Tanzanian Coast Research Articles

Excavation of the Later Stone Age Site of Madola - Kiwangwa, Bagamoyo, Tanzania

ABSTRACTReports on the Later Stone Age (LSA) assemblages along the coast of mainland Tanzania and the surrounding islands date back to the 1960s. However, most of these involved sketchy descriptions of lithic materials from varied contexts, including excavations and surface collections. Most were also by-products of accidental discoveries during other research endeavours, since no one had focused their research on the Tanzanian coastal Stone Age. Excavation of the Madola LSA site in Kiwangwa Village was aimed at addressing this problem, as well as building up a database for the Tanzanian coastal LSA industry. Unlike most areas of the Tanzanian coast where lithic artefacts occur in light scatters, the Madola site consists of a richer artefact assemblage that is comparable to those of inland sites, despite variation in artefact types and quantities. The Madola LSA assemblage predates 14,404 ± 86 BP, with quartz as the predominant raw material and bipolar flaking the main method used to produce artefacts. The site was later occupied by Plain Ware makers, after which it was abandoned until modern times.

Holocene mangrove dynamics and relative sea-level changes along the Tanzanian coast, East Africa

There is continued uncertainty regarding the rate, timing, duration and direction of Holocene sea-level for the Indian Ocean, and indeed the wider tropical realm. We present the first synthesis, and a new chronology, for Holocene relative sea-level (RSL) using a range sediment cores retrieved from mangrove ecosystems in three locations along coastal Tanzania. This study applies the relationship of ratios between the key mangrove taxa of Sonneratia:(Bruguiera/Ceriops) (S/BC) (ranging from 0 to 22.9) and Sonneratia:Rhizophora (S/R) (ranging from 0 to 2.29), vegetation and altitude to interpret mangrove dynamics and refine the vertical errors associated with relative sea level change. The variations in mangrove taxa ratios in the sediment cores obtained from each site shows mangrove development at different periods during the Holocene from around 7900 cal yr BP. An early to mid-Holocene RSL rise occurred from ∼7900 to ∼4600 cal yr BP that may have reached a higher level than present. A lower RSL occurred after 4600 cal yr BP, resulting in mangroves retreating seaward at all three study locations, before a low magnitude RSL rise occurred between 4400 and 2000 cal yr BP. Another RSL rise is recorded at ∼500 cal yr BP before falling to a level lower than present at ∼100 cal yr BP. There is evidence of a recent RSL rise recorded from mangrove ratios during the last century. In addition, the sedimentation rates among sites are relatively different due to different altitudinal ranges with freshwater input, sediment supply and progradation having significantly more effect in the Rufiji Delta (2.1–10.9 mm cal yr−1) than at the Zanzibar sites (0.3–6.6 mm cal yr−1).

Long-Term Rainfall Trends over the Tanzania Coast

Spatial and temporal rainfall trends over the Tanzanian coast are analysed and trends for over 50 years are investigated. This type of study is crucial at this time because the area under study is now one of the world’s economic hotspots, as major gas fields have been discovered and the area also has high potential for oil field discoveries. Methods applied in this study include the Mann-Kendall test for rainfall data to detect the long-term trends, while Sen’s slope estimator test was used for finding the magnitude of change over time. The results exhibited rainfall trend patterns with substantial variations between the stations. The Z value of the Mann-Kendall test showed various months with negative trend at a significance level ≥95%. The few months that showed a positive trend were not statistically significant. Generally, rainfall trends varied in different months for different stations. However, the most outstanding observation on individual months is July, which showed a highly statistically significant (99.9%) reduction in rainfall for the whole coastal area, including the regions of Mtwara, Dar es Salaam and Tanga. The last part of this paper describes the relationship between July rainfall and the horizontal winds from the National Centre for Environmental Prediction/National Centre for Atmospheric Research (NCEP/NCAR) re-analysis. It is observed that the strength of the anticyclonic flow over the southwest Indian Ocean, which is associated with the westward fluxes of moisture, is responsible for rainfall over the whole coastal area of Tanzania during July.

Bioaccumulation and public health implications of trace metals in edible tissues of the crustaceans Scylla serrata and Penaeus monodon from the Tanzanian coast.

The coastal population in East Africa is growing rapidly but sewage treatment and recycling facilities in major cities and towns are poorly developed. Since estuarine mangroves are the main hotspots for pollutants, there is a potential for contaminants to accumulate in edible fauna and threaten public health. This study analysed trace metals in muscle tissues of the giant mud crabs (Scylla serrata) and the giant tiger prawns (Penaeus monodon) from the Tanzanian coast, in order to determine the extent of bioaccumulation and public health risks. A total of 180 samples of muscle tissues of S. serrata and 80 of P. monodon were collected from nine sites along the coast. Both species showed high levels of trace metals in the wet season and significant bioaccumulation of As, Cu and Zn. Due to their burrowing and feeding habits, mud crabs were more contaminated compared to tiger prawns sampled from the same sites. Apart from that, the measured levels of Cd, Cr and Pb did not exceed maximum limits for human consumption. Based on the current trend of fish consumption in Tanzania (7.7kg/person/year), the measured elements (As, Cd, Co, Cu, Mn, Pb and Zn) are not likely to present health risks to shellfish consumers. Nevertheless, potential risks of As and Cu cannot be ruled out if the average per capita consumption is exceeded. This calls for strengthened waste management systems and pollution control measures.

Among-site variability in the stochastic dynamics of East African coral reefs.

Coral reefs are dynamic systems whose composition is highly influenced by unpredictable biotic and abiotic factors. Understanding the spatial scale at which long-term predictions of reef composition can be made will be crucial for guiding conservation efforts. Using a 22-year time series of benthic composition data from 20 reefs on the Kenyan and Tanzanian coast, we developed Bayesian vector autoregressive state-space models for reef dynamics, incorporating among-site variability, and quantified their long-term behaviour. We estimated that if there were no among-site variability, the total long-term variability would be approximately one-third of its current value. Thus, our results showed that among-site variability contributes more to long-term variability in reef composition than does temporal variability. Individual sites were more predictable than previously thought, and predictions based on current snapshots are informative about long-term properties. Our approach allowed us to identify a subset of possible climate refugia sites with high conservation value, where the long-term probability of coral cover ≤0.1 (as a proportion of benthic cover of hard substrate) was very low. Analytical results show that this probability is most strongly influenced by among-site variability and by interactions among benthic components within sites. These findings suggest that conservation initiatives might be successful at the site scale as well as the regional scale.

Genetic diversity of the giant tiger prawn Penaeus monodon in relation to trace metal pollution at the Tanzanian coast

The genetic diversity of giant tiger prawns in relation to trace metals (TMs) pollution was analysed using 159 individuals from eight sites at the Tanzanian coast. The seven microsatellites analysed showed high degree of polymorphism (4–44 alleles). The measured genetic diversity (Ho=0.592±0.047) was comparable to that of populations in the Western Indian Ocean. Apart from that, correlation analysis revealed significant negative associations between genetic diversity and TMs pollution (p<0.05), supporting the genetic erosion hypothesis. Limited gene flow was indicated by a significant genetic differentiation (FST=0.059, p<0.05). The Mantel test rejected the isolation-by-distance hypothesis, but revealed that gene flow along the Tanzanian coast is limited by TMs pollution. This suggests that TMs affect larvae settlement and it may account for the measured deficiency of heterozygosity. This calls for strengthened pollution control measures in order to conserve this commercially important species.

A history of conservation of built heritage sites of the Swahili Coast in Tanzania

ABSTRACTThe interaction between the Swahili Coast of the present-day Tanzanian coast and other parts of the Indian Ocean world dates back to the first millennium AD. This commercial communication resulted in the rise of several coastal city-states (stonebuilt towns), some of which date back to the tenth century. Unfortunately, some of these states started to collapse during the second half of the second millennium and the majority of them is in a ruinous state. These material remains, which according to the Tanzania’s Antiquities Act of 1964 deserve legal protection, have not been studied comprehensively mainly to establish their conservation history. The current article addresses this problem, and by analysing documents, it establishes the conservation history of monuments and historic buildings of the Swahili Coast in Tanzania. Research results indicate that some built heritage sites started decaying during the fourteenth century AD. Because of recognising the importance of these built heritage sites, communities of the region embarked on strategies to care these built heritage sites. This observation contradicts the European conventional wisdom maintaining that, in Africa, conservation of built heritage sites such as monuments and historic buildings began in the nineteenth century and was propagated by European colonialists.

Trace metals in the giant tiger prawn Penaeus monodon and mangrove sediments of the Tanzania coast: Is there a risk to marine fauna and public health?

Mangroves ecosystems support livelihood and economic activities of coastal communities in the tropics and subtropics. Previous reports have documented the inefficiency of waste treatment facilities in Tanzania to contain trace metals. Therefore, the rapidly expanding coastal population and industrial sector is likely to threaten mangrove ecosystems with metal pollution. This study analysed trace metals in 60 sediment samples and 160 giant tiger prawns from the Tanzanian coast in order to document the distribution of trace metals and to establish if measured levels present a threat to mangrove fauna and are of public health importance. High levels of Cr, Co, Cu, Fe, Mn, Ni, and V was observed in mangroves of river Pangani, Wami, and Rufiji. Multivariate analysis showed that they originate mainly from weathering and erosion in the river catchments. Extreme enrichment of Cd was observed in a mangrove affected by municipal sewage. The distribution of Hg, Pb, and Zn was related with urbanisation and industrial activities along the coast. The metal pollution index was high at Pangani, Saadani, and Rufiji, suggesting that these estuarine mangroves are also affected by human activities in the catchment. Moderate to considerable ecological risks were observed in all sampled mangroves, except for Kilwa Masoko. It was revealed that As, Cd, and Hg present moderate risks to fauna. High levels of Cu, Fe and Zn were observed in prawns but the level of the non-essential Cd, Hg, and Pb did not exceed the maximum allowed levels for human consumption. However, based on the trends of fish consumption in the country, weekly intake of Hg is likely to exceed provisional tolerable weekly intake level, especially in fishing communities. This calls for measures to control Hg emissions and to strengthen sewage and waste treatment in coastal cities and urban centres in the basin of major rivers.

Annual cycle of the upper-ocean circulation and properties in the tropical western Indian Ocean

A regional ocean model was used to simulate the annual cycle of the upper-ocean dynamics and its influence on ocean properties in the tropical western Indian Ocean. Surface winds and heat fluxes from the National Centers for Environmental Prediction (NCEP) reanalysis forced the model (Model_NCEP) with initial and lateral boundary conditions derived from the Simple Ocean Data Assimilation (SODA). The model findings were in good agreement with previous research, satellite and observational data as well as another model configuration forced by Comprehensive Ocean and Atmosphere Data Sets (COADS). The initial and lateral boundary conditions for Model_COADS were extracted from World Ocean Atlas 2001. Anticyclonic wind stress curl occurred to the north of Madagascar, and extended towards the Tanzanian coast throughout the year, leading to Ekman convergence and downwelling in that region. The lowest sea-surface height values during the year occurred between 5° and 12° S with an elongated and contracted shape. The East African Coastal Current (EACC) was in phase with the westward North-East Madagascar Current (NEMC) throughout the year with volume transports peaking in June through July in the model forced by NCEP reanalysis. The variability of the volume transport, ocean currents, temperature and salinity to the north of Madagascar on the path of the NEMC mirrored those in the middle Tanzanian shelf on the path of the EACC throughout the year. The NEMC seemed to influence the water masses on the Tanzanian shelf, with cooler and lower-salinity water in the South-West Monsoon, and warmer and saltier water during the North-East Monsoon.

Influence of local environmental conditions and bleaching histories on the diversity and distribution of Symbiodinium in reef-building corals in Tanzania

Pollution, turbidity and coral bleaching history, as well as coral diversity, vary along the Tanzanian coastline. Prior to this study, it was not known whether exposure to such environmental variation might have influenced the diversity and distribution of Symbiodinium along this coastline. Such information can provide insight into whether Tanzanian reef-building corals develop adaptation to current trends of climate change. Here, 10 reef-building coral samples were collected from different reefs along the Tanzanian coast with different micro-environments and bleaching histories. The ITS-2 region of ribosomal DNA was employed in the characterisation of Symbiodinium harboured by reef-building corals. DGGE fingerprints and DNA sequences showed that most coral species host a single Symbiodinium type, which is maintained throughout the coast regardless of local environmental differences. We present polymorphic symbioses in Acropora spp., Millepora sp. and Galaxea fascicularis in mainly turbid and warm environments as a sign of adaptation to harsh conditions. However, such adaptation may not provide marked resistance to bleaching because Acropora is a bleaching-susceptible genus.

Libanasa kilomeni, a new species of East African Lutosinae (Orthoptera: Anostostomatidae).

A new species of Libanasa, L. kilomeni, is described. In contrast to L. brachyura, an inhabitant of lowland wet to submontane forest along the Tanzanian coast and part of the Eastern Arc Mountains of Tanzania, this new species is found in montane forest in the North Pare Mountains. L. kilomeni n. sp. is restricted to a small forest reserve and due to forest clearing at lower elevations probably driven to its upper ecological border. Therefore this species is considered endangered and should be included in the IUCN red list.

Benthic macroinvertebrate assemblages in mangroves and open intertidal areas on the Dar es Salaam coast, Tanzania

The assemblages of benthic macroinvertebrates in mangroves and open intertidal areas of the Dar es Salaam coast, Tanzania, was investigated in 2013–2014, revealing 56 species. Higher density, species richness and diversity were recorded in open intertidal areas, compared to nearby mangrove forests. Non-metric multidimensional scaling indicated differences in assemblages between mangrove and open intertidal samples. These differences were confirmed by analysis of similarity. SIMPER identified an average dissimilarity of 97.24% between mangroves and open intertidal samples, most of which were due to the malacostracan Uca annulipes and the gastropod Cerithidea decollata. PRIMER RELATE indicated significant correlation between macroinvertebrate assemblages and the measured physico-chemical parameters salinity, pH, redox potential and sediment particle size, whereas BIOENV and the Monte Carlo permutation test indicated that redox potential, sediment particle size and pH contributed significantly to variation in species composition. Mangroves were dominated by the gastropod C. decollata, and by the malacostracans Neosarmatium africanum and U. annulipes, and open intertidal areas by the bivalves Dosinia hepatica and Eumarcia paupercula. Due to the rich biodiversity in open intertidal ecosystems, it is recommended that conservation efforts along the Tanzanian coast should focus here.

Conservation, community archaeology, and archaeological mediation at Songo Mnara, Tanzania

During archaeological fieldwork at Songo Mnara, a UNESCO World Heritage Site on the southern Tanzanian coast, a storm caused the collapse of a graveyard’s retaining wall. The process initiated by the rebuilding of that wall serves as a case study in addressing the dialogue among researchers, community members, and national and international organizations concerning heritage. During the process of rebuilding the wall, the Village Ruins Committee was called up by the Songo Mnara villagers as a community voice to speak with external stakeholders and to access perceived opportunities to work with UNESCO for financial reward. The committee led the rescue operation at the graveyard, yet was not always recognized as part of the process of conserving the site. In describing the tensions among the hierarchy of stakeholders at Songo Mnara, we explore the benefits and contradictions of international involvement with marginalized communities who might have multiple competing interests. Our study also speaks to good archaeological practice and the ways that we must seek to do community archaeology through recognizing the efforts of local groups who need to forge their own paths to collaboration. The case of Songo Mnara is an interesting example of how international heritage agendas, local historical memory and archaeological research can intersect to strengthen community ties to, and investment in, the monuments of the past.

The complexity of public space at the Swahili town of Songo Mnara, Tanzania

Public spaces have been long recognized as integral parts of urban settings, often granted importance by the public ceremonies and spectacles that they hosted. Interpretations of such public arenas often focus on elites that use them to construct and legitimize power and authority; city residents are thought to either accept these political machinations, or reject them and the space itself. Alternately, studies of public space that emphasize more practical uses, such as for production or other domestic activities tend to focus on those spaces directly associated with houses, emphasizing the everyday life of city residents. This paper works to set aside this dichotomy by exploring the multi-faceted open spaces at Songo Mnara, a medieval Swahili town on the southern Tanzanian coast. Songo Mnara is particularly well-suited to a study of Swahili public space because of its short occupation and clear town plan understood through standing architecture; it is likely the best example of how the southern Swahili understood a planned town should be organized in the fifteenth century AD. Archaeological research directed at the site’s open spaces has revealed a variety of public spaces which include a mix of deliberately-maintained areas reflecting some element of control and planning, and other less formal public spaces that seem to have been organized and maintained by non-elite residents of the town. This essay reviews literature on the archaeology of open and public space and explores how the case of Songo Mnara contributes to it, by walking the reader through what has been learned about the complex and variable public spaces of the town. The public spaces of Songo Mnara serve to broaden previous dichotomous approaches to urban open space.

Chalinochromis cyanophleps, a new species of cichlid fish (Teleostei: Cichlidae) from Lake Tanganyika.

Chalinochromis cyanophleps is described from nine specimens, the largest 129 mm SL, from Namansi. It differs from other species of Chalinochromis in plain trunk colouration, absence of black stripes on the head, relatively narrow lips, presence of tricuspid jaw teeth, and presence of five rather than four dentary lateralis foramina. The blue iridescent stripe below the eye is shared with other lamprologin cichlids, but is broader and more conspicuous in C. cyanophleps. Chalinochromis cyanophleps occurs at depths between 6 and 45 m in rocky habitats along the Tanzanian coast of Lake Tanganyika, from Mvuna Island south to Kalala Island, a stretch of about 90 km. Field observations were made of specimens up to 18 cm total length. The COI DNA barcode sequence differs by 1.8% from that of C. popelini.

English

A numerical modeling study was carried out using the Regional Ocean Modeling System (ROMS) for the Tanzanian coast to investigate the seasonal dynamics of water circulation, temperature and salinity. The model results indicated the presence of an eddy on the surface that develops during the Northeast (NE) monsoon and which has not been documented previously. The study also revealed that, the core of the East African Coastal Current (EACC) passes adjacent to the coast, just off the three major islands of Pemba, Zanzibar, and Mafia. There are localized patches of strong currents parallel and adjacent to the mainland coast, with magnitudes that are influenced by the coastline configuration, bottom topography and the extent of exposure to the main stream of the EACC. The current speeds along the coast of Tanzania are lowest in February and March, and highest in July, August, and November but generally not exceeding 1 ms-1. Surface salinities generally vary between 34.8 and 35.5, whereas surface temperatures range from a minimum of 25.0&deg;C to a maximum of 30.2&deg;C. The modelled salinity and temperature profiles are similar to those observed from field observations of previous investigations. Key words: Regional Ocean Modeling System (ROMS) model; seasonal variations; water circulation; salinity; water temperature; Tanzanian coast.

A Review of Ceramics from Tanzania, Malawi, and Northern Mozambique, with Implications for Swahili Archaeology

Typological approaches to locally produced ceramics have played an important role in the archaeology of Eastern Africa. This paper engages with that history as it contextualizes the ceramic material recently recovered from the region around the site of Mikindani on the southern Tanzanian coast with known traditions from the Kenyan and Tanzanian coast, Malawi, and Mozambique. That comparison reveals the shifting connections and interregional relationships the inhabitants of the Mikindani region forged over the past two millennia with other communities in the Indian Ocean world and the African interior. Mikindani's ceramics are shown to provide important evidence of the deep connections between the region and the African interior to the southwest during the early second millennium, at the expense of connections with coastal Swahili sites further north. This pattern is unusual for a coastal site during the florescence of Swahili society and the typical expansion of Swahili involvement in the Indian Ocean world at that time. The typological comparison of the Mikindani material and other regional traditions thus allows us to consider the strengths and weaknesses of the typological enterprise, in terms of what information is brought to light and what information is obscured.

The public life of the Swahili stonehouse, 14th–15th centuries AD

Houses are an important subject of archaeological research, normally explored through the households they contain. This has established a deliberately social agenda for the archaeology of houses, yet has had the unintended consequence of creating bounded worlds for study. Although household archaeologies explore the ways that households contributed to broader social and economic realms, it is rare to think through the public role of houses for non-residents and the larger population of the settlement. This paper seeks to explore this more public aspect of houses using the data from archaeology at Songo Mnara, a 14th–15th century Swahili town on the southern Tanzanian coast. This was a time when stone-built domestic architecture was first emerging in this region. The archaeology of the houses provides data for a series of ways that the house was at the heart of the economic and political life of the town, as well as demonstrating a spatial continuity between indoor and outdoor spaces. It is therefore suggested that the domestic and residential functions of the house for a particular household should be balanced with an appreciation of the broader world of the house itself.

Biogeography, ecology, acoustics and chromosomes of East African Eurycorypha Stål species (Orthoptera, Phaneropterinae) with the description of new species

Although Eurycorypha is the most species-rich Phaneropterinae genus in Africa, little is known about the distribution and the ecology of the species. In this study data on distribution, ecology, song and on chromosomes of some East African species are provided. The nymphs of some species are shown, famous for their ant-like appearance and behaviour. The male of E. punctipennis Chopard and three species of Eurycorypha are newly described. These are E. resonans n. sp. and E. combretoides n. sp. occurring in different habitats on Mount Kilimanjaro, and E. conclusa n. sp from forest habitats along the Tanzanian coast. Bioacoustically, the four recorded species are unusually divers, presenting non-resonant and resonant songs. As four Eurycorypha species occur syntopically on geological young Mount Kilimanjaro, the biogeographical pattern and possible speciation mechanisms in the genus Eurycorypha are discussed in context of the climatical history of eastern Africa.

Mangrove dynamics and Holocene sea level change: records from the Tanzanian coast

Mangrove dynamics and Holocene sea level change: records from the Tanzanian coast