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Hydrocarbon depuration and abiotic changes in artificially oil contaminated sediment in the subtidal
Estuarine, Coastal and Shelf Science (1987) 24.567-583
Hydrocarbon Depuration and Abiotic Changes in Artificially Oil Contaminated Sediment in the Subtidal
John A. Berge”,‘, Freydis Oreld*
Rainer
G. Lichtenthaler”
and
“Biological Institute, Department of Marine Zoology and karine Chemistry, University of Oslo, P.B. 1064 Blindern, Oslo 3, Norway, and bCenter for Industrial Research, P.B. 350 Blindern, Oslo 3, Norway Received 7January
1985 and in revisedform 18Jme 1986
Keywords: Benthic environment, sediment parameters, bioturbation,
marine pollution, Norway
crude oil, degradation,
North Sea crude oil was mixed with sediment in concentrations similar to those found in heavily polluted areas (10 000 and 18 000 ppm) and placed in experimental boxes in the subtidal. Experiments were performed in two Norwegian fjords, the eutrophicated Oslofjord (experimental period of 3 months) and the non-eutrophicated Raunefiord (13 months). Physical and chemical responses of the contaminated sediment were compared with similarly treated control sediment without oil. Depuration was investigated using gas and liquid chromatographic analyses for determination of total hydrocarbon content and selected single aromatic components. Biodegradation was followed using n-alkane/ branched alkane ratios. No depuration or biodegradation of hydrocarbon, or pronounced changes in sediment nitrogen and carbon content were observed after exposure in the Oslofiord. In the Raunefjord the redox potential was reduced by 75-200 mV in the oil contaminated sediment after 9 and 13 months. In the control sediment nitrogen and carbon content were significantly reduced after 9 and 13 months but did not change in the oil contaminated sediment except at the sediment surface (O-l cm). A significantly higher macrofaunal biomass was found in the control sediment after 9 and 13 months but not after 5 months. After 13 months of exposure in the Raunefjord 3391~ of the originally added oil remained in the sediment. The most soluble components such as naphthalene and methylnaphthalene were reduced by two orders of magnitude and less soluble components such as phenanthrene and methyiphenanthrene by one order of magnitude. Reduction was most pronounced at the sediment surface. Biodegradation in the Raunefjord sediment was documented after an initial lag period of 4-9 months. It is suggested that lower bioturbation and resuspension rates are responsible for the reducing conditions and the conservation of carbon, nitrogen and particle size distribution in the oil contaminated sediment. Results found as a consequence of oil, resemble the effect of eutrophication. Observed differences between test and control sediment may be caused by ‘Present address: Norwegian Institute for Water Research, P.O. Box 333 Blindern, N-0314 Oslo 3, Norway. 567 0272-7714/87/040567+17803.00/0
0 1987 Academic Press Inc. (London) Limited
568
J. A. Berge, R. G. Lichtenthaler
&F.
Oreld
toxicity of the oil directly or may be mediatedthrough other parameterseffected by the oil. Only limited areasare likely to receivesuchhigh oil concentrationsasapplied in the presentstudy. However, when suchconcentrationsare presentthe effects on sedimentparametersare significant. Introduction As a consequenceof off-shore oil exploitation and accidental oil spills, much effort has been put into studies on the fate and effect of petroleum and petroleum products in the marine environment. Most studies have been performed after accidental oil spills with the main focus on possible effects in the intertidal. The subtidal, however, has not been so extensively investigated, even though petroleum hydrocarbons may also contaminate subtidal sediments both after accidental oil spills (Besliers et al., 1980; Sanders et al., 1980) and after the discharge of oil-based drilling mud in connection with off-shore drilling operations (Addy et al., 1984; Davies et al. 1984; Massie et al., 1985). Investigations after oil spills have shown that oil may enter the sediment adsorbed on detrital material or incorporated in faecal material by sedimentation (Wade & Quinn, 1980; Boehm et al., 1982) and increased levels of hydrocarbons in sediment have been documented as a consequenceof urban activities (Mattsson & Lehtinen, 1985). The presenceof hydrocarbons in sedimentsmay modify chemical, physical and biological processes(Bakke et al., 1982) and cause an increased mortality of benthic animals (Sanders et al., 1980; seealso review by Teal & Howarth, 1984). A problem in describing and evaluating the effects of oil in the marine environment by studying accidental oil spills is finding representative control sites (Keizer et al., 1978). This problem can be overcome with field experiments where known amounts of oil are added to sediment and chemical and biological changes are compared with similar prepared controls without oil. Experimental oiling of subtidal sediments has been performed in Norway (Bakke & Johnsen, 1979; Bakke et al., 1982), in the middle Atlantic continental shelf (Boesch et al., 1981) and in mesocosm experiments in Massachusetts, U.S.A. (Grassle et al., 1980, Frithsen et al., 1985). Information on chemical, physical and biological responsesof known concentrations of oil in subtidal sediments are, however, few. In the experiments presented here we attempt to stimulate a situation where crude oil in high quantities (see Clark & MacLeod, 1977) sufficient for at least partially defaunation of the sediment is introduced to the top layer of a subtidal sediment. We focus on the physical and chemical behaviour of the sediment contaminated, with special reference to the depuration of hydrocarbons from the sediment. Materials Experimental
and methods sites
A three-month experiment was performed on a subtidal (23 m depth) muddy sediment near Vassholmen in the eutrophicated inner Oslofjord and a 13-month experiment on a subtidal (20 m depth) area with shell sand near Eggholmene in the noneutrophicated part of Raunefjorden on the west coast of Norway (Figure 1). Sediments for the experiments were collected at the experimental site for the Oslofjord experiments and at approximately 20 m depth, 1.3 km from the experimental site in the Raunefjord experiment (Figure 1).
Depuration
I
100
569
in oil contaminated sediment
km
\
(BjfLKAIf)
/j:;.:.:
.
.
1
OSLOFJORDEN
I
I
::
Figure 1. A map of the southern half of Norway showing thelocationof theOslofiord(A) and the Raunefjord (B) and more detailed chart showing the experimental areas. 0, Position of the experimental sites; n , position of site from where the sediment for the experiments in the Raunefjord were collected.
Preparation
of boxes and sampling
The experiments were performed by placing oiled and unoiled sediment on the seafloor in experimental boxes of PVC (55 x 37 x 12 cm high). The boxes were divided into four compartments, each with a surface area of 0.05 m2. The boxes were first filled with a 7.5 cm layer of unoiled sediment treated in a cement mixer for 3-5 min and frozen to stabilize the sediment. An additional layer of 3 cm of sediment mixed with unweathered North Sea Crude oil was added on top of the frozen sediment layer. The oil and sediment were mixed in a cement mixer for 15min (seeTable 1 for mixing data). The control boxes were treated similarly but with unoiled sediment. After this treatment all boxes were frozen again in order to kill the fauna and to prevent washing out the top layer of the sediment when submerging in the sea.The boxes were equipped with a lid during placement on the sea bed. Sediments for chemical analysis were taken by SCUBA divers using cores (inner diameter 6 cm) (seeTable 2 for sampling scheme). After sampling, the boxes were taken
570
J. A. Berge,
TABLE
R. G. Lichtenthaler
1. Conditions
Site
& F. Oreld
for the preparation
of the oil contaminated
Amount of oil used (ml)
Amount of sediment used (1)
Temp (‘0
240 374
30 50
15-20 9-15
Oslofjord Raunefjord
TABLE 2. Sampling
date and number
top 3 cm of the sediment
Measured cont. (wet weight) @pm) 3920 4520
Measured cont. (dry weight) (wm) 9940 17795
of boxes sampled Oslofiord
Raunefjord
Start of experiments: Date No. of control boxes submerged No. of oiled boxes submerged
11.04.80 2 2
18.02.81 6 6
First sampling: Date No. of control boxes sampled No. of oiled boxes sampled
08.07.80 2 2
25.06.81 1 1
Second sampling: Date No. of control boxes sampled No. of oiled boxes sampled
11.11.81 2 2
Third sampling: Date No. of control boxes sampled No. of oiled boxes sampled
23.03.82 3 3
to the surface and the remaining sediment sieved for macrofauna. Sediment cores for chemical analysis of the Oslofjord experiments were sectioned at 3-cm intervals and from the Raunefjord experiments at l-cm intervals. In samples from the Raunefjord, hydrocarbon analyses were also carried out on the 04l.5 cm depth section. Particle size distribution For particles larger than 64 e the size distribution was determined gravimetrically after wet sieving. Particles smaller than 65 l.trn were analysed using a Coulter Counter. Twoway analysis of variance (ANOVA) was performed separately on the fraction of sediment (arcsine transformed) in each particle size interval (six intervals for the sand fraction and four for the silt fraction) for oiled and control boxes at three depth intervals. Nitrogen and carbon determination Organic carbon determinations were made by wet oxidation (Gaudette et al., 1974). Total carbon and nitrogen were analysed with a Carlo Erba model 1106 CHN elemental analyser. Inorganic carbon was estimated as the difference between total carbon and organic carbon and assumed to consist of calcium carbonate carbon.
Depuration
TABLE
571
in oil contaminated sediment
3. Chemical
composition
( y0 dry weight)
Total carbon ( yO) Total nitrogen (%) Organic carbon (%) Organic C/N ratio Sediment particles larger than 2 mm (%) Sediment particles smaller than 63 pm (%) Calcium carbonate (%)
of the sediment
used in the experiments
Oslofjord
Raunefiord
4.4 0.34 3.1 9.1 0.5 58.4 11.5
12.0 o-73 6.2 8.5 1.5 23.5 50.3
Redox determination
Redox potentials were recorded using platinum electrodes and a calomel reference electrode and a voltmeter. Readings were taken after 5 min of equilibration in the sediment. Electrodes were calibrated with Zobell’s redox buffer. Biomass
Biomass(formalin wet weight) was determined gravimetrically by weighing macrofauna retained on a 1-mm sieve (excluding bivalves) from each compartment of the boxes. Analysis of petroleum hydrocarbons Determination of total hydrocarbon content in the sediments was performed by gas chromatography (Lichtenthaler, 1981). The single component analyseswere performed using high performance liquid chromatography followed by high resolution gas chromatography of aliphatic and aromatic fractions (Lichtenthaler 8zOreld, 1983, omitting the saponification step). Ratios of the compounds n-C17, n-C18, pristane and phytane were calculated asa measureof biodegradation of oil (Blumer & Sass,1972).
Results Environment
Temperature and salinity were relatively stable during the Oslofjord experiments (7.4-7.9 “C and 31.3-31.4X+ respectively) compared to the Raunefjord experiments (4-14 “C and 23-34%0, respectively). Current velocities were obtained only in the Raunefjord where, 2 m above the bottom, the current did not exceed 14 cm s-r. Sediment composition values at the start of the experiments are shown in Table 3. Results from particle-size distribution analyses at the end of the experiments in the Raunefjord are shown in Figure 2. The ANOVA on the results from the size frequency analysis showed no significant (P> 0.05) effect of oil treatment on the sand fraction. The only significant (P
572
J. A. Berge,
R. G. Lichtenthaler
O-l
& F. Oreld
l-2cm
cm
4-5cm
4
63
250 125
1000 500
: ::: 4 . .,.’ . . ‘: . . .. ‘:. : ::. __ . :: .-I. . ... . ‘, .,. ..: : ..:.. : . . ... 1::“.. :; .i., S...’
.. :*... . ;,.l . .. i . :* . ., 1.; :: . :f,.. .a.. 11.’ . .-” . * .: * :. :!> i, 63
.,Y; . . .. ,*. ,,.’ .,.‘) . ::.-. ..“.’ ; : :: . . :T’. . . >.z:: .._. ::*: . ‘.‘.‘: .:.*.. . I.. 250 1000 125 500 2000
2000 Sieve
mesh
63
250 125
1000 500
2000
(pm)
30
20
10
4
6
4
163264 Part!
6 cle
16
32
4
64
diameter
6
163264
(pm)
Figure 2. Results from particle-size distribution anaIysis at three depth intervals in the sediment at the end of the experiment in the Raunefjord. (A) Mean percentage of sediment weight in each particle-size interval for the sand fraction. (B) Mean percentage of sediment volume in each particle-size interval for the silt fraction. Stippled columns = percentage in control boxes; blank columns =percentage in oiled boxes exceeding values in control boxes. Height of blank column is indicated with a horizontal line when percentage in control exceeds values in oiled boxes.
control boxes as a result of a reduction in the particle volume in the 4-8 urn interval and an increase in the 32-64 urn interval. In the Oslofiord the mean total carbon content in the top 3 cm of the sediment was 4.74, in the oiled boxes and 4.3:/, in the control boxes. At the two other depth intervals the carbon content was almost identical and not significantly different from the level found in the sediment when preparing the boxes (4,40/o). The nitrogen content in the sediment was not significantly reduced during the experimental period in the Oslofjord and there was no significant (paired t-test, P>O.O5) difference between nitrogen content in oiled and control sediment at the end of the experiments. In the Raunefjord, the content of total carbon in the sediment at the end of the experiments (Figure 3) were significantly lower (paired t-test, P < 0.05) in the control boxes than in the oiled boxes. This difference was most pronounced for the depth intervals l-2 and 2-3 cm where there was a significant (t-test, P< 0.05) difference between the mean carbon contents in control and oiled boxes. The content of total carbon in both control and oiled
Depuration
in oil contaminated sediment
o/O 10
Carbon 11
573
o/o (2
13
0.2
0.4
Nitrogen
o/o
0.6
0.0
60
water 70
60
Figure 3. Sediment profiles showing the percentage of total carbon, total nitrogen and water contents in the boxes prior to (A) and after (B) exposure for the experiments performed in the Raunefjord. A horizontal bar indicates + 1 standard deviation (SD) of the mean. On the depth axis ‘ s ’ indicates a significant (PC 0.05) difference between percentage in oiled (0) and control boxes (0). Note that in (B), SDS are only indicated when larger than the radius of the symbol.
4. Concentration ratios of straight chain and branched Cl 7 and Cl8 hydrocarbons in oil-contaminated sediment prior to and after exposure in the Oslofjord
TABLE
n-Cl?/n-Cl8 Pristane/phytane n-C17/pristane n-Cl8/phytane
Before
After
1.08 1.20 1.43 1.59
1.10 1.27 1.37 1.56
boxes was reduced from an initial value of 12.7”, to approximately 9.5’,, in the top 1 cm of the sediment. At other depth intervals the reduction was not so dramatic. In the Raunefjord experiments 49% of the total carbon in the sediment (Table 3) was organic. Organic carbon was measured only at the start and at the end of the experiments in the depth interval l-2 cm in both the control and the oiled boxes. During the experimental period of 13 months the organic carbon in this depth interval fell from 6.17 to 5 I ‘Iq) (reduction= l.OF,,) in the control boxes. The reduction in the total carbon content in the sameperiod was 1.37”,, in the l-2 cm depth interval, thus 78O, of the reduction in carbon content in this depth interval in the control boxes wascausedby a reduction in the organic fraction. In the oiled boxes the reduction in the total carbon was from 12.71O0at the start of the experiment to 12.24”,, at the end of the experiment (reduction = 0.47”,,). The organic
574
J. A. Berge, R. G. Lichtenthaler
Redox
0 L% . .c “, ‘-
I
(mV)
,’
^
4
B
--
$2 3-
potentiol
& F. Ore/d
l-o-4
4-567-
-
Figure 4. Redox potential measurements in sediment from the experiments Raunefiord in November 1981 (A) and March 1982 (B). 0, Control boxes; boxes. Horizontal bar indicates f 1 SD (n = 4-6).
in the 0, oiled
carbon content at the start of the experiment in the oiled boxes was 6.74%, but had increased to 7+3% at the end of the experiment. In the Raunefiord experiments total nitrogen (Figure 3) followed the trend for total carbon, with a significant (paired t-test, P< 0.05) lower nitrogen content in the control boxes than in the oiled boxes. This difference wasmost pronounced in the depth intervals of 2-3 and 3-4 cm. A pronounced reduction in nitrogen from the initial O.7-O%o/0to 0.28O/, for the control sediment and 0.4% for the oiled sediment at the end of the experiments in the top O-l cm was measured. Deeper in the sediment the percentage nitrogen was unchanged in the oiled boxes but was significantly reduced in the control boxes. In both experiments there was a significantly (paired r-test, P< 0.05) higher water content in the oiled sediment than in the control sediment. Comparing each depth interval separately reveals that, at the end of the Raunefiord experiments, there was no significant difference between water content in the oiled and the control boxes at O-l and l-2 cm depth intervals. However, there wasa significant difference (t-test, P < 0.05) deeper in the sediment (seeFigure 3). There was a significant difference (t-test, P< 0.05) in redox potential at all measured depths in the oiled sediment in the Raunefjord both in November and March 1982 (Figure 4). The difference between readings in oiled and control boxes are in the range 75-200 mV. Both control and oiled boxes in the Oslofjord were colonized with speciestypical for an eutrophicated fiord; Polydora ciliata dominated and there were few clear negative effects of oil on the fauna. In the Raunetjord experiments, however, there wasa clear decreasein the number of species, individual densities of most speciesand biomass (Figure 5) in November 1981 and March 1982.
Depuration
d
575
in oil contaminated sediment
I
I
I
I
I
I
I
I
I
I
I
IQ
i
FMAMJJASONDJFM Time
of year
Figure 5. Mean macrofaunal biomass (formalin wet weight excluded bivalves) per compartment (0.05 m*) in control (0) and oiled boxes (0) from the Raunefjord experiments. Vertical bar indicates If: 1 SD.
Hydrocarbon
content and composition
The total concentration of hydrocarbons in the top 3 cm of the sediment did not change significntly during the experimental period in the Oslofjord, mean values being 9940 ppm (SD = 1190) (dry weight) at the start and 11560ppm (SD=470) after three months. No movement of oil down into the layers below 6 cm in the box was indicated. The concentration of methylnaphthalene, naphthalene and phenanthrene had not changed significantly (t-test, P> 0.05) in the top 3 cm of the sediment during the three-month exposure. The results from the experiments in the Raunefjord (Figure 6) showed a gradual reduction in total hydrocarbons from 18 000 ppm (dry weight) at the start to 1000-5000 ppm after nine months both at the surface of the sediment and in the depth interval l-2 cm (Figure 6A). However the analysis from March 1982 showed concentrations higher than in the boxes sampled in November 1981. The measured increase was more pronounced for the depth interval l-2 cm than for the surface. Below the oil-contaminated layer an increasein total hydrocarbon concentration wasfound at the end of the experiments in the 4-5 cm depth interval but not in the 7-8 cm interval (Figure 6B). All hydrocarbon components showed a decrease during the experimental period in the Raunefjord (Figure 7). Generally the reduction was more pronounced at the surface than in the l-2 cm layer (Figure 8). The reduction was more pronounced for the more water-soluble components (e.g. naphthalene and methylnaphthalene) than for the less water-soluble components (e.g. methylphenanthrene and phenanthrene) (Figure 8). After 13 months of exposure the concentration of the most soluble components was reduced by approximately two orders of magnitude and the lessersoluble components by approximately one order of magnitude (Figure 8). The ratios of n-C17/pristane and n-C18/phytane were calculated as an indication of biological or oxidative degradation. The ratios for the Oslofjord experiments are shown in Table 4 and for the Raunefjord in Figure 9. In the Oslofjord both the n-C17/n-Cl8 and
576
3. A. Berge, R. G. Lichtenthaler
& F. Oreld
:
0
0 0
0
I 4J
’ ’ ‘a&l’ FMAMJJAsoNDJFM
’
Time
Figure 6. The total concentration oil-contaminated boxes during the between the scale in Parts A and B. from l-2 cm. (B) n , depth interval
’
ol
‘=I
1
’
‘4
year
(ppm dry weight) of petroleum hydrocarbons in the experiments in the Raunefiord. Note the difference (A) 0, Top 5 mm of the sediment; 0, depth interval from 4-5 cm; 0, depth interval from 7-8 cm.
the pristane/phytane ratios as well as the n-C17/pristane ratio and the n-C18/phytane ratios were similar before and after exposure, thus indicating that no degradation had occurred. In the Raunefjord, the n-C17/n-Cl8 and the pristane/phytane ratios did not change discernibly during the experimental period. The n-C17/pristane and the n-C18/ phytane ratios, however, were significantly lower both in the surface and in the l-2 cm layer of the sediment in November 1981 and in March 1982. This reduction was most pronounced at the surface. Discussion Information on hydrocarbons in sediment has been summarized by Clark and MacLeod (1977). In general, unpolluted sediments have hydrocarbon levels below 70 ppm (dry weight) but considerably lower values are also reported (cf. Law & Androlewicz, 1983). Polluted sedimentsmay have hydrocarbon levels in the range 100-12 000 ppm. The initial hydrocarbon concentrations used in the present investigation (11000 ppm, 18 000 ppm) were at least 2-3 orders of magnitude higher than in sediment from areasnot subjected to oil spills, but were in the upper range found in contaminated sediment. A significant difference between boxes at the end of the experiments wasobserved in the Raunefjord implying that the physical, chemical and biological conditions or a combination of theseaffected the two types of sediment differently. Furthermore, conditions in the sediment are not independent, and observed differences between oiled and control sediment may have been causedby the oil directly or mediated through other parameters which were affected by the oil. Environment
The stable hydrographic conditions at the experimental site in the inner Oslofjord reflect a restricted water circulation caused by a narrow entrance and shallow (19.5 m) still. The
Depuration
in oil contaminated sediment
577
c
. .
n . 0
0
FMAMJJASONOJFM FMAMJJASONDJFM
Tim*
of
year
Figure 7. The concentration (ppm dry weight) of selected aromatic hydrocarbons during the experiments in the Raunefiord. (A) n , Naphthalene in the top 05 cm of the sediment; C!, naphthalene in the depth interval from l-2 cm; 0, methylnaphthalene, O-05 cm; C, , methylnaphthalene, l-2 cm. (B) n , Trimethylnaphthalene, O-05 cm; 0, trimethylnaphthalene, l-2 cm; l , dimethylnaphthalene, 045 cm; 0, dimethylnaphthalene, l-2 cm. (C) H, Methylphenanthrene, O-O.5 cm; CI, methylphenanthrene, l-2 cm; 0, phenanthrene, O-O.5 cm; 0, phenanthrene, 1-2 cm. (D) 0, Dimethylphenanthrene, 0-65 cm; 0, Dimethylphenanthrene, l-2 cm.
hydrographical conditions in the Raunefjord are more variable becauseof a sill depth of 150m, allowing more frequent exchange of water with the coastal current. The increasein the percentage of particles in the size ranged 500-1000 pm at the surface (O-l cm) in both treatments in the Raunefjord (Figure 2A) was probably a result of pelletization. The increased particle size in the control boxes near the sediment surface (O-l and l-2 cm) in the silt fraction (Figure 2B) may have been related to erodability and resuspension either by (1) differences in the form and density of polychaete tubes (Eckman et al., 1981; E&man & Nowell, 1984), or (2) differences in biological activity (bioturbation), or (3) differences in mucous binding of the sediment surface in control and oiled boxes. In June, both treatments in the Raunefjord had a high density of the tube building polychaete Polydora socialis,with its tubes totally embedded in the sediment and this may have stabilized the sediment. The density of P. socialis was, however, much reduced in November 1981 and March 1982 (Berge, in prep.). In November another
578
J. A. Berge,
R. G. Lichtenthaler
0.1
i
1
& F. Oreld
t
.
a phen
0
i2-..ph
‘,
3-naph
I-noph I
,
IOI
I
IIII
1 Solubility
1
,
10 (mg/l)
Figure 8. The ratio of the concentration of aromatic components plotted as a function of the compounds solubility in sea water: A, in November 1981 and at the start of the experiments (February 1981); B, in March 1982 and February 1981. Ratios in surface sediment (O-03 cm) are indicated with open symbols and the ratio in the l-2 cm depth interval with filled symbols. Note that the symbols for the values in the surface sediment and in the l-2 cm depth interval for the same component are joined with a vertical line. Naphthalene = naph, phenanthrene = phen. Number in front of abbreviation indicates degree of methylation.
polychaete, Oweniafusiformis, with tubes that protruded from the sediment, wasfound at a density of 245 m - ’ in the control boxes and only 15 m - 2in the oiled boxes. 0. fusiformis destabilizes sediment at similar densities to those found in the control boxes (E&man et al., 1981). Indication of bacterial degradation of oil was found in November (Figure 9). Bacteria may increaseparticle binding in the sediment and reduce erodability in the oiled boxes. All of the above mentioned factors, which could have facilitated resuspensionin the control boxes or reduced resuspension in the oil contaminated boxes, coincided with enhanced current velocities in November and December. Thus, a different resuspension rate was expected in the control and oiled boxes. It is therefore likely that the increased particle size in the silt fraction at the surface (O-2 cm) in the control boxes (Figure 2) was causedby increasedresuspensionof the finer particles. The carbon and nitrogen profiles found in the Raunefjord experiments (Figure 3) may be explained by two processeswhich are both facilitated in the control boxes. Either carbon and nitrogen compounds were biogenically consumed (fauna consumption, mineralization) or carbon and nitrogen were lost through resuspension from the bioturbated zone in the top layer of the sediment. We are not able to quantify the effect of each
Depuration
in oil contaminated sediment
Time
of
579
year
Figure 9. Concentration ratios of straight chain and branched Cl7 and Cl8 hydrocarbons in the oil-contaminated boxes at the sediment surface (A) and in the 1-2 cm depth interval (B) during the experimental period in the Raunefjord. 0, n-C17/n-C18; n, pristane/phythane; 0, n-C17/pristane; W, n-C18/phythane.
of thesetwo processeson the reduction in the carbon and nitrogen content. Small particles often have a higher content of organic matter than larger particles, as Cammen (1982) found in three out of four sediments. Organic material has a lower density than the bulk sediment and is thus more easily resuspended. In the control boxes where resuspension wasfacilitated, a reduced sediment content of carbon and nitrogen was found. Resuspension is operating from the sediment surface where the effect will be most pronounced. The effect of resuspensionmay, however, extend further down in the sediment in the control boxes becauseof an assumedhigher bioturbation rate (cf. Figure 5 and data on subsurface deposit feeders in the boxes). Nitrogen and carbon values were reduced only in the top 1 cm in the oil contaminated boxes and the values tended to converge at approximately 3-4 cm depth (Figure 3). This indicates that the bioturbated zone was shallower in the oiled boxes than in the control boxes. The lower redox potential found in the oiled boxes in this investigation (Figure 4) were due to (1) reduced bioturbation in the oiled boxes where a lower density of infauna was found, and (2) oxygen consumption through degradation of oil by aerobic bacteria. This study hasdemonstrated that oil contamination affects important sediment properties and that changesin sediment processessuch asbioturbation, resuspension,porewater exchange and mineralization were probably responsible for these changes. Several of the changesfound resemble those causedby organic enrichment (seePearson & Rosenberg, 1978) and have also been documented in the sediment near North Seaoil platforms (e.g. increased content of organic matter, negative redox potential (Addy et al., 1984).
580
3. A. Berge, R. G. Lichtenthaler
Total
oil
2
& F. Oreld
concentration
ppm
xl000
6
10
14
16
I
l
2 3
----------------
2
4 5
c P 0 0
1 2 3 4
-I----- 5
1 2 3 4 5
;-
-
-
-----
--;,
---_ I.+-46 % /c---------&
-’
/’
--
3 3 % _--c
D
l
-d
/(
1
Figure 10. A model for the profiles of the total hydrocarbon concentration in the oiled boxes based on individual measurements. (A): at the start of the experiment in February 1981; (B) June 1981;(C)November 1981; (D)March 1982. Thepercentageoilremaining in the sediment is indicated for each sampling date.
Hydrocarbon
content and composition
The oil-contaminated sediment originated from the samehomogenization batch which should have ensured a homogenous oil concentration at the start of the experiment (cf. Anderson et al., 1977). Occasional large deviations between replicate samples(seeJune measurementsin Figure 6) may result from local bioturbation of the sediment within a box, causing sediment from below the oiled layer to be brought to the top 3 cm. The total content of hydrocarbons in the depth interval from 1-2 cm appears to have increasedmarkedly from November 1981 to March 1982in the Raunefjord (Figure 6) and was unexpected. The increase in concentration was not caused by contamination from hydrocarbon sourcesoutside the boxes becausethe composition of the oil had not changed considerably. The increasewas most pronounced at the depth interval of l-2 cm and not at the surface aswould be expected if contamination originated from external sources.The most probable explanation for the total hydrocarbon increase found in March 1982, is the upward transport of crude oil from the 2-3 cm interval. Figure 10 shows a model of the assumedconcentration profiles in the sediment at each sampling, This model implies
Depuration
in oil contaminated sediment
581
that l/3 of the oil mixed into the top 3 cm of the sediment remains in the boxes after 13 months, that between November 1981 and March 1982 oil moved vertically from below the original O-2 cm depth interval into the l-2 cm depth interval, and that porewater and particle transport downwards from the contaminated top 3 cm is slow (cf. Figure 6B). Processeswhich facilitate aromatic depuration vary with depth in the sediment (Figures 7 and 8). In the Raunefjord, the time needed to reduce the concentration of naphthalene in the surface sediment and in the l-2 cm depth interval by two orders of magnitude was 330 and 390 days, respectively. This is a slower rate than found when oil is applied directly to the sediment surface in the intertidal but a faster rate than found for naphthalene when oil was mixed into the sediment (Andersen et al., 1978). The departure rates in the Raunefjord were alsofaster than those at 118 m depth on the Atlantic continental shelf of USA (Boesch et al., 1981). The lack of evidence for oil depuration from the Oslofjord sediment must be viewed in relation to the coarse depth intervals sampled (3 cm), exposure time (3 months) and potential factors which may limit depuration of hydrocarbons in the subtidal. Factors such as oxygen availability, nutrient supply (Atlas, 1981>, redox potential and pH (Delaune et al., 1980,1981), degreeof exposure (resuspension,sedimentationnear bottom currents) and organic carbon content. The sediment in all the experimental boxes in the Oslofjord was covered with a mat of tube-building polychaetes likely to causea reduction of the water exchange. This resulted in low redox potentials, reduced depuration by dissolution and reduced possibilities for bacterial degradation of hydrocarbons. Tubebuilding polychaetes (PoZydora socialis) were also present in the Raunefjord which did not, however, form dense mats on the sediment surface. Because solubility directly or indirectly determines the concentration change of aromatic compounds (Figure 8), dissolution rather than biodegradation was the most important process responsible for depuration of aromatic compounds. A tentative model for the kinetics of hydrocarbon depuration from low-energy intertidal sediment hasbeen proposed (Fusey & Oudot, 1984). In this model, depuration of oil is causedby physical removal and degradation. Physical removal starts immediately after contamination. Biodegradation on the other hand is considered not to be important before concentrations are below a certain threshold level of 400 ppm. Bacterial degradation in the Raunefjord sediment was demonstrated by the n-alkane/ branched alkane ratio after an initial lag period of 4-9 months (Figure 9). No further change in this ratio was detected after November 1981 in the surface sediment. In the 1-2 cm depth interval a slight increasein the ratio in March 82 ascompared to November 1981 was detected (Figure 9B). This may indicate that sediment with ‘ fresh ’ oil has emerged from below (cf. Figure 10). The larger reduction in the n-alkane/branched alkane ratio in the surface sediment suggeststhat bacterial degradation was greater here than deeper in the sediment. Thus as oil depuration is faster near the sediment surface, the threshold for oil-degradation is first recorded here. In the Raunefjord experiments the reduction in hydrocarbon concentration was detected on the first sampling (after 4 months), however, biodegradation was not detected before 9 months. The mean total hydrocarbon concentration after 9 months was 3000 ppm, thus the threshold for oil degradation in this study must have been one order of magnitude higher than suggested by Fusey & Oudot (1984). The concentrations used in these experiments were substantial. Hydrocarbon concentrations comparable with or higher than those applied in this investigation have been found both after accidental spills of crude oil (Berne et al., 1980) and in areassurrounding
582
J. A. Berge,
R. G. Lichtenthaler
& F. Oreld
North Sea oil platforms where oil based drilling mud have been used (Addy et al., 1984; Davis et al., 1984). In such areas significant effects on benthic communities are documented (sanders et al., 1980; Cabioch, 1980; Matheson et al., 1986). However, areas likely to receive such levels of contamination and be subjected to similar effects as documented in this investigation are not likely to be extensive.
Acknowledgements This investigation was funded by the Norwegian Marine Pollution Research and Monitoring Program (Project No. 203). The authors wish to thank Torleif Brattegard for the use of the facilities at the Department of Marine Biology, University of Bergen. We wish also to thank Terje Kleppe for performing and organizing excellent driving assistance during the experiments. Arnfinn Skadsheim and Hartvig Christie are acknowledged for their assistance during sampling and John S. Gray and Morten Schaanning for their comments on the manuscript.
References Addy,
J. M., Hartley, J. P. & Tibbetts, P. J. C. 1984 Ecological effects of low toxicity oil-based mud drilling in the Beatrice oilfield. Marine Pollution Bulletin, 15,429-436. Anderson, J. W., Moore, J. L., Blaylock, J. W., Woodruff, D. L. & Kiesser, S. L. 1977 Bioavailability of sediment-sorbed naphthalenes to the sipunculid worm, Phascolosoma agassizii. In Fate and EIfects of Petroleum in Marine Organisms and Ecosystems (Wolfe, D. A., ed.). Pergamon Press, New York, pp. 276-285. Anderson, J. W., Riley, R. G. &Bean, R. M. 1978 Recruitment of benthic animals as a function of petroleum hydrocarbon concentration in the sediment. Journal Fisheries Research Board of Canada 35,776-790. Atlas, R. M. 1981 Microbial degradation of petroleum hydrocarbons: an environmental perspective. Microbiological reviews 45,180-209. Bakke, T. & Johnsen, T. M. 1979 Response of a subtidal sediment community to low levels of oil hydrocarbons in a Norwegian fjord. In Proceedings of the 1979 Oil spill conference. (Ludwigson, J. O., ed.). American Petroleum Institute, Washington, DC, pp. 633-639. Bakke, T., Dale, T. & Thingstad, T. F. 1982 Structural and metabolic responses of a subtidal sediment community to water extracts of oil. NetherlandsJournal of Sea Research l&52&537. Berne, S., Marchand, M. & D’ozourille, L. 1980 Pollution of sea water and marine sediments in coastal areas. Ambio 9,287-293. Beslier, A., Birrien, J. L., Cabioch, L., Larsonneur, C & LeBorbne, L. 1980 La pollution des Baies de Morlaix et de Lannion par les hydrocarbures de 1’ ‘ Amoco Cadiz ‘: repartition sur les fonds et evolution. Helgolander Meeresuntersuchungen, 33,209-224. Blumer, M. St Sass, J. 1972 Oil pollution: persistence and degradation of spilled fuel oil. Science 176, 1120-1122. Boehm, P. D., Barak, J. E., Fiest, D. L. & Elskus, A. A. 1982 A chemical investigation of the transport and fate of petroleum hydrocarbons in littoral and benthic environments: the Tsesis oil spill. Marine Environmental Research 6,157-188. Boesch, D. F., Burreson, E. M., Schaffner, L. C., Kator, H. I., Smith, C. L., Alongi, D. M., Bowen, M. A. & deFur, I’. 0. 1981 Experimental colonization of crude oil contaminated sediments by benthos on the Middle Atlantic Continental Shelf. Virginia Institute of Marine Science. Report conducted under contract No. AA551-CT8-32 with the Bureau of Land Management United States Department of Interior. Cabioch, L. 1980 Pollution of subtidal sediments and disturbance of benthic animal communities. Ambio 9, 294-296. Cammen, L. M., 1982 Effect of particle size on organic content and microbial abundance within four marine sediments. Marine Ecology Progress Series 9,273-280. Clark Jr, R. C. & McLeod Jr, W. D. 1977 Inputs, transport mechanisms and observed concentrations of petroleum in marine environments. In Effects of Petroleum on Arctic and Sub-arctic Marine Environments and Organisms, Nature and Fate of Petroleum, Vol. 1, (Malins, D. C. ed). Academic Press, New York, 1977, p. 91.
Deputation
in oil contaminated
sediment
583
Davies, J. M., Addy, J. M., Blackman, R. A., Blanchard, J. R., Ferbrache, J. E., Moore, D. C., Sommerville, H. J., Whitehead, A. & Wilkinson, T. 1984 Environmental effects of the use of oil-based drilling muds in the North Sea. Marine Pollution Bulletin 15,363-370. Delaune, R. D., Hambrick, III, G. A. &Patrick, Jr., W. H. 1980 Degradation ofhydrocarbons in oxidized and reduced sediments. Marine Pollution Bulletin, 11,103-106. Delaune, R. D., Patrick, W. H. & Casselman, M. R. 1981 Effects of sediment pH and redox conditions on degredation of benzo(a)pyrene. Marine Pollution Bulletin, 12,251-253. Eckman, J. E. & Nowell, A. R. M. 1984 Boundary skin friction and sediment transport about an animal-tube mimic. Sedimentology 31,851-862. Eckman, J. E., Nowell, A. R. & Jumars, I’. A. 1981 Sediment destabilization by animal tubes. Journal of Marine Research, 39,361-374. Frithsen, J. B., Elmgren, R. & Rudnick, D. 1985 Responses of benthic meiofauna to long-term, low-level additions of No. 2 fuel oil. Marine Ecology Porogress Series, 23,1-14. Fusey, P. & Oudot, J. 1984 Relative influence of physical removal and biodegradation in the depuration of petroleum-contaminated seashore sediments. Marine Pollution Bulletin 15,13&141. Gaudette, H., Flight, W. R., Toner, L. & Folger, D. W. 1974 An inexpensive titration method for the determination of organic carbon in recent sediments. Journal of Sedimentary Petrology 44,249-253. Grassle, J. F., Elmgren, R. & Grassle, J. P. 1980 Response of benthic communities in MERL experimental ecosystem to low level, chronic addition of No. 2 fuel oil. Marine Environmental Research 4,279-297. Keizer, P. D., Ahern, T. P., Dale, J. & Vandermeulen, J. H. 1978 Residues of Bunker C oil in Chedabucto Bay, Nova Scotia, 6 years after the Arrow spill. Journal Fisheries Research Board Canada 35,528-535. Law, R. & Andrulewicz, E. 1983 Hydrocarbons in water, sediment and mussel from Southern Baltic Sea. Marine Pollution Bulletin, 14,289-293. Lichtenthaler, R. G. 1981 Instrumental analysis of petroleum hydrocarbons. In Proceedings of the first European symposium on the analysis of organic micropollutants in water, Berlin 1979 (Commission of the European Communities, ed.) Brussels, pp. 225-233. Lichtenthaler, R. G. & Oreld, F. 1983 Rapid high-performance liquid chromatographic method for hydrocarbon class separation in environmental samples. Journal of Chromatography, 282,501-507. Massie, L. C. Ward, A. P., Davies, J. M. & Mackie, P. R. 1985 The effects ofoil exploration and production in the Northern North Sea. Part 1. The level of hydrocarbons in water and sediments in selected areas, 1978-1981. Marine environmental Research 15, 165-213. Matheson, I., Kingston, P. F., Johnston, C. S. & Gibson, M. J. 1986 Statfjord field environmental study. In: NPF Seminar Proceedings Oil Based Drilling Fluids, Cleaning and Environmental Effects of Oil Contaminated Drill Cuttings. Throndheim (Noway), pp. 3-16. Mattsson, J. & Lehtinen, C. 1985 Increased levels of petroleum hydrocarbons in the surface sediments of Swedish coastal waters. Marine Pollution Bulletin, 16,390-395. Oudot, J. 1984 Rates of microbial degradation of petroleum components as determined by computerized capillary gas chromatography and computerized mass spectrometry. Marine Environmental Research 13, 277-302. Pearson, T. H. & Rosenberg, R. 1978 Macrobenthic succession in relation to organic enrichment and pollution of the marine environment. Oceanography and Marine Biology Annual Review 16,229-311. Sanders, H. L., Grassle, J. F., Hampson, G. R., Morse, L. S. &Garner-Price, S. 1980 Anatomy ofan oil spill: long term effects from the grounding of the barge Florida of West Falmouth, Massachusetts. Journal of Marine Research 38,265-380. Rhoads, D. C. 1979 Organism-sediment relations on the muddy floor. Oceanography and Marine Biology Annual Review 12,63-300. Teal, J. M. & Howarth, R. W. 1984 Oil spill studies: a review of ecological effects. Environmental management 8,27-44. Wade, T. L. & Quinn, J. G. 1980 Incorporation, distribution and fate of saturated petroleum hydrocarbons in sediments from a controlled marine ecosystem. Marine Environmental Research 3, 15-33.
Hydrocarbon Depuration and Abiotic Changes in Artificially Oil Contaminated Sediment in the Subtidal
John A. Berge”,‘, Freydis Oreld*
Rainer
G. Lichtenthaler”
and
“Biological Institute, Department of Marine Zoology and karine Chemistry, University of Oslo, P.B. 1064 Blindern, Oslo 3, Norway, and bCenter for Industrial Research, P.B. 350 Blindern, Oslo 3, Norway Received 7January
1985 and in revisedform 18Jme 1986
Keywords: Benthic environment, sediment parameters, bioturbation,
marine pollution, Norway
crude oil, degradation,
North Sea crude oil was mixed with sediment in concentrations similar to those found in heavily polluted areas (10 000 and 18 000 ppm) and placed in experimental boxes in the subtidal. Experiments were performed in two Norwegian fjords, the eutrophicated Oslofjord (experimental period of 3 months) and the non-eutrophicated Raunefiord (13 months). Physical and chemical responses of the contaminated sediment were compared with similarly treated control sediment without oil. Depuration was investigated using gas and liquid chromatographic analyses for determination of total hydrocarbon content and selected single aromatic components. Biodegradation was followed using n-alkane/ branched alkane ratios. No depuration or biodegradation of hydrocarbon, or pronounced changes in sediment nitrogen and carbon content were observed after exposure in the Oslofiord. In the Raunefjord the redox potential was reduced by 75-200 mV in the oil contaminated sediment after 9 and 13 months. In the control sediment nitrogen and carbon content were significantly reduced after 9 and 13 months but did not change in the oil contaminated sediment except at the sediment surface (O-l cm). A significantly higher macrofaunal biomass was found in the control sediment after 9 and 13 months but not after 5 months. After 13 months of exposure in the Raunefjord 3391~ of the originally added oil remained in the sediment. The most soluble components such as naphthalene and methylnaphthalene were reduced by two orders of magnitude and less soluble components such as phenanthrene and methyiphenanthrene by one order of magnitude. Reduction was most pronounced at the sediment surface. Biodegradation in the Raunefjord sediment was documented after an initial lag period of 4-9 months. It is suggested that lower bioturbation and resuspension rates are responsible for the reducing conditions and the conservation of carbon, nitrogen and particle size distribution in the oil contaminated sediment. Results found as a consequence of oil, resemble the effect of eutrophication. Observed differences between test and control sediment may be caused by ‘Present address: Norwegian Institute for Water Research, P.O. Box 333 Blindern, N-0314 Oslo 3, Norway. 567 0272-7714/87/040567+17803.00/0
0 1987 Academic Press Inc. (London) Limited
568
J. A. Berge, R. G. Lichtenthaler
&F.
Oreld
toxicity of the oil directly or may be mediatedthrough other parameterseffected by the oil. Only limited areasare likely to receivesuchhigh oil concentrationsasapplied in the presentstudy. However, when suchconcentrationsare presentthe effects on sedimentparametersare significant. Introduction As a consequenceof off-shore oil exploitation and accidental oil spills, much effort has been put into studies on the fate and effect of petroleum and petroleum products in the marine environment. Most studies have been performed after accidental oil spills with the main focus on possible effects in the intertidal. The subtidal, however, has not been so extensively investigated, even though petroleum hydrocarbons may also contaminate subtidal sediments both after accidental oil spills (Besliers et al., 1980; Sanders et al., 1980) and after the discharge of oil-based drilling mud in connection with off-shore drilling operations (Addy et al., 1984; Davies et al. 1984; Massie et al., 1985). Investigations after oil spills have shown that oil may enter the sediment adsorbed on detrital material or incorporated in faecal material by sedimentation (Wade & Quinn, 1980; Boehm et al., 1982) and increased levels of hydrocarbons in sediment have been documented as a consequenceof urban activities (Mattsson & Lehtinen, 1985). The presenceof hydrocarbons in sedimentsmay modify chemical, physical and biological processes(Bakke et al., 1982) and cause an increased mortality of benthic animals (Sanders et al., 1980; seealso review by Teal & Howarth, 1984). A problem in describing and evaluating the effects of oil in the marine environment by studying accidental oil spills is finding representative control sites (Keizer et al., 1978). This problem can be overcome with field experiments where known amounts of oil are added to sediment and chemical and biological changes are compared with similar prepared controls without oil. Experimental oiling of subtidal sediments has been performed in Norway (Bakke & Johnsen, 1979; Bakke et al., 1982), in the middle Atlantic continental shelf (Boesch et al., 1981) and in mesocosm experiments in Massachusetts, U.S.A. (Grassle et al., 1980, Frithsen et al., 1985). Information on chemical, physical and biological responsesof known concentrations of oil in subtidal sediments are, however, few. In the experiments presented here we attempt to stimulate a situation where crude oil in high quantities (see Clark & MacLeod, 1977) sufficient for at least partially defaunation of the sediment is introduced to the top layer of a subtidal sediment. We focus on the physical and chemical behaviour of the sediment contaminated, with special reference to the depuration of hydrocarbons from the sediment. Materials Experimental
and methods sites
A three-month experiment was performed on a subtidal (23 m depth) muddy sediment near Vassholmen in the eutrophicated inner Oslofjord and a 13-month experiment on a subtidal (20 m depth) area with shell sand near Eggholmene in the noneutrophicated part of Raunefjorden on the west coast of Norway (Figure 1). Sediments for the experiments were collected at the experimental site for the Oslofjord experiments and at approximately 20 m depth, 1.3 km from the experimental site in the Raunefjord experiment (Figure 1).
Depuration
I
100
569
in oil contaminated sediment
km
\
(BjfLKAIf)
/j:;.:.:
.
.
1
OSLOFJORDEN
I
I
::
Figure 1. A map of the southern half of Norway showing thelocationof theOslofiord(A) and the Raunefjord (B) and more detailed chart showing the experimental areas. 0, Position of the experimental sites; n , position of site from where the sediment for the experiments in the Raunefjord were collected.
Preparation
of boxes and sampling
The experiments were performed by placing oiled and unoiled sediment on the seafloor in experimental boxes of PVC (55 x 37 x 12 cm high). The boxes were divided into four compartments, each with a surface area of 0.05 m2. The boxes were first filled with a 7.5 cm layer of unoiled sediment treated in a cement mixer for 3-5 min and frozen to stabilize the sediment. An additional layer of 3 cm of sediment mixed with unweathered North Sea Crude oil was added on top of the frozen sediment layer. The oil and sediment were mixed in a cement mixer for 15min (seeTable 1 for mixing data). The control boxes were treated similarly but with unoiled sediment. After this treatment all boxes were frozen again in order to kill the fauna and to prevent washing out the top layer of the sediment when submerging in the sea.The boxes were equipped with a lid during placement on the sea bed. Sediments for chemical analysis were taken by SCUBA divers using cores (inner diameter 6 cm) (seeTable 2 for sampling scheme). After sampling, the boxes were taken
570
J. A. Berge,
TABLE
R. G. Lichtenthaler
1. Conditions
Site
& F. Oreld
for the preparation
of the oil contaminated
Amount of oil used (ml)
Amount of sediment used (1)
Temp (‘0
240 374
30 50
15-20 9-15
Oslofjord Raunefjord
TABLE 2. Sampling
date and number
top 3 cm of the sediment
Measured cont. (wet weight) @pm) 3920 4520
Measured cont. (dry weight) (wm) 9940 17795
of boxes sampled Oslofiord
Raunefjord
Start of experiments: Date No. of control boxes submerged No. of oiled boxes submerged
11.04.80 2 2
18.02.81 6 6
First sampling: Date No. of control boxes sampled No. of oiled boxes sampled
08.07.80 2 2
25.06.81 1 1
Second sampling: Date No. of control boxes sampled No. of oiled boxes sampled
11.11.81 2 2
Third sampling: Date No. of control boxes sampled No. of oiled boxes sampled
23.03.82 3 3
to the surface and the remaining sediment sieved for macrofauna. Sediment cores for chemical analysis of the Oslofjord experiments were sectioned at 3-cm intervals and from the Raunefjord experiments at l-cm intervals. In samples from the Raunefjord, hydrocarbon analyses were also carried out on the 04l.5 cm depth section. Particle size distribution For particles larger than 64 e the size distribution was determined gravimetrically after wet sieving. Particles smaller than 65 l.trn were analysed using a Coulter Counter. Twoway analysis of variance (ANOVA) was performed separately on the fraction of sediment (arcsine transformed) in each particle size interval (six intervals for the sand fraction and four for the silt fraction) for oiled and control boxes at three depth intervals. Nitrogen and carbon determination Organic carbon determinations were made by wet oxidation (Gaudette et al., 1974). Total carbon and nitrogen were analysed with a Carlo Erba model 1106 CHN elemental analyser. Inorganic carbon was estimated as the difference between total carbon and organic carbon and assumed to consist of calcium carbonate carbon.
Depuration
TABLE
571
in oil contaminated sediment
3. Chemical
composition
( y0 dry weight)
Total carbon ( yO) Total nitrogen (%) Organic carbon (%) Organic C/N ratio Sediment particles larger than 2 mm (%) Sediment particles smaller than 63 pm (%) Calcium carbonate (%)
of the sediment
used in the experiments
Oslofjord
Raunefiord
4.4 0.34 3.1 9.1 0.5 58.4 11.5
12.0 o-73 6.2 8.5 1.5 23.5 50.3
Redox determination
Redox potentials were recorded using platinum electrodes and a calomel reference electrode and a voltmeter. Readings were taken after 5 min of equilibration in the sediment. Electrodes were calibrated with Zobell’s redox buffer. Biomass
Biomass(formalin wet weight) was determined gravimetrically by weighing macrofauna retained on a 1-mm sieve (excluding bivalves) from each compartment of the boxes. Analysis of petroleum hydrocarbons Determination of total hydrocarbon content in the sediments was performed by gas chromatography (Lichtenthaler, 1981). The single component analyseswere performed using high performance liquid chromatography followed by high resolution gas chromatography of aliphatic and aromatic fractions (Lichtenthaler 8zOreld, 1983, omitting the saponification step). Ratios of the compounds n-C17, n-C18, pristane and phytane were calculated asa measureof biodegradation of oil (Blumer & Sass,1972).
Results Environment
Temperature and salinity were relatively stable during the Oslofjord experiments (7.4-7.9 “C and 31.3-31.4X+ respectively) compared to the Raunefjord experiments (4-14 “C and 23-34%0, respectively). Current velocities were obtained only in the Raunefjord where, 2 m above the bottom, the current did not exceed 14 cm s-r. Sediment composition values at the start of the experiments are shown in Table 3. Results from particle-size distribution analyses at the end of the experiments in the Raunefjord are shown in Figure 2. The ANOVA on the results from the size frequency analysis showed no significant (P> 0.05) effect of oil treatment on the sand fraction. The only significant (P
572
J. A. Berge,
R. G. Lichtenthaler
O-l
& F. Oreld
l-2cm
cm
4-5cm
4
63
250 125
1000 500
: ::: 4 . .,.’ . . ‘: . . .. ‘:. : ::. __ . :: .-I. . ... . ‘, .,. ..: : ..:.. : . . ... 1::“.. :; .i., S...’
.. :*... . ;,.l . .. i . :* . ., 1.; :: . :f,.. .a.. 11.’ . .-” . * .: * :. :!> i, 63
.,Y; . . .. ,*. ,,.’ .,.‘) . ::.-. ..“.’ ; : :: . . :T’. . . >.z:: .._. ::*: . ‘.‘.‘: .:.*.. . I.. 250 1000 125 500 2000
2000 Sieve
mesh
63
250 125
1000 500
2000
(pm)
30
20
10
4
6
4
163264 Part!
6 cle
16
32
4
64
diameter
6
163264
(pm)
Figure 2. Results from particle-size distribution anaIysis at three depth intervals in the sediment at the end of the experiment in the Raunefjord. (A) Mean percentage of sediment weight in each particle-size interval for the sand fraction. (B) Mean percentage of sediment volume in each particle-size interval for the silt fraction. Stippled columns = percentage in control boxes; blank columns =percentage in oiled boxes exceeding values in control boxes. Height of blank column is indicated with a horizontal line when percentage in control exceeds values in oiled boxes.
control boxes as a result of a reduction in the particle volume in the 4-8 urn interval and an increase in the 32-64 urn interval. In the Oslofiord the mean total carbon content in the top 3 cm of the sediment was 4.74, in the oiled boxes and 4.3:/, in the control boxes. At the two other depth intervals the carbon content was almost identical and not significantly different from the level found in the sediment when preparing the boxes (4,40/o). The nitrogen content in the sediment was not significantly reduced during the experimental period in the Oslofjord and there was no significant (paired t-test, P>O.O5) difference between nitrogen content in oiled and control sediment at the end of the experiments. In the Raunefjord, the content of total carbon in the sediment at the end of the experiments (Figure 3) were significantly lower (paired t-test, P < 0.05) in the control boxes than in the oiled boxes. This difference was most pronounced for the depth intervals l-2 and 2-3 cm where there was a significant (t-test, P< 0.05) difference between the mean carbon contents in control and oiled boxes. The content of total carbon in both control and oiled
Depuration
in oil contaminated sediment
o/O 10
Carbon 11
573
o/o (2
13
0.2
0.4
Nitrogen
o/o
0.6
0.0
60
water 70
60
Figure 3. Sediment profiles showing the percentage of total carbon, total nitrogen and water contents in the boxes prior to (A) and after (B) exposure for the experiments performed in the Raunefjord. A horizontal bar indicates + 1 standard deviation (SD) of the mean. On the depth axis ‘ s ’ indicates a significant (PC 0.05) difference between percentage in oiled (0) and control boxes (0). Note that in (B), SDS are only indicated when larger than the radius of the symbol.
4. Concentration ratios of straight chain and branched Cl 7 and Cl8 hydrocarbons in oil-contaminated sediment prior to and after exposure in the Oslofjord
TABLE
n-Cl?/n-Cl8 Pristane/phytane n-C17/pristane n-Cl8/phytane
Before
After
1.08 1.20 1.43 1.59
1.10 1.27 1.37 1.56
boxes was reduced from an initial value of 12.7”, to approximately 9.5’,, in the top 1 cm of the sediment. At other depth intervals the reduction was not so dramatic. In the Raunefjord experiments 49% of the total carbon in the sediment (Table 3) was organic. Organic carbon was measured only at the start and at the end of the experiments in the depth interval l-2 cm in both the control and the oiled boxes. During the experimental period of 13 months the organic carbon in this depth interval fell from 6.17 to 5 I ‘Iq) (reduction= l.OF,,) in the control boxes. The reduction in the total carbon content in the sameperiod was 1.37”,, in the l-2 cm depth interval, thus 78O, of the reduction in carbon content in this depth interval in the control boxes wascausedby a reduction in the organic fraction. In the oiled boxes the reduction in the total carbon was from 12.71O0at the start of the experiment to 12.24”,, at the end of the experiment (reduction = 0.47”,,). The organic
574
J. A. Berge, R. G. Lichtenthaler
Redox
0 L% . .c “, ‘-
I
(mV)
,’
^
4
B
--
$2 3-
potentiol
& F. Ore/d
l-o-4
4-567-
-
Figure 4. Redox potential measurements in sediment from the experiments Raunefiord in November 1981 (A) and March 1982 (B). 0, Control boxes; boxes. Horizontal bar indicates f 1 SD (n = 4-6).
in the 0, oiled
carbon content at the start of the experiment in the oiled boxes was 6.74%, but had increased to 7+3% at the end of the experiment. In the Raunefiord experiments total nitrogen (Figure 3) followed the trend for total carbon, with a significant (paired t-test, P< 0.05) lower nitrogen content in the control boxes than in the oiled boxes. This difference wasmost pronounced in the depth intervals of 2-3 and 3-4 cm. A pronounced reduction in nitrogen from the initial O.7-O%o/0to 0.28O/, for the control sediment and 0.4% for the oiled sediment at the end of the experiments in the top O-l cm was measured. Deeper in the sediment the percentage nitrogen was unchanged in the oiled boxes but was significantly reduced in the control boxes. In both experiments there was a significantly (paired r-test, P< 0.05) higher water content in the oiled sediment than in the control sediment. Comparing each depth interval separately reveals that, at the end of the Raunefiord experiments, there was no significant difference between water content in the oiled and the control boxes at O-l and l-2 cm depth intervals. However, there wasa significant difference (t-test, P < 0.05) deeper in the sediment (seeFigure 3). There was a significant difference (t-test, P< 0.05) in redox potential at all measured depths in the oiled sediment in the Raunefjord both in November and March 1982 (Figure 4). The difference between readings in oiled and control boxes are in the range 75-200 mV. Both control and oiled boxes in the Oslofjord were colonized with speciestypical for an eutrophicated fiord; Polydora ciliata dominated and there were few clear negative effects of oil on the fauna. In the Raunetjord experiments, however, there wasa clear decreasein the number of species, individual densities of most speciesand biomass (Figure 5) in November 1981 and March 1982.
Depuration
d
575
in oil contaminated sediment
I
I
I
I
I
I
I
I
I
I
I
IQ
i
FMAMJJASONDJFM Time
of year
Figure 5. Mean macrofaunal biomass (formalin wet weight excluded bivalves) per compartment (0.05 m*) in control (0) and oiled boxes (0) from the Raunefjord experiments. Vertical bar indicates If: 1 SD.
Hydrocarbon
content and composition
The total concentration of hydrocarbons in the top 3 cm of the sediment did not change significntly during the experimental period in the Oslofjord, mean values being 9940 ppm (SD = 1190) (dry weight) at the start and 11560ppm (SD=470) after three months. No movement of oil down into the layers below 6 cm in the box was indicated. The concentration of methylnaphthalene, naphthalene and phenanthrene had not changed significantly (t-test, P> 0.05) in the top 3 cm of the sediment during the three-month exposure. The results from the experiments in the Raunefjord (Figure 6) showed a gradual reduction in total hydrocarbons from 18 000 ppm (dry weight) at the start to 1000-5000 ppm after nine months both at the surface of the sediment and in the depth interval l-2 cm (Figure 6A). However the analysis from March 1982 showed concentrations higher than in the boxes sampled in November 1981. The measured increase was more pronounced for the depth interval l-2 cm than for the surface. Below the oil-contaminated layer an increasein total hydrocarbon concentration wasfound at the end of the experiments in the 4-5 cm depth interval but not in the 7-8 cm interval (Figure 6B). All hydrocarbon components showed a decrease during the experimental period in the Raunefjord (Figure 7). Generally the reduction was more pronounced at the surface than in the l-2 cm layer (Figure 8). The reduction was more pronounced for the more water-soluble components (e.g. naphthalene and methylnaphthalene) than for the less water-soluble components (e.g. methylphenanthrene and phenanthrene) (Figure 8). After 13 months of exposure the concentration of the most soluble components was reduced by approximately two orders of magnitude and the lessersoluble components by approximately one order of magnitude (Figure 8). The ratios of n-C17/pristane and n-C18/phytane were calculated as an indication of biological or oxidative degradation. The ratios for the Oslofjord experiments are shown in Table 4 and for the Raunefjord in Figure 9. In the Oslofjord both the n-C17/n-Cl8 and
576
3. A. Berge, R. G. Lichtenthaler
& F. Oreld
:
0
0 0
0
I 4J
’ ’ ‘a&l’ FMAMJJAsoNDJFM
’
Time
Figure 6. The total concentration oil-contaminated boxes during the between the scale in Parts A and B. from l-2 cm. (B) n , depth interval
’
ol
‘=I
1
’
‘4
year
(ppm dry weight) of petroleum hydrocarbons in the experiments in the Raunefiord. Note the difference (A) 0, Top 5 mm of the sediment; 0, depth interval from 4-5 cm; 0, depth interval from 7-8 cm.
the pristane/phytane ratios as well as the n-C17/pristane ratio and the n-C18/phytane ratios were similar before and after exposure, thus indicating that no degradation had occurred. In the Raunefjord, the n-C17/n-Cl8 and the pristane/phytane ratios did not change discernibly during the experimental period. The n-C17/pristane and the n-C18/ phytane ratios, however, were significantly lower both in the surface and in the l-2 cm layer of the sediment in November 1981 and in March 1982. This reduction was most pronounced at the surface. Discussion Information on hydrocarbons in sediment has been summarized by Clark and MacLeod (1977). In general, unpolluted sediments have hydrocarbon levels below 70 ppm (dry weight) but considerably lower values are also reported (cf. Law & Androlewicz, 1983). Polluted sedimentsmay have hydrocarbon levels in the range 100-12 000 ppm. The initial hydrocarbon concentrations used in the present investigation (11000 ppm, 18 000 ppm) were at least 2-3 orders of magnitude higher than in sediment from areasnot subjected to oil spills, but were in the upper range found in contaminated sediment. A significant difference between boxes at the end of the experiments wasobserved in the Raunefjord implying that the physical, chemical and biological conditions or a combination of theseaffected the two types of sediment differently. Furthermore, conditions in the sediment are not independent, and observed differences between oiled and control sediment may have been causedby the oil directly or mediated through other parameters which were affected by the oil. Environment
The stable hydrographic conditions at the experimental site in the inner Oslofjord reflect a restricted water circulation caused by a narrow entrance and shallow (19.5 m) still. The
Depuration
in oil contaminated sediment
577
c
. .
n . 0
0
FMAMJJASONOJFM FMAMJJASONDJFM
Tim*
of
year
Figure 7. The concentration (ppm dry weight) of selected aromatic hydrocarbons during the experiments in the Raunefiord. (A) n , Naphthalene in the top 05 cm of the sediment; C!, naphthalene in the depth interval from l-2 cm; 0, methylnaphthalene, O-05 cm; C, , methylnaphthalene, l-2 cm. (B) n , Trimethylnaphthalene, O-05 cm; 0, trimethylnaphthalene, l-2 cm; l , dimethylnaphthalene, 045 cm; 0, dimethylnaphthalene, l-2 cm. (C) H, Methylphenanthrene, O-O.5 cm; CI, methylphenanthrene, l-2 cm; 0, phenanthrene, O-O.5 cm; 0, phenanthrene, 1-2 cm. (D) 0, Dimethylphenanthrene, 0-65 cm; 0, Dimethylphenanthrene, l-2 cm.
hydrographical conditions in the Raunefjord are more variable becauseof a sill depth of 150m, allowing more frequent exchange of water with the coastal current. The increasein the percentage of particles in the size ranged 500-1000 pm at the surface (O-l cm) in both treatments in the Raunefjord (Figure 2A) was probably a result of pelletization. The increased particle size in the control boxes near the sediment surface (O-l and l-2 cm) in the silt fraction (Figure 2B) may have been related to erodability and resuspension either by (1) differences in the form and density of polychaete tubes (Eckman et al., 1981; E&man & Nowell, 1984), or (2) differences in biological activity (bioturbation), or (3) differences in mucous binding of the sediment surface in control and oiled boxes. In June, both treatments in the Raunefjord had a high density of the tube building polychaete Polydora socialis,with its tubes totally embedded in the sediment and this may have stabilized the sediment. The density of P. socialis was, however, much reduced in November 1981 and March 1982 (Berge, in prep.). In November another
578
J. A. Berge,
R. G. Lichtenthaler
0.1
i
1
& F. Oreld
t
.
a phen
0
i2-..ph
‘,
3-naph
I-noph I
,
IOI
I
IIII
1 Solubility
1
,
10 (mg/l)
Figure 8. The ratio of the concentration of aromatic components plotted as a function of the compounds solubility in sea water: A, in November 1981 and at the start of the experiments (February 1981); B, in March 1982 and February 1981. Ratios in surface sediment (O-03 cm) are indicated with open symbols and the ratio in the l-2 cm depth interval with filled symbols. Note that the symbols for the values in the surface sediment and in the l-2 cm depth interval for the same component are joined with a vertical line. Naphthalene = naph, phenanthrene = phen. Number in front of abbreviation indicates degree of methylation.
polychaete, Oweniafusiformis, with tubes that protruded from the sediment, wasfound at a density of 245 m - ’ in the control boxes and only 15 m - 2in the oiled boxes. 0. fusiformis destabilizes sediment at similar densities to those found in the control boxes (E&man et al., 1981). Indication of bacterial degradation of oil was found in November (Figure 9). Bacteria may increaseparticle binding in the sediment and reduce erodability in the oiled boxes. All of the above mentioned factors, which could have facilitated resuspensionin the control boxes or reduced resuspension in the oil contaminated boxes, coincided with enhanced current velocities in November and December. Thus, a different resuspension rate was expected in the control and oiled boxes. It is therefore likely that the increased particle size in the silt fraction at the surface (O-2 cm) in the control boxes (Figure 2) was causedby increasedresuspensionof the finer particles. The carbon and nitrogen profiles found in the Raunefjord experiments (Figure 3) may be explained by two processeswhich are both facilitated in the control boxes. Either carbon and nitrogen compounds were biogenically consumed (fauna consumption, mineralization) or carbon and nitrogen were lost through resuspension from the bioturbated zone in the top layer of the sediment. We are not able to quantify the effect of each
Depuration
in oil contaminated sediment
Time
of
579
year
Figure 9. Concentration ratios of straight chain and branched Cl7 and Cl8 hydrocarbons in the oil-contaminated boxes at the sediment surface (A) and in the 1-2 cm depth interval (B) during the experimental period in the Raunefjord. 0, n-C17/n-C18; n, pristane/phythane; 0, n-C17/pristane; W, n-C18/phythane.
of thesetwo processeson the reduction in the carbon and nitrogen content. Small particles often have a higher content of organic matter than larger particles, as Cammen (1982) found in three out of four sediments. Organic material has a lower density than the bulk sediment and is thus more easily resuspended. In the control boxes where resuspension wasfacilitated, a reduced sediment content of carbon and nitrogen was found. Resuspension is operating from the sediment surface where the effect will be most pronounced. The effect of resuspensionmay, however, extend further down in the sediment in the control boxes becauseof an assumedhigher bioturbation rate (cf. Figure 5 and data on subsurface deposit feeders in the boxes). Nitrogen and carbon values were reduced only in the top 1 cm in the oil contaminated boxes and the values tended to converge at approximately 3-4 cm depth (Figure 3). This indicates that the bioturbated zone was shallower in the oiled boxes than in the control boxes. The lower redox potential found in the oiled boxes in this investigation (Figure 4) were due to (1) reduced bioturbation in the oiled boxes where a lower density of infauna was found, and (2) oxygen consumption through degradation of oil by aerobic bacteria. This study hasdemonstrated that oil contamination affects important sediment properties and that changesin sediment processessuch asbioturbation, resuspension,porewater exchange and mineralization were probably responsible for these changes. Several of the changesfound resemble those causedby organic enrichment (seePearson & Rosenberg, 1978) and have also been documented in the sediment near North Seaoil platforms (e.g. increased content of organic matter, negative redox potential (Addy et al., 1984).
580
3. A. Berge, R. G. Lichtenthaler
Total
oil
2
& F. Oreld
concentration
ppm
xl000
6
10
14
16
I
l
2 3
----------------
2
4 5
c P 0 0
1 2 3 4
-I----- 5
1 2 3 4 5
;-
-
-
-----
--;,
---_ I.+-46 % /c---------&
-’
/’
--
3 3 % _--c
D
l
-d
/(
1
Figure 10. A model for the profiles of the total hydrocarbon concentration in the oiled boxes based on individual measurements. (A): at the start of the experiment in February 1981; (B) June 1981;(C)November 1981; (D)March 1982. Thepercentageoilremaining in the sediment is indicated for each sampling date.
Hydrocarbon
content and composition
The oil-contaminated sediment originated from the samehomogenization batch which should have ensured a homogenous oil concentration at the start of the experiment (cf. Anderson et al., 1977). Occasional large deviations between replicate samples(seeJune measurementsin Figure 6) may result from local bioturbation of the sediment within a box, causing sediment from below the oiled layer to be brought to the top 3 cm. The total content of hydrocarbons in the depth interval from 1-2 cm appears to have increasedmarkedly from November 1981 to March 1982in the Raunefjord (Figure 6) and was unexpected. The increase in concentration was not caused by contamination from hydrocarbon sourcesoutside the boxes becausethe composition of the oil had not changed considerably. The increasewas most pronounced at the depth interval of l-2 cm and not at the surface aswould be expected if contamination originated from external sources.The most probable explanation for the total hydrocarbon increase found in March 1982, is the upward transport of crude oil from the 2-3 cm interval. Figure 10 shows a model of the assumedconcentration profiles in the sediment at each sampling, This model implies
Depuration
in oil contaminated sediment
581
that l/3 of the oil mixed into the top 3 cm of the sediment remains in the boxes after 13 months, that between November 1981 and March 1982 oil moved vertically from below the original O-2 cm depth interval into the l-2 cm depth interval, and that porewater and particle transport downwards from the contaminated top 3 cm is slow (cf. Figure 6B). Processeswhich facilitate aromatic depuration vary with depth in the sediment (Figures 7 and 8). In the Raunefjord, the time needed to reduce the concentration of naphthalene in the surface sediment and in the l-2 cm depth interval by two orders of magnitude was 330 and 390 days, respectively. This is a slower rate than found when oil is applied directly to the sediment surface in the intertidal but a faster rate than found for naphthalene when oil was mixed into the sediment (Andersen et al., 1978). The departure rates in the Raunefjord were alsofaster than those at 118 m depth on the Atlantic continental shelf of USA (Boesch et al., 1981). The lack of evidence for oil depuration from the Oslofjord sediment must be viewed in relation to the coarse depth intervals sampled (3 cm), exposure time (3 months) and potential factors which may limit depuration of hydrocarbons in the subtidal. Factors such as oxygen availability, nutrient supply (Atlas, 1981>, redox potential and pH (Delaune et al., 1980,1981), degreeof exposure (resuspension,sedimentationnear bottom currents) and organic carbon content. The sediment in all the experimental boxes in the Oslofjord was covered with a mat of tube-building polychaetes likely to causea reduction of the water exchange. This resulted in low redox potentials, reduced depuration by dissolution and reduced possibilities for bacterial degradation of hydrocarbons. Tubebuilding polychaetes (PoZydora socialis) were also present in the Raunefjord which did not, however, form dense mats on the sediment surface. Because solubility directly or indirectly determines the concentration change of aromatic compounds (Figure 8), dissolution rather than biodegradation was the most important process responsible for depuration of aromatic compounds. A tentative model for the kinetics of hydrocarbon depuration from low-energy intertidal sediment hasbeen proposed (Fusey & Oudot, 1984). In this model, depuration of oil is causedby physical removal and degradation. Physical removal starts immediately after contamination. Biodegradation on the other hand is considered not to be important before concentrations are below a certain threshold level of 400 ppm. Bacterial degradation in the Raunefjord sediment was demonstrated by the n-alkane/ branched alkane ratio after an initial lag period of 4-9 months (Figure 9). No further change in this ratio was detected after November 1981 in the surface sediment. In the 1-2 cm depth interval a slight increasein the ratio in March 82 ascompared to November 1981 was detected (Figure 9B). This may indicate that sediment with ‘ fresh ’ oil has emerged from below (cf. Figure 10). The larger reduction in the n-alkane/branched alkane ratio in the surface sediment suggeststhat bacterial degradation was greater here than deeper in the sediment. Thus as oil depuration is faster near the sediment surface, the threshold for oil-degradation is first recorded here. In the Raunefjord experiments the reduction in hydrocarbon concentration was detected on the first sampling (after 4 months), however, biodegradation was not detected before 9 months. The mean total hydrocarbon concentration after 9 months was 3000 ppm, thus the threshold for oil degradation in this study must have been one order of magnitude higher than suggested by Fusey & Oudot (1984). The concentrations used in these experiments were substantial. Hydrocarbon concentrations comparable with or higher than those applied in this investigation have been found both after accidental spills of crude oil (Berne et al., 1980) and in areassurrounding
582
J. A. Berge,
R. G. Lichtenthaler
& F. Oreld
North Sea oil platforms where oil based drilling mud have been used (Addy et al., 1984; Davis et al., 1984). In such areas significant effects on benthic communities are documented (sanders et al., 1980; Cabioch, 1980; Matheson et al., 1986). However, areas likely to receive such levels of contamination and be subjected to similar effects as documented in this investigation are not likely to be extensive.
Acknowledgements This investigation was funded by the Norwegian Marine Pollution Research and Monitoring Program (Project No. 203). The authors wish to thank Torleif Brattegard for the use of the facilities at the Department of Marine Biology, University of Bergen. We wish also to thank Terje Kleppe for performing and organizing excellent driving assistance during the experiments. Arnfinn Skadsheim and Hartvig Christie are acknowledged for their assistance during sampling and John S. Gray and Morten Schaanning for their comments on the manuscript.
References Addy,
J. M., Hartley, J. P. & Tibbetts, P. J. C. 1984 Ecological effects of low toxicity oil-based mud drilling in the Beatrice oilfield. Marine Pollution Bulletin, 15,429-436. Anderson, J. W., Moore, J. L., Blaylock, J. W., Woodruff, D. L. & Kiesser, S. L. 1977 Bioavailability of sediment-sorbed naphthalenes to the sipunculid worm, Phascolosoma agassizii. In Fate and EIfects of Petroleum in Marine Organisms and Ecosystems (Wolfe, D. A., ed.). Pergamon Press, New York, pp. 276-285. Anderson, J. W., Riley, R. G. &Bean, R. M. 1978 Recruitment of benthic animals as a function of petroleum hydrocarbon concentration in the sediment. Journal Fisheries Research Board of Canada 35,776-790. Atlas, R. M. 1981 Microbial degradation of petroleum hydrocarbons: an environmental perspective. Microbiological reviews 45,180-209. Bakke, T. & Johnsen, T. M. 1979 Response of a subtidal sediment community to low levels of oil hydrocarbons in a Norwegian fjord. In Proceedings of the 1979 Oil spill conference. (Ludwigson, J. O., ed.). American Petroleum Institute, Washington, DC, pp. 633-639. Bakke, T., Dale, T. & Thingstad, T. F. 1982 Structural and metabolic responses of a subtidal sediment community to water extracts of oil. NetherlandsJournal of Sea Research l&52&537. Berne, S., Marchand, M. & D’ozourille, L. 1980 Pollution of sea water and marine sediments in coastal areas. Ambio 9,287-293. Beslier, A., Birrien, J. L., Cabioch, L., Larsonneur, C & LeBorbne, L. 1980 La pollution des Baies de Morlaix et de Lannion par les hydrocarbures de 1’ ‘ Amoco Cadiz ‘: repartition sur les fonds et evolution. Helgolander Meeresuntersuchungen, 33,209-224. Blumer, M. St Sass, J. 1972 Oil pollution: persistence and degradation of spilled fuel oil. Science 176, 1120-1122. Boehm, P. D., Barak, J. E., Fiest, D. L. & Elskus, A. A. 1982 A chemical investigation of the transport and fate of petroleum hydrocarbons in littoral and benthic environments: the Tsesis oil spill. Marine Environmental Research 6,157-188. Boesch, D. F., Burreson, E. M., Schaffner, L. C., Kator, H. I., Smith, C. L., Alongi, D. M., Bowen, M. A. & deFur, I’. 0. 1981 Experimental colonization of crude oil contaminated sediments by benthos on the Middle Atlantic Continental Shelf. Virginia Institute of Marine Science. Report conducted under contract No. AA551-CT8-32 with the Bureau of Land Management United States Department of Interior. Cabioch, L. 1980 Pollution of subtidal sediments and disturbance of benthic animal communities. Ambio 9, 294-296. Cammen, L. M., 1982 Effect of particle size on organic content and microbial abundance within four marine sediments. Marine Ecology Progress Series 9,273-280. Clark Jr, R. C. & McLeod Jr, W. D. 1977 Inputs, transport mechanisms and observed concentrations of petroleum in marine environments. In Effects of Petroleum on Arctic and Sub-arctic Marine Environments and Organisms, Nature and Fate of Petroleum, Vol. 1, (Malins, D. C. ed). Academic Press, New York, 1977, p. 91.
Deputation
in oil contaminated
sediment
583
Davies, J. M., Addy, J. M., Blackman, R. A., Blanchard, J. R., Ferbrache, J. E., Moore, D. C., Sommerville, H. J., Whitehead, A. & Wilkinson, T. 1984 Environmental effects of the use of oil-based drilling muds in the North Sea. Marine Pollution Bulletin 15,363-370. Delaune, R. D., Hambrick, III, G. A. &Patrick, Jr., W. H. 1980 Degradation ofhydrocarbons in oxidized and reduced sediments. Marine Pollution Bulletin, 11,103-106. Delaune, R. D., Patrick, W. H. & Casselman, M. R. 1981 Effects of sediment pH and redox conditions on degredation of benzo(a)pyrene. Marine Pollution Bulletin, 12,251-253. Eckman, J. E. & Nowell, A. R. M. 1984 Boundary skin friction and sediment transport about an animal-tube mimic. Sedimentology 31,851-862. Eckman, J. E., Nowell, A. R. & Jumars, I’. A. 1981 Sediment destabilization by animal tubes. Journal of Marine Research, 39,361-374. Frithsen, J. B., Elmgren, R. & Rudnick, D. 1985 Responses of benthic meiofauna to long-term, low-level additions of No. 2 fuel oil. Marine Ecology Porogress Series, 23,1-14. Fusey, P. & Oudot, J. 1984 Relative influence of physical removal and biodegradation in the depuration of petroleum-contaminated seashore sediments. Marine Pollution Bulletin 15,13&141. Gaudette, H., Flight, W. R., Toner, L. & Folger, D. W. 1974 An inexpensive titration method for the determination of organic carbon in recent sediments. Journal of Sedimentary Petrology 44,249-253. Grassle, J. F., Elmgren, R. & Grassle, J. P. 1980 Response of benthic communities in MERL experimental ecosystem to low level, chronic addition of No. 2 fuel oil. Marine Environmental Research 4,279-297. Keizer, P. D., Ahern, T. P., Dale, J. & Vandermeulen, J. H. 1978 Residues of Bunker C oil in Chedabucto Bay, Nova Scotia, 6 years after the Arrow spill. Journal Fisheries Research Board Canada 35,528-535. Law, R. & Andrulewicz, E. 1983 Hydrocarbons in water, sediment and mussel from Southern Baltic Sea. Marine Pollution Bulletin, 14,289-293. Lichtenthaler, R. G. 1981 Instrumental analysis of petroleum hydrocarbons. In Proceedings of the first European symposium on the analysis of organic micropollutants in water, Berlin 1979 (Commission of the European Communities, ed.) Brussels, pp. 225-233. Lichtenthaler, R. G. & Oreld, F. 1983 Rapid high-performance liquid chromatographic method for hydrocarbon class separation in environmental samples. Journal of Chromatography, 282,501-507. Massie, L. C. Ward, A. P., Davies, J. M. & Mackie, P. R. 1985 The effects ofoil exploration and production in the Northern North Sea. Part 1. The level of hydrocarbons in water and sediments in selected areas, 1978-1981. Marine environmental Research 15, 165-213. Matheson, I., Kingston, P. F., Johnston, C. S. & Gibson, M. J. 1986 Statfjord field environmental study. In: NPF Seminar Proceedings Oil Based Drilling Fluids, Cleaning and Environmental Effects of Oil Contaminated Drill Cuttings. Throndheim (Noway), pp. 3-16. Mattsson, J. & Lehtinen, C. 1985 Increased levels of petroleum hydrocarbons in the surface sediments of Swedish coastal waters. Marine Pollution Bulletin, 16,390-395. Oudot, J. 1984 Rates of microbial degradation of petroleum components as determined by computerized capillary gas chromatography and computerized mass spectrometry. Marine Environmental Research 13, 277-302. Pearson, T. H. & Rosenberg, R. 1978 Macrobenthic succession in relation to organic enrichment and pollution of the marine environment. Oceanography and Marine Biology Annual Review 16,229-311. Sanders, H. L., Grassle, J. F., Hampson, G. R., Morse, L. S. &Garner-Price, S. 1980 Anatomy ofan oil spill: long term effects from the grounding of the barge Florida of West Falmouth, Massachusetts. Journal of Marine Research 38,265-380. Rhoads, D. C. 1979 Organism-sediment relations on the muddy floor. Oceanography and Marine Biology Annual Review 12,63-300. Teal, J. M. & Howarth, R. W. 1984 Oil spill studies: a review of ecological effects. Environmental management 8,27-44. Wade, T. L. & Quinn, J. G. 1980 Incorporation, distribution and fate of saturated petroleum hydrocarbons in sediments from a controlled marine ecosystem. Marine Environmental Research 3, 15-33.