“Gas and Fat Embolic Syndrome” Involving a Mass Stranding of Beaked Whales (Family Ziphiidae) Exposed to Anthropogenic Sonar Signals

Abstract

A study of the lesions of beaked whales (BWs) in a recent mass stranding in the Canary Islands following naval exercises provides a possible explanation of the relationship between anthropogenic, acoustic (sonar) activities and the stranding and death of marine mammals. Fourteen BWs were stranded in the Canary Islands close to the site of an international naval exercise (Neo-Tapon 2002) held on 24 September 2002. Strandings began about 4 hours after the onset of midfrequency sonar activity. Eight Cuvier's BWs (Ziphius cavirostris), one Blainville's BW (Mesoplodon densirostris), and one Gervais' BW (Mesoplodon europaeus) were examined postmortem and studied histopathologically. No inflammatory or neoplastic processes were noted, and no pathogens were identified. Macroscopically, whales had severe, diffuse congestion and hemorrhage, especially around the acoustic jaw fat, ears, brain, and kidneys. Gas bubble-associated lesions and fat embolism were observed in the vessels and parenchyma of vital organs. In vivo bubble formation associated with sonar exposure that may have been exacerbated by modified diving behavior caused nitrogen supersaturation above a threshold value normally tolerated by the tissues (as occurs in decompression sickness). Alternatively, the effect that sonar has on tissues that have been supersaturated with nitrogen gas could be such that it lowers the threshold for the expansion of in vivo bubble precursors (gas nuclei). Exclusively or in combination, these mechanisms may enhance and maintain bubble growth or initiate embolism. Severely injured whales died or became stranded and died due to cardiovascular collapse during beaching. The present study demonstrates a new pathologic entity in cetaceans. The syndrome is apparently induced by exposure to mid-frequency sonar signals and particularly affects deep, long-duration, repetitive-diving species like BWs.

Hyperbaric computed tomographic measurement of lung compression in seals and dolphins

“…These findings require that we reopen the discussion as to whether marine mammals are susceptible to DCS. The data we present here add credence to findings and hypotheses on the subject of susceptibility to and manifestation of DCS in bycaught and stranded marine mammals (Fernandez et al, 2005;Jepson et al, 2005;Moore et al, 2009). The data add further weight to the suggestion that marine mammals may experience supersaturation at levels that may result in asymptomatic or symptomatic inert gas bubbles when diving repetitively, acquired when lung collapse is incomplete (Hooker et al, 2009).…”

“…These data established the pathobiological basis for a hypothesis (Cox et al, 2006) that beaked whales are acutely (Fernandez et al, 2005), and other odontocetes are perhaps chronically (Jepson et al, 2005;Moore and Early, 2004), at risk of DCS.…”

“…Gas bubbles in stranded aquatic mammals have become a focus of attention since a brief report (Jepson et al, 2003) and later papers on atypical mass strandings of beaked whales (Fernandez et al, 2005) and single strandings of odontocetes (Jepson et al, 2005). These data established the pathobiological basis for a hypothesis (Cox et al, 2006) that beaked whales are acutely (Fernandez et al, 2005), and other odontocetes are perhaps chronically (Jepson et al, 2005;Moore and Early, 2004), at risk of DCS.…”

“…bycaught animals) at 34-120m depth (Moore et al, 2009), and concluded that these cases are evidence of supersaturation during dives that are prolonged through entanglement. Thus, breath-holding marine mammals that are disturbed during diving may risk clinical symptoms of gas bubble formation, as observed in atypical mass strandings of beaked whales (Fernandez et al, 2005).…”

Acute kidney injury caused by decompression illness successfully treated with hyperbaric oxygen therapy and temporary dialysis

“…In an old animal experimental study, gas bubble emboli were observed in the renal artery and vein [20]. In another study, air emboli in the kidney veins were observed microscopically in a specimen taken from a stranded beaked whale that showed DCI-like lesions, similar to those in humans and laboratory animals [21]. In the current case, the exact cause of AKI could not be ascertained histologically because kidney biopsy was not performed due to the improvement of renal function soon after the diuretic phase.…”