Spatial and temporal variations of faecal indicator bacteria in Lake Bunyonyi, South-Western Uganda

Abstract Background Microbial water quality serves to indicate health risks associated with the consumption of contaminated water. Nevertheless, little is known about the microbiological characteristics of water in Lake Bunyonyi. This study was therefore undertaken to examine the spatial and temporal variations of faecal indicator bacteria (FIB) in relation to physicochemical parameters in Lake Bunyonyi. Result The FIB concentration was consistently measured during sampling months and correlated with each other showing the presumed human faecal pollution in the lake. The highest concentration values for E. coli (64.7 ± 47.3 CFU/100 mL) and enterococci (24.6 ± 32.4 CFU/100 mL were obtained in the station close to the Mugyera trading centre. On a temporal basis, the maximum values were recorded during the rainy season in October 2019 (70.7 ± 56.5 CFU/100 mL for E. coli and 38.44 ± 31.8 CFU/100 mL for enterococci. FIB did not differ significantly among the study stations (p > 0.05) but showed significant temporal variations among the months (p < 0.05) with concentrations being significantly high in wet season than dry season (U = 794, p < 0.0001 for E. coli; U = 993.5, p = 0.008 for enterococci). Spearman’s rank correlation revealed that FIB concentrations were significantly positively correlated with turbidity and DO concentration levels (p < 0.05). Approximately 97.2% of the water samples had E. coli and enterococci concentrations levels below USEPA threshold for recreational waters. Likewise, 98.1 and 90.7% of samples recorded E. coli and enterococci counts exceeding the UNBS, APHA, WHO and EU threshold values for drinking water. Conclusion The FIB counts show that the Lake Bunyonyi water is bacteriologically unsuitable for drinking unless it is treated since the FIB pose health risks to consumers. Besides, the water can be used for recreational purposes

Spatial variation of nutrients and primary productivity in the Rufiji Delta mangroves, Tanzania

Determinations of spatial and temporal variations in organic matter and nutrient dynamics in water and sediments are crucial for understanding changes in aquatic bodies. In this study, we (i) determine the spatial dynamics of dissolved inorganic nutrients, during the transition from the dry to the rainy season, and (ii) provide future productivity predictions for the Rufiji Delta mangroves, Tanzania, based on the input of various nutrients. Water samples were collected from six locations, three times per year between April 2012 and January 2014, and analysed for dissolved nutrients, total organic and inorganic carbon, chlorophylla, chlorophyllband total carotenoids. The prediction of future net primary productivity in the Rufiji mangroves was undertaken using the software STELLA. The mean nutrient concentrations were of the order: nitrate &amp;gt; phosphate &amp;gt; ammonium &amp;gt; silica &amp;gt; dissolved organic carbon. The study revealed that high nutrient concentrations occurred in the northern part of the Rufiji Delta as a result of anthropogenic influence in the watershed. Modelling of nutrient inputs into the delta indicated enhanced primary productivity, which is expected to increase the vulnerability of water quality in the near future due to eutrophication.Funding Agencies|Swedish Research Links Program Africa [348-211-7408]</p

Temporal and spatial distribution of trace metals in the Rufiji delta mangrove, Tanzania

Spatial and temporal distribution of trace metals and their cycling is a key issue for understanding the ongoing biogeochemical processes in coastal environments. Sediment cores were collected from six different sampling locations from the Rufiji delta mangrove forests in southeastern coastal Tanzania that are perceived to be impacted by urban development and agricultural activities in the catchment, and pollution in upstream sections of the Rufiji River. The chronology and sediment accumulation rates at these sampling sites were derived based on the distribution of Pb-210(excess) method. The trace metals (As, Cd, Cr, Cu, Ni, Pb, and Zn) were sequentially extracted as per the BCR method and analyzed. The results indicate that the mass accumulation rates range from 0.40 g cm(-2) year(-1) (cores NR3 and NR4) to 1.75 g cm(-2) year(-1) (core SR1). Trace metals in the cores are mainly associated with the residual phase and their abundances in sediments are ranked as Cr amp;gt; Zn amp;gt; Ni amp;gt; Cu amp;gt; Pb amp;gt; Cd. The results imply that trace metals in the Rufiji delta mangroves are mainly of crustal origin, and they are less sensitive to weathering. Further, these metals are least available for uptake by plants and they pose limited threat to the biota.Funding Agencies|Swedish Research Link project-Africa [348-211-7408]; Western Indian Ocean Marine Science Association (WIOMSA); MARG 2</p

Histomorphological Damage in the Small Intestine of Wami Tilapia (Oreochromis urolepis) (Norman, 1922) Exposed to Microplastics Remain Long after Depuration

The histopathological effects of microplastics (MPs) in the gastrointestinal tracts of fish following long-term exposure and depuration are relatively understudied. This study investigated histomorphological damage in the small intestine of Oreochromis urolepis larvae following 65 d exposure to 38–45 μm of polyethylene microspheres (PE MPs) and after a recovery period of 60 d. Larval fish were assigned to each treatment group (control, 1, 10 and 100 PE MPs), where ingestion and degenerative changes in the small intestine were examined using a routine hematoxylin and eosin staining technique. The results highlighted significant PE MPs ingestion and retention proportional to exposure dose (χ2 = 49.54; df = 2). Villi height and width and epithelial cell height were significantly affected and differed between treatment groups. Indices of damage to the small intestine organ (χ2 = 47.37; df = 2; p < 0.05) and reaction patterns of villi, epithelial, goblet and cryptic glandular cells, leucocytic infiltration and blood congestion revealed significant occurrence of alteration as PE MPs exposure dose increased. After the recovery period, no PE MPs were observed, and villi height, width and epithelial cells showed recovery with no significant difference between treatment groups. Organ indices declined (χ2 = 12; df = 2; p < 0.05) but remained significantly different between treatment groups, largely due to leucocytic infiltration (χ2 = 9.08; df = 2; p < 0.05). The study demonstrated that microplastics induced small intestinal wall degeneration, but recovery in young fish occurred slowly. The damage likely compromised its digestive function, which may affect growth and reproduction. This requires further research.publishedVersio

Impaired Growth Performance of Wami Tilapia Juveniles (Oreochromis urolepis) (Norman, 1922) Due to Microplastic Induced Degeneration of the Small Intestine

Microplastics-induced histopathological changes in gastrointestinal tracts of fish have been widely reported. However, the translation of adverse effects in the gut to impacts on growth are understudied. This study investigated the effect of MP-induced small intestinal histomorphological changes on growth performance of Oreochromis urolepis juveniles. Sixty larvae were exposed in control (0), 1, 10, and 100 polyethylene microplastic particles (PE MPs)/mL treatment groups. On day 65, juveniles were euthanized, dissected, and biometric data were taken. Small intestine histomorphological lesion index (HLI) was calculated following histological preparation using routine hematoxylin and eosin procedure. Results showed increase in HLI proportional to PE MPs exposure dose. These deteriorations equally reduced growth in final weight, weight gain and total length (One-Way ANOVA, p > 0.05), and Specific Growth Rate (SGR) (Kruskal–Wallis Test, p > 0.05), though there were insignificant differences between treatment groups. Condition factors of fishes in control and 1 PE MPs differed significantly and with other treatment groups (Tukey HSD, p < 0.05). Small intestines HLI correlated significantly with growth pattern (Spearman, r = 1.00, p = 0.01), condition factors (Pearson, r = −0.995, p < 0.05), final weight, weight gain, and total length (Spearman, r = −1.00, p = 0.01) but not with SGR. The allometric growth pattern changed towards isometric corresponding to increasing HLI. These findings suggest that MPs damaged small intestine structure and thus impaired digestion and nutrients absorption functions which disrupted growth. Such effects may impair juveniles’ ability to escape enemies, find food, and eventually reproduce, and therefore require further study.publishedVersio

Water column biogeochemistry of a pristine and a human-impacted Tanzanian mangrove system

In the framework of an ongoing EU project (PUMPSEA: “Peri-urban mangrove forests as filters and potential phythoremediators of domestic sewage in East Africa”), we compared biogeochemical characteristics of the water column in two constrasting Tanzanian mangrove systems during the dry season: (i) Mtoni, located within the perimeter of Dar es Salaam and which is subsequently under significant anthropogenic influence, and (ii) Ras Dege, a pristine site located ~30 km south of Dar es Salaam. Despite inherent differences in the environmental settings and hydrology of both systems, we wanted to evaluate whether the inputs of sewage in the impacted site would be detectable using a range of biogeochemical parameters, including physico-chemical and nutrient data, dissolved methane, concentrations and stable isotope signatures of different C and N pools (dissolved inorganic carbon, dissolved and particulate organic carbon, particulate nitrogen). Overall, our data suggest that for most of the parameters examined, the range of values and their co-variations are within the normal variability observed in relatively pristine mangrove sites, and most of the observed differences between Mtoni and Ras Dege are likely to be due to their contrasting environmental settings (e.g. salinity regime, tidal amplitude, forest/open water ratio, …). Data collected during diurnal cycles indicate the dominance of tidal effects on the biogeochemical signatures in the water column in the pristine site, and a tight coupling with processes occuring in the intertidal areas, e.g. through porewater drainage. For organic and inorganic carbon, this would imply that the variability in the sources and concentrations of these C pools is large enough to mask any additional inputs derived from other sources such as sewage inputs – such inputs may exist but biogeochemical signatures of these carbon pools per se are insufficient to trace such inputs. Distinct differences in inorganic N profiles (NH4+ and NO3-) were found and consistent with expectations, but data from other sites suggest that nutrient concentrations in itself are not necessarily a diagnostic for anthropogenic inputs. In the impacted site, photosynthesis by dense mats of benthic microalgae is sufficiently high to be traced in the water column oxygen levels and δ18O signatures, and stable isotope data on bacterial biomarkers suggest an exceptionally high dependency of sediment microbial communities on benthic primary production -at least in the surface layers. Finally, distinctly higher δ15N signatures were found in suspended matter in the impacted site, which is likely to be closely linked to anthropogenic nutrient inputs – δ15N signatures of different biological compartments therefore appear to be a potentially powerful and integrative measure of nutrient loading at the ecosystem level

Developing human capital for successful implementation of international marine scientific research projects

The oceans play a crucial role in the global environment and the sustainability of human populations, because of their involvement in climate regulation and provision of living and non-living resources to humans. Maintenance of healthy oceans in an era of increasing human pressure requires a high-level understanding of the processes occurring in the marine environment and the impacts of anthropogenic activities. Effective protection and sustainable resource management must be based, in part, on knowledge derived from successful research. Current marine research activities are being limited by a need for high-quality researchers capable of addressing critical issues in broad multidisciplinary research activities. This is particularly true for developing countries which will require the building of capacity for marine scientific research. This paper reviews the current activities aimed at increasing marine research capacity in developing and emerging countries and analyses the challenges faced, including: appropriate alignment of the research goals and societal and policy-relevant needs; training in multidisciplinary research; increasing capacity for overall synthesis of scientific data; building the capacity of technical staff; keeping highly qualified personnel in marine scientific research roles; cross-cultural issues in training; minimising duplication in training activities; improving linkages among human capital, project resources and infrastructure. Potential solutions to these challenges are provided, along with some priorities for action aimed at improving the overall research effort