Study on Freshwater Macroinvertebrates of Some Tanzanian Rivers as a Basis for Developing Biomonitoring Index for Assessing Pollution in Tropical African Regions
Macroinvertebrates and physicochemical parameters were assessed at 15 sites along five rivers in Kilimanjaro region, Tanzania, with the aim of understanding their ecological status and setting a base to the development of a biological index for tropical regions. Investigated rivers that occur within Pangani basin include Karanga, Rau, Lumbanga, Sere, and Umbwe. Sampling sites were categorized according to the level of water and habitat quality as follows: reference or least impacted (4 sites), moderately impacted (5 sites), and highly impacted (6 sites) sites. A total of 12,527 macroinvertebrates belonging to 13 orders and 48 families were recorded. The highest total abundance of 4,110 individuals per m2 was found in Karanga river, while Umbwe river had the lowest with 1,203 individuals per m2. Chironomidae was the most abundant family (2,588 individuals per m2) and the least were Hydridae and Thiaridae, each having 5 individuals per m2. High numbers of taxa were noted among the orders: Ephemeroptera (8), Odonata (8), Diptera (7), and Trichoptera (6). In conclusion, orders with greater diversity of macroinvertebrate families offer a wide range of tolerance to pollution and, thus can potentially be used to develop a biomonitoring index for evaluating pollution in tropical African rivers. 1. Introduction Freshwater macroinvertebrate species are at higher risk of extinction due to habitat degradation following overwhelming human activities (i.e., invasive industrialization, agriculture, and urban development) near rivers [1–3]. It is unlikely that there is a substantial number of freshwater bodies remaining that have not been irreversibly altered from their original state as a result of anthropogenic activities [4]. In Tanzania, for example, most of the industries are located in Dar es Salaam city and mostly discharge their waste waters into Mzinga, Msimbazi, Yombo, and Kizinga rivers, which eventually discharge into the Indian Ocean [2, 5]. This, in turn, affects the occurrence, composition, and the distribution of freshwater macroinvertebrate species, depending on their levels of tolerance and adaptability [6–9]. In tropical African regions, researches on the status and trends of freshwater macroinvertebrates in rivers have not been given much attention compared to nontropical regions [10, 11]. As a result, some species may already have become extinct even before they were taxonomically classified leading to lack of taxonomical information. This situation has hindered the potential use of benthic macroinvertebrates as indicators for water quality
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