δ(15)N of Chironomidae: An index of nitrogen sources and processing within watersheds for national aquatic monitoring programs
| Autor: | Jiajia Lin, Amanda M. Nahlik, Alan T. Herlihy, Jana E. Compton, W D Rugh, J. Renée Brooks, Marc H. Weber |
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| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
Pollution
Environmental Engineering Watershed Nitrogen media_common.quotation_subject STREAMS Chironomidae Article Water column Rivers Environmental Chemistry Animals Humans Waste Management and Disposal Ecosystem media_common Hydrology biology Nitrogen Isotopes Aquatic ecosystem δ15N biology.organism_classification Environmental science Water quality Water Pollutants Chemical Environmental Monitoring |
| Zdroj: | Sci Total Environ |
| Popis: | Nitrogen (N) removal along flowpaths to aquatic ecosystems is an important regulating ecosystem service that can help reduce N pollution in the nation’s waterways, but can be challenging to measure at large spatial scales. Measurements that integrate N processing within watersheds would be particularly useful for assessing the magnitude of this vital service. Because most N removal processes cause isotopic fractionation, δ(15)N from basal food-chain organisms in aquatic ecosystems can provide information on both N sources and the degree of watershed N processing. As part of EPA’s National Aquatic Resource Surveys (NARS), we measured δ(15)N of Chironomidae collected from over 2000 lakes, rivers and streams across the continental USA. Using information on N inputs to watersheds and summer total N concentrations ([TN]) in the water column, we assessed where elevated chironomid δ(15)N would indicate N removal rather than possible enriched sources of N. Chironomid δ(15)N values ranged from −4 to +20 ‰, and were higher in rivers and streams than in lakes, indicating that N in rivers and streams underwent more processing and cycling that preferentially removes (14)N than N in lakes. Chironomid δ(15)N increased with watershed size, N inputs, and water chemical components, and decreased as precipitation increased. In rivers and streams with high watershed N inputs, we found lower [TN] in streams with higher chironomid δ(15)N values, suggesting high rates of gaseous N loss such as denitrification. At low watershed N inputs, the pattern reversed; streams with elevated chironomid δ(15)N had higher [TN] than streams with lower chironomid δ(15)N, possibly indicating unknown sources elevated in δ(15)N such as legacy N, or waste from animals or humans. Chironomid δ(15)N values can be a valuable tool to assess integrated watershed-level N sources, input rates, and processing for water quality monitoring and assessment at large scales. |
| Databáze: | OpenAIRE |
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