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5/21/2019  |   9:15 AM - 9:30 AM   |  FACTORS AFFECTING NUISANCE ALGAL BLOOMS IN AN AGRICULTURAL STREAM BAYOU   |  150 DEF

FACTORS AFFECTING NUISANCE ALGAL BLOOMS IN AN AGRICULTURAL STREAM BAYOU

An agriculturally cultivated 17 square kilometer impounded stream bayou watershed was studied to assess variables influencing summer (June-September) nuisance algal blooms. Approximately 83% of the watershed is cropped in corn, cotton, soybeans and/or rice. During the three-year study period (2016-2018), total algal and cyanobacteria blooms (measured as chlorophyll a and phycocyanin, respectively) were affected by three major factors. Early summer (June) algal blooms were delayed by elevated suspended sediment (TSS) loads > 144 mg/L limiting light availability. During mid-summer (July-August), TSS settles and/or flushes from the water column, and nutrients (nitrogen and phosphorus) become limiting factors. Peak nuisance algal blooms occur when nutrients, specifically nitrogen, occur at concentrations > 1-2 mg/L. During late summer (September), algal blooms can be significantly mitigated by elevated chromophoric dissolved organic carbon (CDOM) at concentrations > 7 mg/L originating from extensive areas of drying row-crop plant material which can be flushed into the bayou during intense rainfall events. Previous research indicates that current agricultural best-management practices are useful in reducing TSS and nutrient loads entering rivers and streams but less is known about how such practices may reduce CDOM loads.

  • Eutrophication
  • Nutrients
  • Organic Matter

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Presenters/Authors

Richard Lizotte, Jr. (), USDA Agricultural Research Service, National Sedimentation Lab , richard.lizotte@ars.usda.gov ;


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Martin Locke (), USDA-ARS, martin.locke@ars.usda.gov ;


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