Wetland Assessment: Beyond the Traditional Water Quality Perspective.

Water chemistry or water quality is often used to determine if aquatic ecosystems meet restoration objectives or Clean Water Act criteria. However, it is not consistently possible to collect water in wetlands because surface water presence varies across wetland types. Using data from the National Wetland Condition Assessment (NWCA), a survey of 967 sites representing 25,153,681 hectares of wetland across the conterminous US, we found surface water could be collected at only 537 of the sampled sites, representing only 41% of the wetland population area and under-representing particular wetland types. We use wetlands to introduce the concept of aquatic resource quality, the condition of an ecosystem based on the collective assessment of physical, chemical, and biological indicators, to meet monitoring and assessment goals for aquatic ecosystems. Wetland condition was evaluated through the NWCA based on a biotic indicator (vegetation multimetric index) at each sampled site. Results indicated wetland resource quality was good for about half of the area of the sampled population, with the remainder of the wetland area in fair and poor quality. Ten physical, chemical, and biological indicators measured at every site were used to report the relative extent and relative risk of stressors on wetland resource quality. Physical stressors, especially vegetation removal and surface hardening, are commonly observed and have negative impacts on aquatic resource quality. Because aquatic resource quality can be consistently evaluated, regardless of surface water presence or aquatic ecosystem type, we propose that this concept be used as the basis for aquatic ecosystem monitoring and assessment.

Impact/Purpose

A comprehensive assessment of an ecosystem requires information about the physical, chemical, and biological integrity; however, scientists and managers often solely use surface water chemistry or water quality to address Clean Water Act (CWA) criteria or monitoring objectives. For ecosystems that have variable presence of surface water, like wetlands, this approach is problematic. For example, of 967 wetland sites included in the 2011 National Wetland Condition Assessment (NWCA), surface water chemistry was only present at 537 sites, representing 41% of the wetland population area. Furthermore, the wetlands with surface water chemistry were disproportionally represented by particular wetland types, such as tidal and riverine wetlands that have permanent sources of surface water. In this presentation, Amanda Nahlik, Mary Kentula, Steve Paulsen, and Teresa Magee (EPA/ORD/CPHEA/PESD) introduce the concept of aquatic resource quality to meet CWA criteria and monitoring objectives. Aquatic resource quality is the ecological condition of an aquatic ecosystem. Evaluating aquatic resource quality requires the collective use of physical, chemical, and biological indicators to describe the ecological condition of the resource and identify factors negatively affecting the condition. We present wetland condition for wetlands of the conterminous US through the 2011 NWCA based on a biotic indicator (vegetation multimetric index), and we identify factors that negatively affect condition using ten physical, chemical, and biological indicators measured at each sampled site. Results indicated wetland resource quality was good for about half of the area of the sampled population, with the remainder of the wetland area in fair and poor quality. Physical stressors, especially vegetation removal and surface hardening, are commonly observed and have negative impacts on wetland resource quality. We propose that aquatic resource quality is a stronger measure of ecosystem integrity than water chemistry or water quality alone because (1) it can be consistently evaluated across all aquatic ecosystems, regardless of the presence of surface water, (2) it comprehensively addresses physical, chemical, and biological aspects of the ecosystem, and (3) it allows comparison and integration of information across aquatic ecosystem types. The USEPA National Aquatic Resource Surveys have been collecting data for over a decade that provides a basis for aquatic resource quality in the continental US.

Citation

Nahlik, A., M. Kentula, Steve Paulsen, AND T. Magee. Wetland Assessment: Beyond the Traditional Water Quality Perspective. Society of Wetland Scientists Annual Meeting, NA, None-Virtual, June 01 - 10, 2021.