A preliminary survey and analysis of the spatial distribution of aquatic invertebrates in the Okavango Delta, Botswana

Abstract

The spatial distribution of aquatic macroinvertebrates in the Okavango River Delta, Botswana, was investigated during the lowwater period in February 2003. This complements an earlier study undertaken during high-water in June 2000. Seventy-five samples were taken in a range of aquatic habitats at 29 georeference points in four focal areas: Upper Panhandle (UPH), Lower Panhandle and Guma Lagoon (LPH), Moremi Game Reserve/Xakanaka (MGR), and Chief's Island (CI). Over 180 morphospecies (approximately 63 families) were recorded during the survey. Multivariate analyses of macroinvertebrate assemblages indicated that assemblages in each of the four focal areas were at least 54% similar at morphospecies level, and 71% similar at family level, although some taxa were more or less common in different areas. Differences in macroinvertebrate assemblages were observed amongst different habitat types, with differences most pronounced between the deltaic habitats and isolated seasonally-flooded pools and temporary rain-filled pools in MGR and CI. The highest number of taxa was recorded in the MGR (125), followed by the UPH (96), CI (93) and the LPH (89) areas. The most families were recorded in the Hemiptera (11), followed by Mollusca (10), Diptera (nine), Coleoptera (nine), Crustacea (six), Ephemeroptera (six) and Odonata (four). Three families of Hirudinea and Trichoptera, and one family of Lepidoptera, were also recorded. Hydracarina were common but not identified beyond order, while Oligochaeta were less frequently recorded. With respect to the different aquatic habitats sampled, the highest number of taxa was recorded in marginal vegetation in the channels and lagoons, although inundated floodplains, floating vegetation and marginal vegetation in backwaters also supported many taxa. The fewest taxa were recorded in sediment. This survey, whilst representing a 'snapshot' of the system under low-water conditions, highlights the importance of maintaining a mosaic of aquatic habitats in the Delta. Further studies would enhance our knowledge of the aquatic macroinvertebrate biodiversity of the Okavango Delta, thereby contributing to its conservation. (Tweddle et al. 2003) -have examined its aquatic biology.

Seasonal and spatial hydrological variability drives aquatic biodiversity in a flood‐pulsed, sub‐tropical wetland

“…, 2012). Aquatic macroinvertebrates show variation in space that has been attributed to habitat, but the drivers of change are less clear (Dallas & Mosepele, 2007). Recent developments in the hydrological modelling and mapping of the Delta (Wolski et al.…”

Spatial and Seasonal Variability in Surface Water Chemistry in the Okavango Delta, Botswana: A Multivariate Approach

“…1). Fifty sites were selected to capture a strong hydrological gradient, and built on previous aquatic research undertaken in the Delta (Ashton et al 2003;Dallas and Mosepele 2007).…”

“…Across the regions, 15 sample points were analysed from UPH, 17 from LPH, 31 from XAK, and 35 from BOR. Sample points were further characterised by the dominant habitat, including marginal vegetation in channels (MV-IC), marginal vegetation in lagoons (MV-L), floating vegetation (FV), inundated floodplains (IF), and isolated, seasonally flooded pools (SP) (after Dallas and Mosepele 2007). The first three habitat types are permanently wet (WET), while IF and SP experience wet-dry cycles (WET/DRY).…”

Biomonitoring of Mucheke and Shagashe Rivers in Masvingo, Zimbabwe Using Macro-Invertebrates as Indicators of Water Quality

“…Even though many different organisms contribute to the biodiversity of river water ecosystems, aquatic macro-invertebrates are among the most ubiquitous and diverse group of organisms in these systems because they play a central ecological role in nutrient cycling in these ecosystems [5] [6]. It is on this basis that macro-invertebrates find wide application as ideal organisms in freshwater biomonitoring studies [7].…”