Microalgal biomass in the St Lucia Estuary during the 2004 to 2007 drought period

Extreme microalgal biomass levels, among the highest recorded globally, were observed in the St Lucia Estuary during South Africa's 2004-2007 drought. Water-column chlorophyll a concentrations averaged 32.3 ± 53.4 mg m⁻³, with peaks reaching 413 mg m⁻³, while sediment concentrations averaged 201 ± 377 mg m⁻², peaking at 2576 mg m⁻²—far surpassing values reported for other estuaries. Spatial and temporal variability in phytoplankton and microphytobenthos biomass was linked to water levels, mouth state, and nutrient availability (N:P ratios). Hypersaline conditions during the closed phase, with temperatures nearing 50°C, likely suppressed grazers, contributing to microalgal dominance. The study highlights the iSimangaliso Wetlands Park's ecological sensitivity to drought and hydrological changes.

Perissinotto, R., Pillay, D., & Bate, G. (2010). Microalgal biomass in the St Lucia Estuary during the 2004 to 2007 drought period. Marine Ecology Progress Series, 405, 147–161. https://doi.org/10.3354/meps08542