Consultant says Ocean Shores waterways are "eutrophic to hyper-eutrophic," outlines management options

Katie Rodriguez, a limnologist with Herrera Environmental Consultants, told the Freshwater Waste Advisory Board that the city’s canals and lakes are "eutrophic to hyper eutrophic," a trophic state driven by high phosphorus that fuels cyanobacteria blooms. She cited 2024 field sampling that found cyanobacteria hotspots in Duck Lake, Lake Menard, Fish Hook and Granite Canal South and noted at least one microcystin exceedance in 2024. "What we found was that the entire system as a whole is really eutrophic to hyper eutrophic," Rodriguez said, and she emphasized groundwater and certain creek inputs as major phosphorus sources.

Rodriguez reviewed a range of management approaches in the draft cyanobacteria management plan, explaining the trade-offs and likely effectiveness of each. She recommended routine surveillance and targeted monitoring, communication to residents and visitors about bloom recognition and reporting, and a mix of in-lake controls where appropriate. She advised that dredging would likely be ineffective because groundwater-derived phosphorus would re-fill excavated areas; instead, options included annual alum (aluminum sulfate) treatments for many management units, hypolimnetic oxygenation for Lake Menard, enhanced circulation devices for shallow canals, and targeted algaecide for short-term events. Rodriguez offered to provide monitoring maps and OST (oxygenation saturation technology) contractor information after the meeting.