Browsing by Author "Moline, Mark A."
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Item Climate-driven sympatry may not lead to foraging competition between congeneric top-predators(Nature Publishing Group, 2016-01-06) Cimino, Megan A.; Moline, Mark A.; Fraser, William R.; Patterson-Fraser, Donna L.; Oliver, Matthew J.; Megan A. Cimino, Mark A. Moline, William R. Fraser, Donna L. Patterson-Fraser & Matthew J. Oliver; Cimino, Megan A.; Moline, Mark A.; Oliver, Matthew J.Climate-driven sympatry may lead to competition for food resources between species. Rapid warming in the West Antarctic Peninsula (WAP) is coincident with increasing gentoo penguin and decreasing Adélie penguin populations, suggesting that competition for food may exacerbate the Adélie penguin decline. On fine scales, we tested for foraging competition between these species during the chickrearing period by comparing their foraging behaviors with the distribution of their prey, Antarctic krill. We detected krill aggregations within the horizontal and vertical foraging ranges of Adélie and gentoo penguins, and found that krill selected for habitats that balance the need to consume food and avoid predation. In overlapping Adélie and gentoo penguin foraging areas, four gentoo penguins switched foraging behavior by foraging at deeper depths, a strategy which limits competition with Adélie penguins. This suggests that climate-driven sympatry does not necessarily result in competitive exclusion of Adélie penguins by gentoo penguins. Contrary to a recent theory, which suggests that increased competition for krill is one of the major drivers of Adélie penguin population declines, we suggest that declines in Adélie penguins along the WAP are more likely due to direct and indirect climate impacts on their life histories.Item Comparisons of Underwater Light From Atmospheric and Mechanically Stimulated Bioluminescence Sources in High Arctic Polar Night(Journal of Geophysical Research: Oceans, 2024-04-29) Shulman, Igor; Cohen, Jonathan H.; Anderson, Stephanie; Penta, Bradley; Moline, Mark A.At high latitudes, polar night is a prolonged period of seasonal darkness with the sun remaining below the horizon throughout the diel cycle for up to 177 days at the North Pole. Along with diffuse atmospheric light from the sun and the moon, bioluminescence is an in-water light source that can facilitate ecological interactions in an otherwise dim-light environment. At high latitudes during polar night, bioluminescence rather than sunlight represents a significant portion of the photons available in the pelagic. We investigated depths of transition zones (called the bioluminescence transition depth) in the pelagic light field during polar night, defining the transition of a light field dominated by atmospheric irradiance, to one dominated by bioluminescent point sources. We derived relationships between values of the transition depth, bioluminescence potential, surface irradiance due to atmospheric light and the diffuse attenuation coefficient. We conducted studies for two Svalbard, Norway fjords, as well as for offshore areas located in the shelf-break, shelf-slope and in the Arctic basin. Based on our results for two polar nights, the transition from underwater light dominated by atmospheric sources to that dominated by bioluminescence occurs between 10 and 40 m in two Svalbard fjords, and between 18 and 60 m for offshore areas. These transition depths may be of particular importance to understanding how bioluminescence structures planktonic communities both in polar regions and at lower latitudes. Key Points - We investigated depths of transition zones from one dominated by atmospheric irradiance to one dominated by bioluminescent sources - We derived relationships between transition depth, bioluminescence potential, surface irradiance and diffuse attenuation coefficient - At high latitudes during polar night, bioluminescence represents a significant portion of the photons available in the pelagic Plain Language Summary The polar night is a period of continuous winter darkness north of ∼72.5°N latitude, and this period presents challenging light conditions for Arctic pelagic organisms. With the sun remaining below the horizon from one day at the Arctic Circle to 6 months at the North Pole, prolonged darkness limits light-mediated predator prey interactions in the plankton. Bioluminescence is light produced by a photochemical reaction in organisms, and it is an in-water light source that can facilitate ecological interactions in an otherwise dim-light environment. We investigated depths of transition zones from a light field dominated by atmospheric irradiance, to one dominated by bioluminescent point sources, across a gradient from Svalbard fjords to the Arctic basin. Based on our results, the transition from underwater light dominated by atmospheric sources to that dominated by bioluminescence occurs between 10 and 40 m in two Svalbard fjords, and between 18 and 60 m for offshore areas. The light gradient occurring in these transition zones has ecological implications, including depth selection and predator-prey interactions. This work provides another step in the difficult task of untangling the complex relationships among marine organisms and natural light.Item CTD and UBAT data from: Comparisons of underwater light from atmospheric and mechanically stimulated bioluminescence sources in high Arctic Polar Night(2024-01-22) Shulman, Igor; Cohen, Jonathan H.; Anderson, Stephanie; Penta, Bradley; Moline, Mark A.For each station, we profiled an instrumented cage from the surface to 120 m (bottom depth ≈ 200 m). The cage was equipped with a bathyphotometer (UBAT–Underwater Bioluminescence Assessment Tool, WetLabs, Philomath, OR) and CTD (SBE 49 FastCAT, Sea-Bird, Bellevue, WA). For each cast, we held instruments for 4 min at every 20 m depth interval to measure bioluminescence. Fjord sampling in January 2014 (A2014, B2014, C2014, D2014) was conducted in Kongsfjord, Svalbard (78° 56.16'N, 11° 56.58'E). For more detail on this data collection see: Cronin et al. (2016) Scientific Reports 6:36374, DOI: 10.1038/srep36374 Fjord sampling in January 2017 (A2017) was conducted in Rijpfjorden, Svalbard (80° 18.261'N / 02° 215.705'E). For more detail on this data collection see: Shulman et al. (2020) Ocean Dynamics 70:1211–1223, https://doi.org/10.1007/s10236-020-01392-2 Shelf/slope sampling in January 2017 (B2017, C2017) was conducted offshore from Rijpfjorden, Svalbard (80° 55.364'N / 017°32.469E, 80°35.923'N / 013°40.636'E). For more detail on this data collection see: Shulman et al. (2020) Ocean Dynamics 70:1211–1223, https://doi.org/10.1007/s10236-020-01392-2 Arctic basin sampling in January 2017 (D2017) was conducted further offshore of Rijpfjorden, Svalbard (81°21.285'N / 014°51.079'E). For more detail on this data collection see: Shulman et al. (2020) Ocean Dynamics 70:1211–1223, https://doi.org/10.1007/s10236-020-01392-2 The separate tabs in this spreadsheet correspond to each sampling location described above. CTD and UBAT data are included, with bioluminescence data provided as both 1 second averages and at 60Hz resolution Parameters and units for the profile at each station from merged CTD and UBAT records are: Time (ms) Record number (NA) Temp (C) Depth (m) Salinity (psu) Calibration Coeff for HV step (photons/s) Avg BL (photons/s) Pump RPM (RPM) System Voltage (V) Flow RPM (RPM) HV step (V) 60Hzdata_n [60 Hz digitized raw A/D counts, n=1-60] (photons)Item Is Ambient Light during the High Arctic Polar Night Sufficient to Act as a Visual Cue for Zooplankton?(PLOS (Public Library of Science), 2015-06-03) Cohen, Jonathan H.; Berge, Jørgen; Moline, Mark A.; Sørensen, Asgeir J.; Last, Kim; Falk-Petersen, Stig; Renaud, Paul E.; Leu, Eva S.; Grenvald, Julie; Cottier, Finlo; Cronin, Heather; Menze, Sebastian; Norgren, Petter; Varpe, Øystein; Daase, Malin; Darnis, Gerald; Johnsen, Geir; Jonathan H. Cohen, Jørgen Berge, Mark A. Moline, Asgeir J. Sørensen, Kim Last, Stig Falk-Petersen, Paul E. Renaud, Eva S. Leu, Julie Grenvald, Finlo Cottier, Heather Cronin, Sebastian Menze, Petter Norgren, Øystein Varpe, Malin Daase, Gerald Darnis, Geir Johnsen; Cohen, Jonathan H.; Moline, Mark A.; Cronin, HeatherThe light regime is an ecologically important factor in pelagic habitats, influencing a range of biological processes. However, the availability and importance of light to these processes in high Arctic zooplankton communities during periods of 'complete' darkness (polar night) are poorly studied. Here we characterized the ambient light regime throughout the diel cycle during the high Arctic polar night, and ask whether visual systems of Arctic zooplankton can detect the low levels of irradiance available at this time. To this end, light measurements with a purpose-built irradiance sensor and coupled all-sky digital photographs were used to characterize diel skylight irradiance patterns over 24 hours at 79°N in January 2014 and 2015. Subsequent skylight spectral irradiance and in-water optical property measurements were used to model the underwater light field as a function of depth, which was then weighted by the electrophysiologically determined visual spectral sensitivity of a dominant high Arctic zooplankter, Thysanoessa inermis. Irradiance in air ranged between 1–1.5 x 10-5 μmol photons m-2 s-1 (400–700 nm) in clear weather conditions at noon and with the moon below the horizon, hence values reflect only solar illumination. Radiative transfer modelling generated underwater light fields with peak transmission at blue-green wavelengths, with a 465 nm transmission maximum in shallow water shifting to 485 nm with depth. To the eye of a zooplankter, light from the surface to 75 m exhibits a maximum at 485 nm, with longer wavelengths (>600 nm) being of little visual significance. Our data are the first quantitative characterisation, including absolute intensities, spectral composition and photoperiod of biologically relevant solar ambient light in the high Arctic during the polar night, and indicate that some species of Arctic zooplankton are able to detect and utilize ambient light down to 20–30m depth during the Arctic polar night.