Regular monitoring: northern/central sites show typical seasonal conditions; St. Lucie estuary salinities stable under Lake Okeechobee recovery releases

St. Johns River Water Management District and South Florida Water Management District staff briefed the council on routine monitoring for the Northern, Central and Southern stretches of the Indian River Lagoon on Feb. 14.

Northern and central lagoon: Lauren Hall of the St. Johns River Water Management District said continuous monitoring sites through Mosquito Lagoon, Titusville, Cocoa, Banana River and Vero Beach showed seasonal patterns consistent with winter conditions. Salinity rose at most sites during the dry months; dissolved oxygen generally remained well above hypoxic levels (2 mg/L). Short, transient chlorophyll spikes—likely diatom blooms—were recorded but did not develop into long‑lasting, widespread blooms. Secchi (water clarity) measurements were lower at some sites in Melbourne and Sebastian on the monthly snapshot sampling, but preliminary samples taken in February indicated clarity had improved to roughly 1.5 meters in those stations.

Seagrass: Hall said field divers observed patches of Halophila species at a northern Brevard monitoring site where cover had been low during summer; that site now shows higher percent cover than in previous surveys. Full winter transect data were still being collected and will be reported later.

Southern lagoon / St. Lucie Estuary: Melanie Parker of the South Florida Water Management District summarized inflows to the St. Lucie estuary and current salinity and oyster monitoring. The U.S. Army Corps’ Lake Okeechobee recovery operations have driven additional regulated releases to the estuary since December. Parker said seven‑day average inflows at the time of the meeting averaged about 1,389 cubic feet per second, with most flow originating at the lake.

Salinity and oysters: Parker reported salinities in the upstream North Fork (HR‑1) were in the “stressful” range for adult oysters at the surface (roughly 5–10) while bottom salinities at that station remained in the “optimal” band (10–25). Middle and downstream stations (US‑1 and A1A bridge) were generally within the optimal range. Weekly monitoring at the estuary showed relatively consistent salinity patterns since mid‑December. Florida Wildlife Institute spat settlement monitoring showed a 2024 pattern of spring recruitment followed by a decline through summer and fall; Parker said that low spat numbers later in 2024 corresponded to lower salinity events that reduce larvae survival.

What the council heard: both agencies cautioned that routine monitoring is a snapshot; monthly boat transects and continuous sondes capture different aspects of variability. Staff noted a sensor calibration issue at one Cocoa deployment that will be investigated. Council members asked about flow gauges and a problematic instrument at Tim Allen Creek; staff said the flow gauge was not functioning and that the team is tracking repairs and data gaps.

Ending: both monitoring teams will return with full seagrass transect results and additional station troubleshooting at the council’s next meeting. The reports indicated no current basin‑wide hypoxia events during the winter sampling period and continued focus on impacts from large lake releases to the southern lagoon.