5.1 ENVIRONMENTAL VULNERABILITIES

5.1.1 General Aspects

Crude oil and oil products have a major share of the marine mass cargo transported across the world oceans and handled in marine ports. Consequently considerable risks arise for the marine environment as a consequence of oil releases.

Oil present in the marine environment originates mainly from human activities throughout the hydrocarbon offshore production and transport chains. Typical releases occur from production wells, risers and platforms, tanker and ship accidents as well as from faults in cargo handling or of storage and transportation systems (pipelines, flow lines, risers and tanks). Deliberate releases from tank washing and ballasting of empty crude oil tankers comprise a non-negligible diffusive source for oil releases across the oceans despite this is a matter of high concerns especially in marine sensitive or protected areas like all coastal zones and nearshore regions and marginal and enclosed seas (in Europe particularly the North Sea, the Baltic Sea, the Mediterranean and the Black Sea). Large spill events are mainly caused by tanker accidents, to some extent also by blow-outs of subsea oil wells. In times of naval warfare large amounts of oil can be spilled into the seas by offensive actions and sinking of ships as well as deliberate releases (“environmental warfare”) as massively experienced during the first Gulf War in 1991. Nowadays oil releases along with terrorist actions are considered as an additional threat to the marine environment. Regionally but rarely oil is diffusing also into the environment by natural processes by washout of near surface subsea or coastal hydrocarbon reservoirs.

Human errors and deliberate disregards of environmental policies and best practices are a major reason for minor and small spill incidents (some to about 100 tonnes). Larger spills (several hundreds to thousand tonnes) occur mostly as consequences of ship accidents with spilling fuel oil or rupture of cargo tanks. Their reasons lie mostly in a combination of human errors, adverse weather conditions, lacking maintenance and aged vessels. Large spills (in excess of several thousand tonnes) have similar reasons in case of tanker accidents and are mostly associated with a total loss of the transported cargo and the vessel. Apart form war-like actions well blowouts are another reason for large spills which are caused by human errors and/or unexpected reservoir conditions.

The release of oil into the marine environment becomes almost immediately a matter of high public concerns. Whereas most other pollutants dissolved in marine waters or aggregated in sediments are directly detectable by means of measurements, sampling and analysis only, oil slicks on the water surface and beaches become immediately visible. Direct effects of oil pollution on marine and coastal habitats and wildlife can be identified suddenly upon occurrence whereas the effects of many other, in particular dissolvable pollutants can be identified indirectly and in longer terms only.

On the other hand one has to bear in mind that crude oil and main constituents of oil products are combustion products of organisms transformed under long-term acting geological conditions. These have been and are always in traces and small concentrations in the marine environment which has to some extent adapted thereto. This is the reason that oil has a significantly higher rate of biological combustion by marine organisms than many other environmentally harmful substances.

Behaviour and Residence of Oil in Seawater and Coastal Zones
The behaviour and residence of oil in seawater and ashore is a complex interaction between many factors and depends on many factors (see also below). In overall the following processes can be demarcated and below given residence times and associated environmental impacts can be outlined.

The photos below shall give an impression and overview on the diversity and effects of oil in different marine and coastal environments and conditions.

Freshly spilled oil in calm sea An oil spill in waves and surf Oil spilled over ice sheets An oil polluted reef Burning tanker and oil spill Large drifting and stranded tar balls Heavy oil pollution on a rock coast A broad beach heavily oil polluted Drifting tar balls at sub-tropic coast Oiled roots in mangroves Oiled Spartina grass in wetlands Oil in a shallow sea grass weed Photos courtesy of the United States National Oceanographic Administration (NOAA)

The close-up photos below provide an impression on various types of stranded oil on different beach formations and sediments

Small pellets of oil “milk-shake” oil mousse on a sandy beach Oil pollution on a beach covered with coarse sandy sediments Pockets of oil on a heavily polluted rock and gravel covered beach Dispersed oil over the inter-tidal tidal range and wave reach Re-spilled oil from beach cleaning and wash-up spill response work Measuring the penetration depth of stranded oil into beech sediments Photos courtesy of the United States National Oceanographic Administration (NOAA)

The photos below illustrate some secondary effects of oil pollution and re-mobilisation

Dispersed oil over the inter-tidal tidal range and wave reach Re-spilled oil from beach cleaning and wash-up spill response work Measuring the penetration depth of stranded oil into beech sediments Photos courtesy of the United States National Oceanographic Administration (NOAA)

Short-term environmental effects and damages
As for every pollutant or harmful substance released into the environment it is of critical evidence for impact minimisation to recover as much as possible prior it is spreading, diluting and dispersing in the sea. Consequently short-term minimisation and mitigation measures have the most beneficial effects to decrease negative effects for marine and coastal environments and thereof resulting damage. The short-term effects of oil spills can be summarised as follows:

The short-term development and fate of oil spills as well as the damage caused by oil to the marine environment have very different characteristics. This depends on factors like:

• Amount of released (e.g. fuel oil, cargo, tank washing, type of accident)
• Characteristics of the spilling source (vessel on transit, moored or adrift, size of leakage, temporal evolution of oil release, ignition of oil)
• Type, physical and chemical properties of oil (e.g. viscosity, density, hydrocarbon-composition, evaporation, solubility – note that almost each oil field and oil sort has its typical characteristics and unique finger print – note: viscosity rage of oil spans from consistencies like water (light), molasses (medium) or tar (heavy oil)).
• Meteorological conditions (wind and current speed and direction, air temperature)
• Oceanographic conditions (wave climate, current speed and direction, sea water temperature and density)
• Hydrographic conditions (water depth, seabed and coastline shape)
• Morpholocigal conditions (sediment type of seabed and beaches)
• Biological conditions (underwater and coastal vegetation, flora and fauna in affected areas, type and sensitivity of ecosystems)
• Applied spill response, combating and mitigation measures

Above frame conditions result in complex interactions and interferences which make it very difficult to predict evolution and fate of spilled oil as well as the resulting negative effects on marine and coastal environments and ecosystems.

The photos below give impressions on different types of oil spills as a result of tanker accidents and oil spill incidents as well as in offshore oil exploration, production, and storage.

The tanker Amoco Cadiz ran aground off the coast of Brittany (France) on March 16, 1978. More than 300 million litres of oil. This is currently the sixth largest spilled oil amount in history. The tanker Exxon Valdez grounded in Alaska on March 24, 1989 on Bligh Reef in Prince William Sound. About 50 million litres of crude oil spilled into Prudhoe Bay and about 190 million litres lightered and safely transferred ashore The IXTOC I exploratory well blew out on June 3, 1979 off Ciudad del Carmen, Mexico. Until the well was brought under control in 1980 more than 610 million litres of oil had spilled into the bay (presently the second biggest spill in history). On 8 June 1990 the ultra-large crude oil carrier Mega Borg released more than 22 million litres of crude oil as the result of a lightering accident and a subsequent fire about 60 nm southeast of Galveston (Texas). Deliberate oil releases during the 1991 Gulf War comprised the so far biggest amounts of crude oil spilled into a single marine area in a short period of time. The aerial photo shows an oiled coastal strip in Saudi Arabia. A smaller oil spill incident as caused for instance by the crude oil product carrier Tenu Maru outside the entrance to the Straight of Juan de Fuca discharging about 0.9 million litres of petroleum products in to the sea. Photos courtesy of the United States National Oceanographic Administration (NOAA)

Recommendations and Practices for Short-term Response
As general recommendations for short term actions the following can be given:

• The sooner it is possible to capture, lighter or recover spilled oil from the water surface or, even better, from a disabled vessel, the lower are the environmental impacts and damages of an oil spill. Hence response time and ability to act at site is the critical factor and, most likely, has the biggest potential for optimisation in oil spill response and damage mitigation.
• Once oil is dispersed over larger areas, has developed to thinner slicks and is partly dissolved in the water column the resulting environmental (and economic) damage increase substantially.
• Correspondingly clean-up and spill response measures become more difficult (if not impossible) and costly.

In longer terms residues of oil spills disappear to a considerable extent from the water column by biodegradation, weathering, sedimentation and stranding (including removal by human intervention). Compared to other environmentally harmful substances crude oil and crude oil products are much better degradable by the biota.

The table below tries to compactly summarise long-term effects and environmental damage of oil pollution in the marine environment versus such caused by other harmful substances.

It is still under debate and a matter of scientific research to which extent non-combusted or longer persistent residues of oil spills are environmentally harmful and which are especially eco-toxic and whether these may cause long-lasting chronic effects and permanent stress on marine and coastal environments and ecosystems. The general opinion is that especially coastal sites almost entirely recover after a period of 5 to 10 years after oil spill damage.

However, some of the few conducted long-term studies and site monitoring activities indicate some negative influence beyond this time scale. However, all serious ones admit that these indications are highly masked by natural variability, lifecycles and dynamics of individual species abundance and stocks and, moreover, regarding development and dynamics of communities of animals and plants. As these are also significantly influenced by other natural and anthropogenic processes and their variability it is difficult if not impossible to directly identify whether findings from observation and monitoring results are directly or indirectly resulting from a former oil spill damage.

A notable example for long-term monitoring results and above depicted uncertainties is Mearns Rock – a large boulder in the inter-tidal zone of Price William Sound (Alaska) which is regularly monitored since 1990 after the oil spill damage caused by the Exxon Valdez stranding. Within the first 4 years gradual restoration with region-typical plants, followed by barnacles and mussels occurred. Thereafter (1996) a major drop or change occurred followed by a second growth cycle, subsequent die-off (2002) and subsequent recovering. Long-term effects of the oil spill damage are almost impossible to quantify as they appear to be masked marine plant and species lifecycles as well as variation and variability of environmental conditions. 1990 – 15 months after the spill Oil originally covering the rock has entirely disappeared and young plants of commonly abundant, so called “rock weed” grow in its surface. 1993 “Rock weed” covers about 20% of the surface, older plants died off and were replaced by young ones. Mussels and barnacles also grow on the rock feet. 1994 Plants have almost entirely disappeared and the rock sides are heavily populated by mussels. 1999 The rock is thickly covered with older “rock weed” which began to grow again in 1995-96 after the first die-off. 2002 The rock’s top is rather bare (plant cover on top less than about 15%) and sides are covered with barnacles but no with mussels as 1994. 2004 The rock is again covered with young “rock weed” as well as considerable amounts of barnacles but still with no mussels. Refer to the web pages of NOAA (see repository) for detailed descriptions. Photos courtesy of the United States National Oceanographic Administration (NOAA)

Newer findings shown that in many cases oiled beaches and sites recover similar or even better when not being cleaned. Especially cleaning with high vapour pressure and vacuum cleaners which is very efficient for oil removal from rocky coasts lines have negative effects as they simultaneously destroy biota and species communities on surrounding non-oiled spots which are the source for natural recovery. Investigations show that in many cases beaches and shorelines recover similarly regardless whether being cleaned or not.

Even more, the use of dispergent agents to increase oil viscosity can have considerable negative side effects on the environment which can increase the estimated or virtual benefits from their use. It is therefore forbidden in many cases and areas that dispergents are used for instance by vessel masters in case of an oil spill incident without prior consideration of experts and subsequent permission from authorities.

Oiling of beach surfaces declines relatively quickly. Post-spill damage and recovery monitoring of beaches usually show a relatively rapid decline of surface oiling from typical initial below values between typically 50% and 100% (depending on grades of initial pollution and height respectively exposure to tides and waves of the terrain) to well below 1% within typical periods of 2 to 3 years. Typical reduction factors of surface oiling after peak values 1 year are in the range of 5 to 10.

Inter-tidal areas higher beach areas which are wetted by higher waves or water covered at high tides only show increasing tendencies of oil coverage for a period of about one year after a spill has stranded. This is due to the fact that oil deposited on lower areas can be still washed away and deposited on higher altitudes (especially when the spill stranded not around high water). Thereafter the decrease in surface oiling shows similar behaviour also in the higher levels of the coast. Details, however, depend on lots of factors like the oil sort itself, exposure to sun light or soil type as well as on abundance and composition of the biota.

Oil which is buried or has entrained deeper sediment and soil layers remains much longer in the environment and disappears much slower this can be well seen in sand cuts. Buried oil can reach the surface again by erosion of soil or sediments as well as by excavation by benthic organisms (especially worms, crabs, clams and mussels).

Heavy or solid oil compounds like tar and asphalt can remain much longer on the surface and seals it off. Also pockets and small ponds with heavy oil compounds are frequently found in areas with former oil spill damage many years after the spill has stranded.

Residual oil found in beach sediments found 9 years (1998) after the Exxon Valdez spill in Prince Williams sound (Alaska). The right photo shows mobilised liquid oil and sheen, the left one heavily oiled sediment in an undisturbed pool. Photos courtesy of the United States National Oceanographic Administration (NOAA)

5.1.2 Environmental Sensitivity, Vulnerability and Recovery Capacity

The identification and assessment of the sensitivity and vulnerability of marine and coastal environments with regard to oil spill damage provides the baseline information and input for decision making for both short- and long-term response and recovery planning and actions.

Open Waters

Open waters are generally considered as less sensitive for oil spill damage in particular if located further offshore. Reasons for this are mainly in their less dense or sparser population of sea birds and marine mammals and their lower evidence as habitats, spawning or breeding grounds.

On the other hand oil pollution (especially in longer terms) is less visible and detectable in vast open sea areas and once the oil has disappeared from the sea surface it is much more difficult if not impossible to detect. Moreover, oil compounds and pelagic biota is highly movable by ocean currents (and higher trophic animals also by themselves). For many open water areas species composition and functioning of marine ecosystems are sparsely known.

Hence in the medium to long terms it is very difficult to estimate in detail whether and to which extent larger areas of open waters have been affected by oil spill. Without baseline data and information the assessment of oil spill damage to environments and ecosystems is almost impossible and consequently estimation of sensitivity and vulnerability almost impossible.

In general, but within aforementioned limitations, the following sensitivity and vulnerability of open water ecosystems ranking can be given.

Coastal Waters and Coastal Zone Environments

Costal waters and zones are usually the most richest and productive marine environments and hold the highest biodiversity in the oceans. This applies for the water column, the shoreline and the seabed.

Large and very notable and visible damages occur to coastal zones in case oil is stranding. Seabirds breeding and feeding in coastal areas can get oil with a high rate of mortality. The same applies for abundant mammals with, however, usually lower mortality rates. Benthic organisms, fish spawning and grow-up areas are usually heavily damaged. The same applies for coastal and seabed vegetation.

Human assets such as aquaculture installations, tourism and leisure facilities but also infrastructure and industrial installations and, more general, work and social life can get heavily interfered and disturbed both in short and medium terms.
Clean-up of coastal zones and shore areas is usually a large mess and involves big capacities of personnel and equipment. Another problem is environmentally safe dumping of contaminated soil and oil residues.

Sensitivity and vulnerability of coastal zones depend on the characteristics of the affected coastal area (see below) but also on a series of hydrodynamic (eg waves and tides), ecosystem and socio-economic factors.

Polar Regions

With nowadays increasing oil and gas exploration as well as sea transport activities in offshore Sub-arctic and Arctic areas which are temporarily or permanently covered with sea ice oil spill damage and its mitigation become high relevance in marine environmental protection.

Due to the cold temperature and accordingly the reduced chemical reaction capacity evaporation, decomposition and degradation of oil is greatly reduced or delayed. Correspondingly residence times are increasing and especially the more dangerous light oil composites remain much longer in the environment.

When oil is spilled in ice it diffuses into cracks and pockets (especially in young sea ice which has a high degree of porosity). Oil is also spreading under the ice and between ice sheets. By ice drift (refer to the circum-polar ice drift) and mechanical properties (eg levelling, ridging, break-up, re-freezing) spilled oil in ice is widely diffused and dispersed. Stranded or sunken oil compounds can be easily remobilised by ice action (eg by uptake of temporary stranded or grounded ice sheets and ridges). When oiled ice melts either by drifting into warmer waters and areas or by seasonal warming the enclosed oil is remobilised and released to the water surface and water column.

Due to the slow growth and decay processes typical for arctic environments biodegradation as well as recovery and re-growth of oiled coastal areas is greatly delayed. In certain areas wildlife concentrates permanently or seasonally on relatively small spots. In summertime the globally abundant stocks of some bird species breed and feed in a few very small areas. If such areas are severely damaged by an oil spill the entire species is severely affected. Long-term environmental and ecosystem damages are almost impossible to estimate as the knowledge on arctic lifecycles and ecosystems is still very poor.

Almost all oil spill combating methods and equipments do not work in Arctic waters. In ice equipment like booms or classical uptake devices are simply smashed by ice pressure, loads and forces. Most areas are barely possible to access and capacities of appropriate transport devices as well as of clean-up personnel are very low. This plus the harsh weather conditions and their rapid changes make large spill combating activities almost impossible. Some specialised equipment recovering small amounts of oil in ice as possible to occur for instance during fuelling or small-scale loading operations have been developed. However, their application possibilities and recovery potential is very limited.

Utmost care must be taken to avoid oil spills in arctic regions in any case. Combating devices and trained staff has to be on site in advance as it is rather unlikely that these can be transported in appropriate time and in relevant amounts and numbers to an incident site.

Deep Water Areas

Increasing activities in oil exploration and production along continental margins and in deep water areas has raised great concerns on oil spill risks and mitigation also for these regions.

Oil production in deep waters brings along risks of a new type of incident – an oil spill in large water depth. Such may happen by deep water well blow outs or leakage of risers in larger water depths. At present the knowledge on spill behaviour in large water depths and under high pressure is very rarely known.

In overall there is very little knowledge on species composition, functioning and sensitivity of deep water ecosystems (almost each larger deep water research cruise brings new findings and surprises). There is also very little knowledge on the behaviour of oil in deep water and how oil compounds slowly sinking through cold and dark deep water column may affect the environment.

In mind of these uncertainties utmost care, redundancy of safety devices and equipment as well as high levels of training in spill prevention and avoidance is the best practice to apply.

Vulnerability Assessment, Mitigation and Response Planning

In developed and also most emerging countries it has meanwhile become common practice to assess and map sensitivity of coastlines and marine regions. Also a series of policies and requirements oblige countries to monitor the condition and quality of their environments including coastal and marine areas.

On the global scales obligations posed by regulations regarding the Exclusive Economic Zones (EEZ) require detailed assessments and monitoring activities. The same applies for the ongoing implementation of the Global Ocean Observing Systems endorsed by the United Nations. This is presently ongoing and fostered by a series of regional implementation initiatives like EuroGOOS in Europe, NOOS for the North Atlantic, BOOS for the Baltic Sea or MEDGOOS in the Mediterranean.

In Europe especially the Water Framework Directive (WFD) and its extension towards coastal zones and marine areas pose certain requirements in this conjunction and all member states of the European Union are obliged to intensively assess and monitor their coastal waters.

In addition several areas and marginal seas have special protection status and related activities and policies are backed by trans-boundary and multi-national agreements and treaties. Such are in Europe for instance OSPARCOM for the North Sea, HELCOM for the Baltic Sea, or the Rome Convention for the Mediterranean. Even more strict regulations apply in specifically protected or sensitive sub-areas like in Europe the Wadden Seas, the Adriatic Sea and as serious of specific areas important for feeding and breeding of migrating birds or vital for sustainable stocks of fish and other marine livestock.

Also special policies and regulations apply for very sensitive areas like mangroves, wetlands, coral reefs and certain arctic areas. The Antarctic Subcontinent and its surrounding waters is entirely protected form fossil energy and mineral excavation by the Antarctic Treaty.

ESI – the Environmental Sensitivity Index

Although difficult to generalise a commonly agreed series of indices was developed throughout the last decades. The ESI for marine shores and coastal areas ranks environmental sensitivity in terms of numbers (1 – low to 10 – high sensitivity) and associates these to specific types of coastal zones and habitats.

With respect to oil pollution sensitivity of coastal zones highest sensitivity is indexed to mangroves and coral reefs and high sensitivity to coastal wetlands and inter-tidal flats. Sand, gravel and rock coasts are usually indexed with the lowest sensitivity.

Sensitivity Mapping

It has become common practice that coast lines and coastal zones are mapped
Nowadays GIS systems are usually applied for environmental sensitivity mapping. These allow multi-layered processing of geographical and environmental data and information (e.g. coastlines, topography, water depth, vegetation, species abundance, settlements, assets, sensitivity ranking, areas of specific priority and sensitivity for spill combating and damage control).
Environmental sensitivity mapping provides the baseline data and background information for response and contingency planning as well as for concrete spill response and damage control actions and selection of procedures, application of technologies and definition of equipment and inventories.

It has also become more and more practice to make this information widely available so that all involved bodies can access the information and use it for individual planning and activities.

Response and Contingency Planning

The establishment of response and contingency plans to avoid and minimise oil spill damage has become common practice. Such plans are applied in the public sector for protection of coastal regions, territorial waters and in many cases also exclusive economic zones of a specific country. Partially, although still less frequently, these are extended across territorial boundaries towards regional protection plans.

It has become common practice in the oil and gas industry and the marine transport sectors to develop and implement field, site or plant specific response and contingency plans.

Spill response and contingency plans describe in detail related operation and work procedures along the entire chain of activities (e.g. reporting, alarming, setting of priorities for countermeasures, composition of response teams and inventories of equipment, damage control and clean-up procedures, safety and health issues, training, maintenance).

Best Practices

Both governmental agencies as well as the offshore oil and gas, marine transportation and shipping industries have developed and constantly review and refine best practices which diminish the occurrence risk of oil spills as well as the minimisation and mitigation of damages to the environment in case spills occur. Certification and supervision bodies incorporate these accordingly in rules and guidelines and issue respective certificates.

There exists a series of best practices plus related codes and regulations for the oil and gas industry whereas the most advanced ones are implemented in Europe, the United States, Canada and Australia.

In addition operators of offshore oil and gas production, loading, transportation and storage facilities apply site and plant specific guidelines and practices which are usually documented and implemented in related safety, environment and health procedures and manuals as well as in site- and plant-specific contingency and response plans.

Copyrights and Crediting of Photos and Graphics included in this Section
All photos and graphs in this section are treated in compliance with individually and applicable copyrights and/or terms and conditions of use. They are credited, referenced or cited accordingly. Third party copyrights have been considered as applicable and have been, where required, permitted for use in this course by the individual copyright holders.