| Noise disturbance and pollution are associated with all phases of offshore petroleum exploration and production, accompanying seismic surveying, drilling, air and ship support and the operation of onshore and offshore facilities. 3.1 Noise and Disturbance. The potential for cetaceans to be affected by loud noise has become of increasing interest recently. Cetaceans rely heavily on sound for communication, food finding and obtaining information about their environment. It is suspected that noise may interfere with, or mask communication, disturb or harm cetaceans. Potential effects range from altered behaviour and physiological damage to ear structures, to stress, displacement from preferred areas or interrupted feeding. However, the effects of disturbance on cetaceans are poorly understood. Disturbance is often measured by observations of behaviour. Cetaceans reactions to noise include cessation of normal activities such as feeding, socialising, or vocalising and avoidance of the noise source - whales may dive or swim away. The longer term effects of altered behaviour, displacement and stress are not known. Several reviews provide comprehensive coverage of the documented reactions to, and potential effects of various forms of disturbance of whales and dolphins. These include (Richardson et. al. 1991) (Richardson et. al. 1995) (Gordon and Moscrop 1996) (Evans and Nice 1996) (Reeves 1992). Much research, to date, has focused on the bowhead whale (in the Beaufort Sea) and the gray whale (off the US west coast).
The potential effects of loud noise and disturbance may be divided into: Physiological Effects a) Damage to Tissues Shock waves (from explosions and other very loud sound sources) can cause direct tissue damage. For example, they can kill fish with swim bladders and cause haemorrhage in lungs and ulceration of gastrointestinal tract in mammals (Turnpenny and Nedwell 1994) (EPA 1974) (Yelverton et. al. 1973) (Myrick et. al. 1990). b) Damage to Hearing Structures Rapid pressure change can cause discomfort, sensory effects and permanent hearing damage. In extreme cases, eruptive injury to the inner ear may result. Ear damage has been discovered in seals following explosions (Bohne et. al. 1985, 1986) and in humpback whales found dead in an area characterised by industrial noise (underwater drilling, dredging and blasting) (Ketten et. al. 1993) (Ketten 1993) (Lien et. al. 1995). These studies reveal that animals may tolerate very loud sound despite experiencing physiological damage, when previously it was accepted that animals would move away from an area before sound levels became uncomfortably high. It is obvious that this does not always occur and so physiological damage (particularly to the hearing structures) may be more common than previously thought. In the case of humpback whales, the whales in the area showed little reaction to the noise, in terms of distribution, displacement from the area, movements or behaviour (Lien et. al. 1993). Entrapment in fishing gear increased significantly during the period of industrial activities, and it is possible that the long term exposure to high noise levels decreased the whales sensitivity to acoustic stimuli (Todd et. al. in press). c) Hearing Threshold Shifts (due to a reduction in sensitivity of hair cells within the inner ear). This is expected to occur in cetaceans as in other animals. Andre (pers. comm.) has suggested that sperm whales off the Canaries may possibly be experiencing increased collisions with ferries due to damage to their ears. Hearing damage may result in them being unable to detect the approaching vessels clearly enough to take avoiding action. Humpback whales affected by industrial noise may similarly have had their hearing compromised, and this may have led to increased net entrapments in the vicinity (Lien et. al. 1993) (Todd et. al. in press). d) Chronic Stress Stress-mediated effects due to noise have been observed in other species of birds and mammals (Fletcher 1971) and include lowered resistance to disease, increased vulnerability to environmental disturbances and endocrine imbalances which may affect reproduction (Geraci and St Aubin 1980). Behavioural Effects a) Masking and Interference with Communication Rising levels of man-made noise in the oceans prompted Payne and Webb (1971) to express concern for long distance, infrasonic communicators such as fin and blue whales, which they considered may be suffering from masking of communication by anthropogenic sound. Low frequency vessel noise is known to mask fin whale vocalisations, and higher frequency vessel noise similarly masked minke whale sounds in the St. Lawrence estuary (Edds and Macfarlane 1987). Faucher and Whitehead (1991) believe that Northern Bottlenose whales may be affected by increasing levels of ship traffic and other noise in 'the Gully' off Nova Scotia. Noise may mask the very low amplitude social sounds made by these whales. b) Altered Behaviour Animals may cease vocalising, cease socialising, make hasty dives or attempt to avoid noise sources. Boats which emit strong noise or change direction rapidly may cause baleen whales to alter their behaviour and move rapidly away from the area. Avoidance may be acute if the boat heads directly at the whale. Some whales move several kilometres away in response to a straight line pass by a vessel. Avoidance reactions are not always successful in preventing collisions, and this is a particular problem for right whales (Richardson et. al. 1995). Off New Zealand, some sperm whales were found to avoid whale watching vessels at up to 2 km away, with responses including altered surfacing-respiration-dive patterns and increasingly erratic surface movements (Cawthorn 1992). Close to the boats, the whales tended to spend less time at the surface, with fewer blows per surfacing, shorter intervals between successive blows and increased frequency of dives without raised flukes (Gordon et. al. 1992). Sperm whales appear to react to seismic pulses at long ranges. In the Gulf of Mexico, sperm whales moved away from an area of seismic operations to locations over 50 km distant when seismic surveys began (Mate et. al. 1994). In the southern Indian Ocean, sperm whales and pilot whales ceased vocalising during some periods when relatively weak seismic pulses were received from an airgun over 300 km away (Bowles et. al. 1994). There are anecdotal reports of sperm whales behaving 'very oddly' in the vicinity of seismic operations off Scotland (Goold pers. comm.). Seismic surveys also involve the use of sonar to conduct bottom profiling. Some odontocetes, particularly sperm whales are known to react to sonar pulses and other pingers (Reeves 1992) (Watkins et. al. 1985, 1993). Low frequency sonar pulses also elicited avoidance responses in humpback whales (Maybaum 1993). Low levels of seismic noise may have subtle effects on the surfacing and respiration patterns of baleen whales. Strong seismic pulses elicit active avoidance, although they may tolerate low and moderate level noise from distant seismic vessels. They show strong avoidance at several kilometres from the array and may be displaced by several kilometres. Normal behaviour may also be altered for over an hour, including cessation of feeding, resting and socialising (Richardson et. al. 1995). c) Displacement Displacement as a result of industrial activities (dredging, vessel traffic, oil production) has been documented, for example, in gray whales in Baja California (Bryant et. al. 1984), and bowhead whales in the Beaufort Sea (Richardson et. al. 1985). There are anecdotal reports that whales abandon areas with heavy and uncontrolled vessel traffic (Nishiwaki and Sasao 1977) (Reeves 1992). Bowhead and gray whales appear to avoid areas of heavy vessel traffic (Richardson et. al. 1995). During the Heard Island Feasibility test in the southern Indian Ocean (Munk et. al. 1994), sighting rates for medium-sized and large whales including pilot, beaked and balaenopterid whales were lower than before transmissions (Bowles et. al. 1994). Recent studies by John Goold (e.g. Goold 1996) suggest that dolphins may be displaced by seismic activities. During studies off Wales, bow-riding by common dolphins, which had been frequent, ceased when firing began. Acoustic contacts with the dolphins also dropped sharply as soon as firing began. Analysis of the sound produced by the seismic array indicated that dolphins less than a kilometre away might find the noise discomforting enough to displace them. The blasts, Goold suggests, are likely to be even more uncomfortable to larger whales which have more sensitive hearing at low frequencies. Baines (1993) provided evidence that harbour porpoises and bottlenose dolphins were temporarily displaced by seismic operations in Cardigan Bay. Conversely, dolphins have been observed close to seismic vessels when firing, and there are apparently anecdotal reports from crew members on seismic boats that dolphin 'play' around the guns, swimming out before the guns fire and returning afterwards, possibly to swim in the bubbles produced by the guns (Stronarch 1993). It has been postulated that increasing levels of noise in the deep waters, north and west of the British Isles, may be deflecting some sperm whales to the east, perhaps resulting in the unusual appearances (and strandings) of sperm whale in the North Sea in recent years (Gordon pers. comm.) (Goold pers. comm.). d)Energetic Consequences Negative effects may result from repeatedly interrupted feeding. The effects of disturbance may be particularly acute on deep diving whales such as sperm whales, beaked whales and pilot whales, which need to spend periods of time at the surface replenishing oxygen supplies to facilitate deep foraging dives (Gordon and Moscrop 1996). Migrating and lactating whales, with finely tuned energy budgets, may also be negatively impacted by disturbance which may result in flight (avoidance) when disturbed, diversions during migration, interruptions to feeding etc. e) Increased Stress Animals may stay in an area, despite disturbance, due to limited alternative habitat. This may induce stress and possible harmful physiological effects (Seyle 1973), about which very little is known in cetaceans. The long term effects of noise and disturbance (for example, on reproduction rates, distribution and habitat use) are not known. For example, on the west coast of the US and in the Beaufort Sea, gray and bowhead whale populations have continued to use areas and migration corridors which have been subject to seismic operations for many years. It is not known whether the same individuals return to areas of previous seismic exposure, whether seismic operations have resulted in local changes in distribution and migration routes, or whether whales that tolerate strong seismic pulses are stressed (and the possible effects that this stress may have) (Richardson et. al. 1995). Seismic Operations West of Shetland Seismic surveys are best conducted in calm seas conditions, during the period April to September. Historically, upon the award of a license for oil exploration purposes, the Government attached constraints to the licence in terms of the activities allowed on that block, which often related to the possible effect of seismic operations on fish on the advice of the Scottish Office Agriculture and Fisheries Department (SOAFD). Seismic surveys have been blamed as one of the reasons for reduced seasonal fish catches from the North Sea. Known effects on fish include damage to fish and eggs and displacement of fish (Turnpenny and Nedwell 1994). In the past, cetaceans were not considered in the licence conditions. However, increasing attention has been focused on the potential effects of seismic operations on cetaceans. The UKOOA have recently sponsored a review of the effects of underwater sounds from seismic surveys on cetaceans (Evans and Nice 1996). This concluded:
1. The choice of when to conduct a seismic survey should be dictated by the relative vulnerability of the species present. For example for minke and fin whales, the period of least impact would be November to March (the worst period for seismic surveys). The JNCC has started to attach conditions regarding cetaceans on licence blocks, and have in consultation with UKOOA, produced a series of guidelines regarding cetacean monitoring for use during seismic operations. This recommends:
1. Keeping a log of all visual cetacean sightings (to be forwarded to the JNCC on completion of a survey) However, it is important to note, that seismic surveys are conducted by independent operators which are autonomous, (although contracted) by the oil companies. Also some species of cetacean are especially difficult to detect visually (and therefore difficult to avoid disturbing during seismic surveys). Sperm whales, for example remain submerged for long periods (often an hour or so) and so may be present in an area, but undetectable visually. Indeed it is when they are diving (and undetectable visually) that they may be particularly vulnerable to seismic survey noise. Similarly, harbour porpoises are difficult to detect visually. The presence of both of these species is more reliably detected acoustically. In the 'west of Shetland' area, environmental issues are being evaluated and managed by all operators jointly, led by Shell. Environmental initiatives include improved cetacean monitoring capability (incorporating visual and acoustic monitoring) as part of seismic surveys and, a major research project sponsored by a consortium of 14 oil companies (the Atlantic Frontier Environmental Network), through JNCC and Cornell University. This project is aimed at monitoring and tracking large cetaceans in the Atlantic (and west of Shetland) using redundant US and Royal Navy hydrophones, the so-called IUSS sound surveillance system chain. 3.2 Oil Pollution Despite the fact that much hydrocarbon resource development is concentrated in areas which are feeding and breeding grounds for cetaceans (including the Gulf of Mexico, the Californian coast and the Beaufort Sea) relatively little is known about the effects of oil on cetaceans, in the long or the short term. Oil is composed of aliphatic and aromatic hydrocarbons. Aliphatics are responsible for the smothering qualities of oil and aromatics are generally highly toxic (many, such as polycyclic aromatic hydrocarbons, PAH's, are carcinogens) (NAS 1985). At high exposures, aromatic components can induce death in organisms (NAS 1985). Sub-lethal effects include changes in physiology, decreased growth and reduced reproductive success. Such effects have been reported in birds and turtles (Geraci and St. Aubin 1987). Genetic damage may also occur as a result of exposure to petroleum hydrocarbons (NAS 1985) and it has been suggested that they may cause tumours in fish (NAS 1985). Polar bears, which died following exposure to crude oil were found to have lesions in their digestive tracts, brains, livers, lymph and bone marrow. There are many observations of cetaceans within oil slicks, but relatively few documented deaths related to oil (Geraci and St. Aubin 1980). Although cetaceans are known to be able to recognise (and avoid) thick and weathered oil in experimental conditions, lighter fractions and sheens can not be detected, and cetaceans do not necessarily avoid oil at sea (Geraci 1990). Such experimental results do not provide reassurances that cetaceans do not suffer from any longer term or chronic effects from their contact with oil. Cetaceans spend considerable periods of the time at the surface to breath, socialise, rest, swim and feed. They might be impacted by oil in several ways:
1. Physical smothering - cetaceans may become coated in oil Acute Effects
* Physical contact - fouling and irritation of the skin - cetacean skin is very sensitive. Petroleum compounds are known to irritate skin and mucous membranes, triggering an inflammatory response (Hansborough et. al. 1985). If contact persists, necrosis and inflammation occur. Experiments undertaken to assess the effects of oil on cetacean skin showed that the skin appeared to be an effective barrier to oil and even extended contact did not elicit a severe visible response, although biochemical and metabolic examination revealed subtle changes in cells exposed to petroleum (Geraci 1990).
* Inhalation of volatile fractions.
It can cause: Volatiles such as benzene and toluene are transferred rapidly to the bloodstream from the lungs. They accumulate in tissues such as the brain and liver resulting in neurological disorders and liver damage. The vapours of volatile fractions of petroleum hydrocarbons irritate and damage soft tissues, and depending on the duration of exposure and concentration of vapours, effects range from mild irritation to sudden death (Wang and Irons 1961). Cetaceans breathing air from immediately above the water surface would be exposed to high levels of volatiles, particularly a few hours after a spill. Animals which inhale petroleum hydrocarbons can suffer from effects ranging from death (as has been observed in humans (Bass 1986)), to irritation of the respiratory membranes and absorption of hydrocarbons into the bloodstream.
* Ingestion
Chronic Effects Marine fish also take up petroleum hydrocarbons from the water and their food. Metabolites of aromatic hydrocarbons are quickly formed and excreted. Some metabolites can bind to tissue macromolecules including DNA. Top carnivores such as killer whales may be less likely to be exposed to petroleum compounds than baleen whales which feed on zooplankton (Neff 1990). The threat from contaminated food is expected to be greatest to benthic feeders (as oil deposits may settle on the ocean floor) (Wursig 1990).
Species at Risk The potential impacts of oil pollution have generally been neglected in assessments relating to oil developments in Scottish waters (Thompson 1992). The extent of threats to cetaceans from oil pollution are uncertain, but Thompson (1992) considers that they deserve more attention, particularly where developments and shipping activities occur in important habitat, such as areas around Shetland and west of Shetland.
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