Browsing by Author "Cohen, Jonathan H."
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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 Effects of a bacteria-produced algicide on non-target marine invertebrate species(Scientific Reports, 2021-01-12) Simons,Victoria E.; Coyne, Kathryn J.; Warner, Mark E.; Dolan, Margaret M.; Cohen, Jonathan H.Harmful algal blooms (HABs) affect both freshwater and marine systems. Laboratory experiments suggest an exudate produced by the bacterium Shewanella sp. IRI-160 could be used to prevent or mitigate dinoflagellate blooms; however, effects on non-target organisms are unknown. The algicide (IRI-160AA) was tested on various ontogenetic stages of the copepod Acartia tonsa (nauplii and adult copepodites), the blue crab Callinectes sapidus (zoea larvae and megalopa postlarvae), and the eastern oyster Crassostrea virginica (pediveliger larvae and adults). Mortality experiments with A. tonsa revealed that the 24-h LC50 was 13.4% v/v algicide for adult females and 5.96% for early-stage nauplii. For C. sapidus, the 24-h LC50 for first-stage zoeae was 16.8%; results were not significant for megalopae or oysters. Respiration rates for copepod nauplii increased in the 11% concentration, and in the 11% and 17% concentrations for crab zoeae; rates of later stages and oysters were unaffected. Activity level was affected for crab zoeae in the 1%, 11%, and 17% treatments, and for oyster pediveliger larvae at the 17% level. Activity of later stages and of adult copepods was unaffected. Smaller, non-target biota with higher surface to volume could be negatively impacted from IRI-160AA dosing, but overall the taxa and stages assayed were tolerant to the algicide at concentrations required for dinoflagellate mortality (EC50 = ~ 1%).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.Item Photoperiodism and overwintering in boreal and sub-Arctic Calanus finmarchicus populations(Marine Ecology Progress Series, 2023-06-08) Coguiec, Estelle; Last, Kim S.; Cohen, Jonathan H.; Hobbs, Laura; Choquet, Marvin; Ershova, Elizaveta; Berge, Jørgen; Daase, MalinThe copepod Calanus finmarchicus, a key species in the North Atlantic, generally spends the non-productive season by descending into deep waters and entering diapause, a physiological state characterized by reduced metabolism and arrested development. In the open ocean, overwintering depths are below 600 m, where temperature and light conditions are favourable to initiate diapause. However, C. finmarchicus has also been reported diapausing in areas with shallow water depth such as fjords, coastal waters and shelf seas. In these environments, the temperature and light conditions are different, and it has been hypothesized that under such conditions C. finmarchicus may remain active throughout winter. Here, we investigated changes in the swimming activity of C. finmarchicus from shallow fjords in the eastern North Atlantic during overwintering in response to ambient photoperiod. We conducted monthly experiments with populations from 2 fjords from different latitudes (sub-Arctic Ramfjord, 69°N and boreal Loch Etive, 56°N), measuring the locomotor activity of individual C. finmarchicus stage CVs exposed to a natural light:dark cycle. At both locations, peaks in activity in response to the light cycle were observed to shift from nocturnal during the early overwintering phase to diurnal during mid and late overwintering phase, with a minimal intensity observed during the mid-overwintering phase. In Ramfjord, activity and rhythmicity were generally lower than in Loch Etive. We conclude that C. finmarchicus remains active throughout its overwintering period when in shallow (<200 m) locations but down-regulates its locomotor activity during the main overwintering phase, which we describe as a winter resting state as distinct from classical diapause.Item Photophysiological cycles in Arctic krill are entrained by weak midday twilight during the Polar Night(PLOS Biology, 2021-10-19) Cohen, Jonathan H.; Last, Kim S.; Charpentier, Corie L.; Cottier, Finlo; Daase, Malin; Hobbs, Laura; Johnsen, Geir; Berge, JørgenLight plays a fundamental role in the ecology of organisms in nearly all habitats on Earth and is central for processes such as vision and the entrainment of the circadian clock. The poles represent extreme light regimes with an annual light cycle including periods of Midnight Sun and Polar Night. The Arctic Ocean extends to the North Pole, and marine light extremes reach their maximum extent in this habitat. During the Polar Night, traditional definitions of day and night and seasonal photoperiod become irrelevant since there are only “twilight” periods defined by the sun’s elevation below the horizon at midday; we term this “midday twilight.” Here, we characterize light across a latitudinal gradient (76.5° N to 81° N) during Polar Night in January. Our light measurements demonstrate that the classical solar diel light cycle dominant at lower latitudes is modulated during Arctic Polar Night by lunar and auroral components. We therefore question whether this particular ambient light environment is relevant to behavioral and visual processes. We reveal from acoustic field observations that the zooplankton community is undergoing diel vertical migration (DVM) behavior. Furthermore, using electroretinogram (ERG) recording under constant darkness, we show that the main migratory species, Arctic krill (Thysanoessa inermis) show endogenous increases in visual sensitivity during the subjective night. This change in sensitivity is comparable to that under exogenous dim light acclimations, although differences in speed of vision suggest separate mechanisms. We conclude that the extremely weak midday twilight experienced by krill at high latitudes during the darkest parts of the year has physiological and ecological relevance.Item Physiological and behavioral evidence for multiple spectral channels in the larval stomatopod visual system(Journal of Experimental Biology, 2023-05-17) McDonald, Marisa S.; Cohen, Jonathan H.; Porter, Megan L.Larval stomatopods have generally been described as having a typical larval crustacean compound eye, which lacks the visual pigment diversity and morphological specializations of the well-studied stomatopod adult eye. However, recent work has suggested that larval stomatopod eyes are more complex than previously described. In this study, we provide physiological and behavioral evidence of at least three distinct photoreceptor classes in three species of larval stomatopods: Gonodactylellus n. sp., Gonodactylaceus falcatus and Pullosquilla n. sp. First, electroretinogram recordings were used to measure the spectral sensitivity of each species. Evidence for at least three spectral classes were identified in each: an ultraviolet, peaking at 340–376 nm; a short-wavelength blue, peaking at 455–464 nm; and a long-wavelength orange, peaking at 576–602 nm. Next, the behavioral response to light was investigated. We found that each species demonstrated positive phototactic responses to monochromatic stimuli across the UV–visible spectrum. In wavelength preference trials, distinct preferences among species were identified when different colored light stimuli were presented simultaneously. All species displayed a strong response to the UV stimulus, as well as responses to blue and orange stimuli, although at different response strengths, but no response to green. The results of this study demonstrate that larval stomatopods not only have multiple physiologically active spectral classes but they also display clear and distinct responses to wavelengths across the spectrum. We propose that the spectral classes demonstrated in each are related to visually guided ecological tasks of the larvae, which may differ between species.Item Zooplankton-microplastic exposure in Delaware coastal waters: Atlantic blue crab (Callinectes sapidus) larvae case study(Marine Pollution Bulletin, 2023-10-05) Thoman, Todd X.; Kukulka, Tobias; Cohen, Jonathan H.; Boettcher, HaydenHigh microplastic concentrations in the Delaware Bay have prompted concern regarding harm to local species. We consider the extent to which the zooplankton is exposed to bay-derived microplastics, focusing on Atlantic blue crabs (Callinectes sapidus) during offshore larval migration. We simulate regional flow fields for a spawning season in the Delaware coastal system to advect passive Lagrangian microplastic and zooplankton tracers. Microplastic exposure levels are estimated from tracer distributions. Field sampling of zooplankton and microplastic concentrations for the Delaware Bay mouth and the adjacent shelf in August 2020 is utilized to appraise model performance. Three mechanisms elevating microplastics exposure are identified: zooplankton transport into microplastic-laden tidelines, displacement of microplastics into the buoyant outflow current, and aggregation in offshore plume fronts. Organization via the above mechanisms substantially enhance microplastic exposures over zooplankton migrations (by an average factor of at least 3.8). Highlights • Microplastic distribution is tied to surface winds and the offshore river plume front. • Tidelines, river outflow, and fronts amplify zooplankton exposure to microplastics. • Offshore plume fronts drive weaker exposure than less common transport pathways. • Mean microplastic exposures are comparable to source microplastic concentrations.