Modelling sound propagation in the Southern Ocean to estimate the acoustic impact of seismic research surveys on marine mammals

AbstractUnderstanding the regional and seasonal distribution of seismic research surveys in the Southern Ocean is essential for assessing their acoustic impact on the marine environment. An analysis of the navigation data and cruise table in the Seismic Data Library System for Cooperative Research (SDLS) shows that a fairly extensive network of seismic lines is now available for the Southern Ocean. However, line spacing ranges from tens to hundreds of kilometres, and some almost unsurveyed areas still exist. The seasonal distribution of the seismic profile lengths shows periods with increased survey activity between 1976/77 and 2001/02, but only moderate levels of activity between 2002/03 and 2010/11. The corresponding line spacing is large, and lines are widely distributed over the Southern Ocean. None of the eight Antarctic regions considered here have experienced seismic survey activity during all summer seasons in the last 35 years. Instead, periods with survey activity are interspersed by periods with no survey activity. The average survey length ranges from ∼2600 km per season off the Antarctic Peninsula to ∼260 km per season off Enderby Land. Compared to the industrial seismic exploration off Norway the acoustic impact of the seismic research activity in the Southern Ocean is at least ∼150 times lower.

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A Correction for the Thermal Mass–Induced Errors of CTD Tags Mounted on Marine Mammals

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-17-0141.1 ◽

2018 ◽

Vol 35 (6) ◽

pp. 1237-1252 ◽

Cited By ~ 8

Author(s):

Vigan Mensah ◽

Fabien Roquet ◽

Lia Siegelman-Charbit ◽

Baptiste Picard ◽

Etienne Pauthenet ◽

...

Keyword(s):

Temperature Gradient ◽

Southern Ocean ◽

Marine Mammals ◽

Thermal Mass ◽

Density Estimates ◽

Mass Error ◽

Correction Scheme ◽

Salinity Data ◽

Temperature Depth

AbstractThe effect of thermal mass on the salinity estimate from conductivity–temperature–depth (CTD) tags sensor mounted on marine mammals is documented, and a correction scheme is proposed to mitigate its impact. The algorithm developed here allows for a direct correction of the salinity data, rather than a correction of the sample’s conductivity and temperature. The amplitude of the thermal mass–induced error on salinity and its correction are evaluated via comparison between data from CTD tags and from Sea-Bird Scientific CTD used as a reference. Thermal mass error on salinity appears to be generally O(10−2) g kg−1, it may reach O(10−1) g kg−1, and it tends to increase together with the magnitude of the cumulated temperature gradient (THP) within the water column. The correction we propose yields an error decrease of up to ~60% if correction coefficients specific to a certain tag or environment are calculated, and up to 50% if a default value for the coefficients is provided. The correction with the default coefficients was also evaluated using over 22 000 in situ dive data from five tags deployed in the Southern Ocean and is found to yield significant and systematic improvements on the salinity data, including for profiles whose THP was weak and the error small. The correction proposed here yields substantial improvements in the density estimates, although a thermal mass–induced error in temperature measurements exists for very large THP and has yet to be corrected.

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Fishing down the food web of the Antarctic continental shelf and slope

Polar Record ◽

10.1017/s0032247412000757 ◽

2013 ◽

Vol 50 (1) ◽

pp. 92-107 ◽

Cited By ~ 34

Author(s):

David G. Ainley ◽

Daniel Pauly

Keyword(s):

Southern Ocean ◽

Food Web ◽

Antarctic Peninsula ◽

Continental Margin ◽

Marine Mammals ◽

Marine Ecosystem ◽

Euphausia Superba ◽

The Commons ◽

By Catch ◽

The Antarctic

ABSTRACTThe history of biotic exploitation for the continental margin (shelf and slope) of the Antarctic Large Marine Ecosystem (LME) is reviewed, with emphasis on the period from 1970 to 2010. In the Antarctic Peninsula portion, marine mammals were decimated by the 1970s and groundfish by the early 1980s. Fishing for Antarctic krill Euphausia superba began upon the demise of groundfish and now is the only fishing that remains in this region. Surveys show that cetacean and most groundfish stocks remain severely depressed, harvest of which is now prohibited by the International Whaling Commission and the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). On the other hand, krill fishing in this region is underway and in recent years has contributed up to 72% of the Southern Ocean catch, depending on fishing conditions and the CCAMLR conservation measures in force. Elsewhere along the Antarctic continental margin, marine mammals were also severely depleted by the 1970s, followed directly by relatively low-level fisheries for krill that continued until the early 1990s. Recently in these areas, where fin-fishing is still allowed, fisheries for Antarctic toothfish Dissostichus mawsoni have been initiated, with one of this fish's main prey, grenadiers Macrourus spp., being taken significantly as by-catch. Continental margin fishing currently accounts for ~25% of the total toothfish catch of the Southern Ocean. Fishing along the Antarctic continental margin, especially the Antarctic Peninsula region, is a clear case of both the tragedy of the commons and ‘fishing down the food web’.

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Seals and whales of the Southern Ocean

Philosophical Transactions of the Royal Society of London Series B Biological Sciences ◽

10.1098/rstb.1977.0073 ◽

1977 ◽

Vol 279 (963) ◽

pp. 81-96 ◽

Cited By ~ 177

Keyword(s):

Southern Ocean ◽

Marine Mammals ◽

Deep Ocean ◽

Euphausia Superba ◽

The Body ◽

The Arctic ◽

Individual Species ◽

Baleen Whales ◽

Fur Seals ◽

The Antarctic

There are fewer species of marine mammals in the Antarctic than in the Arctic, probably because of the wide deep ocean with no geographical barriers to promote speciation. The stocks are substantially larger in the Antarctic and the body sizes of individual species are larger, probably owing to a more abundant food supply. Seasonal changes in the environment in the Southern Ocean are marked and food available to baleen whales is very much greater in summer. Ecological interactions of the consumers, principally in relation to krill Euphausia superba , are discussed and attention drawn to some of the ways in which ecological separation is achieved, both within and between species. Estimates of abundances, biomasses and food requirements are given for the seals and large whales. The original numbers of whales in the Antarctic were far greater than in other oceans, but the stocks have been severely reduced by whaling. This may have increased the availability of krill to other consumers by as much as 150 million tonnes annually. Increased growth rates, earlier maturity and higher pregnancy rates have been demonstrated for baleen whale species, and earlier maturity for the crabeater seal. While it has not been possible to demonstrate increases in the populations of any of these species, the stocks of fur seals and penguins have been monitored and show significant population increases. A key question is whether the original balance of this ecosystem can be regained with appropriate management.

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A Modeling Comparison of the Potential Effects on Marine Mammals from Sounds Produced by Marine Vibroseis and Air Gun Seismic Sources

Journal of Marine Science and Engineering ◽

10.3390/jmse9010012 ◽

2020 ◽

Vol 9 (1) ◽

pp. 12

Author(s):

Marie-Noël R. Matthews ◽

Darren S. Ireland ◽

David G. Zeddies ◽

Robert H. Brune ◽

Cynthia D. Pyć

Keyword(s):

Marine Mammals ◽

Sound Propagation ◽

Animal Movement ◽

Evaluation Criteria ◽

Threshold Function ◽

Behavioral Disturbance ◽

Marine Fauna ◽

Sound Levels ◽

Air Gun ◽

Geophysical Surveys

Concerns about the potential environmental impacts of geophysical surveys using air gun sources, coupled with advances in geophysical surveying technology and data processing, are driving research and development of commercially viable alternative technologies such as marine vibroseis (MV). MV systems produce controllable acoustic signals through volume displacement of water using a vibrating plate or shell. MV sources generally produce lower acoustic pressure and reduced bandwidth (spectral content) compared to air gun sources, but to be effective sources for geophysical surveys they typically produce longer duration signals with short inter-signal periods. Few studies have evaluated the potential effects of MV system use on marine fauna. In this desktop study, potential acoustic exposure of marine mammals was estimated for MV and air gun arrays by modeling the source signal, sound propagation, and animal movement in representative survey scenarios. In the scenarios, few marine mammals could be expected to be exposed to potentially injurious sound levels for either source type, but fewer were predicted for MV arrays than air gun arrays. The estimated number of marine mammals exposed to sound levels associated with behavioral disturbance depended on the selection of evaluation criteria. More behavioral disturbance was predicted for MV arrays compared to air gun arrays using a single threshold sound pressure level (SPL), while the opposite result was found when using frequency-weighted sound fields and a multiple-step, probabilistic, threshold function.

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