Oil Spill Dispersants Efficacy and Effects (2005) / Chapter Skim
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5 Toxicological Effects of Dispersants and Dispersed Oil
5 Toxicological Effects of Dispersants and Dispersed Oil
Pages 193-276
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From page 193... ...
Comparing the possible ecological consequences and toxicological impacts of these trade-offs is difficult. First, each oil spill represents a unique situation and second, it is often difficult to extrapolate from published research data into field predictions, especially regarding the possibility of longterm, sublethal toxicological impacts to resident species (Box 5-1 provides definitions for most the common terms used in discussions of toxicological effects)
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From page 194... ...
For example, the protection of sensitive habitats, such as tropical coral reefs and mangroves, is a priority in oil spill response decisions. Many studies have shown that oil, floating above subtidal reefs, has no adverse effects on the coral; however, if allowed to reach the shoreline, the oil may have long-term impacts to a nearby mangrove system.
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From page 195... ...
Exposures: Concentration of dis persant sample is highest at start and then declines to non-detectable levels after 68 hr using a flow-through exposures protocol developed by Chemi cal Response to Oil Spills Environmental Research Forum (CROSERF) par ticipants.
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From page 196... ...
This chapter reviews recent laboratory, mesocosm, and field studies on the toxicological effects of dispersants and dispersed oil, particularly those published since the 1989 NRC report on oil dispersants (NRC, 1989)
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From page 197... ...
Consequently, the majority of ecological risk assessments of environmental chemicals are still based on species-specific tests of toxicological effects on individual organisms. Until population and community-level approaches are more widely accepted and utilized in ecotoxicology, evaluations re garding the impacts of oil spills will remain largely based on qualitative assessments and best professional judgment.
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From page 198... ...
The choice of test duration alone can significantly overestimate or underestimate toxicity depending on the actual oil spill situation being simulated. The choice of response parameters measured in a test can be significant as well.
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From page 199... ...
, was organized to coordinate and disseminate research on oil spill dispersant use. CROSERF developed toxicity test protocols involving spiked exposures of shorter durations and standardized preparations of water accommodated fractions (WAF)
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From page 200... ...
recommended as concentration endpoint Exposure regime 48 or 96 h tests in sealed vessels; static-renewal exposures for duration of test, aeration discouraged; flow-through "spiked exposures" with concentrations decreasing to non detectable levels in <8 h Test maintenance Renew solutions at unspecified intervals for static renewal tests, removing dead organisms; dead organisms not removed in flow-through exposures; feeding as specified for test species, with food amount adjusted for loss of test organisms
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From page 201... ...
. cWAF=Water accommodated fraction; CEWAF=Chemically enhaced WAF, or chemically dispersed oil; stir bar size 12 in as appropriate.
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From page 202... ...
(2001a) argue for the variable loading method because they believe it is more "field relevant" since spilled oil slicks tend to be dynamic, continu Variable Loading Variable ratio of toxic components WAF 2 WAF 1 WAF 3 Variable Dilution Same ratio of toxic components WAF 1 WAF 3 WAF 2 FIGURE 5-1 Comparison of variable loading and variable dilution methods of preparing toxicity test solutions.
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From page 203... ...
However, if chemical analyses were limited to stock solutions, inaccuracies may occur due to differential partitioning in the test dilutions, adsorption of compounds onto test chambers, or loss to the gaseous phase. The interpretation of the results of toxicity tests can be significantly affected by the method of WAF and CEWAF preparation because of the variable solubilities of the many components in oil.
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From page 204... ...
However other temperate zone oil spills (French-McCay, 1998) , especially subarctic spills (Neff and Burns, 1996; Short and Harris, 1996)
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From page 205... ...
Species were exposed to fresh Forties crude oil and Corexit 9500, except for topsmelt, which were exposed to fresh Prudhoe Bay crude oil, and kelp mysid, which were exposed to fresh Kuwait crude oil and Corexit 9527. LC50s for spiked exposures were based on the initial total petroleum hydrocarbon concentration of the CEWAF.
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From page 206... ...
Photoenhanced toxicity is another factor that has not been adequately considered in dispersant and dispersed oil toxicity testing under either CROSERF or non-CROSERF protocols. The toxicity of oil dispersed in water has been shown in some studies to be many times higher in the presence of the ultraviolet radiation from sunlight, yet to date only a single study has examined the photoenhanced toxicity of chemically dispersed oil (Barron et al., 2004)
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From page 207... ...
. However, the previous NRC report concluded that the acute lethal toxicity of chemically dispersed oil is primarily associated not with the current generation of dispersants but with the dispersed oil and dissolved oil constituents following dispersion (NRC, 1989)
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From page 208... ...
Prawn Penaeus monodon 96 LC 5 0 Shrimp Penaeus vannemai 96 LC 5 0 White shrimp (postlarvae) , F Penaeus setiferus 96 LC 5 0 Gulf mysid Mysidopsis bahia 96 LC 5 0 Gulf mysid Mysidopsis bahia 48 LC 5 0 Gulf mysid Mysidopsis bahia SD LC 50 Kelp forest mysid, F Holmesimysis costata 96 LC 5 0 Kelp forest mysid, F Holmesimysis costata SD LC 50 Kelp forest mysid, F Holmesimysis costata 96 LC 5 0 Kelp forest mysid, F Holmesimysis costata SD LC 50 Kelp forest mysid Holmesimysis costata 96 LC 5 0 Blue crab (larvae)
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From page 209... ...
209 TOXICOLOGICAL EFFECTS OF DISPERSANTS AND DISPERSED OIL Effect Concentration (ppm) References 230 f Mitchell and Holdaway (2000)
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From page 210... ...
Menidia beryllina 96 LC 5 0 Red drum (embryo-larval) , F Sciaenops ocellatus 48 LC 5 0 Sheepshead minnow Cyprinodon variegatus 96 LC 5 0 Atlantic menhaden Brevoortia tyrannus 48 LC 5 0 (embryo-larval)
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From page 211... ...
211 TOXICOLOGICAL EFFECTS OF DISPERSANTS AND DISPERSED OIL Effect Concentration (ppm) References ca.
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From page 212... ...
Cnidarians Green Hydra Hydra viridissima 96 LC 5 0 Green Hydra Hydra viridissima 168 NOEC Crustaceans Amphipod, F Allorchestes compressa 96 LC 5 0 Brine shrimp Artemia salina 48 LC 5 0 White shrimp, F Palaemonetes varians 6 L C 50 Ghost shrimp Palaemon serenus 96 LC 5 0 Gulf mysid Mysidopsis bahia 48 LC 5 0 Gulf mysid Mysidopsis bahia 96 LC 5 0 Gulf mysid Mysidopsis bahia SD LC 50 Copepod (adult) Eurytemora affinis 96 LC 5 0 Kelp forest mysid, F Holmesimysis costata SD LC 50 Kelp forest mysid, F Holmesimysis costata SD NOEC Prawn (larval)
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From page 213... ...
213 TOXICOLOGICAL EFFECTS OF DISPERSANTS AND DISPERSED OIL Effect Concentration (ppm) References 160 f Mitchell and Holdaway (2000)
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From page 214... ...
, and dispersants using either fresh crude oil (Kuwait, Forties, Prudhoe Bay, and Venezuela) , weathered-crude oil (Arabian medium)
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From page 215... ...
The purpose of chemical dispersants is to facilitate the movement of oil into the water column. The result is a complex, multi-phase mixture composed of dissolved dispersant, dissolved petroleum hydrocarbons, oil/dispersant droplets, and bulk, undispersed oil.
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From page 216... ...
. Rather than review these findings, the purpose here is to focus on the issues that are pertinent to understanding the bioavailability and toxicity of chemically dispersed oil.
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From page 217... ...
(2004) exposed juvenile rainbow trout to chemically dispersed oil and WAF using Corexit 9500 and Mesa crude oil and then used epifluorescence1 to microscopically observe PAH uptake in the fish gills.
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From page 218... ...
The limited information available suggests that fairly high oil and SPM concentrations are required before chemically dispersed oil interacts with SPM, and that chemically dispersed oil has a much lower tendency to form SPM agglomerates compared to physically dispersed oil. Aquatic organisms may also be exposed to oil due to contamination of their food.
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From page 219... ...
Regardless of their Type I or Type II classification, all organic chemicals in a field mixture contribute to toxicity by narcosis (Deneer et al., 1988) ; therefore, mixtures of organic chemicals, such as found during an oil spill, would be expected to exhibit additive toxicity over a range of composition ratios (van Wezel et al., 1996)
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From page 220... ...
220 OIL SPILL DISPERSANTS 900 800 A 700 600 mg/kg 500 400 300 200 100 0 F/P1 F/P3 P/A1 P/A3 BAP BP IP C2 C4 D2 N2 N4 BK AE FL F2 A C D N F 16000 14000 B 12000 10000 ng/L 8000 6000 4000 2000 0 F/P1 F/P3 P/A1 P/A3 BAP BP IP N2 N4 D2 C2 C4 AE BK F2 FL N D C F A 100000 C 80000 60000 ng/L 40000 20000 0 F/P1 F/P3 P/A1 P/A3 BAP BP IP C2 C4 N2 N4 D2 AE BK F2 FL C N D F A 6000 5000 D 4000 ug/Kg 3000 2000 1000 0 F/P1 F/P3 P/A1 P/A3 BAP BP IP D2 N2 N4 C2 C4 AE BK F2 FL D N C F A 12 E 10 8 ug/Kg 6 4 2 0 F/P1 F/P3 P/A1 P/A3 BAP BP IP N2 N4 C2 C4 D2 AE BK F2 FL N C D F A FIGURE 5-4 PAH histograms for: (A) mixed M/V New Carissa source oil "blend" (ET-2)
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From page 221... ...
221 TOXICOLOGICAL EFFECTS OF DISPERSANTS AND DISPERSED OIL Analytes Abbreviation Naphthalene N C1-Naphthalenes N1 C2-Naphthalenes N2 C3-Naphthalenes N3 C4-Naphthalenes N4 Biphenyl BI Acenaphthylene AC Acenaphthene AE Fluorene F C1-Fluorenes F1 C2-Fluorenes F2 C3-Fluorenes F3 Anthracene A Phenanthrene P C1-Phenanthrene/Anthracenes P/A1 C2-Phenanthrene/Anthracenes P/A2 C3-Phenanthrene/Anthracenes P/A3 C4-Phenanthrene/Anthracenes P/A4 Dibenzothiophene D C1-Dibenzothiophenes D1 C2-Dibenzothiophenes D2 C3-Dibenzothiophenes D3 Fluoranthene FL Pyrene PYR C1-Fluoranthene/Pyrenes F/P1 C2-Fluoranthene/Pyrenes F/P2 C3-Fluoranthene/Pyrenes F/P3 Benzo(a) Anthracene BA Chrysene C C1-Chrysenes C1 C2-Chrysenes C2 C3-Chrysenes C3 C4-Chrysenes C4 Benzo(b)
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From page 222... ...
Nevertheless, more work needs to be done to link the additive compound-specific toxicity data with the component concentrations and mixtures within each hydrocarbon block or pseudocomponent. It should be noted that narcosis may not account for all the toxic effects due to exposure to oil or dispersed oil, particularly sublethal or longterm effects.
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From page 223... ...
Because dispersants generally increase the water-column concentrations of dissolved and particulate petroleum hydrocarbons (including the photoactive compounds) relative to undispersed oil, photoenhanced toxicity of some PAH is an important consideration for evaluating toxicity associ
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From page 224... ...
(2002) found that the toxicity of weathered Alaska North Slope crude oil for two calanoid copepod species was dramatically increased upon exposure of the copepods to natural sunlight.
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From page 225... ...
However, this approach has limited utility in evaluating the relative toxicity of chemically dispersed versus untreated oil based on exposure to oil in the water column. The degree to which a dispersant facilitates dissolution of petroleum hydrocarbons into the water column will influence the resulting degree of toxicity observed.
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From page 226... ...
In a series of tests, they evaluated the acute effects of untreated and dispersant-treated (Corexit 9527) Prudhoe Bay crude oil on early life stages of three Pacific marine species: red abalone, Haliotis rufescens, kelp forest mysid shrimp, Holmesimysis costata, and topsmelt, Atherinops affinis.
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From page 227... ...
were 48 hour exposures with Forties crude oil and Corexit 9500. Data expressed as LL imply that CEWAF is more toxic than WAF, but when expressed as measured TPH, toxicities are roughly equivalent.*
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From page 228... ...
(1994) in a series of tests comparing the toxicity of chemically dispersed oil, dispersant (Corexit 9527)
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From page 229... ...
In addition, application of additive toxicity models for PAH and other petroleum constituents may facilitate the interpretation of toxicity test results. Although acute toxicity studies do not indicate differences in the lethal or sublethal responses of organisms exposed to chemically dispersed or untreated oil, some studies have suggested that the bioaccumulation kinetics of PAH from dispersed oil may differ from those for undispersed oil.
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From page 230... ...
Depuration of phenanthrene by rotifers decreased significantly following dispersed oil exposures, while uptake and depuration of naphthalene by larval topsmelt significantly increased in both aqueous and dietary exposures to dispersed oil. These detailed and elegant experiments have enhanced our understanding of the bioaccumulation kinetics of dispersed oil PAH.
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From page 231... ...
, two dispersants (Corexit 9500 and 9527) , continuous and shortterm spiked exposures, and early life stages of several marine organisms in 46 and 96 hr tests found that physically dispersed oil appears less toxic than chemically dispersed oil when LC50s were expressed as nominal loading concentrations (see earlier in Chapter 5)
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From page 232... ...
Corexit 9500 96 static (60% daily renewal) Mysidopsis bahia Kuwait (1:10)
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From page 233... ...
mg/L Reference larval mortality NA 0.5 Initial TPH Clark et al., 2001 larval mortality NA 1.92 Initial TPH Clark et al., 2001 larval mortality NA 0.81 Initial TPH Clark et al., 2001 larval mortality NA 3.99 Initial TPH Clark et al., 2001 larval mortality >1.14 0.53 Initial TPH Clark et al., 2001 larval mortality >1.83 2.28 Initial TPH Clark et al., 2001 hatchling 0.51 3.11 Average TPH Long and Holdaway, mortality over 24 hr 2002 hatchling 0.39 1.8 Average TPH Long and Holdaway, mortality over 24 hr 2002 larval mortality NA 514 Initial Wu et al., 1997 nominal a larval mortality NA 48 Initial Wu et al., 1997 nominal a larval mortality NA 505 Initial Wu et al., 1997 nominal a larval mortality NA 71 Initial Wu et al., 1997 nominal a mortality 258,000 3.6 Initial nominal Gulec and Holdaway, 2000 mortality 258,000 8.1 Initial nominal Gulec and Holdaway, 2000 83.5b 1.1b mortality Initial nominal Unsal, 1991 mortality 311,000 16.2 Initial nominal Gulec et al., 1997 mortality 311,000 14.8 Initial nominal Gulec et al., 1997 mortality 0.63 0.65 Initial TPH Clark et al., 2001 mortality >2.93 17.2 Initial TPH Clark et al., 2001 mortality NA 0.11 Initial TPH Clark et al., 2001 continues
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From page 234... ...
Corexit 9527 96 spiked Mysidopsis bahia KCO (1:10) Corexit 9527 96 static daily renewal, sealed Holmesimysis costata Kuwait (1:10)
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From page 235... ...
5 9 0 . 8 9 10.218.1 Average TPH Wetzel and van Fleet, 2001 larval mortality >6.86 15.9 Average TPH Wetzel and van Fleet, 2001 larval mortality >0.63>0.83 72.6120.8 Average TPH Wetzel and van Fleet, 2001 mortality >2.9 17.7 Initial TPH Pace et al., 1995 mortality 0.78 0.98 Initial TPH Pace et al., 1995 mortality 0.1 0.17 Initial TPH Clark et al., 2001 mortality >2.76 1.8 Initial TPH Clark et al., 2001 Initial THCc Singer et al., 1998 juvenile >25.45 >34.68 10.5410.83 mortality Initial THCc early-life stage 14.23>17.5 9.4614.40 Singer et al., 2001 mortality Initial THCc early-life stage 0.951>1.03 5.7233.27 Singer et al., 2001 mortality mortality 0.7 9 Initial stock Mitchell and Holdaway, TPH 2000 mortality 0.7 7.2 Initial stock Mitchell and Holdaway, TPH 2000 larval mortality ~0.045 0.199 Initial tPAH Barron et al., 2004 continues
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From page 236... ...
Corexit 9500 96 continuous Menidia beryllina VCO (1:10) Corexit 9500 96 static (90% daily renewal)
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From page 237... ...
5 Initial TPH Fuller and Bonner, 2001 early life stage NA 20.28 Initial THC Singer et al., 2001 mortality larval mortality 26.36 12.22 Initial THC Rhoton et al., 2001 larval mortality 15.59 12.42 Initial THC Rhoton et al., 2001 larval mortality >19.86 12.29 Initial THC Rhoton et al., 2001 larval mortality 14.81 4.57 Initial THC Rhoton et al., 2001 larval mortality <0.11 0.68 Average TPH Wetzel and van Fleet, 2001 larval mortality 0.63 2.84 Average TPH Wetzel and van Fleet, 2001 larval mortality >6.86 18.1 Average TPH Wetzel and van Fleet, 2001 continues
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From page 238... ...
Corexit 9500 48 static, daily renewal Melanotaenia fluviatilis BSC (1:50) Corexit 9500 72 static, daily renewal Melanotaenia fluviatilis BSC (1:50)
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From page 239... ...
mg/L Reference larval mortality >1.06 30.8 Average TPH Wetzel and van Fleet, 2001 larval mortality 0.79 0.65 Initial THC Rhoton et al., 2001 larval mortality >1.13 18.89 Initial THC Rhoton et al., 2001 larval mortality 0.85 4.23 Average TPH Wetzel and van Fleet, 2001 larval mortality 465,000 14.1 Initial nominal Gulec and Holdaway, 2000 larval mortality 465,000 28.5 Initial nominal Gulec and Holdaway, 2000 mortalilty Initial TPH on Cohen and Nugegoda, stocks 2000 Mitchell and Holdaway, mortality 0.7 9 Initial stock TPH 2000 mortality 0.7 7.2 Initial stock Mitchell and Holdaway, TPH 2000 embryo 4.48 2.62 Initial stock Pollino and Holdaway, mortality TPH 2002b embryo 3.38 1.94 Initial stock Pollino and Holdaway, mortality TPH 2002b embryo 2.1 1.67 Initial stock Pollino and Holdaway, mortality TPH 2002b embryo 1.28 1.37 Initial stock Pollino and Holdaway, mortality TPH 2002b embryo 3.38 2.92 Initial stock Pollino and Holdaway, mortality TPH 2002b embryo 2.1 1.25 Initial stock Pollino and Holdaway, mortality TPH 2002b embryo 1.28 0.74 Initial stock Pollino and Holdaway, mortality TPH 2002b NOTE: THC, summation of total hydrocarbon content C6 to C36; (W) , weathered; ANS, Alaska North Slope crude oil; PBCO, Prudhoe Bay crude oil; BSC, Bass Strait crude oil; ALC, Arabian light crude; VCO, Venezuelan medium crude oil.
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From page 240... ...
through narcosis mysid shrimp) Balanus Larvae Diesel Vecom 24 static phototaxis amphitrite oil B-1425 inhibition (barnacle)
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From page 241... ...
Oil Effect Concentration Estimatec mg/L Conc. Comments Reference 11.31 111.07 Initial THC Singer et al., 15.90 48.03 1998 NA LOEC; Initial No oil alone comparison.
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From page 242... ...
(2% of stock prepared daily) Macquaria Juvenile BSC Corexit 96 constant Oxygen novemaculeata 9527 (1:30)
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From page 243... ...
DO WAF concentrations >5x higher cf. WAF NA NA Initial TPH LDH activity higher in DO Cohen et al., on stocks WAF cf WAF.
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From page 244... ...
Endpoint Salmo salar Immature BSC Corexit 144 (plus constant Hepatic 9527 (1:50) 29 days flow- EROD recovery)
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From page 245... ...
Oil Effect Concentration Estimatec mg/L Conc. Comments Reference NA NA Initial TPH Induction of EROD by 2 days in Gagnon and WAF and DO WAF -- induction Holdaway, levels higher and more 2000 persistent in DO WAF.
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From page 246... ...
renewal growth rate (green hydra) FISH Salmar salmar Juvenile Mesa Corexit 48 static daily EROD activity (rainbow sour 9500 (1:20)
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From page 247... ...
Oil Effect Concentration Estimatec mg/L Conc. Comments Reference >0.6 0.6 Initial stock Mitchell and TPH Holdaway, 2000 >0.6 4 Initial stock Mitchell and TPH Holdaway, 2000 0.00072 0.0006 Initial TPH CYP1A induction x106 in Ramachandran and PAH CEWAF (if expressed as et al., 2004 % v/v ratio)
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From page 248... ...
monitored 29 days No change in before exposure and 30 phyto- or zoo days post-exposure plankton density, Response: plankton planktonic biomass, counts, metabolic rate, metabolic rates, aqueous microbial or microbial counts, bioassays populations with (Daphnia, rainbow trout, O or DO plots and microtox) NOTE: O, oil; D, dispersant; DO, chemically dispersed oil; NWC, Norman Wells Crude Oil.
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From page 249... ...
Prudhoe Bay crude oil on early life stages of three Pacific marine species: the red abalone, Haliotis rufescens, a kelp forest mysid shrimp, Holmesimysis costata, and the topsmelt, Atherinops affinis and concluded that CEWAF versus WAF toxicity was dependent upon test species and exposure time (also see earlier in Chapter 5)
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From page 250... ...
(2001a,b) using juvenile fish exposed to Bass Straight crude oil and Corexit 9527 found that chemically dispersed oil increased the response in many of the biochemical indicators examined (e.g., cytochrome C oxidase)
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From page 251... ...
Finally, effects on infaunal benthic communities were found in the untreated oil site but not in the area exposed to dispersed oil. Researchers attributed these differences to the greater persistence of undispersed oil in the intertidal sediments.
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From page 252... ...
Thus, it was not possible to determine if the use of dispersants increased the amount of oil that reached benthic habitats. However, a qualitative comparison of PAH measurements in oysters collected during other oil spills where dispersants were not applied, does not suggest any dramatic difference in uptake (Michel and Henry, 1997)
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From page 253... ...
Consequently, a focused series of experiments should be conducted to quantify the final fate of chemically dispersed oil droplets compared to undispersed oil, including an evaluation of the interaction with a broader range of sediment types.
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From page 254... ...
Thirty barrels of Corexit 9527 were applied over a 3-day period, for an application rate of 1:13. Applications followed guide lines in the facility's oil spill contingency plan.
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From page 255... ...
(1987) concluded that, from the toxicological perspective, the effects of oil and chemically dispersed oil on seabirds were similar, based on sublethal responses at the biochemical and physiological level.
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From page 256... ...
indicates that a multitude of surface-active organic contaminants, including petroleum compounds and detergents, may have detrimental effects on aquatic birds due to alterations in water surface tension. Application of chemical dispersants during an oil spill
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From page 257... ...
could cause temporary toxic effects to natural microbial populations. Studies of biodegradation rates that report changes in bacterial growth (numbers)
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From page 258... ...
, using dilutions up to 1:1,000, but weathered Nigerian crude oil was not mutagenic. No data were available for the dispersed oil mixture.
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From page 259... ...
communities. Coral Reefs Compared with other test species, data on the effects of dispersants and/or chemically dispersed oil and comparisons with physically dispersed oil on coral species are even more limited.
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From page 260... ...
indicates toxicity) Rat intestinal bacterial D; Corexit 9527, Corexit 9500 Bacterial no.'s mixed population O; Weathered Bonnie light Species diversity Salmonella typhimimurium Nigerian crude oil Bacterial enzymes (mutagenicity study)
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From page 261... ...
261 TOXICOLOGICAL EFFECTS OF DISPERSANTS AND DISPERSED OIL Finding Reference Increased no.'s with D alone Elevated no.'s in DO c.f. O alone Mulkins-Phillips Changes in species diversity with DO (genus level)
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From page 262... ...
NOTE: ANS, Alaskan North Slope crude oil; ATP, adenosine triphosphate; D, dispersant; DO, chemically dispersed oil; FW, freshwater; MPN, most probable numbers; O, oil; W, weathered. a Biodegradation study with indirect toxicity observations.
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From page 263... ...
and chemically dispersed oil (using Corexit 9527; dispersant to oil ratio at1:100 and 1:10) or dispersant alone for 4 hr and assessed fertilization rates.
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From page 264... ...
Chemically dispersed oil exposures resulted in a dramatic increase in acute toxicity to both coral species larvae. In addition, the authors reported that dispersants and dispersed oil treatments caused larval morphological deformations, loss of normal swimming behavior, and rapid tissue degeneration.
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From page 265... ...
. At the untreated oil site no significant impacts to corals were observed at any of the time points (Dodge et al., 1995)
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From page 266... ...
were monitored continuously for 24 hr using a field fluorometer that was calibrated to convert fluorescence into the concentration of physically and chemically dispersed oil. Discrete and unfiltered water samples were collected for chemical analysis by gas chro matography (GC)
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From page 267... ...
An additional stress for corals may be attributed to the physical toxicity of oil droplets. It has been observed that oil droplets adhere to the surface of the coral, which results in a complete breakdown of the under FIGURE 5-7 Case study: (TROPICS, Panama)
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From page 268... ...
NRC (1989) stated that the smaller droplets in chemically dispersed oil did not adhere to the corals, in contrast to the larger, physically dispersed oil droplets, some of which were found on coral a few weeks after
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From page 269... ...
, no negative effects were observed for plant survival, growth rates, or leaf blade area at the dispersed oil treatment site compared to the non-oiled reference site. Untreated, whole oil caused significant impacts to mangrove habitats with high levels of defoliation and 17 percent mortality of adult mangroves after 2 years.
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From page 270... ...
It is unclear whether chemically dispersed droplets or physically dispersed droplets or accumulation of dissolved components could alter this response. The excessive production of mucus takes energy away from normal cellular processes potentially reducing the overall health and fitness of the coral.
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From page 271... ...
There is insufficient information to determine how chemically dispersed oil interacts with suspended sediments, as well as biotic components of aquatic systems, both short- and long-term, compared to naturally dispersed oil. Relevant state and federal agencies, industry, and appropriate international partners should develop and implement a focused series of experiments to quantify the weathering rates and final fate of chemically dispersed oil droplets compared to undispersed oil.
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From page 272... ...
NOTE: D, dispersant; DO, chemically dispersed oil; D:O, dispersant:oil ratio; HC, Hydrocarbon concentration (ppb) ; O, oil; PBCO, Prudhoe Bay Crude Oil; SW, seawater; TPH, total petroleum hydrocarbons; WAF, water-accommodated fraction; WSF, water soluble fraction.
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From page 273... ...
Assessment investigations of oil spills that are not treated with dispersants) implement a field program to measure both dissolved-phase PAH and particulate/oil-droplet phase PAH concentrations for comparison to PAH thresholds measured in toxicity tests and predicted by computer models for oil spill fate and behavior.
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From page 274... ...
The primary assumption for models predicting acute toxicity of physically and chemically dispersed oil is additive effects of dissolved-phase aromatic hydrocarbons. However, the possibility of photoenhanced toxicity and particulate/oil droplet phase exposure is generally not considered.
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From page 275... ...
estimate the relative contribution of dissolved and particulate oil phases to toxicity with representative species, including sensitive species and life stages; and (3) expand toxicity tests to include an evaluation of delayed effects.
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