Top predators in relation to bathymetry, ice and krill during austral winter in Marguerite Bay, Antarctica

Author Posting. © Elsevier B.V., 2007. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 55 (2008): 485-499, doi:10.1016/j.dsr2.2007.11.006.A key hypothesis guiding the U.S. Southern Ocean Global Ocean Ecosystems Dynamics (U.S. SO GLOBEC) program is that deep across-shelf troughs facilitate the transport of warm and nutrient-rich waters onto the continental shelf of the Western Antarctic Peninsula, resulting in enhanced winter production and prey availability to top predators. We tested aspects of this hypothesis during austral winter by assessing the distribution of the resident pack-ice top predators in relation to these deep across-shelf troughs and by investigating associations between top predators and their prey. Surveys were conducted July-August 2001 and August-September 2002 in Marguerite Bay, Antarctica, with a focus on the main across-shelf trough in the bay, Marguerite Trough. The common pack-ice seabird species were snow petrel (Pagodroma nivea, 1.2 individuals km-2), Antarctic petrel (Thalassoica antarctica, 0.3 individuals km-2), and Adélie penguin (Pygoscelis adeliae, 0.5 individuals km-2). The most common pack-ice pinniped was crabeater seal (Lobodon carcinophagus). During both winters, snow and Antarctic petrels were associated with low sea ice concentrations independent of Marguerite Trough, while Adélie penguins occurred in association with this trough. Krill concentrations, both shallow and deep, were also associated with Adélie penguin and snow petrel distributions. During both winters, crabeater seal occurrence was associated with deep krill concentrations and with regions of lower chlorophyll concentration. The area of lower chlorophyll concentrations occurred in an area with complex bathymetry close to land and heavy ice concentrations. Complex or unusual bathymetry via its influence on physical and biological processes appears to be one of the keys to understanding how top predators survive during the winter in this Antarctic region.This material is based upon work supported by the National Science Foundation under Grants No. OPP-9910096 (to C. Ribic), OPP-9910307 (to P. Wiebe), OPP-9632763, OPP-0120525, OPP-0217282 and OPP-0224727 (to W. Fraser), and a Fulbright Scholarship and Office of Naval Research Grant N00014-03-0212 (to G. Lawson)

Avian olfactory receptor gene repertoires: evidence for a well-developed sense of smell in birds?

Among vertebrates, the sense of smell is mediated by olfactory receptors (ORs) expressed in sensory neurons within the olfactory epithelium. Comparative genomic studies suggest that the olfactory acuity of mammalian species correlates positively with both the total number and the proportion of functional OR genes encoded in their genomes. In contrast to mammals, avian olfaction is poorly understood, with birds widely regarded as relying primarily on visual and auditory inputs. Here, we show that in nine bird species from seven orders (blue tit, Cyanistes caeruleus; black coucal, Centropus grillii; brown kiwi, Apteryx australis; canary, Serinus canaria; galah, Eolophus roseicapillus; red jungle fowl, Gallus gallus; kakapo, Strigops habroptilus; mallard, Anas platyrhynchos; snow petrel, Pagodroma nivea), the majority of amplified OR sequences are predicted to be from potentially functional genes. This finding is somewhat surprising as one previous report suggested that the majority of OR genes in an avian (red jungle fowl) genomic sequence are non-functional pseudogenes. We also show that it is not the estimated proportion of potentially functional OR genes, but rather the estimated total number of OR genes that correlates positively with relative olfactory bulb size, an anatomical correlate of olfactory capability. We further demonstrate that all the nine bird genomes examined encode OR genes belonging to a large gene clade, termed γ-c, the expansion of which appears to be a shared characteristic of class Aves. In summary, our findings suggest that olfaction in birds may be a more important sense than generally believed

Decadal Trends in Abundance, Size and Condition of Antarctic Toothfish in McMurdo Sound, Antarctica, 1972-2010

We report analyses of a dataset spanning 38 years of near-annual fishing for Antarctic toothfish Dissostichus mawsoni, using a vertical setline through the fast ice of McMurdo Sound, Antarctica, 1972-2010. This constitutes one of the longest biological time series in the Southern Ocean, and certainly the longest for any fish. Fish total length, condition and catch per unit effort (CPUE) were derived from the more than 5500 fish caught. Contrary to expectation, length-frequency was dominated by fish in the upper half of the industrial catch. The discrepancy may be due to biases in the sampling capabilities of vertical (this study) versus benthic (horizontal) fishing gear (industry long lines), related to the fact that only large Antarctic toothfish (more than 100 cm TL) are neutrally buoyant and occur in the water column. Fish length and condition increased from the early 1970s to the early 1990s and then decreased, related to sea ice cover, with lags of 8 months to 5 years, and may ultimately be related to the fishery (which targets large fish) and changes in the Southern Annular Mode through effects on toothfish main prey, Antarctic silverfish Pleuragramma antarcticum. CPUE was constant through 2001 and then decreased dramatically, likely related to the industrial fishery, which began in 1996 and which concentrates effort over the Ross Sea slope, where tagged McMurdo fish have been found. Due to limited prey choices and, therefore, close coupling among mesopredators of the Ross Sea, Antarctic toothfish included, the fishery may be altering the trophic structure of the Ross Sea

Sea ice parameters near McMurdo Station, Antarctica from 1986 to 2013

Dataset: McMurdo Sound sea ice thicknessFast ice thickness and temperature data collected at the “sea ice runway” near McMurdo Station by the United States Antarctic Program (USAP) logistic support contractors and provided by the Ice Surveyor (J Scanniello). Fast ice measurements were taken at a suite of 16 stations along a 3000 m distance, and five stations across an orthogonal 1000 m distance. At each station, small holes were drilled through the fast ice and the thickness measured using a meter tape with a lever-arm that held the zero-point against the bottom of the fast ice. Thickness was measured for solid ice and did not include underlying platelet ice, nor overlying snow. Fast ice temperature was measured at 15 cm depth beneath the ice surface. Note that the sea ice runway area is routinely cleared of excess snow, which may affect the fast ice thickness and temperature measurements. For a complete list of measurements, refer to the supplemental document 'Field_names.pdf', and a full dataset description is included in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: http://www.bco-dmo.org/dataset/675187NSF Division of Polar Programs (NSF PLR) PLR-0944747, NSF Division of Polar Programs (NSF PLR) PLR-0944511, NSF Division of Polar Programs (NSF PLR) PLR-094469

Chlorophyll data from McMurdo Sound, Antarctica from 2012 to 2015 (McMurdo Predator Prey project)

Dataset: McMurdo Sound chlorophyllDiscrete chlorophyll a data were collected as part of an ecosystem study in McMurdo Sound, which is located at the southern extent of the Ross Sea in the Southern Ocean. The major goal of this multi-disciplinary project was to assess the influence of top−down forcing (predation) on pelagic zooplankton and fish. Samples were collected using Niskin water bottles deployed through the fast ice (sea ice attached to land) during two spring/summer seasons: 3 November 2012 – 21 January 2013 and17 November 2014 – 1 January 2015. Water samples were collected at the surface and in the chlorophyll maximum, when present, as determined by a fluorescence sensor during a CTD cast. During 2012/2013, stations were located along a transect in the middle of McMurdo Sound, perpendicular to the fast ice edge. During 2014/2015, stations were located along the fast ice edge, and along three transects into the fast ice along the eastern side of the McMurdo Sound (Ross Island), in the middle of the Sound, and on the western side of the Sound. For a complete list of measurements, refer to the supplemental document 'Field_names.pdf', and a full dataset description is included in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: http://www.bco-dmo.org/dataset/679685NSF Division of Polar Programs (NSF PLR) PLR-094451

CTD data from McMurdo Sound, Antarctica from 2012 to 2015 (McMurdo Predator Prey project)

Dataset: McMurdo Sound CTDsCTD data were collected as part of an ecosystem study in McMurdo Sound, which is located at the southern extent of the Ross Sea in the Southern Ocean. The major goal of this multi-disciplinary project was to assess the influence of top−down forcing (predation) on pelagic zooplankton and fish. During the first year (3 November 2012 – 21 January 2013), the CTD was deployed through ice core holes in the fast ice (sea ice attached to land), sampling from near surface to depths between 97 and 175 m. Stations were located along a transect in the middle of McMurdo Sound, perpendicular to the fast ice edge. In the second year (17 November 2014 – 1 January 2015), CTD casts were deployed between 100 and 254 m in depth, at stations along the fast ice edge, and along three transects into the fast ice along the eastern side of McMurdo Sound (Ross Island), in the middle of the Sound, and on the western side of the Sound. Chlorophyll fluorescence sensor measurements on the CTD casts were only made during the 2014/2015 field expedition. For a complete list of measurements, refer to the supplemental document 'Field_names.pdf', and a full dataset description is included in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: http://www.bco-dmo.org/dataset/680929NSF Division of Polar Programs (NSF PLR) PLR-094451

Dates of sea ice movement and sea ice distance in McMurdo Sound, Antarctica from MODIS and SSMI imagery between 1978-2015 (McMurdo Predator Prey project)

Dataset: McMurdo Sound sea ice movement datesFast/sea ice movement was quantified from visible-wavelength images from the Moderate-resolution Imaging Spectroradiometer (MODIS) aboard the Aqua and Terra satellites (250 m resolution; processing occurred for 2002/03-2014/15 seasons and Terra satellite date from 2000-2002 were not used) and sea ice concentration derived from the Scanning Multichannel Microwave Radiometer- and Special Sensor Microwave Imager-family passive microwave sensors (SSM/I; 25 km resolution; 1978/79-2014/15). MODIS data were acquired in one of two ways, from either processing of Level 1 swath data into “true color” images using SeaDAS software v. 6.4 (2002-2012), or from the Corrected Reflectance (True Color) layers of the NASA Worldview website (http://worldview.earthdata.nasa.gov/; 2012-2015). Fast ice areas were generated manually from clear-sky images by drawing polygons in GIS software; pack ice was excluded from analysis. The fast ice in MODIS images was sometimes obscured by clouds, so for days with missing imagery we interpolated linearly between valid data. From the MODIS imagery, we also measured the direct linear distance between McMurdo Station and the nearest open water. For SSM/I, daily or bi-daily fractional sea ice cover was extracted from data available at the National Snow and Ice Data Center (NSIDC). SSM/I ice concentration was retrieved from the NSDIC web site and ftp site (http://nsidc.org/data/seaice/). To minimize the biases inherent to the different data processing algorithms and in order to reduce the daily variability introduced by the movement of pack ice, we took the maximum of either the Bootstrap or NASATEAM processed values (Comiso, 2000; Cavalieri and others, 2015), and then used a 5-day median filter to smooth changes in sea ice concentration. To further compensate for short-term oscillations we masked ice concentrations greater than 80% when extracting the dates of changes in sea ice cover. For detecting the timing of sea ice changes, sea ice concentrations below 15% were excluded from our analysis, following the methods of Comiso and Steffen (2001).> To simplify discussion in the following, we use the inclusive term “fast/sea ice” to refer to fast ice as determined by MODIS and sea ice as determined by SSM/I. Fast/sea ice area was plotted over time, and the following sequential pattern of fast/sea ice events is identified: (1) initial fast/sea ice retreat from winter maximum; (2) final rapid fast/sea ice retreat to minimum extent; (3) fast/sea ice cover minimum in the entire McMurdo Sound; and (4) fast/sea ice advance. From the MODIS data, we additionally determined (5) fast ice cover minimum on the west side of the Sound; and (6) fast ice cover minimum on the east side of the Sound. For a complete list of measurements, refer to the supplemental document 'Field_names.pdf', and a full dataset description is included in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: http://www.bco-dmo.org/dataset/674819NSF Division of Polar Programs (NSF PLR) PLR-0944747, NSF Division of Polar Programs (NSF PLR) PLR-0944511, NSF Division of Polar Programs (NSF PLR) PLR-094469

Icebreaker dates and ice edge distance in McMurdo Sound, Antarctica from austral years 1956/1957 to 2014/2015 (McMurdo Predator Prey project)

Dataset: McMurdo Sound icebreaker dates and ice edge distanceThe icebreaker channel from the fast ice edge to McMurdo Station has been created each year since 1956, with the location of the channel remaining consistent, by and large, over the entire period. Dates of the icebreaker arrival at the fast ice edge and/or at McMurdo Station since 1957 were acquired from scientist and icebreaker logbooks and contractor records (DACSUSAP2012-13; pers. comm. P. McGillivary USCG), along with the distance, which was measured by radar from the fast ice edge to McMurdo Station on the date that the icebreaker began breaking fast ice. For a complete list of measurements, refer to the supplemental document 'Field_names.pdf', and a full dataset description is included in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: http://www.bco-dmo.org/dataset/674992NSF Division of Polar Programs (NSF PLR) PLR-0944747, NSF Division of Polar Programs (NSF PLR) PLR-0944511, NSF Division of Polar Programs (NSF PLR) PLR-094469