Use of Benthic Macroinvertebrate Indices as Bioindicators of Ecosystem Health for the Detection of Degraded Landscapes in Malawi

A study was conducted in Lilongwe West Rural Development Project (RDP) in central Malawi to investigate the potential use of benthic macroinvertebrates as affordable and cost-effective bioindicators of landscape degradation in Malawi. Benthic macroinvertebrates were studied in two reservoirs, Bunda and Kamuzu Dam I. A total of 778 individuals belonging to ten (10) taxonomic groups were encountered in the two reservoirs: oligochaete worms (30.70%), bivalves (15.04%), leeches (12.08%), crustaceans (11.18%), chironomids (8.99%), gastropods (8.22%), stonefly nymphs (4.24%), mayfly nymphs (3.60%), caddisfly larvae (2.70) and dragonfly nymph (2.70%). Application of t-tests on community assemblage metrics, pollution tolerance index (PTI), biodiversity and physico-chemical indices showed the two reservoirs differed significantly (p<0.05) in 69 per cent of biological indices and 11 per cent of physico-chemical indices, with Bunda reservoir having less EPT (mayflies, stoneflies, caddisflies), more oligochaete worms, more chironomid larvae, higher Simpson’s index (D), lower Simpson’s diversity index (1-D), Shannon’s index (H), Margalef’s (DMg) and Pielou’s (Jˋ) indices, lower PTI, higher percentage chironomids and lower Secchi disk visibility than Kamuzu Dam I. Results show that Bunda reservoir is fairly polluted with organic matter washed into it from the surrounding farmed landscapes through soil erosion. Deforestation and unsustainable farming practices accounted for landscape degradation around the reservoirs, while Dzalanyama Forest Reserve protected much of the Lilongwe River on which Kamuzu Dam I is located. Landscapes in the catchment area of Bunda reservoir are considered degraded and recommended for restoration through establishment of vegetative land cover. Benthic macroinvertebrates have high potential for use as biological indicators of ecosystem health for the identification of deforested degraded landscapes in Malawi and other developing countries of the tropics.