Hydrocarbon Concentrations In Sediments Research Articles

STATISTICAL APPROACH TO ESTIMATING REGIONAL BACKGROUND CONCENTRATIONS OF PETROLEUM HYDROCARBONS IN SEDIMENTS

Modern approaches to environmental regulation require that regional background concentrations of pollutants in environmental objects are set to serve as the basis for an objective assessment of the geoecological situation at a certain spatial level using monitoring data. The determination of the regional background levels of pollutants in sediments is particularly relevant due to the lack of matching sanitary standards for their permissible concentrations in the Russian Federation. Petroleum hydrocarbons, being structural components of natural organic matter, enter water bodies also from anthropogenic sources. Their accumulation in sediments leads to secondary water pollution and alteration of the structural and functional characteristics of the aquatic ecosystems. The natural component of petroleum hydrocarbons must be taken into account when determining their background levels in sediments. Based on representative material and using a statistical approach, the background concentrations of petroleum hydrocarbons in sediments of rivers, storage reservoirs and lakes of the Republic of Tatarstan were calculated. The structure of the variability in the content of petroleum hydrocarbons in the sediments is represented by the ratio of three factors: the hydrological conditions, organic matter content, and the particle size distribution (the pelite fraction content) of the sediments. The baseline value of the background concentration of petroleum hydrocarbons in sediments of water bodies in the Republic of Tatarstan is the median of the series, and its upper quartile serves as the criterion telling whether the value is within the regional background. Minimal background concentrations of petroleum hydrocarbons – 45 to 180 mg/kg (the upper limit of 100‒475 mg/kg) – are typically found in the sediments of rivers and storage reservoirs. In lake sediments, where the proportion of organic matter and clay particles is higher due to hydrological and production characteristics, the background content of petroleum hydrocarbons is estimated to be much higher – 90‒320 mg/kg, and the upper limits of the background content are 195‒510 mg/kg.

Distribution and source estimation of polycyclic aromatic hydrocarbons in coastal sediments from Seto Inland Sea, Japan

Environmental contextPolycyclic aromatic hydrocarbons are carcinogenic environmental contaminants that tend to migrate into the sediments in oceans and seas. Their vertical distribution in sediments from the Seto Inland Sea matched their emission over time, which in turn reflected changes in energy sources and industrial activities in Japan. This study shows that human activities on land directly and significantly influence the concentration of polycyclic aromatic hydrocarbons in sediments. AbstractSeventeen polycyclic aromatic hydrocarbons (PAHs) were identified in sediment cores collected at several locations in the Seto Inland Sea in 2015 and 2016 to understand their spatial distribution and potential emission sources. PAHs were analysed using gas chromatography–mass spectrometry. The age of the sediment cores was analysed using radioisotopic dating techniques to reconstruct historical PAH emissions. The total concentrations of 17 PAHs in the sediment cores of Osaka Bay in 2015 were in the range of 108–2810ng g−1 dry weight (dw) with a mean concentration of 1050ng g−1 dw. The total concentrations of 17 PAHs in sediment cores from the Seto Inland Sea in 2016 were in the range of 52.6–941ng g−1 dw with a mean concentration of 313ng g−1 dw. The spatial distribution of PAHs showed the highest concentration in Osaka Bay and the lowest in Kii Channel in 2016. The horizontal PAH distribution showed a decreasing trend in concentrations from the estuary offshore to Osaka Bay and Aki-Nada. The vertical PAH distribution revealed that levels were higher before the 1980s–1990s, when oil consumption and industrial activities in the Osaka region reached a maximum in the 20th century. The diagnostic ratios of PAHs and a principal component analysis revealed three main emission sources of PAHs, industry, biomass burning and traffic activities.

Spatial and temporal changes in the population of macro-benthic invertebrates exposed to oil spillage in Suez Bay, Red Sea, Egypt

The current study aims to assess the environmental response of macro-benthic invertebrates in the exposed coastal area of Suez Bay to a big fuel oil spill leakage from Ataqa Power Station. This oil spill occurred in the area opposite to the Power Station where the ninth (IX) sampling station was located. Thirteen stations were selected in the studied area and sampling was carried out during spring, 2018 (before the oil spill) and autumn, 2018 (after the oil spill) incident. The results indicated that the density of macro-benthic invertebrates were higher in spring than that in autumn (61,636 and 26,839 ind./m2, respectively). The Northern stations recorded higher densities than the southern ones (16,438 ind. ∕m2 with 34 species and 10,401 ind. ∕m2 with 19 species, respectively). Except for ammonia, the recorded values of dissolved nutrients (nitrite, nitrate, phosphate, and silicate) were higher in autumn than in spring. In addition, it was found that the average concentration of total petroleum hydrocarbons in sediments was 431.49 μg/g in autumn. While in spring, it was estimated to be in average of 194.96 μg/g.

Effects of offshore oil exploration and development in the Alaskan Beaufort Sea: Long-term patterns of hydrocarbons in sediments.

The United States Bureau of Ocean Energy Management (BOEM) has sponsored 4 major monitoring projects in the oil and gas development area of the Alaskan Beaufort Sea since the 1980s, the last being the Arctic Nearshore Impact Monitoring in the Development Area III (ANIMIDA III) Project (2014-2017). These studies were conducted to better understand the physical, chemical, and biological environments and how oil and gas activities may impact them. This paper focuses on monitoring sediment hydrocarbon chemistry. The projects included measuring polycyclic aromatic hydrocarbons (PAHs), n-alkanes and isoprenoids (SHCs), and sterane/triterpene (S/T) geochemical biomarkers and determining their distribution, possible sources, and environmental significance in the sediments of the Beaufort Sea and rivers emptying into it. Concentrations of hydrocarbons in sediments were variable on both spatial and temporal scales; surface sediment concentrations of total PAHs (TPAHs), the class of hydrocarbons of greatest environmental interest, averaged between 300 and 700 μg/kg in different years of monitoring between 1985 and 2015. The concentrations were similar to those measured in other marine regions of Alaska where oil activities have not occurred. Sediment TPAH concentrations were below sediment quality guidelines values, indicating a low risk of harm to benthic marine communities. The hydrocarbons in the Beaufort Sea sediments are primarily from non-oil petrogenic and biogenic sources, with small amounts of pyrogenic hydrocarbons. Most of the hydrocarbons are carried to the Beaufort Sea in coastal erosion and river inputs of hydrocarbon-rich materials, such as peat and shale. The majority of the Beaufort Sea Development Area, including near production facilities, contains uncontaminated sediments with only a few small areas near (<100 m) some exploratory wells where petroleum hydrocarbon concentrations are above regional background. Integr Environ Assess Manag 2019;15:224-236. © 2019 SETAC.

On the effects of the dispersant Corexit 9500© during the degradation process of n-alkanes and PAHs in marine sediments

In many coastal countries, oil spill contingency plans include several alternatives for removal of the spilled oil from the ocean. Frequently, these plans include dispersants. Because this process applies chemical substances that may add toxicity to oil that already contains toxic compounds, it is, at times, a controversial method to fight oil pollution. Additionally, local conditions may result in particular complications. We investigated the possible effects of the dispersant Corexit 9500© under conditions similar to those of subtropical oceans. We used fuel oil #6+ diesel as the test mixture. Under certain conditions, at least part of the dispersed oil may reach the sediment, particularly if the dispersant is applied in coastal waters. Nine experimental units were used in this experiment. Similar conditions of water temperature, salinity, air fluxes into the experimental units, and hydrocarbon concentrations in sediments were used. Two treatments and one control, each one with three replicates, were carried out. We concentrated our investigation on sediment, although measurements of water were also taken. Our results suggest that once the oil has penetrated the sediment, no significant differences exist between oil that contains dispersant and oil without dispersant. Noticeable degradation of aliphatic hydrocarbons occurred mainly in the low molecular weight aliphatic hydrocarbons and not in the others. Apparently, degradation of aromatics was easier than that of alkanes. However, some differences were noticed for the degradation of PAHs in the sediment, suggesting a faster degradation under particular conditions in aerobic environments such as under this experiment.

Composition and sources of aliphatic lipids and sterols in sediments of a tropical island, southern South China Sea: preliminary assessment

Near-shore surface sediment was collected from five stations off Redang Island located on the eastern coast of Peninsular Malaysia. Freeze-dried sediments were Soxhlet extracted and then fractionated using column chromatography into aliphatic and polar fractions. Determination of these fractions was carried out using gas chromatography mass spectrometry. The concentration of total resolved aliphatic hydrocarbons in sediments ranged from 157 to 308 ng/g. The distribution of aliphatic fraction showed the presence of n-alkanes ranging from nC15 to nC33 with a minor odd-to-even predominance exhibiting carbon maximum, depending on station, at nC17, nC26, nC29 or nC31. Calculation of Carbon Preference Index (CPI) for CPI(15-33) gave values ranging from 1.09 to 1.46. n-Alkanol in all sediment exhibits even-to-odd carbon predominance ranging from nC16 to nC28 and maximising at nC22. n-Fatty acids distribution ranged from nC14 to nC24 with a dominant maximum at nC16 and exhibiting high values of short chain fatty acids (≤nC20) to long chain fatty acids (>nC20) ratios. Unsaturated fatty acids, particularly nC16:1 and nC18:1 is also ubiquitous in all samples. Cholesterol is the most abundant compound amongst the sterol group ranging from 42.8 to 62.6% of the total sterols. β-Sitosterol, brassicasterol and stigmasterol, are also present but of relatively lower amount. These observations suggest that the aliphatic lipids and sterols in the study area originate, mainly, from biogenic sources of marine microbial with minor contribution from epiticular waxes of terrestrial plants.

The effects of urbanization on Lepomis macrochirus using the comet assay

Urbanization has been linked to increased concentrations of polycyclic aromatic hydrocarbons in natural waterways. This study was designed to examine the impact of urbanization and a wastewater treatment plant by investigating the impact on field-collected bluegill (Lepomis macrochirus). Results show a significant increase in DNA strand breaks in blood cells (comet assay) linked to urbanization and a reduction in DNA strand breaks downstream of the WWTP, likely the result of dilution. A laboratory study exposing L. macrochirus to the known mutagen, methyl methanesulfonate, was performed to validate the comet assay endpoints in this species. Results of the laboratory study showed that the comet assay endpoints of tail length and tail extent moment responded in a dose- and time-dependent manner. Habitat quality assessments, along with chemical concentrations of polycyclic hydrocarbons in sediments showed that habitat quality between all sites were similar and that hydrocarbons likely contributed to the DNA strand breaks observed.

Estimation of bioavailability of polycyclic aromatic hydrocarbons in river sediments

This study aimed to evaluate the total concentration of polycyclic aromatic hydrocarbons in sediments of Iguassu River in Southern Brazil. Alongside the concentration, the amount of such compounds bioavailable was also evaluated. This is accomplished by comparing its total amount present in sediments and the amount extracted by n-butanol. The results showed that the total concentration of polycyclic aromatic hydrocarbons presented in sediment ranged from 4.49 to 58.75 μg/g. The total amount of polycyclic aromatic hydrocarbons extracted by n-butanol ranged from 1.22 to 17.07 μg/g. The use of n-butanol represents the mimetic conditions that hydrocarbons, derived from oil, could be taken up by organisms. Most of the hydrocarbons extracted by n-butanol were those with lower octanol–water partition constant, usually those with three and four rings. Compounds with more than four rings were extracted in lower or insignificant amounts. Even the hydrocarbons with lower molecular weight available may be degraded or eliminated by organisms, when accumulated. Estimating bioavailability of hydrocarbons represents what specific hydrocarbons could be available to be taken up by organisms.

Seasonal Monitoring of Hydrocarbon Degraders in Alabama Marine Ecosystems Following the Deepwater Horizon Oil Spill

Following the Deepwater Horizon explosion and crude oil contamination of a marsh ecosystem in AL in June 2010, hydrocarbon-degrader microbial abundances of aerobic alkane, total hydrocarbon, and polycyclic aromatic hydrocarbon (PAH) degraders were enumerated seasonally. Surface sediment samples were collected in October and December of 2010 and in April and July of 2011 along 40–70-m transects from the high tide to the intertidal zone including Spartina alterniflora-vegetated marsh, seagrass (Ruppia maritima)-dominated sediments, and nonvegetated sediments. Alkane and total hydrocarbon degraders in the sediment were detected, while PAH degraders were below detection limit at all locations examined during the sampling periods. The highest counts for microbial alkane degraders were observed at the high tide line in April and averaged to 8.65 × 105 of cells/g dry weight (dw) sediment. The abundance of alkane degraders during other months ranged from 9.49 × 103 to 3.87 × 104, while for total hydrocarbon degraders, it ranged between 5.62 × 103 and 1.14 × 105 of cells/g dw sediment. Pore water nutrient concentrations (NH 4 + , NO 3 − , NO 2 − , and PO 4 3− ) showed seasonal changes with minimum values observed in December and April and maximum values in October and July. Concentrations of total petroleum hydrocarbons in sediments averaged 100.4 ± 52.4 and 141.9 ± 57.5 mg/kg in January and July, 2011, respectively. The presence of aerobic microbial communities during all seasons in these nearshore ecosystems suggests that an active and resident microbial community is capable of mineralizing a fraction of petroleum hydrocarbons.

Petroleum hydrocarbon concentrations in eight mollusc species along Tamilnadu coast, Bay of Bengal, India

Eight mollusc species and sediment samples collected from three different stations along Tamilnadu coast, Bay of Bengal, India were analysed for the levels of petroleum hydrocarbons to elucidate the status of the petroleum residues in mollusc meant for human consumption. The concentrations of petroleum hydrocarbons in sediments along Tamilnadu coast varied from 5.04–25.5 μg/g dw (dry weight). High concentration of petroleum hydrocarbons in the sediment of Uppanar estuary (25.5 ± 1.45 μg/g dw) was perhaps land and marine based anthropogenic sources of this region. The petroleum hydrocarbon residues in eight mollusc species collected from Uppanar, Vellar and Coleroon estuaries varied between 2.44–6.04 μg/g ww (wet weight). Although the concentration of petroleum hydrocarbons in sediment of the Uppanar region was markedly higher than the background, the petroleum hydrocarbon residues in mollusc collected from Uppanar estuary did not suggest bioaccumulation. The results signified that industrial growth has affected the aquatic environments and regular monitoring will help to adopt stringent pollution control measures for better management of the aquatic region.

Heat-shock protein (Hsp70) and cytochrome P-450 (CYP1A) in the white mullet Mugil curema (Pisces:Mugilidae) as biomarkers to assess environmental quality in coastal lagoons

Biomarkers have been useful tools to monitor some effects of pollution in coastal environments. Hepatic expression of heat-shock protein 70 (Hsp70) and cytochrome P450 1A (CYP1A) were analyzed in white mullet (Mugil curema) by RT-PCR from July, 2005 until July, 2006 in three coastal lagoons located in the southern Gulf of California, Mexico. These three coastal systems receive contaminants derived from local anthropogenic activities. Heat-shock proteins function to maintain protein integrity in the presence of stressors (such as heat or chemicals) and can be used as biomarkers of homeostatic alterations in polluted environments, whereas cytochrome P450 family members participate in steroid hormone synthesis and metabolism, and in xenobiotic transformation as a detoxification mechanism. The expression levels of both genes showed consistency in time and space, and presented a high overall correlation (r = 0.731, P < 0.001). Regardless of a high individual variability, both genes presented higher expression levels in the Urias Estuary (P < 0.001 and P < 0.05 for CYP1A and Hsp70, respectively), which was considered the most polluted among the three systems, especially during the rainy season (summer to fall). Gene expression levels were significantly associated with non-halogenated hydrocarbon concentrations in sediments during the sampling period (r = 0.686, P = 0.019 for CYP1A and r = 0.91, P < 0.001 for Hsp70), suggesting that both genes respond to chemicals in the environment. The results indicate that Mugil curema is a good candidate species to implement biomonitoring programs in tropical coastal environments.

Fluxes and fate of petroleum hydrocarbons in the Timor Sea ecosystem with special reference to active natural hydrocarbon seepage

A sediment and sediment trap study of natural oil seeps in the Timor Sea off the north coast of Australia has been conducted. Sediment traps were set at 40 m below sea level on top of a benthic carbonate dome, formed near the Cornea oil and gas field, which was visibly leaking oil and gas around its edges in ∼ 90 m of water. Other traps were set at the continental shelf edge at 100 m and 400 m below sea level on the 500 m bathymetric contour to gauge the long range dispersion of the Cornea seep. Sediment cores from the trap sites and other relevant sites were also collected. Sea surface microlayer samples of the oil slicks emerging with gas bubbles were also sampled. These were used to characterize the oil as it moved from surface slicks, through settling particles, to surface sediment. Downward fluxes of total hydrocarbons (THC) ranged from ∼ 500 µg m − 2 d − 1 at the shallow Cornea seep site to ∼ 100 µg m − 2 d − 1 in 100 m depth traps at the offshore stations. Fluxes of oil polynuclear aromatic hydrocarbons (PAH) ranged from ∼ 6000 ng m − 2 d − 1 at Cornea to ∼ 1000 ng m − 2 d − 1 at off shore stations. Principal Hierarchical Cluster Analysis and Principal Component Analysis (HCA–PCA) of the petroleum biomarkers confirmed that the surface slick samples and sediment traps from Cornea and some of the offshore traps had similar hydrocarbon compositions. However, some of the offshore traps also contained hydrocarbons from an apparently different source. This second source appeared to be “background oil”, probably due to a mixture of natural seeps, oil industry activities, or release from shipping traffic, and was similar in composition to that seen in previous sediment trap studies on the Northwest shelf. The Cornea seep area was deemed a significant point source of oil and gas to the coastal environment that was dispersed by tidal movements across the continental shelf and contributed to settling particles up to 300 km away on the continental slope of the Timor Sea. An extension of a diagenesis model showed that 44 to 77% of the (THC) and 27 to 83% of the (PAH) were degraded in the water column. Of the remaining oil reaching the sediment surface 99 to ∼ 100% of THC and 98 to ∼ 100% of PAH were degraded in the near surface sediments. Microbial biomarkers indicated the presence of sulphate reducing bacteria in both sediment traps and sediments and only trace amounts of the markers associated with Archaea which together accomplish the anoxic oxidation of methane (AOM). Rather than this well known deep sea microbial consortia, aerobic hydrocarbon oxidizing bacteria constituted a small proportion of the bacterial community in the surface sediment layer associated with the largest seep plume observed at the Cornea seep area. These hydrocarbon degraders were not visible in the offshore sediments against the background of other microbes. The rapid water column and surface sediment degradation rates indicated that the Timor Sea is well adapted to degrade natural oil seeps. This rapid degradation rate makes detection difficult for specific oil biomarkers due to low hydrocarbon concentrations in sediments. Such studies are more successfully accomplished with sediment trap deployments.

Description and evaluation of a sampling system for monitoring hydrocarbons in sediments

A composite random sampling design was used to estimate the concentrations of hydrocarbons in sediments from two near-shore areas of Scotland (Firth of Clyde and Firth of Forth). The aim of this work was to estimate a mean value for each parameter in these areas, and to determine whether this can be done with more thorough coverage (better representation), better precision and less variance at lower analytical cost through a composite random sampling scheme rather than a simple random sampling scheme, and thereby contribute to the re-design of the UK National Marine Monitoring Programme (NMMP), re-named the UK Clean Seas Environmental Monitoring Programme (CSEMP) in 2006. Samples were collected using a simple random sampling design during 2005. All sediment samples were analysed for their particle size distribution and total organic carbon (TOC). All sediments were analysed for polycyclic aromatic hydrocarbons (PAHs) and n-alkanes. The concentrations of PAHs and n-alkanes in the study areas are described, and sources of PAHs were investigated through the PAH distributions and n-alkane profiles. Individual sediment samples from each area were combined to give a series of composite sub-samples, each comprised of 5 individual sediment samples. These composite samples were re-analysed for the same parameters as the individual samples. Mean total PAH (2- to 6-ring parent and branched) concentrations, based on the individual original sediment samples collected through simple random sampling, were 1858 microg kg(-1) dry weight (SE = 196 microg kg(-1) dry weight, n = 25) and 532.4 microg kg(-1) dry weight (SE = 59 microg kg(-1) dry weight, n = 25) in the Clyde and Forth, respectively. Mean total PAH concentrations of the composite samples were 1745 microg kg(-1) dry weight (SE = 121.0 microg kg(-1) dry weight, n = 5) in the Clyde and 511.6 microg kg(-1) dry weight (SE = 37.4 microg kg(-1) dry weight, n = 5) in the Forth. No significant differences were found between the mean PAH concentrations from the two sampling designs. This study demonstrated that the composite random sampling design gave a mean value with less variance than the simple random sampling design, at significantly reduced analytical effort (and cost).

Measurement of total polycyclic aromatic hydrocarbon concentrations in sediments and toxic units used for estimating risk to benthic invertebrates at manufactured gas plant sites

The U.S. Environmental Protection Agency's (U.S. EPA) narcosis model requires the measurement of 18 parent and 16 groups of alkyl polycyclic aromatic hydrocarbons (PAHs) (so-called 34 PAHs) in sediments to calculate the number of PAH toxic units (TU) available to benthic organisms. If data for the 34 PAHs are not available, the U.S. EPA proposes estimating the risk by multiplying the TU for 13 parent PAHs by 11.5 (95% confidence interval) based on data from 488 sediments. This estimate is overly conservative for PAHs from pyrogenic manufactured gas plant (MGP) processes based on the analysis of 45 sediments from six sites. Parent PAHs contributed approximately 40% of the total concentrations and TU for MGP sediments. In contrast, parent PAHs from diesel fuel and petroleum crude oil contributed only 2 and 1%, respectively, of the PAH concentrations and TU, compared to approximately 98 to 99% contributed by the alkyl PAHs. Statistical comparison of the TU based on the measured 34 alkyl and parent PAHs and those based on only 13 parent PAHs demonstrated that a factor of 4.2 (rather than 11.5) is sufficient to estimate total TU within a 95% confidence level for MGP sites. Similarly, measurement of parent PAHs is sufficient to accurately estimate the total 34 alkyl and parent PAH concentrations for MGP-impacted sediments.

Oil spill in the Río de la Plata estuary, Argentina: 2-hydrocarbon disappearance rates in sediments and soils

The 6-month assessment of the oil spill impact in the Río de la Plata described in the preceding paper [Colombo, J.C., Barreda, A., Bilos, C., Cappelletti, N., Demichelis, S., Lombardi, P., Migoya, M.C., Skorupka, C., Suárez, G., 2004. Oil spill in the Río de la Plata estuary, Argentina: 1 – biogeochemical assessment of waters, sediments, soils and biota. Environmental Pollution] was followed by a 13- and 42-month campaigns to evaluate the progress of hydrocarbon decay. Average sediment hydrocarbon concentrations in each sampling include high variability (85–260%) due to contrasting site conditions, but reflect a significant overall decrease after 3 years of the spill: 17 ± 27, 18 ± 39 to 0.54 ± 1.4 μg g −1 for aliphatics; 0.44 ± 0.49, 0.99 ± 1.6 to 0.04 ± 0.03 μg g −1 for aromatics at 6, 13 and 42 months, respectively. Average soil hydrocarbon levels are 100–1000 times higher and less variable (61–169%) than sediment values, but display a clear attenuation: 3678 ± 2369, 1880 ± 1141 to 6.0 ± 10 μg g −1 for aliphatics and 38 ± 26, 49 ± 32 to 0.06 ± 0.04 μg g −1 for aromatics. Hydrocarbon concentrations modeled to first-order rate equations yield average rate constants of total loss (biotic + abiotic) twice as higher in soils ( k = 0.18–0.19 month −1) relative to sediments (0.08–0.10 month −1). Individual aliphatic rate constants decrease with increasing molecular weight from 0.21 ± 0.07 month −1 for isoprenoids and < n-C22 to 0.10 ± 0.08 month −1 for > n-C27, similar to hopanes (0.10 ± 0.05 month −1). Aromatics disappearance rates were more homogeneous with higher values for methylated relative to unsubstituted species (0.17 ± 0.05 vs. 0.12 ± 0.05 months −1). Continued hydrocarbon inputs, either from biogenic (algal n-C15,17; vascular plant n-C27,29) or combustion related sources (fluoranthene and pyrene), appear to contribute to reduced disappearance rate. According to the different loss rates, hydrocarbons showed clear compositional changes from 6–13 to 42 months. Aliphatics disappearance rates and compositional changes support an essentially microbiologically-mediated recovery of coastal sediments to pre-spill conditions in a 3–4 year period. The lower rates and more subtle compositional changes deduced for aromatic components, suggest a stronger incidence of physical removal processes.

Chlorophyll-deficient propagules of Avicennia marina and apparent longer term deterioration of mangrove fitness in oil-polluted sediments

A correlation between petroleum hydrocarbon concentrations in sediments and chlorophyll-deficient mutations in mangroves may occur also in Australian mangroves. Earlier reports of such mutations in the Caribbean area were evident in viviparous propagules of the common mangrove genera, Rhizophora, borne on otherwise normal trees. These mutant propagules were termed ‘albinos’ since they lacked chlorophyll and normal green coloration, leaving them white, yellow or red. The mutation was considered lethal since newly established albino seedlings appeared unable to survive more than a few months. Our preliminary investigation of mangroves in SE Queensland found a similar mutation in another common mangrove genus, Avicennia, and this was apparently also correlated with oil concentrations in sediments. Although, more evidence is required, an apparently similar relationship shows that whatever caused the mutations may act commonly across a diverse range of plant types in quite separate locations. How widespread might this mutation be in mangroves? How many genera and species are affected? Are all occurrences correlated with oil in sediments? Does oil cause the mutation? We discuss these important questions and the potentially serious implications to coastal management where high mutant densities may be indicative of longer term genetic deterioration of mangrove habitat in oil-polluted wetland environments.

Long-term investigation of benthic fauna and the influence of treated ballast water disposal in Port Valdez, Alaska

Benthic faunal structure and hydrocarbon concentrations in sediments were examined annually for 10 years (1989–1998) in Port Valdez, Alaska, where a near-bottom permitted discharge of treated tanker ballast waters containing residual petroleum has occurred since 1977. Measured concentrations of hydrocarbons in sediments near the discharge showed detectable increases in concentration, but on only one occasion were these increases either to levels exceeding ecotoxicological thresholds (Effects-Range Low, ER-L) or associated with alterations in the benthic community. Changes in faunal structure indicating disturbance were observed at one station near the discharge from 1995 to 1997 and were apparent as increased numbers of opportunistic taxa and anomalous trends in abundance and diversity. Minimum-effect (ME) hypotheses provided evidence of negligible to small effects on benthic infauna from disposal of treated ballast water. ME hypotheses have the potential to assist both researchers and managers by providing a tool to relate scientific results to ecological importance and decision criteria.

Characterization and degradation of petroleum hydrocarbons following an oil spill into a coastal environment of South Texas, U.S.A.

Petroleum hydrocarbons were characterized at eleven sites withinthe sediments of a coastal stream in south Texas, U.S.A. following a medium sized crude oil spill. Bank and open-water(deep) sediments were collected at each site. Hydrocarbonstargeted for analysis included 22 aliphatic hydrocarbons (C-11to C-34) and 16 polynuclear aromatic hydrocarbons. Sedimentconcentrations were measured at intervals of 1, 2, 3, 4, 6, and12 months post-spill. Higher hydrocarbon concentrations were observed for a longerduration within the deep sediments than bank sediments. Initialhydrocarbon constituents in impacted sediments matched the crudeoil fingerprint accurately with the exception of the lighter-endhydrocarbons. The lighter-end aliphatic hydrocarbons areaffected immediately by evaporation and dissolution processesduring the spill event and were found below the detection levelsat most of the sites. Total hydrocarbon concentrations insediments within each hydrocarbon group returned to backgroundlevels by the end of the study period. Observed decreases inhigh molecular weight polycyclic aromatic hydrocarbons (PAH)concentrations exceeded known environmental degradation rateswhich suggests the influence of a sediment transport process. Overall, the fate of petroleum hydrocarbons within this type ofenvironment were likely related to both degradation and sedimenttransport processes. By the end of the study period, most individual PAH constituent concentrations were below thresholdconcentrations thought to produce toxic effects in marine andestuarine organisms. PAH constituents concentrations remainingabove threshold concentrations included benz(a)anthracene,chrysene, and benzo(a)pyrene.

The composition and the source of hydrocarbons in sediments taken from the tectonically active Andaman Backarc Basin, Indian Ocean

Abstract Concentrations of total hydrocarbons in sediments of the tectonically active part of the Andaman Basin ranged from 130–720 (with an average of 349) mg/kg in the most active Spreading zone (the Rift Valley) to 43–180 (with an average of 113) mg/kg in the less active Fault zone of the Deep Basin. Average concentrations of total aromatic hydrocarbons ranged from 215 mg/kg in the Spreading zone to 49 mg/kg in the Deep Basin. Compound distributions were dominated by short-chain n -alkanes n -C 13 – n -C 24 (on the average, 77% in the Spreading zone and 64% in the Deep Basin, correspondingly). Distribution of n -alkanes in this region is characterized by a carbon predominance index (CPI 13–35 ) being mainly either below or about 1,0. Substituted homologues of biphenyl, fluorene, naphthalene, phenanthrene, benzofluorenes, chrysene (6-methylchrysene), pyrene and perylene (3-methylperylene) as well as unsubstituted individual polycyclic aromatic hydrocarbon (PAH): pyrene, benzo( a )pyrene, perylene, benzo( g , h , i )perylene, were identified in all samples. Concentrations of substituted homologues of PAH ranged, on the average, from 27 μg/kg in the Spreading zone to 16 μg/kg in the Deep Basin. Concentrations of unsubstituted individual PAH ranged, on the average, from 25 μg/kg in Spreading zone to17 μg/kg in the Deep Basin. A composition of both aliphatic hydrocarbons and PAH in the sediments of the region studied is identical to the composition of non-biological compounds: petroleum products or hydrothermal organic matter. Anthropogenic sources in region studied are of minor importance. From the results obtained, it may be deduced that the hydrocarbons in the sediments of the tectonically active part of the Andaman Basin are mainly due to an alteration of sediment organic matter by emanation processes (hydrothermal and thermal fluxes, Earth's outgassing, petroleum show, etc.).

An Assessment of Potential Oil Spill Damage to Salt Marsh Habitats and Fishery Resources in Galveston Bay, Texas

We sampled nekton, benthic infauna, and sediments in salt marshes of upper Galveston Bay, Texas to examine relationships between habitat use and sediment hydrocarbon concentration. Most marsh sediment samples were contaminated with relatively low concentrations of weathered petroleum hydrocarbons. We found few statistically significant negative relationships between animal density and hydrocarbon concentration (6 of 63 taxa examined using simple linear regression). Hydrocarbon concentration did not contribute significantly to Stepwise Multiple Regression models we used to explore potential relationships between animal densities and environmental parameters; in most cases where hydrocarbon concentration was an important variable in the models, the relationship was positive (i.e., animal densities increased with hydrocarbon concentration). Low hydrocarbon concentrations in sediments of upper Galveston Bay marshes could have contributed to our results either because levels were too low to be toxic or levels were toxic but too low to be detected by most organisms.