Reliability of the Tanzania river scoring system (TARISS) macroinvertebrate index of water quality: a case study of the river Mpanga system, Uganda

Abstract

Uganda does not have a biomonitoring system for assessing the water quality of its rivers basing on benthic macroinvertebrates. An alternative system has been suggested in Tanzania. Differences in characteristics between Tanzania and Uganda may contribute to differences in the physical and chemical characteristics of rivers between the two countries, resulting in variations in macroinvertebrate assemblages and sensitivity levels in relation to disturbance. River Mpanga lies along the equator in western Uganda and shows heterogeneity of impacted and non-impacted sites along its course. The disturbance gradient of River Mpanga was determined using habitat integrity scores. The ability of the Tanzania River Scoring System (TARISS) to distinguish test from reference sites using macroinvertebrate assemblages was validated. Both qualitative and quantitative data were obtained through purposive sampling in both the wet and dry seasons. Macroinvertebrates were sampled following a slightly modified TARISS protocol. Canonical analysis of principle coordinates (CAP) showed that macroinvertebrate assemblages vary along a disturbance gradient, grouping test sites distinct from reference sites. Of the TARISS metrics, average score per taxon was able to distinguish between test and reference sites (p = .009) among the TARISS metrics. Five taxa not included in TARISS were found in river Mpanga and were assigned sensitivity scores based on CAP predictive model in PERMANOVA. It was concluded that TARISS could be reliable for eastern African river systems but should be updated and/or modified by users in different regions to include missing taxa.

Keywords:

• Biomonitoring
• macroinvertebrates
• freshwater
• disturbance gradient
• bioassessment
• River Mpanga

Acknowledgment

Field assistance from Mr. Muhairwe Godwin during data collection was appreciated.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes on contributors

Julius Tumusiime is interested in freshwater studies, ecology, parasitology, and conservation. He holds an MSc. in Biology (Natural resources' ecology, management and conservation) since 2017.

Dr. Casim Umba Tolo is Senior Lecturer in the Department of Biology, Faculty of Science, and the Center Leader/Director of Pharmbiotechnology and Traditional Medicine Center (PHARMBIOTRAC), under the Eastern and Southern Africa Higher Education Centers of Excellence (ACE II) at Mbarara University of Science and Technology, Uganda. He holds M.Sc. and Ph.D in Biology. He has wide research experience and published articles in peer-reviewed journals and has contributed book chapters in the areas ranging from Conservation Biology, Ecology, Environment, Climate Change Adaptation and Indigenous Knowledge Systems.

Marie Claire Dusabe currently serves as bat project coordinator under the Rwanda Wildlife Conservation Association (RWCA). She has a master's in Biology (Natural resources ecology management and conservation) and has served as researcher in the field of environmental conservation especially freshwater quality and macroinvertebrates taxonomy since 2013. Claire became fascinated with environmental conservation as a researcher in the field school held in Uganda where best students from Umutara Polytechnic in wildlife and aquatic resources management were invited to attend the international field school regarding environmental conservation. Claire got her first grant in Congo Basin grant Program in 2016 about Assessment of water quality and macro-invertebrates diversity of a major tributary to ancient Lake Tanganyika, the Rusizi catchment; as the project investigator she was in charge of coordinating the team of research assistants for the field and laboratory work. Her dreams since she was young was being a good biologist. Marie Claire can be reached by email at [email protected].

Christian Albrecht is interested in biodiversity, evolution and biogeography of African freshwater invertebrates.