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Abstract
Standard tracer techniques, known from work with radioactive tracers and fluorescent dyes, have been applied for full scale studies of the distribution of oil in the water column. The study was part of oil spill experiments conducted off the cost of Norway in June 1985 under the research program 'Dispersion of Oil on Sea'. Light scattering of oil droplets in water and UV-fluorescence of dissolved oil components were used for in-situ detection of oil in water. By UV-fluorescence measurements, being the more sensitive of the two methods, it was demonstrated that dissolved components of oil were present 15 m below the slick less than one hour after the surface release of 10 tonnes of Statfjord crude oil (premixed with 2% dispersant). By tracking a submerged UV-fluorimeter through the elongated oil patch it was found that the maximum concentration of dissolved components occurred below the central part of the slick. It was experienced that in-situ UV-fluorimeter recordings provide detailed information on the relative distribution of dissolved oil compounds in the water column below a slick. By laboratory calibration of the UV-fluorimeter it is possible to establish a reliable estimate on the physical dilution of the released oil within a working range of 5 to about 10,000 μl m-3 oil in water. However, at the present state of work, the working range is only tested on oil with a residence time of less than six hours in sea water

Abstract
Conidiospores of the insect-pathogenic fungus Beauveria bassiana caused lethal and sublethal damage to embryos of Menidia beryllina. However, conidiosposer treated with a dispersant (0.03% concentration of Triton X-100) showed significantly less binding to embryos, which in turn caused fewer adverse effects

Abstract
In September 1960 a spillage of fuel oil occurred from the Marine terminal of the Esso oil refinery at Fawley, England. The oil-polluted mudflats at the mouth of the River Hamble contained large populations of the common intertidal polychaetes, C. tentaculata and C. cirratus. Quantitative studies on C. tentaculata at Hamble Spit showed that its spawning, growth and mortality were unaffected by the presence of oil. Semi-quantitative observations on the Spit population of C. cirratus showed it to be similarly unaffected. The reasons for the ineffectiveness of the oil in disrupting the life processes of the worms were discussed. On mudflats at Hamble village and Warsash where Essolvene dispersant was used to remove oil from boats and shore installations, a drop in numbers of both species of worm occurred. Toxicity tests using Essolvene and BP 1002 showed that both ssp were killed by relatively low concentrations of dispersant, although C. cirratus was the more tolerant. BP 1002 was the most toxic of the two dispersants. The populations at Hamble village and Warsash showed signs of recovery 2 yrs after pollution, with C. tentaculata recolonizing less rapidly than C. cirratus. Laboratory tests showed a new dispersant, Corexit 7664, to be several orders of magnitude less toxic than Essolvene and BP 1002, although all 3 dispersants prevented gamete formation in C. cirratus at concentrations approaching the lethal level

Abstract
When oil is spilled into aquatic systems, chemical dispersants frequently are applied to enhance emulsification and biological availability. In this study, a mammalian model system was used to determine the effect of Bonnie Light Nigerian crude oil, weathered for 2 d with continuous spraying and recirculation, and a widely used dispersant, Corexit (Cx) 9527, on intestinal microbial metabolism and associated populations. To determine the subchronic dose, concentrated or diluted (1:2, 1:5, 1:10, 1:20) Cx9527 or oil was administered by gavage to Fischer 344 rats and the effect on body weight was determined. Next, rats were treated for 5 wk with oil, dispersant, or dispersant + oil. Body and tissue weights, urine mutagenicity, and the impact on the intestinal microflora and three microbial intestinal enzymes linked to bioactivation were determined in the small and large intestines and cecum. Two tested dispersants, Cx9527 and Cx9500, were toxic in vitro (1:1000 dilution), and oil was not mutagenic in strains TA98 and TA100(+/-S9). None of the treated rats produced urine mutagens detected by TA98 or TA100. Undiluted dispersant was lethal to rats, and weight changes were observed depending on the dilution, whereas oil generally was not toxic. In the 5-wk study, body and tissue weights were unaffected at the doses administered. Small-intestinal levels of azoreductase (AR), β-glucuronidase (BG), and nitroreductase (NR) were considerably lower than cecal and largeintestinal activities at the same time point. A temporal increase in AR activity was observed in control animals in the 3 tissues examined, and large-intestinal BG activity was elevated in 3-wk controls. No significant changes in cecal BG activity were observed. Oil- or dispersant-treated rats had mixed results with reduced activity at 3 wk and elevated activity at 5 wk compared to controls. However, when the dispersant was combined with oil at 3 wk, a reduction in activity was observed that was similar to that of dispersant alone. One-week nitroreductase activity in the small intestine and cecum was unaffected in the three treatment groups, but elevated activity was observed in the large intestines of animals treated with oil or dispersant. The effect of the combination dose was not significantly different from the control value. Due to experimental error, no 3- or 5-wk NR data were available. By 5 wk of treatment, enterobacteria and enterococci were eliminated from ceca of oil-treated rats. When oil was administered in combination with dispersant, an apparent protective effect was observed on the enterococci and lactose-fermenting and nonfermenting enterobacteria. A more detailed analysis at the species level revealed qualitative differences dependent on the treatment. This study suggests that prolonged exposure of mammals to oil, dispersant, or in combination impacts intestinal metabolism, which ultimately could lead to altered detoxification of oil constituents and coexposed toxicants

Abstract
Corexit 9527, Corexit 9500, and Corexit 9580 have low (LC50 or EC50 > 100 ppm) to moderate (LC50 or EC50 ≥ 1 to 100 ppm) toxicity to most aquatic organisms in laboratory tests; however, the experimental species, temperature, and exposure duration can significantly affect measurements of toxicity. Field and laboratory studies indicate that 4-hour toxicity test data are more reflective of actual dispersant use conditions

Abstract
The acute toxicities of a commercial dispersant (Corexit 9527) and four experimental dispersant formulations were evaluated using the 96-h mysid (Mysidopsis bahia) test and two rapid screening tests, Microtox and the Mysid IQ Toxicity Test. During 96-h toxicity tests, survival observations were recorded at 3, 6, 9, 12, and 24 h to document mortalities from short-term exposures more consistent with field exposure times and more approximate to exposure times used in Microtox and the Mysid IQ Toxicity Test. At nominal concentrations (6.25 and 12.5 mg/liter) and exposure times (3–24 h) near the upper range of predicted field conditions, mysid mortalities were ≤5% for all test materials. Microtox and Mysid IQ Toxicity Test were evaluated for their ability to differentiate test materials compared with that of the 96-h mysid test. Dispersant formulations were ranked by relative toxicities based on LC50or EC50 values and ranks compared among test methods. Microtox ranked the test materials similar to the 96-h mysid test. Ranks from the Mysid IQ Toxicity Test were dissimilar to those of the other tests. Early mortality observations during 96-h tests did not provide a better basis for comparing results of the rapid screening tests

Abstract
The oil spill dispersants, Corexit® 9500 and Corexit® 9527 have low to moderate toxicity to most aquatic species in laboratory tests. Toxicity estimates are significantly affected by test variables such as species, lifestage, exposure duration, and temperature. Aquatic toxicity data generated from spiked, declining exposures (107 min half-life) are more reflective of actual dispersant use conditions. Decisions to use oil spill response chemicals should not be based solely on aquatic toxicity. Factors to consider include product effectiveness, toxicity of dispersed oil, species/habitats requiring priority protection, and recovery potential of sensitive habitats and populations. An environmental risk assessment approach is recommended where dispersant toxicity data generated under environmentally relevant exposures are compared to estimated environmental concentrations of dispersants

Abstract
Recent inland spills in Latin America have generated interest in dispersant use for freshwater oil spills. However, oil spill dispersants primarily are formulated for use in marine waters. Dispersants that are designed for saltwater use show reduced effectiveness when applied in freshwater. The effectiveness of COREXIT® 9500 in low salinity waters varies with the type of oil, the dispersant-to-oil ratio (DOR), and other factors. The effectiveness of COREXIT® 9500 can decrease markedly at salinities of 15 ppt or less. The authors observed an increase in effectiveness of COREXIT® 9500 in freshwater when the dispersant was blended with an inorganic, divalent salt, such as calcium chloride, prior to use (patent pending). COREXIT® 9500* refers here to the blend of the salt and dispersant. The Exxon Dispersant Effectiveness Test (EXDET) was used to evaluate dispersant performance in deionized water and in river water samples from Rio de la Plata, Argentina. COREXIT® 9500 showed 22% effectiveness on Alaska North Slope (ANS) crude oil in deionized water, a value indicative of poor effectiveness. Depending on the amount of calcium chloride added, COREXIT® 9500* showed up to 63% effectiveness on ANS crude oil in deionized water, which indicates good effectiveness. The effectiveness of COREXIT® 9500* and COREXIT® 9500 was compared for three additional crude oils both in deionized water and in river water. In all cases, the effectiveness of COREXIT® 9500 was lower compared with COREXIT® 9500*

Abstract
The present study examines the impact of exposure to oil-derived products on the behaviour and physiology of the Australian 11-armed asteroid Coscinasterias muricata. Asteroids were exposed to dilutions of water-accommodated fraction (WAF) of Bass Strait stabilised crude oil, dispersed oil or burnt oil (n=8) for 4 days whereby, prey-localisation behaviour was examined immediately after exposure, and following 2, 7, and 14 days depuration in clean seawater. The prey-localisation behaviour of asteroids exposed to WAF and dispersed oil was significantly affected though recovery was apparent following 7 and 14 days depuration, respectively. In contrast, there was no significant change in the prey-localisation behaviour of asteroids exposed to burnt oil. Behavioural impacts were correlated with the total petroleum hydrocarbon concentrations (C6–C36) in each exposure solution, WAF (1.8 mg l-1), dispersed oil (3.5 mg l-1) and burnt oil (1.14 mg l-1), respectively. The total microsomal cytochrome P450 content was significantly lower (PDunnett test

Abstract
An experimental approach was developed and applied for testing the effects of oil and dispersant combinations on the growth of mangrove seedlings (trees of the intertidal tropics). A controlled growth chamber was employed to test the effects of different oils and dispersed oils in an array of dosages applied to different parts of the plants. Preliminary test results are reported for two species of mangroves collected from five localities, including both oiled and unoiled estuaries. Differences occurred between species, substances, dosages, the part of the plant dosed, and the presence of chronic oil pollution at localities from which the stocks were collected. Avicennia germinans (L.) L. (black mangrove) was more sensitive than Rhizophora mangle L. (red mangrove) when exposed to almost all substances tested. Light Arabian crude oil (LA) and light Arabian crude oil dispersed (LAD) were the most toxic substances tested. No. 2 fuel oil (N2) and No.2 fuel oil dispersed (N2D) were as toxic as LA and LAD, except for an increase (an enhancement effect) in foliage and stem growth in Avicennia at lower dosages. Bunker C oil (BC) was the least toxic of the oils tested, resulting in the reduction of foliage and stem growth only at the highest dosage tested in Avicennia. Bunker C oil dispersed (BCD) failed to show effects in either species at any dosage tested. The leaves of Rhizophora were the most sensitive part of the plant tested. Root-dosing had a lesser effect than leaf-dosing but resulted in greater effects with LAD than with any other substance tested. Seedling stock from chronically oiled areas sprouted more rapidly and developed more foliage in response to LA, indicating a possible “preadaptation” to spilled oil; no such effect occurred when dispersant was added to LA. The response of mangroves was specific to the oil type to which the dispersant was added. Dispersant increased the toxicity of LA and N2 but decreased the toxicity of BC

Abstract
Relatively few data exist on the effects of oil and dispersing agents on tropical wetlands. This is true despite extensive nearshore and onshore drilling, onshore refining, and transportation of oil through the past decade in tropical areas of the world. This paper reports on preliminary results from a laboratory experiment on the toxicity of oil and dispersants to mangroves (tropical marine forests). A controlled-growth chamber with regulated light, temperature, and humidity was used to monitor growth and stress responses. Seedlings of the mangrove genera Rhizophora and Avicennia were selected for study since they represent species found growing along most oil-sensitive, tropical shorelines. Mangrove seedlings were treated with three oil types (bunker C, No. 2 fuel oil, and light Arabian crude), both with and without a dispersant concentrate added. The plants were dosed with oil at 25, 50, 500, 5,000, and 50,000 parts per million; dispersant concentrates were added as a well-mixed, unweathered dilution with oil in a 1:22 ratio. From these results, preliminary conclusions are drawn regarding the differential response of mangrove species, different oil and dispersant combinations, and the difference in response to oil and dispersants by stocks of mangroves from chronically oiled environments

Abstract
Field experiments were conducted to determine the effects of oil and dispersant on red mangroves (Rhizophora mangle). Two experimental sites were chosen on the basis of their biological and physical similarity and treated with either undispersed Prudhoe Bay crude oil or with Prudhoe Bay crude and dispersant Corexit 9527. Short- and long-term effects on biota were monitored to determine the effects of using dispersants on spilled oil on mangrove forests. Significant differences were noted in effects on seedling and adult mangroves, most notably in survival and growth of adults. Addition of dispersant to crude oil greatly increased its mobility in the water column, and decreased its residence time in the intertidal zone. Retention of oil within the mangrove forest was the primary factor in controlling impacts to mangroves, and dispersants appeared to greatly reduce the amount of oil retained in the intertidal zone of the mangrove forest. Additional research is underway to investigate the impact of dispersed oil in the subtidal communities associated with mangrove forests

Abstract
The results of a long-term program to determine the effects of oil and dispersant on red mangroves and black mangroves are presented. Laboratory experiments were conducted to determine the effects of three oils and dispersant on juvenile red mangroves and black mangroves. A field experiment was conducted to determine the effects of a crude oil and dispersant on a mature mangrove forest in Panama. Our studies indicate that exposure of mangrove seedlings to oil and dispersant in the laboratory resulted in changes of growth, respiration, and transpiration, and led to uptake of petroleum hydrocarbons. Exposure of a mature red mangrove forest to oil and dispersant resulted in many of the same effects observed in the laboratory and at other oil spill sites. These effects were greatly reduced at the site treated with oil and dispersant when compared to the site treated with whole oil

Abstract
Research Planning Institute, Inc. (RPI) and Bermuda Biological Station for Research, Inc. (BBS) have implemented a long-term program of research on the fate and effects of oil spills and dispersants on coastal tropical areas. Tropical Oil Pollution Investigations in Coastal Systems (TROPICS) is an integrated study to allow examination of possible tradeoffs of impacts between intertidal and subtidal tropical ecosystems and to establish whether the application of dispersants to spilled oil in nearshore tropical areas is an ecologically safe means of minimizing damages to these habitats. Baseline studies have been conducted at selected field sites to characterize and measure biological, chemical, and physical parameters prior to experimental spills. The fate and effects of dispersed and undispersed oil in the nearshore tropical ecosystem are being monitored for one year after the experimental treatments. Detailed measurements are being made of the mangroves and sea grasses to determine effects on primary productivity, growth, general condition, and survival. Infauna and epifauna are being monitored to estimate changes in density and diversity, and motile macrofauna are being observed to determine changes in distribution and behavior. Corals are being measured to determine changes in growth, abundance, and coverage; and the infauna, epifauna, and resident fish communities are being monitored as well. The water column, sediments, and biota are being monitored chemically using discrete and flowthrough pumping techniques, large-volume extraction techniques, replicate sediment cores, and tissue samples of dominant biota. Samples are being analyzed using ultraviolet fluorometry (UV), gas chromatography (GC), and GC/mass spectrometry

Abstract
On August 19, 1981, two test spills of Murban crude oil were carried out in Long Cove, Searsport, Maine. One spill was chemically dispersed; the other was not. Measurements were made to make quantitative comparisons of the chemical fates and biological effects of the two spills. Hydrocarbon analyses were carried out on water samples, animal tissue samples, intertidal sediment samples, and subtidal sediment samples. Biological measurements were carried out at the community level, whole animal level, and biochemical level of organization. No significant biological effects attributable to the dispersed oil spill were observed. This lack of effect is, in part, a result of changes in the physical and chemical properties of dispersed oil which help limit its availability and toxicity. The chemical fate and biological effects of the undispersed oil spill were typical of those reported from actual oil spill sites. Oil was incorporated into sediments and animal tissue. On the community level of organization mortality, reduced diversity and evenness, increased population density, and increased dominance by opportunists were all observed immediately after the spill, and up to 1 year later. On the whole animal level of organization, no effects on scope-for-growth were observed in two filter feeding bivalves. On the biochemical level of organization, activities of two sensitive enzyme systems were elevated

Abstract
The effect of two nearshore discharges of Murban crude oil on community structure in intertidal benthic communities was studied. One discharge consisted of 250 gallons of Murban crude only. Following the discharge, no measurable amount of Murban crude could be found in sediments exposed to the cloud of dispersed oil. Significant amounts were found in the test plot exposed to untreated oil. In the area exposed to untreated oil, more oil was found in the upper intertidal zone than lower down. Effects on infaunal communities mirrored the analytical results. There was no evidence of adverse effects on infaunal community structure from exposure to dispersed oil. There is clear evidence that exposure to untreated oil did adversely affect community structure. Some indigenous species were reduced in number or eliminated; there were blooms of opportunistic polychaetes. The changes in community structure brought about by the untreated oil are consistent with results observed at real-world oil spill sites

Abstract
In 1981, two test oil spills were made in Maine. One spill was 975 L (250 gal) of Murban crude oil; the other was 975 L of Murban crude oil premixed with 97 L (25 gal) of Corexit© 9527. The uptake of the oil and its effects on enzymatic activity in two species of common intertidal bivalve mollusks, Mya arenaria and Mytilus edulis, were studied. Data were obtained on uptake and depuration of the oil for each species; data were also obtained on the activity of glucose-6-phosphate dehydrogenase and aspartate aminotransferase for each species. Data were collected both before and after each of the spills. Much less oil was taken up by the animals exposed to chemically dispersed oil than by those exposed to nondispersed oil. Rates of depuration were the same for each species; they were also the same regardless of oil exposure. Significant long-term effects on enzyme activity were detected only in those animals exposed to nondispersed oil

Abstract
As provided by the Canadian Shipping Act, the marine emergency office of the Canadian Coast Guard (CCG) is responsible for providing maritime emergency countermeasures operations that in peace time are not furnished by the private sector. With respect to oil spill countermeasures, the Canadian Coast Guard has pursued an equipment acquisition programme that involves recovery hardware, tanker lightening machinery, and dispersant spraying equipment. In developing a national dispersant spraying capability, the CCG has undertaken a modification programme to enable the conventional offshore spraying gear to be mounted on almost any vessel of convenience. Smaller, more versatile inshore spraying vessels and pumps have been designed and built. With the popularization of concentrated dispersants, the inshore pumping equipment can be used aboard hovercraft for special application situations. A programme of acquiring mobile dispersant storage tanks has been undertaken with auxiliary equipment that will facilitate the shipment of dispersants in bulk by air freight. Work also has commenced on extending the dispersant application programme to include the CCG fleet of helicopters

Abstract
During the summer of ’75 and the winter of ’76, the Canadian Coast Guard Marine Emergency Organization conducted field trials on a number of commercial oil dispersants using the Warren Spring type of testing apparatus. These field trials, as part of an ongoing programme, were undertaken to gain a better appreciation of the effectiveness of dispersants in both warm and cold water. The results of tests conducted on the five products reported hereunder indicate that the new concentrates represent a considerable improvement over the more conventional oil dispersants with the implication of improved application logistics. Data obtained from the work dine in colder weather suggests that oil dispersant performance deteriorates somewhat under colder conditions

Abstract
During the summer of 1977, modifications were made to the Canadian Coast Guard Voyageur hovercraft for preliminary studies to determine whether this vehicle, and possibly hovercraft in general, could be considered as potential platforms for oil spill dispersant spraying. Work to date indicates that air turbulence resulting from underskirt escapage, propeller wash, and forward velocity does not represent an obstacle that would deter the use of these vehicles as dispersant spraying platforms

Abstract
The Canadian Offshore Aerial Application Task Force (COAATF) was convened in 1979 to conduct laboratory and field studies on the practical effectiveness of the aerial application of oil spill dispersant concentrates under Canadian environmental conditions. Several studies undertaken by COAATF are briefly reviewed with regard to their contribution towards this objective

Abstract
In September 1983, the Canadian Offshore Aerial Applications Task Force conducted a 3-day oil spill dispersant field trial using the commercial products Corexit 9527, Corexit 9550, and BPMA 70. A different dispersant concentrate was applied each day to one of two 15 barrel spills of 13 percent weathered Alberta crude oil using a Bell 212 transported Rotortech TC-3 spraying bucket. Both treated and control slicks were surveyed using remote sensing aircraft to determine surface area, spreading rates, and major differences in slick thickness. A water sampling program was undertaken to determine the extent of dispersant effectiveness. Sea conditions during the first two days’ work (9527 then 9550) were comparable with a moderate increase in mixing energy on the third day (BPMA 700). Against these conditions, and with corresponding dispersant to oil ratios of 1:27, 1:8, and 1:9, the percentage of weathered oil dispersed into the water column was calculated to be 3.75, 20.5 and 41 respectively

Abstract
This paper describes both the Warren Spring Laboratory (WSL) and Institut-Français du Pétrole (IFP) tests, noting that there is no apparent correlation between the test methods, due to their different designs. It is stressed that dispersants should be tested in different conditions, because effectiveness varies by the function of the test design being used

Abstract
An oil spill–food chain interaction model, composed of a multiphase oil spill model (MOSM) and a food chain model, has been developed to assess the probable impacts of oil spills on several key marine organisms (phytoplankton, zooplankton, small fish, large fish and benthic invertebrates). The MOSM predicts oil slick thickness on the water surface; dissolved, emulsified and particulate oil concentrations in the water column; and dissolved and particulate oil concentrations in bed sediments. This model is used to predict the fate of oil spills and transport with respect to specific organic compounds, while the food chain model addresses the uptake of toxicant by marine organisms. The oil spill–food chain interaction model can be used to assess the environmental impacts of oil spills in marine ecosystems. The model is applied to the recent Evoikos–Orapin Global oil spill that occurred in the Singapore Strait

Abstract
An experimental program to test the effectiveness of dispersants in an open-ocean, cold-water environment was conducted off St. John’s, Newfoundland in the fall of 1981. The dispersion of Lago Medio oil by Corexit© 9527 was investigated by using surface and subsurface sampling techniques combined with remote sensing which employed infrared (IR), ultraviolet (UV), and visual sensors to define the surface slick and show the position of the sampling vessels within the slick. Infrared photography was used to estimate the area of the thick slick because IR “coolness” (darker gray level) appears to be indicative of thicker oil. The total extent of the slick was determined from the reflectance in the UV region. Both photographic and line-scanning imagery was used in the UV, and a line scanner in the IR. Measurements were taken from a height of 500 to 800 m every 20 min of both a control slick and a slick to which dispersant had been applied from the air. A comparison of the two slicks shows a difference in the dynamics and gives some indication of the nature of the dispersion process. Problems with sampling and determination of hydrocarbons in the water column prevented the comparison of remote sensing results with those from water column chemistry. As a result of these experiments, it is shown that remote sensing can be used to obtain quantitative data on the spreading characteristics of an oil slick and hence changes in interfacial tension that effect dispersion as well as spreading. This technique has the potential to measure the effectiveness of a dispersant without the need for an extensive water sampling program

Abstract
This paper describes the development of a simple remote sensing system for the detection of oil on water. Signals from sensors operating in the ultraviolet and infrared are combined in a computer-based image processing system to produce information on the area of thick and thin portions of the slick, from which the effectiveness of dispersants can be calculated. The design parameters, the selection of sensors, and the integration of these sensor signals into a user friendly display is discussed. The use of this UV/IR system in field oil spill experiments and in an actual spill situation is described