Indian Ocean Coast Research Articles

Mapping Of Land Use Changes In Urban Catchments. A Case Of Msimbazi Catchment In Dar Es Salaam, Tanzania

Rapid urbanization activities may put significant pressure on catchments around the globe as they are also associated with the change in land use/land cover. This study used GIS-based techniques to investigate the land use/land cover changes in the Msimbazi river catchment in Dar es Salaam, Tanzania. The Landsat images of the selected study years (1998, 2009, and 2018) were processed in ArcGIS software. The land use classes were grouped into five groups namely; water bodies, forests, developed high intensity, developed medium intensity, and developed low intensity. This study observed significant changes in land use/land cover in the Msimbazi catchment from 1998 to 2018, with an estimated 40.54% decrease in developed low-intensity areas, as well as a 15.95% increase in developed high-intensity areas defined with 80% to 100% impervious cover. The extent of development and impervious surface cover were observed to be increasing towards the downstream approaching the Indian Ocean coast. The results from this study reflect the reality of the catchment where downstream is characterized with more development activities than the upstream of the catchment. The results derived from this study can be useful in the planning and implementation of catchment management practices.

Mapping of Land Use Changes in Urban Catchments. A Case of Msimbazi Catchment in Dar Es Salaam, Tanzania

Rapid urbanization activities may put significant pressure on catchments around the globe as they are also associated with the change in land use/land cover. This study used GIS-based techniques to investigate the land use/land cover changes in the Msimbazi river catchment in Dar es Salaam, Tanzania. The Landsat images of the selected study years (1998, 2009, and 2018) were processed in ArcGIS software. The land use classes were grouped into five groups namely; water bodies, forests, developed high intensity, developed medium intensity, and developed low intensity. This study observed significant changes in land use/land cover in the Msimbazi catchment from 1998 to 2018, with an estimated 40.54% decrease in developed low-intensity areas, as well as a 15.95% increase in developed high-intensity areas defined with 80% to 100% impervious cover. The extent of development and impervious surface cover were observed to be increasing towards the downstream approaching the Indian Ocean coast. The results from this study reflect the reality of the catchment where downstream is characterized with more development activities than the upstream of the catchment. The results derived from this study can be useful in the planning and implementation of catchment management practices.

Trace metal enrichment and sediment quality in coastal-urban rivers along the Indian Ocean coast, Dar es Salaam, Tanzania

Trace metal enrichment and sediment quality in coastal-urban rivers along the Indian Ocean coast, Dar es Salaam, Tanzania

Use of physicochemical parameters and metal concentrations in assessing anthropogenic influences on coastal rivers in Dar es Salaam, Tanzania

Spatio-temporal variations in water quality of three rivers along the Indian Ocean coast in Dar es Salaam, Tanzania, were investigated based on physicochemical parameters and metal concentrations. A compliance analysis was performed based on the Tanzania Bureau of Standards (TBS) and World Health Organization (WHO) limits to examine the suitability of water for domestic use. The dataset was subjected to statistical analysis to determine differences and similarities amongst the rivers. Levels of pH (6.83-11.41), total dissolved solids (203–34,333 mg/L), electrical conductivity (9,408-68,014 μS/cm), turbidity (10.0-45.0 NTU), chloride (108-14,248 mg/L), sulphate (35-766 mg/L) and ammonium (40-5,468 μg/L) complied with neither TBS nor WHO limits. Dissolved oxygen (1.4-6.6 mg/L), chemical oxygen demand (91-1,863 mg/L), total suspended solids (11.9-50.7 mg/L), alkalinity (200-2,658 mg/L), total hardness (362-12,1312 mg/L), salinity (0.19-29.35 ppt) and phosphate (<method detection limit-3.01 μg/L) indicated polluted water in parts of the rivers. Pb (0.7-24.0 μg/L) exceeded both the TBS and WHO limits, whereas Cr, Cu, Fe, Zn and Cd were below limits. Water quality was poorer during the wet season. The results indicate that water from the rivers is unsafe for human consumption and the poor water quality probably also affects the ecology of the rivers. Strategic measures to protect the rivers from further contamination are suggested.

Coastal adaptations on the eastern seaboard of South Africa during the Pleistocene and Holocene? Current evidence and future perspectives from archaeology and marine geology

The use of marine resources and the settlement of coastal settlements may have influenced the bio-cultural evolution and dispersal of PleistoceneHomo sapiensin Africa. In order to test such scenarios, however, we require evidence for these behaviours deriving from an expanded spatio-temporal archaeological record. The Stone Age of South Africa documents the richest and longest record of coastal adaptations. In contrast to abundant evidence of coastal sites on the western and southern seaboard, the eastern Indian Ocean coast has not played a role in recent discussions. Considering the important and well-known Middle and Later Stone Age (MSA/LSA) record from inland sites of KwaZulu-Natal (KZN), this region may be an underappreciated area for further study. Here we provide a systematic overview of marine resource use and the settlement of coastal landscapes during the Late Pleistocene and Holocene in KZN. For the first time, we contextualize these archaeological findings with a review and new data on the changing marine and coastal geomorphology in the context of GIS modelling and offshore marine geophysical investigations. Our review finds evidence for long-term dietary and non-dietary use of marine resources during the MSA and LSA from a few stratified sites, with many more surface occurrences particularly for the MSA along the modern KZN coastline indicating human habitation. Comparisons to other areas of South Africa, GIS modelling and geological considerations suggest that current data on the eastern seaboard are not reflective of the original extent and nature of the consumption of marine foods and settlement of coastal landscapes. By contextualizing the biased and patchy MSA and LSA record with results on the dynamic marine and coastal geomorphology of KZN, we develop productive lines of future studies to assess open questions on potential coastal adaptations in this region. These research strategies include the identification of areas with high potential for finding new sites within a 10 km transect along the current coastline as well as dedicated off-shore projects including underwater archaeology aided by new marine geological work in the southwest Indian Ocean.

Whole-genome sequencing analysis of wild house mice (Mus musculus) captured in Madagascar.

In Madagascar, the house mouse (Mus musculus) is widely believed to have colonized with human activities and is now one of the most abundant rodents on the island. However, its genetic background at the genomic level remains unclear, and clarifying this would help us to infer the timing of introduction and route of migration. In this study, we determined the whole-genome sequences of five Madagascar house mice captured from an inland location in Madagascar. We examined the genetic background of samples by analyzing the mitochondrial and autosomal genomes. We confirmed that the mitochondrial genome lineages of collected samples formed a single clade placed at one of the most basal positions in the Mus musculus species. Autosomal genomic sequences revealed that these samples are most closely related to the subspecies M. m. castaneus (CAS), but also contain a genetic component of the subspecies M. m. domesticus (DOM). The signature of a strong population bottleneck 1,000-3,000 years ago was observed in both mitochondrial and autosomal genomic data. In a comparison with global samples of M. musculus, the Madagascar samples showed strong genetic affinity to many CAS samples across a wide range of Indian Ocean coastal and insular regions, with divergence time estimated as around 4,000 years ago. These findings support the proposition that the ancestors of these animals started to colonize the island with human agricultural activity and experienced a complex history during their establishment.

Aquatic biodiversity in a pond on the airport landside areas through environmental DNA metabarcoding: Implementation for Aviation Security Management

Abstract. Priyono DS, Reza A, Eprilurahman R, Yudha DS, Mufti D, Fauzy NH, Triyono RB, Adhi PK. 2022. Aquatic biodiversity in a pond on the airport landside areas through environmental DNA metabarcoding: Implementation for Aviation Security Management. Biodiversitas 23: 3639-3646. Environmental DNA (eDNA) has become a widely used tool for aquatic biodiversity monitoring, as well as for formulating effective landscape management strategies. Yogyakarta International Airport (YIA), Indonesia, has a green belt landscape located on the Indian Ocean coast. YIA's landscape biodiversity analysis is still unexplored. Herein, we first used high throughput sequencing DNA metabarcoding to identify and investigate aquatic biodiversity in a pond on the airport landside areas. The metabarcoding eDNA sequencing analysis yielded 224,737 raw reads from the metagenomics utilizing Illumina MiSeq sequencing. We identified 588 eukaryote species from 205 families and 300 genera. Actinopteri is the most dominant class with a diversity of 160 taxa, followed by Mammalia (88), Amphibia (60), and Chlorophyceae (25). At the order level, Anura has the highest order diversity (50), followed by Rodentia (31), Chiroptera (17), Eulipotyphla (16), Squamata (15), and Cypriniformes (14). We found that Plasmodium was the genus with the highest relative abundance in this pond (18,030 reads). Furthermore, the large variety of fish and other taxa in this pond may attract waterbirds, increasing the risk of bird strike. The abundance of Plasmodium sp. in this airport area is an important issue, especially regarding airport malaria risk. Integration of biodiversity monitoring using eDNA with aviation security management provides valuable information for the airport's wildlife hazard management plan. To prevent the recurrence of bird strikes and prevent airport malaria, aviation security strategies utilizing habitat management approaches are recommended.

Wing-moult and seasonal occurrence of sunbirds (Nectariniidae) captured at four sites in the Eastern Cape, South Africa

Ringing activity in the Eastern Cape province, South Africa, spanned 30 years, with three sites active concurrently over a 14-year period, and three sites over a 6-year period. In total, in the course of 714 ringing days, in all months, we handled 1 207 Amethyst Sunbirds, 708 Southern Double-collared Sunbirds, 707 Greater Double-collared Sunbirds, 381 Grey Sunbirds, 121 Malachite Sunbirds and 140 Collared Sunbirds. Although individuals of all six species were recaptured more than five years after ringing, and despite evidence of the seasonal passage of sunbirds at two sites near the Indian Ocean coast, no birds were recaptured away from the original ringing site. The extent of seasonal movement by these species remains unclear. All species have a complete post-breeding moult, with a period of eclipse plumage in males of the Malachite Sunbird and Southern Double-collared Sunbird. Primary wing-moult in adult Greater and Southern Double-collared Sunbirds extends over three months beginning in December. Inland populations of adult Amethyst Sunbirds and Malachite Sunbirds start primary moult in April. Moult apparently proceeds more rapidly in Malachite Sunbirds (70 days to completion) than in Amethyst Sunbirds (125 days), but the Malachite Sunbird is the only species that frequently displays interrupted/suspended moult in this region. Adult Amethyst Sunbirds in the coastal population evidently start moulting earlier, in late February, with a similar duration to completion as inland birds. Juvenile Amethyst Sunbirds start to moult some two months later than adults in each region and they may complete moult more quickly. Collared Sunbirds appear to have the most protracted moult, extending over five months from November, but estimates of moult parameters for this species and the Grey Sunbird (three months from December) are based on small samples.

Hunter-gatherer technological organization and responses to Holocene climate change in coastal, lakeshore, and grassland ecologies of eastern Africa

The Holocene of eastern Africa saw extreme climatic fluctuations between hyper-humid and arid conditions, which manifested differently across the region's lake basins, coastal ecotones, and terrestrial biomes. Changes to resource availability, distribution, and predictability presented different constraints and opportunities to diverse hunter-gatherer communities. Major ongoing questions concern how humans reconfigured economic, social, and technological strategies in different regional settings. The role of more stable coastal environments in these processes remains especially under-studied. Here, we examine and compare relationships between environmental change and the organization of stone tool technology at the site of Panga ya Saidi Cave, eastern Kenya, in strata dating from c. 15-0.2 ka. Located near the Indian Ocean coast, this dataset provides the first insights into Holocene human-environmental relationships in a coastal forest zone of eastern Africa. Integrating the new Panga ya Saidi environmental and archaeological records with other high-resolution records from nearby terrestrial and lacustrine zones, we take a comparative approach to address how climatic fluctuations shaped trajectories of hunter-gatherer adaptations through the Holocene. We argue that lithic technologies deployed within lake basins and coastal zones reflect more stable land-use strategies with less residential mobility compared to those associated with terrestrial foraging. All regions exhibit technological reconfigurations with the arrival of pastoralism, except for the coastal forest which appear largely consistent across the study period. Results inform ongoing debates into the resilience of recent eastern African hunter-gatherers and food-producers and provide an analogical framework for examining human-environmental dynamics deeper in time.

Development of fragility curve due to the effect of tsunami force on existing building in Banda Aceh city

Aceh is located on the Indian Ocean Coast which is very prone to Tsunamis, this is due to frequent large earthquakes due to Megatrust faults, such as those that occurred during the earthquake on December 26, 2004. Based on the 2012 Aceh earthquake, the Acehnese prefer horizontal evacuation to vertical evacuation [1]. In this case, many people in Banda Aceh do not believe in the strength of TVE buildings (distrust building). From this research, it it is possible for the Acehnese will do the same thing in the future when the tsunami occurs. Horizontal evacuation puts them at risk of traffic accidents so that they cannot reach a safe area in a short time, whereas through vertical evacuation they can reach the TVE of a building in a short time due to its proximity to settlements. When the earthquake and tsunami occured Banda Aceh in 2004, many buildings were destroyed due to the earthquake load and also the Tsunami load. For this problem, a vulnerability analysis of buildings that can be used as TVE buildings can be carried out. If an earthquake magnitude more than 7.0 Mw can cause a tsunami, the TVE building should be counted on the structural strength caused by the Tsunami waves. In this research, a hydrodynamic analysis will be carried out due to air pressure and collision which is a function of velocity and depth of flow and also the influence of drag and drift variables on the building.

Does anthropogenic fragmentation selectively filter avian phylogenetic diversity in a critically endangered forest system?

SummaryDocumenting phylogenetic diversity for conservation practice allows elucidation of ecosystem functioning and processes by highlighting the commonality and divergence of species’ functional traits within their evolutionary context. Conserving distinct evolutionary histories has intrinsic value, and the conservation of phylogenetically diverse communities is more likely to preserve distinct or relic evolutionary lineages. We explored the potential for anthropogenic forest fragmentation to act as a selective filter of avian phylogenetic diversity within the community of forest-dependent birds of the critically endangered Indian Ocean Coastal Belt Forest (IOCBF), South Africa. We conducted avian point count surveys during the austral breeding season, and calculated fragmentation metrics of forest structural complexity, patch size and isolation. We constructed a maximum likelihood phylogeny using the combined analysis of two mitochondrial genes and three nuclear markers and measured the influence of the fragmentation metrics on six measures of phylogenetic diversity. Our results indicated that the avian community was variously affected by anthropogenic forest fragmentation, with the different metrics of phylogenetic diversity responding with no definitive overall pattern. However, forest structural complexity emerged as an important metric explaining phylogenetic structuring. While the avian community’s phylogenetic diversity displayed resilience to anthropogenic fragmentation, previous research showed a reduction in functional diversity along the fragmentation gradient. Therefore, we recommend studies that especially aim to guide conservation management, incorporate both phylogenetic and functional diversity measures to sufficiently interrogate communities’ resilience to the threats under investigation.

South Africa, Western Cape Province, Indian Ocean Coast

South Africa, Western Cape Province, Indian Ocean Coast

Bayhead delta evolution in the context of late Quaternary and Holocene sea-level change, Richards Bay, South Africa.

Richards Bay is part of a back-barrier lagoon fronted by high coastal dunes on the NE, Indian Ocean coast of South Africa. In the early 1970s, a berm was constructed, dividing the original Mhlathuze Estuary into two separate systems; the Richards Bay Harbour and the new Mhlathuze Estuary. This study investigates the stratigraphic evolution of the incised valley system and bayhead delta in the Richards Bay Harbour segment. Seven seismic units (Units 1–7) were imaged. A single regionally developed sequence boundary (SB) along with two tidal ravinement surfaces (tRS1 and tRS2) were identified. Surface SB is associated with the LGM lowstand which developed when sea levels were ~ 130 m below present, until ~18,000 year BP. Cretaceous age siltstones (Unit 1) form the basement. Transgressive material overlying SB (Unit 2) reflects the filling of an incised valley located in the middle segment of a wave-dominated back-barrier system. It is overlain by a bayhead delta (Unit 3), the geometry and seismic signature of which indicate alternating periods of aggradation/progradation and backstepping. The behaviour is attributed to episodic jumps in sea-level, and is tentatively (on the basis of elevations in relation to the regional sea-level curve) linked to periods of rapidly rising sea-level (8.2 ka event and Meltwater Pulse (MWP)-1d). These intervals of rapidly rising sea-level, combined with relatively low gradient settings facilitated backstepping of the delta. Fills (Unit 4) occur within minor incisions along the delta top. These are interpreted as distributary channels that fed sediment to the seaward edge of the bayhead delta system. Elongated mounds on the seafloor (Unit 5) are interpreted as spoil from contemporary port dredging. Slump deposits (Unit 6) along the delta front are attributed to a combination of oversteepening of the delta by dredging, as well as deposition of modern sediments brought into the system by tidal currents. The system is capped by fine-grained, tidally redistributed and deposited sediments (Unit 7) which were possibly sourced from older organic material of an indeterminate source. This site is especially sensitive to episodic rates of sea-level change due to the relatively small Glacial Isostatic Adjustments (GIA) during the postglacial transgression and the flat antecedent gradients of both the subaerial unconformity and the overlying tidal ravinement.

Forest biomes of Southern Africa

ABSTRACT The forests of South Africa and the neighbouring countries, including Lesotho, eSwatini, Namibia, Botswana, Zimbabwe, and Mozambique (south of the Zambezi River), were mapped and classified according to the global system of biomes. The new four-tier hierarchical biome system suggested in this paper includes zonobiome, global biome, continental biome (all recognised earlier), and regional biome – a novel biome category. The existing spatial coverages of the forests were revised and considerably improved, both in terms of forest-patch coverage and mapping precision. Southern Africa is home to three zonal forest types, namely Subtropical Forests (Zonobiome I), Tropical Dry Forest (TDF; Zonobiome II) and Afrotemperate Forests (Zonobiome X). These three biomes are characterised by unique bioclimatic envelopes. Five, two, and eight regional biomes, respectively, have been recognised within these zonal biomes. Recognition of the Zonobiome I and the global biome Tropical Dry Forests in southern Africa is novel and expands our knowledge of the biome structure of African biotic communities. The system of the azonal regional biomes is also new and comprehensively covers the variability of the azonal helobiomes (riparian woodlands and swamp forests), mangroves, and azonal coastal forests. In total, 11 azonal regional biomes have been recognised in the study area. The forest biomes in southern Africa were captured in our electronic map in the form of more than 60 000 polygons, covering 42 416 km2 (1.27% of the study area). No less than 83% of these forests occur in the territory of southern Mozambique. Abbreviations: for the abbreviation of the biome units, see Table 1; CE: centre of endemism; IOCB: Indian Ocean Coastal Belt; MBSA: the area of the Map of Biomes of Southern Africa; VegMap2006 and VegMap2018: Vegetation Map of South Africa, Lesotho and Swaziland (as released in respective years); for the meaning of the codes of the biome units see Table 1, and for the meaning of the abbreviations of climatic characteristics see Appendix S1

LOCAL MARINE RESERVOIR AGE (ΔR) RECONSTRUCTED BASED ON THE TSUNAMI DEPOSIT FROM PANGANI BAY (TANZANIA)

ABSTRACTQuantifying the local marine reservoir age (ΔR) and its change over time is critical for precise radiocarbon calibration of marine samples and for the study of the ocean carbon cycle. ΔR values are scarce for the African coast facing the Indian Ocean, and the few values available were obtained from pre-bomb shells collected during the 19th century. Here, the ΔR value for calibrated year 1110 ± 25 (1σ) CE was reconstructed from radiocarbon dating and Bayesian analysis of marine and terrestrial materials coexisting in a tsunami deposit discovered in Pangani Bay (Tanzania, western Indian Ocean coast). The reconstructed ΔR of –8 ± 40 (1σ, n = 3) is similar to pre-bomb regional estimates and provides new information to investigate regional ΔR change over time. The Bayesian analysis of the dated samples revises the age of the tsunami event found in Pangani Bay to 1064–1157 cal CE (95.4% confidence level) or 1110 ± 25 (1σ) cal CE, about one century younger compared to the previous estimate. Our results indicate that the new ΔR value and the proposed calibration approach can be used to refine existing chronologies in the region, with implications for paleo-environmental reconstructions and archaeological studies of Early Swahili societies.

Biogeographical patterns of grasses (Poaceae) indigenous to South Africa, Lesotho and Eswatini

The ecological and economical importance of African grasses in sustaining animal production prompted studies to quantify the wealth of grass genetic resources indigenous to southern Africa. Plant collection and occurrence data were extracted from two southern African datasets, BODATSA and PHYTOBAS, and analysed to establish biogeographical patterns in the grass flora indigenous to South Africa, Lesotho and Eswatini. A total of 1 648 quarter degree grid cells, representing 674 grass species, were used in an agglomerative hierarchical clustering to determine biogeographical units being referred to as grasschoria. Six distinct groups formed, mainly following existing biome vegetation units, termed the Grassland, Indian Ocean Coastal Belt, Fynbos, Savanna, Central Arid Region and Succulent Karoo grasschoria. The description focuses on associated phytochoria, floristic links, key species, climate and soil properties. The main gradient distinguishing grasschoria was a rainfall-temperature gradient. The collection, conservation and breeding of pasture grass species adapted to especially arid and semi-arid environments, could be managed more efficiently by using these results, but also calling on the need to describe and label infraspecific genetic variants, including ecotypes.

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, EDXRF

Forest canopy gaps offer a window into the future:The case of subtropical coastal forests within an urban matrix in South Africa

Aim of the study: Alien and indigenous species emergence patterns within canopy gaps in urban subtropical forests are poorly understood. This study compared canopy gap floristics in relation to abiotic and physical characteristics across three subtropical urban forests differing in disturbance history.Area of study: Three Northern Coastal Forests of varying disturbance histories located in coastal subtropical urban KwaZulu-Natal (KZN), South Africa (SA).Materials and methods: Closed canopy (n = 15 quadrats per forest ) and four gaps (n = 12 quadrats per forest) from three size classes (‘small’ < 25 m2, ‘medium’ 25 - 45 m2; ‘large’ > 45 m2) were surveyed for the primary least disturbed (PLD), primary highly disturbed (PHD) and transitional highly disturbed (THD) forests using classical vegetation sampling techniques. Soil moisture content and air temperature were measured within each gap.Main results: Cumulatively all forest gaps hosted 198 species. Equivalent number of species (Hill numbers from H = 0 to H = 2) were constantly higher in the PHD forest followed by the PLD forest and lowest in the THD forest. Alien and indigenous plant density were negatively correlated. Species richness was positively correlated with gap size and soil moisture content, and negatively correlated with air temperature.Research highlights: Gap floristic patterns are influenced by size, abiotic factors, disturbance and forest successional status. Floristic, abiotic and physical characteristics of gaps should be monitored within urban forests as these can influence gap infilling in terms of rate, species composition, and alien-indigenous plant interactions across the forest. This can inform management interventions such as species reintroduction and alien clearing.Keywords: conservation; disturbance; gaps; management; Northern Coastal Forest; subtropical; species richness.Abbreviations: SA: South Africa; KZN: KwaZulu-Natal; PLD: Primary Least Disturbed forest; PHD: Primary Highly Disturbed forest; THD: Transitional Highly Disturbed forest; IOCB: Indian Ocean Coastal Belt; New POSA: New Plants of southern Africa website; NEMBA: National Environmental Management: Biodiversity Act.

Reconstruction of metal(loid)s pollution history in sediments of Wami Estuary, Indian Ocean Coast of Tanzania

Results of metal(loid)s pollution history, their enrichment and contamination factors in sediments of Wami River Estuary, Tanzania are presented. Two sediment cores (WE1 and WE2) were retrieved from the Estuary using hand-driven PVC coring tubes. Levels of metal(loid)s in sediment samples were determined using EDXRF spectrometer coupled with X-lab ProTM software. Metal(loid)s enrichment factors (EF) were determined using metal(loid)s baseline values established during this study. Contamination factors were determined by dividing measured metal(lod)s concentrations in the samples by their respective baseline concentrations. Sediment physical chemical parameters were determined in order to establish their relationship with metal(loid)s concentrations. Sediment chronologies were established using the Constant Initial Concentration (CIC) lead-210 sediment-dating model in order to convert sediment depth profile into timescales. The lowest concentrations of As in sediments was measured in sediments deposited during 1960s, followed by increase reaching the highest concentrations in sediments deposited between ca. 2015 and 2017. Lowest and highest concentrations of Cd were measured in 1960’s and ca. 2000, respectively. Cu and Zn had their maximum concentrations in ca. 1971 and their significant positive correlation (r = 0.94, p = 0.01) suggest common origin of these metals. Average metals enrichment factors in the core were established and are in the order As = Cd = Cu = Pb = Zn = 0.1. This EF value suggests that all metals in sediments of Wami originate from natural sources (EF < 1). Metal(loid)s contamination factors (CF) were low to moderate for As, Cu and Zn; moderate for Pb; and low to considerable for Cd. CIC model revealed that the sediment at the bottom of cores WE1 and WE2 date back about 33 and 55 years, respectively. Sediments of Wami Estuary is characterized by mixing as evidenced in the established chronologies. Therefore, reported radiometric dates should be considered as a preliminary chronological estimate and further research is needed focused on terrestrial records of anthropogenic activities.

Early divergence and differential population histories of the Indo-Pacific humpback dolphin in the Pacific and Indian Oceans.

The currently recognized Indo-Pacific humpback dolphin occurs in estuaries and surrounding shallow waters from the South China Sea to the Asian coast of the Indian Ocean. However, a recent study suggested that the humpback dolphin from the Bay of Bengal may represent a distinct phylogenetic species. In this study, we sequenced 915-bp mtDNA segments from five geographic populations in both Chinese and Thai waters; together with previously published sequences, these data revealed that the ancestral Indo-Pacific humpback dolphin might have split during the transition from the Oligocene to Miocene (23.45 Mya, 95% HPD: 16.65-26.55 Mya), and then dispersed along the Pacific and Indian Ocean coasts of Asia. Genetic differentiation was detected between most of the examined populations, except for only a few pairwise populations in the northern South China Sea. Genetic differentiation/distance between the humpback dolphins from the northern and southern South China Sea met the sub-species threshold value proposed for marine mammals, whereas that between the humpback dolphins in the Pacific and the Indian Ocean was above the species threshold. Bayesian inference of historic gene flow indicated low but constant northward gene flow along the Indian Ocean coast; however, there was a recent abrupt increase in gene flow in the Pacific region, likely due to the shortening coastline at the low stand of sea level. Our results revealed that the current taxonomic classification of Indo-Pacific humpback dolphins may not reflect their phylogeography.