Ecological Indicators (Oct 2023)
Effectiveness of rapid sampling assessments for wetland-breeding amphibians
Abstract
A primary response to the Clean Water Act has been the development of numerous indices of biotic integrity (IBI) using various taxonomic groups to assess the condition of water bodies in the United States. The IBI is a frequently used approach for assessing the ecological integrity of streams; however, it is less commonly applied to wetland systems, despite the scientific and policy needs to assess wetland condition and develop ecological performance goals for wetland monitoring, creation, and restoration. Although a great deal of attention has been given to wetland acreage due to the “no net loss” policy over the past two decades, much less attention has been given to the ecological integrity of these same wetlands. To assess wetland health and function, regulatory agencies and land managers need clear performance standards that are based on the ecology of wetland organisms. To address this need, we sampled 242 wetlands distributed across 45 managed properties in Illinois, U.S.A. over three years (2012–2014) for adult and larval amphibians (12 samples per wetland). Amphibian assemblages make up critical ecological components of many wetland ecosystems and are considered useful bioindicators of environmental change because they are sensitive to various forms of environmental and habitat alteration. We developed an amphibian-based IBI (hereafter aIBI) for the assessment of seasonal wetlands and optimal sampling strategies to best quantify these wetlands (i.e., assessment of time and effort). The aIBI applied a conservation coefficient to all species captured; conservation coefficients were developed through a survey of amphibian experts (n = 16). We captured 25 amphibian species with an average of 7.11 amphibian species (range 1–13) per site. Using the species occurrence data collected from both dipnet and minnow trap surveys over 12 survey periods, we assessed the average percent error in the estimation of aIBIs and species richness. Our results show that a wetland can be accurately evaluated with amphibians in one field season, but that multiple samples during that field season will be necessary. We show that 4–5 surveys using multiple methods distributed throughout the spring and summer are required. This level of effort may be incongruent with existing definitions of ‘rapid assessment’, but it is the necessary level of effort needed to confidently and accurately evaluate wetlands using amphibians as an indicator taxon. Additionally, aIBI provides a more robust framework to assess wetland integrity compared to simple species richness or other similar methodologies.
