Study on Freshwater Macroinvertebrates of Some Tanzanian Rivers as a Basis for Developing Biomonitoring Index for Assessing Pollution in Tropical African Regions

Abstract

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.

Assessment of Water Quality Across Irrigation Schemes: A Case Study of Wetland Agriculture Impacts in Kilombero Valley, Tanzania

“…In addition, Sululu being close to Ifakara town, besides irrigation related factors, is impacted by human activities along the stream, such as washing clothes and discharge from untreated wastewater. Similar discussion was shared by Minaya et al [11] and Elias et al [12], who found most rivers located near towns to be more polluted compared to peripheral streams. It is difficult to disentangle all the human activities in the landscape to isolate the direct role of agrochemicals in determining water quality in multiuse regions like Kilombero Valley.…”

“…These taxa have a potential for biomonitoring, as their fluctuation can be related to human impacts [60]. Such observations have been recorded in similar tropical rivers in some parts of Tanzania [12,29]. In our study, Hemiptera, Odonata and Ephemeroptera were dominant in upstream Sites 1 and 2, indicating good water quality.…”

“…In our study, Hemiptera, Odonata and Ephemeroptera were dominant in upstream Sites 1 and 2, indicating good water quality. Similarly, Elias et al [12] found the benthic communities of Pangani Basin streams to be dominated by Hemiptera, Odonata and Ephemeroptera, expressing to be good and slightly polluted water categories. Diptera (Chironomidae) and Annelida (Hirudinea) were present at Sululu stream and downstream sampling sites indicating pollution.…”

“…This in turn can allow us to track changes affecting wetland ecosystem function and biodiversity at higher trophic levels and across larger scales, thereby providing useful early warnings to help avoid widespread degradation under widespread agricultural intensification.Water 2019, 11, 671 2 of 22 extent and magnitude of impacts of anthropogenic activity at small scales to support management decisions and avoid compounded impacts at larger scales.Usually, the main source of agricultural irrigation water in wet landscape environments comes from surface water. Because of spatial variation of water chemistry in wetlands, streams and rivers, assessment and monitoring programs are necessary to provide robust insights into the quality and quantity of surface water supplies [11][12][13]. Increased use of chemicals and excess draining of wetlands for agriculture and the associated irrigation can have impacts not only on aquatic ecosystem, but also on human health.…”

“…Usually, the main source of agricultural irrigation water in wet landscape environments comes from surface water. Because of spatial variation of water chemistry in wetlands, streams and rivers, assessment and monitoring programs are necessary to provide robust insights into the quality and quantity of surface water supplies [11][12][13]. Increased use of chemicals and excess draining of wetlands for agriculture and the associated irrigation can have impacts not only on aquatic ecosystem, but also on human health.…”