Global change pressures influence estuarine functionality, driving structural shifts that threaten ecosystem resilience. Estuarine lakes are inherently susceptible to these pressures given their tendency to experience prolonged periods of water residency and mouth closure. As such, this study aimed to investigate water quality and phytoplankton responses to drastic shifts in abiotic conditions during the transition from a dry to wet cycle in the Verlorenvlei Estuarine Lake, South Africa. Initially, drought- and human-induced hydrological constraints resulted in extreme environmental conditions, characterised by low water levels and acidification. These low water levels reduced connectivity, resulting in hypersaline conditions and phytoplankton blooms (>
20 μg Chl-a L