Geographic variations in the relationship between silicic acid and nitrate in the South Pacific Ocean

Zentara, Sara-Joan; Kamykowski, Daniel

doi:10.1016/0198-0149(81)90137-0

Cited by 57 publications

(42 citation statements)

References 17 publications

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“…According to these data, the regression intercepts range between nitrate concentrations less than 5 pM N and silicic acid concentrations less than 10 pM Si over most of the world ocean except south of the southern Subtropical Convergence. As shown by Zentara & Kamykowski (1981) for the Pacific sector, the Southern Ocean north of the Antarctic Divergence exhibits a potential for nitrate excess above 15 pM N at silicic acid depletion in all sectors. The GEOSECS data does not extend far (1977).…”

Section: Methodsmentioning

confidence: 99%

“…Fig. 1 shows that high projected at nitrate depletion south of the Antarctic quality data readily suwive the applied selection Divergence (Zentara & Kamykowski 1981). The criteria and provide a standard for the NODC data set.…”

Section: Methodsmentioning

confidence: 99%

“…The results of this effort provide a description of how these 2 plant nutrients CO-vary in the upper part of the world ocean. The Southern Ocean is the focus of a detailed discussion of mechanisms and implications because of its rich variability in the relation between nitrate and silicic acid concentrations and because of the downstream influence that the nutrient patterns generated in this region exercise on phytoplankton community structure (Zentara & Kamykowski 1981).…”

Section: Introductionmentioning

confidence: 99%

“…Harrison et al (1981) have refined this generalization near the equator off the coast of Peru based on nonlinear nutrient relations with depth. Zentara & Kamykowski (1981) have further examined the Southern Hemisphere nutrient patterns in the Pacific Ocean. Although South Pacific Central Water exhibits nearly simultaneous nitrate and silicic acid depletion, the water south of the Subtropical Convergence generally exhibits a potential for nitrate excess at silicic acid depletion.…”

Section: Introductionmentioning

confidence: 99%

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Nitrate and silicic acid in the world ocean: patterns and processes

Kamykowski¹,

Zentara²

1985

Mar. Ecol. Prog. Ser.

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Two world ocean data sets, GEOSECS and NODC, were analyzed for patterns in the nitrate versus silicic acid regression relation. Significant regional nitrate or silicic acid excesses (i.e. amount of one of these plant nutrients remaining in the water after the other is no longer measurable) tend to occur in some areas of upwelling, shallow sills, deep convection or high rainfall/river outflow. The Southern Ocean is unique in the intensity and complexity of projected (regression intercepts on the nitrate [y] or silicic acid [X] axis) excesses. These global nutrient depletion patterns pertain to regional comparisons of phytoplankton succession and thus to the overall character of plankton community structure. Intercept patterns in different areas are affected by the processes that determine absolute nutrient concentrations at the beginning, and their relative decline during, the growth season. The region south of the southern Polar Front is unlque because winter nutrient concentrations are unusually high around Antarctica due to water mass characteristics and because nutrients generally remain unusually abundant over the growth season partly in response to the cycle of incident solar radiation. The patterns in the regression intercepts in this region largely result from variations in the regression slopes which respond to different weightings of the chemical and biological pathways that determine nitrate and silicic acid concentrations in the upper water column. The nitrate and silicic acid profiles in the Southern Ocean contain information on the temporal average of primary production and of nitrogen recycling up to the tlme of sample collection within the growth season. The interpretation of this information depends on the detail to which the processes that determine the water column concentrations of nitrate and silicic acid are known.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Nitrate and silicic acid in the world ocean: patterns and processes

Kamykowski¹,

Zentara²

1985

Mar. Ecol. Prog. Ser.

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“…Results from CTD and XBT's displayed a mixed-layer, underpinned by a sharp pycnocline, with depths &65 m as suggested by the desktop survey . Mixed-layer nitrate and phosphate concentrations (Table 1) were relatively high, silicic acid concentrations intermediate (see Zentara and Kamykowski, 1981), and dissolved iron levels were relatively low for polar waters (see de Baar et al, 1999). The phytoplankton community exhibited sub-optimal values of photosynthetic competence (F /F , see Table 1) and was thus resource-limited, and based on the #avodoxin assay the resident diatoms were iron-stressed .…”

Section: The Soiree Sitementioning

confidence: 99%

The Southern Ocean Iron RElease Experiment (SOIREE)—introduction and summary

Boyd

Law

2001

Deep Sea Research Part II: Topical Studies in Oceanography

191

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This volume is dedicated to the Southern Ocean Iron RElease Experiment (SOIREE), the "rst in situ iron fertilisation experiment performed in the polar waters of the Southern Ocean. SOIREE was an interdisciplinary study involving participants from six countries, and took place in February 1999 south of the Polar Front in the Australasian-Paci"c sector of the Southern Ocean. Approximately 3800 kg of acidi"ed FeSO . 7H O and 165 g of the tracer sulphur hexa#uoride (SF ) were added to a 65-m deep surface mixed layer over an area of &50 km. Initially, mean dissolved iron concentrations were &2.7 nM, but decreased to ambient levels within days, requiring subsequent additions of 1550}1750 kg of acidi"ed FeSO .7H O on days 3, 5 and 7 of the experiment. During the 13-day site occupation there were iron-mediated increases in phytoplankton growth rates, with marked increases in chlorophyll a (up to 2 g l\) and production rates (up to 1.3 g C m\ d\). These resulted in subsequent changes in the pelagic ecosystem structure, and in the cycling of carbon, silica and sulphur, such as a 10% drawdown of surface CO . The SOIREE bloom persisted for '40 days following our departure from the site, as observed via SeaWiFS remotely sensed observations of Ocean Colour. Papers in this volume report in detail on aspects of this study, from the oceanographic setting of the experiment to a modelling simulation of the SOIREE bloom. A CD-ROM accompanies this volume and contains the main SOIREE datasets and ancillary information including the pre-experiment &desktop' database study for site-selection, and satellite images of the SOIREE bloom.

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Annual cycles of deep‐ocean biogeochemical export fluxes in subtropical and subantarctic waters, southwest Pacific Ocean

2016

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The annual cycles of particle fluxes derived from moored sediment trap data collected during 2000–2012 in subtropical (STW) and subantarctic waters (SAW) east of New Zealand are presented. These observations are the most comprehensive export flux time series from temperate Southern Hemisphere latitudes to date. With high levels of variability, fluxes in SAW were markedly lower than in STW, reflecting the picophytoplankton‐dominated communities in the iron‐limited, high nutrient‐low chlorophyll SAW. Austral spring chlorophyll blooms in surface STW were near synchronous with elevated fluxes of bio‐siliceous, carbonate, and organic carbon‐rich materials to the deep ocean, probably facilitated by diatom and/or coccolithophorid sedimentation. Lithogenic fluxes were also high in STW, compared to SAW, reflecting proximity to the New Zealand landmass. In contrast, the highest biogenic fluxes in SAW occurred in spring when surface chlorophyll concentrations were low, while highest annual chlorophyll concentrations were in summer with no associated flux increase. We hypothesize that the high spring export in SAW results from subsurface chlorophyll accumulation that is not evident from remote‐sensing satellites. This material was also rich in biogenic silica, perhaps related to the preferential export of diatoms and other silica‐producing organisms, such as silicoflagellates and radiolarians. Organic carbon fluxes in STW are similar to that of other mesotrophic to oligotrophic waters (∼6–7 mg C m−2 d−1), whereas export from SAW is below the global average (∼3 mg C m−2 d−1). Regional differences in flux across the SW Pacific and Tasman region reflect variations in physical processes and ecosystem structure and function.

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Geographic variations in the relationship between silicic acid and nitrate in the South Pacific Ocean

Cited by 57 publications

References 17 publications

Nitrate and silicic acid in the world ocean: patterns and processes

Nitrate and silicic acid in the world ocean: patterns and processes

The Southern Ocean Iron RElease Experiment (SOIREE)—introduction and summary

Annual cycles of deep‐ocean biogeochemical export fluxes in subtropical and subantarctic waters, southwest Pacific Ocean

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