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U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2006-5091


Interactive effects of dissolved zinc and orthophosphate on phytoplankton from Coeur d'Alene Lake, Idaho

By James S. Kuwabara1, Brent R. Topping1, Paul F. Woods2, James L. Carter1, and Stephen W. Hager1

1 U.S. Geological Survey, Menlo Park, CA

2 U.S. Geological Survey, Boise, ID

Executive Summary

Within the longitudinal chemical-concentration gradient in Coeur d'Alene Lake, generated by inputs from the St. Joe and Coeur d'Alene Rivers, two dominant algal species, Chlorella minutissima and Asterionella formosa, were isolated and cultured in chemically defined media to examine growth response to a range of dissolved orthophosphate concentrations and zinc-ion activities representative of the region within- and up-gradient of the Coeur d'Alene River inlet to the lake. Although zinc is an essential micronutrient, the toxicity of algal species to elevated concentrations of uncomplexed zinc has been demonstrated, and affects the metabolism of phosphorus (Kuwabara, 1985a; Kuwabara and others, 1986), the limiting nutrient in the lake. This interaction between solutes could be of management interest. As an extension of field work conducted in August, 1999 (Kuwabara and others, 2003b), the water column and benthos of Coeur d'Alene Lake were sampled in August 2001, June 2004 and June 2005 (Fig. 1; Table 1) to provide the biological characterization in terms of phytoplankton community composition, benthic macroinvertebrate community composition and benthic chlorophyll concentrations, as well as chemical characterizations at six sites (three depths per site) within the lake. This work, in support of the Idaho Department of Environmental Quality and regional tribal organizations, provides the first phytoplankton response models in a format that may be incorporated into a process-interdependent water-quality model like CAEDYM (Fig. 2; Brookes and others, 2004; Centre for Water Research, 2006) as a management tool for the lake.

This study provides information in support of developing process-interdependent solute-transport models for the watershed (that is, models integrating physical, geochemical and biological processes), and hence in support of subsequent evaluation of remediation or load-allocation strategies. The following two questions are posed: Are dissolved zinc and orthophosphate concentrations interactively associated with growth parameters of dominant phytoplankton species within the longitudinal concentration gradient of Coeur d’Alene Lake? If so, can these interactions be quantitatively incorporated into a water-quality model for the lake?

During a single sampling event, in June 2004, replicate samples from the lake water column were collected and processed for taxonomic analysis. Dominant species from two locations within- and up-gradient of the Coeur d’Alene River plume were isolated for a series of chemically defined culturing experiments. In all sampling events (August 2001, June 2004 and June 2005), the water column and benthos were also sampled to determine profiles for macronutrients, trace elements and dissolved organic carbon as well as to determine benthic macroinvertebrate community structure and, in 2005, benthic chlorophyll concentrations. This work, in support of the Idaho Department of Environmental Quality and regional tribal organizations, provides the first phytoplankton response models in a format that may be incorporated into a process-interdependent water-quality model like CAEDYM (Fig. 2; Brookes and others, 2004; Centre for Water Research, 2006) as a management tool for the lake.

TABLE OF CONTENTS

Conversion Factors, Abbreviations and Acronyms

Executive Summary

Physical and Biological Characterizations

Chemical Characterizations

Potential Management Implications

Background

Results and Discussion

Physical Data

Biological Data

Chemical Data

Study Design and Methods

Physical Data

Biological Parameters

Chemical Parameters

References Cited

Acknowledgments

Appendix 1: Comments on the Report Structure

Appendix 2: List of Figures

Appendix 3: List of Tables


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For additional information, contact:

James S. Kuwabara or Brent R. Topping
U.S. Geological Survey
345 Middlefield Road, MS 439
Menlo Park, CA 94025

Or visit the authors' project website at:

http://wwwrcamnl.wr.usgs.gov/solutetransport/index.htm


Copies of this report may be obtained from the authors.


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