Abstract
Salinity is an important factor affecting freshwater aquatic species distribution and diversity. The semi-arid Eastern Cape Karoo region of South Africa has been earmarked for shale gas development through hydraulic fracturing. The process uses large amounts of water and produces briny wastewater. When not managed properly, these wastewaters may lead to salinisation of surface freshwater bodies in the region. Therefore, the effect of salinity on the hatching success of crustacean resting eggs was examined using sediments from four depression wetlands found in the region. The sediments were exposed for 28 days to salinity levels of 0.5 g L−1, 2.5 g L−1, 5 g L−1 and 10 g L−1. Control aquaria in which no salt was added were also set up. There was a significant decrease in the emerged taxa richness and abundances at salinities of 2.5 g L−1 and above. Anostraca, Notostraca and Spinicaudata hatchlings were abundant at salinities of 0.5 g L−1 and below, while Copepoda, Daphniidae (Cladocera) and Ostracoda were observed in the highest salinity, but their densities were still lower with increased salinities. Given the importance of large branchiopods in the trophic balance of depression wetlands, their loss may alter the ecological balance and function of these ecosystems.
Highlights
Salinity is an important factor affecting freshwater aquatic species distribution and diversity
Et al.[16] stated that there is potential for increasing salinity in freshwater rivers and wetlands to decrease the species richness of aquatic communities, South African Research Chairs Initiative, Shallow Water Ecosystems, Nelson Mandela University, P.O
The geographical location of the depression wetlands and the key variables measured during the 2014/2015 wet season sampling (November and April representing periods of maximum precipitation) are presented in Supplementary Table S1
Summary
Salinity is an important factor affecting freshwater aquatic species distribution and diversity. Increased salinisation resulting from land-use change is most likely to occur in semi-arid or arid regions of the world[8,9] Wetlands in these areas occasionally experience periods of higher salinity under natural conditions, because of the high evaporative conditions and the variability of inflows[9]. The Eastern Cape Karoo region of South Africa has recently been earmarked for shale gas exploration using the hydraulic fracturing technique[11,12] This process involves high amounts of water and disposal of briny wastewater[13], which when not managed properly may find its way into freshwater systems. Et al.[16] stated that there is potential for increasing salinity in freshwater rivers and wetlands to decrease the species richness of aquatic communities, South African Research Chairs Initiative, Shallow Water Ecosystems, Nelson Mandela University, P.O. Box 77000, Port Elizabeth, 6031, South Africa. Endorheic wetlands are potentially at higher risk of salinisation than flow-through systems, as there is no salt removal mechanism within them[9]
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