Effects of iron limitation on intracellular cadmium of cultured phytoplankton: Implications for surface dissolved cadmium to phosphate ratios

Dissolved cadmium in the Southern Ocean: Distribution, speciation, and relation to phosphate

“…This points to high Cd : P and Zn : P ratios in P. antarctica, which could be associated with a previously reported higher cellular N : P ratio than that of diatoms (Arrigo et al 1999;Croot et al 2011). Contrastingly, Lane et al (2009) reported relatively low Cd : P ratios in a P. antarctica isolate compared to the diatoms Thalassiosira pseudonana and T. oceanica. The authors estimated the Cd : P ratio from Cd : C and C : P ratios using a common Redfield ratio for all phytoplankton (C : P 5 106).…”

“…Notably, under Fe limitation such as in the HNLC waters of the Southern Ocean, cellular Cd : P ratios are known to increase significantly (Cullen et al 2003;Lane et al 2009). This may be by slow growth rates or by uptake of Cd with nonspecific divalent metal transporters that may be upregulated under Fe limitation (Cullen 2006;Lane et al 2009). Hence, higher Cd : P uptake ratios and low Cd* are expected in Fe-limited surface waters, providing a mechanistic link for a covariation of Cd* and Fe (see Fig.…”

“…However, it has previously been shown that P. antarctica in the Ross Sea have significantly higher C : P ratios (C : P 5 120-154; Arrigo et al 2002), whereas diatoms have lower C : P ratios (C : P 5 76.2). Considering an additional strong increase in Cd : P uptake ratios at limiting Fe (Lane et al 2009) and potentially Mn concentrations for P. antarctica, it is possible that the high Cd* values at B7 in depths between 75-300 m were related to the decay of a recent P. antarctica bloom.…”

Adaptive strategies by Southern Ocean phytoplankton to lessen iron limitation: Uptake of organically complexed iron and reduced cellular iron requirements

“…The largest species, P. inermis, has the lowest Fe : C ratios ever reported (0.4 mmol : mol for cells growing at m : m max 5 0.6), although several other oceanic diatom species from the equatorial Pacific and N. Atlantic also have Fe : C ratios , 1 mmol : mol (Maldonado and Price 1996). It is reassuring that comparably low Fe : C ratios for P. inermis were found in independent experiments performed under comparable experimental conditions by Lane et al (2009;0.7 The mean Fe : C ratio for Fe-limited Southern Ocean species in our study was 1.7 6 1.3 mmol : mol, which agrees favorably with the mean Southern Ocean ratio of 1.8 6 0.4 mmol : mol (n 5 2) calculated by Sunda (1997) from regressions of dissolved Fe vs. apparent oxygen utilization. The author predicted that this Fe : C ratio could support a specific growth rate of 0.48 6 0.1 d 21 for T. oceanica at 20uC, using the empirically derived relationship: m (d 21 ) 5 0.268 3 Fe : C (mmol mol 21 ).…”

A seasonal study of dissolved cobalt in the Ross Sea, Antarctica: micronutrient behavior, absence of scavenging, and relationships with Zn, Cd, and P

“…Based on the extent to which this biochemical circulation modifies the composition of seawater, the slope of the dissolved nutrient to phosphate relationship can reflect the aggregate stoichiometry of biological processes. For example, Redfield et al (1963) observed similarities between the ratios of seawater NO distributions and the elemental N:P composition of marine plankton (Redfield et al, 1963), and more recently the cellular metal contents of phytoplankton have been compared with trace metal abundances in seawater (e.g., Huntsman, 1995, 2000;Fitzwater et al, 2000;Ho et al, 2003;Saito et al, 2004;Noble et al, 2008;Lane et al, 2009). This characterization of elemental stoichiometries in nature has been termed "ecological stoichiometry", defined broadly as "the balance of multiple chemical substances in ecological interactions and processes" (Sterner and Elser, 2002).…”