Phosphorus loading and ecological impacts from agricultural tile drains in a west Michigan watershed

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• 作者：Delilah R. Clement ; Alan D. Steinman ; ^{steinmaa@gvsu.edu}
• 关键词：Tile drain effluent ; Phosphorus ; Eutrophication ; Algal blooms ; Bioassay
• 刊名：Journal of Great Lakes Research
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：43
• 期：1
• 页码：50-58
• 全文大小：1490 K
• 卷排序：43

文摘

Phosphorus (P) loading from nonpoint sources is often implicated as a contributing factor to the proliferation of algal blooms in freshwater ecosystems. However, the influence of subsurface tile drains as a source of P, especially in agricultural areas, has received limited attention. We examined the importance of tile drain effluent in the Macatawa Watershed; this watershed is dominated by row crop agriculture and drains into hypereutrophic Lake Macatawa, which connects to Lake Michigan. Our objectives were twofold: 1) assess the importance of tile drain effluent as a source of P in the Macatawa Watershed by measuring tile drain P concentrations spatially and temporally over a one-year period; and 2) assess the ability of tile drain effluent to stimulate algal blooms using bioassays with natural phytoplankton communities. During March 2015–February 2016, P concentrations varied significantly among sample sites (SRP: < 0.005 to 0.447 mg/L; TP: 0.010 to 0.560 mg/L), and the highest P loads occurred during the non-growing season. Annual SRP yields from the tile drain sample sites ranged from 0.002 kg/ha to 0.248 kg/ha, and annual TP yields ranged from 0.003 kg/ha to 0.322 kg/ha. SRP, on average, accounted for 60% of TP, and the SRP:TP ratio measured at the tile drain outlets was positively correlated with area drained by the tile system. Algal bioassays failed to find a positive relationship between chlorophyll a and tile drain SRP; algal community structure was dominated by diatoms, not by cyanobacteria, as expected.