African Journal of Aquatic Science ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/taas20 Species composition and distribution of mayflies (Ephemeroptera) in relation to land use systems along the Thika River, Kenya C Maina, BM Mwangi & JJ Jumbe To cite this article: C Maina, BM Mwangi & JJ Jumbe (2021): Species composition and distribution of mayflies (Ephemeroptera) in relation to land use systems along the Thika River, Kenya, African Journal of Aquatic Science, DOI: 10.2989/16085914.2020.1842169 To link to this article: https://doi.org/10.2989/16085914.2020.1842169 Published online: 26 Feb 2021. Submit your article to this journal View related articles View Crossmark data Full Terms & Conditions of access and use can be found at https://www.tandfonline.com/action/journalInformation?journalCode=taas20 African Journal of Aquatic Science 2021: 1–10 Copyright © NISC (Pty) Ltd Printed in South Africa — All rights reserved AFRICAN JOURNAL OF AQUATIC SCIENCE This is the final version of the article that is published ISSN 1608-5914 EISSN 1727-9364 ahead of the print and online issue https://doi.org/10.2989/16085914.2020.1842169 Species composition and distribution of mayflies (Ephemeroptera) in relation to land use systems along the Thika River, Kenya C Maina1, BM Mwangi2* and JJ Jumbe1 1 Department of Zoological sciences, Kenyatta University, Nairobi, Kenya 2 Department of Physical and Biological Sciences, Murang’a University of Technology, Murang’a, Kenya *Correspondence: [email protected] Mayflies (order Ephemeroptera) are widely distributed and commonly used in biological assessment of water quality because of their sensitivity. Their application as bio-indicators in tropical streams and rivers, however, is hampered by lack of adequate information about their status in many such ecosystems. The current study investigated their species composition, distribution and abundance in relation to land use and water quality characteristics of the Thika River, Kenya. The Thika River emanates from the Aberdare Ridges and flows through forest, agricultural and urban catchments. Sampling was carried out at three sites representing forest, agricultural and urban land use systems. Dissolved oxygen, conductivity, total dissolved solids, temperature and transparency were measured in situ at each sampling station. Macroinvertebrates were sampled using a modified Hess sampler and the Ephemeropterans were later identified and sorted in the laboratory. Thirteen Ephemeroptera genera belonging to six families were obtained. Mean larvae abundance was 1 238 ind. m−2. Acanthiops (70.4%) and Afronurus (13.3%) dominated the community at all sites. The current study revealed that decreasing Ephemeroptera taxa abundance along the river channel indicates decreasing water quality. Keywords: abundance, Acanthiops, Afronurus, macroinvertebrates, water quality Introduction Good water quality is essential because it maintains the (Schloesser and Nalepa 2002). Mayflies play an essential ecological processes that support aquatic biodiversity. role in almost all undisturbed freshwater communities, Rivers emanating from forested catchment areas are and their larvae frequently form a considerable part of generally of good water quality, as a result of minimal the material sampled during bio-monitoring procedures human activities (Garcia et al. 2014). However, declining (Bauernfeind and Moog 2000). In tropical areas, the method water quality as a result of environmental perturbation has been given less attention while most water quality affects the stability of the biodiversity, hence hindering the assessments are done using the physical and chemical ecosystems services and functions of aquatic ecosystems processes. Aschalew and Moog (2015) found that until (Ndung’u 2014). Water quality deterioration is, therefore, present, conventional physico-chemical techniques are used a significant threat in many rivers (Ndaruga 2004; Arimoro in some streams for monitoring the river water quality. The et al. 2007), which is as a result of growth in human current study therefore aimed at investigating the community population (DeSA 2013). In particular, industrialization, structure of mayflies in relation to water quality changes urbanization and agricultural activities have led to along the Thika River, Kenya. This is by first assessing increased nutrient levels in the water bodies (Heathwaite the water quality status of the Thika River as it flows et al. 1996). The Thika River emanates from a heavily downstream through the various land use systems, and forested catchment and then flows through various land relating this to the composition, distribution and abundance use types including large coffee plantations, horticultural of Ephemeroptera in relation to water quality changes. and animal farms, where it is heavily impacted by agricultural, industrial and domestic pollution. Materials and methods The method of water quality assessments using macroinvertebrates as indicators has been widely exploited Study area in temperate areas. Ephemeroptera is a widely distributed The centroid for the Thika River catchment lies at order of insects with >2 500 described species worldwide 36°47′31.3″ E, 0°46′52.2″ S (Figure 1). Annual precipitation (Hubbard 1990). There are 23 families and 371 genera and temperature are relatively stable with the coolest worldwide (Hubbard 1990). In Lake Erie, Ephemeroptera months occurring from June to August. The hottest air is successfully utilised in bio-monitoring (Schloesser and temperatures are normally from December to March. Nalepa 2002). A recent study showed peak emergence The average annual rainfall in Thika Town and its of burrowing mayfly nymphs (Hexagenia spp.) that was surrounds ranges between 900 and 1 250 mm per year. associated with an improvement of the ecosystem health Lake Ol-borosat influences the hydrology of Aberdare African Journal of Aquatic Science is co-published by NISC (Pty) Ltd and Informa UK Limited (trading as Taylor & Francis Group) Published online 26 Feb 2021 2 Maina, Mwangi and Jumbe 36°48′ E 36°54′ E 37° E 37°6′ E LEGEND 1. Abadare Ranges 2. Gatanga Estate Rivers 3. Makongeni Estate KIKUYU Dam ESCARPMENT FOREST Kangare Forest 1 Ndakaini Coffee plantation and Kigumo 0°48′ S Dam holticultural farm Pineapple plantation Ndakaini Urban center Kariua Settlements Thika River Towns Kaguthi Kandara Gakoe Gatitu 0°48′ S Kamunyaka Githunguri Kiriko Ndungu Gacharage Karatu Muruka 2 Kibuu Kairi Kabati Ritho Gatukuyu Murang’a Nyamangara Thika River MURANG’A Mangu Del Monte Kenya Gatundu 1° S COUNTY ’ Pineapple farm Gatundu Mutomo 3 KIUMBA Juja COUNTY Thika Town Kimunyu See enlarged area Ndarugu 1°6′ E AFRICA KENYA Kalimoni Kenya 0 400 800 km Figure 1: Map of study area showing sampling sites 1, 2 and 3 within the Thika catchment in Muranga county, Kenya. Site 1 was surrounded by natural forest in the Aberdare ranges, Site 2 by agricultural farmlands and Site 3 by industrial and urban settlements ranges region, and the natural forest vegetation, both Murang’a-Kiambu and empties in River Tana. The river of which impact on the process of evapotranspiration. substratum consists mainly of a mixture of red volcanic, This eventually produces precipitation in the region. The black cotton soils and murram. Decomposing macrophytes precipitation replenishes the underground water content and plant remains also form part of the river substrate. that feeds the river (Kotchoni et al. 2019). The river is Three sites were selected along this river system from the also fed by surface runoff that is often contaminated forest to the downstream reaches. with agrarian, municipal and industrial effluents (Kimani The Thika River is impacted heavily by industrial and et al. 2016). The river flows through the bounder of domestic wastes as it flows downstream from its source African Journal of Aquatic Science 2021: 1–10 3 (Karuri et al. 2003). For instance, the levels of heavy metals of disappearance and reappearance recorded (Wetzel at a downstream site near Blue Post hotel were found to 2000). Water temperature was measured using a pocket be higher than levels at upstream sites (Karuri et al. 2003). thermometer. Water conductivity, pH and total dissolved Inoti et al. (2012) found out that the concentration of heavy solutes (TDS) were measured using a multi-probe meter metals like iron, cadmium, chromium, and lead in the soil (Hanna Instruments Model H199130, Romania). DO was along the Thika River catchment areas was above the measured using a portable dissolved oxygen meter (MRC, maximum permitted levels. model DO-5510, UK). Three readings were taken per Site 1 is located approximately 1 km from the river’s sampling event. source (Figure 1). The shallower river channel is heavily Macroinvertebrates were collected using a disturbance shaded by the thick forest canopy, with more exposed pools removal sampling technique (DRST) (Kage 2003) and at various points along its reaches. The dominant water a Hess sampler was used in shallow sites with a rocky flora was sub-merged and floating macrophytes, such as substrate. An Eckman grab sampler was used on deeper Azolla africana, Salvania molesta and Nymphaea lotus. sites with a muddy substratum. At each sampling site, three Emergent macrophytes were also present, for instance, samples of macroinvertebrates were collected. These were Vossia cuspidate, Pycreus lanceolatus and Scirpus jacobi. from the middle and approximatly 1 m from the left and right The streambed is granite with fallen