Mangrove Die-Off Accelerates Along Costa Mar's Northern Lagoons

The Costa Mar Reef Monitoring Network's northern station recorded nitrogen concentrations of 8.2 micrograms per litre last week—nearly double the seasonal baseline—and phosphorus at 1.1 micrograms per litre, the highest reading since the station began collecting data in 2019. The mangrove stands along Laguna Verde and Laguna Blanca show visible die-off: leaf yellowing, branch dieback, and canopy thinning visible from the water's surface. Local dive cooperatives report that visibility has worsened and fish congregations have shifted.

The timing aligns with the Federal Hydro Authority's recent increase in discharge from the Esperanto River dam system, a decision made to manage reservoir levels as the dry season deepens. The Authority has not yet published its water-quality monitoring data, though regional officials in Puerto Azul say they have requested it. The mangrove ecosystem supports the nursery grounds for commercial fish stocks, and the tourism sector depends on the aesthetic and ecological integrity of the lagoons.

Governor Solomon Adeyemi's office issued a statement this week acknowledging the elevated nutrient readings and announcing a joint review with the Federal Hydro Authority. The Costa Mar Regional Assembly's Environmental Committee is scheduled to hear testimony on the matter in mid-June. What remains unclear is whether the dam discharge pattern can be adjusted without risking the power grid's stability during the dry season.