Catastrophic Events

A catastrophic event in Cook Inlet may be the result of a natural or anthropogenic event. Regardless of source, the potential for injury or mortality of CI belugas exists. A catastrophic event could directly affect CI belugas (e.g., harm due to spilled contaminants), or could indirectly affect them through effects upon their habitat or prey. A catastrophic event may also be a contributing factor to a mass stranding event. A mass stranding resulting in numerous mortalities would be catastrophic to the recovery of CI belugas; as such, we consider mass strandings as a potential catastrophic event.

Potential Sources of a Catastrophic Event

Several natural factors may result in a catastrophic event with potential to adversely affect CI belugas, including effects from environmental or climatic changes, earthquakes, volcanos, disease outbreaks, lethal mass strandings, and failures of key salmon runs. Anthropogenic events, such as oil spills and natural gas blowouts, may also have detrimental effects on CI belugas. Catastrophic events may also affect CI beluga prey, whether through changes to spawning or migration patterns, direct mortality, or potential long-term sub-lethal impacts (Moles et al. 1994; Marty et al. 1997; Murphy et al. 1999).

The State of Alaska maintains a record of all spills of harmful substances. From 1994 to 2011, there were 255 events in or near Cook Inlet releasing more than 100 gallons or 100 lb (378.5 liters or 45.4 kg) of reportable substances (Alaska Department of Natural Resources, Division of Oil & Gas, 2011, unpub. data). These spills included 90 events releasing a total of 84,195 gallons (318,713 liters) of various types of oils (diesel, hydraulic, gasoline, engine lube, aviation fuel, and natural gas); 48 events releasing a total of 25,404 gallons (96,165 liters) and 11,364,847 kg (25,055,199 lb) of hazardous materials (bases or alkaline substances, drilling muds, glycols, and urea); and 73 events releasing 110,332 kg (243,241 lb) and 1,574 gallons (5,958 liters) of extremely hazardous substances (anhydrous ammonia, hydrochloric acid, and sulfur dioxide). The most significant events releasing more than 10,000 lb or 10,000 gallons (4,536 kg or 37,854 liters) are listed in Table 7 (Alaska Department of Natural Resources, Division of Oil & Gas, 2011, unpub. data). There are no reports of CI belugas being directly impacted by any of these events.

Belugas may live-strand in response to a variety of natural and anthropogenic stimuli that may occur singly or in combination, including predator avoidance, chasing prey, changes in water flow, disease, illness, injury, acoustic events, or catastrophic events. Belugas are usually able to survive through a live stranding event and escape to deeper water on the rising tide. However, some deaths have occurred from these events (see Table 5). If a large number of mortalities were associated with a live stranding, the effects on the population could be catastrophic. Fortunately, mortalities associated with a live stranding event do not appear to be common. The last mortalities suspected to be associated with a live stranding event were in May 2014 when two CI belugas were found dead with evidence of glacial silt in their lungs (NMFS AKR, unpub. data). Although NMFS received no reports of a live stranding, the presence of silt in the airway is indicative of a likely live stranding event. Prior to 2014, the last suspected mortalities from a live stranding event were in 2008 (Table 5). For the purposes of this section, we would consider mass mortalities associated with a live stranding as a catastrophic event.

Relative Concern

Effects from catastrophic events are variable, ranging from mortality to compromised health or injury to individual whales, reduced overall fitness or resilience of the population, or reduced carrying capacity of the environment. A catastrophic event resulting in CI beluga mortality will increase the likelihood of extinction, currently projected at 0–14% probability in the next 100 years (Hobbs et al. 2015c). A catastrophic event in which only carrying capacity was affected will likely have minimal impact to CI belugas because the population (300–400) is small compared to carrying capacity (K = at least 1,300). Compared to other effects of catastrophes, decreased survival and fecundity have a much greater impact on recovery than does a decrease in carrying capacity. For example, an anthropogenic spill of some chemical in a marginal area of habitat would result in limited exposure of CI belugas to that chemical. However, a spill in a more centrally located area will increase the exposure of CI belugas and increase the severity of the impact, to the point recovery of the population could be delayed (Hobbs et al. 2009).

Small populations, such as CI belugas, may be more susceptible than large populations to adverse effects resulting from catastrophic events. The reduced summer range of CI belugas into the upper Inlet makes them vulnerable to catastrophic events that have the potential to kill or injure a significant portion of the population. It is expected that most catastrophic events would be localized events, affecting only a portion of the CI belugas’ range. However, depending on the location of the event, the exposure or effect to the whales will vary. With the exception of live strandings, a catastrophic event in lower Cook Inlet which occurs in the summer when most CI belugas are in the upper Inlet will have less effect than if the same event were to occur during summer in the upper Inlet. Fortunately, the frequency of catastrophic events in Cook Inlet has been low, and such events occur only intermittently. Although past experience indicates the frequency of catastrophic events is low, anthropogenic activity in Cook Inlet is increasing, and environmental and climatic conditions are changing; accordingly, we infer that the probability of a catastrophic event occurring in the future will be higher than it has been, and thus we categorize this probability as medium to high. The magnitude of effect of a catastrophic event on CI belugas is assumed to be variable and dependent upon several factors including type of event, location of event, timing of event, and exposure of whales to the event. However, we ranked the magnitude as variable, but potentially high given the fact that mortalities from live strandings or other catastrophic events would have a greater and more immediate adverse effect on the recovery potential of the population than other types of effects (e.g., behavior modification; reduced carrying capacity). When we consider all these factors, we conclude the overall relative concern of the impact of catastrophic events on CI belugas to be of high concern.

Table 7. Events releasing more than 10,000 pounds or gallons of reportable substances into Cook Inlet, 1994– 2011.
Type
Y ear
Spill name/description
Region
Quantity
Unit
Substance
Refineries, pipelines, and production 2003 to 2008 Agrium Ammonia Nikiski 78,123 Pounds Ammonia, anhydrous 37 Events
Refineries, pipelines, and production 2008 Aurora Gas Moquawkie West Kenai 11,000 Gallons Drilling mud
Refineries, pipelines, and production 2004 Marathon Beaver Creek Fire Beaver Creek Field 21,000 Gallons Natural gas liquid
Refineries, pipelines, and production 1995 to 1996 UNOCAL Central Kenai 57,940 Pounds Ammonia, anhydrous 16 events
Refineries, pipelines, and production 2008 to 2009 Tesoro Refinery SO2 Nikiski 104,595 Pounds Sulfur dioxide 13 Events
Refineries, pipelines, and production 1999 UNOCAL SRF Swanson River Field 10,500 Gallons Produced watera
Vessels 1997 Crowley Oregon Barge South Cook Inlet 25,000,000 Pounds Urea (solid)

a The water produced when oil and gas are extracted from the ground.

Source: Alaska Department of Natural Resources, Division of Oil & Gas, 2011, unpub. data.

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