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The Historical Prevalence of Cyanobacteria in Spanaway Lake, Pierce County, Washington
Citation:
Hobbs, W., E. Frame, F. Sweeney, I. Struewing, N. Sienkiewicz, J. Lu, E. Villegas, AND R. Labiosa. The Historical Prevalence of Cyanobacteria in Spanaway Lake, Pierce County, Washington. Washington State Department of Ecology, Lacey, WA, 2022.
Impact/Purpose:
1) Public concern over cyanobacterial blooms has increased due to their higher frequency of occurrences and their potential ecological and health impacts. 2) Microcystin is also the most common cyanotoxin produced with Microcystis and Planktothrix being the major toxin producing cyanobacterial genera during CyanoHABs. Previously, we have demonstrated that mcy-targeted qPCR and RT-qPCR can be useful as a detection indicator for microcystin production in fresh surface waters. The presence of mcy gene in lake sediment cores can indicate the long-term ecological changes and the historical context of lakes over the last ~150 years or more. 3) This information can be used to aid in making management decisions related to harmful algal blooms. 4) OW, regional offices, scientists and water quality managers could be interested in the results.
Description:
Spanaway Lake in Pierce County (Washington) experiences annual harmful cyanobacterial blooms that produce high concentrations of the toxin, microcystin. The goal of this project was to understand whether, 1) cyanobacteria have been a dominant part of the lake phytoplankton historically (~150 years ago) and 2) whether microcystin was produced historically. The project entailed: • Collecting a lake sediment core. • Establishing sediment ages using radioisotopes. • Analyzing the sediment intervals for fossil algal pigments, microcystin concentrations, and microcystin-producing genes. The pigment analysis of the sediments recorded a diverse cyanobacteria community in the lake, extending back to approximately 1850. This finding suggests that the physical and chemical (i.e. nutrients), characteristics of the lake supported cyanobacteria prior to urbanization. Measured pigments in modern sediments represented both colonial cyanobacteria (zeaxanthin and myxoxanthophyll) and filamentous cyanobacteria (canthaxanthin). Microcystin compounds (MCs) were measured throughout the sediment core, with the MC-LA variant making up over 97 - 100% of the total MC. Copies of cyanobacterial 16S rRNA gene were measured throughout the sediment core. Microcystin-producing genes (mcyE) linked to several cyanobacterial genera (i.e., Anabaena, Microcystis and Planktothrix) were detected back to 1850 with a period of no detection from ~1900 – 1950. Microcystin-producing genes specific to Microcystis (mcyA) were detected in the sediment record after 1985. Overall, Spanaway Lake has a long history of cyanobacteria production, however changes in the pigment abundance and microcystin-producing genes suggest that the post-1985 period of the lake has had a greater dominance of cyanobacteria with higher levels of toxin production.
URLs/Downloads:
THE HISTORICAL PREVALENCE OF CYANOBACTERIA IN SPANAWAY LAKE, PIERCE COUNTY, WASHINGTON