisms and ecosystem recovery. With this knowledge, one can improve upon management decisions and help protect nontarget species that are of conservation concern. Keywords Biodiversity, density-mediated indirect effects, ecosystem function, fungicide, herbicide, insecticide, trait-mediated indirect effects.Ecology Letters (2006) 9: 1157-1171 I N T R O D U C T I O NThe fields of ecology and toxicology have largely evolved as separate disciplines over the past century with unique journals, unique tools and a distinct jargon that has reinforced an allopatric evolution of ideas. While ecologists have focused on how biotic and abiotic factors affect species distribution and species interactions, toxicologists have traditionally focused on single-species toxicity tests. There is, however, the growing field of ecotoxicology, a name that naturally implies a hybrid of ideas and approaches from ecology and toxicology. Given that the number of ecotoxicological studies has experienced tremendous growth in the past decade, it is an excellent time to evaluate what we have learned. In this essay, we evaluate the study of ecotoxicology in freshwater systems, an arena that has received a great deal of research focus. In doing so, we examine how one can use general ecological theory to integrate ecology and ecotoxicology to better understand and conserve the ecology of aquatic systems.

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Section: Unexplored Research Areasmentioning

confidence: 99%

Assessing the ecology in ecotoxicology: a review and synthesis in freshwater systems

2006

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“…2 Historical pesticide use has been implicated as a potential factor for declines for multiple amphibian species. [3][4][5][6][7][8] Much of the interest on amphibian's declines is currently focused on the role of pesticides on the observed global declines. 3,[9][10][11][12] Concentrations of diazinon pesticide typically found in Nigerian waters range from 0.01-3.64, which are above the ecological benchmark (0.01 µg/L) recommended by Nigerian Environmental Protection agency.…”

Section: Introductionmentioning

confidence: 99%

Diazinon mediated biochemical changes in the African toad (Bufo regularis)

Tongo¹,

Ezemonye²,

Ochei

2012

J Xenobiotics

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The sublethal toxicity of diazinon to the adult African toad, Bufo regularis was assessed using an integration of biomarkers. Changes in acetylcholinesterase (AChE), corticosterone and total protein levels were assessed in the serum, brain, liver, lungs and gastrointestinal tract (GIT) and the results supported by bioaccumulation data. The biomarkers were chosen as indicators of key physiological functions: AChE for neurotoxicity, corticosterone and total protein levels as indicators of oxidative stress. Toads were exposed to 0.01, 0.02, 0.03 and 0.04 g/L for 28 days. Brain AChE activity reduced by 96% in the highest concentration (0.04 g/L) compared to the control brain. Similarly, AChE activities in serum, liver, lungs and GIT tissues (88%, 88%, 87, 87% umg -1 protein respectively) were also inhibited in the toads. Corticosterone and total protein levels in the tissues decreased compared to the control. The accumulation results obtained showed accumulation in the tissues (liver>serum>brain> lung>GIT), with a direct relationship between tissue concentration and changes in the biochemical indices. The alterations in all the indices were significantly concentration dependent. The biomarkers described in this study could be useful complementary indices in the risk assessment of diazinon pesticide.

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“…Moreover, the sheer number of registered chemicals (tens of thousands) and species to be tested and the complexities of population growth rate analyses may make this approach too time-consuming considering the urgent need to identify causal factors in the global decline of amphibians ( Houlahan et al 2000 ; Stuart et al 2004 ). Researchers have suggested that a more practical and efficient alternative may be to study the effects of contaminants across life stages using amphibians reared under semi-natural conditions where postexposure effects and density-dependent regulation are permitted ( Rohr et al 2004 ; Sih et al 2004 ). The proxy for population-level effects would be the net effect of the contaminant at some point near reproductive age, where the net effect is defined as the sum of exposure effects, carryover effects, and density-mediated compensation ( Figure 1 ).…”

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confidence: 99%

Exposure, Postexposure, and Density-Mediated Effects of Atrazine on Amphibians: Breaking Down Net Effects into Their Parts

Rohr

Sager

Sesterhenn

et al. 2006

Environ Health Perspect

108

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Most toxicology studies focus on effects of contaminants during exposure. This is disconcerting because subsequent survival may be affected. For instance, contaminant-induced mortality can be later ameliorated by reduced competition among the survivors, a concept we refer to as “density-mediated compensation.” Alternatively, it can be exacerbated by toxicant effects that persist or appear after exposure, a phenomenon we term “carryover effects.” We developed a laboratory framework for testing the contribution of exposure, density-mediated, and carryover effects to net survival, by exposing embryos and larvae of the streamside salamander (Ambystoma barbouri) to atrazine (0, 4, 40, 400 ppb; 3 ppb is the U.S. drinking water maximum) and quantifying survival during and 14 months after exposure. Atrazine is the most commonly used herbicide in the United States and a documented endocrine disruptor. We show that atrazine-induced mortality during exposure was ameliorated by density-dependent survival after exposure, but complete density-mediated compensation was precluded by significant carryover effects of atrazine. Consequently, salamanders exposed to ≥4 ppb of atrazine had significantly lower survival than did control animals 14 months postexposure. The greatest change in survival occurred at low exposure concentrations. These nonlinear, long-term, postexposure effects of atrazine have similarities to effects of early development exposure to other endocrine disruptors. Together with evidence of low levels of atrazine impairing amphibian gonadal development, the results here raise concerns about the role of atrazine in amphibian declines and highlight the importance of considering persistent, postexposure effects when evaluating the impact of xenobiotics on environmental health.

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Response to Schmidt. Pesticides, mortality and population growth rate

Cited by 9 publications

References 14 publications

Assessing the ecology in ecotoxicology: a review and synthesis in freshwater systems

Assessing the ecology in ecotoxicology: a review and synthesis in freshwater systems

Diazinon mediated biochemical changes in the African toad (Bufo regularis)

Exposure, Postexposure, and Density-Mediated Effects of Atrazine on Amphibians: Breaking Down Net Effects into Their Parts

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