33 Harmful Algal Bloom Indicator - Mid Atlantic
Description: An aggregation of reported algal bloom data in Chesapeake Bay between 2007-2017.
Found in: State of the Ecosystem - Mid-Atlantic (2018)
Indicator category: Database pull
Contributor(s): Sean Hardison, Virginia Department of Health
Data steward: Kimberly Bastille, kimberly.bastille@noaa.gov
Point of contact: Kimberly Bastille, kimberly.bastille@noaa.gov
Public availability statement: Source data for this indicator are available here. Processed time series can be found here.
33.1 Methods
We presented two indicator time series for reports of algal blooms in the southern portion of Chesapeake Bay between 2007-2017. The first indicator was observations of algal blooms above 5000 cell ml-1. This threshold was developed by the Virginia Department of Health (VDH) for Microcystis spp. algal blooms based on World Health Organization guidelines (Organization 2003; Health 2011). VDH also uses this same threshold for other algal species blooms in Virginia waters. When cell concentrations are above 5000 cell ml-1, VDH recommends initiation of biweekly water sampling and that relevant local agencies be notified of the elevated cell concentrations.
The second indicator we reported, blooms of Cochlodinium polykrikoides at cell concentrations >300 cell ml-1, was chosen due to reports of high ichthyotoxicity seen at these levels. Tang and Gobler (2009) showed that fish exposed to cultured C. polykrikoides at densities as low 330 cells ml-1 saw 100% mortality within 1 hour, which if often far less than C. polykrikoides cell concentrations seen in the field. Algal bloom data were not available for 2015 nor 2010. The algal bloom information presented here are a synthesis of reported events, and has been updated to include data not presented in the 2018 State of the Ecosystem Report.
33.1.1 Data sources
Source data were obtained from VDH. Sampling, identification, and bloom characterization was completed by the VDH, Phytoplankton Analysis Laboratory at Old Dominion University (ODU), Reece Lab at the Virginia Institute of Marine Science (VIMS), and Virginia Department of Environmental Quality. Problem algal species were targeted for identification via light microscopy followed by standard or quantitative PCR assays and/or enzyme-linked immunosorbent assay (ELISA). Reports specifying full methodologies from ODU, VIMS, and VDH source data are available upon request.
33.1.2 Data extraction
Data were extracted from a series of spreadsheets provided by the VDH. We quantified the number of algal blooms in each year reaching target cell density thresholds in the southern Chesapeake Bay.
R code used in extracting harmful algal bloom data can be found here.