Assessment of the Geochemical Characteristics of Water and Surface Sediments of Rufiji Mangrove Forest, Tanzania

This study was carried out to investigate the geochemical characteristics of the Rufiji mangrove systems using mineralogy and heavy metal analyses. Rufiji mangrove sediments showed predominance of fine grain size fractions with silt as the major component. Stoichiometric ratios of nutrients revealed phosphorus enrichment in Rufiji sediment. The overall order of heavy metal concentrations in sediments was: Fe > Mg > Mn > Zn > Cr > Ni > Pb > Cu > Co > Cd. There was no relationship between grain size and some of the heavy metal concentrations, except for Co, Cr, Fe, and Mg which negatively correlated with sand, and positively correlated with silt. The findings indicated minor enrichments for Pb and Zn, and no enrichment for all other metals. The estimated geo-accumulation index demonstrated very low values (Igeo < 0) in almost all metals, except Zn (Igeo > 1.0) at station 3, indicating that sediments of the Rufiji mangrove ecosystem are unpolluted to moderately polluted. Ongoing research on the transport of nutrients, distribution and behaviour of anthropogenic chemicals throughout the estuary, and over different seasons, may provide further insights on the processes and factors which modulate the spatial and temporal variability in geochemistry of this rich and diverse tropical estuarine system. Keywords: Rufiji mangrove; Enrichment factor; Geoaccumulation index; heavy metal

Levels of selected toxic and essential elements in fish and oysters from Western Indian Ocean, Coast of Tanzania

Concentrations of toxic and essential elements in selected finfish and shellfish collected from Dar es Salaam and Tanga, Indian Ocean coast of Tanzania are presented. The elemental concentrations were determined using Energy Dispersive X-ray Fluorescence (EDXRF) spectrometer coupled with X-lab ProTM software. The mean concentrations of metals observed in finfish and shellfish collected from Tanga ranged from 3.40–5.75, 1.8–37.17, 3.5–7.1, 0.6–1.3, 0.53–0.73 and 16.80–96.70 mg kg–1 for As, Cu, Mn, Ni, Pb and Zn, respectively. For Dar es Salaam, the mean concentrations of metals ranged from 3.34–9.46, 2.90–30.53, 3.4–6.9, 0.7–1.0, 0.57–0.80 and 14.2–100.90 mg kg–1 for As, Cu, Mn, Ni, Pb and Zn, respectively. Thumbprint emperor showed the highest levels of Cu and Ni; octopus showed the highest values of As and Pb, while sardines showed the highest level of Mn. Oysters, used as pollution indicators in this study showed the highest elemental concentrations and exceeded their mean levels in finfish from Dar es Salaam by factors of 1.30, 7.15, 6.27, 2.72, 1.29 and 35.57 for As, Cu, Mn, Ni, Pb and Zn, respectively. In samples from Tanga, the metal concentrations in oysters were several times higher (3.76, 17.68, 1.12, 3.89, 1.88 and 66.92 for As, Cu, Mn, Ni, Pb and Zn) than in finfish, respectively. Based on metal concentrations in oysters, it can be concluded that coastal waters are contaminated with heavy metals. However, with an exception of arsenic and copper, the elemental levels in finfish are within the maximum permissible levels recommended by various international standards and guidelines. Keywords: Finfish, toxic elements, essential elements, pollution, EDXR

Variation of Proximate Contents in Selected Marine Fish from Tanzanian Coast due to Seasonality and Processing Methods

The effect of seasonality (wet and dry seasons) and processing treatments (frying and boiling) on proximate composition of selected fish species (Alectis ciliaris, Lethrinus harak, Rastrelliger kanagurta and Siganus canaliculatus) from Tanzania marine waters were assessed. The proximate composition of fish was proved to be altered by the fish feeds, salinity, geographical location, seasons and processing methods. Therefore, the fish samples were purposively collected from four selected locations (Tanga, Bagamoyo, Dar es Salaam and Mtwara) and treated as appropriately. Proximate parameters were determined using AOAC standard methods. The proximate contents varied with changing seasons in all the fish species. Crude protein and lipid contents increased in wet season while moisture and ash contents increased in dry season. The effect of changing seasons in proximate contents was significant (p < 0.05) except in ash. Frying process had a significant effect (p < 0.05) on proximate contents in the fish species than boiling process except in ash. The derived model accurately predicted the extent of variation of proximate contents with both dry and wet seasons and processing treatment in particular frying. However, it failed to predict the extent of variation of lipid, crude protein and moisture with boiling treatment. Further research is needed to establish the extent of variations of proximate contents due to other processing methods such as steaming and microwaving

Microplastics in agriculture – a potential novel mechanism for the delivery of human pathogens onto crops

Mulching with plastic sheeting, the use of plastic carriers in seed coatings, and irrigation with wastewater or contaminated surface water have resulted in plastics, and microplastics, becoming ubiquitous in agricultural soils. Once in the environment, plastic surfaces quickly become colonised by microbial biofilm comprised of a diverse microbial community. This so-called ‘plastisphere’ community can also include human pathogens, particularly if the plastic has been exposed to faecal contamination (e.g., from wastewater or organic manures and livestock faeces). The plastisphere is hypothesised to facilitate the survival and dissemination of pathogens, and therefore plastics in agricultural systems could play a significant role in transferring human pathogens to crops, particularly as microplastics adhering to ready to eat crops are difficult to remove by washing. In this paper we critically discuss the pathways for human pathogens associated with microplastics to interact with crop leaves and roots, and the potential for the transfer, adherence, and uptake of human pathogens from the plastisphere to plants. Globally, the concentration of plastics in agricultural soils are increasing, therefore, quantifying the potential for the plastisphere to transfer human pathogens into the food chain needs to be treated as a priority

Citizen scientist monitoring accurately reveals nutrient pollution dynamics in Lake Tanganyika coastal waters

Several studies in Lake Tanganyika have effectively employed traditional methods to explore changes in water quality in open waters; however, coastal monitoring has been restricted and sporadic, relying on costly sample and analytical methods that require skilled technical staff. This study aims in validating citizen science water quality collected data (nitrate, phosphate and turbidity) with those collected and measured by professional scientists in the laboratory. A second objective of the study is to use citizen scientist data to identify the patterns of seasonal and spatial variations in nutrient conditions and forecast potential changes based on expected changes in population and climate (to 2050). The results showed that the concentrations of nitrate and phosphate measured by citizen scientists nearly matched those established by professional scientists, with overall accuracy of 91% and 74%, respectively. For total suspended solids measured by professional and turbidity measured by citizen scientists, results show that, using 14 NTU as a cut-off, citizen scientist measurements of Sec-chi tube depth to identify lake TSS below 7.0 mg/L showed an accuracy of 88%. In both laboratory and citizen scientist-based studies, all measured water quality variables were significantly higher during the wet season compared to the dry season. Climate factors were discovered to have a major impact on the likelihood of exceeding water quality restrictions in the next decades (2050), which could deteriorate lake conditions. Upscaling citizen science to more communities on the lake and other African Great Lakes would raise environmental awareness, inform management and mitigation activities, and aid long-term decision-making

Community monitoring of coliform pollution in Lake Tanganyika

Conventional water quality monitoring has been done for decades in Lake Tanganyika, under different national and international programs. However, these projects utilized monitoring approaches, which were temporally limited, labour intensive and costly. This study examines the use of citizen science to monitor the dynamics of coliform concentrations in Lake Tanganyika as a complementary method to statutory and project-focused measurements. Persons in five coastal communities (Kibirizi, Ilagala, Karago, Ujiji and Gombe) were trained and monitored total coliforms, faecal coliforms and turbidity for one year on a monthly basis, in parallel with professional scientists. A standardized and calibrated Secchi tube was used at the same time to determine turbidity. Results indicate that total and faecal coliform concentrations determined by citizen scientists correlated well to those determined by professional scientists. Furthermore, citizen scientist-based turbidity values were shown to provide a potential indicator for high FC and TC concentrations. As a simple tiered approach to identify increased coliform loads, trained local citizen scientists could use low-cost turbidity measurements with follow up sampling and analysis for coliforms, to inform their communities and regulatory bodies of high risk conditions, as well as to validate local mitigation actions. By comparing the spatial and temporal dynamics of coliform concentrations to local conditions of infrastructure, population, precipitation and hydrology in the 15 sites (3 sites per community) over 12 months, potential drivers of coliform pollution in these communities were identified, largely related to precipitation dynamics and the land use

Urban coral reefs: Degradation and resilience of hard coral assemblages in coastal cities of East and Southeast Asia

© 2018 The Author(s) Given predicted increases in urbanization in tropical and subtropical regions, understanding the processes shaping urban coral reefs may be essential for anticipating future conservation challenges. We used a case study approach to identify unifying patterns of urban coral reefs and clarify the effects of urbanization on hard coral assemblages. Data were compiled from 11 cities throughout East and Southeast Asia, with particular focus on Singapore, Jakarta, Hong Kong, and Naha (Okinawa). Our review highlights several key characteristics of urban coral reefs, including “reef compression” (a decline in bathymetric range with increasing turbidity and decreasing water clarity over time and relative to shore), dominance by domed coral growth forms and low reef complexity, variable city-specific inshore-offshore gradients, early declines in coral cover with recent fluctuating periods of acute impacts and rapid recovery, and colonization of urban infrastructure by hard corals. We present hypotheses for urban reef community dynamics and discuss potential of ecological engineering for corals in urban areas

Assessment of the quality and quantity of organic matter in the Rufiji mangrove surface sediments using biochemical composition

This study was carried out to investigate spatial changes in the quality and quantity of sedimentary organic matter in the Rufiji mangrove system, Tanzania. Sediment samples were collected from three sampling sites. Total organic matter in mangrove sediments ranged from 7.28 ± 2.02% to 10.58 ± 1.34%. Protein concentrations varied from 1,145.33 ± 20.33 μg/g to 2,747.50 ± 25.14 μg/g in the mangrove sediments. Total carbohydrates, lipids and biopolymeric carbon in mangrove sediments ranged between 1,110.50 ± 16.31 μg/g and 1,914.17 ± 27.79 μg/g, 1,436.50 ± 24.13 μg/g and 6,373.50 ± 25.79 μg/g, and 4,496 μg C/g and 10,231.50 μg C/g, respectively. Tannins and lignins in mangrove sediments varied from 817.67 ± 12.97 μg/g to 1786.50 ± 30.74 μg/g, while stable carbon isotope (δ13C) in Rufiji mangrove sediments ranged between –26.64 ± 0.10 ‰ and –25.48 ± 0.13 ‰. Higher protein:carbohydrate (PRT:CHO) at station 3 indicated the presence of freshly deposited organic matter. The high lipid:carbohydrate (LPD:CHO) ratios observed in the Rufiji mangrove systems pointed towards the high quality of labile organic matter which supports benthic fauna. PCA revealed the association of variables and their distribution on trends across sites of the Rufiji mangrove system. Keywords: Organic matter, biochemical composition, Rufiji, mangroves, sediments &nbsp

Variability of Selected Mineral Contents in Marine Fish from Local Markets in Tanzania

Mineral contents (K, Na, Ca and Mg) in selected marine fish species (Alectis ciliaris, Lethrinus harak, Rastrelliger kanagurta and Siganus canaliculatus) from local fish markets were analysed in wet and dry seasons. The processing methods (frying and boiling) were also assessed for their influence on the mineral contents. Samples were randomly collected from Tanga, Bagamoyo, Dar es Salaam and Mtwara seaports, analysed using established methods and determined by Graphite Furnace Atomic Absorption Spectrometry. Mean mineral contents in individual and all analysed fish species were high during dry season compared to wet season except Ca and the difference was statistically significant (p fried > boiled), while those of Ca were similar. Mineral contents in all fish species between raw and frying as well as between raw and boiling processing methods varied significantly for K only. Variation of mineral contents in all fish species between frying and boiling was not significant. Pearson correlations and Principal component analyses have indicated significant close relationships between minerals (except Ca) and seasonal variations. In addition, significant relationship between processing methods and K mineral only was observed. Derived models have accurately predicted variations of mineral contents due to seasons and variations of K content due to processing methods. Further research is required to determine effects of using steaming and microwaving on mineral contents and what factors control variations of Ca, Na and Mg using frying and boiling in these fish species