Richness and distribution of Benthic Macroinvertebrates in selected waterbodies, Uganda

Abstract

Benthic macroinvertebrates are important in the functioning of freshwater ecosystems, as they regulate primary production, cleanse water, decompose organic matter, translocate materials in water, form key links in food webs, and are invaluable indicators of stream degradation. However, most of the biological conservation measures present are for other groups of aquatic organisms, like vertebrates, with limited measures present for macro-invertebrates. Legislative and institutional shortcomings regarding the protection of benthic macroinvertebrates in Uganda pose a severe threat to their protection, for they exacerbate the effects of the primary threats of pollution and habitat loss by failing to provide robust and enforceable mechanisms for their conservation and effective monitoring. The Legislative and institutional shortcomings are due to lack of organized and centralized macroinvertebrate data which hinders evidence-based policymaking and adaptive management. This study aimed at contributing information leading to the development of the first national checklist of benthic macroinvertebrates in Uganda, so as to provide reference baseline information for guiding conservation and sustainable use of aquatic ecosystems in the country. To achieve this, the study mobilized data on occurrence records from datasets available in Global Biodiversity Information Facility (GBIF), archives of biodiversity surveys conducted at the National Fisheries Resources Research Institute (NaFIRRI) in Uganda, and publications of benthic macroinvertebrate studies done in Uganda. A total of 9860 records of benthic macro-invertebrates were retrieved from 65 waterbodies, with 85% of the records from the major lakes namely: Victoria, Kyoga, Albert, George and Edward, and with 15% from the minor/satellite water bodies in the country. This study also revealed that the macroinvertebrates in the country belong to five phyla namely; Annelida, Arthropoda, Mollusca, Nematoda, and Platyhelminthes, with majority of the records belonging to Phylum Arthropoda, and Nematoda and Platyhelminthes having the least records. Also, majority (58%) of the records were identified to Genus level. In terms of diversity, more families were recorded in large waterbodies, with Victoria basin having higher taxa richness. For the records identified to species level, majority of the species with known conservation status were found to be of least concern status hence are not under threat. The study also revealed that the environmental variables that predict maroinvertebrate assemblages in Ugandan water bodies are: DO, SRP, salinity, SRSI, conductivity, SD, Turbidity, Salin, TSS, pH, NO2, Chla, TP, TN, TD, Temperature, and NH4. Regarding hotspots for biodiversity conservation at broader taxonomic levels (phylum and class), extensive systems like the Kibale swamp-river system and Lake Albert exhibited the highest diversity. At family level however, the Bwindi Impenetrable National Park rivers emerged as a unique hotspot with highest of level diversity. Also, the high proportion (58%) of geographically restricted macroinvertebrate families in Uganda indicates that Uganda's waters host many rare macroinvertebrate families. This indicates that they are extremely vulnerable, and those specific waterbodies need immediate protection to ensure these indigenous species survive. Also, the high number of Not Evaluated (NE) species (highest in Lake Victoria) points to significant knowledge gaps in basic taxonomic assessment of benthic macroinvertebrates in the country.