Application of artificial mussels (AMs) under South African marine conditions: A validation study

Over the last three decades there has been a significant decline in the number of marine pollution monitoring-related studies in South Africa. Thus, the current study was conducted to assess the current state of metal contamination within the South African marine environment through the validation of the artificial mussel (AM). Indigenous reference mussels (Perna perna) were deployed alongside the passive device within the South African marine environment for a 6 week exposure period. Analysis of metal uptake (Cd, Cr, Cu, Pb and Zn) was determined by filtration and elution of the AM chelex resins, microwave digestion of the transplanted mussels, and determination of their metal concentrations by ICP-MS and ICP-OES analysis. Uptake patterns between the AM and transplanted mussels showed significant temporal and spatial correlation for the majority of the elements analysed. While the AM provided relevant and complementary information on the dissolved metal concentrations, limitations were also observed.     

Brown mussels (Perna perna) and semi-permeable membrane devices (SPMDs) as indicators of organic pollutants in the South African marine environment

A distinct lack of historical and current data on the status of organic pollutant contaminants within the South African marine environment is evident. This has highlighted the need for more current organic pollutant assessments. Reference mussels and SPMDs were transplanted at five South African harbour sites to assess organic bioaccumulation in brown mussels (Perna perna) and semi-permeable membrane devices (SPMDs). Spatial patterns of PAH and PCB contaminants were determined by GC-MS and GC-ECD after appropriate sample preparation. Significant (p<0.05) spatial differences were observed between the sites. Results indicate no correlations between the passive device and the transplanted mussels; however the SPMDs provided complementary information on the presence of dioxin-like PCBs within the environment not detected by the mussel. The results indicate that information provided by both the mussels and SPMDs allow for a more in depth scrutiny of environmental conditions as a result of anthropogenic influence.     

Bioconcentration of triclosan and methyl-triclosan in marine mussels (Mytilus galloprovincialis) under laboratory conditions and in metropolitan waters of Gulf St Vincent,South Australia

The anti-microbial agent triclosan (TCS), and its derivative methyl-triclosan (Me-TCS), are discharged with treated effluents from wastewater treatment plants to receiving environments. We investigated the bioconcentration of TCS and Me-TCS in mussels (Mytilus galloprovincialis) exposed to TCS (100 ng L⁻¹) for 30 days in seawater aquaria (19 ± 2 °C) with fresh phytoplankton as a food source. Bioconcentration increased with time reaching a steady-state around 24–30 days. The bioconcentration factor (log BCF) for TCS were 2.81 L kg⁻¹ (dry weight) and 4.13 L kg⁻¹, when lipid normalised concentrations were used. Mussels were also deployed in cages at four marine locations receiving effluents from WWTPs. The mean (±SD) TCS and Me-TCS concentrations for mussels from these sites were 9.87 (±1.34) and 6.99 (±2.44) μg kg⁻¹. The study showed that mussels can be a useful tool for monitoring pollution of TCS and Me-TCS in marine and estuarine environments.     

The use of selected genotoxicity assays in green-lipped mussels (Perna viridis): a validation study in Hong Kong coastal waters

In Hong Kong, discharges of domestic and industrial wastewaters and disposal of contaminated muds into coastal waters have resulted in high levels of persistent organic contaminants in the water column, biota and bottom sediments. Although the acute toxicity of effluents has been tested by government regulators using mortality-based bioassays, the sublethal effects of many of the pollutants, including environmental carcinogens, have not been well studied. The objective of the present work was to examine the efficiency and efficacy of using: (1) DNA strand breaks (comet assay and alkaline agarose gel electrophoresis assay); (2) oxidative DNA damage (levels of 8-hydroxy-2-deoxyguanosine in cellular DNA) and (3) micronuclei (MN) formation as early warning toxicological indicators of potential environmental carcinogen exposure. Green-lipped mussels (Perna viridis) were transplanted to study sites and retrieved after 4, 8, 12, 16 and 30 days. The bioaccumulation of organic pollutants, including the polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OC pesticides) and polychlorinated biphenyls (PCBs) was observed, and compared with biomarker assays. Some significant dose- and time-dependent inductions of the genotoxic biomarkers, including 8-OHdG, DNA strand breaks and micronuclei were observed. In particular, several very strong (r>0.9) and significantly positive relationships were found at all sites during days 0-12. In addition, significant strong relationships between certain organic contaminants (carcinogenic PAHs and 4 common OC pesticides) and micronuclei were detected at the polluted sites, Tsim Sha Tsui and Sai Wan Ho. The results suggest that the use of micronuclei as a biomarker is potentially effective, especially at the more polluted sites. Nonetheless, further research is required to validate their effectiveness under varying field conditions, especially to elucidate responses under lower contaminant loads, interactions between the environmental and physiological factors affecting organisms in differing coastal environments, and changes in biotransformation and DNA repair enzymes in test organisms.     

Ras gene in marine mussels: a molecular level response to petrochemical exposure

Mussels are susceptible to numerous toxicants and are often employed as bioindicators. This study investigated the status of the ras proto-oncogene in Mytilus galloprovincialis following petrochemical exposure. A M. galloprovincialis homologue of the vertebrate ras gene was isolated, showing conserved sequence in regions of functional importance and a high incidence of polymorphic variation. Mutational damage was investigated in mussels chronically exposed to the water-accommodated fraction of #4 fuel-oil (WAF), and in mussels collected along the NW coast of Portugal in sites with different levels of petrochemical contamination. A ras gene point mutation was identified in the codon 35 of one individual exposed to 12.5% WAF. No mutations were detected in mussels from the WAF control or environmental samples. This represents the first report of a ras gene mutation, experimentally-induced by petrochemical exposure, in an invertebrate species.     

Comparison of metal accumulation between 'Artificial Mussel' and natural mussels (Mytilus galloprovincialis) in marine environments

The passive sampler called 'Artificial Mussel' (AM) developed by Wu et al. (2007) can provide a time-integrated estimate of metal concentrations in the marine environment, and offers a potential device to assess and compare metal concentration in different marine environments worldwide. The aim of this study was to compare metal accumulation on AM and natural mussel Mytilus galloprovincialis at three sites with different metal loads along the Portuguese coast for four months. M. galloprovincialis were placed in cages alongside AMs at each site. Samples were collected monthly and Cd, Cr, Cu, Pb, and Zn concentrations in whole soft tissues and AMs compared. For both Cu and Cd, the results were similar between AMs and natural mussels. Higher concentrations of Zn were observed in natural mussels, whereas the inverse was shown for Pb (about 10-fold higher). Our results showed that AMs are promising tools for assessing metal concentrations in marine environments.     

The usefulness of transplantation studies in monitoring of metals in the marine environment: South African experience

Due to their close proximity to the point sources of pollution, estuaries and harbours are exposed to metals. Mussels are used worldwide to monitor marine pollution due to their ability to take up contaminants and the ease of transplantation. Mussels were collected from two reference sites and transplanted in Richards Bay Harbour (2006 and 2010) and in three harbours. Transplanted and resident mussels were removed after 6 weeks exposure and metal concentrations were analysed using ICP-MS techniques. Transplanted mussels had higher metal concentrations than the resident mussels. This was attributed to regulation of metals by the resident mussels. Metal regulation was greater in mussels that are continuously submerged as opposed to those that undergo tidal influences. For monitoring it is essential that the reference population for transplantation is considered carefully as upwelling events in the pristine reference location results in significant increases in metal bioaccumulation.     

Status of marine pollution research in South Africa (1960-present)

The published literature on marine pollution monitoring research in South Africa from 1960 to present was evaluated. There has been a general decline in the number of papers from the 1980s and this can be linked to the absence of a marine pollution monitoring programme in South Africa. General trends observed were that contaminant exposure monitoring of metals predominates the research conducted to date. Monitoring results indicate that there has been a general decrease in metal concentrations in South African coastal waters and concentrations of metals and most organics in mussels are lower than in other industrialised nations. This is reflected in the general pristine nature and high biodiversity of the South African coastline. The establishment of a national marine pollution monitoring framework would stimulate marine pollution research.     

Imposex in the indigenous Nassarius kraussianus (Mollusca: Neogastropoda) from South African harbours

Nassarius kraussianus populations in the Durban and Richards Bay harbours (along the eastern seaboard of southern Africa) and in the Knysna lagoon (southern Cape coast) showed imposex development, confirming bioavailability of tributyltin (TBT) in these waterways. Incidence of imposex (which ranged from 29% to 100%) and relative penis length of females (RPL; which ranged from 1.3% to 55.2%) were markedly variable among populations from different sites in each waterway, indicative of localised effects of TBT contamination. Shell length of the snails was apparently not correlated with contamination level, as assessed from imposex measurements. While population imposex features are easy to determine and often provide a sensitive biomarker of TBT exposure, the discussion outlines reservations when extrapolating these to general ecological situations. Additionally, this study represents the first published report on the topic for sub-Saharan, African harbours, some of which seem remarkably less affected than suggested for other world regions.     

模拟暴雨条件下农田磷素迁移特征

开展三次重复人工暴雨试验,研究太湖流域平原河网区农田磷素在暴雨径流过程中的迁移输出特征,结果表明,地表径流是暴雨径流过程农田磷素迁移的主要途径,地表径流水相和侵蚀相磷素迁移量分别占总磷输出量的58.50%和34.69%;随壤中水流输移的磷素仅占总磷输出量的6.81%,磷素迁移以颗粒态为主,约占总磷输出量的60.73%,溶解态磷素以无机磷酸盐输出为主,溶解态磷素更易于在土壤中运动,地表径流与壤中流磷素输出特征对比分析显示,土壤对磷素具有较强的滤减作用,尤其对总颗粒态附着磷浓度的消减效果明显,可达80%以上,尽管暴雨径流过程中磷素迁移以地表径流为主,然而在降雨丰富的太湖地区,一般降雨条件下壤中流是产流的主要形式,同时壤中流溶解态磷流失占有较大的比例,对区域水环境恶化具有重要贡献,因此加强壤中流溶解态磷素输移和控制研究具有重要意义.     

Field validation of antioxidant enzyme biomarkers in mussels (Perna viridis) and clams (Ruditapes philippinarum) transplanted in Hong Kong coastal waters

Green-lipped mussels, Perna viridis, and Manila clams, Ruditapes philippinarum were sourced from “clean” sites in the Hong Kong region, depurated in a laboratory using uncontaminated filtered seawater for 8 days, and transplanted to a suspected gradient of chemically polluted sites in Hong Kong. After 14- and 28-days of field exposure, several antioxidant parameters including glutathione S transferase (GST), catalase (CAT), glutathione peroxidase (GPx), and glutathione (GSH) were quantified in gill and hepatopancreas tissues. Whole body tissue concentrations of polycyclic aromatic hydrocarbons (PAHs), petroleum hydrocarbons (PHCs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCs) were determined in pooled site samples. Chemical analyses indicated that: (a) clams had higher levels of PAHs, PHCs, DDTs and PCBs, whereas mussels had higher hexachlorocyclohexane (HCHs) and there was no difference between species for dieldrin and remaining OCs; (b) Kat O should not be continued as a “clean” reference site for Hong Kong, because of the levels of contaminants measured and (c) PAH concentrations in the current survey were similar to those previously measured. Toxicological conclusions were: (a) antioxidant responses were different between species; (b) CAT and GST have highest utility in clams for field use in Hong Kong, whereas CAT in both gill and hepatopancreas tissue showed most potential in mussels; (c) significant induction of antioxidant responses over day 0 (excluding GPx in both tissues, and GST in mussel hepatic tissue); (d) groups of contaminants do not consistently induce antioxidant responses and (e) organochlorines and PCBs correlated significantly with CAT and GST in clam hepatopancreas and with CAT in mussel gill and hepatic tissue. Multivariate statistical techniques indicated little relationship between the site patterns for antioxidant responses and the contaminant gradients identified in body burden analysis.     

Baseline levels of benzo(a)pyrene in southern California mussels

Marine mussels accumulate the carcinogen benzo(a)pyrene from contaminated environments. Baseline studies in California indicate that levels of the carcinogen in mussels are at or near zero, except in areas of human activity. This finding runs counter to previous suggestions that benzo(a)pyrene is widely distributed in marine organisms.     

Recuperated-OSL dating of quartz from Aegean (South Greece) raised Pleistocene marine sediments: current results

The purpose of this work is to provide an OSL dating framework for raised marine sequences in the South-West coast of Greece during Upper Quaternary. Paleontological investigations and Geographic Information System (GIS) analysis on elevated marine landforms have proved that a record of uplift and eustacy exists in South Greece since the Early Pleistocene (～1.6 Ma). Hereby, we test the suitability of the SAR methodology for recuperated-OSL (Re-OSL), proposed by Wang et al. (2007), on coarse-grained quartz aliquots from emerged nearshore outcrops. Protocol's performance is examined on the basis of signal characteristics, dose response, sensitivity changes, recovery of known doses and Re-OSL bleachability to sunlight. The accuracy of the Re-OSL dates calculated for natural samples is also discussed.     

Molecular staging of marine medaka: a model organism for marine ecotoxicity study

Oryzias melastigma, also called O. dancena, is becoming a very useful model for estuarine and marine ecotoxicity studies. With O. melastigma being adopted by ILSI Health and Environmental Science Institute (HESI) for embryo toxicity testing, improved knowledge of biomarker based embryonic development becomes especially important for mechanism-based toxicity evaluations. Using whole mount in situ hybridization and immunostaining techniques together with widely used molecular markers, this study describes the molecular development of marine medaka embryos, focusing on the brain, eye, heart, pectoral fin, pancreas, liver, muscle and neuron system. These organs are targets of environmental pollutants that disrupt normal embryonic development in medaka and other fish.     

Field validation of antioxidant enzyme biomarkers in mussels (Perna viridis) and clams (Ruditapes philippinarum) transplanted in Hong Kong coastal waters

Green-lipped mussels, Perna viridis, and Manila clams, Ruditapes philippinarum were sourced from “clean” sites in the Hong Kong region, depurated in a laboratory using uncontaminated filtered seawater for 8 days, and transplanted to a suspected gradient of chemically polluted sites in Hong Kong. After 14- and 28-days of field exposure, several antioxidant parameters including glutathione S transferase (GST), catalase (CAT), glutathione peroxidase (GPx), and glutathione (GSH) were quantified in gill and hepatopancreas tissues. Whole body tissue concentrations of polycyclic aromatic hydrocarbons (PAHs), petroleum hydrocarbons (PHCs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCs) were determined in pooled site samples. Chemical analyses indicated that: (a) clams had higher levels of PAHs, PHCs, DDTs and PCBs, whereas mussels had higher hexachlorocyclohexane (HCHs) and there was no difference between species for dieldrin and remaining OCs; (b) Kat O should not be continued as a “clean” reference site for Hong Kong, because of the levels of contaminants measured and (c) PAH concentrations in the current survey were similar to those previously measured. Toxicological conclusions were: (a) antioxidant responses were different between species; (b) CAT and GST have highest utility in clams for field use in Hong Kong, whereas CAT in both gill and hepatopancreas tissue showed most potential in mussels; (c) significant induction of antioxidant responses over day 0 (excluding GPx in both tissues, and GST in mussel hepatic tissue); (d) groups of contaminants do not consistently induce antioxidant responses and (e) organochlorines and PCBs correlated significantly with CAT and GST in clam hepatopancreas and with CAT in mussel gill and hepatic tissue. Multivariate statistical techniques indicated little relationship between the site patterns for antioxidant responses and the contaminant gradients identified in body burden analysis.     

Survey of PAH in low density residential stormwater ponds in coastal South Carolina: false dark mussels (Mytilopsis leucophaeata) as potential biomonitors

The distribution of PAHs was studied in sediment and false dark mussels, Mytilopsis leucophaeata, of three brackish stormwater retention ponds on Kiawah Island, a gated residential community and golf resort. Impervious surface in pond watersheds ranged from 5 to 30%. Sediment concentrations were lower than those found in other studies of suburban residential areas, and there were no significant differences among ponds or seasons. Mean summation operatorPAH(16) values for sediments in Ponds 67, 100, and 37 were 184.7+/-101.3ng g(-1), 67.5+/-26.0ng g(-1), and 84.3+/-75.5ng g(-1), respectively. Mussel summation operatorPAH(16) concentrations from Pond 67 in August (mean 734.5+/-148.1ng g(-1)), and from Pond 37 in December (mean 1115.1+/-87.7ng g(-1)), were significantly higher than other ponds. Mean summation operatorPAH(16) values for mussels in Ponds 67, 100, and, 37 were 555.9+/-219.7ng g(-1), 312.5+/-99.1ng g(-1) and 737.8+/-419.8ng g(-1), respectively. The mean biota-to-sediment ratio was 7.6+/-8.1. Isomer ratios generally suggested pyrogenic sources. False dark mussels are a promising indicator species for PAH contamination because they are abundant, easy to sample, bioaccumulate PAH profiles representative of the time-integrated sediment profiles, and their PAH levels are less variable than either stormwater or sediment samples.     

Influence of stock origin and environmental conditions on the survival and growth of juvenile freshwater pearl mussels (Margaritifera margaritifera) in a cross-exposure experiment

The freshwater pearl mussel (Margaritifera margaritifera) is a highly specialized and sensitive freshwater bivalve, whose survival in the juvenile phase is indicative of high quality habitats. This contribution investigates the use of juvenile freshwater pearl mussels as bioindicators, considering the influence of mussel stock and study stream conditions on juvenile performance, as described by survival and growth rates. A standardized cross experiment was carried out investigating juvenile performance in four different pearl mussel stocks originating from the Rhine, Danube and Elbe drainages, representing distinct genetic conservation units. The juveniles were exposed in five study streams which were selected to integrate pearl mussel streams with different water qualities and recruitment status of the mussel population. Per study stream, five standard mesh cages containing an equal number of 20 (10 × 2) juvenile pearl mussels per stock in separate chambers were installed. Survival and growth rates of juveniles were checked after three months (i.e. before their first winter) and after nine months (i.e. after their first winter). Mussel stock and study stream conditions significantly influenced juvenile performance. Growth rates were determined by study stream conditions and increased with stream water temperature, organic carbon and C/N ratios. Survival rates varied stock-specifically, indicating different levels of local adaptation to their native streams. Due to the detection of stream-specific differences in juvenile performance, freshwater pearl mussels appear suitable as bioindicators. However, a careful consideration of stock-specificity is necessary to avoid false interpretation of bioindication results. The comparison of stock-specific survival in native versus non-native streams implicates that exposure of juveniles outside their native habitats is able to increase breeding success or else serve for risk spreading in breeding programs.     

Relationships between tissue concentrations of chlorinated hydrocarbons (polychlorinated biphenyls and chlorinated pesticides) and antioxidative responses of marine mussels,Perna viridis

Marine mussels, Perna viridis, were transplanted from a reference site to various polluted sites around Hong Kong. After 30 d of exposure, antioxidative responses in the gills and hepatopancreas and tissue concentrations of chlorinated hydrocarbons [polychlorinated biphenyls (PCBs) and chlorinated pesticides (CPs)] were determined for individual mussels. Glutathione S transferase (GST) and glutathione (GSH) were positively correlated with tissue PCB concentrations. Only one of the enzymatic antioxidants, glutathione peroxidase (GPx), showed significant response to tissue PCB. No significant correlation was found between tissue concentrations of chlorinated hydrocarbons and other enzymatic antioxidants (superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) and NADPH DT-diaphorase (DT-d). Oxidative stress, measured as thiobarbituric acid reactive substances, was correlated with chlorinated pesticide concentrations in tissues. This study demonstrated a correlation between GST/GSH and chlorinated hydrocarbons. The apparent lack of correlation between trace organic pollutants and some of the enzymatic antioxidants may be due to the inhibitory effects caused by these chemicals. The above results suggest that more investigations are needed before these enzymes can be used as biomarkers.     

A continuous record of artificial tritium fallout at the South Pole (1954–1978)

Snow samples were taken from a 5-m-deep pit located near the South Pole station in January 1975 and continuous deuterium, tritium and β activity profiles have been obtained from them. These three measurements and the stratigraphic observations allow us to deduce a precise chronology of the pit from 1950 to 1975, providing a continuous record of artificial tritium fallout in the southern hemisphere; this record has been extended to 1978 using samples from a second pit taken this last year. Taking advantage of the unusual 1957–1958 stable isotope content in the snow, we have demonstrated that an important part of the isotopic signal in the precipitation is retained in the snow in spite of the low accumulation rate (8.2 g cm^?2 yr^?1).The first artificial tritium, due to the 1952 Ivy experiments was detected during 1954. A two-year delay between explosions and fallout is well established and allows us to relate the tritium fallout to the main nuclear tests from 1952 to 1960. This delay appears longer for the large 1961–1962 devices. A stratospheric half residence time equal to 20 months is deduced from the fallout decrease occurring after the 1966 peak. For the French southern hemisphere experiments, it is about one year. A sharp tritium decrease is observed after a high 1973 peak, providing a new tritium reference level for future glaciological studies in Antarctica.The β and tritium peaks occur respectively during the Antarctic summer and the Antarctic winter, showing different injection mechanisms. This winter input and the high tritium values registered at the South Pole indicate a preferential tritium transfer over the pole area. Two mechanisms, stratospheric-tropospheric exchange and direct stratospheric cloud precipitation could account for this injection.     

Application of artificial neural networks in regional flood frequency analysis: a case study for Australia

Regional flood frequency analysis (RFFA) is widely used in practice to estimate flood quantiles in ungauged catchments. Most commonly adopted RFFA methods such as quantile regression technique (QRT) assume a log-linear relationship between the dependent and a set of predictor variables. As non-linear models and universal approximators, artificial neural networks (ANN) have been widely adopted in rainfall runoff modeling and hydrologic forecasting, but there have been relatively few studies involving the application of ANN to RFFA for estimating flood quantiles in ungauged catchments. This paper thus focuses on the development and testing of an ANN-based RFFA model using an extensive Australian database consisting of 452 gauged catchments. Based on an independent testing, it has been found that ANN-based RFFA model with only two predictor variables can provide flood quantile estimates that are more accurate than the traditional QRT. Seven different regions have been compared with the ANN-based RFFA model and it has been shown that when the data from all the eastern Australian states are combined together to form a single region, the ANN presents the best performing RFFA model. This indicates that a relatively larger dataset is better suited for successful training and testing of the ANN-based RFFA models.