First Assessment of the Effects of the 2000 Southern Mozambique Floods on Coral Communities: The Case of Xai-Xai Lagoon

Abstract

The southern part of Mozambique suffered, at the beginning of the present year, the worst floods in the last 50 years, which caused several fatalities and high material losses. The objective of this study was to investigate the influence of this phenomenon on the coral communities of the Xai-Xai lagoon reef. Benthic category percentage cover was assessed in January 2000 (before the floods) and September 2000 (after the floods) using the line intercept transect (LIT). A decrease of hard coral percentage cover was observed, in the order of 58.5 %. The soft coral community was also affected, with a high decrease of percentage cover, about 90.4%. Other benthic category that showed an elevated decrease was coralline algae (85.1%). All other categories increased their percentage cover: turf algae (164.4%), other invertebrates (e.g. sponges, sea urchins – 111.1%), fleshy algae (80.4%), rubble (34.4%) and dead coral (379.0%). The main causes of this degradation scenario are the low salinity values and high amount of sediment discharged by the Limpopo River. Some massive (e.g. Porites, Favia, Favites and Goniopora) and encrusting (e.g. Echinopora) hard coral genera, seemed less affected, suggesting an elevated adaptation capacity to this kind of stress through massive mucus-sheet formation. The extension of the floods’ effects on other reefs in the southern coast of Mozambique is discussed along with a proposed monitoring program for this reef.