Concentration Of Produced Water Research Articles

Advantages of model averaging of species sensitivity distributions used for regulating produced water discharges.

Produced water (PW) generated by Australian offshore oil and gas activities is typically discharged to the ocean after treatment. These complex mixtures of organic and inorganic compounds can pose significant environmental risk to receiving waters, if not managed appropriately. Oil and gas operators in Australia are required to demonstrate that environmental impacts of their activity are managed to levels that are as low as reasonably practicable, for example, through risk assessments comparing predicted no-effect concentrations (PNECs) with predicted environmental concentrations of PW. Probabilistic species sensitivity distribution (SSD) approaches are increasingly being used to derive PW PNECs and subsequently calculating dilutions of PW (termed "safe" dilutions) required to protect a nominated percentage of species in the receiving environment (e.g., 95% and 99% or PC95 and PC99, respectively). Limitations associated with SSDs include fitting a single model to small (six to eight species) data sets, resulting in large uncertainty (very wide 95% confidence limits) in the region associated with PC99 and PC95 results. Recent advances in SSD methodology, in the form of model averaging, claim to overcome some of these limitations by applying the average model fit of multiple models to a data set. We assessed the advantages and limitations of four different SSD software packages for determining PNECs for five PWs from a gas and condensate platform off the North West Shelf of Australia. Model averaging reduced occurrences of extreme uncertainty around PC95 and PC99 values compared with single model fitting and was less prone to the derivation of overly conservative PC99 and PC95 values that resulted from lack of fit to single models. Our results support the use of model averaging for improved robustness in derived PNEC and subsequent "safe" dilution values for PW discharge management and risk assessment. In addition, we present and discuss the toxicity of PW considering the paucity of such information in peer-reviewed literature. Integr Environ Assess Manag 2024;20:498-517. © 2023 Commonwealth Scientific and Industrial Research Organisation. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Composition of Xanthan gum produced by Xanthomonas campestris using produced water from a carbonated oil field through Raman spectroscopy

Produced water (PW) is a by-product generated throughout oil exploration. Geological formation and geographical location of the reservoir influence its physical, chemical and biological characteristics. Xanthan gum (XG), an exopolysaccharide (EPS) produced by Xanthomonas campestris, has been widely used in enhanced oil recovery (EOR) technology because of its high viscosity, pseudoplastic behavior, stability in function of salinity, temperature and alkaline conditions. The production of XG may be affected by the composition of the PW, where the acetyl and pyruvyl radicals may be present in the mannoses. The aim of this study was to evaluate the composition of XG produced by X. campestris, particularly the amount of Xanthan, acetyl and pyruvyl groups, in culture mediums containing distilled (DW) or produced (PW) water in different concentrations, by means of dispersive Raman spectroscopy (1064 nm). The spectra of XG showed peaks referred to the main constituents of the Xanthan (glucose, mannose and glucuronic acid). Spectral features assigned to pyruvyl were seen in all samples mainly at ~1010 cm−1, with higher intensity when using DW and 25% PW. PCA loadings showed that the peaks assigned to pyruvyl are consistent to presence of sodium pyruvate (~1040/~1050 and ~ 1432 cm−1) and were higher in the samples obtained in 25% PW. ANOVA GLM applied to Raman peaks of interest (~1010 and ~ 1090 cm−1) and to PCA scores (Score 1 to Score 3) showed that both were influenced by the type of water used in the culture medium, where the XG were strongly reduced in the groups PW compared to DW while the pyruvyl content increased proportionally with the concentration of PW. The results suggest that the composition of the water used in the bacteria's culture medium influenced the composition of XG, including the amount of Xanthan and particularly the pyruvyl content, and therefore needs to be considered when using this approach of injecting XG in oil fields as pyruvyl content affects viscosity.

Environmental impact of utilization of \u201cproduced water\u201d from oil and gas operations in turfgrass systems

This study attempted to use produced water (PW) to irrigate turfgrass species, Cynodon dactylon and Paspalum sp. Assessment on established grasses, heavy metal accumulation and germination tests for weeds and turf grass seeds were conducted to evaluate the impact of PW irrigation. C. dactylon depicted lower tolerance while Paspalum sp. showed better tolerance capacity towards PW. C. dactylon grown from seeds under greenhouse conditions were not able to tolerate more than 30% concentration of PW (4.5% salinity). In comparison to tap water irrigated turf grass, Paspalum sp. was found to accumulate higher concentrations of V and Pb in shoots and Cr, Ni and As in roots. The results of seed germination tests recommended that irrigation with PW is to be performed after turfgrass establishment. Germination tests also revealed that PW could encourage growth of the weed—Chloris virgata while it could discourage growth of Amaranthus viridis and Launaea mucronata. This study suggests that PW could be used for turfgrass as an alternative water resource but only after further research on the long-term scale.

Acute toxicity of produced water on selected organisms in the aquatic environment of the niger delta

The discharge of produced water (PW) and drill cuttings from oil operations may elicit varied toxicity in fresh, brackish and marine organisms when exposed. The Niger Delta region which is the oil and gas province of Nigeria have incessantly been recipients of produced water. The study was aimed at investigating the toxic effects of produced water on freshwater fish- Oreochromis niloticus and brackish water shrimp- Palaemonetes africanus in the Niger Delta region of Nigeria. Probit toxicity tests were conducted on the organisms through a 96 h bioassay using produced water (PW) obtained from Mobil, Qua Iboe Terminal (QIT) in Eket, Akwa Ibom State, Nigeria. The organisms were tested in separate tanks containing produced water of 0.0, 100, 200, 400, 800 and 1000 mL, mixed with 2 L of habitat water (fresh/ brackish water). The physicochemical properties of the mixtures were determined by multiparameter hand held probe and atomic absorption photometer (AAS). The physico-chemical parameters, particularly the pH, and conductivity of the PW at 26.5 °C were significantly higher (p < 0.05) than those of the freshwater and brackish water samples. O. niloticus at the end of the 96 h test were 35%, 45%, 60%, 70% and 85%; while P. africanus had percentage mortalities of 25%, 35%, 45%, 60% and 80% at produced water (PW) of 5%, 10%, 20%, 40% and 50% respectively. Mortality rates of both test organisms being directly proportional to the percentages of PW and zero mortality recorded in the controls suggest that PW inflicted significant acute toxicity on the tested species. Higher mortality rates recorded in O. niloticus than P.africanus could be attributed to the increase of salinity following the introduction of the PW in the fresh water test media. The concentrations of PW administered in the study which were below the LC50 were are 49,500 and 99,000 ppm, while 198,000, 396,000, and 495,000 ppm were above the LC50. Results showed that the PW collected from the Mobil QIT effluent point source was toxic to the aquatic organisms, particularly the freshwater Oreochromis niloticus. We therefore speculate that 99,000 ppm of PW may be considered as the “no observed effect concentration” (NOEC).

Physiological and enzymatic responses of Chlorella vulgaris exposed to produced water and its potential for bioremediation.

In South America, Colombia is known as an important oil-producing country. However, the environmental impact of crude oil industry has not been studied deeply and few studies have been carried out for evaluating responses of algae and its adaptation under specific conditions. Enzymatic and physiological effects in Chlorella vulgaris and its potential for bioremediation after exposure to produced water (PW) were assessed using different PW concentrations (0, 25, 50, 75 and 100%) and crude oil. Variables such as cell density, growth rate (μ), percentage of growth inhibition (% I), chlorophyll a and b and cell diameter were evaluated during 5days. Furthermore, enzymatic biomarkers such as superoxide dismutase (SOD) and catalase (CAT) were also measured. Results showed that the treatment with 100% PW had the highest cell density and μ; similarly, 25% PW treatment had a similar behaviour, being these two treatments with the highest growth. A dose-dependent response was seen for chlorophyll a and b and cell diameter, showing significant differences between treatments and the control. Different levels of SOD and CAT were observed in algae exposed to PW. At 24h, an increase in SOD and CAT activity was observed, probably due to effects caused by xenobiotics. After 72h, a decrease in the activity of both enzymes was observed. The results evidenced that C. vulgaris can adapt easily to PW, showing an increase on its growth and stabilisation in its antioxidant activity. Additionally, cell diameter results and decrease of hydrocarbons and phenols show the potential of these algae to degrade xenobiotics from PW.

Risk assessment of human exposure to Ra-226 in oil produced water from the Bakken Shale

Unconventional oil production in North Dakota (ND) and other states in the United States uses large amounts of water for hydraulic fracturing to stimulate oil flow. Most of the water used returns to the surface as produced water (PW) containing different constituents. Some of these contents are total dissolved solids and radionuclides. The most predominant radionuclide in PW is radium-226 (Ra-226) of which level depends on several factors including the content of certain cations. A multivariate regression model was developed to predict Ra-226 in PW from the Bakken Shale based on the levels of barium, strontium, and calcium. The simulated Ra-226 activity concentration in PW was 535 pCi/L supporting extremely limited actual data based on three PW samples from the Bakken (527, 816, and 1210 pCi/L). The simulated activity concentration was further analyzed by studying its impact in the event of a PW spill reaching a surface water body that provides drinking water, irrigation water for crops, and recreational fishing. Using food transfer factors found in the literature, the final annual effective dose rate for an adult in ND was estimated. The global average annual effective dose rate via food and drinking water is 0.30 mSv, while the predicted dose rate in this study was 0.49 mSv indicating that there is potential risk to human health in ND due to Ra-226 in PW spills. This predicted dose rate is considered the best case scenario as it is based on the simulated Ra-226 activity concentration in PW of 535 pCi/L which is close to the low end actual activity concentration of 527 pCi/L.

Growth performance and phytoremediation ability of &lt;i&gt;Azolla pinnata&lt;/i&gt; in produced water

In the present study, effect of produced water on the growth of Azolla pinnata was observed and the phytoremediating ability of the plant was also exploited. A. pinnata was grown in produced water concentrations of 0% (control), 5%, 10%, 15%, 20% and 25%. The plant exhibited reduced growth rate in a concentration dependent order. Toxicity symptoms of produced water on the plant include chlorosis, frond disintegration and eventual death. Produced water exposure resulted in less than 20% growth inhibition in 5- 15 % treatment concentrations. The optimum removal efficiency concentration of produced water by A. pinnata was at 10- 20%. It was revealed that A. pinnata has low potential for improving the quality of produced water at high concentrations. This study exposed the need for proper produced water treatment and strict monitoring to ensure compliance with standards set by regulatory bodies before its discharge to surface water to mitigate the environmental impacts.Key Words: produced water, heavy metal, aquatic macrophytes.

Effect of varying ratios of produced water and municipal water on soil characteristics, plant biomass, and secondary metabolites of Artemisia annua and Panicum virgatum

Coal-bed natural gas production in the U.S. in 2012 was 1655 billion cubic feet (bcf). A by-product of this production is co-produced water, which is categorized as a waste product by the Environmental Protection Agency. The effects of varying concentrations of coal-bed methane (produced) water were studied in the greenhouse to elucidate their effects on two species as feedstock for lignocellulosic ethanol production: Panicum virgatum L. and Artemisia annua L. Two populations of A. annua were used, one from Canada and the other from Bulgaria. Plants were treated with varying ratios of produced water: control (0% produced or 100% municipal water), 25% produced, 50% produced, 75% produced, and 100% produced water. With increased concentration of produced water, the soil soluble Na increased, whereas soil soluble Mg and Ca decreased. The Na adsorption ratio (SAR) increased from 2 in the control to 21 in the 100% produced water treatment, and significant interaction was observed between the crop and water terms for electrical conductivity and phosphorus bicarbonate. SAR also increased in soils with both varieties of wormwood and with switchgrass as a result of increased concentrations of produced water. In addition, SAR was influenced by crop; SAR was higher in soil under switchgrass than in soil under the wormwood varieties. The biomass yields had significant interaction between crop and water treatments with Bulgarian wormwood consistently yielding more until the highest concentration of produced water when it decreased below that of Canadian wormwood. Bulgarian wormwood yielded the most with 131g/pot for the control followed by the 75% (118g/pot, statistically similar to control), 25% (111g/pot, statistically similar to control), and 50% (107g/pot) treatments. Biomass yields were reduced in the 100% produced water treatment. Regression analysis of the Canadian wormwood essential oil yield and constituents revealed weak correlations to increasing treatment of produced water. β-pinene, for which a quadratic yield curve was present, indicated a steep decline and leveling off of β-pinene production at high concentrations of produced water. The study shows increasing accumulation of Na and salts in the soil with increasing concentration of the produced (saline–sodic) water. High concentrations of these ions (average Na concentrations were 1156mgl−1) and salts in the 100% produced water treatment hampered growth and development of the plants. Implications of this research indicate that produced water could be utilized chemically untreated if diluted with high quality water. Produced water concentrations in dilution can be no higher than 25% in order to avoid deleterious soil and plant growth effects.

In Vivo Effects of Environmental Concentrations of Produced Water on the Reproductive Function of Polar Cod (Boreogadus saida)

Offshore oil and gas drilling processes generate operational discharges such as produced water (PW), a complex mixture of seawater with polycyclic aromatic hydrocarbons (PAH) and alkylphenols (AP). Some of these compounds may interact with the endocrine system of marine organisms and alter reproductive functions. In this study, polar cod were exposed for up to 28 d to a mixture of PAH, alkylated PAH, and AP simulating the composition of North Sea PW, at low and high concentrations (1:2000 and 1:1000 dilution of the original concentrate, respectively). Potential adverse effects of PW on polar cod physiology were investigated through biomarkers of biotransformation (hepatic ethoxyresorufin O-deethylase [EROD] activity and bile PAH metabolites), endocrine disruption (plasma vitellogenin [VTG] levels and sex steroid concentrations), and gonad histology. Plasma sexual steroid levels in fish were not markedly affected by PW exposure, while higher plasma VTG concentrations were measured in females exposed to the high PW treatment for 7 and 28 d. In males exposed to the higher PW concentration, inhibition of spermatogenesis was observed after 28 d in addition to increase of melano-macrophage occurrence in testis. Females exposed to the high PW treatment for 21 d showed a significant increase of atresia incidence. Finally, a significant decrease in oocyte number was observed in high PW exposed female ovaries after 28 d of exposure.

Modelling produced water dispersion and its direct toxic effects on the production and biomass of the marine copepod Calanus finmarchicus

Zooplankton is a key group in North Atlantic and Arctic food chains, and assessment and minimization of adverse effects from petroleum activities to this resource are important. The potential direct effects of produced water discharges on the biomass of Calanus finmarchicus were evaluated using a fully coupled, high resolution 3D hydrodynamic-ecological model system (SINMOD). Several scenarios with varying effects of produced water concentrations were considered. In order to reduce numerical dilution of the produced water effluents, a “sub grid” model component of higher resolution (80 m horizontal resolution vs 800 m for the main model grid) was developed and implemented. The results show that dilution and dispersion of produced water varies between locations. In general, realistically simulated concentrations of produced water were too low to have significant effects on the C. finmarchicus biomass and reproduction according to the toxicity-dilution profiles used, even when the toxicity of the produced water was increased 10-fold. The decrease in C. finmarchicus biomass was partially compensated by a slight increase in production.

Fungi Isolated from Produced Water and Water-Soluble Fraction of Crude Oil

&#x0D; This study was sought to determine the fungi present in the produced water (PW) and water- soluble fraction (WSF) of crude oil as a preliminary approach to determining that fungi can survive in crude oil polluted water and their possible use in bioremediation. Different concentrations of PW and WSF of crude oil samples from Ughelli East Flow Station in Delta State of Nigeria were exposed to onion (Allium cepa) primordial cells at different concentrations for twelve days. Thereafter, samples of the PW and WSF were cultured on Potato Dextrose Agar. Isolates of Thamnidium sp, Gelasinospora sp, Zygorhynchus sp and Colletotrichum sp were found. Zygorhynchus and Colletotrichum were associated with PW while Thaminidium and Gelasinospora associated with the WSF. There were changes in the pH and turbidity of the PW and WSF before and after exposure to Allium cepa cells. At 25% level of treatments there were significant differences in pH and turbidity values of the PW and WSF at P &lt; 0.05 and P &gt; 0.01 before and after exposure to the plant.&#x0D; &#x0D;

Biomarker responses in Atlantic cod (Gadus morhua) exposed to produced water from a North Sea oil field: Laboratory and field assessments

Biological markers of produced water (PW) exposure were studied in Atlantic cod (Gadus morhua) in both laboratory and field experiments, using authentic PW from a North Sea oil field. In the laboratory study, the PW exposure yielded significantly elevated levels of metabolites of polycyclic aromatic hydrocarbons (PAHs) and alkylphenols (APs) in bile even at the lowest exposure dose (0.125% PW). Other biomarkers (hepatic CYP1A induction and DNA adduct formation) responded at 0.25% and 0.5% PW concentrations. In the field study, bile metabolite markers and hepatic CYP1A were clearly increased in fish caged close to the PW outfall. Induction of plasma vitellogenin was not found in laboratory or field exposures, suggesting that the levels of oestrogen agonists (such as APs) might not have been sufficient to elicit induction, under the present conditions. The applicability of the biomarkers for use in water column biomonitoring programs is discussed.

The immune response of juvenile Atlantic cod ( Gadus morhua L.) to chronic exposure to produced water

Produced water (PW) is the main discharge from the offshore oil industry and contains oil-derived compounds such as poly-aromatic hydrocarbons, phenols, alkylphenols, and heavy metals. Studies suggest that PW discharges may affect the biota over larger areas from the oil drilling sites at sea than originally predicted. We investigated the effects of chronic exposure to PW on some aspects of juvenile Atlantic cod immunity, stress response and growth by intermittently exposing fish to 0, 100 or 200 ppm of PW for 22 weeks. No significant effects of PW were observed on growth, hepatosomatic index, condition factor or plasma cortisol. The respiratory burst (RB) of circulating leukocytes was significantly elevated in the 100 ppm group only, while the RB of head–kidney leukocytes was significantly decreased in both the 100 and 200 ppm groups. Significant up-regulation of the mRNA expression of β-2-microglobulin, immunoglobulin-M light chain and interleukins-1β and −8 was observed in the 200 ppm group, while the down-regulation of interferon stimulated gene 15 was obvious for both the 100 and 200 ppm groups. The results suggest that chronic exposure to environmentally relevant concentrations of PW causes modulations of the immune system of juvenile Atlantic cod with most immune parameters being stimulated, potentially resulting in an energetic cost that may be detrimental to the fish.

Produced water extracts from North Sea oil production platforms result in cellular oxidative stress in a rainbow trout in vitro bioassay

Produced water (PW) discharged from offshore oil industry contains chemicals known to contribute to different mechanisms of toxicity. The present study aimed to investigate oxidative stress and cytotoxicity in rainbow trout primary hepatocytes exposed to the water soluble and particulate organic fraction of PW from 10 different North Sea oil production platforms. The PW fractions caused a concentration-dependent increase in reactive oxygen species (ROS) after 1 h exposure, as well as changes in levels of total glutathione (tGSH) and cytotoxicity after 96 h. Interestingly, the water soluble organic compounds of PW were major contributors to oxidative stress and cytotoxicity, and effects was not correlated to the content of total oil in PW. Bioassay effects were only observed at high PW concentrations (3-fold concentrated), indicating that bioaccumulation needs to occur to cause similar short term toxic effects in wild fish.

Pilot-Scale Engineered Wetland Design for Produced Water Treatment

Summary Engineered wetlands are a promising technology for treatment of oilfield and gasfield produced water. The engineering optimization of natural treatment processes, adapted from chemical engineering reactor design principles, shows that engineered wetlands are a viable alternative to mechanical produced water treatment systems. Engineered wetlands incorporate a subsurface flow gravel bed reactor, lined with an impermeable liner and equipped with an aeration system to enhance oxygen delivery. Design parameters include biodegradation rate coefficients for biochemical oxygen demand (BOD) and individual organic compounds, produced water flowrate, temperature, and influent and required effluent concentrations. An oil and gas company in the Caspian region is seeking to use engineered wetlands for treatment of oilfield and gasfield produced water. The oilfield produced water concentrations are high in total dissolved solids (TDS: 43048 mg/L), BOD (14693 mg/L), and oil and grease (1213 mg/L) and moderately high in total benzene, toluene, ethylbenzene, and xylenes (BTEX; 3.067 mg/L). The gasfield produced water concentrations are moderately high in TDS (16110 mg/L), BOD (9910 mg/L), and oil and grease (557 mg/L) and high in total BTEX (12.393 mg/L). Pilot-scale engineered wetland treatment systems have been designed on a flowrate basis of 100 m3/d using the first-order kinetic mass reaction model recently published by Kadlec and Wallace (2009). This model uses a modified tanks-in-series number that accounts for both hydraulic effects and weathering effects in the biodegradation rate. Hydraulic effects are caused by dispersion in the saturated gravel bed. Variation in the biodegradation rate is because of rapid biodegradation at the upgradient portion of the engineered wetland, in which short chain/low molecular weight organics are oxidized at rapid rates, and slower biodegradation at the downgradient portion of the engineered wetland, in which long chain/higher molecular weight organics are oxidized at lower rates. This advanced design process, combined with BOD surface area loading criteria, enables the optimization of engineered wetland design for produced water treatment.

SURVIVAL AND GROWTH OF THE DOMINANT SALT MARSH GRASS SPARTINA ALTERNIFLORA IN AN OIL INDUSTRY SALINE WASTEWATER

Saline oil produced water (PW) is the largest wastewater stream in the oil exploration and production processes. Although eventual disposal of PW into shallow coastal waters occurs nearby coastal wetlands, no studies regarding its toxicity to higher plants were found in our literature review. To fill this knowledge gap and evaluate the potential use of this halophyte for PW phytoremediation the salt marsh grass Spartina alterniflora was grown in five PW concentrations and no PW treatment control for seven weeks. The oil & grease, NaCl, and ammonium (N-NH4+) concentrations in the PW were 120 mg L−1, 30 g L−1, and 381 mg L−1, respectively. Plants grown in 30% PW and 10% PW achieved survival rates (75%) significantly higher than plants grown in 100% PW (35% survival). LT50 of S. alterniflora to raw PW with 120 mg L−1 of oil & grease (100% PW) was estimated at 30 days. Root and sprout biomass were significantly stimulated by PW; plants grown in 10% to 50% PW concentrations were 70–300% more productive than those in control, 80% PW and 100% PW, respectively. No significant inhibitory effects on survival or growth were detected for concentrations of PW less than 80% when compared to control. Our results pointed out that S. alterniflora grows in saline oil PW and its potential use to phytoremediate this effluent should be evaluated.

Immune modulation in the blue mussel Mytilus edulis exposed to North Sea produced water

The discharge of oil well produced water (PW) provides a constant source of contaminants to the marine environment including polycyclic aromatic hydrocarbons, alkylated phenols, metals and production chemicals. High concentrations of PW cause adverse effects to exposed biota, including reduced survival, growth and reproduction. Here we explore the effects of PW on immune function in the blue mussel, Mytilus edulis. Mussels were exposed for 21 days to sublethal PW concentrations (0.125–0.5%) and cellular parameters were measured. Cell viability, phagocytosis and cytotoxicity were inhibited after exposure to 0.25% and 0.5% PW, whilst the 0.125% PW treatment produced significant increases in these biomarker responses. This biphasic response was only observed after 7 days exposure; longer exposure periods led to a reduction in immune parameters. Results indicate that PW concentrations close to the discharge point cause modulation to cellular immunity. The implications for longer-term disease resistance are discussed.

Modelling the uncertainties in predicting produced water concentrations in the North Sea

A random walk model has been used to compute concentration distributions of dispersed oil in the North Sea resulting from produced water discharges. This formed part of a joint study commissioned by Statoil, OLF and BP International with modelling being undertaken by SINTEF and the Brixham Environmental Laboratory. The model has been set up using predicted tidal currents from the Norwegian Meteorological Office 20-km grid three-dimensional Continental Shelf model for the year 1990. Climatology data from the North Sea have been used to define the variation of the thermocline depth at monthly intervals over the year, and wind data from the East Shetland Basin have been used to compute the vertical mixing rates. Peak concentrations of dispersed oil were predicted to be approximately 3 μg l −1 in the East Shetland Basin, assuming no biodegradation; this value is consistent with the measurements of Stagg et al. (In: Reed, M., Johnsen, S. (Eds), Produced Water 2, Environmental Issues and Mitigation Technologies, Plenum Press, 1996), where the data were collected in the immediate vicinity of the discharges and the effects of degradation would be expected to be negligible. A matrix of model runs was undertaken with different parameter values for the degradation of dispersed oil, horizontal and vertical mixing, and the mixing across the thermocline. These results were used to estimate the sensitivity of the model and the uncertainty in the predicted concentration fields. The results indicate that for the areas of high concentration, a band approximately 150-km wide stretching up the centre of the North Sea, parameterisation of the vertical mixing is most important for predicting the concentration levels. For areas more remote from the discharges and closer to the land masses, the degradation rate of material has most effect on predicted concentrations.

Effects of an oil and gas-production effluent on the colonization potential of giant kelp (Macrocystis pyrifera) zoospores

Point sources of pollution (e.g. industrial and municipal outfalls) may produce ecological impacts at distant locations if pollutants affect dispersive propagules. We used laboratory experiments to determine how water-column exposure to produced water (=the aqueous fraction of oil and gas production that is typically discharged into coastal waters) influences the colonization potential of giant kelp (Macrocystis pyrifera) zoospores on the bottom. Zoospores were maintained in suspension at relatively low densities in 18-liter containers and exposed to one of five concentrations of produced water for varying amounts of time. Zoospore swimming generally decreased with increasing produced-water concentration and exposure duration; however, the specific pattern of decrease differed between experimental trials done on different dates. The effect of exposure duration on the ability of swimming zoospores to attach to plastic dishes placed on the bottom varied with produced-water concentration. Zoospores placed in produced-water concentrations of 1 and 10% showed a steady decline in their ability to attach with increased exposure; lower concentrations of produced water had no such effects. The percentage of zoospores that germinated after attachment varied tremendously with exposure duration and date of experimental trial. Zoospores that settled during the first 12 h after release had very poor rates of germination, indicative of a short precompetent period. Surprisingly, exposure of suspended zoospores to high concentrations of produced water during the first 12 h reduced this precompetent period and greatly improved germination success on the bottom. The magnitude of this enhancement, however, varied among dates. The results suggest that adverse effects of discharging produced water on planktonic zoospores of giant kelp would most likely be limited to the immediate vicinity of the outfall.

Response of embryos of the sea urchin Strongylocentrotus purpuratus to aqueous petroleum waste includes the expression of a high molecular weight glycoprotein

The present study investigated the sublethal effects of the largest aqueous waste associated with offshore oil development, produced water (PW), on sea urchin embryo development. PW inhibited normal gastrulation in purple sea urchin (Strongylocentrotus purpuratus) embryos exposed at the hatching stage. The exposed embryos did not form complete archenterons, and secondary mesenchyme cells exhibited an unusual behavior with respect to the wall of the blastocoelic cavity. In addition, an abundance of extracellular matrix was observed in the blastocoelic cavities in the embryos exposed to higher concentrations of PW. An inhibition of the development of embryos through the pluteus stage was observed as a result of PW exposure. This was manifested by inhibition of normal spicule formation with concomitant abnormal pluteus morphology. To determine if a biochemical stress response occurs as a result of PW exposure, embryos at the early gastrula stage were exposed to PW for 2 h, followed by an additional 1 h in 3H-leucine and PW. These embryos expressed a 253 kDa protein as observed by one-dimensional SDS (sodium dodecyl sulfate) polyacrylamide gel electrophoresis and autoradiography. This protein could occasionally be observed in gels stained for protein, and was glycosylated as demonstrated by staining with periodic acid Schiff (PAS). The 70 to 73 kDa heat-shock proteins previously described in sea urchin embryos (and other organisms) as a result of stress were not synthesized as a result of PW exposure. Heat shock did not induce synthesis of the 253 kDa glycoprotein. Combined PW and heat-shock exposure elicited both the heat-shock response (73 kDa protein) as well as expression of the 253 kDa glycoprotein. These data demonstrate the use of expression of endogenous macromolecular markers to distinguish exposures of embryos to different perturbations. Arsenic (as sodium arsenite), a metal constituent of PW, also induced the 253 kDa glycoprotein in early gastrula-stage embryos. We suggest that this glycoprotein may be a marker for PW (and a metal constituent) exposure in sea urchin embryos, and may be related to morphological abnormalities.