PLEASE NOTE: THIS IS A DEVELOPMENT SITE, AND THE CONTENT DOES NOT REFLECT THE MOST CURRENT INFORMATION.

Chesapeake Bay Bloom Position Forecast

These movies show the modeled bloom position from the date the satellite imagery (2025-06-16) to a minimum of 96 hours from time of the model run, using water current data from the Semi-implicit Cross-scale Hydroscience Integrated System Model (SCHISM). Potential for bloom movement and algal growth/decay is forecasted in 3-dimensions using a coupled bio-physical model combined with the satellite imagery. The modeled output does not contain clouds. Black indicates the absence of a M. polykrikoides bloom and grey indicates area with no data.
Surface concentration of the bloom, which is likely to be experienced by boaters. From 2025-06-16 up to 6 days.
Total bloom biomass--all the bloom, both surface and subsurface. From 2025-06-16 up to 6 days.

More Information:

Hydrodynamic Model:

  • SCHISM based model for the Chesapeake Bay region (2-3 km on the ocean shelf) with finer resolution grid in the tributaries (100-300 m; Rappahanock, York, and James rivers)
  • Salinity, temperature, and subtidal horizontal velocity at the ocean boundary is forced by  global HYCOM
    • A nudging zone of ~30 km near the open boundary is used to relax simulated salinity and temperature toward the HYCOM product 
  • Water level at the open boundary is interpolated from two tidal gauges at Lewes, DE and Beaufort, NC following Ye et al. (2018)
  • Daily river discharge and temperature for major tributaries are from the United States Geological Survey (USGS)
  • Atmospheric forces are obtained from NOAA’s Global Forecast System (GFS)
  • Initial salinity and temperature is based on Chesapeake Bay Program surveys (Chesapeake Bay and tributaries) and HYCOM (shelf)

Key References:

Clayton S, Chrabot JB, Echevarria M, Gibala-Smith L, Mogatas K, Bernhardt P and Mulholland MR (2024) Diel vertical migration rates of the dinoflagellate species Margalefidinium polykrikoides in a lower Chesapeake Bay tributary. Front. Microbiol. 15:1378552. doi: 10.3389/fmicb.2024.1378552

Hofmann EE, Klinck JM, Filippino KC, Egerton T, Davis LB, Echevarría M, and Mullholland MR (2021) Understanding controls on Margalefidinium polykrikoides blooms in the lower Chesapeake Bay. Harmful Algae 107:102064. doi: 10.1016/j.hal.2021.102064

Qin Q, Shen J, Reece KS, and Mulholland MR (2021) Developing a 3D mechanistic model for examining factors contributing to harmful blooms of Margalefidinium polykrikoides in a temperate estuary. Harmful Algae 105:102055. doi: 10.1016/j.hal.2021.102055

Wolny JL, Tomlinson MC, Schollaert Uz S, Egerton TA, McKay JR, Meredith A, Reece KS, Scott GP and Stumpf RP (2020) Current and Future Remote Sensing of Harmful Algal Blooms in the Chesapeake Bay to Support the Shellfish Industry. Front. Mar. Sci. 7:337. doi: 10.3389/fmars.2020.00337

Xiong J, Shen J, Qin Q, Tomlinson MC, Zhang YJ, Cai X, Ye F, Cui L, and Mulholland MR. (2023) Biophysical interactions control the progression of harmful algal blooms in Chesapeake Bay: A novel Lagrangian particle tracking model with mixotrophic growth and vertical migration. Limnology Oceanography Lett. 8:498–508. doi: 10.1002/lol2.10308

Ye F, Zhang YJ, Wang HV, Friedrichs MAM, Irby ID, Alteljevich E, Valle-Levinson A, Wang Z, Huang H, Shen J, and Du J. (2018) A 3D unstructured-grid model for Chesapeake Bay: Importance of bathymetry. Ocean Model. 127:16–39. doi: 10.1016/j.ocemod.2018.05.002

Yu X, Tomlinson MC, Shen J, Li Y, Hounshell AG, Scott GP and Reece KS (2025) Using a coupled satellite image-numerical model framework to simulate Margalefidinum polykrikoides in the York River estuary. Front. Mar. Sci. 12:1561340. doi: 10.3389/fmars.2025.1561340

Zhang YJ, Ye F, Stanev EV, and Grashorn S. (2016) Seamless cross-scale modeling with SCHISM. Ocean Model. 102, 64–81. doi: 10.1016/j.ocemod.2016.05.002