Temporal dynamics of a subtropical floodplain pool after 2 years of supra-seasonal drought: a mesocosm study

A need exists to understand how drought and its linked consequences threaten aquatic ecosystems and their associated biota in semi-arid countries, as climate change is predicted to increase the effects of these events. South Africa experienced one of the worst droughts in its history from 2015 to 2017 and, as a result, all but the permanent waterbodies of the lower Phongolo River floodplain (PRF) in northern KwaZulu-Natal dried up. This study examined the resilience of aquatic invertebrates associated with the PRF and what the colonization and succession trends of aquatic invertebrates would be once floodplain pools were to receive water again following a 2-year drought. Water and aquatic invertebrates were collected 11 times from nine field mesocosms over a 5-week period for chemical and biodiversity analysis, respectively. Zooplankton hatched from resting stages and macroinvertebrates colonized the mesocosms from nearby permanent waterbodies within the first week of inundation, suggesting that the drought had not affected the ability of aquatic biota to continue natural colonization and succession. Although the biota appeared unaffected, an extension of such a drought could lead to habitat fragmentation and total desiccation of permanent waterbodies, potentially causing the local extinction of aquatic populations and a loss of biodiversity.