Trace metals distributions in coastal sea ice of Terra Nova Bay, Ross Sea, Antarctica

Grotti, Marco; Soggia, Francesco; Ianni, Carmela; Frache, Roberto

doi:10.1017/s0954102005002695

Cited by 94 publications

(97 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…6c). These results suggest that there are potential differences in iron availability and supply within different zones of the Southern Ocean, which agrees with previous studies which postulated that the bloom extent and duration within the SAZ could potentially be driven by enhanced iron supply through storm-eddy interaction (Nicholson et al, 2016) while in the MIZ addition iron is supplied through melting ice (Gao et al, 2003;Grotti et al, 2005;Sedwick and DiTullio, 1997). The Fe addition test performed here demonstrates the sensitivity of waters south of 50 • S to Fe availability.…”

Section: Discussionsupporting

confidence: 90%

Modelled estimates of spatial variability of iron stress in the Atlantic sector of the Southern Ocean

Ryan‐Keogh

Thomalla²,

Mtshali³

et al. 2017

Biogeosciences

View full text Add to dashboard Cite

Abstract. The Atlantic sector of the Southern Ocean is characterized by markedly different frontal zones with specific seasonal and sub-seasonal dynamics. Demonstrated here is the effect of iron on the potential maximum productivity rates of the phytoplankton community. A series of iron addition productivity versus irradiance (PE) experiments utilizing a unique experimental design that allowed for 24 h incubations were performed within the austral summer of 2015/16 to determine the photosynthetic parameters α B , P B max and E k . Mean values for each photosynthetic parameter under iron-replete conditions were 1.46 ± 0.55 (µg (µg Chl a) −1 h −1 (µM photons m −2 s −1 ) −1 ) for α B , 72.55 ± 27.97 (µg (µg Chl a) −1 h −1 ) for P B max and 50.84 ± 11.89 (µM photons m −2 s −1 ) for E k , whereas mean values under the control conditions were 1.25 ± 0.92 (µg (µg Chl a) −1 h −1 (µM photons m −2 s −1 ) −1 ) for α B , 62.44 ± 36.96 (µg (µg Chl a) −1 h −1 ) for P B max and 55.81 ± 19.60 (µM photons m −2 s −1 ) for E k . There were no clear spatial patterns in either the absolute values or the absolute differences between the treatments at the experimental locations. When these parameters are integrated into a standard depth-integrated primary production model across a latitudinal transect, the effect of iron addition shows higher levels of primary production south of 50 • S, with very little difference observed in the subantarctic and polar frontal zone. These results emphasize the need for better parameterization of photosynthetic parameters in biogeochemical models around sensitivities in their response to iron supply. Future biogeochemical models will need to consider the combined and individual effects of iron and light to better resolve the natural background in primary production and predict its response under a changing climate.

show abstract

Section: Discussionsupporting

confidence: 90%

Modelled estimates of spatial variability of iron stress in the Atlantic sector of the Southern Ocean

Ryan‐Keogh

Thomalla²,

Mtshali³

et al. 2017

Biogeosciences

View full text Add to dashboard Cite

show abstract

“…As expected however, these open ocean ∫ρN rates are up to 60 % lower than those observed during bloom conditions in the Seasonal Ice Zone (SIZ) of the Bellinghausen Sea (18.0 ± 11.9 mmol m −2 d −1 ) (Table 3). Lower open ocean ∫ρN rates compared to the SIZ can be ascribed to the lack of dissolved iron inputs from melting ice (Sedwick and DiTullio, 1997;Gao et al, 2003;Grotti et al, 2005) and a less favourable light environment through deep mixed layer depths (93.9 ± 14.7 m) (Smith and Nelson, 1986). Although there is a slight increase in production and f -ratios in the AZ, relative to the PFZ, the ice free regions of this sector appear to have a relatively low potential for carbon export particularly in the late summer season due predominantly to Fe limitation.…”

Section: The Antarctic Zonementioning

confidence: 99%

Nitrogen uptake by phytoplankton in the Atlantic sector of the Southern Ocean during late austral summer

et al. 2011

View full text Add to dashboard Cite

Abstract. As part of the Bonus-GoodHope (BGH) campaign, 15 N-labelled nitrate, ammonium and urea uptake measurements were made along the BGH transect from Cape Town to ∼60 • S in late austral summer, 2008. Our results are categorised according to distinct hydrographic regions defined by oceanic fronts and open ocean zones. High regenerated nitrate uptake rate in the oligotrophic Subtropical Zone (STZ) resulted in low f -ratios (f = 0.2) with nitrogen uptake being dominated by ρurea, which contributed up to 70 % of total nitrogen uptake. Size fractionated chlorophyll data showed that the greatest contribution (>50 %) of picophytoplankton (<2 µm) were found in the STZ, consistent with a community based on regenerated production. The Subantarctic Zone (SAZ) showed the greatest total integrated nitrogen uptake (10.3 mmol m −2 d −1 ), mainly due to enhanced nutrient supply within an anticyclonic eddy observed in this region. A decrease in the contribution of smaller size classes to the phytoplankton community was observed with increasing latitude, concurrent with a decrease in the contribution of regenerated production. Higher f -ratios observed in the SAZ (f = 0.49), Polar Frontal Zone (f = 0.41) and Antarctic Zone (f = 0.45) relative to the STZ (f = 0.24), indicate a higher contribution of NO − 3 -uptake relative to total nitrogen and potentially higher export production. High ambient regenerated nutrient concentrations are indicative of active regeneration processes throughout the transect and ascribed to late summer season sampling. Higher depth integratedCorrespondence to: W. R. Joubert (wjoubert@csir.co.za) uptake rates also correspond with higher surface iron concentrations. No clear correlation was observed between carbon export estimates derived from new production and 234 Th flux. In addition, export derived from 15 N estimates were 2-20 times greater than those based on 234 Th flux. Variability in the magnitude of export is likely due to intrinsically different methods, compounded by differences in integration time scales for the two proxies of carbon export.

show abstract

“…Small amounts of seawater can be trapped in the advancing ice interface, entraining some impurities, but most of the seawater is rejected at the ice-seawater interface. However, Antarctic field studies have shown Fe and organic matter enrichment of 1 to 2 orders of magnitude over seawater (Grotti et al, 2005;Lannuzel et al, 2007Lannuzel et al, , 2008Lannuzel et al, , 2014aLannuzel et al, , 2014bvan der Merwe et al, 2009van der Merwe et al, , 2011avan der Merwe et al, , 2011b; de Jong et al,…”

Section: Introductionmentioning

confidence: 99%

Incorporation of iron and organic matter into young Antarctic sea ice during its initial growth stages

Janssens

Meiners

Tison

et al. 2016

Elementa: Science of the Anthropocene

View full text Add to dashboard Cite

This study reports concentrations of iron (Fe) and organic matter in young Antarctic pack ice and during its initial growth stages in situ. Although the importance of sea ice as an Fe reservoir for oceanic waters of the Southern Ocean has been clearly established, the processes leading to the enrichment of Fe in sea ice have yet to be investigated and quantified. We conducted two in situ sea-ice growth experiments during a winter cruise in the Weddell Sea. Our aim was to improve the understanding of the processes responsible for the accumulation of dissolved Fe (DFe) and particulate Fe (PFe) in sea ice, and of particulate organic carbon and nitrogen, dissolved organic carbon, extracellular polymeric substances, inorganic macro-nutrients (silicic acid, nitrate and nitrite, phosphate and ammonium), chlorophyll a and bacteria. Enrichment indices, calculated for natural young ice and ice newly formed in situ, indicate that during Antarctic winter all of the measured forms of particulate matter were enriched in sea ice compared to underlying seawater, and that enrichment started from the initial stages of sea-ice formation. Some dissolved material (DFe and ammonium) was also enriched in the ice but at lower enrichment indices than the particulate phase, suggesting that size is a key factor for the incorporation of impurities in sea ice. Low chlorophyll a concentrations and the fit of the macro-nutrients (with the exception of ammonium) with their theoretical dilution lines indicated low biological activity in the ice. From these and additional results we conclude that physical processes are the dominant mechanisms leading to the enrichment of DFe, PFe, organic matter and bacteria in young sea ice, and that PFe and DFe are decoupled during sea-ice formation. Our study thus provides unique quantitative insight into the initial incorporation of impurities, in particular DFe and PFe, into Antarctic sea ice.

show abstract

Trace metals distributions in coastal sea ice of Terra Nova Bay, Ross Sea, Antarctica

Cited by 94 publications

References 29 publications

Modelled estimates of spatial variability of iron stress in the Atlantic sector of the Southern Ocean

Modelled estimates of spatial variability of iron stress in the Atlantic sector of the Southern Ocean

Nitrogen uptake by phytoplankton in the Atlantic sector of the Southern Ocean during late austral summer

Incorporation of iron and organic matter into young Antarctic sea ice during its initial growth stages

Contact Info

Product

Resources

About