Effects of anthropogenic activities on macroinvertebrate assemblages in the littoral zone of Lake Hawassa, a tropical Rift Valley Lake in Ethiopia

Abstract

In developing tropical countries, the littoral region of lakes is exposed to high human pressures, and the degradation effects are more evident on riparian vegetation and macrophytes. Human impacts on other biological entities, such as plankton and macroinvertebrates, are rarely investigated and reported. The present study focuses on assessing the effects of habitat disturbance on the littoral macroinvertebrate assemblages in Lake Hawassa, Ethiopia. Samples were taken from February to November 2015/16 from 12 sampling sites purposefully selected on the basis of percentage disturbance score (PDS) and categorized into minimally disturbed (four sites), moderately disturbed (five sites) and highly disturbed (three sites). Macroinvertebrate samples were collected from each site using a D‐frame net of 500 µm, with both in situ measurement and laboratory analysis of the environmental variables being conducted. A total of 23,051 macroinvertebrates belonging to 43 families were identified. Analysis of similarities (ANOSIM) and non‐metric multidimensional scaling (NMDS) analyses revealed significantly different macroinvertebrate assemblages among the disturbance levels (ANOSIM: p = .004, R = .55). Variables such as Biological Monitoring Working Party, Shannon diversity index, Ephemeroptera and Trichoptera (ET) family richness, and family richness exhibited a flawless pattern of decrease with increasing human disturbances and a negative correlation with nutrients. The reduction of these metrics for highly disturbed sites was attributable to the deterioration of vegetation and bottom substrate qualities, increasing stormwater inputs, lack of buffer zones and well‐planned land use induced by human interventions. It was evident anthropogenic activities in and around the littoral zone of the lake contributed to the degradation of habitat quality and decreased macroinvertebrate richness and abundance. Thus, effective lake management practices are recommended to rehabilitate the degraded littoral habitat quality in order to realize the sustainable use of this natural resource.

Habitat quality–physicochemical water quality–littoral macroinvertebrate community nexus in Lugo Lake (Ethiopia): Priorities for sustainable water resources management

“…recreation), removal of macrophytes for animal fodder, artificial substrate development, human settlement, lodges, swimming and others. Our findings are in congruent with the reports of other studies conducted in Lake Hawassa (Wondmagegn & Mengistou, 2020) and European lakes (McGoff et al, 2013), which underlined the negative influence of human pressures on habitat quality of lakes.…”

“…On the other hand, FBI, which is an indicator of high pollution stress as well as presence of pollution‐tolerant macroinvertebrates, was significantly higher in oxygen‐deprived sites than relatively oxygen‐rich agricultural sites. Similar findings were also reported by Wondmagegn & Mengistou (2020). In agricultural sites, macroinvertebrate metrics, such as TR, BMWP, %EPT, D and the abundances of pollution‐sensitive macroinvertebrates (e.g.…”

“…Macroinvertebrate samples were collected along the transects of each habplot within the littoral zone of the lake using 500‐μm‐mesh size D‐Frame kick net (Wondmagegn & Mengistou, 2020). The lake bed was continuously agitated with the operator's boot to dislodge macroinvertebrates and allow them to enter into the net.…”

The effect of human disturbance on the community composition and diversity of aquatic plants in the tropical wetlands of Lake Tana, Ethiopia

“…Human disturbance altered the community compositions and reduced species richness of water birds and benthic invertebrates in the wetlands of Lake Tana (Gezie et al 2017), Alamgano, Kofe, and Kito wetlands of southwestern Ethiopian (Chawaka et al 2018), and Lake Ziway in Ethiopia (Wondmagegn and Mengistou 2020). Human disturbance can affect the aquatic plant community composition and species richness in multiple ways.…”

Application of Bipartite Networks to the Study of Water Quality

“…Water quality studies based on aquatic macroinvertebrates often use the qualitative characteristics of the BMWP index and the quantitative characteristics of the H index [3,[20][21][22][23]. The BMWP index does not consider the abundance of each taxon, and the Shannon diversity index does not consider the sensitivity/tolerance to environmental stress of indicator organisms.…”