Relating Cyanobacteria and Physicochemical Water-Quality Properties in Willow Creek Lake, Nebraska, 2012–14

Scientific Investigations Report 2018-5121
Prepared in cooperation with the Lower Elkhorn Natural Resources District, Nebraska Department of Environmental Quality, Nebraska Game and Parks Commission, Nebraska Department of Natural Resources, Nebraska Environmental Trust, and University of Nebraska–Lincoln
By: , and 

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Abstract

Cyanobacteria (also referred to as blue-green algae) are naturally present members of phytoplankton assemblages that may detract from beneficial uses of water because some strains produce cyanotoxins that pose health hazards to people and animals. Cyanobacteria populations observed in Willow Creek Lake during 2012 through 2014 were compared to external nutrient loading from the Willow Creek drainage basin and several other physicochemical properties within the lake, including internal nutrient loading. This report is part of a cooperative study between the U.S. Geological Survey, the Lower Elkhorn Natural Resources District, the Nebraska Department of Environmental Quality, the Nebraska Game and Parks Commission, the Nebraska Department of Natural Resources, the Nebraska Environmental Trust, and the University of Nebraska–Lincoln.

Cyanobacteria concentrations were quantified using weekly microcystin sampling, intermittent algal taxonomy, and hourly in-situ phycocyanin measurements. External and internal nutrient loads, lake water physical characteristics, and local meteorological conditions were evaluated as potential causes of cyanobacterial blooms. A water balance approach that estimated Willow Creek Lake inflow and outflow volumes identified Willow Creek as the major inflow and groundwater flux as the major outflow for the lake. Nutrient concentrations from several water sources were quantified and combined with flow volumes to compute nutrient loads during the study period.

Surface flows contributed most external nutrients to the lake, whereas lake nutrients were exported during groundwater losses. The main stem of Willow Creek accounted for most nitrate loads to the lake, whereas total Kjeldahl nitrogen, total phosphorus, and phosphate loads to the lake were more evenly distributed between Willow Creek and the North Tributary, a smaller drainage. Sediment core incubations determined internal phosphorus loading was a negligible component of the overall nutrient load to the lake.

Cyanobacterial responses were compared to nutrient loads and other external factors that could potentially affect algal growth. A series of univariate comparisons were made by plotting those factors against phycocyanin using biweekly summaries of each and a multivariate model that incorporated seasonality and cumulative nitrate loading. Although the multivariate model only incorporated cumulative nitrate, both nitrogen and phosphorus are likely contributing to cyanobacterial population growth, and management efforts may benefit from the recognition of differences in nutrient loading characteristics between the monitored basins.

Suggested Citation

Rus, D.L., Hall, B.M., and Thomas, S.A., 2018, Relating cyanobacteria and physicochemical water-quality properties in Willow Creek Lake, Nebraska, 2012–14: U.S. Geological Survey Scientific Investigations Report 2018–5121, 43 p, https://doi.org/10.3133/sir20185121.

ISSN: 2328-0328 (online)

Study Area

Table of Contents

  • Acknowledgments
  • Abstract
  • Introduction
  • Methods
  • Cyanobacterial Characteristics in Willow Creek Lake
  • Physicochemical Water-Quality Properties of Willow Creek Lake
  • Relation of Nutrients and Other Factors to Cyanobacteria
  • Summary
  • References Cited
  • Appendix 1. Development of Stream Nutrient Load Models

Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title Relating cyanobacteria and physicochemical water-quality properties in Willow Creek Lake, Nebraska, 2012–14
Series title Scientific Investigations Report
Series number 2018-5121
DOI 10.3133/sir20185121
Year Published 2018
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Nebraska Water Science Center
Description Report: x, 43 p.; Data Release
Country United States
State Nebraska
Other Geospatial Willow Creek Lake
Online Only (Y/N) Y