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 m 2 was found in Karanga river, while Umbwe river had the lowest with 1,203 individuals per m 2 . Chironomidae was the most abundant family (2,588 individuals per m 2 ) and the least were Hydridae and Thiaridae, each having 5 individuals per m 2 . 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.

The World is transforming more rapidly than ever before as a result of urbanization and industrialization. Such unrelenting destruction of nature has surpassed the capacity of mother Earth to support the aquatic ecosystem. Apart from freshwater macroinvertebrate species, there is no single measure of declining freshwater ecosystem that can capture either the short and long-term changes or the trend of overall freshwater ecosystem health. In that regard, the macroinvertebrates and physico-chemical variables were used as surrogates to determine levels of impairment within and between Pangani and Wami-Ruvu rivers' basins in Tanzania. Spatial distribution of macroinvertebrate communities in the basins is significantly influenced by varying levels of environmental variables as a result of geomorphology and improper land uses. Principal Components Analysis (PCA) ordination showed two distinct patterns of biometrics that clearly discriminate reference sites from monitoring sites at each basin and consequently demonstrate the differences in water quality and physical habitat between the site categories. Similarly, distinctive macroinvertebrate species were observed and varied considerably among the site categories in the studied rivers as a function of tolerance levels. Impacted sites are characterized by either absence of any sensitive taxa or presence of few if any; greater dominance of only a few taxa that are tolerant to pollution. Therefore, the more diverse orders with a wider range of occurrences and tolerance to pollution (Ephemeroptera (E), Diptera (D), Odonata (O) and Trichoptera (T)) can be considered as potential bio-indicators in developing biomonitoring index for Tropical African Rivers as they showed a significant discriminating power that separated reference from monitoring sites.

No abstract

Acute toxicity test was performed to determine the sensitivity of Neorpela spio, Baetis harrisoni, and Tubifex spp. to nitrates (NO3-N) and phosphates (PO4-P) with different concentrations after 96 hours of exposure time. The observed lethal effects and/or mortality increased with concentration and exposure time among tested species of different sensitivities. The results demonstrated that both nitrate and phosphate are toxic to the three studied organisms under the test conditions, with Neorpela spio displaying the highest acute effect in water with nitrate and phosphate compared with Baetis harrisoni and Tubifex spp. The 100% cumulative mortality was experienced at 3.2 mg NO3-N/L and 2.4 mg PO4-P/L for N. spio, 5.6 mg NO3-N/L and 4.8 mg PO4-P/L for B. harrisoni, and 128 mg NO3-N/L and 24 mg PO4-P/L for T. spp. However, N. spio and B. harrisoni showed high mortality at the Tanzanian nitrate recommended lower and maximum limits of 10 and 75 mg NO3-N/L, respectively, for drinking water and significant mortality at the recommended limits of nitrite (20 mg NO3-N/L) and phosphorus (6 mg PO4-P/L) concentrations for municipal and industrial wastewaters. Therefore, there is a need for these Tanzanian recommended nitrate ranges for drinking water of 10 to 75 mg NO3-N/L and 20 mg NO3-N/L and 6 mg PO4-P/L for municipal and industrial wastewaters to be refined for the betterment of protecting both human health and riverine organisms.