Concentration and Biomagnification of Heavy Metals in Biota of the Coastal Marine Areas of Tanzania

The concentrations of heavy metals （As, Hg, Cr, Pb and Zn） were measured in the macroalgae, macrobenthos and fish from the Tanzanian coastal marine environment in order to ascertain the biomagnification using stable isotopes of C and N. Macroalgae samples from the central marine areas of the Tanzanian coast had higher mean concentrations of Hg （0.17 ± 0.01 μg/g） and Cr （23.7 ± 4.15 μg/g） compared to other locations. Higher concentration of Hg （0.06 ±0.02 μg/g） was detected in the Ulva fasciata close to the Msimbazi Creek in Dares Salaam, whereas the highest concentration of Cr （45.5 ± 6.83 μg/g） was found in Ulva petrusa near Dares Salaam port. The crab Portunus pelagicus collected from Pangani river estuary contained 411.5 ± 13.04 μg/g of Zn. The other metals were uniformly distributed in macrobenthos from the entire coast. Mercury and lead in the biota were found to biomagnify along the Arius dussumieri and Lethrinus lentjan food chains as suggested by the significant positive relationships between log-pollutant concentrations in fish muscle tissues vs. 615N signatures. Zinc in muscle tissues was found to be transferred along the food webs although no biomagnification was observed. Arsenic and chromium were found to decrease with the rise of the trophic position. Metal concentrations in macroalgae, macrobenthos and fish were compared with quality guidelines values by FAO （Food and Agricultural Organization） in 1983 and they all were below permissible limits for human consumption.δ

Analysis of Ground Level Ozone and Nitrogen Oxides in the City of Dar es Salaam and the Rural Area of Bagamoyo, Tanzania

From 2012 to 2015, we measured surface ozone, NOx, NO2, and NO levels at three urban sites (Mapipa, Ubungo, and Posta) and two suburban sites (Kunduchi and Vijibweni) in the city of Dar es Salaam and in the village of Mwetemo, a rural area of Bagamoyo, Tanzania. The average hourly O3 concentrations at all sites were between 9 ppb and 30 ppb during our sampling periods. O3 levels at suburban sites were generally higher than at urban sites. The average hourly concentrations in Dar es Salaam were 10 - 32 ppb, while in Bagamoyo they were 9 - 15 ppb. We observed a strong diurnal variation in Dar es Salaam while measurements from Bagamoyo showed little variation. At Dar es Salaam, the surface O3 concentrations increased from their minimum level at sunrise (around 6:00 a.m.) to a maximum in the late afternoon (around 4:00 p.m.), and then decreased toward 11:00 p.m. Another secondary ozone peak appeared between midnight and ~4:00 a.m., after which the surface ozone concentrations decreased to a minimum around 7:00 a.m. NO2 concentrations were higher at the urban sites of Ubungo and Posta, and their weekly average NO2 concentrations were 246 ppb and 118 ppb, respectively. Weekly average NOx concentrations ranged from 39.4 ppb at the Kunduchi site (suburban) to 738 ppb at the Ubungo site (urban). To our knowledge, there were few continuous measurements of ozone and nitrogen oxides concentrations in Tanzania. Since high NOx concentrations were observed, continuous air quality monitoring and effective air pollution control measures are required in Dar es Salaam to prevent further deterioration of air quality and limit the possible negative impacts on humans and vegetation.

Distribution and Speciation of Heavy Metals in Water and Sediments of the Coastal Marine Areas of Tanzania

The present study investigated the concentration and species of heavy metals As, Hg, Cr, Pb and Zn in water and As, Hg, Cr, Pb and Zn in sediments collected along the coastal marine areas of Tanzania so as to determine their behaviour and remobilization potential in the environment and the degree of their availability to edible aquatic biota for monitoring purposes. Sequential extraction revealed the presence of a significant proportion of heavy metals Cr, Pb and Zn bound to available fractions of sediments. Arsenic had the highest concentration in non available residual fractions. PCA analysis found that As-Hg, Cr-Pb were strongly correlated and that the two may be derived from the same source most likely from storm water drainage of waste water discharges, while Zn may have come from the different source like watershed erosion. Further, PCA clearly confirms the same. Generally, Zn among all heavy metals analysed was the most available to aquatic biota due to its higher average concentrations in the acid soluble fraction, followed by chromium. However, high percentages of metal species studied in Tanzania coastal marine areas were found in non available fractions which indicated that the edible aquatic biota was safe for human consumptions.

The Community of Parasites Infecting <i>Clarias gariepinus</i>in the Tanzanian Waters: A Case of Lake Victoria

Quantitative variations in parasites were investigated with respect to sex and size of Clarias gariepinus, season and localities sampled. Parasitic infection in male and female fish was not significantly different;prevalence (Man-Whitney paired sample test, U = 135.5, p = 0.7697), mean intensity (U = 136, p = 0.7829). Based on Kruskal-Wallis test analysis, the prevalence and mean intensity of five parasite species varied significantly among the three localities sampled. Adult parasites in Clarias gariepinus showed high abundance during the dry season while the larval forms showed high abundance in the wet season. In most of the parasite species analyzed the abundance varied significantly with host size. The abundance of Dolops ranarum, Paracamallanus cyatopharynx and Eumasenia bangweulensis for instance, increased with fish size, while that of Diplostomum mashonense, Tylodelphys species, Astiotrema reniferum, piscicolid leeches and Monobothrioides woodlandi increased initially but decreased as fish length reached 31 - 40 cm. Total parasite burden increased in fish of 20 - 40 cm standard length. Generally, most parasites were highly overdispersed and the negative binomial model described their distribution.

Morphometric Relationships among the Clariid Fishes of the Lake Victoria Basin, Tanzania

Six hundred and fifty-eight specimens of the Clariidae were collected from seven localities in the Lake Victoria basin and the Malagarasi wetland, Tanzania. A total of three hundred unadjusted morphometric measurements and meristic counts were analysed with the aim of assessing the adequacy of morphometric technique to delineate the clariid species occurring in theLake Victoriabasin. Results showed that morphometrics augmented by multivariate analysis (PCA, DCA and cluster analysis) amalgamated the clariid fishes into three groups, the?Clarias alluaudi/C. werneri,?C. gariepinus/C. liocephalus?andClariallabes petricola. Although other workers have used this technique, the present study concluded that, standing alone morphometrics is not a substitute for external morphology in the identification of clariid fish species, as it failed to separate the clariids into their respective taxonomic species. The technique, however, insinuates the regressional morphological relationships among the clariids occurring in the Lake Victoria basin.

Phylogenetic relationships among small <i>barbus</i>,<i>barbus</i>(actinopterygii: Cyprinidae) from malagarasi and Pangani river basins, Tanzania

The phylogenetic relationships among “Barbus” species (Barbus jacksonii, B. paludinosus and B. trimaculatus) from Malagarasi and Pangani River systems were examined by partial mitochondrial cytochrome b (cyt.b) gene. Sequences of the same samples from elsewhere in Africa obtained from the South African Institute of Aquatic Biodiversity (SAIAB’s) collection were also included in the analysis. Molecular technique was necessary due to phenotypic plasticity and extensive overlap of morphological features among the “Barbus species”. The findings of this study revealed that B. paludinosus from hale and Pangani populations occurred in two distinct genetic lineages though separated by a distance of approximately 10 km apart. Similar results were also noted amongst the population of B. paludinosus in Songati and Muumbara located on Lake Sagara in Malagarasi River basin. B. trimaculatus and B. jacksonii were indistinguishable such that it is envisaged that the two species are one and the same. The Barbus spp. from Africa included in the current study showed genetic affinity to neither European Barbus spp. nor South African redfins of the Pseudobarbus to conclude that the studied species of barbs are taxonomically quite different that needs further investigation to warrant renaming.

Metazoan Parasites of Clariid Fishes, Lake Victoria: Reflection of the Original Fauna in the Lake?

A total of 32 parasite species were documented from 658 clariid fishes examined. Thirteen species were nematodes, eleven digeneans, three cestodes, two crustaceans, and the Monogenea, Acanthocephala and Hirudinea were each represented by one species. Of the parasites recovered 16 were identified to species level, 12 to genus and 4 parasites were not identified. Most of the parasites recorded in the present study have been reported in fish ofTanzaniaand elsewhere, however, there were a few first records, and these included Neogoezia sp., Comephoronema sp., Travnema sp., Quimperia sp. and Gendria tilapiae. It is stipulated that these parasites represent the original fauna of the lake prior to introduction of the alien species. The clariid fish species investigated were a good model for studying the parasites of fish in the lake because of having a variety of parasites some of which being specific to certain clariid fishes, for instance Diplostomum and Tylodelphys species infecting only C. gariepinus and the camallanids being typical of the clariid fishes.

The Effect of Measuring Magnetic Susceptibility of Water Samples by Starting with Isothermal Remanent Magnetization (IRM) before Anhysteretic Remanent Magnetization (ARM)

Estimating magnetic properties of water samples by first measuring the Anhysteretic Remanent Magnetization (ARM) before Isothermal Remanent Magnetization (IRM) is induced has been costly due to the discard of samples measured by staring with the latter before the former. However, no clear understanding exists on the effect of measuring magnetic properties values by first inducing IRM before ARM. This study explored the effect of measuring concentration related parameters (χlf, χfd and χARM), a mineral related parameter (S-300) and grain size parameters (χfd% and χARM/SIRM ratio) fromwater samples by starting with IRM before ARM. Forty three surface water samples were collected from the estuarine of Yangtze River (China) with the aim of measuring magnetic characteristics by starting with IRM before ARM. The results indicated that, measuring magnetic properties by either starting with ARM or IRM led to similar values for χlf, χfd, χfd%, χARM, S-300 and χARM/SIRM ratio (p > 0.05). These results imply that, measuring concentrationrelated parameters does not necessarily require measuring ARM first and then IRM. Researchers can start by measuring any parameter between ARM and IRM without affecting the final results of the water samples, but with proper demagnetization when started with IRM.

基于线粒体D-loop DNA序列的瓯江口鳗鲡幼苗遗传鉴定

浙江瓯江口及邻近水域是东海诸多经济鱼类的重要栖息地。本研究对采自瓯江口6个地点,34尾玻璃鳗样本进行遗传鉴定。通过对线粒体D-loop 800 bp DNA序列分析,共检测得到34个不同单倍型,这些单倍型与GenBank中的日本鳗鲡D-loop序列相似度最高(>99%),说明这些鳗鲡为日本鳗鲡。瓯江口鳗鲡群体的单倍型多态性(Hd)为1.0±0.007,核苷酸多态性(π)为0.011±0.000 8,说明该群体的遗传变异水平较高。各采样点之间没有显著的遗传差异(FST=-0.028)。根据Tajima’s D中性检验(D=-1.982 96,P<0.01)和核苷酸错配分布结果,推测这些日本鳗鲡可能在近期发生过种群爆发性扩张。

The effects of on-farm produced feeds on growth, survival, yield and feed cost of juvenile African sharptooth catfish (Clarias gariepinus)

The culture of African sharptooth catfish(Clarias gariepinus)in most developing countries lacks suitable diets for semi-intensive production.The present study evaluated the growth performance,survival,nutrient utilization,hepatosomatic index(HSI),body composition,yield and feeding cost of African catfish fed on semi-intensive feeds 1(SMF1)and semi-intensive feed 2(SMF2)produced on-farm and an industrially manufactured(IM)feed as a control.Two hundred fish(14.95±0.24 g)were stocked in triplicate earthen ponds and fed the three diets at 5%of the body weight for eight weeks.The final weight,specific growth rate and yield of fish fed the SMF2 diet was significantly lower than SMF1 and IM diets.However,no significant differences were revelead in final weight,specific growth rate and yield between fish fed SMF1 and IM diets.The survival rate,feed conversion ratio and protein efficiency ratio of fish did not differ among the diets.Apparent net protein utilization was significantly higher on fish fed the SMF2 and SMF1 diets than IM diet.The HSI of fish fed the IM diet was significantly higher and the livers were yellow-coloured compared to smaller and brownish/reddish livers of fish fed the SMF1 and SMF2 diets.The fish fed the IM diet had statistically lower ash content than SMF1 diet.The incidence cost of fish fed the IM diet was 35%higher,while its profit index was 31%lower than fish fed the SMF1 and SMF2 diets.Taken together,African catfish farmers can reduce feed cost up to 30%by using on-farm produced feeds when formulated properly and blended without affecting fish growth performance,survival and yield while obtaining better protein retention and healthier fish.

Lipophagy is essential for lipid metabolism in fish

Lipophagy is a form of autophagy in mammals.In this cellular process,lipid droplets(LDs)are degraded through the lysosomal degradative pathway[1].During lipophagy,LDs sequestrated in autophagosomes are delivered to lysosomes,which fuse to form autophagosomes and then develop into autophagolysosomes,leading to LDs degradation of[1].A number of studies have demonstrated that lipophagy play important roles in lipid