Milford Haven Research Articles

THE SEA EMPRESS INCIDENT: OVERVIEW AND RESPONSE AT SEA

ABSTRACT The oil tanker Sea Empress spilled more than 72,000 tons (23 million U.S. gallons) of crude oil when she grounded at Milford Haven, United Kingdom, on February 15, 1996. The response at sea by the U.K. government through the Coastguard Agency's Marine Pollution Control Unit involved aerial surveillance, the spraying of dispersants from aircraft, and the recovery of several thousand tons of oil from the sea surface. This paper by the overall commander presents an overview of the incident and the response operation at sea.

HYDROCARBONS AND PAH IN FISH AND SHELLFISH FROM SOUTHWEST WALES FOLLOWING THE SEA EMPRESS OIL SPILL IN 1996

ABSTRACT The tanker Sea Empress spilled approximately 72,000 tons of light crude oil from the Forties field (North Sea) and 360 tons of heavy fuel oil at the mouth of Milford Haven in west Wales in February 1996. The scale of the spillage made it necessary to impose closure orders on both commercial and recreational fishing in adjacent coastal waters and rivers. A monitoring program was initiated both to follow the spread of oil and its uptake by fish and shellfish and to provide information with which to assess human health risks. In this paper we report the results of monitoring in both commercial and noncommercial stocks offish and shellfish in the first 6 months following the grounding.

Modulations in Cell-Mediated Immunity of Mytilus Edulis Following the ‘Sea Empress’ Oil Spill

The ‘Sea Empress’ oil tanker grounded outside Milford Haven (Wales, UK) in February 1996, spilling ~70,000 tonnes of crude oil and contaminating over 100 km of coastline, causing mass mortalities and standings of at least 11 mollusc species. Intensive field monitoring commenced after the spill, examining immunity and hydrocarbon levels in the mussel, Mytilus edulis (Mollusca: Bivalvia), a commercially-harvested species which can accumulate contaminants. Comparisons of mussels from oiled and reference sites revealed significant modulations in cell-mediated immunity. Elevations in blood cell (haemocyte) numbers and decreases in superoxide generation and phagocytosis were identified in contaminated animals. The immune response of contaminated mussels gradually improved and generally showed no significant differences compared with clean mussels after 11 weeks. By then, total hydrocarbon content in contaminated mussels had declined by 70–90%, while polycyclic aromatic hydrocarbon content had decreased by over 90%.

RADARSAT SAR for oil spill response

RADARSAT synthetic aperture radar imagery has been successfully classified to delineate oil slicks on water using training areas for various degrees of oil coverage located within each image. Three and four class schemes have been tested with imagery from the Nakhodka and Milford Haven spills. An interactive graphical editor has been developed using the classified images to re-initialize the SPILLSIM oil spill model during a simulation.

Microgeographical variation in shell strength in the flat periwinkles Littorina obtusata and Littorina mariae

The strength of molluscan shells has been shown to vary in adaptive ways in a number of species and one of the main factors thought to be involved is shell-crushing by predators. A recent study found that the sibling species of flat periwinkle Littorina obtusata and Littorina mariae showed significant differences in the rates at which shell strength increased with shell length in specimens which had been collected from the same location, where the species were sympatric. This paper describes differences between the shells of the two species from a number of localities around Milford Haven in Dyfed, Wales, and local geographical variation in the shells.

Variation in populations of Littorina obtusata and L. mariae (Gastropoda) in the Severn Estuary

Abstract Populations of both species of flat periwinkle were examined at five discrete sites along the Severn Estuary, and at a marine site in Dyfed. The vertical distribution of the two species showed a clear partitioning of the shore— Littorina obtusata occupied the high/mid shore and L. mariae the low shore area. L. obtusata also extended further up the Severn Estuary than L. mariae. Maximum densities of both species were found in Milford Haven. Biometric investigations revealed intra and inter-specific differences in colour morphs, shell damage and size between populations. The possihle influence of differential selection pressures at the various sites is discussed.

Variation in populations of Littorina obtusata and L. mariae (Gastropoda) in the Severn Estuary

Populations of both species of flat periwinkle were examined at five discrete sites along the Severn Estuary, and at a marine site in Dyfed. The vertical distribution of the two species showed a clear partitioning of the shore— Littorina obtusata occupied the high/mid shore and L. mariae the low shore area. L. obtusata also extended further up the Severn Estuary than L. mariae. Maximum densities of both species were found in Milford Haven. Biometric investigations revealed intra and inter-specific differences in colour morphs, shell damage and size between populations. The possihle influence of differential selection pressures at the various sites is discussed.

A mathematical model for the hydrodynamics and pollutants transport in long and narrow tidal rivers

This paper deals with the application of the Taylor-Galerkin finite element method to the simulation of the tidal dynamics and transport of chemically reactive pollutants in a branching river—estuary system. The adopted mathematical technique is fully described and the derivation of the working equations of the scheme is outlined. To validate the model two case studies, namely, tidal dynamics and salt intrusion in Upper Milford Haven (Wales, UK) and heavy metal dispersion in the Fal estuary (Cornwall, UK) are reported. Results of the model simulation in both cases are in good agreement with the field observations.

LONG-TERM FATE AND EFFECTS OF UNTREATED THICK OIL DEPOSITS ON SALT MARSHES

ABSTRACT The paper compares two case histories in which thick oil layers were deposited on salt marshes. The first concerns a spill in Milford Haven, Wales, in February 1969, which resulted in deposits of heavy fuel oil on parts of the Martinshaven marsh. The second concerns the Metula spill of light Arabian crude in the Strait of Magellan, Chile, in August 1974. Salt marshes near Puerto Espora, Tierra del Fuego, were affected by thick mousse. Following both spills, vegetation was smothered and killed. For a variety of reasons, including remoteness, there was no cleanup treatment in either case. At Martinshaven, vegetation recovery started within the first year after the spill, and was complete within 15 years. The oil layer is still clearly visible in core samples, but is not visible at the marsh surface because of sediment deposition. Samples analyzed in 1990, 22 years after the spill, were still recognizable as heavy fuel oil, albeit highly degraded. The Puerto Espora marshes were revisited in 1990 and 1991, 16 and 17 years after the spill. Mousse deposits were still visible at the surface. Samples analyzed in 1990 showed that oil beneath the surface skin of thick deposits was still quite fresh. There was no vegetation recovery in such areas. Where deposits were thinner, the mousse was well weathered and vegetation was recovering. Factors influencing recovery include oil type and weathering, oil thickness, sedimentation processes, size of area affected, and plant morphology. It is concluded that in extreme circumstances of extensive, thick oil deposits, natural recovery will take decades, so a cleanup program is likely to be justifiable. Cleanup may not be necessary for small areas of thick deposits on some marshes.

Estuarine Oil Spill Effects in the Context of Dispersant use Changes

ABSTRACT Surveys of rock, cobble, gravel, and salt marsh shores, intertidal macrobenthos, hydrocarbons, and estuarine bird populations were carried out over twelve months following the El Omar spill of 3 December 1988, when 100 metric tons (t) of Iranian light crude oil were spilled in Milford Haven, United Kingdom. Although small, this incident resulted in more widespread shoreline oiling than any previous spill in 30 years of operations at Milford Haven. About 20 t of chemical dispersant were used in the lower estuary. Dispersants were not used where there was a danger of oil and dispersant mixtures impinging on fish farms. Rock/cobble shores have been studied since the arrival of the oil industry in 1960 and spill impacts were, therefore, discernible at some sites against the baseline data. Serious impacts occurred locally due to excessive oiled algae and substrate removal. On gravel and salt marsh study sites, natural removal of oil was an efficient cleanup option. Some evidence was detected, however, that oil deposited on seed heads of Spartina was later transferred to the sediment surface as part of the litter fall. The marsh vegetation recovered by the end of the 1989 growing season, confirming the resilience of this community to single oil spills, provided intrusive cleanup is not attempted. The increase in aromatic hydrocarbon concentrations found in the surface sediments of the salt marsh was found also in mudflats adjacent to heavily-oiled areas, although no biological effects on the infauna of the inner estuary were detected (compared to a macrobenthic and hydrocarbon survey of 1984). No significant impacts were recorded on the population of 20,000 waders, wildfowl, and gulls present at the time of the spill. This is believed to be partly fortuitous due to the mild 1988/89 winter. The arrival in Milford Haven of intensive fish farming means that the previously routine use of chemical dispersants in the oil port will now be increasingly challenged. From the El Omar, it may be predicted that, in future spills, more oil will become stranded in marshes and rock and cobble shorelines. Not only are guidelines and scientific advice during shoreline cleanup essential, but also it is recommended that scientific monitoring, which lapsed in the early 1980s, be reinstated. These data would help make the important tradeoff between commercial and conservation interests in future spills.

Pollutant transport and fate in ecosystems : Coughtrey, P.J., M.H. Martin and M.H. Unsworth (eds.), 1987. [Selected papers from a meeting of the Industrial Ecology group, British Ecological Society, University of Bristol, 1–4 April 1985.] Spec. Publ. Br. ecol. Soc., 6:414pp; 26 papers

Partial Contents: The periodic table of the elements: geochemical and biochemical mechanisms Flushing and dispersal mechanisms in estuaries Transfer mechanisms for dissolved pollutants in estuaries Some factors affecting the fate of estuarine hydrocarbons and trace metals in Milford Haven, 1978-82 Facts and fallacies in wet deposition modelling The capture of wind-driven cloud by vegetation Transport of acidity through ecosystems The modification of rainfall chemistry by a forest canopy Transformations in rainwater chemistry on passing through forested ecosystems The microbial sulphur cycle in atmospheric polluted soils.

The effects of sediment transport on contaminant dispersal: an example from Milford Haven [U.K.] : McLaren, P. and D.I. Little, 1987. Mar. Pollut. Bull., 18(11):586–594. Dept. of Earth Sci., Univ. of Cambridge, Downing St., Cambridge CB2 3EQ, UK

The effects of sediment transport on contaminant dispersal: an example from Milford Haven [U.K.] : McLaren, P. and D.I. Little, 1987. Mar. Pollut. Bull., 18(11):586–594. Dept. of Earth Sci., Univ. of Cambridge, Downing St., Cambridge CB2 3EQ, UK

The effects of sediment transport on contaminant dispersal: An example from Milford Haven

Milford Haven is an estuary that has been subjected to industrial pollution from tanker operations and refinery and power station effluents since about 1962. Consequently build-up of various anthropogenic heavy metals and hydrocarbons has been observed in the bottom sediments. This paper describes 1. a new technique whereby the patterns of net sediment transport are determined from the relative changes of grain-size distributions in 125 grab samples, and 2. how net sediment transport correlates with the quantity of contaminants contained in the bottom sediments. The analysis demonstrates that sediment movement in the flood direction dominates the central channel and the northern half of the estuary. Transport in the ebb direction is confined to the southern coastal zone. A comparison of the transport paths with contaminant concentrations shows clearly that the flood-dominant movement leads to concentration of heavy metals and hydrocarbons. As a result, an area of fine-grained deposition near the head of the estuary receives exceptionally high concentrations of contaminants. The ebbdominant transport, on the other hand, causes dilution in the amount of pollutants contained in the sediments. The derived transport paths agree well with known current patterns, and this technique is shown to be a rapid and inexpensive method for 1. environmental impact assessment, 2. establishing effective monitoring programmes, 3. predicting areas vulnerable to contamination, and 4. rational contingency planning.

87:6588 A study of the sediments and communities in Milford Haven, Wales: Rostron, D.M., D.I. Little and S.E. Howells, 1986/87. Oil chem. Pollut., 3(2):131–166. 14 Merlins Cross, Lower Lamphey Rd., Pembroke, Dyfed, Wales

87:6588 A study of the sediments and communities in Milford Haven, Wales: Rostron, D.M., D.I. Little and S.E. Howells, 1986/87. Oil chem. Pollut., 3(2):131–166. 14 Merlins Cross, Lower Lamphey Rd., Pembroke, Dyfed, Wales

Mathematical model of Upper Milford Haven—A branching estuary

A mathematical model for hydrodynamics and salt intrusion in a one-dimensional branching estuary has been developed. The model satisfactorily predicts water levels and discharges throughout Upper Milford Haven estuary for spring and neap tides. There is also a measure of agreement between computed and observed salinities.

A study of the sediments and communities in Milford Haven, Wales

Milford Haven is a well-established oil port which has been in operation since the early 1960s, at which time biological monitoring activities were also in progress. The majority of these activities were rocky shore studies. The first comprehensive study of sediments using remote sampling techniques was carried out in 1975 and revealed that a variety of community types were present within Milford Haven. Two further sediment surveys were completed during the months of April 1982 andApril 1984. In 1982, 135 stations were sampled. This was reduced to 55 in 1984, of which 46 were relocated from the 1982 work. The samples, obtained by means of a Day grab, were used for biological, sediment particle size, trace metal and hydrocarbon analyses. The objectives of the 1982 benthic survey were to make a thorough investigation of the distribution of species and communities in relation to environmental factors, and also to note possible effects of industrial activity within the survey area. Populations of several species appeared to have changed since the area was last surveyed during 1975. Several species characteristic of stressed environments, notably Chaetozone ?setosa, had increased in abundance. In Pembroke River there were interesting variations in the distribution and types of species present. Areas of interest were resurveyed during 1984 in order to monitor the status of the opportunist species in Milford Haven, and to provide more detailed data on the distribution of intertidal species in Pembroke River. The 1984 data showed that whilst the opportunistic species Chaetozone ?setosa had shown fluctuations in density from station to station, it had changed little in distribution or abundance between the two surveys. Other species typical of muddy areas had increased in density. Although not grossly polluted, communities showed signs of disturbance, probably as a result of dredging activities and various kinds of anthropogenic input. Pembroke River maintained a reasonably high diversity of species in comparison with other estuarine areas in the British Isles. The range in total hydrocarbon concentration was from 1 to 615 μgg −1 whilst the overall trace elements were comparatively low for an estuary with substantial areas of fine sediment. However, all contaminants showed a clear enrichment at certain localities within Milford Haven.

Modelling of tidal motion in shoaling waters: The estuary of Milford Haven

An experimental survey of the estuary of Milford Haven has been carried out in which velocity, temperature and salinity have been measured over the full extent of the estuary during a complete spring and a complete neap- tidal cycle. The measurements were taken from three survey vessels, each of which was used to service six or seven survey points so that the measurements comprised a total of about 40 vertical profiles distributed over a grid of 20 survey points for each tide. Tide level measurements at two points were made simultaneously. The experimental measurements of tidal level have been used to calibrate a two-dimensional mathematical model based upon a new numerical representation of the shallow water equations. The predictions of velocity for the model have been compared with vertically integrated velocities calculated from experiments, and good agreement has been found over the full extent of the estuary. The effect of a strong south-westerly wind in the estuary has been examined in numerical simulation.

Spawning of Herring in Milford Haven

Information regarding spawning grounds of the Atlantic herring Clupea harengus Linnaeus has been based mainly on the collection of spawning fish, newly hatched larvae, or the presence of eggs within the stomachs of predators (Postuma, Saville & Wood, 1977). This type of evidence indicates general areas of spawning, rather than accurately delineating the spawning grounds. Though samples of spawn have been obtained from several localities in the North-East Atlantic (Ewart, 1884; Runnström, 1941; Fridriksson & Timmerman, 1951; Bolster & Bridger, 1957; Parrish et al. 1959; Hemmings, 1965; Bowers, 1969; Anthony, Sauskan & Sigaer, 1970), few quantitative studies of individual grounds have been made. In consequence, little is known of the factors influencing the selection of grounds by Atlantic herring, the shape of these grounds and egg distribution within spawning areas.

Estimation of dispersion in estuaries by a self-consistent method

Longitudinal and transverse dispersion in estuaries may be determined in principle by measuring the change in time of the concentration field of a water soluble dye. In practice, measurements may take the form of several sampling runs crossing the dye patch. The coefficients of dispersion are usually estimated from the second moments of the concentration field; the use of second moments, in particular, introduces errors because measurements at long times or distance are unduly emphasized. A self-consistent method, free of the disadvantages inherent in the use of higher moments, is described in which the distribution of concentration in space is related to the zeroth spatial moment of concentration. In this formulation, based upon sampling runs across the dye patch, the concentration field in the estuary may be directly and simply related to the dispersion coefficients in both the intercept and gradient of a linear graph. The methods are illustrated by the characterization of a series of experiments in the Inner Estuary of Milford Haven.

Rocky shore monitoring in Milford Haven

Oil-related industrial developments in Milford Haven began in 1960. Over the next 13 years four refineries, one terminal and one power station were opened. With the onset of tanker movement came the inevitable oil spills. Ecological studies of the rocky shores began in 1958 and continued until 1982. This paper deals with the most recent studies, carried out in 1982. Results show that biological changes have occurred on some rocky shores, mainly in limpet, barnacle, gastropod and seaweed populations. Changes tend to be shore-specific and are either interpreted as natural or tentatively linked to oil industry activity. Apart from localised changes, Milford Haven continues to support apparently healthy rocky shore communities. There are several factors which have helped to prevent the deterioration of the shores, such as tidal flushing, active port management and strict water authority effluent quality standards. In addition, the rocky shores are comparatively resilient, and Milford Haven has never been subjected to an extremely severe oil spill. Sublittoral benthic studies revealed that the communities in certain areas may have been subjected to mild pollution stress. To date, damage in Milford Haven has been very limited, but strict controls must be maintained in the future to ensure that conditions do not deteriorate further.