| Processing Steps |
- Parameter or Variable: DISSOLVED INORGANIC CARBON (DIC) (measured); Units: micromole/liter; Observation Category: laboratory analysis; Sampling Instrument: 15 mL syringe from 1L quartz bottle; Sampling and Analyzing Method: Near-surface (<0.5 m) water samples were collected from two stations along the main channel of Baffin Bay (BB3 and BB6 in Fig. 1) on August 11, 2017. Both near-surface and near-bottom (<0.5 m above the sediment) water samples were collected again at these two stations on September 18, 2017. For the August 2017 experiment, both filtered (through pre-combusted Whatman GF/F filters, pore size=0.7 µm) and whole water were distributed into ground-neck 1000-mL quartz bottles. Only filtered water was used in the September 2017 experiment. There was no duplicate bottle for all incubations. Microbial activity in all incubating bottles was stopped by adding 400 µL saturated HgCl2 solution, and the bottles were then closed and exposed to natural sunlight outdoors. The bottle stoppers were secured with Parafilm® and placed in a plastic tray (89.9 cm ×42.5 cm×14.9 cm) filled with tap water. The water level in the tray was maintained near the bottle neck, which was about 14.5 cm height. The water temperature was purely controlled by air temperature (25°C~30°C). Aliquots of water samples (~12 mL) were extracted every 4-5 days using syringes from the 1000 mL quartz bottles for DIC analyses. Care was taken to minimize the opening time of bottle stoppers during sample extraction. DIC samples were stored in 4 mL borosilicate vials, which were tightly closed using phenolic screw caps with PTFE-faced rubber liner. DIC analyses were finished in two weeks after the experiment. The analytical methods for DIC was the same as those used in Wang et al. (2018). Briefly, DIC was measured with an infrared CO2 detector-based DIC analyzer (AS-C3 Apollo SciTech Inc.). Certified Reference Materials from A. G. Dickson, Scripps Institution of Oceanography were used as an independent data quality control. The precisions for DIC was within 2 µmol L-1 (±0.1%) (Chen et al. 2015). Chen, B., W.-J. Cai, and L. Chen. 2015. The marine carbonate system of the Arctic Ocean: Assessment of internal consistency and sampling considerations, summer 2010. Marine Chemistry 176: 174-188..
- Parameter or Variable: DIC-C13 (measured); Units: per mille; Observation Category: laboratory analysis; Sampling Instrument: 15 mL syringe from 1L quartz bottle; Sampling and Analyzing Method: Near-surface (<0.5 m) water samples were collected from two stations along the main channel of Baffin Bay (BB3 and BB6 in Fig. 1) on August 11, 2017. Both near-surface and near-bottom (<0.5 m above the sediment) water samples were collected again at these two stations on September 18, 2017. For the August 2017 experiment, both filtered (through pre-combusted Whatman GF/F filters, pore size=0.7 µm) and whole water were distributed into ground-neck 1000-mL quartz bottles. Only filtered water was used in the September 2017 experiment. There was no duplicate bottle for all incubations. Microbial activity in all incubating bottles was stopped by adding 400 µL saturated HgCl2 solution, and the bottles were then closed and exposed to natural sunlight outdoors. The bottle stoppers were secured with Parafilm® and placed in a plastic tray (89.9 cm ×42.5 cm×14.9 cm) filled with tap water. The water level in the tray was maintained near the bottle neck, which was about 14.5 cm height. The water temperature was purely controlled by air temperature (25°C~30°C). Aliquots of water samples (~12 mL) were extracted every 4-5 days using syringes from the 1000 mL quartz bottles for stable carbon isotope of dissolved inorganic carbon (δ13CDIC). Care was taken to minimize the opening time of bottle stoppers during sample extraction. δ13CDIC samples were save in 2 mL borosilicate autosampler vials (Restek®) with natural rubber septa lined open-top aluminum caps. δ13CDIC analyses were finished in two weeks after the experiment. The analytical methods for δ13CDIC was the same as those used in Wang et al. (2018). δ13CDIC samples were measured at J. Brandes’ lab at Skidaway Institute of Oceanography, University of Georgia. They were determined on a Thermo Fisher Delta V isotope ratio mass spectrometer (IRMS) with a GasBench II preparation module for trace gas samples. The analytical precision was ±0.1‰ (Brandes 2009). Brandes, J. A. 2009. Rapid and precise δ13C measurement of dissolved inorganic carbon in natural waters using liquid chromatography coupled to an isotope‐ratio mass spectrometer. Limnology and Oceanography: Methods 7: 730-739.
- Parameter or Variable: DOC-C13 (measured); Units: per mille; Observation Category: laboratory analysis; Sampling Instrument: 50 mL syringe from 1 L quartz bottle; Sampling and Analyzing Method: Near-surface (<0.5 m) water samples were collected from two stations along the main channel of Baffin Bay (BB3 and BB6 in Fig. 1) on August 11, 2017. Both near-surface and near-bottom (<0.5 m above the sediment) water samples were collected again at these two stations on September 18, 2017. For the August 2017 experiment, both filtered (through pre-combusted Whatman GF/F filters, pore size=0.7 µm) and whole water were distributed into ground-neck 1000-mL quartz bottles. Only filtered water was used in the September 2017 experiment. There was no duplicate bottle for all incubations. Microbial activity in all incubating bottles was stopped by adding 400 µL saturated HgCl2 solution, and the bottles were then closed and exposed to natural sunlight outdoors. The bottle stoppers were secured with Parafilm® and placed in a plastic tray (89.9 cm ×42.5 cm×14.9 cm) filled with tap water. The water level in the tray was maintained near the bottle neck, which was about 14.5 cm height. The water temperature was purely controlled by air temperature (25°C~30°C). The δ13CDOC samples were collected at the beginning and the end of each filtered water incubation and preserved in 40 mL Fisher brand borosilicate glass EPA vials with Teflon-lined silicone septa. δ13CDOC samples were preserved at pH~2 by adding concentrated HCl. The δ13CDOC samples were analyzed by C. Osburn’s lab in North Carolina State University. They were measured with a combination of an Aurora 1030C high-temperature catalytic conversion DOC analyzer, a molecular sieve trap, and a continuous-flow IRMS. The precision of the δ13CDOC analysis was ±0.2‰ (Lalonde et al. 2014). Lalonde, K., P. Middlestead, and Y. Gélinas. 2014a. Automation of 13C/12C ratio measurement for freshwater and seawater DOC using high temperature combustion. Limnology and Oceanography: Methods 12: 816-829..
- Parameter or Variable: CHLOROPHYLL A (measured); Units: microgram/liter; Observation Category: laboratory analysis; Sampling Instrument: 50 mL syringe; Sampling and Analyzing Method: Near-surface (<0.5 m) water samples were collected from two stations along the main channel of Baffin Bay (BB3 and BB6 in Fig. 1) on August 11, 2017. Both near-surface and near-bottom (<0.5 m above the sediment) water samples were collected again at these two stations on September 18, 2017. For the August 2017 experiment, both filtered (through pre-combusted Whatman GF/F filters, pore size=0.7 µm) and whole water were distributed into ground-neck 1000-mL quartz bottles. Only filtered water was used in the September 2017 experiment. There was no duplicate bottle for all incubations. Microbial activity in all incubating bottles was stopped by adding 400 µL saturated HgCl2 solution, and the bottles were then closed and exposed to natural sunlight outdoors. The bottle stoppers were secured with Parafilm® and placed in a plastic tray (89.9 cm ×42.5 cm×14.9 cm) filled with tap water. The water level in the tray was maintained near the bottle neck, which was about 14.5 cm height. The water temperature was purely controlled by air temperature (25°C~30°C). The chlorophyll a samples were collected at the beginning of the incubation. A known volume of water sample was gently filtered through Whatman GF/F filters (pore size =0.7 µm), which were then stored frozen at -20°C until analysis. Chlorophyll a was extracted from the filters by soaking for 18-24 hours in 90% HPLC-grade acetone at -20oC, after which the concentration was determined fluorometrically with a Turner Trilogy fluorometer without acidification..
- Parameter or Variable: d13Cocdegredated (calculated); Units: per mille; Observation Category: laboratory analysis; Sampling Instrument: calculated from DIC and stable carbon isotope of DIC; Sampling and Analyzing Method: The stable carbon isotope of photoreactive organic carbon was calculated using the DIC “Keeling” plot.
- Parameter or Variable: DIC change (calculated); Units: micromole/liter; Observation Category: laboratory analysis; Sampling Instrument: calculate from DIC concentration change; Sampling and Analyzing Method: the difference between maximum and minimum of dissolved inorganic carbon during each incubation treatment.
- Parameter or Variable: SALINITY (measured); Units: psu; Observation Category: in situ; Sampling Instrument: YSI - handheld multi-parameter instrument; Sampling and Analyzing Method: Salinity was measured at each site using a calibrated YSI ProPlus sonde..
- Parameter or Variable: DEPTH - SENSOR (measured); Units: meter; Observation Category: in situ; Sampling Instrument: YSI - handheld multi-parameter instrument; Sampling and Analyzing Method: Depth was measured at each site using a calibrated YSI ProPlus sonde.
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