Sand Prawns Mitigate the Impact of Prolonged Drought on the Biology of a Temporary Open/Closed Estuary

The role of the sand prawn, Kraussillichirus kraussi (Stebbing, 1900), as an ecosystem engineer was evaluated through a two-and-a-half-month caging experiment conducted during a prolonged drought in the lower reaches of the temporarily open/closed Kasouga Estuary along South Africa’s eastern seaboard. Findings indicate that at intermediate densities, the burrowing activities of K. kraussi significantly enhanced microphytobenthic algal concentrations, leading to an increase in macrobenthic abundance and biomass (H(3) = 12.772, p < 0.0001; H(3) = 11.305, p = 0.001; H(3) = 13.787, p < 0.0001, respectively). This response was largely driven by elevated densities of the gastropod Nassarius kraussianus (Dunker, 1847), which benefited from the increased microphytobenthic biomass. These results highlight the critical role of K. kraussi as an ecosystem engineer, demonstrating its ability to locally enhance biological productivity even under environmental stress, such as prolonged drought conditions.