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  • 1
    Publication Date: 2017-01-22
    Description: Fecal pellets (FP) are a key component of the biological carbon pump, as they can, under some circumstances, efficiently transfer carbon to depth. Like other forms of particulate organic carbon (POC), they can be remineralized in the ocean interior (particularly in the upper 200 m), or alternatively they can be preserved in the sediments. The controls on the attenuation of FP flux with depth are not fully understood, in particular, the relative contributions of zooplankton fragmentation and microbial/zooplankton respiration to FP loss. Collection of sinking particles using Marine Snow Catchers at three ecologically contrasting sites in the Scotia Sea, Antarctica, revealed large differences in POC flux composition (5–96% FP) and flux attenuation despite similar temperatures. To determine the importance of microbial respiration on FP loss in the upper mesopelagic, we made the first ever measurements of small scale oxygen gradients through the boundary layer at the interface of krill FP collected from the Scotia Sea. Estimated carbon-specific respiration rates of microbes within FP (0.010–0.065 d−1) were too low to account for the observed large decreases in FP flux over the upper 200 m. Therefore, the observed rapid declines in downward FP flux in the upper mesopelagic are more likely to be caused by zooplankton, through coprophagy, coprorhexy, and coprochaly. Microbial respiration is likely to be more important in regions of higher temperatures, and at times of the year, or in depths of the ocean, where zooplankton abundances are low and therefore grazing and fragmentation processes are reduced.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 2
    Publication Date: 2017-05-04
    Description: The impact of anthropogenic ocean acidification (OA) on marine ecosystems is a vital concern facing marine scientists and managers of ocean resources. Euthecosomatous pteropods (holoplanktonic gastropods) represent an excellent sentinel for indicating exposure to anthropogenic OA because of the sensitivity of their aragonite shells to the OA conditions less favorable for calcification. However, an integration of observations, experiments and modelling efforts is needed to make accurate predictions of how these organisms will respond to future changes to their environment. Our understanding of the underlying organismal biology and life history is far from complete and must be improved if we are to comprehend fully the responses of these organisms to the multitude of stressors in their environment beyond OA. This review considers the present state of research and understanding of euthecosomatous pteropod biology and ecology of these organisms and considers promising new laboratory methods, advances in instrumentation (such as molecular, trace elements, stable isotopes, palaeobiology alongside autonomous sampling platforms, CT scanning and high-quality video recording) and novel field-based approaches (i.e. studies of upwelling and CO2 vent regions) that may allow us to improve our predictive capacity of their vulnerability and/or resilience. In addition to playing a critical ecological and biogeochemical role, pteropods can offer a significant value as an early-indicator of anthropogenic OA. This role as a sentinel species should be developed further to onsolidate their potential use within marine environmental management policy making.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 3
    Publication Date: 2016-06-12
    Description: Biogeochemical and diatom export fluxes are presented from two bathypelagic sediment trap deployments in the Antarctic Zone of the Southern Ocean. One of the sediment traps was deployed in very productive, naturally iron-fertilized waters downstream of South Georgia (P3, 2000 m) and compared to a deployment in moderately productive waters upstream of the island system (P2, 1500 m). At both sites significant diatom export events occurred in spring (November) and contained mostly empty cells that were associated with low particulate organic carbon (POC) fluxes. A summer export pulse occurred one month later at P2 (end February/March) compared to P3 (end January). Diatom fluxes at P3 were one order of magnitude higher than at P2, a difference mainly attributed to the short and intense export of resting spores from Chaetoceros Hyalochaete and Thalassiosira antarctica species. Aside from these resting spores, diatom export assemblages at both sites were dominated by empty Fragilariopsis kerguelensis frustules. The fraction of diatoms exported as empty frustules was considerably lower at P3 (52%) than P2 (91%). This difference was related to the flux of intact diatom resting spores at P3 and may partially explain the lower Si:C export stoichiometry observed at P3 (1.1) compared to P2 (1.5). Through the enumeration of full diatom frustules and subsequent biomass calculations we estimate that diatom resting spores account for 42% of annual POC flux in the productive waters downstream of South Georgia. At both sites the contribution of diatom vegetative stages to POC fluxes was considerably lower (〈5%). From these analyses we conclude that resting spore export contributes towards the slightly higher bathypelagic (POC) flux at P3 (40.6 mmol m−2 y−1) compared to P2 (26.4 mmol m−2 y−1). We compared our sediment trap records with previously published diatom assemblage data from the mixed layer and surface sediments (3760 m) around South Georgia. The relative proportion of diatom resting spores within diatom assemblages increases as a function of depth and is explained by selective preservation of their robust frustules. Our study highlights the significance of diatom resting spore export as a carbon vector out of the mixed layer. Furthermore, the contribution or resting spores to POC flux in the bathypelagic ocean and sediments suggests they play a particularly important role in sequestering biologically fixed CO2 over climatically relevant timescales.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
    Format: application/pdf
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  • 4
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    PANGAEA
    In:  Supplement to: Manno, C; Peck, Victoria L; Tarling, Geraint A (2016): Pteropod eggs released at high pCO2 lack resilience to ocean acidification. Scientific Reports, 6, 25752, https://doi.org/10.1038/srep25752
    Publication Date: 2019-09-18
    Description: The effects of ocean acidification (OA) on the early recruitment of pteropods in the Scotia Sea, was investigated considering the process of spawning, quality of the spawned eggs and their capacity to develop. Maternal OA stress was induced on female pteropods (Limacina helicina antarctica) through exposure to present day pCO2 conditions and two potential future OA states (750 matm and 1200 matm). The eggs spawned from these females, both before and during their exposure to OA, were incubated themselves in this same range of conditions (embryonic OA stress). Maternal OA stress resulted in eggs with lower carbon content, while embryonic OA stress retarded development. The combination of maternal and embryonic OA stress reduced the percentage of eggs successfully reaching organogenesis by 80%. We propose that OA stress not only affects the somatic tissue of pteropods but also the functioning of their gonads. Corresponding in-situ sampling found that post-larval L. helicina antarctica concentrated around 600 m depth, which is deeper than previously assumed. A deeper distribution makes their exposure to waters undersaturated for aragonite more likely in the near future given that these waters are predicted to shoal from depth over the coming decades.
    Type: Dataset
    Format: text/tab-separated-values, 1548 data points
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  • 5
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    PANGAEA
    In:  Supplement to: Manno, C; Morata, N; Bellerby, Richard G J (2012): Effect of ocean acidification and temperature increase on the planktonic foraminifer Neogloboquadrina pachyderma (sinistral). Polar Biology, 35(9), 1311-1319, https://doi.org/10.1007/s00300-012-1174-7
    Publication Date: 2019-09-18
    Description: The present study investigated the effects of ocean acidification and temperature increase on Neogloboquadrina pachyderma (sinistral), the dominant planktonic foraminifer in the Arctic Ocean. Due to the naturally low concentration of [CO3] 2- in the Arctic, this foraminifer could be particularly sensitive to the forecast changes in seawater carbonate chemistry. To assess potential responses to ocean acidification and climate change, perturbation experiments were performed on juvenile and adult specimens by manipulating seawater to mimic the present-day carbon dioxide level and a future ocean acidification scenario (end of the century) under controlled (in situ) and elevated temperatures (1 and 4 °C, respectively). Foraminifera mortality was unaffected under all the different experiment treatments. Under low pH, N. pachyderma (s) shell net calcification rates decreased. This decrease was higher (30 %) in the juvenile specimens than decrease observed in the adults (21 %) ones. However, decrease in net calcification was moderated when both, pH decreased and temperature increased simultaneously. When only temperature increased, a net calcification rate for both life stages was not affected. These results show that forecast changes in seawater chemistry would impact calcite production in N. pachyderma (s), possibly leading to a reduction of calcite flux contribution and consequently a decrease in biologic pump efficiency.
    Type: Dataset
    Format: text/tab-separated-values, 7932 data points
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  • 6
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    PANGAEA
    In:  Supplement to: Manno, C; Morata, N; Primicerio, Raul (2012): Limacina retroversa's response to combined effects of ocean acidification and sea water freshening. Estuarine, Coastal and Shelf Science, 113, 163-171, https://doi.org/10.1016/j.ecss.2012.07.019
    Publication Date: 2019-09-18
    Description: Anthropogenic carbon dioxide emissions induce ocean acidification, thereby reducing carbonate ion concentration, which may affect the ability of calcifying organisms to build shells. Pteropods, the main planktonic producers of aragonite in the worlds' oceans, may be particularly vulnerable to changes in sea water chemistry. The negative effects are expected to be most severe at high-latitudes, where natural carbonate ion concentrations are low. In this study we investigated the combined effects of ocean acidification and freshening on Limacina retroversa, the dominant pteropod in sub polar areas. Living L. retroversa, collected in Northern Norwegian Sea, were exposed to four different pH values ranging from the pre-industrial level to the forecasted end of century ocean acidification scenario. Since over the past half-century the Norwegian Sea has experienced a progressive freshening with time, each pH level was combined with a salinity gradient in two factorial, randomized experiments investigating shell degradation, swimming behavior and survival. In addition, to investigate shell degradation without any physiologic influence, one perturbation experiments using only shells of dead pteropods was performed. Lower pH reduced shell mass whereas shell dissolution increased with pCO2. Interestingly, shells of dead organisms had a higher degree of dissolution than shells of living individuals. Mortality of Limacina retroversa was strongly affected only when both pH and salinity reduced simultaneously. The combined effects of lower salinity and lower pH also affected negatively the ability of pteropods to swim upwards. Results suggest that the energy cost of maintaining ion balance and avoiding sinking (in low salinity scenario) combined with the extra energy cost necessary to counteract shell dissolution (in high pCO2 scenario), exceed the available energy budget of this organism causing the pteropods to change swimming behavior and begin to collapse. Since L. retroversa play an important role in the transport of carbonates to the deep oceans these findings have significant implications for the mechanisms influencing the inorganic carbon cycle in the sub-polar area.
    Type: Dataset
    Format: text/tab-separated-values, 45643 data points
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  • 7
    Publication Date: 2017-08-26
    Description: Author(s): Behrouz Khodadadi, Jamileh Beik Mohammadi, Claudia Mewes, Tim Mewes, M. Manno, C. Leighton, and Casey W. Miller We study the temperature-dependent static and dynamic magnetic properties of polycrystalline bilayers of permalloy ( N i 80 F e 20 , or Py) and gadolinium (Gd) bilayers using DC magnetometry and broadband ferromagnetic resonance. Magnetometry measurements reveal that the 3-nm-thick Gd layers undergo a mag... [Phys. Rev. B 96, 054436] Published Fri Aug 25, 2017
    Keywords: Magnetism
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
    Topics: Physics
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  • 8
    Publication Date: 2012-11-21
    Description: Hopping transport and the Hall effect near the insulator–metal transition in electrochemically gated poly(3-hexylthiophene) transistors Nature Communications 3, 1210 (2012). doi:10.1038/ncomms2213 Authors: Shun Wang, Mingjing Ha, Michael Manno, C Daniel Frisbie & C Leighton
    Electronic ISSN: 2041-1723
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General , Physics
    Published by Springer Nature
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  • 9
    Publication Date: 2019-06-01
    Print ISSN: 0886-6236
    Electronic ISSN: 1944-9224
    Topics: Biology , Chemistry and Pharmacology , Geography , Geosciences , Physics
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  • 10
    Publication Date: 2018-10-03
    Description: Plastic in the Oceans: Challenges and Solutions; Cambridge, United Kingdom, 7 March 2018
    Print ISSN: 0096-3941
    Electronic ISSN: 2324-9250
    Topics: Geosciences
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