Limitation of algal growth by iron deficiency in the Australian Subantarctic Region

Sedwick, Peter N.; DiTullio, Giacomo R.; Hutchins, David A.; Boyd, Philip W.; Griffiths, F. Brian; Crossley, A.; Trull, Thomas W.; Quéguiner, Bernard

doi:10.1029/1998gl002284

Cited by 112 publications

(87 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These include Ekman transport of upper circumpolar water that has been upwelled south of the Polar Front, lateral and vertical mixing of Fe derived from Australia's continental shelves, and atmospheric deposition (Meskhidze et al, 2007;Cassar et al, 2007;Gabric et al, 2002;Sedwick et al, 1999). Here, we compare soluble iron deposition fluxes to NCP measurements.…”

Section: Ncp Vs Aeolian Fe Deposition Estimatesmentioning

confidence: 99%

The influence of iron and light on net community production in the Subantarctic and Polar Frontal Zones

et al. 2011

View full text Add to dashboard Cite

The roles of iron and light in controlling biomass and primary productivity are clearly established in the Southern Ocean. However, their influence on net community production (NCP) and carbon export remains to be quantified. To improve our understanding of NCP and carbon export production in the Subantarctic Zone (SAZ) and the northern reaches of the Polar Frontal Zone (PFZ), we conducted continuous onboard determinations of NCP as part of the Sub-Antarctic Sensitivity to Environmental Change (SAZ-Sense) study, which occurred in January–February 2007. Biological O2 supersaturation was derived from measuring O2/Ar ratios by equilibrator inlet mass spectrometry. Based on these continuous measurements, NCP during the austral summer 2007 in the Australian SAZ was approximately 43 mmol O2 m−2 d−1. NCP showed significant spatial variability, with larger values near the Subtropical front, and a general southward decrease. For shallower mixed layers (<50 m), dissolved Fe concentrations and Fe sufficiency, estimated from variable fluorescence, correlated strongly with NCP. The strong correlation between NCP and dissolved Fe may be difficult to interpret because of the correlation of dissolved Fe to MLD and because the concentration of iron may not be a good indicator of its availability. At stations with deeper mixed layers, NCP was consistently low, regardless of iron sufficiency, consistent with light availability also being an important control of NCP. Our new observations provide independent evidence for the critical roles of iron and light in mediating carbon export from the Southern Ocean mixed layer

show abstract

Section: Ncp Vs Aeolian Fe Deposition Estimatesmentioning

confidence: 99%

The influence of iron and light on net community production in the Subantarctic and Polar Frontal Zones

et al. 2011

View full text Add to dashboard Cite

show abstract

“…Site P1 is representative of a large proportion of the circumpolar SAZ, in terms of exhibiting iron limitation, seasonally low silicate levels, non-limiting nitrate and phosphate levels, low to moderate biomass throughout much of the year, and a mixed phytoplankton community that includes cyanobacteria, coccolithophores, small diatoms, and flagellates (Sedwick et al, 1999(Sedwick et al, , 2008Trull et al, 2001b;Rintoul and Trull, 2001;Wang et al, 2003). Site P2 is also representative of circumpolar conditions for the PFZ.…”

Section: Study Areamentioning

confidence: 99%

Controls on mesopelagic particle fluxes in the Sub-Antarctic and Polar Frontal Zones in the Southern Ocean south of Australia in summer—Perspectives from free-drifting sediment traps

Ebersbach

Trull

Davies

et al. 2011

Deep Sea Research Part II: Topical Studies in Oceanography

Self Cite

View full text Add to dashboard Cite

a b s t r a c tThe SAZ-Sense project examined ecosystem controls on Southern Ocean carbon export during austral summer (January-February 2007) at three locations: P1 in the low biomass Subantarctic Zone (SAZ) west of Tasmania, P3 in a region of elevated biomass in the SAZ east of Tasmania fuelled by enhanced iron supply, and P2 in High-Nutrient/Low Chlorophyll (HNLC) Polar Frontal Zone (PFZ) waters south of P1 and P3. Sinking particles were collected using (i) a cylindrical time-series (PPS3/3) trap for bulk geochemical fluxes, (ii) indented rotating sphere (IRS) traps operated as in-situ settling columns to determine the flux distribution across sinking-rate fractions, and (iii) cylindrical traps filled with polyacrylamide gels to obtain intact particles for image analysis.Particulate organic carbon (POC) flux at 150 m (PPS3/3 trap) was highest at P1, lower at P2, and lowest at P3 (3.3 71.8, 2.1 7 0.9, and 0.9 70.4 mmol m À 2 d À 1 , respectively). Biogenic silica (BSi) flux was very low in the SAZ (0.2 7 0.2 and 0.02 7 0.005 mmol m À 2 d À 1 at P1 and P3, respectively) and much higher in the PFZ (2.3 7 0.5 mmol m À 2 d À 1 at P2). Hence, the high biomass site P3 did not exhibit a correspondingly high flux of either POC or BSi. Separation of sinking-rate fractions with the IRS traps (at 170 and 320 m depth) was only successful at the PFZ site P2, where a relatively uniform distribution of flux was observed with $ 1/3 of the POC sinking faster than 100 m d À 1 and 1/3 sinking slower than 10 m d À 1 .Analysis of thousands of particles collected with the gel traps (at 140, 190, 240, and 290 m depth) enabled us to identify 5 different categories: fluff-aggregates (low-density porous or amorphous aggregates), faecal-aggregates (denser aggregates composed of different types of particles), cylindrical and ovoid faecal pellets, and isolated phyto-cells (chains and single cells). Faecal-aggregates dominated the flux at all sites, and were larger in size at P1 in comparison to P3. The PFZ site P2 differed strongly from both SAZ sites in having a much higher abundance of diatoms and relatively small-sized faecalaggregates. Overall, the particle images suggest that grazing was an important influence on vertical export at all three sites, with differences in the extents of large aggregate formation and direct diatom export further influencing the differences among the sites.

show abstract

“…The Southern Ocean is thus the largest of the High-Nitrate, LowChlorophyll (HNLC) regions (Martin, 1990). In recent years, substantial evidence has accumulated that the limited availability of the micronutrient iron limits growth rates, and in conjunction with loss processes maintains chlorophyll concentrations (and phytoplankton biomass) at relatively low levels within the Southern Ocean (Martin et al, 1990a,b;Helbling et al, 1991;de Baar et al, 1995;Van Leeuwe et al, 1997;Sedwick et al, 1997Sedwick et al, , 1999Takeda, 1998;Boyd et al, 1999Boyd et al, , 2000Boyd et al, , 2001Hutchins et al, 2001). Strong grazing pressure, light limitation, and silicon limitation of diatom growth have also been suggested to limit biomass accumulation in this region (Banse, 1996;Mitchell et al, 1991;Nelson and Smith, 1991;Boyd et al, 1999Boyd et al, , 2001Frank et al, 2000;Brown and Landry, 2001;Nelson et al, 2001;Hutchins et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

Surface chlorophyll concentrations in relation to the Antarctic Polar Front: seasonal and spatial patterns from satellite observations

Moore

Abbott

2002

Journal of Marine Systems

150

118

View full text Add to dashboard Cite

Satellite ocean color data from the Sea Viewing Wide Field of View Sensor (SeaWiFS) are used to investigate phytoplankton bloom dynamics at the Antarctic Polar Front (PF). Satellite sea surface temperature (SST) data are used to map the location of the PF at weekly timescales. Elevated chlorophyll within the PF often appears as a narrow band that occupies only a portion of the SST gradient across the PF. Phytoplankton blooms within the PF occur most frequently during the month of December and are unevenly distributed within the Southern Ocean. Elevated chlorophyll concentrations at the PF are most frequently observed where the current is interacting with large topographic features.Mesoscale physical processes, including meander-induced upwelling and increased eddy mixing, where the PF encounters large topographic features likely leads to increased nutrient flux to surface waters in these regions. The highest mean chlorophyll values associated with the PF occur where the front comes into contact with relatively shallow waters along the North Scotia Ridge and at Kerguelen Plateau. Iron input from sedimentary sources likely plays an important role in these regions.Over seasonal timescales it appears likely that light-limitation prevents phytoplankton blooms at the PF during winter and spring months. PF blooms are observed most commonly during December when surface radiation peaks and mixed layer depths are rapidly shoaling. Even during December, when the light regime would seem to be favorable, PF blooms are largely restricted to regions where enhanced nutrient fluxes to surface waters due to frontal dynamics are likely. During late summer, nutrient limitation due to depletion of iron and possibly silicate largely prevent blooms at the PF. In the fall, deepening mixed layers would provide some relief from nutrient limitation but likely lead again to light-limitation of growth rates and the prevention of blooms. D

show abstract

Limitation of algal growth by iron deficiency in the Australian Subantarctic Region

Cited by 112 publications

References 20 publications

The influence of iron and light on net community production in the Subantarctic and Polar Frontal Zones

The influence of iron and light on net community production in the Subantarctic and Polar Frontal Zones

Controls on mesopelagic particle fluxes in the Sub-Antarctic and Polar Frontal Zones in the Southern Ocean south of Australia in summer—Perspectives from free-drifting sediment traps

Surface chlorophyll concentrations in relation to the Antarctic Polar Front: seasonal and spatial patterns from satellite observations

Contact Info

Product

Resources

About