We are pleased to announce the publication of a
short review that summarizes our current ideas how sonar may
interfere with diving in cetaceans.
This article is an open access publication,
which means that it is freely accessible to any reader anywhere in
the world. We encourage you to share the article link with any
colleagues who may be interested in this work.
Title:
How man-made interference might cause gas
bubble emboli in deep diving whales
Authors:
Andreas Fahlman, Peter L Tyack, Patrick
James Miller, and Petter H Kvadsheim
Journal:
Frontiers
in Physiology
URL: http://www.frontiersin.org/Journal/Abstract.aspx?f=65&name=physiology&ART_DOI=10.3389/fphys.2014.00013&utm_source=Email_to_authors_&utm_medium=Email&utm_content=T1_11.5e1_author&utm_campaign=Email_publication&journalName=Frontiers_in_Physiology&id=66907
Recent cetacean
mass strandings in close temporal and spatial association with
sonar activity
has raised the concern that anthropogenic sound may harm
breath-hold diving
marine mammals. Necropsy results of the stranded whales have
shown evidence of bubbles
in the tissues, similar to those in human divers suffering from
decompression
sickness (DCS). It has been proposed that changes in behavior or
physiological
responses during diving could increase tissue and blood N2
levels,
thereby increasing DCS risk. Dive
data
recorded from sperm, killer, long-finned pilot, Blainville’s
beaked and
Cuvier’s beaked whales before and during exposure to low- (1-2
kHz) and mid-
(2-7 kHz) frequency active sonar were used to estimate the
changes in blood and
tissue N2 tension (PN2). Our
objectives were to determine if
differences in 1) dive behavior or 2) physiological responses to
sonar are
plausible risk factors for bubble formation. The theoretical
estimates indicate
that all species may experience high N2
levels. However, unexpectedly, deep diving generally result in
higher end-dive PN2
as compared
with shallow diving. In this focused review we focus on three
possible explanations:
1) We revisit an old hypothesis that CO2, because of
its much higher
diffusivity, forms bubble precursors that continue to grow in N2
supersaturated
tissues. Such a mechanism would be less dependent on the
alveolar collapse
depth but affected by elevated levels of CO2
following a burst of
activity during sonar exposure. 2) During deep
dives, a greater
duration of time might be spent at depths where gas exchange
continues as
compared with shallow dives. The resulting elevated levels of N2
in
deep diving whales might also make them more susceptible to
anthropogenic
disturbances. 3) Extended duration of dives even at depths
beyond where the
alveoli collapse could result in slow continuous accumulation of
N2
in the adipose tissues that eventually becomes a liability.
-- Andreas Fahlman Department of Life Sciences Texas A&M- Corpus Christi 6300 Ocean Dr Unit 5892 Corpus Christi, TX 78412 Ph. +1-361-825-3489 Fax +1-361-825-2025 mail: andreas.fahlman@tamucc.edu web: http://www.comparative-physiology.tamucc.edu/