18 research outputs found
Temperature-enhanced effects of iron on Southern Ocean phytoplankton - associated data
No full textIron (Fe) is a key limiting nutrient for Southern Ocean phytoplankton. Input of Fe into the Southern Ocean is projected to change due to global warming, yet the combined effects of a concurrent increase in temperature with dissolved Fe (dFe) addition on phytoplankton growth and community composition are understudied. To improve our understanding of how Antarctic phytoplankton communities respond to Fe and enhanced temperature, we performed four full factorial onboard bioassays under trace metal clean conditions with phytoplankton communities from different regions of the Weddell and the Amundsen Seas in the Southern Ocean. Treatments consisted of a combined 2 nM dFe addition with 2 °C warming treatment (TF), compared to the single factor treatments of Fe addition at in-situ temperature (F), and non-Fe addition at + 2 °C (T) and at in-situ temperature (C). Temperature had limited effect by itself but boosted the positive response of the phytoplankton to Fe addition. Photosynthetic efficiency, phytoplankton abundances, and chlorophyll a concentrations typically increased (significantly) with dFe addition (F and/or TF treatments) and the phytoplankton community generally shifted from haptophytes to diatoms upon dFe addition. The < 20 µm phytoplankton fraction displayed population-specific growth responses, resulting in a pronounced shift in community composition and size distribution (mainly towards larger-sized phytoplankton) for the F and TF treatment. Such distinct enhanced impact of dFe supply with warming on Antarctic phytoplankton size, growth and composition will likely affect trophic transfer efficiency and ecosystem structure, with potential significance for the biological carbon pump
Trace Metals Amundsen Sea Araon ANA08B and Weddell Sea PS117
No full textAmundsen ANA08B: Samples were collected onboard the South Korean icebreaker RV Araon during the ANA08B research expedition to the Amundsen Sea in the austral summer of 2017/2018. The sampling period spanned from the 24th of January to the 2nd of February 2018. A total of 10 full depth stations were investigated with a maximum of 12 sampling depths. The transect followed the in- and outflow of CDW in the ASP through a trough near the Dotson ice shelf. The ASP was surrounded by sea ice at the start of the sampling campaign, whereas the polynya had started to open to the open ocean on the northwest side by the end of sampling. Along this transect, station 53 was located off the shelf and outside the polynya in the marginal sea ice zone, station 52 was located near the outermost edge of the polynya at the shelf break, stations 42 and 36 were located at the Dotson Ice Shelf front on the in -and outflow side respectively, and the remaining stations were located in the central open water body of the ASP. Water was collected with the ‘Titan’ ultraclean CTD sampling system for trace metals mounted with pristine large volume samplers. To prevent light shock of phytoplankton, the original PVDF samplers were replaced by a light-proof version of the Pristine samplers and were made from polypropylene. The salinity (conductivity), temperature, fluorescence, depth (pressure) and oxygen were measured with a CTD (Seabird SBE 911+) mounted on the trace metal clean sampling system of NIOZ. The sampling system was deployed on a 11 mm Dyneema cable without internal conductive wires and therefore an SBE 17 plus V2 Searam in a titanium housing provided power, saved the CTD data and closed the sampling bottles at pre-programmed depths. After deployment, the complete CTD sampling system was placed in a cleanroom environment inside a modified high cube shipping container and subsamples were collected.
Weddell Sea PS117: Samples were collected on board the German icebreaker RV Polarstern during the PS117 research expedition to the Weddell Sea in the austral summer of 2018/2019. The sampling period spanned from the 26th of January to the 1st of February 2019. A total of 23 (semi)full depth stations were taken with a maximum of 20 sampling depths. Samples for trace metals were collected along the prime meridian (0° W) transect in December/January 2018-2019 at 8 stations. Northernmost station 22 is located at 59°S and southernmost station 30 at 69.37° S. Additionally, 4 stations were samples near the ice sheet and in the Weddell Basin that were not along a transect. Due to the malfunctioning sampling system, deepest depths were not sampled correctly and can therefore not be used in the analysis. Along the Weddell Sea transect a total of 11 trace metal stations, of which 6 full depth, were sampled in January/February 2019. The transect starts in the Weddell Sea basin at station 61 (45.8°W) and followed the continental slope towards the West-Antarctic peninsula where the shelf station 95 was closest to the continent (54.5° W).
Water was collected with the ‘Titan’ ultraclean CTD sampling system for trace metals mounted with pristine large volume samplers. To prevent light shock of phytoplankton, the original PVDF samplers were replaced by a light-proof version of the Pristine samplers and were made from polypropylene. The salinity (conductivity), temperature, fluorescence, depth (pressure) and oxygen were measured with a CTD (Seabird SBE 911+) mounted on the trace metal clean sampling system of NIOZ. The sampling system was deployed on a 11 mm Dyneema cable without internal conductive wires and therefore an SBE 17 plus V2 Searam in a titanium housing provided power, saved the CTD data and closed the sampling bottles at pre-programmed depths. After deployment, the complete CTD sampling system was placed in a cleanroom environment inside a modified high cube shipping container and subsamples were collected
Diapycnal nutrient mixing
No full textIn this data file nutrient, DFe and raw CTD data are available used for the paper
"Diapycnal mixing across the photic zone of the NE-Atlantic".
Variable physical conditions such as vertical turbulent exchange, internal wave and mesoscale eddy action, affect the availability of light and nutrients for phytoplankton (unicellular algae) growth. It is hypothesized that changes in ocean temperature may affect ocean vertical density stratification, which may hamper vertical exchange. In order to quantify variations in physical conditions in the Northeast Atlantic Ocean, we sampled a latitudinal transect along 17 degrees 5minutes W between 30 and 63 degrees N in summer. A shipborne Conductivity-Temperature-Depth CTD-instrumented package was used with a custom-made modification of the pump-inlet to minimize detrimental effects of ship motions on its data. Thorpe-scale analysis was used to establish turbulence values for the upper 500 m from 3 to 6 profiles obtained in a short CTD-yoyo, 3 to 5 h after local sunrise. From south to north, average temperature decreased together with stratification while turbulence values weakly increased or remained constant. Vertical turbulent nutrient fluxes did not vary significantly with stratification and latitude. This apparent lack of correspondence between turbulent mixing and temperature is likely due to internal waves breaking (increased stratification can support more internal waves), acting as a potential feed-back mechanism. As this feed-back mechanism mediates potential physical environment changes in temperature, global surface ocean warming may not affect the vertical nutrient fluxes to a large degree. We urge modelers to test this deduction as it could imply that the future summer phytoplankton productivity in stratified oligotrophic waters would experience little alterations in nutrient input from deeper waters
Diapycnal mixing across the photic zone of the NE Atlantic
No full textVariable physical conditions such as vertical turbulent exchange, internal wave, and mesoscale eddy action affect the availability of light and nutrients for phytoplankton (unicellular algae) growth. It is hypothesized that changes in ocean temperature may affect ocean vertical density stratification, which may hamper vertical exchange. In order to quantify variations in physical conditions in the northeast Atlantic Ocean, we sampled a latitudinal transect along 17 ± 5∘ W between 30 and 63∘ N in summer. A shipborne conductivity–temperature–depth (CTD) instrumented package was used with a custom-made modification of the pump inlet to minimize detrimental effects of ship motions on its data. Thorpe-scale analysis was used to establish turbulence values for the upper 500 m from three to six profiles obtained in a short CTD yo-yo, 3 to 5 h after local sunrise. From south to north, average temperature decreased together with stratification while turbulence values weakly increased or remained constant. Vertical turbulent nutrient fluxes did not vary significantly with stratification and latitude. This apparent lack of correspondence between turbulent mixing and temperature is likely due to internal waves breaking (increased stratification can support more internal waves), acting as a potential feedback mechanism. As this feedback mechanism mediates potential physical environment changes in temperature, global surface ocean warming may not affect the vertical nutrient fluxes to a large degree. We urge modellers to test this deduction as it could imply that the future summer phytoplankton productivity in stratified oligotrophic waters would experience little alterations in nutrient input from deeper waters
Dissolved zinc and cadmium isotope systematics in the Amundsen and Weddell coastal Antarctic marginal seas
No full textCoastal Antarctica is experiencing rapid environmental change with potential effects on regional marine trace element biogeochemistry. Here, we investigate the biogeochemistry of two dissolved bioactive trace elements, zinc (Zn) and cadmium (Cd), and their isotope ratios (δ66Zn and δ114Cd) in two coastal marginal seas with distinct oceanographic features – the Amundsen Sea with the intrusion of Circumpolar Deep Water (CDW) onto the Antarctic continental shelf, and the Weddell Sea where formation of Antarctic Bottom Water occurs. In the Amundsen Sea, our isotope data show CDW predominantly controls δ66Zn and δ114Cd on the continental shelf. This result is consistent with previous concentration-focused studies that suggested only a negligible addition of Zn and Cd from continental sediments and ice shelf meltwater, and other processes (e.g., scavenging) play a limited role in their cycling on the shelf region. In the Weddell Sea, homogeneous δ66Zn and δ114Cd within different water masses across the Antarctic Peninsula shelf, while Zn and Cd concentrations increase via physical mixing with deep water masses, suggest a preformed isotope signature on the continental shelf. In surface waters of both regions, δ114Cd exhibited isotope fractionation linked to biological uptake, with different Rayleigh closed system fractionation factors (α = Rbiomass/Rseawater) for regions dominated by haptophytes (0.99930–0.99960) and diatoms (0.99970–0.99995) and we speculate that such differences may be associated with variability between species. In contrast, estimated fractionation factors for Zn in haptophytes (0.99995) and diatoms (0.99980–0.99995) dominated blooms are similar and comparable to reported values in the Southern Ocean (0.99995 ± 0.00001). At the intermediate depth (250–1500 m) in the Weddell Sea, significantly lower δ114Cd in the inner gyre compared to the outer gyre implies Cd regeneration and reduced ventilation. This pattern was not observed for δ⁶⁶Zn, likely due to its smaller biological fractionation in the surface. These findings confirm the role of CDW as the main source of Zn and Cd to the Amundsen Sea and the importance of physical mixing in setting global dissolved Zn and Cd distributions during the formation of deep waters in the Weddell Sea, providing insights into the impacts of regional coastal systems on the biogeochemistry of Zn and Cd.</p
Diapycnal nutrient mixing
No full textIn this data file nutrient, DFe and raw CTD data are available used for the paper
"Diapycnal mixing across the photic zone of the NE-Atlantic".
Variable physical conditions such as vertical turbulent exchange, internal wave and mesoscale eddy action, affect the availability of light and nutrients for phytoplankton (unicellular algae) growth. It is hypothesized that changes in ocean temperature may affect ocean vertical density stratification, which may hamper vertical exchange. In order to quantify variations in physical conditions in the Northeast Atlantic Ocean, we sampled a latitudinal transect along 17 degrees 5minutes W between 30 and 63 degrees N in summer. A shipborne Conductivity-Temperature-Depth CTD-instrumented package was used with a custom-made modification of the pump-inlet to minimize detrimental effects of ship motions on its data. Thorpe-scale analysis was used to establish turbulence values for the upper 500 m from 3 to 6 profiles obtained in a short CTD-yoyo, 3 to 5 h after local sunrise. From south to north, average temperature decreased together with stratification while turbulence values weakly increased or remained constant. Vertical turbulent nutrient fluxes did not vary significantly with stratification and latitude. This apparent lack of correspondence between turbulent mixing and temperature is likely due to internal waves breaking (increased stratification can support more internal waves), acting as a potential feed-back mechanism. As this feed-back mechanism mediates potential physical environment changes in temperature, global surface ocean warming may not affect the vertical nutrient fluxes to a large degree. We urge modelers to test this deduction as it could imply that the future summer phytoplankton productivity in stratified oligotrophic waters would experience little alterations in nutrient input from deeper waters
Trace Metals Amundsen Sea Araon ANA08B
No full textSamples were collected onboard the South Korean icebreaker RV Araon during the ANA08B research expedition to the Amundsen Sea in the austral summer of 2017/2018. The sampling period spanned from the 24th of January to the 2nd of February 2018. A total of 10 full depth stations were investigated with a maximum of 12 sampling depths. The transect followed the in- and outflow of CDW in the ASP through a trough near the Dotson ice shelf. The ASP was surrounded by sea ice at the start of the sampling campaign, whereas the polynya had started to open to the open ocean on the northwest side by the end of sampling. Along this transect, station 53 was located off the shelf and outside the polynya in the marginal sea ice zone, station 52 was located near the outermost edge of the polynya at the shelf break, stations 42 and 36 were located at the Dotson Ice Shelf front on the in -and outflow side respectively, and the remaining stations were located in the central open water body of the ASP. Water was collected with the ?Titan? ultraclean CTD sampling system for trace metals mounted with pristine large volume samplers. To prevent light shock of phytoplankton, the original PVDF samplers were replaced by a light-proof version of the Pristine samplers and were made from polypropylene. The salinity (conductivity), temperature, fluorescence, depth (pressure) and oxygen were measured with a CTD (Seabird SBE 911+) mounted on the trace metal clean sampling system of NIOZ. The sampling system was deployed on a 11 mm Dyneema cable without internal conductive wires and therefore an SBE 17 plus V2 Searam in a titanium housing provided power, saved the CTD data and closed the sampling bottles at pre-programmed depths. After deployment, the complete CTD sampling system was placed in a cleanroom environment inside a modified high cube shipping container and subsamples were collected
Clinical decision trees support systematic evaluation of multidisciplinary team recommendations
No full textPurpose: EUSOMA’s recommendation that “each patient has to be fully informed about each step in the diagnostic and therapeutic pathway” could be supported by guideline-based clinical decision trees (CDTs). The Dutch breast cancer guideline has been modeled into CDTs (www.oncoguide.nl). Prerequisites for adequate CDT usage are availability of necessary patient data at the time of decision-making and to consider all possible treatment alternatives provided in the CDT. Methods: This retrospective single-center study evaluated 394 randomly selected female patients with non-metastatic breast cancer between 2012 and 2015. Four pivotal CDTs were selected. Two researchers analyzed patient records to determine to which degree patient data required per CDT were available at the time of multidisciplinary team (MDT) meeting and how often multiple alternatives were actually reported. Results: The four selected CDTs were indication for magnetic resonance imaging (MRI) scan, preoperative and adjuvant systemic treatment, and immediate breast reconstruction. For 70%, 13%, 97% and 13% of patients, respectively, all necessary data were available. The two most frequent underreported data-items were “clinical M-stage” (87%) and “assessable mammography” (28%). Treatment alternatives were reported by MDTs in 32% of patients regarding primary treatment and in 28% regarding breast reconstruction. Conclusion: Both the availability of data in patient records essential for guideline-based recommendations and the reporting of possible treatment alternatives of the investigated CDTs were low. To meet EUSOMA’s requirements, information that is supposed to be implicitly known must be explicated by MDTs. Moreover, MDTs have to adhere to clear definitions of data-items in their reporting
Temperature-enhanced effects of iron on Southern Ocean phytoplankton
No full textIron (Fe) is a key limiting nutrient for Southern Ocean phytoplankton. Input of Fe into the Southern Ocean is projected to change due to global warming, yet the combined effects of a concurrent increase in temperature with dissolved Fe (dFe) addition on phytoplankton growth and community composition have not been extensively studied. To improve our understanding of how Antarctic phytoplankton communities respond to Fe and enhanced temperature, we performed four full factorial onboard bioassays under trace-metal-clean conditions with phytoplankton communities from different regions of the Weddell Sea and the Amundsen Sea in the Southern Ocean. Treatments consisted of 2 nM Fe addition with 2 °C warming (TF), Fe addition at in situ temperature (F) +2 °C warming with no Fe addition (T) and a control at in situ temperature with no Fe addition (control, C). Temperature had a limited effect by itself but boosted the positive response of the phytoplankton to Fe addition. Photosynthetic efficiency, phytoplankton abundances and chlorophyll a concentrations typically increased (significantly) with Fe addition (F and/or TF treatment), and the phytoplankton community generally shifted from haptophytes to diatoms upon Fe addition. The < 20 µm phytoplankton fraction displayed population-specific growth responses, resulting in a pronounced shift in community composition and size distribution (mainly towards larger-sized phytoplankton) for the F and TF treatments. Such a distinct enhanced impact of dFe supply with warming on Antarctic phytoplankton size, growth and composition will likely affect trophic transfer efficiency and ecosystem structure, with potential significance for the biological carbon pump.</p
Ecological Importance of Viral Lysis as a Loss Factor of Phytoplankton in the Amundsen Sea
No full textWhether phytoplankton mortality is caused by grazing or viral lysis has important implications for phytoplankton dynamics and biogeochemical cycling. The ecological relevance of viral lysis for Antarctic phytoplankton is still under-studied. The Amundsen Sea is highly productive in spring and summer, especially in the Amundsen Sea Polynya (ASP), and very sensitive to global warming-induced ice-melt. This study reports on the importance of the viral lysis, compared to grazing, of pico- and nanophytoplankton, using the modified dilution method (based on apparent growth rates) in combination with flow cytometry and size fractionation. Considerable viral lysis was shown for all phytoplankton populations, independent of sampling location and cell size. In contrast, the average grazing rate was 116% higher for the larger nanophytoplankton, and grazing was also higher in the ASP (0.45 d−1 vs. 0.30 d−1 outside). Despite average specific viral lysis rates being lower than grazing rates (0.17 d−1 vs. 0.29 d−1), the average amount of phytoplankton carbon lost was similar (0.6 µg C L−1 d−1 each). The viral lysis of the larger-sized phytoplankton populations (including diatoms) and the high lysis rates of the abundant P. antarctica contributed substantially to the carbon lost. Our results demonstrate that viral lysis is a principal loss factor to consider for Southern Ocean phytoplankton communities and ecosystem production
