Meso-zooplankton movement through the newly constructed Mfolozi channel into and out of the St Lucia Estuary, South Africa

Biodiversity census of Lake St Lucia, iSimangaliso Wetland Park (South Africa): Gastropod molluscs

“…Since the end of 2011, the system has entered a wet phase, with above average rainfall leading to occasional flooding and the prevalence of oligo- to polyhaline conditions throughout the extent of the system. This was compounded by the excavation of a beach spillway in July 2012, which has since contributed substantial freshwater inflow from the Mfolozi River into the St Lucia system and also partial exchange of water with the open ocean ( Nel 2014 , van Elden et al in press ). These changes have led to the appearance of a number of new gastropod species of brackish to freshwater origin, including Bulinus natalensis , Cassidula labrella , Melampus parvulus , Melampus semiaratus and Melanoides tuberculata (Figure 2 ).…”

Zooplankton dynamics during a regime shift in the St Lucia Estuary, South Africa.

“…Zooplankton play an essential role in linking primary producers (phytoplankton) to higher trophic levels (Hays et al 2005, Carrasco et al 2011, Rice et al 2013. They also aid in the transfer of energy between benthic and pelagic environments (Wooldridge 1999, Van Elden et al 2014, Taylor 2006) through diel-vertical migration (Gibbons 1997 which is common in most zooplankton species (Gibbons 1997). Diel vertical migration occurs when zooplankton migrate to the surface waters during the night to feed and return to the bottom during the day in an effort to escape visual predators (Gibbons 1997, Wooldridge 1999.…”

“…Additionally, a beach spillway was created in 2012 to link the Mfolozi River to St Lucia at the mouth to allow for freshwater input and sea water input when the Mfolozi mouth was open to the sea (Whitfield et al 2013, Tweedley et al 2019). The beach spillway was successful in the recruitment of marine, estuarine and freshwater species; however, the channel would close during periods of low rainfall (Van Elden et al 2014, Tweedley et al 2019). The Mfolozi River has one of the highest silt loads in comparison to other estuaries in South Africa (Carrasco et al 2007, Nhleko et al 2012, Jones 2015.…”

“…During past harsh drought conditions in the St Lucia Estuary, the lower reaches of the system were dominated by resident estuarine taxa including the estuarine calanoid copepods Pseudodiaptomus stuhlmanni, Acartiella natalensis and the mysid Mesopodopsis africana (Carrasco et al 2010. The beach spillway which was constructed in 2012 facilitated recruitment into the estuarine system from the Mfolozi River and the Indian Ocean during open mouth conditions but used to close under low rainfall conditions (Van Elden et al 2014, Tweedley et al 2019). In the current study, taxa richness increased at the mouth during May 2015 as a result of marine intrusion through the beach spillway as the Mfolozi River mouth was open to the sea.…”

“…and post beach spillway(Van Elden et al 2014). The full relinkage of the St Lucia-Mfolozi link at the mouth area has provided an opportunity to study the impacts of increased freshwater input to the estuarine system.…”