Physical forcing and nutrient conditions associated with patterns of Chl a and phytoplankton productivity in the southeastern Bering Sea during summer

Sambrotto, Raymond N.; Mordy, Calvin W.; Zeeman, Stephan I.; Stabeno, Phyllis J.; Macklin, S. Allen

doi:10.1016/j.dsr2.2008.03.003

Cited by 59 publications

(36 citation statements)

References 77 publications

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“…The seaward extent of subsurface high D-Fe water ($169 W, Figure 2d) might also be limited by the size of eddies along the BSC. Isopycnal mixing along the sloping isopycnals of 25.4-25.6s q might additionally contribute to the iron-supply from iron-rich water over the shelf to the GB (Figure 2d) as suggested by previous studies [Aguilar-Islas et al, 2007;Sambrotto et al, 2008].…”

Section: Discussionmentioning

confidence: 50%

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Vertical turbulent iron flux sustains the Green Belt along the shelf break in the southeastern Bering Sea

Tanaka¹,

Yasuda²,

Kuma³

et al. 2012

Geophysical Research Letters

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[1] To evaluate the impact of vertical turbulent iron flux on the summertime biological productivity in the Bering Sea Green Belt (GB), we conducted the concurrent observations of dissolved iron (D-Fe) and turbulence in the Bering Sea for the first time. We show that the GB can be sustained by iron supply from iron-rich, subsurface thick layer distributed along the southeastern shelf break where the GB is located, via strong turbulent vertical mixing. The flux ratio of D-Fe and nitrate was within the range of the N/Fe uptake ratio by GB phytoplankton, suggesting this flux of nutrients can sustain GB productivity. We also analyzed historical hydrographic data and suggest the thick subsurface layer along the GB is formed by the mixing of relatively warm water with some iron from the Aleutian Passes and ironrich outer-shelf cold water in which the D-Fe derived from seafloor sediment is suspended due to strong vertical mixing. Citation: Tanaka, T., I. Yasuda, K. Kuma, and J. Nishioka

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Section: Discussionmentioning

confidence: 50%

“…[18] Summertime new production was estimated to be 500-1000 mgC/m 2 /day around the GB [Sambrotto et al, 2008]. Various studies have estimated the Fe:C uptake ratio of phytoplankton.…”

Section: Discussionmentioning

confidence: 99%

Vertical turbulent iron flux sustains the Green Belt along the shelf break in the southeastern Bering Sea

Tanaka¹,

Yasuda²,

Kuma³

et al. 2012

Geophysical Research Letters

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“…323, are located in the 'Green Belt' area. A relatively high deposition of organic matter is originating from the high primary production of 170 g C m À 2 y À 1 in the photic zone (Sambrotto et al, 2008) and a high sedimentation rate of 29-89 cm ky À 1 (Wehrmann et al, 2011). Deep subsurface sediments from the Peru margin (sites 1227 and 1230) and the eastern equatorial Pacific (sites 1225 and 1226), recovered during ODP Leg 201, harbor a relatively high number of cells with low metabolic activity (D'Hondt et al, 2004).…”

Section: Site Descriptionsmentioning

confidence: 99%

High virus-to-cell ratios indicate ongoing production of viruses in deep subsurface sediments

et al. 2014

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Marine sediments cover two-thirds of our planet and harbor huge numbers of living prokaryotes. Long-term survival of indigenous microorganisms within the deep subsurface is still enigmatic, as sources of organic carbon are vanishingly small. To better understand controlling factors of microbial life, we have analyzed viral abundance within a comprehensive set of globally distributed subsurface sediments. Phages were detected by electron microscopy in deep (320 m below seafloor), ancient (B14 Ma old) and the most oligotrophic subsurface sediments of the world's oceans (South Pacific Gyre (SPG)). The numbers of viruses (10 4 -10 9 cm À 3 , counted by epifluorescence microscopy) generally decreased with sediment depth, but always exceeded the total cell counts. The enormous numbers of viruses indicate their impact as a controlling factor for prokaryotic mortality in the marine deep biosphere. The virus-to-cell ratios increased in deeper and more oligotrophic layers, exhibiting values of up to 225 in the deep subsurface of the SPG. High numbers of phages might be due to absorption onto the sediment matrix and a diminished degradation by exoenzymes. However, even in the oldest sediments, microbial communities are capable of maintaining viral populations, indicating an ongoing viral production and thus, viruses provide an independent indicator for microbial life in the marine deep biosphere.

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“…Although nitrate is present in sufficient concentrations to support significant productivity in the outer domain of the Bering Sea Shelf, production is low in this region compared to the middle shelf. This is likely due to iron limitation: in general, iron concentrations tend to be highest nearer the coast, and decrease off the shelf where iron-deficient basin waters have a greater influence on the water column (Fujishima et al, 2001;Takata el al., 2005;Suzuki et al, 2002;Sambrotto et al, 2008). Over the Outer Domain, iron is not present in high enough concentrations to allow complete drawdown of macronutrients, and some classify this area as a High-Nutrient, Low-Chlorophyll system as a result (Aguilar-Islas et al, 2007;Banse and English, 1999;Fung et al, 2000;Moore et al, 2002).…”

Section: Primary Production Variability Within the Different Bering Smentioning

confidence: 99%

Seasonal distribution of dissolved inorganic carbon and net community production on the Bering Sea shelf

et al. 2010

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Abstract. In order to assess the current state of net community production (NCP) in the southeastern Bering Sea, we measured the spatio-temporal distribution and controls on dissolved inorganic carbon (DIC) concentrations in spring and summer of 2008 across six shelf domains defined by differing biogeochemical characteristics. DIC concentrations were tightly coupled to salinity in spring and ranged from ∼1900 µmoles kg −1 over the inner shelf to ∼2400 µmoles kg −1 in the deeper waters of the Bering Sea. In summer, DIC concentrations were lower due to dilution from sea ice melt, terrestrial inputs, and primary production. Concentrations were found to be as low ∼1800 µmoles kg −1 over the inner shelf. We found that DIC concentrations were drawn down 30-150 µmoles kg −1 in the upper 30 m of the water column due to primary production and calcium carbonate formation between the spring and summer occupations. Using the seasonal drawdown of DIC, estimated rates of NCP on the inner, middle, and outer shelf averaged 28 ± 9 mmoles C m −2 d −1 . However, higher rates of NCP (40-47 mmoles C m −2 d −1 ) were observed in the "Green Belt" where the greatest confluence of nutrient-rich basin water and iron-rich shelf water occurs. We estimated that in 2008, total NCP across the shelf was on the order of ∼96 Tg C yr −1 . Due to the paucity of consistent, comparable productivity data, it is impossible at this time to quantify whether the system is becoming more or less productive. However, as changing climate continues to modify the character of the Bering Sea, we have shown that NCP can be an important indicator of how the ecosystem is functioning.

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Physical forcing and nutrient conditions associated with patterns of Chl a and phytoplankton productivity in the southeastern Bering Sea during summer

Cited by 59 publications

References 77 publications

Vertical turbulent iron flux sustains the Green Belt along the shelf break in the southeastern Bering Sea

Vertical turbulent iron flux sustains the Green Belt along the shelf break in the southeastern Bering Sea

High virus-to-cell ratios indicate ongoing production of viruses in deep subsurface sediments

Seasonal distribution of dissolved inorganic carbon and net community production on the Bering Sea shelf

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