Abstract
This study aims to investigate macroinvertebrate assemblage structure and composition across the three major waterbody types (temporary rivers, depression wetlands and semi-permanent dams) of the Eastern Cape Karoo, and to identify important environmental and spatial correlates of macroinvertebrate assemblage composition in the region. A total of 33 waterbodies (9 dams, 13 depression wetlands and 11 rivers) were sampled. Altogether, 91 taxa were recorded in November 2014 and 82 in April 2015. Twenty-seven taxa were common to all three waterbody types (across both sampling occasions), with 17 of these observed in November and 19 in April. The ANOSIM tests revealed significant differences in assemblage composition between the depression wetlands and rivers for both sampling occasions, but dams did not differ from the other waterbody types. SIMPER analyses indicated that the notonectid Anisops varia and the corixid Micronecta scutellaris were abundant across all three waterbody types during both sampling occasions. The mayfly Cloeon africanum and the damselfly Pseudagrion sp. were abundant in river habitats during both sampling occasions, while the gastropod mollusc Bulinus tropicus and the copepod Lovenula falcifera best characterised depression wetlands on both occasions. Non-metric multidimensional scaling ordination highlighted a clear separation of assemblages between November and April, while distance-based Redundancy Analysis revealed that conductivity, altitude, turbidity and pH were the most important variables explaining the variation in macroinvertebrate assemblage patterns. These results provide baseline information which is important for future biological monitoring of impacts associated with hydraulic fracturing activities and climatic changes in the region.
Highlights
Sustainable utilisation of freshwater systems requires knowledge of the spatial distribution of different water body types, the variability of their physico-chemistry across the landscape and the net contribution of each to catchment biodiversity [1]
Permission for fieldwork and scientific collection of macroinvertebrates in the Eastern Cape Karoo region earmarked for shale gas exploration was granted by the Eastern Cape Department of Economic Affairs, Environmental Affairs and Tourism (Cacadu Region) and access to privately owned land in the province of the Eastern Cape was granted by AGRI Eastern Cape
All sites are located in an area of approximately 2 000 km2, bounded by the towns of Aberdeen in the west and Tarkastad in the east, and covering the bulk of the Eastern Cape Karoo region earmarked for potential shale gas exploration (Fig 1; see S1 Table for site coordinates)
Summary
Sustainable utilisation of freshwater systems requires knowledge of the spatial distribution of different water body types, the variability of their physico-chemistry across the landscape and the net contribution of each to catchment biodiversity [1]. Inland waters are becoming increasingly threatened by anthropogenic activities such as water pollution, flow modification, destruction or degradation of habitat, invasion by exotic species, non-point impacts associated with land-use changes in catchments [10], and more recently, large-scale intensive hydraulic fracturing for shale gas extraction [11]. Despite their apparent vulnerability, there is little published information on the general ecology and biodiversity of small nonperennial freshwater systems characterising semi-arid regions, in southern Africa [12,13,14]. The important role of dams as biodiversity refugia in semi-arid areas is becoming recognised, given that they increase the availability of permanent or semi-permanent aquatic habitat and area of occupancy for many invertebrate species that rely on a more permanent aquatic medium for survival [27, 28]
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