A field survey of chemicals and biological products used in shrimp farming

This study documented the use of chemicals and biological products in marine and brackish water shrimp farming in Thailand, the world's top producer of farmed shrimp. Interviews were conducted with 76 shrimp farmers in three major shrimp producing regions, the eastern Gulf coast, the southern Gulf coast and the Andaman coast area. Farmers in the study used on average 13 different chemicals and biological products. The most commonly used products were soil and water treatment products, pesticides and disinfectants. Farmers in the southern Gulf coast area used a larger number of products than farmers in the other two areas. In the study, the use of more than 290 different chemicals and biological products was documented. Many of the pesticides, disinfectants and antibiotics used by the farmers could have negative effects on the cultured shrimps, cause a risk for food safety, occupational health, and/or have negative effects on adjacent ecosystems. Manufacturers and retailers of the products often neglected to provide farmers with necessary information regarding active ingredient and relevant instructions for safe and efficient use.     

Distribution of heavy metals in marine bivalves, fish and coastal sediments in the Gulf and Gulf of Oman

An assessment of marine contamination due to heavy metals was made in the Gulf and Gulf of Oman based on marine biota (fish and various bivalves) and coastal sediment collected in Bahrain, Oman, Qatar, and the United Arab Emirates (UAE) during 2000-2001. Sediment metal loadings were generally not remarkable, although hot spots were noted in Bahrain (Cu, Hg, Pb, Zn) and on the east coast of the UAE (As, Co, Cr, Ni). Concentrations of As and Hg were typically low in sediments and the total Hg levels in top predator fish commonly consumed in the region were < 0.5 microg g(-1) and posed no threat to public health. Very high Cd concentrations (up to 195 microg g(-1)) in the liver of some fish from southern Oman may result from food-chain bioaccumulation of elevated Cd levels brought into the productive surface waters by upwelling in the region. Very high As concentrations (up to 156 microg g(-1)) were measured in certain bivalve species from the region. Although not certain, the As is probably derived from natural origins rather than anthropogenic contamination.     

TBT-pollution in the Gulf of Thailand: A re-inspection of imposex incidence after 10 years

Imposex in neogastropods was used to determine the relative TBT distribution in the Gulf of Thailand in 2006. To identify the imposex prevalence, 8757 specimens, belonging to 22 species from five families of neogastropods, were collected at 56 sites in 13 sample areas. These areas were located between the Bight of Bangkok in the north and the Malaysian border in the south. A contamination model was developed to compensate for differences in TBT sensitivity among species and to make comparisons among areas. At every area imposex was found in neogastropods. The highest incidence was in the east side of the Bight of Bangkok off Si Racha and Pattaya and in the southern part around Pattani. The same areas showed the highest frequency of imposex in 1996. While the frequency of imposex appeared to have slightly decreased in these areas, increases were found elsewhere. In Pattani Province this could be related to dumping of highly polluted harbour sediments in the shallow coastal area. The overall frequency of imposex in the Gulf of Thailand significantly increased from 1996 to 2006.     

Magnetic monitoring of marine particulate pollution in the Elefsis Gulf,Greece

Measurements of magnetic susceptibility (χ) and saturation isothermal remanent magnetization (SIRM) on both filtered particulates and sediment samples provide a cheap, rapid and non-destructive method of particulate pollution monitoring in marine environments where ferrimagnetic iron oxides are important components of the discharge from industrial or urban complexes. The value of this approach is illustrated by reference to results obtained from the Elefsis Gulf, Greece, where the major source of particulate metal pollution is an iron and steel works discharging waste into a settling lagoon connected to the waters of the Gulf.     

Fate of drilling waste discharges and ecological risk assessment in the Egyptian Red Sea: an aquivalence-based fuzzy analysis

Egypt is located in the Northeast of Africa where oil and gas (O&G) are produced offshore from the Gulf of Suez and the Southeast part of the Mediterranean. The O&G production in Egypt is distributed as follows: 70% from Gulf of Suez, 16% from Western desert, 8% from the Sinai Peninsula and 6% from Eastern desert. Past O&G activities, refining and transport have resulted in chronic pollution in Egyptian offshore and numerous environmental programs have been initiated to protect new development areas from the environmental impacts. The offshore drilling process uses drilling fluids (mud) and generates waste fluids and cuttings, which could be the largest discharges going into the receiving water bodies. There are several options to manage offshore drilling wastes: offshore discharge, offshore down-hole injection and onshore disposal. Water-based drilling fluids (WBF) are commonly employed for drilling in Egyptian offshore because of their expected environmental benign behavior. The main objective of this paper is to develop a methodology to determine the fate of heavy metals associated with WBF drilling waste in the marine environment and estimate the associated ecological risks. Proposed contaminant fate model is based on an aquivalence approach, which has been integrated with fuzzy-based analysis to study the uncertainties. This research concluded that the impacts of heavy metals associated with the drilling waste discharges in the receiving waters are minimal.     

Distribution and origins of polycyclic aromatic hydrocarbons (PAHs) in riverine, estuarine, and marine sediments in Thailand

To assess the status of polycyclic aromatic hydrocarbon (PAH) contamination in coastal and riverine environments in Thailand, we collected 42 surface sediment samples from canals, a river, an estuary, and coastal areas in Thailand in 2003 and analyzed them for PAHs with 3-7 benzene rings by gas chromatography-mass spectrometry (GC-MS). The total concentration of PAHs ranged from 6 to 8399 ng/g dry weight. The average total PAH concentrations were 2290+/-2556 ng/g dry weight (n=8) in canals, 263+/-174 (n=11) in the river, 179+/-222 (n=9) in the estuary, and 50+/-56 (n=14) in coastal areas. Comparison of the concentration range with a worldwide survey of sedimentary PAH concentrations ranked PAH contamination in Thai sediments as low to moderate. The ratio of the sum of methylphenanthrenes to phenanthrene (MP/P ratio) allows discrimination of PAH sources between petrogenic (>2) and pyrogenic (<0.5) origins. Sediments from urban canals in Bangkok showed the highest PAH concentrations and petrogenic signatures (MP/P=1.84+/-0.98 [n=6] in canal sediments) with abundant alkylated PAHs, indicating major sources of petrogenic PAHs in the city. To identify the sources of the petrogenic inputs in Thailand, we analyzed triterpanes, biomarkers of petroleum pollution, in the sediment samples and in potential source materials. Hopane profiles were remarkably uniform throughout the nation, suggesting a diffuse single source (e.g. automobiles). Molecular profiles of hopanes and PAHs in sediments from the urban canals were similar to those in street dust, indicating that street dust is one of the major sources of petrogenic PAHs in the urban area. On the other hand, low levels of PAHs (approximately 50 ng/g) with a pyrogenic signature (MP/P ratio approximately 0.5) were widely recorded in remote areas of the coast and the Chao Phraya River. These pyrogenic PAHs may be atmospherically transported throughout the nation. Middle and lower reaches of the Chao Phraya River, the river mouth, and the upper Gulf of Thailand showed intermediate concentrations and profiles of PAHs, indicating mixtures of petrogenic and pyrogenic origins. Perylene was abundant in sediments, representing up to approximately 60% of total identified PAHs. High inputs of soil due to frequent heavy rains could contribute to the high perylene abundance in the sediments. Sedimentary PAH concentrations decreased offshore with a half distance of approximately 10 km in the upper Gulf off the mouth of the Chao Phraya River. This is probably due to active deposition of laterally transported riverborne particles.     

Heavy metals and polycyclic hydrocarbon compounds in benthic organisms of the Upper Gulf of Thailand

Concentrations of heavy metals and polycyclic aromatic hydrocarbons (PAHs) were measured in bivalves collected in the Upper Gulf of Thailand. PAHs detected included acenaphthene, acenaphthylene, benzo[a]pyrene, fluoranthene, methylphenanthrene, phenanthrene and triphenylene. Benzo[a]pyrene was detected in all species at concentrations varying from 1.0 to 8.2 ng·g^?1. Concentrations of cadmium, cobalt, copper, lead and nickel were significantly lower in bivalves from the Gulf than in green mussels collected from the mouth of the Chao Phraya River. No correlation was found between metal concentrations in animals and sediment, with the exception of copper. Copper concentrations in polychaetes and clams appeared to correlate with the copper:iron ratio of sediments. High rates of degradation were observed when radiolabelled chlorobenzene, phenanthrene and chrysene were added to water and sediment of the Chao Phraya River. Rates were lower in the waters and sediment of the Gulf of Thailand. The calculated half-lives of chlorobenzene in the Gulf of Thailand and the Chao Phraya River were about 130 and 68 days, respectively.     

Mercury contamination in tropical algal species of the Island of Penang,Malaysia

An investigation on the levels of mercury contamination in one species of the Cyanophyta, 14 species of the Rhodophyta, five species of the Phaeophyta and six species of the Chlorophyta from Penang waters indicated fairly low levels of bioaccumulated total mercury content. The bioaccumulated values ranged from below the detectable level to 0.35 μg g^?1 except for Padina sp. 1 which demonstrated an amount equivalent to 1.025 μg g^?1.These results indicate that the level of mercury contamination in the marine environment of Penang island falls within an acceptable range from the viewpoint of algal biodeposition.     

Distribution of petroleum hydrocarbons and organochlorinated contaminants in marine biota and coastal sediments from the ROPME Sea Area during 2005

The composition and spatial distribution of various petroleum hydrocarbons (PHs), comprising both aliphatic and polycyclic aromatic hydrocarbons (PAHs), and selected chlorinated pesticides and PCBs were measured in biota and coastal sediments from seven countries in the Persian Gulf and the Gulf of Oman (Bahrain, Iran, Kuwait, Oman, Qatar, Saudi Arabia and the United Arab Emirates). Evidence of extensive marine contamination with respect to organochlorinated compounds and PHs was not observed. Only one site, namely the BAPCO oil refinery in Bahrain, was considered to be chronically contaminated. Comparison of the results from this survey for Σ DDTs and Σ PCBs in rock oysters from the Gulf of Oman with similar measurements made at the same locations over the past two decades indicates a temporal trend of overall decreasing Σ PCB concentrations in oysters, whereas Σ DDTs levels have little changed during that period.     

Evaluation on surface current observing network of high frequency ground wave radars in the Gulf of Thailand

Due to the high cost of ocean observation system, the scientific design of observation network becomes much important. The current network of the high frequency radar system in the Gulf of Thailand has been studied using a three-dimensional coastal ocean model. At first, the observations from current radars have been assimilated into this coastal model and the forecast results have improved due to the data assimilation. But the results also show that further optimization of the observing network is necessary. And then, a series of experiments were carried out to assess the performance of the existing high frequency ground wave radar surface current observation system. The simulated surface current data in three regions were assimilated sequentially using an efficient ensemble Kalman filter data assimilation scheme. The experimental results showed that the coastal surface current observation system plays a positive role in improving the numerical simulation of the currents. Compared with the control experiment without assimilation, the simulation precision of surface and subsurface current had been improved after assimilated the surface currents observed at current networks. However, the improvement for three observing regions was quite different and current observing network in the Gulf of Thailand is not effective and a further optimization is required. Based on these evaluations, a manual scheme has been designed by discarding the redundant and inefficient locations and adding new stations where the performance after data assimilation is still low. For comparison, an objective scheme based on the idea of data assimilation has been obtained. Results show that all the two schemes of observing network perform better than the original network and optimal scheme-based data assimilation is much superior to the manual scheme that based on the evaluation of original observing network in the Gulf of Thailand. The distributions of the optimal network of radars could be a useful guidance for future design of observing system in this region.     

Organotin contamination in seafood and its implication for human health risk in Hong Kong

Organotins (OTs) have caused widespread adverse effects on marine organisms, while they can also induce health problems to humans via consumption of contaminated seafood. This study aimed to quantify the tissue concentrations of OTs in 11 seafood species in Hong Kong, and assess the human health risk for consuming these species. The tongue sole Paraplagusia blochii had the highest concentration of total OTs. Triphenyltin (TPT) accounted for 56–97% of total OTs. The highest hazard quotient (HQ) for TPT was 1.41 in P. blochii, while the HQs for butyltins were much less than 1. The results indicated that it is likely to have certain health risks for consuming P. blochii due to its high TPT contamination. Therefore, TPT should be a priority pollutant of concern. Appropriate management actions should be taken to control its use and release in the region in order to safeguard the marine ecosystem and human health.     

Impacts of gold mine waste disposal on deepwater fish in a pristine tropical marine system

Little is known about the impacts of mine waste disposal, including deep-sea tailings, on tropical marine environments and this study presents the first account of this impact on deepwater fish communities. The Lihir gold mine in Papua New Guinea has deposited both excavated overburden and processed tailings slurry into the coastal environment since 1997. The abundances of fish species and trace metal concentrations in their tissues were compared between sites adjacent to and away from the mine. In this study (1999-2002), 975 fish of 98 species were caught. Significantly fewer fish were caught close to the mine than in neighbouring regions; the highest numbers were in regions distant from the mine. The catch rates of nine of the 17 most abundant species were lowest, and in three species were highest, close to the mine. There appears to be limited contamination in fish tissues caused by trace metals disposed as mine waste. Although arsenic (several species) and mercury (one species) were found in concentrations above Australian food standards. However, as in the baseline (pre-mine) sampling, it appears they are accumulating these metals mostly from naturally-occurring sources rather than the mine waste.     

Chlorinated hydrocarbons in marine biota and coastal sediments from the Gulf and Gulf of Oman

The spatial distribution of various organochlorinated compounds was investigated in the Gulf and Gulf of Oman based on marine biota (fish and various bivalves) and coastal sediment collected in Bahrain, Oman, Qatar and the United Arab Emirates (UAE) during 2000-2001. Several potential organic contaminants from agricultural (e.g., DDT and its breakdown products, lindane, endrin, dieldrin, endosulfan) and industrial (PCBs) sources were measured. Sediment burdens for all compounds, even for an apparent hot spot near a refinery in Bahrain, were amongst the lowest reported for surface sediments from other seas. Concentrations of DDTs were low in the muscle and liver of all fish (orange spotted grouper and the spangled emperor) analysed. Similarly, the levels of chlorinated hydrocarbons were low in the various bivalve species, notably rock oysters and pearl oysters. These results contribute to the sparse regional database for organochlorinated compounds in the marine environment. Moreover, they can be used as the most recent end point for elucidating temporal trends. Whereas the levels, albeit relatively low, SigmaDDTs in the rock oysters from the Gulf of Oman have remained uniform, there has been an irregular but generally decreasing trend in concentrations of summation SigmaPCBs during the last two decades.     

Preliminary study on responses of marine nematode community to crude oil contamination in intertidal zone of Bathing Beach, Dalian

This study investigated the responses of marine nematodes to crude oil contamination in polluted and relatively uncontaminated sites in Dalian Xingang, China, 40 days after an oil spill. Samples were taken at different tide levels on the beach and at different positions along the beach. We present the results of a comparison of nematode assemblages from undisturbed sediment from the Xiajiahezi Bathing Beach with those from sediment from the Xinghai Bathing Beach contaminated with crude oil. A total of 1666 nematodes from 26 genera were found in this study. Results showed significant differences in nematode assemblages between samples from undisturbed controls and those from the polluted area. Nematode abundance, number of species, diversity and species richness decreased significantly with increasing levels of crude oil contamination. Fifteen genera were eliminated and seemed to be composed of species intolerant to crude oil contamination; only the abundance of Marylynnia sp. increased slightly.     

Contamination and toxic effects of persistent endocrine disrupters in marine mammals and birds

In recent years, several species of marine mammals and birds have been affected by uncommon diseases and unusual mortalities. While several possible causative factors have been attributed for these events, a prominent suspect is exposure to man-made toxic contaminants. Particularly, some of these man-made chemicals can disrupt normal endocrine physiology in animals. At CMES, our studies focus on exposure and toxic effects of endocrine disrupting chemicals, particularly organochlorines, in higher trophic level wildlife. Endocrine disrupting chemicals, such as organochlorine insecticides, polychlorinated biphenyls, organotins etc. are found in tissues of a wide variety of wildlife. Extremely high concentrations have been found in animals afflicted with diseases and/or victims of mass mortalities. Elevated contamination by organochlorines has been found in open sea animals such as cetaceans and albatrosses, which seemed to be attributable to their low capacity to metabolize toxic persistent contaminants. Significant correlations between biochemical parameters (serum hormone concentrations and cytochrome P450 enzyme activities) and residues of endocrine disrupting chemicals were found in some species of marine animals, which indicates that these chemicals may impose toxic effects in animals even at the current levels of exposure. In general, water birds and marine mammals accumulated the dioxin-like compounds with much higher concentrations than humans, implying higher risk from exposure in wildlife. The future issues of endocrine disrupting chemicals in humans and wildlife will have to be focused in developing countries.     

Long-term modification of Arctic lake ecosystems: Reference condition, degradation under toxic impacts and recovery (case study Imandra Lakes, Russia)

In this study, published data on Lake Imandra, north-west Russia, have been synthesised to investigate trends in lake contamination and recovery due to changing inputs of heavy metals and nutrients over time. Records of water chemistry, phytoplankton, zooplankton and fish communities have been used to determine the status of aquatic ecosystem health in three distinct phases of Lake Imandra's recent history. Firstly, background (reference) conditions within the lake have been established to determine lake conditions prior to anthropogenic influences. Secondly, a period of ecosystem degradation due to anthropogenic inputs of toxic metals and nutrients has been described. Finally, evidence of lake recovery due to recent decreases of toxic metals and nutrients has been explored. Pollution of Lake Imandra began in the 1930s, reaching a peak in the 1980s. Increases in heavy metal and nutrient inputs transformed the typical Arctic ecosystem. During the contamination phase, there was a decrease in Arctic species and in biodiversity. During the last 10 years, pollution has decreased and the lake has been recolonised by Arctic water species. Ecosystem recovery is indicated by a change of predominant species, an increase in the individual mass of organisms and an increase in the biodiversity index of plankton communities. In accordance with Odum's ecosystem succession theory, this paper demonstrates that the ecosystem has transformed to a more stable condition with new defining parameters. This illustrates that the recovery of Arctic ecosystems towards pre-industrial reference conditions after a reduction in anthropogenic stresses occur, although a complete return to background conditions may not be achievable. Having determined the status of current ecosystem health within Lake Imandra, the effect of global warming on the recovery process is discussed. Climate warming in Arctic regions is likely to move the ecosystem towards a predominance of eurybiontic species in the community structure. These organisms have the ability to tolerate a wider range of environmental conditions than typical Arctic inhabitants and will gain advantages in development. This indicates that the full recovery of Arctic ecosystems in a warming climate may not be possible.     

An analysis of the chemical and microbiological quality of ground water from boreholes and shallow wells in Zimbabwe

Groundwater from boreholes and shallow wells is a major source of drinking water in most rural areas of Zimbabwe. The quality of groundwater has been taken for granted and the status and the potential threats to groundwater quality have not been investigated on a large scale in Zimbabwe. A borehole and shallow well water quality survey was undertaken between January, 2009 and February, 2010 to determine the chemical and microbial aspects of drinking water in three catchment areas. Groundwater quality physico-chemical indicators used in this study were nitrates, chloride, water hardness, conductivity, alkalinity, total dissolved solids, iron, magnesium, manganese, potassium, calcium, fluoride, sulphates, sodium and pH. The microbiological indicators were total coliforms, faecal coliforms and heterotrophs. Principal component analysis (PCA) showed that most of the variation in ground water quality in all catchment areas is accounted for by Total Dissolved Solids (TDS), electrical conductivity (EC), sodium, bicarbonate and magnesium. The principal dissolved constituents in ground water are in the form of electrically charged ions. Nitrate is a significant problem as the World Health Organization recommended levels were exceeded in 36%, 37% and 22% of the boreholes in the Manyame, Mazowe and Gwayi catchment areas respectively. The nitrate levels were particularly high in commercial farming areas. Iron and manganese also exceeded the recommended levels. The probable source of high iron levels is the underlying geology of the area which is dominated by dolerites. Dolerites weather to give soils rich in iron and other mafic minerals. The high level of manganese is probably due to the lithology of the rock as well as mining activity in some areas. Water hardness is a problem in all catchment areas, particularly in the Gwayi catchment area where a value of 2550 mg/l was recorded in one borehole. The problems with hard water use are discussed. Chloride levels exceeded the recommended levels in a few areas under irrigation. Most of the chloride is probably from agricultural activity particularly the application of potassium chloride. Fluoride levels were particularly elevated in the Gwayi catchment area and this is because of the geology of the area. There was no evidence of microbial contamination in all the boreholes sampled as the total coliform, faecal coliforms, heterotrophs count was nil. However, severe microbial contamination was found in the wells especially those in clay areas.     

Source and dispersal of suspended sediment in the macro-tidal Gulf of Kachchh

The macro-tidal Gulf of Kachchh, covering nearly 7000 km(2), is located about 150 km south of the Indus River mouth. In spite of semi-arid climate and lack of major rivers flowing into it, the Gulf is highly turbid with suspended sediment concentrations (SSC) during October-November 2002 ranging between 0.5 and 674 mgl(-1). Highly turbid waters are observed towards the northern portion of the mouth of the Gulf, at the head of the Gulf and adjacent to the numerous shoals present within the Gulf. Perennial high SSC in the Gulf is due to resuspension of sediments by strong tidal currents, shallow bathymetry and presence of fine-grained sediments on the sea floor. Numerical model studies show that there is a dynamic barrier in the central Gulf, which prevents the exchange of water and suspended sediments between the outer and inner Gulf. This dynamic barrier associated with strong east-west tidal currents restricts the turbid waters mainly to the northern Gulf, resulting in relatively clear waters (SSC<10 mgl(-1)) in the southern and central portions of the Gulf. Laser particle size distribution, clay mineralogy and geochemistry of the suspended matter show that the main source of sediments to the Gulf of Kachchh is the Indus River. Although the Indus discharge has been severely curtailed in the recent decades due to construction of numerous dams and barrages, the Gulf of Kachchh continues to receive resuspended sediments from the numerous meso and macro-tidal creeks of the Indus delta. The sediments at the head of the Gulf appear to be a mixture of sediments derived from the Indus as well as the numerous seasonal rivers draining the Rann of Kachchh.     

The most temperature-adapted corals have an Achilles' Heel

The corals of the Persian/Arabian Gulf are better adapted to temperature fluctuations than elsewhere in the Indo-Pacific. The Gulf is an extreme marine environment displaying the highest known summer water temperatures for any reef area. The small and shallow sea can be considered a good analogue to future conditions for the rest of the world’s oceans under global warming. The fact that corals can persist in such a demanding environment indicates that they have been able to acclimatize and selectively adapt to elevated temperature. The implication being that colonies elsewhere may be able to follow suit. This in turn provides hope that corals may, given sufficient time, similarly adapt to survive even in an impoverished form, under conditions of acidification-driven lowering of CaCO₃ saturation state, a further consequence of raised atmospheric CO₂. This paper demonstrates, however, that the uniquely adapted corals of the Gulf may, within the next three centuries, be threatened by a chronic habitat shortage brought about by the dissolution of the lithified seabed on which they rely for colonisation. This will occur due to modifications in the chemical composition of the Gulf waters due to climate change.     

Seasonal variation in water column conditions in the upper Gulf of Thailand

Seasonal variation in water column conditions in the upper Gulf of Thailand (UGoT) was analyzed by considering four major factors including surface heat flux, freshwater discharge, tidal and wind stirrings. The coincidence of surface heat loss, low river discharge and strong wind resulted in vertical well-mixing in December. Strong stratification developed in September and October due to large river discharge and moderate heat flux. Strong surface heating in April and May has a potential to generate strong stratification, although not as large as that in September and October due to low river discharge. Although no factors are prominent during January and March, and June and August, weak to moderate stratification results, because the influences of river discharge and surface heating are still larger than those of tidal and wind stirrings. The results of water column analysis based on monthly average data agree well with analyses derived from cruise data in the same months. Most analytical results correspond to the distributions of temperature and salinity from field observations. Disagreement, however, was found in December 2003 (cruise CU-2) when stratification in some small regions occurs in the distribution of water properties, but the water column analysis suggests vertical well-mixing. This phenomenon is triggered by non-uniform distribution of freshwater over UGoT, which is related to river discharge, monsoonal wind and current. Compared to a previous study regarding surface chlorophyll dynamics, water column conditions may be used to explain the occurrence of phytoplankton bloom in this region.