Influence of small-scale gold mining and toxic element concentrations in Bonsa river,Ghana: a potential risk to water quality and public health

A preliminary assessment of toxic element pollution caused by artisanal and small-scale gold mining in the Bonsa river of Ghana as well as the influence of TOC and SO₄ ^2? concentration on these traces in the sediment has been determined. With the exception of mercury (Hg), manganese (Mn), and arsenic (As), the concentration of aluminum (Al) in filtered river water exceeded the WHO guideline limit of 0.1 mg L^?1 in drinking water. Analyses of toxic element in sediment using Canadian Sediment Quality Criteria, contamination factor, geoaccumulation index, and enrichment factor indicate that river sediment is severely contaminated with Hg confirming the negative impact of the amalgamation technique in gold beneficiation in Ghana. The level of Hg in the surface water exceeded reported values from some rivers in Africa, Asia, and South America. The ranking order of the mean element concentration in both matrices followed the conservative order of traces found in the Earth crust except copper, which was below the detection limit of 0.01 mg kg^?1. A Pearson correlation matrix of the toxic element and geology of the river bedrock indicates that the Hg contamination is of anthropogenic origin whilst As, Mn, and Al are the result of natural enrichment. The partitioning of elements in the sediment compartments is independent of TOC and SO₄ ^2? concentration. Health-risk assessment based on average daily dose, hazard quotient, and cancer risk indicates that Hg is a health risk to the human population. In conclusion, the study has shown that there is a likely anthropic affection of the river and that this situation has worsened since earlier studies. In order to sustain aquatic life and to prevent future human health hazard, an immediate mercury remediation in the river is recommended.     

Genetic stock structure of white steenbras Lithognathus lithognathus (Cuvier, 1829), an overexploited fishery species in South African waters

White steenbras Lithognathus lithognathus (Teleostei: Sparidae) is an overexploited marine fish species endemic to South Africa. Overexploitation in recreational, subsistence and commercial fisheries has resulted in stock collapse and the need for improved management of the species. Adults are thought to undertake large-scale annual spawning migrations, yet studies of their movement indicate low levels of connectivity among coastal regions. To address this, mitochondrial DNA sequencing and genotyping of microsatellite loci in the nuclear genome were conducted to determine the genetic stock structure and level of gene flow in this species. Genetic diversity was high throughout the species’ core distribution, with no evidence of isolation by way of distance or localised spawning. Low, non-significant pairwise fixation indices (F_ST, R_ST and Jost’s D_est) indicated low genetic differentiation and high levels of gene flow. The observed results, and agreement between mitochondrial and microsatellite DNA, confirm that white steenbras exists as a single genetic stock with high levels of gene flow throughout its distribution.     

Sedimentary evidence of prehistoric distant-source tsunamis in the Hawaiian Islands

Over the past 200 years of written records, the Hawaiian Islands have experienced tens of tsunamis generated by earthquakes in the subduction zones of the Pacific ‘Ring of Fire’ (for example, Alaska–Aleutian, Kuril–Kamchatka, Chile and Japan). Mapping and dating anomalous beds of sand and silt deposited by tsunamis in low-lying areas along Pacific coasts, even those distant from subduction zones, is critical for assessing tsunami hazard throughout the Pacific basin. This study searched for evidence of tsunami inundation using stratigraphic and sedimentological analyses of potential tsunami deposits beneath present and former Hawaiian wetlands, coastal lagoons, and river floodplains. Coastal wetland sites on the islands of Hawai΄i, Maui, O΄ahu and Kaua΄i were selected based on historical tsunami runup, numerical inundation modelling, proximity to sandy source sediments, degree of historical wetland disturbance, and breadth of prior geological and archaeological investigations. Sand beds containing marine calcareous sediment within peaty and/or muddy wetland deposits on the north and north-eastern shores of Kaua΄i, O΄ahu and Hawai΄i were interpreted as tsunami deposits. At some sites, deposits of the 1946 and 1957 Aleutian tsunamis are analogues for deeper, older probable tsunami deposits. Radiocarbon-based age models date sand beds from three sites to ca 700 to 500 cal yr bp , which overlaps ages for tsunami deposits in the eastern Aleutian Islands that record a local subduction zone earthquake. The overlapping modelled ages for tsunami deposits at the study sites support a plausible correlation with an eastern Aleutian earthquake source for a large prehistoric tsunami in the Hawaiian Islands.     

Quantifying the impact of watershed urbanization on a coral reef: Maunalua Bay,Hawaii

Human activities in the watersheds surrounding Maunalua Bay, Oahu, Hawaii, have lead to the degradation of coastal coral reefs affecting populations of marine organisms of ecological, economic and cultural value. Urbanization, stream channelization, breaching of a peninsula, seawalls, and dredging on the east side of the bay have resulted in increased volumes and residence time of polluted runoff waters, eutrophication, trapping of terrigenous sediments, and the formation of a permanent nepheloid layer. The ecosystem collapse on the east side of the bay and the prevailing westward longshore current have resulted in the collapse of the coral and coralline algae population on the west side of the bay. In turn this has lead to a decrease in carbonate sediment production through bio-erosion as well as a disintegration of the dead coral and coralline algae, leading to sediment starvation and increased wave breaking on the coast and thus increased coastal erosion. The field data and resulting coral reef ecohydrology model presented in this paper demonstrate and quantify the importance of biophysical processes leading to coral reef degradation as the result of urbanization. Coral restoration in Maunalua Bay will require an integrated ecosystem approach.     

Modeling the ionosphere wind dynamo: A review

This paper reviews the current status of research concerned with modeling the ionospheric wind dynamo. Simulation models have been reasonably successful in reproducing the types of magnetic perturbations that are produced by the dynamo. Ionospheric electric fields are less well simulated, particularly at night. The primary areas of research needed to improve our ability to simulate realistically the ionospheric wind dynamo are in the modeling of nighttime conditions, hemispherical asymmetries of thermospheric tides, and mutual dynamic coupling among winds, conductivities, electric fields, and electric currents.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

PHYSIOLOGICAL INHIBITORY EFFECT OF OCS IN ARACHIDONIC ACID-RICH PARIETOCHLORIS INCISA （TREBOUXIOPHYCEAE, CHLOROPHYTA）

Parietochloris incisa is an arachidonic acid-rich snow green alga. The main physiological profiles, such as ash free dry weight (AFDW), chlorophyll, carotenoid, protein and total fatty acids (TFA), in this alga exposed to old culture supernatant (OCS) at the decline phase or its crude ethyl acetate extracts (CEAE) were investigated by using tubular photobioreactors of different diameters. Results showed that both OCS and CEAE had strong inhibitory effect on the above physiological parameters. The longer the culture was exposed to OCS and the more CEAE were added into the algal culture, the more the above physiological properties were inhibited. Arachidonic acid (AA), the dominant component of fatty acids in this alga, was also seriously inhibited with respect to total TFA, AFDW of cell mass, or culture volume, due to a prebable reduction of enzymes activities catalyzing chain elongation from C18:1ω9 to AA. These results incontestably evidenced that some CEAE dissolving substances existing in OCS, like auto-inhibitors, inhibited P. incisa growth through feedback. Hence, any efficient removal of auto-inhibitors from algal culture to decrease their bioactivity could be good for maximal production of desired products like AA.     

Developing Data-Rich Video of Surface Water–Groundwater Interactions for Public Engagement

Communication of hydrologic data to the public can be improved by connecting data to the places they represent. In our example of data communication, we coupled hydrologic data with simultaneously collected video as both a scientific and public engagement tool. This note presents a method for collecting spatially and temporally dense datasets of water-quality and geophysical data on small streams and lakes, and for displaying the data in a user-friendly format using commercially available software. With this method, multiple instruments are mounted on a canoe and a controlled survey float is carried out to collect data. The data stream is georeferenced and logged using an Arduino microcontroller to provide detailed information about spatial variability. We employed these continuous data-collection methods at small streams and lakes across Wisconsin, USA. Comparison of stream-float sensor data to lab reported data, data collected by alternative sensors, and previously collected data in our study areas indicates that the low-cost temperature, electrical conductivity, pH, and dissolved oxygen sensors performed well. GoPro cameras recorded video throughout the duration of data collection. Our established water-quality and geophysical data collection methods are inexpensive, fast, and reliable, which qualify them as excellent tools for fine-scale spatial understanding of stream and lake habitats' health. Data-rich video connects point measurements of water properties to the appearance of the native environment. This method helps improve our understanding of groundwater and surface water interactions in complex hydrogeologic systems, enhance communication amongst stakeholders, and provide context when monitoring and managing sensitive habitats.     

FATTY ACIDS PROFILE IN A HIGH CELL DENSITY CULTURE OF ARACHIDONIC ACID-RICH PARIETOCHLORIS INCISA （TREBOUXIOPHYCEAE, CHLOROPHYTA） EXPOSED TO HIGH PFD

The changes in arachidonic acid (AA) and fatty acids profiles along the growth curve ofParietochloris incisa, a coccoid snow green alga, were studied in a 2.8 cm light-path flat photobiorcactor, exposed to strong photon flux density [PFD, 2400 μEmol/(m²·s)]. Sixteen fatty acids were identified by gas chromatography showing that AA was the dominant fatty acid (33%–41%) followed by linoleic acid (17%–21%). AA content was closely investigated with respect to total fatty acids (TFA), ash free dry weight (AFDW) of cell mass as well as total culture content. These parameters were influenced significantly in a similar manner by culture growth phase, i.e., slightly decreasing in the lag period, gradually increasing in the logarithmic phase, becoming maximal at the early stationary phase, starting to decrease at the late stationary phase, sharply dropping at the decline phase. The increase in AA per culture volume during the logarithmic phase was not only associated with the increase in AFDW but also connected with a corresponding increase in AA/TFA, TFA/AFDW as well as AA/AFDW. The sharp decrease in AA content of the culture during the decline phase was mainly due to the decrease in AA/TFA, TFA/AFDW and AA/AFDW, although AFDW declined only a small extent. Maximal AA concentration, obtained at the early stationary phase, was 900 mg/L culture volume, and the average daily net increase of AA during 9 days logarithmic growth was 1.7 g/(m²·day). Therefore, harvesting prior to the decline phase in a batch culture, or at steady state in continuous culture mode seems best for high AA production. The latter possibility was also further confirmed by continuous culture with 5 gradients of harvesting rate. Contribution No. 4138 from the Institute of Oceanology, Chinese Academy of Sciences. Project 39970575 supported by NSFC and A/2786-2 supported by International Foundation for Sciences (IFS).     

Trapping of fine sediment in a semi-enclosed bay, Palau, Micronesia

Airai Bay, Palau, is a small (3 km²), semi-enclosed, mangrove-fringed, meso-tidal, coral lagoon on the southeast coast of Palau. It drains a small catchment area (26 km²) of highly erodible soils in an area with high annual rainfall (3.7 m). River floods are short-lived and the sediment load is very large, with suspended fine sediment concentration exceeding 1500 mg l⁻¹. The resulting river plume is about 2 m thick. The brackish water residence time is about 7 days; during this period the plume remains a distinct surface feature even after river runoff has ceased. About 98% of the riverine fine sediment settles in Airai Bay, of which about 15–30% is deposited in the mangroves during river floods. This mud remains trapped in Airai Bay because the bay is protected from ocean swells and the tidal currents and locally generated wind waves are too small to resuspend the mud in quantity. The mud is smothering coral reefs, creating a phase shift from coral to fleshy algae dominance, and is even changing habitats by creating mud banks. The persistence of Airai Bay marine resources may not be possible without improved soil erosion control in the river catchment.