High‐frequency measurement of seawater chemistry: Flow‐injection analysis of macronutrients

Hales, Burke; Geen, Alexander van; Takahashi, Taro

doi:10.4319/lom.2004.2.91

Cited by 48 publications

(29 citation statements)

References 21 publications

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“…Species identification with epifluorescence microscopy is usually limited, and many of the taxa are presented with the genus or group name only. Onboard analyses for the major dissolved inorganic nutrients, nitrate plus nitrite (hereafter, nitrate (NO { 3 )), dissolved inorganic phosphorus (DIP), and silicic acid, were done using standard colorimetric methodology (Grasshoff et al 1983) as adapted for flow injection analysis (FIA) on a LACHAT Instruments Quick-Chem 8000 autoanalyzer (Hales et al 2004). Dissolved ammonium (NH z 4 ) was also determined onboard with the fluorimetric method of Holmes et al (1999) using a HITACHI F2000 fluorescence spectrophotometer.…”

Section: Methodsmentioning

confidence: 99%

Biogeochemical composition of natural sea ice brines from the Weddell Sea during early austral summer

Papadimitriou

Thomas

Kennedy

et al. 2007

Limnology & Oceanography

116

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Sea ice brines were collected from a single floe composed of different ice types in the western Weddell Sea in December 2004. The chemical composition of the brines (temperature: 23.4uC to 22.1uC; salinity: 40-63) was examined on seven occasions over 25 days with measurements of dissolved oxygen, dissolved inorganic macronutrients (nitrate plus nitrite, ammonium, phosphorus [DIP], and silicic acid), pH, total alkalinity (A T ), dissolved organic carbon (DOC) and nitrogen (DON), total dissolved inorganic carbon (C T ), and the stable isotopic composition of C T (d 13 C T ). The in situ pH ranged from 8.41-8.82 on the seawater scale, dissolved oxygen from 212-604 mmol kg 21 , nitrate from 0.1-3.1 mmol kg 21 , ammonium 0.1-2.4 mmol kg 21 , DIP 0.4-2.0 mmol kg 21 , silicic acid 4-80 mmol kg 21 , A T 2,690-4,620 meq kg 21 , DOC 115-359 mmol kg 21 , DON 8-26 mmol kg 21 , C T 2,090-3,550 mmol kg 21 , and d 13 C T +2.9%-+6.4%. Compared with the chemical composition of surface oceanic water (salinity of 34), the brines had elevated pH, reduced concentrations of dissolved inorganic macronutrients (including carbon), especially dissolved inorganic nitrogen, and were mostly supersaturated with dissolved oxygen with respect to equilibrium with air, whereas the C T was considerably enriched in 13 C. The chemical composition of the brines was consistent with internal biological productivity, but there was a lack of a distinctive and uniform relationship among the major dissolved inorganic nutrients typically used for describing biological activity. This was interpreted as the result of varying stoichiometry of biological activity within a very small spatial scale. Modification by abiotic processes was a potential contributing factor, such as degassing acting on the dissolved oxygen concentration. Carbonate mineral formation, acting on A T and C T , was not evident in brines from first-year ice but was apparent in brine from second-year ice.Sea ice covers 13% of the surface of the earth at its maximum extent, equivalent to the areal extent of deserts and tundra. The largest expanse of sea ice occurs in the Southern Ocean, totalling 18.8 3 10 16 km 2 of 0.5-0.6 m mean thickness at its maximum extent in September (Comiso 2003). It is an ecologically diverse habitat and has been increasingly recognized for its key role in global biogeochemical cycles, including contribution to the primary productivity of the Southern Ocean (Arrigo 2003;Arrigo and Thomas 2004) and the ventilation of the deep ocean at high latitudes (Francois et al. 1997;Stephens and Keeling 2000).The chemical composition of sea ice is primarily a function of salinity and temperature, but it is modified further by productivity of the internal microbial assemblages recruited from the surface seawater during sea ice formation (Brierley and Thomas 2002;Thomas and Dieckmann 2002;Rysgaard et al. 2007). Primary production is a major carbon sink within sea ice, resulting in the fixation of 30-70 Tg C yr 21 into biomass in the firstand multi-year ice pack of the Sou...

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Section: Methodsmentioning

confidence: 99%

Biogeochemical composition of natural sea ice brines from the Weddell Sea during early austral summer

Papadimitriou

Thomas

Kennedy

et al. 2007

Limnology & Oceanography

116

View full text Add to dashboard Cite

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“…DOC was measured by high-temperature catalytic oxidation, using a MQ 1001 TOC Analyzer (Qian and Mopper 1996). The concentrations of NO 3 , NO 2 -, PO 4 3-, and Si(OH) 4 were determined by standard colorimetric methods (Grasshoff et al 1983) as adapted for flow injection analysis (FIA) on a LACHAT Instruments QuickChem 8000 autoanalyzer (Hales et al 2004). The PO 4 3-samples from the first sampling was contaminated, and therefore we did not include them.…”

Section: Spatial Variabilitymentioning

confidence: 99%

The relative contributions of biological and abiotic processes to carbon dynamics in subarctic sea ice

et al. 2013

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Knowledge on the relative effects of biological activity and precipitation/dissolution of calcium carbonate (CaCO 3 ) in influencing the air-ice CO 2 exchange in sea-icecovered season is currently lacking. Furthermore, the spatial and temporal occurrence of CaCO 3 and other biogeochemical parameters in sea ice are still not well described. Here we investigated autotrophic and heterotrophic activity as well as the precipitation/dissolution of CaCO 3 in subarctic sea ice in South West Greenland. Integrated over the entire ice season (71 days), the sea ice was net autotrophic with a net carbon fixation of 56 mg C m -2 , derived from a sea-icerelated gross primary production of 153 mg C m -2 and a bacterial carbon demand of 97 mg C m -2 . Primary production contributed only marginally to the TCO 2 depletion of the sea ice (7-25 %), which was mainly controlled by physical export by brine drainage and CaCO 3 precipitation. The net biological production could only explain 4 % of this sea-ice-driven CO 2 uptake. Abiotic processes contributed to an air-sea CO 2 uptake of 1.5 mmol m -2 sea ice day -1 , and dissolution of CaCO 3 increased the air-sea CO 2 uptake by 36 % compared to a theoretical estimate of melting CaCO 3 -free sea ice. There was a considerable spatial and temporal variability of CaCO 3 and the other biogeochemical parameters measured (dissolved organic and inorganic nutrients).

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“…Samples were filtered through Whatman GF/F syringe filters (pore size 0.45 µm), stored on ice and frozen (−18°C) on return to the laboratory until further analysis. The concentrations of the major dissolved inorganic nutrients, nitrate (NO 3 − ), nitrite (NO 2 − ), SRP (soluble reactive phosphorus,) and silicic acid (Si(OH) 4 ) were determined by standard colorimetric methods (Grasshoff et al 1983) as adapted for flow injection analysis (FIA) on a LACHAT Instruments Quick-Chem 8000 autoanalyzer (Hales et al 2004). The concentration of dissolved ammonium (NH 4 + ) was determined with the fluorimetric method of Holmes et al (1999) ) from that of the total dissolved nitrogen (TDN) determined by FIA on the LACHAT autoanalyzer using on-line peroxodisulfate oxidation coupled with UV radiation at pH 9.0 and 100°C (Kroon 1993).…”

Section: Samplingmentioning

confidence: 99%

Short-term variability in bacterial abundance, cell properties, and incorporation of leucine and thymidine in subarctic sea ice

Kaartokallio¹,

Søgaard²,

Norman³

et al. 2013

Aquat. Microb. Ecol.

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Sea ice is a biome of immense size and provides a range of habitats for diverse microbial communities, many of which are adapted to living at low temperatures and high salinities in brines. We measured simultaneous incorporation of thymidine (TdR) and leucine (Leu), bacterial cell abundance and cell population properties (by flow cytometry) in subarctic sea ice in SW Greenland. Short-term temporal variability was moderate, and steep environmental gradients, typical for sea ice, were the main drivers of the variability in bacterial cell properties and activity. Low nucleic acid (LNA) bacteria, previously linked to oligotrophic ecotypes in marine habitats, were more abundant in the upper ice layers, whereas high nucleic acid (HNA) bacteria dominated in lower ice, where organic carbon was in high concentrations. Leu incorporation was saturated at micromolar concentrations, as known from freshwater and marine biofilm systems. Leu:TdR ratios were high (up to > 300) in lowermost ice layers, and when compared to published respiration measurements, these results suggest non-specific Leu incorporation. There was evidence of polyhydroxyalkanoate (PHA)-containing bacteria in the sea ice, shown by brightly fluorescing intracellular inclusions after Nile Blue A staining. High Leu saturating concentrations coupled with the occurrence of PHA-producing organisms further highlight the similarity of sea ice internal habitats to biofilm-like systems rather than to open-water systems.

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High‐frequency measurement of seawater chemistry: Flow‐injection analysis of macronutrients

Cited by 48 publications

References 21 publications

Biogeochemical composition of natural sea ice brines from the Weddell Sea during early austral summer

Biogeochemical composition of natural sea ice brines from the Weddell Sea during early austral summer

The relative contributions of biological and abiotic processes to carbon dynamics in subarctic sea ice

Short-term variability in bacterial abundance, cell properties, and incorporation of leucine and thymidine in subarctic sea ice

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