Fronts, water masses and heat content variability in the Western Indian sector of the Southern Ocean during austral summer 2004

Winter distributions of dissolved cadmium (dCd) and particulate cadmium (pCd) were measured for the first time in the Indian sector of the Southern Ocean thereby contributing a unique spatial and seasonal dataset. Seven depth profiles, between 41°S and 58°S, were collected along the 30°E longitude during the 2017 austral winter to investigate the biogeochemical cycling of cadmium during a period characterized by contrasting upper water column dynamics compared to summer. Our results support an important role for biological uptake during winter months albeit weaker compared to summer. Distinct, biologically driven changes in cadmium cycling across the transect were observed. For example, surface ratios of pCd to phosphorus (P; pCd:P) increased from 0.37 to 1.07 mmol mol–1 between the subtropical zone (STZ) and the Antarctic zone (AAZ) reflecting increased Cd requirements for diatoms at higher latitudes which, in turn, was driven by a complex relationship between the availability of dCd and dissolved iron (dFe), zinc (dZn) and manganese (dMn). Vertical profiles of pCd:P displayed near-surface maxima consistent with (1) P occurring in two phases with different labilities and the lability of Cd being somewhere in-between and (2) increasing dCd to phosphate (PO4; dCd:PO4) ratios with depth at each station. North of the Antarctic Polar Front (APF), a secondary, deeper pCd:P maximum may reflect an advective signal associated with northward subducting Antarctic Intermediate Water (AAIW). The strong southward increase in surface dCd and dCd:PO4, from approximately 10–700 pmol kg–1 and 40–400 μmol mol–1, respectively, reflected the net effect of preferential uptake and regeneration of diatoms with high Cd content and the upwelling of Cd enriched water masses in the AAZ. Furthermore, distinct dCd versus PO4 relationships were observed in each of the intermediate and deep water masses suggesting that dCd and PO4 distributions at depth are largely the result of physical water mass mixing.

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SEA SURFACE pCO2IN THE INDIAN SECTOR OF THE SOUTHERN OCEAN DURING AUSTRAL SUMMER OF 2009

Advances in Geosciences ◽

10.1142/9789814405683_0007 ◽

2012 ◽

pp. 79-92

Author(s):

SUHAS SHETYE ◽

MARUTHADU SUDHAKAR ◽

RENGASWAMY RAMESH ◽

RAHUL MOHAN ◽

SHRAMIK PATIL ◽

...

Keyword(s):

Southern Ocean ◽

Austral Summer ◽

Sea Surface ◽

Indian Sector

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Variability in primary productivity and bio-optical properties in the Indian sector of the Southern Ocean during an austral summer

Polar Biology ◽

10.1007/s00300-020-02722-2 ◽

2020 ◽

Vol 43 (10) ◽

pp. 1469-1492

Author(s):

Anvita U. Kerkar ◽

S. C. Tripathy ◽

P. Minu ◽

N. Baranval ◽

P. Sabu ◽

...

Keyword(s):

Optical Properties ◽

Southern Ocean ◽

Primary Productivity ◽

Austral Summer ◽

Indian Sector

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Variations of net primary productivity and phytoplankton community composition in the Indian sector of the Southern Ocean as estimated from ocean color remote sensing data

Biogeosciences ◽

10.5194/bg-9-3875-2012 ◽

2012 ◽

Vol 9 (10) ◽

pp. 3875-3890 ◽

Cited By ~ 13

Author(s):

S. Takao ◽

T. Hirawake ◽

S. W. Wright ◽

K. Suzuki

Keyword(s):

Southern Ocean ◽

Community Composition ◽

Primary Productivity ◽

Phytoplankton Community ◽

Net Primary Productivity ◽

Austral Summer ◽

Remote Sensing Data ◽

The Past ◽

Phytoplankton Community Composition ◽

Indian Sector

Abstract. Phytoplankton population dynamics play an important role in biogeochemical cycles in the Southern Ocean during austral summer. Recent environmental changes such as a rise in sea surface temperature (SST) are likely to impact on net primary productivity (NPP) and phytoplankton community composition. However, their spatiotemporal relationships are still unclear in the Southern Ocean. Here we assessed the relationships between NPP, dominant phytoplankton groups, and SST in the Indian sector of the Southern Ocean over the past decade (1997–2007) using satellite remote sensing data. As a result, we found a statistically significant reduction in NPP in the polar frontal zone over the past decade during austral summer. Moreover, the decrease in NPP positively correlated with the dominance of diatoms (Kendall's rank correlation τ = 0.60) estimated by a phytoplankton community composition model, but not correlated with SST. In the seasonal ice zone, NPP correlated with not only the dominance of diatoms positively (τ = 0.56), but also the dominance of haptophytes (τ = −0.54) and SST (τ = −0.54) negatively. Our results suggested that summer NPP values were strongly affected by the phytoplankton community composition in the Indian sector of the Southern Ocean.

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