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Measuring lotic ecosystem responses to nutrients: a mismatch that limits the synthesis and application of experimental studies to management.
Citation:
Bennett, M. AND S. Lee. Measuring lotic ecosystem responses to nutrients: a mismatch that limits the synthesis and application of experimental studies to management. Limnology and Oceanography Bulletin. American Society of Limnology and Oceanography, Lawrence, KS, 28(1):26-30, (2019). https://doi.org/10.1002/lob.10293
Impact/Purpose:
The purpose of this viewpoint article is to highlight the mismatch between nutrients used in numeric criteria development and nutrients commonly measured in experimental nutrient addition experiments.
Description:
Synthesis of existing research on nutrient (i.e., nitrogen and phosphorus) stressor-response relationships can provide scientific evidence for environmental decision makers charged with protecting and managing ecosystem integrity through the tools provided by the Clean Water Act, such as setting water quality standards to address nutrient pollution. Such syntheses benefit from inclusion of controlled studies, such as mesocosm and field manipulation experiments, which account for confounding factors and are considered high quality. We reviewed state specific water quality standards that set target protective concentrations for nutrient pollution (nutrient criteria) across the United States and 100 published nutrient addition experiments in lotic systems to assess whether experimental dose-response research typically measures the same nutrient forms used to develop criteria. We discovered a mismatch between research and management in which experimental results may not be directly useful for nutrient criteria development despite their high quality: most state criteria are based on total nitrogen (TN) and total phosphorus (TP), whereas most experimental studies use measures of dissolved nutrients (e.g., NO3-, SRP). Of the 17 states with lotic nutrient criteria, 88% had criteria based on TP and more than half had criteria based on TN. However, most published experiments used dissolved forms to report effects of nutrient addition, and only 8% measured or reported TP or TN. Regardless of any questions about whether dissolved or total nutrients better predict ecological responses in streams and rivers, numeric nutrient criteria in the U.S. are being developed predominantly based on TN and TP. Although studies measuring dissolved nutrients continue to provide invaluable information on nutrient responses, for experimental results to be most useful for managers in a synthesis framework, studies need to measure the same nutrient constituents used in criteria development. Well-designed, paired field and controlled studies could help elucidate relationships between dissolved and total nutrients in simple and complex systems. However, we urge researchers to measure TN and TP in addition to dissolved nutrients, and to be complete in data reporting, when designing and conducting nutrient addition experiments to better generate useful findings for nutrient management.
URLs/Downloads:
DOI: Measuring lotic ecosystem responses to nutrients: a mismatch that limits the synthesis and application of experimental studies to management.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6475923/