Circulation in the vicinity of Mackenzie Canyon from a year-long mooring array

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Lin, P., Pickart, R. S., Fissel, D., Ross, E., Kasper, J., Bahr, F., Torres, D. J., O'Brien, J., Borg, K., Melling, H., & Wiese, F. K. Circulation in the vicinity of Mackenzie Canyon from a year-long mooring array. Progress in Oceanography, 187, (2020): 102396, doi:10.1016/j.pocean.2020.102396.Data from a five-mooring array extending from the inner shelf to the continental slope in the vicinity of Mackenzie Canyon, Beaufort Sea are analyzed to elucidate the components of the boundary current system and their variability. The array, part of the Marine Arctic Ecosystem Study (MARES), was deployed from October 2016 to September 2017. Four distinct currents were identified: an eastward-directed flow adjacent to the coast; a westward-flowing, surface-intensified current centered on the outer-shelf; a bottom-intensified shelfbreak jet flowing to the east; and a recirculation at the base of the continental slope within the canyon. The shelf current transports −0.120.03 Sv in the mean and is primarily wind-driven. The response is modulated by the presence of ice, with little-to-no signal during periods of nearly-immobile ice cover and maximum response when there is partial ice cover. The shelfbreak jet transports 0.030.02 Sv in the mean, compared to 0.080.02 Sv measured upstream in the Alaskan Beaufort Sea over the same time period. The loss of transport is consistent with a previous energetics analysis and the lack of Pacific-origin summer water downstream. The recirculation in the canyon appears to be the result of local dynamics whereby a portion of the westward-flowing southern limb of the Beaufort Gyre is diverted up the canyon across isobaths. This interpretation is supported by the fact that the low-frequency variability of the recirculation is correlated with the wind-stress curl in the Canada Basin, which drives the Beaufort gyre.The authors are indebted to Fisheries and Oceans Canada for building the logistics for MARES into the at-sea missions of the Integrated Beaufort Observatory. We are grateful to the captain and crew of the CCGS Sir Wilfred Laurier for ably deploying and recovering the MARES array. Marshall Swartz assisted with the cruise preparation logistics. We thank the two anonymous reviewers for their input which helped improve the paper. This project was funded by the US Bureau of Ocean Energy Management (BOEM), on behalf of the National Ocean Partnership Program. The Canadian contribution was supported by the Environmental Studies Research Fund (ESRF Project 2014-02N). MARES publication 003

Localization and Characterization of STRO-1+ Cells in the Deer Pedicle and Regenerating Antler

The annual regeneration of deer antlers is a unique developmental event in mammals, which as a rule possess only a very limited capacity to regenerate lost appendages. Studying antler regeneration can therefore provide a deeper insight into the mechanisms that prevent limb regeneration in humans and other mammals, and, with regard to medical treatments, may possibly even show ways how to overcome these limitations. Traditionally, antler regeneration has been characterized as a process involving the formation of a blastema from de-differentiated cells. More recently it has, however, been hypothesized that antler regeneration is a stem cell-based process. Thus far, direct evidence for the presence of stem cells in primary or regenerating antlers was lacking. Here we demonstrate the presence of cells positive for the mesenchymal stem cell marker STRO-1 in the chondrogenic growth zone and the perivascular tissue of the cartilaginous zone in primary and regenerating antlers as well as in the pedicle of fallow deer (Dama dama). In addition, cells positive for the stem cell/progenitor cell markers STRO-1, CD133 and CD271 (LNGFR) were isolated from the growth zones of regenerating fallow deer antlers as well as the pedicle periosteum and cultivated for extended periods of time. We found evidence that STRO-1+ cells isolated from the different locations are able to differentiate in vitro along the osteogenic and adipogenic lineages. Our results support the view that the annual process of antler regeneration might depend on the periodic activation of mesenchymal progenitor cells located in the pedicle periosteum. The findings of the present study indicate that not only limited tissue regeneration, but also extensive appendage regeneration in a postnatal mammal can occur as a stem cell-based process

Sinking rates of dead birds: Improving estimates of seabird mortality due to oiling

Seabird mortality resulting from oil spills is generally assessed based on the number of birds lost at sea. Drift blocks we often employed to determine the loss at sea and because blocks do not sink, but seabird carcasses do, it is essential to determine accurate sinking rates of seabird carcasses to correctly interpret onshore drift block recoveries. To quantify sinking rates of seabird carcasses, to determine possible differences between oiled and unoiled birds, and to investigate the importance of scavenging, I conducted an experiment in St. John's, Newfoundland, Canada, with 54 intact, but previously frozen murres (Uria spp.), the most common victims in oil spills in the Northern Hemisphere. Birds were randomly assigned to clean, lightly oiled (25% of body oiled) or heavily oiled (50% body oiled) categories. Twelve birds of each oiling category were placed into a floating three-chambered wooden-framed pen. The remaining birds were placed in a mesh-screened pen on the wharf. After nine days, randomly assigned carcasses from the floating pen and all birds on land, were opened to simulate partial scavenging. After 19 days, all flesh and muscles were removed from remaining birds to simulate complete scavenging. Changes in the buoyancy of carcasses were determined daily by measuring the amount of added mass (in 5 g increments) necessary to sink them (Burger 1991, cited in Burger and Fry 1993). On average, carcasses remained afloat 8.2 ± 1.0 d (95% C.I. 6.2 - 10.3), with no difference between oiled and unoiled, either floating or on land. Carcasses on land retained buoyancy significantly longer and only 1 carcass sank with the 24 d period. Buoyancy loss was best described by a logistic time-dependent function. When carcasses were scavenged, buoyancy loss increased exponentially. Based on these results, it appears that backwash and subsequent sinking of stranded carcasses is likely not a significant mechanism of carcasses removal from beaches. I recommend using a 10-14 d estimate for the length of time that murres and other auks remain afloat at sea, and to use a time-dependent logistic function to estimate the proportion of birds lost at sea. It appears that most estimates of seabird mortality due to spilled oil based on drift block experiments may be too low because onshore block recoveries relevant to seabird carcasses have been over-estimated

Estimation and impacts of seabird mortality from chronic marine oil pollution off the coast of Newfoundland

The Grand Banks south off Newfoundland provide year-round feeding habitat for tens of millions of seabirds of numerous species, an abundance and diversity unparalleled in the North Atlantic. Dense ship traffic routes traverse this productive environment as vessels travel the Great Circle Route between Europe and North America. Oiled seabirds have washed up on beaches in Newfoundland for many decades. Most oil on their feathers has been identified as heavy fuel oil mixed with lubricants, the mixture found in the bilges of large vessels. Beached bird surveys conducted between 1984-1999 indicate that the incidence of chronic oil pollution along the southeast coast of Newfoundland is among the highest in world. More than 60% of all dead birds found over the 16-year period had oil on their feathers; 74% during the last five years. Auks, especially Thick-billed Murres (Uria lomvia), are the most affected. -- In an effort to estimate overall mortality of seabirds in winter due to chronic oil pollution in Atlantic Canada, I performed a series of experiments to determine the fate of oiled and unoiled birds at sea and on beaches. First, I determined that carcasses persisted on average for only 3.3 ± 0.1 days on beaches in southeastern Newfoundland, after which they were no longer detectable due to scavenging or burial in the beach substrate. In addition, no differences were found in persistence rates between oiled and unoiled birds. I also determined deposition rates and detection probabilities of bird carcasses on beaches, and developed a model to estimate the number of birds arriving on a beach between periodic surveys. This model only performs well if survey intervals are less than 10 days. Second, I designed a drift block that accurately mimics the movements of a seabird carcass drifting at sea. As drift blocks used in past studies showed little resemblance to actual carcass drift because they were overly influenced by wind, a more realistic drift block was needed to accurately interpret the number of birds that are found dead on beaches. Third, I measured murre carcass sinking rates and found that birds only float 8.2 ± 5.2 days before sinking, but that scavenging is important. Fourth, I carried out extensive drift block experiments using the new block design to determine the proportion of birds that die at sea and reach the shore, taking into account sinking rates of floating carcasses at sea. Recovery rates of blocks dropped at different locations varied, and the best predictor for the proportion of blocks lost at sea was the distance from shore where they were dropped, combined with the cumulative wind direction vector during the first three days following drift block drops. Based on wind patterns observed during the experiment, I was able to estimate wind specific recovery rates and catchment areas for birds that die at sea. Fifth, I constructed a general mathematical Oiled Seabird Mortality Model to assess seabird mortality due to chronic oil pollution along a given coastline. -- I applied the Oiled Seabird Mortality Model to southeastern Newfoundland, based on periodic beached bird surveys conducted during the winters 1998/1999 through 2000/2001 and the parameters I determined earlier. Several assumptions were made to extrapolate seabird mortality due to oil to a large area at sea, and my most robust estimate is that on average, 315,000 ± 65,000 seabirds were killed annually in southeastern Newfoundland due to illegal discharges of oil from ships. Thick-billed Murres that over- winter on the Grand Banks made up 67 % of this kill. I examined the effects of this anthropogenic mortality, in combination with the estimated number of murres killed during the traditional murre hunt in Newfoundland, on Thick-billed Murre populations that breed in the eastern Canadian Arctic, by building a stochastic (demographic and environmental), age-structured, density independent, pre-breeding, Lefkovitch population projection matrix. The model suggested that chronic oil pollution has reduced potential annual population growth by 2.5 %. In combination with a further 2 % reduction in annual growth caused by hunting, these sustained anthropogenic causes of mortality have made Thick-billed Murre populations particularly vulnerable to environmental changes (e.g. global warming, ocean regime shifts). A series of actions are outlined to help reduce chronic oil pollution in Atlantic Canada, including increased year-round enforcement, imposition of minimum fines and higher imposed fines, the establishment of convenient oil disposal facilities on land, and increased education and awareness programs

Appendix A. A table showing mass of bird carcasses collected in Chelan County, Washington, USA, during the summers of 2002–2004.

A table showing mass of bird carcasses collected in Chelan County, Washington, USA, during the summers of 2002–2004

Appendix B. A table showing mean mass and caloric density of prey species found in stomachs of birds shot at Rock Island Dam, Washington, USA, during the summers of 2002–2004.

A table showing mean mass and caloric density of prey species found in stomachs of birds shot at Rock Island Dam, Washington, USA, during the summers of 2002–2004