xvEPA
         United States
         Environmental Protection
         Agency
           Office of Research and
           Development
           Washington DC 20460
EPA/600/R-98/104
November 1998
Synthetic-Based
Drilling Fluids:
An Assessment of the
Spatial Distribution of
Toxicants in
Sediments from Gulf of
Mexico Drilling Platforms

A Report Prepared for the
Office of Water

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                                                EPA/600/R-98/104
                                                  November 1998
Synthetic-Based Drilling Fluids: An Assessment
             of the Spatial Distribution
 of Toxicants in Sediments from Gulf of Mexico
                 Drilling Platforms
   A Report Prepared for the Office of Water
                           By

                      Carol B. Daniels, Ph.D.
                  U. S. Environmental Protection Agency
                 National Health and Environmental Effects
                       Research Laboratory
                      Gulf Ecology Division
                 1 Sabine Island, Gulf Breeze, FL 32561-5299
                                             Printed on Recycled Paper

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 Abstract
 Use of the amphipods, Leptocheirus plumulosus and Ampelisca
 abdita, iff these bioassays presented no major difficulties in the
 execution of these test protocols. Sensitivity to the toxicants was
 exhibited by L. plumulosus and survival of control animals was
 good  suggesting the suitability of  this organism for use.
 Continued application of these species to evaluations of field-
 collected sediments contaminated with Synthetic-based drilling
 fluids  (SBF)  is  encouraged  and  should  enhance our
 understanding of the toxicity of these products.  Data from this
 initial  screening with   Leptocheirus  plumulosus  indicate
 sensitivity of this species to sediments collected within a 150
 meter radius of platform 1 (GI95) and demonstrate the spatial
 distribution of contaminants along a gradient. Sediments within
 the vicinity of the other two platforms, (platform 2, SMI57C and
 platform  3, ST148) proved to be less toxic than those from
 platform  1 but serve to illustrate the sensitivity of the organism,
 L. _ piiimulosus to a  range  of SBF.   Data from tests  with
 Ampelisca abdita indicated a lower  sensitivity to the  field-
 collected samples  than  was observed with L.  plumulosus.
 Survival values in the range of the control suggested an apparent
 lack of toxicity from any of the sites to this organism above
 those of background. Procedural delays were thought to have
 reduced the overall responsiveness of Ampelisca abdita in these
 tests.  Measures of sample  variability  indicated variability
 between replicate samples from the same grab and between
 sequential grabs.  Variability denoted in composite samples
 suggests additional research should be conducted to improve the
 protocol to achieve sample homogenization.  Coarse-sieving of
 field-collected sediments should also be explored to ascertain if
 such procedural modifications  might also reduce  sample
 variability.

 1. INTRODUCTION
 Increasing pressure from industry has  prompted the  U.S.
 Environmental Protection Agency (EPA)  to  consider the
 expansion of current regulatory guidelines for oil drilling to
 include language to facilitate more wide-spread use of synthetic-
 based drilling fluids (SBF) in the United States.   Synthetic
 based fluids are currently in  use in US coastal waters although
 no specific limitations for SBF have been set forth in current
 guidelines (EPA, 1996). Historically,  use of SBF has  been
 greatest in the North Sea (Friedheim and Conn, 1996); however,
 use of these agents in the US has grown appreciably (as many as
 300  wells in the Gulf of Mexico have been drilled with SBF)
 since the initiation of drilling of the first well using SBF in the
 Gulf of Mexico in 1992 (Candler et al., 1997).

 Synthetic-based  fluids have  been described as being more
effective than water-base  muds (WBM)  and oil-based muds
(OBM) and considered more environmentally benign than their
predecessors (Veil et al., 1996; Burke and Veil, 1995; Candler
etal., 1993; Friedheim eta.l, 1991). Despite indications of some
 environmental benefits use of the agents in US waters remains
 tenuous  until  questions  can  be   addressed  about  the
 environmental safety of these agents and the appropriateness of
 toxicity tests currently described in the coastal guideline to
 adequately  assess  the potential  impact of SBF  on benthic
 species.

 Synthetic-based fluids are muds prepared for drilling purposes
 which are manufactured from materials containing no detectable
 levels of priority pollutants. All major mud suppliers are said to
 offer SBF,  and formulations of these  materials are  routinely
 prepared using vegetable esters, polyalpha olefins (PAO),
 internal/isomerized olefins (IO), linear alpha olefins (LAO) and
 ethers (Candler et al.,  1997).  Traditional base-fluids such as
 diesel and mineral oil, are not designated SBF since they are not
 synthesized. Conversely, they are refined from crude oil and are
 known to contribute to the toxicity of drilling fluids (they release
 aromatics into the water fraction of  the fluids).   Concern
 regarding the use of SBF is related largely to questions  about the
 biodegradability and toxicity  of SBF-coated cuttings,  since
 cutting piles accumulate on the seafloor and synthetics, may
 account for as much as  12% of the material adhering to the
 surface of the cuttings (Friedheim and Conn, 1966).

 Because toxicity protocols, currently incorporated in the coastal
 guidelines, were designed to assess water-column effects (EPA,
 1996), limited toxicological data are available on the  potential
 impact of Synthetic-based fluids on North American benthic
 species (Candler etal., 1997; Candler, 1997; Hood, 1997a&b).
 One seafloor study has been completed which directly addresses ,
 the impacts of SBF discharges on benthic fauna of the Gulf of
 Mexico (Candler et al., 1995) and suggests diminished biological
 effects of an SBF when compared with an OBM.

 Evaluation of several  benthic endpoints  (species richness,
 diversity and number of individuals)  and  total  petroleum
 hydrocarbon (TPH) concentrations indicate a smaller area of
 transition (than for OBM)  surrounding  the PAO discharge
 platform with community level effects approaching background
 for the benthic fauna.

 Laboratory investigations with benthic species have focused on
 use  of  the  amphipods, • Corophium volutator,  Rhepoxinius
 abronius, Ampelisca abdita and Leptocheirus plumulosus, and
 deal almost  exclusively with the toxicity of the base fluids
 (Candler etal., 1997; unpublished data by Candler, 1997; Hood,
 1997a).  Contaminants of interest have included enhanced
mineral oils  (EMO), internal/isomerized olefins  (IO),  and
polyalpha olefins (PAO).  Some data exist on the toxicity of a
used, whole synthetic-base mud (Hood, 1997b)  and  indicate
some product toxicity.  The reported LC50 for the  used SBF
ranged between 692 mg/kg and 3, 600  mg/kg  in  10-day

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(definitive) sediment toxicity tests with R. abtonius, A. abdita
and L plumulosus. Ranking of species sensitivity to this product
indicated Leptocheirus > Rhepoxinius > Ampelisca.

Information gaps exist and suggest the need for continued
research on SBF to enhance our understanding of the toxicity
and potential hazards associated with the discharge of drilling
fluids and cuttings, contaminated with  synthetic material, into
sub-tropical waters such as the Gulf of Mexico. This study
represents a singular  attempt to  augment the current data to
provide information on the toxicity of three product types, IO,
LAO, and a combined ester-olefin mixture, currently in use on
drilling platforms in the Gulf of Mexico.

This study was designed to provide a qualitative assessment of
a series of field sites  in the Gulf of Mexico for the Office of
Water, with an indication of the potential hazards associated
with the field application/use of synthetic-based drilling fluids
(SBF).  Additionally,  this  report supplies information on the
relative sensitivity of two infaunal  amphipods,  Leptocheirus
plumulosus and Ampelisca abdita, to these agents and discusses
the feasibility of adapting a standardized protocol, such as the
10-day acute sediment toxicity  test  (EPA, 1994), to the
evaluation of a non-homogeneous geochemical matrix of SBF
mixed with sediment.

The use of L plumulosus and A.  abdita in this study, and their
consideration for use  in Agency guidance for Synthetic-based
fluids, is  intended to complement  current regulatory trends
toward use of amphipods for the assessment of sediment-
associated contaminants and is intended to complement works
previously performed  on this unique group of products.  Both
Leptocheirus plumulosus and Ampelisca abdita have been used
routinely  for  the evaluation of the toxicity of marine and
estuarine sediments. Their sensitivity to a range of toxicants has
been documented in the scientific literature, and the method
reviewed  extensively. Guidance documents (ASTM,  1993;
EPA, 1994) have been prepared for these acute bioassays and
serve to substantiate the credibility of these protocols for use in
ecological risk assessment.

Toxicity testing was conducted according to EPA Guidelines as
specified  in Methods for assessing the toxicity of sediment-
associated contaminants with estuarine and marine amphipods
(EPA, 1994). Testing was conducted at Gulf Ecology Division,
NHEERL, U.S. Environmental Protection Agency, Gulf Breeze,
FL,  and utilized undiluted, sediment samples collected in the
vicinity of three drilling platforms (GI95, SMI 57C and ST148)
during a reconnaissance survey conducted aboard the research
vessel S.S. Anderson (EPA) August 18-22,1997.
2. TEST SUBSTANCE
Field samples containing synthetic drilling fluids were received
from George Gibson, U.S. Environmental Protection Agency, on
August 23, 1997.  Samples were contained in sample jars of a
variable nature, i.e., size (1 -1.5 liter) and construction (glass or
high-density polyethylene). Upon receipt in the laboratory, the
samples were stored in the dark in an environmental chamber at
approximately 4°C.  Prior to  their use in the bioassay, each
sample underwent a visual inspection to assess spoilage. An
absence of a  foul odor and black spots on  the surface of the
sediments were noted for each sample, indicating suitability for
testing.

3. TEST ORGANISMS
Field samples were  evaluated using one marine amphipod,
Ampelisca abdita, and one estuarine amphipod, Leptocheirus
plumulosus.  Leptocheirus plumulosus were purchased from
Chesapeake Cultures (P.O. Box 507, Hayes, VA 23072, 804
693-4046) and were received on August 29, 1997. Ampelisca
abdita were purchased from East Coast Amphipod (16 Ayrault
St., Suite 1, Newport, RI02840,401 849-4631). The amphipods
were collected and shipped on September 3,1997, and received
on September 5, 1997, after a 36 H delay in  shipment.   ,

Feeding: No food was supplied to the amphipods during holding
and testing.

Age/Length:  Leptocheirus plumulosus used in this study were
mixed-age  adults  ranging in size from 2 to  4 mm. Ampelisca
abdita were juveniles, ranging in size from 0.71 mm to 1.18 mm.

Receipt/Handling: Water quality parameters of the overlying
water contained  in each organism  shipping container were
measured  and recorded  upon  arrival at  the laboratory.
Leptocheirus were shipped in water only, thus transfer of these
organisms  to containers of  freshly,  aerated  seawater was
accomplished by pouring the contents of a container through a
 125 \jm\ sieve. Amphipods retained on the  screen of the sieve
were flushed from the screen with a gentle stream of saline (20
ppt) water into 2L Carolina culture dishes containing  20  ppt
oxygenated seawater. Bowls  were aerated and the organisms
were held at 20±1°C until the randomization process was
initiated.

As was the case with Leptocheirus, water quality parameters of
the overlying water of each shipping container of  Ampelisca
were measured and  recorded upon  arrival  at the laboratory.
Collection of Ampelisca was slightly different, however, as the
amphipods had been shipped  in sediment obtained  from their
collection site. Using a rubber spatula, sediment containing the

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 amphipods was removed from the shipping container and placed
 on the surface of a 500 ,um sieve. The sieve was placed inside
 a large polyethylene tub and ambient sea water gently sprayed
 over the surface to facilitate removal of the sediments.    ~~

 Most of the sediment passed through, leaving the amphipods
 behind. A fine spray of water was again passed over the sieve
 to ensure organisms  had been  flushed  from  their  tubes.
 Amphipods retained on the screen of the sieve were flushed
 from the screen with a gentle stream of 28 ppt water into 2L
 Carolina culture dishes containing 20 ppt oxygenated seawater
 (28 ppt).  The tubes were examined to see if any amphipods
 were present. Amphipods found adhering to the water surface
 were removed from the containers by placing a fine-meshed
 screen just below the surface of the water and gently lifting them
 out.    These organisms  were added  to the culture dishes
 containing animals previously  collected.   The bowls were
 aerated and the organisms were held in environmental chambers
 maintained at 28±1°C until the randomization process  was
 initiated.

 4. REFERENCE & FIELD-COLLECTED SEDIMENTS
 The reference sediment for these tests was sediment collected by
 the supplier. In the case of Leptocheirus, no sediment  was
 received from the vendor; therefore a sediment obtained from a
 non-polluted region of the Pensacola Bay Estuary was used as a
 reference sediment. The sediments were coarse^sieved through
 a 2,000 /urn stainless steel, sieve and fine-sieved through a 500
 yum stainless steel, sieve to remove any large organisms that were
 confused with or preyed upon the amphipods.

 Field-collected sediments were not wet-sieved, in an attempt to
 maintain the integrity of their geochemical properties. Stainless
 steel forceps were used, however, to remove large objects (shell
 and other debris) and predators from the field samples prior to
 use in the bioassay. Samples collected from multiple benthic
 grabs were homogenized by stirring by hand. Samples from the
 same benthic grab were similarly homogenized, if  the samples
 were received in more  than one storage container.

 5. OVERLYING WATER
 In the case of Leptocheirus, the overlying water added to the
 exposure chambers after the addition of the sediment-test was 20
 ppt natural, filtered sea water.  The overlying water added to A.
 abdita exposure chambers was 28 ppt natural, filtered sea water.
 Synthetic sea water was prepared by adding a brine solution
 (prepared from a commercial preparation of dried, balanced sea
 salts [Forty Fathoms Sea Salts, Baltimore, MD]) to natural sea
 water (20 ppt filtered seawater) to obtain a seawater mixture of
 28 ppt salinity. The resultant solution was aerated and allowed
 to age for. several  days prior to use.   Water for tests with
Ampelisca was maintained in a water bath at 20 °C, and seawater
 for Leptocheirus maintained at 25°C.
 6. EXPOSURE CHAMBERS
 Exposure chambers were one-liter glass beakers. Glassware was
 acid-washed prior to use, rinsed five times with deionized water
 and air-dried prior to affixing sample labels to each exposure
 vessel. Beakers contained approximately 2 cm of field-collected
 sediment.   Sediments were  weighed to  ensure  equivalent
 amounts of material were delivered to each beaker  (average
 weight of sediment disbursed = 253.47 g). Sea water (800 ml,
 20 ppt and 28 ppt salinity, respectively, for L. plumulosus and A.
 abdita) was added to each exposure chamber to bring the total
 volume of sediment and overlying water to 1 liter.

 7. TEST CONCENTRATION
 Because a limited amount of sediment was received, the test was
 conducted as a screening bioassay.  As such, a geometric series
 of concentrations of the sediments was  not tested.  Rather,
 replicate samples (3) of the undiluted field-collected sediment
 were evaluated against a control in the 10 day acute test.

 Exposure chambers  containing control and field-collected
 samples were placed onto a water table maintained at  20°C.
 Each exposure chamber was covered with a  watch glass
 containing  a small hole  used for insertion of an  aeration
 apparatus.   Gentle aeration of each  exposure chamber was
 established  using flexible air-line tubing fitted  with a 1  ml
 serological  glass  pipette.  The flexible  air-line tubing was
 connected to a gang valve, and the tapered end of the pipette
 inserted through the hole of the watch glass, suspending it to a
 depth approximately 2 cm below the surface of the water in the
 exposure chamber. Temperature, dissolved oxygen,  pH  and
 salinity were measured in the overlying water in each treatment
 and control.

 8. PREPARATION OF TEST ORGANISM
 Organisms  maintained overnight in two-liter Carolina dishes
 were randomly distributed using  a  fire-polished,  wide-bore
 dropping pipette  to  10 ml  glass beaker  cups  containing
 approximately 10 ml of  sea water.   Five organisms  were
 randomly delivered into each cup; a total of twelve cups were
 prepared for each treatment and control.

 9. TEST INITIATION
 The test was initiated when twenty organisms, introduced into
 each exposure chamber by gently pouring the 10-ml cups over
 a fine-meshed screen, were transferred from the screen into the
 overlying water of the exposure chamber. This procedure was
 repeated until the  required number of organisms (20) was
 introduced into the exposure chambers.

 10. TEST MONITORING & TERMINATION
The bioassay was performed under condition of continuous light
in accordance with the recommended test conditions (Table 1).
Aeration of the  exposure chambers was  continuous, each

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chamber was observed daily and the airflow adjusted, as appro-
priate, to ensure maintenance of dissolved oxygen  at ^90%.
Temperature, dissolved oxygen (D.O.), pH and salinity were
measured in the overlying water of each treatment and control at
the start and conclusion of the test. Water quality parameters
(D.O.. pH, salinity and temperature) were monitored daily for a
single representative of each treatment and control group.

The test was terminated 10 days after introduction of the
amphipods to the exposure chambers.  Beginning with the
control  treatment, the contents of each replicate were poured
onto the screen of a 500-A/m nylon, sieve held over a plastic tub.
The organisms were typically retained on the screen while most
of the sediment passed through the screen. A fine spray of water
was passed over the sieve to remove any sediments adhering to
the surface of the screen.

Animals were collected from the sieve any passing through the
screen were recovered from the surface of the water retained in
the tub (refer to the prior description of this technique) and all
were placed in a finger bowl.  The finger bowls were placed on
an illuminated   light table and the number of  surviving
organisms   determined.    In cases  where  mortality  was
questionable, determination of survival was made by examining
animals under a dissecting scope.

11. DEVIATIONS FROM PROTOCOL
Sediment toxicity tests  with L.  plumulosus and  A.  abdita
included a few departures from the standard testing protocols.
One  deviation from  the guidelines was the use of only three
replicate samples of each sediment evaluated, rather than the
prescribed minimum of four (EPA, 1994). This was necessitated
by the limited volume of material received and the  need to
conduct testing with two test organisms.  Because a reduced
number of replicates was used, test acceptability was modified
to include a minimum control survival of 80%.

Another deviation from recommended test guidelines was the
use of sediments beyond the suggested 14 day storage'limit
(ASTM, 1996). Sediments used in tests with Ampelisca were
beyond this limit at the initiation of the 10-day acute sediment
 toxicity test.  This was due to the initial receipt of a batch of
 organisms of inferior quality and a delay in receipt (36 H) of the
 replacement shipment of amphipods.  Visual and olfactory
 inspection of the sediments used  in tests with A.  abdita,
 however, indicated no apparent loss of quality for these samples.
 Because animals were shipped at temperatures and salinities
 matching those used in  the toxicity  tests, animals  were used
 without a period of acclimation as is generally recommended.

 12. STATISTICAL ANALYSIS
 The determination of 10-day LC,0 values was not performed, as
 a geometric series of sediment concentrations  had not been
 evaluated for each of the field-collected sediments. The mean
 percent (%) survival was calculated for each replicate group of
 samples and served as the basis for comparison. To compare
 sites, split samples from composites (although not statistically
 true  replicates) were used to compare  sample  variability
 (attributed to  the homogenization procedure) and to test the
 sensitivity of  the two test organisms, L. plumulosus and A.
 abdita. Replicate samples from the same benthic grab were used
 to compare within-grab variability.

 13. RESULTS
 Leptocheirus:  The bioassay Was terminated after 10 days of
 exposure, and the survival for each treatment group determined.
 Survival data for Leptocheirus plumulosus are tabulated in Table
 2. Data from tests with Ampelisca abdita are shown in Table 3.
 Data from tests with Leptocheirus indicate a high degree of
 toxicity (0 - 65% survival) for sites within a 150 m (1G1, 1G3,
 1G7 and 1G10) radius of drilling Platform 1 (GI95). Although
 survival at the platform  reference site (1 R3 A+B) was slightly
 reduced compared with to that noted in the control sediment (C-
 17) (83.3% compared to 95%), it was significantly different
 from the four test sites (1G1, 1G3, 1G7 and 1G10) referred to
 above.

 Sediment samples collected at sites adjoining Platforms 2 (SMI
 57C) and 3 (ST 148) were far less toxic than those collected in
 the vicinity of Platform 1. The lowest recorded survival (81.7%)
 for any of the sediments for stations surrounding Platform 2 was
 observed with sediments from station 2G2. Although sediment
 samples from stations within the survey area of  Platform 3
 demonstrated lower toxicity than sediments  from Platform  1,
. they tended to be slightly more toxic than samples obtained from
 sites near Platform 2.  Sediments from the reference  site for
 Platform 2 (2R1)  were of equivalent toxicity  (95%) to the
 control sediment (C17).   A survival  value of 86.7%  was
 recorded for the sediments from the Platform 3 reference site
 (3R2).

 Ampelisca: Tests  with Ampelisca indicated lower survival
 (86.67%) with the control treatments (i.e., Ampelisca control
 sediment)  than  was  observed  with  Leptocheirus  (95%).
 Contrary  to  indications  'of L.  plumulosus adaptability  to
 Pensacola Bay sediments (C17), this sediment proved unsuitable
 for  habitation by A.  abdita  (0%  survival).   Survival  of
 amphipods treated with sediments from Platforms  1, 2 and 3
 indicated no adverse toxicity .beyond that demonstrated for the
 control treatment. The lowest survival value was 83.3% and was
 recorded for organisms treated with sediments from 1 GlOB and
 3G1 A+B.  In one case, survival (91.7% ) for one of the field-
 collected sediments (2G6) exceeded that  recorded  for the
 Ampelisca control sediment (86.7%).  Toxicity for the two
 reference sites (1R3A+B and 3R2) evaluated in this series  of
 acute toxicity tests indicated comparability to that determined for

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the control: sediment (85.0% and 88.3 % survival, respectively,
compared with 86.7% for the control).

Reference  Toxicant:    Toxicity  evaluations  involving the
reference toxicant, copper  sulfate were, performed at con-
centrations in excess of the 96-hour LC50 of copper sulfate, for
both L. plumulosus and A. abdita to ensure demonstration of a
lethal effect. In both cases, all animals had expired within 24 H
of their initial exposure.

14. CONCLUSIONS
Use of the amphipods, Leptocheirus plumidosus and Ampelisca
abdita, in these bioassays presented no major difficulties in the
execution of these test protocols. Sensitivity to the toxicants was
exhibited by both organisms, and survival of control animals was
good, indicative of the suitability of L. plumulosus and A. abdita
for use. Continued application of these species to evaluations of
field-collected sediments  contaminated with  synthetic-based
fluids.(SBF) is encouraged and is expected  to  enhance our
understanding of the toxicity of these products.

Data from this initial  reconnaissance survey indicate toxicity
associated with sediments recovered from sites surrounding at
least one of the drilling platforms (Platform 1; GI95). Although
toxic responses   were  limited,  only  one  (Leptocheirus
plumulosus) of the two species  tested  (L. plumulosus  and
Ampelisca  abdita) at these sites warrant closer examination,
because of the extreme degree of toxicity (0% survival) denoted
for at least one site (1G1) in close proximity (50 m) to the point
of discharge for Platform 1. Toxicity was also clearly evident at
other sites within a 150 m radius of this platform (1G3,1G7 and
1GIO), although survival was not nearly as limited for animals
exposed  to these sediments as for those treated with sediments
from IGl.

These data, coupled with data from the reference site for this
platform (1R3), clearly indicate the spatial  distribution  of
toxicants beyond the point of discharge and illustrate the dilution
of a pollutant  along a geographic gradient.  Similarly, recent
work by  Candler et al. (1995) demonstrated the distribution of
contaminants within a 200 m radius of a synthetic-base well
(characterized as using PAO) in the Gulf of Mexico.

Quantitative analysis and pollutant characterization have not yet
been  completed for these samples, • thus the nature of the
contaminant(s) associated with these samples or the identity of
the agents eliciting this  toxic  response is not yet  clear.
Petroleum  is suspected of  having contributed to the  toxic
response noted with Leptocheirus, as  a  smell of petroleum
products  was clearly  evident  when  these  samples  were
distributed to the  test chambers.. Furthermore introduction of
water to the beakers containing these sediments resulted  in the
formation of a surface sheen.  Because oil can be quite toxic to
aquatic life  (Neff and Anderson, 1981), the  presence of
petroleum and petroleum by-products may serve to mask or
enhance the  toxicity associated with any synthetic materials
discharged from the drilling platform.

Comparison of data from 10 day, static acute sediment tests with
the two target organisms, L. plumulosus and A. abdita, indicate
comparative  sensitivity   of  Leptocheirus  >   Ampelisca:
Ampelisca abdita was seen to be less susceptible to the effects
of exposure to the synthetic muds than was Leptocheirus, despite
the lower numbers of amphipods noted in sediments from both
the control treatments and the reference sites at the conclusion
of the test. The lower survival counts denoted in A. abdita
control sediments were attributed to stress experienced by the
animals prior to initiation of the test (i.e., the 36 H shipping
delay).

Comparison of survival data from treatments involving exposure
to sediments  from multiple (benthic) grabs at  a collection site
indicates a small degree of variability among sequential grabs.
Hand mixing of composite sample tended not to reduce the
variability  associated with  replicate  samples,  although it
appeared not  to distort the toxic effect noted in the. individual
grab samples. Additional research should be conducted to see
if other methods of mixing might further reduce the variability
among sample replicates. Considerable amounts of shell and
other marine  debris were associated with  the samples making
recovery and counting of the amphipods rather time consuming.
The presence of this material was also thought  to partially
contribute to the variability observed among sample replicates.
Additional studies should be initiated  to  assess the effect of
coarse-sieving of these sediments on the sample toxicity.
15. REFERENCES
American Society for Testing and Materials.  Standard Guide
  for Conducting 10 day Static Sediment Toxicity Tests with
  Marine and Estuarine Amphipods, Designation E 1367-92.
  Philadelphia, PA: American Society forTesting and Materials,
  1996.
Burke, CJ. and J.A. Veil.  Potential Environmental Benefits
  from Regulatory Consideration of Synthetic Drilling Muds,
  ANL/EAD/TM-43,Argonne, IL: Argonne National Laboratory
  (1995).
Candler, J., R. Hebert and AJ J. Leuterman. "Effectiveness of
  a 10-day ASTM Sediment Test to Screen Drilling Mud Base
  Fluids for Benthic Toxicity." In Proceedings of SPE 37890 •
  SPE/EPA   Exploration  and  Production  Environmental
  Conference, Dallas, TX, March 3-5, 1997..
Candler, J.  1997. Personal Communication, June 30, 1997.
Candler, J., S. Hoskin, M. Churan, C.W. Lai and M. Freeman.
  1995.  "Seafloor Monitoring for Synthetic-Based Mud Dis-
  charged in the Western Gulf of Mexico." In Proceedings of

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SPE  29694  SPE/EPA  Exploration  and  Production
Environmental Conference, Houston, TX, March 27-29, 1995.
Candler, J., J.H. Rushing, and A.J.J. Leuterman. "Synthetic-
  Based Mud Systems Offer Environmental  Benefits Over
  Traditional Mud Systems." In Proceedings  of SPE 25993
  SPE/EPA  Exploration  and  Production   Environmental
  Conference, San Antonio, TX, March 7-10, 1993.
Daan, R., K.  Booij, M. Mulder, and E. M. vanWeerlee.
  Environmental effects  of a discharge of  drill cuttings
  contaminated with esr-based drilling muds in the North Sea.
  Environmental Toxicology and Chemistry I5(10):1709-1722
  (1996).
Friedheim, I.E. and H.L. Conn. "Second Generation Synthetic
  Fluids in the North Sea: Are they Better?" In  Proceedings of
  SPE 33061 presented at ADDUCE/SPE Drilling Conference,
  New Orleans, LA, March 12-15, 1996.
Friedheim, J.E., G.H. Hans, A. Park and C.R. Ray.  "An
  Environmentally  Superior Replacement for Mineral-Oil
  Drilling."   In Proceedings  of  SPE 23062 presented at
  Offshore Europe Conference, Aberdeen, Scotland, September
  3-6,1991.
Hood.C. 1997a^ Personal Communication, April 21, 1997.
Hood.C. 1997b. Personal Communication, July 9,  1997.
Neff, J. M. and J. W. Anderson. Response of Marine Animals
  to Petroleum Hydrocarbons. Applied Science Publishers Ltd.,
  London, 1981.
U.S.  Environmental  Protection Agency.   Final Effluent
  Limitation  Guidelines  and  Standards  for the, Coastal
  Subcategory of the Oil and Gas Extraction Point Source
  Category.  Federal Register 66086 (December 16, 1966).
U.S. Environmental Protection Agency. Methods for assessing
  the  toxicity of  sediment-associated  contaminants with
  estuarine  and  marine  amphipods,  EPA/600/R-94/025.
  Washington, DC. U.S. Environmental Protection Agency,
  1994.
Veil C. J. Burke, and D.O. Moses. Synthetic-based Muds Can
  Improve Drilling Efficiency Without Polluting.   Oil Gas
  Journal March 4, 1996:49-54(1996).

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Table I. Test conditions for conducting a 10-d sediment toxicity test with Ampelisca abdita, Eohaustorius estuarius,
        Leptochelnts plumulosus, or Rhepoxynius abronius.                                     , "
  Parameter
 Conditions
  1. Test type:

  2. Temperature:



  3. Salinity:


  4. Light quality:

  5. Illuminance:

  6. Photoperiod:

  7. Test chamber:

  8. Sediment volume:

  9. Overlying water volume:

  10. Renewal of overlying water:

  11. Size and life
     stage of amphipods:
  12.  Number of organisms/
      chamber:

  13.  Number of replicate
      chambers/treatment:

  14.  Feeding:

  15.  Aeration:
  16.  Overlying water:

  17.  Overlying water quality:



  18.  Test duration:

  19.  Endpoints:


  20. Test acceptability:
 Whole sediment toxicity test, static

 15°C: E. estuarius and R. abronius
 20°C: A. abdita
 25 °C: L. plumulosus

 20ppt: E. estuarius and L. plumulosus
 28 ppt: A. abdita and  R. abronius

 Wide-spectrum fluorescent lights

 500-1000 lux

 24L:OD

 1-L glass beaker or jar with -10 cm I.D.

 175 mL (2 cm)

 800 mL

 None

 A. abdita: 3-5 mm (no mature males or females)
 E. estuarius: 3-5 mm
 L. plumulosus: 2- 4 mm (no mature males or females)
 R. abronius: 3-5 mm

 20 per test chamber
Depends on objectives of test. At a minimum, four
replicates must be used.

None

Water in each test chamber should be aerated overnight before start
of test, and throughout the test; aeration at rate that maintains 90%
saturation of dissolved oxygen concentration.

Clean sea water, natural or reconstituted water.

Temperature daily. pH, ammonia, salinity, and DO of overlying
water at least at test start and end. Salinity, ammonia, and pH of pore
water.

lOd

Survival (reburial optional for E. estuarius, L. plumulosus, and R.
abronius)

Minimum mean control survival of 90% and satisfaction of
performance-based criteria specifications outlined in the guidance document.

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Table 2. Survival data for Leptocheirus plumulosus exposed to field-collected sediments
        containing synthetic based drilling muds.
Descriptor
Platform 1


-








Platform 2



Platform 3


Controls

Site ID
1G1
1G1 rep4
1G3A
1G3B
1G3 A+B
1G7A
1G7B
1G7 A+B
1G10A
1G10B
1G10A+B
1R3A+B
2G2
2G6
2G9
2R1
3G1 A+B
3G5 A+B
3R2
C-17
Copper sulfate
Distance from
Platform
50
50
50
50
50
150
150
150
100
100 •
100
2000
50
150
100
2000
50
150
1000
NA
NA
Survival (%)
* 0
o
51.67
56.67
55.0
61.67
63.33
65.0
51.67
56.67
58.3
83.3
81.67
90.0
91.67
95.0
86.67
90.0
86.67
95
0
Standard Error
of the Mean
0
0
3.33
8.82
8.66
8.82
9.28
, 8.66
3.33
12.02
8.33
3.33
.1.67
5.77
4.41
0
3.33
5.77
3.33
2.89
0

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 Table 3. Survival data for Ampelisca abdita exposed to field-collected sediments containing synthetic based
         drilling muds.
   Descriptor
Controls
Site ID
Distance form
Platform (m)
                                                                Survival (%)
                   Ampelisca Control
                        Sediment
                      NA
                                         86.67
Standard Error
  of the Mean
Platfonn 1


„
Platfonn 2


Platform 3


1G3A
1G3B
1GIOB
1R3 A+B
2G2
2G6
2G9
3G1 A+B
3G5 A+B
3R2
50
50
100
2000
50
150
100
50
150
1000
86.67
85.0
. 83.33
85.0
85.0
91.67
83.33
83.33
85.0
88.33
8.82
7.64
6.67
2.89
0
4.41
3.33
.6.67
2.89 -
4.41
                                                             3.33
                         C-17

                          Cu
                      NA

                      NA
                         0

                         0
      0

      0

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