Ratios of Si, C and N uptake by microplankton in the Southern Ocean

Brzezinski, Mark A.; Dickson, Mary-Lynn; Nelson, David M.; Sambrotto, Raymond N.

doi:10.1016/s0967-0645(02)00587-8

Cited by 114 publications

(78 citation statements)

References 46 publications

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“…4), potentially indicative of the concentration at which diatoms are out-competed for any remaining nitrate (Egge and Aksnes, 1992). Assuming that diatoms utilize silicate down to ∼1 µmol l −1 alongside an equimolar consumption of nitrate (Brzezinski et al, 2003) and that non-siliceous phytoplankton utilize any remaining nitrate, a simple model of the expected community structure response can be formulated (Fig. 5a).…”

Section: Discussionmentioning

confidence: 99%

“…In addition to acting as a tracer, we propose that the distinct Si * signatures of these water masses, negative in SAMW and positive in NPIW, may also play a role in dictating phytoplankton community responses to euphotic zone nutrient input. Si * can be considered an important indicator of nutrient availability related to the requirement of diatoms (Ragueneau et al, 2000;Brzezinski et al, 2003). When sufficient light and nutrients (including iron) are available, diatoms accumulate biomass with silicate and nitrate at a molar ratio of ∼1:1 (Brzezinski et al, 2003(Brzezinski et al, , 2005.…”

Section: Introductionmentioning

confidence: 99%

“…Si * can be considered an important indicator of nutrient availability related to the requirement of diatoms (Ragueneau et al, 2000;Brzezinski et al, 2003). When sufficient light and nutrients (including iron) are available, diatoms accumulate biomass with silicate and nitrate at a molar ratio of ∼1:1 (Brzezinski et al, 2003(Brzezinski et al, , 2005. Consequently, for a diatom population to efficiently utilize all available nitrate, it might be expected that the ambient Si * would have to be >0 µM (Ragueneau et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

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Silicate:nitrate ratios of upwelled waters control the phytoplankton community sustained by mesoscale eddies in sub-tropical North Atlantic and Pacific

Bibby

Moore

2011

Biogeosciences

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Abstract. Mesoscale eddies in sub-tropical gyres physically perturb the water column and can introduce macronutrients to the euphotic zone, stimulating a biological response in which phytoplankton communities can become dominated by large phytoplankton. Mesoscale eddies may therefore be important in driving export in oligotrophic regions of the modern ocean. However, the character and magnitude of the biological response sustained by eddies is variable. Here we present data from mesoscale eddies in the Sargasso Sea (Atlantic) and the waters off Hawai'i (Pacific), alongside mesoscale events that affected the Bermuda Atlantic TimeSeries Study (BATS) over the past decade. From this analysis, we suggest that the phytoplankton community structure sustained by mesoscale eddies is predetermined by the relative abundance of silicate over nitrate (Si * ) in the upwelled waters. We present data that demonstrate that mode-water eddies (MWE) in the Sargasso Sea upwell locally formed waters with relatively high Si * to the euphotic zone, and that cyclonic eddies in the Sargasso Sea introduce waters with relatively low Si * , a signature that originated in the iron-limited Southern Ocean. We propose that this phenomenon can explain the observed dominance of the phytoplankton community by large-diatom species in MWE and by small prokaryotic phytoplankton in cyclonic features. In contrast to the Atlantic, North Pacific Intermediate Water (NPIW) with high Si * may influence the cyclonic eddies in waters off Hawai'i, which also appear capable of sustaining diatom populations. These observations suggest that the structure of phytoplankton communities sustained by eddies may be related to the Correspondence to: T. S. Bibby (tsb@noc.soton.ac.uk) chemical composition of the upwelled waters in addition to the physical nature of the eddy.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Silicate:nitrate ratios of upwelled waters control the phytoplankton community sustained by mesoscale eddies in sub-tropical North Atlantic and Pacific

Bibby

Moore

2011

Biogeosciences

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“…These values are the Redfield ratios (Redfield 1958;Redfield et al 1963), and have often been adopted in previous studies (Turner et al 1998(Turner et al , 2003a. They are also identical to the upper limit of the ranges for N and P requirements (against a specific DSi level) of diatompredominant phytoplankton communities: an N/DSi ratio of 0.27-1.05 (Redfield et al 1963;Brzezinski 1985;Hutchins and Bruland 1998;Takeda 1998;Kudo and Matsunaga 1999;Yanada et al 1999;Koike et al 2001;Brzezinski et al 2003;Tett et al 2003) and a P/DSi Figure 1 Four target areas with river systems and sampling sites. The target areas consist of the Okitsu River and adjacent streams (OK), the Warashina River (WR), the Asahina River (OB), and the Ohta River and adjacent streams (OT).…”

Section: Critical and Precautionary Level For N And P Against Dsimentioning

confidence: 65%

“…Other studies have demonstrated the large fluctuations in the N and/or P requirement against DSi not only due to diatom species (Brezinski 1985) but also due to environmental factors such as light intensity (Brezinski 1985) and nutritional factors such as iron addition (Hutchins and Bruland 1998;Takeda 1998). The N/DSi ratio has been found to be 0.27-1.05 in several studies (Redfield 1963;Brzezinski 1985;Hutchins and Bruland 1998;Takeda 1998;Kudo and Matsunaga 1999;Yanada et al 1999;Koike et al 2001;Brzezinski et al 2003;Tett et al 2003). Incidentally, the P/DSi ratio is reported to be in the range 0.02-0.07 (Redfield 1963;Takeda 1998;Kudo and Matsunaga 1999;Yanada et al 1999).…”

Section: Introductionmentioning

confidence: 99%

Impact of agricultural land use on N and P concentration in forest-dominated tea-cultivating watersheds

Nagumo

Yosoi

Aridomi

2012

Soil Science and Plant Nutrition

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The increase in nitrogen (N) and phosphorus (P) and the decrease in dissolved silica (DSi) in aquatic environments attributed to human activities has been the focus of many studies. The resultant increases in the N/DSi and P/DSi ratios have been associated with the disturbance and deterioration of aquatic ecosystems. We investigated the impact of land use on riverine N and P as well as their ratio to DSi in 4 mountainous forest-dominated tea-cultivating areas in Shizuoka, central Japan. More than 50% of the drainage basins investigated were under forested land, while the land under tea (Camellia sinensis) fields varied from 0 to 18% and orchard fields reached up to 30% in some cases. The total nitrogen (TN) concentration was 5 mg L À1 at maximum, the majority of which was dominated by nitrate-N. An increase in the tea field area (%) within the basin resulted in significant increase in the TN concentration (p < 0.001) and in a considerably higher impact factor of 0.1-0.2 for the tea field. Orchard fields also affected the TN concentration in corresponding areas. An increase in the tea field area significantly contributed to an increase in the TN/DSi mole-based ratio. These results indicated that tea fields are a major source of riverine N. To maintain the TN/ DSi below the critical level (TN/DSi ratio <1.0), tea fields should be cultivated only in a maximum of 30% of the watershed area, and the TN concentration should be limited to 2.5 to 4.0 mg L À1. Based on the level of precaution (TN/DSi <0.3), the TN concentration should be strictly limited to less than 1 mg L À1, which is identical to the Japanese critical standard for environmental conservation of lakes and coastal seas. On the other hand, TP concentrations were almost always below 0.1 mg L À1 and the TP/DSi ratios were considerably lower than the critical level (TP/DSi <0.07). Excess N load in the tea-cultivating watersheds might accelerate the P shortage in aquatic ecosystems. N concentration should be reduced to prevent future problems. In most of our mountainous tea-cultivating watersheds, 1 mg L À1 of TN concentration could be achieved, and generally a minimum of 2.5 to 4.0 mg L À1 should be achieved. To reduce the riverine TN concentration, the fertilizer N rate should be reduced by using modern practices to enhance N fertilizer use efficiency, such as slow-released coated urea combined with cultivar selection, without producing inferior quality tea leaves.

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Sea ice diatom contributions to Holocene nutrient utilization in East Antarctica

et al. 2014

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Competing hypotheses are discussed to account for the decoupling trend in utilization proxies including iron fertilization, species-dependent fractionation effects, and diatom habitats. Based on mass balance calculations, we highlight that diatom species derived from the semi-enclosed sea ice environment may have a confounding effect upon δ 30Si downcore compositions of the seasonal sea ice zone. A diatom composition, with approximately 28% of biogenic silica derived from the sea ice environment (diat-SI) can account for the increased average composition of δ 30Si diat during the Neoglacial. These data highlight the significant role sea ice diatoms can play with relation to their export in sediment records, which has implications on productivity reconstructions from the seasonal ice zone.

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Ratios of Si, C and N uptake by microplankton in the Southern Ocean

Cited by 114 publications

References 46 publications

Silicate:nitrate ratios of upwelled waters control the phytoplankton community sustained by mesoscale eddies in sub-tropical North Atlantic and Pacific

Silicate:nitrate ratios of upwelled waters control the phytoplankton community sustained by mesoscale eddies in sub-tropical North Atlantic and Pacific

Impact of agricultural land use on N and P concentration in forest-dominated tea-cultivating watersheds

Sea ice diatom contributions to Holocene nutrient utilization in East Antarctica

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