Benthic algae are the nutritional base of most freshwater food webs. Here we consider the nutritional contribution of benthic algae in the form of fatty acids (FAs) over multiple seasons and years. Our study was conducted in the Upper Delaware River watershed (New York, USA), where best-management practices (BMPs) had been implemented over varying numbers of years (BMP age) to mitigate effects of agricultural activities in the watershed. We defined 4 BMP categories by the presence and duration of management used in each stream drainage prior to initiating our study: 1) reference (unaffected), 2) no BMP (agriculturally affected), 3) new (agriculturally affected, BMP ≤ 2 y), and 4) old (agriculturally affected, BMP ≥ 3 y). Our results indicate that BMPs were able to reduce agricultural effects, as evidenced by a significantly lower benthic algal total FA content in reference than in agricultural streams. However, FA content did not differ between BMP-age categories, a result suggesting that BMPs were rapidly effective (within 1–2 y). Among essential molecules, amount of essential FA precursors (alinoleic acid 18:3x3 and linolenic acid 18:2x6) were inversely related to their derivatives (arachidonic acid 20:4x6, eicosapentaenoic acid 20:5x3, docosahexaenoic acid 20:6x3) across BMP-age categories. These outcomes suggest that BMP practices are important for maintaining the quality of the New York City metropolitan area water supply.
agriculture, benthic algae, bioassessment, BMPs, fatty acids, streams
Whorley, S. B., & Wehr, J. D. (2018). Multiyear Patterns in Benthic Algal Fatty-Acid Compounds Under Agricultural Stress. Freshwater Science, 37(3), 534-550. https://doi.org/10.1086/699201