The influence of global change on Southern Ocean productivity will have major ramifications for future management of polar life. A prior laboratory study investigated the response of a batch‐cultured subantarctic diatom to projected change simulating conditions for 2100 (increased temperature/CO 2 /irradiance/iron; decreased macronutrients), showed a twofold higher chlorophyll‐derived growth rate driven mainly by temperature a...

Manganese (Mn) is an abundant element in the Earth's crust. However, its concentrations in open ocean seawater are low, where external inputs are scarce. In this study, we report the dissolved Mn and particulate Mn distributions in the Southern Ocean, measured along the GEOTRACES—SR3 transect, from Tasmania (Australia) to Antarctica in the Southern Ocean, during the austral summer 2018. Both dissolved Mn and particulate Mn con...

Zinc (Zn) isotope fractionation by the coccolithophore Emiliania huxleyi (a Tasman Sea isolate) was investigated by culturing it across a range of free Zn 2+ ion concentrations (1.2 pmol L −1 to 3.2 nmol L −1 ), which span the natural range observed in the global oceans. Across the range of free Zn 2+ ion concentrations tested, the amount of bio‐available Zn did not have any appreciable influence on the specific growth rate or...

We investigated the effects of iron (Fe) limitation on the elemental stoichiometry, silicic acid (Si(OH) 4 ) uptake kinetics and cell morphology in two Southern Ocean diatoms Eucampia antarctica and Proboscia inermis and the temperate diatom Thalassiosira pseudonana . An increase in Fe‐stress resulted in reductions in specific growth rate and decreases in cellular nitrogen (N) and carbon (C) content relative to cellular biogen...

In laboratory experiments we examined the interplay of light and iron availability on the intracellular iron concentrations, specific growth rates, and photosynthetic physiology of Southern (S.) Ocean diatoms ( Eucampia antarctica and Proboscia inermis ) and the haptophyte Phaeocystis antarctica . Intracellular iron concentrations and iron : carbon (Fe : C) molar ratios increased with decreasing irradiance in temperate coastal...

We report results of laboratory studies examining the effect of low levels of iron (Fe) availability on the intracellular Fe concentrations and specific growth rates in Southern Ocean diatoms ( Fragilariopsis kerguelensis , Eucampia antarctica , Proboscia inermis , and Thalassiosira antarctica ) and Phaeocystis antarctica . All species grew on Fe complexed to the siderophore desferrioxamine B (DFB). Concentrations of DFB up to...

Climate change will alter concurrently many environmental factors that exert control over oceanic phytoplankton. Recent laboratory culture work, shipboard experiments, and field surveys reveal many remaining unknowns about the bottom‐up controls for five globally important algal groups. Increasing uncertainties exist, respectively, for picocyanobacteria, diatoms, Phaeocystis spp., N 2 ‐fixing cyanobacteria, and coccolithophore...

We report the results of laboratory and field studies examining inorganic carbon (C i ) utilization by Southern Ocean phytoplankton. Both in monospecific laboratory cultures of diatoms and Phaeocystis antarctica and in natural assemblages in the Ross Sea, C i uptake by phytoplankton was dominated by direct HCO 3 1 transport. The contribution of HCO 3 1 transport to total C i uptake ranged from 65% to 95%, with an overall avera...

In this study, we show a fundamental difference between diatom species from different marine habitats in their ability to cope with changes in irradiance. Estuarine species show a higher and more flexible capacity for photoprotection than oceanic and coastal species, and when exposed to excess light, the impairment of their photosynthetic capacity because of photoinhibition was reduced. This resulted in maintenance of growth i...

Iron supply is thought to regulate primary production in high nitrate, low chlorophyll (HNLC) regions of the sea in both the past and the present. A critical aspect of this relationship is acquisition of iron (Fe) by phytoplankton, which occurs through a complex series of extracellular reactions that are influenced by Fe chemistry and speciation. During the first in situ mesoscale Fe‐enrichment experiment in the Southern Ocean...