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Dissolved phosphorus pools and alkaline phosphatase activity in the euphotic zone of the Western north pacific ocean.

Suzumura M, Hashihama F, Yamada N, Kinouchi S - Front Microbiol (2012)

Bottom Line: Although DIP concentrations in the euphotic zone at all stations were equally low, around the nominal method detection limit of 20 nmol L(-1), chlorophyll a (Chl a) concentrations were one order of magnitude greater at the coastal station.The ratio of the APA half-saturation constant to the ambient L-DOP concentration decreased markedly from the NPSG to the coastal station.There were substantial differences in the rate and efficiency of DOP remineralization and its contribution as the potential P source between the low-phosphate/high-biomass coastal ecosystem and the low-phosphate/low biomass oligotrophic ocean.

View Article: PubMed Central - PubMed

Affiliation: Research Institute for Environmental Management Technology, National Institute of Advanced Industrial Science and Technology Tsukuba, Japan.

ABSTRACT
We measured pools of dissolved phosphorus (P), including dissolved inorganic P (DIP), dissolved organic P (DOP) and alkaline phosphatase (AP)-hydrolyzable labile DOP (L-DOP), and kinetic parameters of AP activity (APA) in the euphotic zone in the western North Pacific Ocean. Samples were collected from one coastal station in Sagami Bay, Japan, and three offshore stations between the North Pacific subtropical gyre (NPSG) and the Kuroshio region. Although DIP concentrations in the euphotic zone at all stations were equally low, around the nominal method detection limit of 20 nmol L(-1), chlorophyll a (Chl a) concentrations were one order of magnitude greater at the coastal station. DOP was the dominant P pool, comprising 62-92% of total dissolved P at and above the Chl a maximum layer (CML). L-DOP represented 22-39% of the total DOP at the offshore stations, whereas it accounted for a much higher proportion (about 85%) in the coastal surface layers. Significant correlations between maximum potential AP hydrolysis rates and DIP concentrations or bacterial cell abundance in the offshore euphotic zone suggest that major APA in the oligotrophic surface ocean is from bacterial activity and regulated largely by DIP availability. Although the range of maximum potential APA was comparable among the environmental conditions, the in situ hydrolysis rate of L-DOP in the coastal station was 10 times those in the offshore stations. L-DOP turnover time at the CML ranged from 4.5 days at the coastal station to 84.4 days in the NPSG. The ratio of the APA half-saturation constant to the ambient L-DOP concentration decreased markedly from the NPSG to the coastal station. There were substantial differences in the rate and efficiency of DOP remineralization and its contribution as the potential P source between the low-phosphate/high-biomass coastal ecosystem and the low-phosphate/low biomass oligotrophic ocean.

No MeSH data available.


Locations of sampling stations in the western North Pacific Ocean superimposed on the moderate resolution imaging spectroradiometer (MODIS) chlorophyll image from 19 July 2010. White areas have no data because of cloud cover. The MODIS chlorophyll image is courtesy of the Japan Aerospace Exploration Agency (JAXA) and Tokai University. The red lines indicate the northern and southern boundaries of the Kuroshio Current on 14 July 2010 (Marine Information Service Office, Oceanographic Data Information Division, Hydrographic and Oceanographic Department, Japan Coast Guard, 2010).
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Figure 1: Locations of sampling stations in the western North Pacific Ocean superimposed on the moderate resolution imaging spectroradiometer (MODIS) chlorophyll image from 19 July 2010. White areas have no data because of cloud cover. The MODIS chlorophyll image is courtesy of the Japan Aerospace Exploration Agency (JAXA) and Tokai University. The red lines indicate the northern and southern boundaries of the Kuroshio Current on 14 July 2010 (Marine Information Service Office, Oceanographic Data Information Division, Hydrographic and Oceanographic Department, Japan Coast Guard, 2010).

Mentions: Field data were obtained from on board the R/V Tansei-maru on cruise KT10-13 from 8 to 19 July 2010. Samples were collected at three offshore stations along longitude 137°E in the western North Pacific (station A, 30°00.1′N; station B, 32°00.3′N; station C, 33°00.1′N) and from a coastal station (station H; 35°00.0′N, 139°20.5′E) in Sagami Bay, Japan (Figure 1). A light–depth profile was measured at station B with an underwater quantum sensor (MDS-MkV/L, JFE Advantech Corp., Hyogo, Japan). Surface seawater samples were collected with a plastic bucket and transferred to a 20-L Carboy equipped with a spigot (2322-0050, Thermo Scientific Nalgene, Rochester, NY, USA). Seawater samples were also collected at depths from 10 to 200 m using 12-L Niskin sampling bottles on a multiple-bottle rosette sampler with attached conductivity/temperature/depth (CTD) sensor. A 250-mL aliquot of water samples were passed through a 100-μm nylon mesh filter (47-mm diameter, NY1H04700, Millipore, Billerica, MA, USA) in an in-line filter holder (PFA-47, Advantec, Tokyo, Japan) connected with tubing to the outlets of the Carboy or Niskin bottle to remove large organisms and macro-detritus. A portion of the 100-μm-filtered sample was further filtered through a 0.45-μm membrane filter on a filtration apparatus (Steritop and Stericup vacuum filter cups, 150-mL funnel and bottle, SCHV U01 RE, Millipore) under gentle vacuum (<26 kPa). The filtrates were stored frozen at −30°C until P analyses at the laboratory within 1 month of sampling.


Dissolved phosphorus pools and alkaline phosphatase activity in the euphotic zone of the Western north pacific ocean.

Suzumura M, Hashihama F, Yamada N, Kinouchi S - Front Microbiol (2012)

Locations of sampling stations in the western North Pacific Ocean superimposed on the moderate resolution imaging spectroradiometer (MODIS) chlorophyll image from 19 July 2010. White areas have no data because of cloud cover. The MODIS chlorophyll image is courtesy of the Japan Aerospace Exploration Agency (JAXA) and Tokai University. The red lines indicate the northern and southern boundaries of the Kuroshio Current on 14 July 2010 (Marine Information Service Office, Oceanographic Data Information Division, Hydrographic and Oceanographic Department, Japan Coast Guard, 2010).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3307022&req=5

Figure 1: Locations of sampling stations in the western North Pacific Ocean superimposed on the moderate resolution imaging spectroradiometer (MODIS) chlorophyll image from 19 July 2010. White areas have no data because of cloud cover. The MODIS chlorophyll image is courtesy of the Japan Aerospace Exploration Agency (JAXA) and Tokai University. The red lines indicate the northern and southern boundaries of the Kuroshio Current on 14 July 2010 (Marine Information Service Office, Oceanographic Data Information Division, Hydrographic and Oceanographic Department, Japan Coast Guard, 2010).
Mentions: Field data were obtained from on board the R/V Tansei-maru on cruise KT10-13 from 8 to 19 July 2010. Samples were collected at three offshore stations along longitude 137°E in the western North Pacific (station A, 30°00.1′N; station B, 32°00.3′N; station C, 33°00.1′N) and from a coastal station (station H; 35°00.0′N, 139°20.5′E) in Sagami Bay, Japan (Figure 1). A light–depth profile was measured at station B with an underwater quantum sensor (MDS-MkV/L, JFE Advantech Corp., Hyogo, Japan). Surface seawater samples were collected with a plastic bucket and transferred to a 20-L Carboy equipped with a spigot (2322-0050, Thermo Scientific Nalgene, Rochester, NY, USA). Seawater samples were also collected at depths from 10 to 200 m using 12-L Niskin sampling bottles on a multiple-bottle rosette sampler with attached conductivity/temperature/depth (CTD) sensor. A 250-mL aliquot of water samples were passed through a 100-μm nylon mesh filter (47-mm diameter, NY1H04700, Millipore, Billerica, MA, USA) in an in-line filter holder (PFA-47, Advantec, Tokyo, Japan) connected with tubing to the outlets of the Carboy or Niskin bottle to remove large organisms and macro-detritus. A portion of the 100-μm-filtered sample was further filtered through a 0.45-μm membrane filter on a filtration apparatus (Steritop and Stericup vacuum filter cups, 150-mL funnel and bottle, SCHV U01 RE, Millipore) under gentle vacuum (<26 kPa). The filtrates were stored frozen at −30°C until P analyses at the laboratory within 1 month of sampling.

Bottom Line: Although DIP concentrations in the euphotic zone at all stations were equally low, around the nominal method detection limit of 20 nmol L(-1), chlorophyll a (Chl a) concentrations were one order of magnitude greater at the coastal station.The ratio of the APA half-saturation constant to the ambient L-DOP concentration decreased markedly from the NPSG to the coastal station.There were substantial differences in the rate and efficiency of DOP remineralization and its contribution as the potential P source between the low-phosphate/high-biomass coastal ecosystem and the low-phosphate/low biomass oligotrophic ocean.

View Article: PubMed Central - PubMed

Affiliation: Research Institute for Environmental Management Technology, National Institute of Advanced Industrial Science and Technology Tsukuba, Japan.

ABSTRACT
We measured pools of dissolved phosphorus (P), including dissolved inorganic P (DIP), dissolved organic P (DOP) and alkaline phosphatase (AP)-hydrolyzable labile DOP (L-DOP), and kinetic parameters of AP activity (APA) in the euphotic zone in the western North Pacific Ocean. Samples were collected from one coastal station in Sagami Bay, Japan, and three offshore stations between the North Pacific subtropical gyre (NPSG) and the Kuroshio region. Although DIP concentrations in the euphotic zone at all stations were equally low, around the nominal method detection limit of 20 nmol L(-1), chlorophyll a (Chl a) concentrations were one order of magnitude greater at the coastal station. DOP was the dominant P pool, comprising 62-92% of total dissolved P at and above the Chl a maximum layer (CML). L-DOP represented 22-39% of the total DOP at the offshore stations, whereas it accounted for a much higher proportion (about 85%) in the coastal surface layers. Significant correlations between maximum potential AP hydrolysis rates and DIP concentrations or bacterial cell abundance in the offshore euphotic zone suggest that major APA in the oligotrophic surface ocean is from bacterial activity and regulated largely by DIP availability. Although the range of maximum potential APA was comparable among the environmental conditions, the in situ hydrolysis rate of L-DOP in the coastal station was 10 times those in the offshore stations. L-DOP turnover time at the CML ranged from 4.5 days at the coastal station to 84.4 days in the NPSG. The ratio of the APA half-saturation constant to the ambient L-DOP concentration decreased markedly from the NPSG to the coastal station. There were substantial differences in the rate and efficiency of DOP remineralization and its contribution as the potential P source between the low-phosphate/high-biomass coastal ecosystem and the low-phosphate/low biomass oligotrophic ocean.

No MeSH data available.