Circumpolar HNLC context
The area south of 40°S is a broad Southern/subantarctic geographic reference, not an HNLC boundary or project area. Seven deliberate Southern Ocean and subantarctic experiments span strong surface responses, 100 m transfer, negligible short-window export and a deep aggregate-sinking event. Light, mixing, silicate, winter ventilation and non-local nutrient effects determine how each record is interpreted.
Regional carbon pathway
Named field studies separate observed responses from unresolved atmospheric removal and durability.
SOIREE: A 13-day diatom-led bloom with no iron-enhanced particle-export signal resolved in the short record.
EisenEx: A three-week eddy study with a larger-diatom bloom and no patch-specific export enhancement distinguished by ²³⁴Th.
SOFeX North: A low-silicate, mixed-assemblage response with float-observed two- to six-fold carbon transfer through 100 m.
SOFeX South: A high-silicate, diatom-dominated bloom with ²³⁴Th-derived POC flux through 100 m rising by more than 700%.
EIFEX: An eddy-confined diatom bloom with an observed aggregate-sinking event and evidence of transfer below 1,000 m in that setting.
SAGE: A 15.5-day, largely non-diatom response in which mixing offset the estimated biological pCO₂ drawdown.
LOHAFEX: A low-silicate, grazer-influenced response without enhanced fertilisation-induced downward particle flux during the 39-day study.
SOIREE followed an iron–SF₆ patch at 61°S, 140°E for 13 days in a seasonal mixed layer near 65 m; drifting particle traps sampled near 110 m.Evidence: Boyd et al. (2000) · Nodder & Waite (2001)
A tracer-labelled iron treatment patch was tracked alongside surrounding waters through repeated sampling.Evidence: Boyd et al. (2000)
Iron stimulated a marked diatom-led bloom, higher production and lower surface-water pCO₂.Evidence: Boyd et al. (2000)
²³⁴Th measurements did not show an iron-enhanced particle-export signal during the short record.Evidence: Charette & Buesseler (2000)
The short record did not determine delayed export, remineralisation, deep circulation or atmospheric durability.Evidence: Charette & Buesseler (2000) · Buesseler et al. (2024)
Tracer-defined treatment waters, a comparable reference, particle flux, carbonate chemistry and seasonal follow-up separate bloom response from later fate.Evidence: Buesseler et al. (2024)
EisenEx tracked a cyclonic Polar Frontal Zone eddy near 47°S, 21°E through three weeks of variable upper-ocean mixing.Evidence: Gervais et al. (2002)
Repeated iron additions and in-patch/out-patch observations framed the treatment amid eddy and mixed-layer variability.Evidence: Gervais et al. (2002)
Chlorophyll and productivity increased, with larger diatoms becoming more prominent in the induced bloom.Evidence: Gervais et al. (2002)
²³⁴Th observations did not distinguish an in-patch export enhancement from surrounding waters during the campaign.Evidence: EisenEx ²³⁴Th dataset · Buesseler et al. (2004)
The three-week record did not resolve delayed export, mesopelagic attenuation or atmospheric durability.Evidence: Gervais et al. (2002) · Buesseler et al. (2024)
In-patch and out-patch hydrography, ²³⁴Th, POC, carbonate and later-depth observations distinguish biological response from eddy variability.Evidence: EisenEx ²³⁴Th dataset · Buesseler et al. (2004)
SOFeX North followed a low-silicate patch north of the Antarctic Polar Front near 56°S, 172°W for about 40 days.Evidence: Coale et al. (2004)
Iron, SF₆ and ³He tracers defined a low-silicate treatment patch and its surrounding waters.Evidence: Coale et al. (2004)
Biomass and productivity rose in a mixed low-silicate assemblage; later export-associated material included diatoms.Evidence: Coale et al. (2004)
Autonomous floats recorded a two- to six-fold increase in carbon transfer through 100 m as the patch subducted below a front.Evidence: Bishop et al. (2004)
A 100 m transfer observation did not determine transfer below winter mixing, later remineralisation or atmospheric durability.Evidence: Bishop et al. (2004) · Buesseler et al. (2024)
Tracer-defined waters, float profiles, carbonate chemistry and deeper follow-up separate physical subduction from sustained particle transfer.Evidence: Bishop et al. (2004)
SOFeX South followed a high-silicate patch south of the Antarctic Polar Front near 66°S, 172°W for about a month.Evidence: Coale et al. (2004)
Iron, SF₆ and ³He tracers separated a high-silicate treatment patch from surrounding water.Evidence: Coale et al. (2004)
The high-silicate setting supported a diatom-dominated bloom.Evidence: Coale et al. (2004)
²³⁴Th-derived POC flux through 100 m increased by more than 700% during the observation.Evidence: Buesseler et al. (2005)
The 100 m flux did not independently establish persistence below winter mixing, later remineralisation or atmospheric durability.Evidence: Buesseler et al. (2005) · Buesseler et al. (2024)
In-patch and out-patch ²³⁴Th, POC, silica, carbonate and water-mass observations define the measured contrast.Evidence: Buesseler et al. (2005)
EIFEX followed one iron-enriched eddy within the Antarctic Circumpolar Current; fronts and eddy retention defined the observation frame.Evidence: Smetacek et al. (2012)
A tracked treatment eddy and surrounding comparison waters framed the study; the comparison was not a matched pre-treatment control.Evidence: Smetacek et al. (2012)
EIFEX observed an eddy-confined, diatom-dominated bloom that formed large sinking aggregates.Evidence: Smetacek et al. (2012)
Multiple observations indicated aggregate transfer across 100 m and at least half the bloom biomass sinking below 1,000 m in this one-eddy setting.Evidence: Smetacek et al. (2012)
Deep transfer in one eddy did not independently determine air–sea attribution, later circulation or atmospheric durability.Evidence: Smetacek et al. (2012) · Oschlies et al. (2025) · NASEM (2022) · Buesseler et al. (2024)
Eddy tracking, air–sea exchange, carbonate inventories, deep particles and later circulation describe different parts of an atmospheric account.Evidence: Buesseler et al. (2024)
SAGE followed a Fe–SF₆/³He-labelled subantarctic patch near 46.5°S, 172.5°E for 15.5 days; mixed layers ranged from 50 to 80 m, with a transient restratification shallower than 40 m.Evidence: Harvey et al. (2011) · Stevens et al. (2011)
A tracer-labelled treatment patch and out-patch waters placed biological changes alongside mixing and dilution.Evidence: Harvey et al. (2011)
Chlorophyll and primary productivity roughly doubled near the end through non-diatom activity, without significant particulate organic carbon accumulation.Evidence: Peloquin et al. (2011)
No iron-induced deep-export event was established during the 15.5-day study.Evidence: Peloquin et al. (2011)
Surface pCO₂ rose from 327 to 338 µatm as mixing offset an estimated biological drawdown; this did not establish an iron-caused atmospheric return.Evidence: SAGE carbon-system study
Dual tracers, carbonate chemistry, mixed-layer physics, food-web observations and depth-resolved particles distinguish biological response from dilution and recycling.Evidence: SAGE mixed-layer study
LOHAFEX followed a low-silicate Southern Ocean eddy near 48°S, 15°W for 39 days; mean mixed-layer depth was 66 m.Evidence: Martin et al. (2013)
Tracked treatment and comparison waters separated the fertilised response from eddy transport, mixing and background variability.Evidence: Martin et al. (2013)
Small flagellates and strong grazing dominated; chlorophyll and primary productivity doubled without an EIFEX-like aggregate event.Evidence: Martin et al. (2013)
Net community production increased, but fertilisation-induced downward particle flux did not increase during the 39-day study.Evidence: Martin et al. (2013)
Flux was strongly attenuated across mixed-layer, 100 m and 200–450 m observations; later fate depends on remineralisation, circulation and ventilation.Evidence: Martin et al. (2013) · Buesseler et al. (2024)
Treatment/reference ecology, carbonate chemistry, grazing, particle flux and physical transport distinguish production from atmospheric removal.Evidence: Buesseler et al. (2024)
Diatom blooms characterised SOIREE, EisenEx, SOFeX South and EIFEX. SOFeX North was a mixed low-silicate response; SAGE was largely non-diatom and LOHAFEX small-cell, grazer-influenced.
Deep particle observations do not alone quantify additional atmospheric CO₂ uptake, later re-emission, nutrient displacement or life-cycle emissions.
SOIREE and EisenEx did not resolve fertilisation-enhanced export in their short windows. SOFeX North and South recorded 100 m transfer; EIFEX observed substantial biomass transfer below 1,000 m in one eddy; SAGE and LOHAFEX did not establish induced deep flux.
2–4 GtCO₂ yr⁻¹
Idealised modelling estimate: continuous OIF across the entire Southern Ocean, or at ocean-basin to global scales; centennial timescale.
Oschlies et al. (2025)
Long transit, severe weather windows, deep observing systems, winter follow-up and a large downstream observation corridor.
Route atlas
Study-specific atlas. It is not a regional composition, limitation or removal ledger.
Named patch versus comparison; not a regional baseline.
A floristic shift toward large heavily silicified chain-forming diatoms was reported; no species label is retained.
The record did not resolve fertilisation-enhanced export or later fate.
Eddy-specific comparison; not a regional reference.
Larger diatoms became more prominent in the induced bloom; no exact species or morphometry is retained.
No carrier-specific transfer or later-fate conclusion is retained.
Study-specific north-patch frame.
The low-silicate response remained a mixed assemblage; later export-associated material included diatoms without a species/morphometry claim.
Carrier type, later remineralisation, deep circulation and atmospheric durability remain unresolved.
Study-specific south-patch frame.
A diatom-dominated bloom was observed; no named species or size record is retained.
²³⁴Th-derived POC flux
Derived POC flux through 100 m increased by more than 700%.
The estimate does not identify a carrier or establish permanence.
One-eddy study frame; not a general Southern-Ocean reference.
An eddy-confined diatom-dominated bloom formed large sinking aggregates.
Study-specific physical and biological frame.
Non-diatom activity, chlorophyll and production roughly doubled late; no significant POC accumulation was established.
mixing/recycling with no induced deep-export event
No iron-induced deep-export event was established.
The short record and mixing/recycling context do not resolve later export or atmospheric fate.
Eddy-specific comparison; not an EIFEX reference.
Small flagellates and strong grazing dominated; no EIFEX-like aggregate event occurred.
No induced deep-transfer carrier or atmospheric-removal outcome is established.
| Study / treated guild | Matched reference | Treated response | Morphology / resolution | Source |
|---|---|---|---|---|
| SOIREE · large heavily silicified chain-forming diatoms | Pre-addition taxonomic composition is not resolved in this evidence table at taxon level. Named patch versus comparison; not a regional baseline. | A floristic shift toward large heavily silicified chain-forming diatoms was reported; no species label is retained. | heavily silicified chain-forming diatom. broad morphology · No named species or dimension is specified. Morphology schematic · not to scale | Boyd et al. (2000) ↗ · Nodder & Waite (2001) ↗ · Charette & Buesseler (2000) ↗ |
| EisenEx · larger diatoms | Baseline taxonomic composition is not resolved in the cited source. Eddy-specific comparison; not a regional reference. | Larger diatoms became more prominent in the induced bloom; no exact species or morphometry is retained. | larger-diatom outline. broad schematic · No species or dimensions are specified. Morphology schematic · not to scale | Gervais et al. (2002) ↗ · EisenEx ²³⁴Th dataset ↗ |
| SOFeX North · mixed low-silicate assemblage | Low-silicate mixed assemblage; taxonomic composition is not resolved in the cited source. Study-specific north-patch frame. | The low-silicate response remained a mixed assemblage; later export-associated material included diatoms without a species/morphometry claim. | mixed assemblage field. unresolved taxonomic morphology · No generic pennate morphology is assigned. Morphology schematic · not to scale | Coale et al. (2004) ↗ · Bishop et al. (2004) ↗ |
| SOFeX North · diatom material in later export-associated observations | Low-silicate mixed assemblage; taxonomic composition is not resolved in the cited source. Study-specific north-patch frame. | The low-silicate response remained a mixed assemblage; later export-associated material included diatoms without a species/morphometry claim. | No additional morphology schematic. broad material label | Coale et al. (2004) ↗ · Bishop et al. (2004) ↗ |
| SOFeX South · diatom-dominated bloom | High-silicate setting; a pre-addition taxon table is not retained. Study-specific south-patch frame. | A diatom-dominated bloom was observed; no named species or size record is retained. | diatom chain. broad schematic · No taxon, carrier or permanence claim is assigned. Morphology schematic · not to scale | Coale et al. (2004) ↗ · Buesseler et al. (2005) ↗ |
| EIFEX · diatom-dominated bloom | Eddy-specific baseline taxonomic composition and micronutrient measurements are not reported in the cited sources. One-eddy study frame; not a general Southern-Ocean reference. | An eddy-confined diatom-dominated bloom formed large sinking aggregates. | No additional morphology schematic. broad guild | Smetacek et al. (2012) ↗ · Berg et al. (2011) ↗ |
| EIFEX · large diatom aggregates | Eddy-specific baseline taxonomic composition and micronutrient measurements are not reported in the cited sources. One-eddy study frame; not a general Southern-Ocean reference. | An eddy-confined diatom-dominated bloom formed large sinking aggregates. | irregular porous diatom-fragment aggregate. particle morphology · Aggregate form is study-specific to the tracked eddy. Morphology schematic · not to scale | Smetacek et al. (2012) ↗ · Berg et al. (2011) ↗ |
| SAGE · non-diatom activity | Baseline taxonomic composition is not resolved in this evidence table. Study-specific physical and biological frame. | Non-diatom activity, chlorophyll and production roughly doubled late; no significant POC accumulation was established. | small non-diatom cell field. broad schematic · No diatom morphology or taxon is assigned. Morphology schematic · not to scale | Harvey et al. (2011) ↗ · Peloquin et al. (2011) ↗ · SAGE carbon-system study ↗ |
| LOHAFEX · small flagellates | Low-silicate setting; baseline taxon/metals table is not resolved in this evidence table. Eddy-specific comparison; not an EIFEX reference. | Small flagellates and strong grazing dominated; no EIFEX-like aggregate event occurred. | small flagellate field. broad schematic · Strong grazing is a food-web control, not a cell morphology. Morphology schematic · not to scale | Martin et al. (2013) ↗ |
| Study | Record | Analyte | Method / fraction / depth | Date / value | Status | Limit / context | Source |
|---|---|---|---|---|---|---|---|
| SOIREE | Treatment input / patch | dissolved Fe | — | — None dissolved Fe four infusions over seven days | Observed | Treatment elevation 1–2 nM above ambient <0.1 nM during four FeSO4 infusions over seven days in an SF6-traced patch; not a regional baseline. | Boyd et al. (2000) ↗ |
| SOIREE | Regional transect context | Nutrients and trace metals | — | — — | Local baseline required | No Southern regional numeric context is carried into the v16 public model. | — |
| SOIREE | Regional transect context | Mn, Zn, Co, Cu, Ni, Cd and B12 | — | — — | Not measured in cited study | Not measured in the cited study; no value is implied. | Boyd et al. (2000) ↗ |
| SOIREE | Cellular function | Fe and silicic acid | — | — — | Context only | Fe supports photosynthetic/electron-transfer and nitrogen-assimilation machinery; silicic acid forms diatom frustules. This is physiological context, not a demonstrated limitation or species-specific stoichiometry. | — |
| SOIREE | Cellular function | Mn, Zn, Co, Cu, Ni, Cd and B12 | — | — — | Not reported | No route-specific cellular-function, stoichiometry or limitation claim is retained. | — |
| EisenEx | Treatment input / patch | Fe | — | — — | Local baseline required | No compatible ambient or public numeric treatment row is retained. | Gervais et al. (2002) ↗ |
| EisenEx | Regional transect context | Nutrients and trace metals | — | — — | Local baseline required | No Southern regional numeric context is carried into the v16 public model. | — |
| EisenEx | Regional transect context | Mn, Zn, Co, Cu, Ni, Cd and B12 | — | — — | Not measured in cited study | Not measured in the cited study; no value is implied. | Gervais et al. (2002) ↗ |
| EisenEx | Cellular function | Fe and silicic acid | — | — — | Context only | Fe supports photosynthetic/electron-transfer and nitrogen-assimilation machinery; silicic acid forms diatom frustules. This is physiological context, not a demonstrated limitation or species-specific stoichiometry. | — |
| EisenEx | Cellular function | Mn, Zn, Co, Cu, Ni, Cd and B12 | — | — — | Not reported | No route-specific cellular-function, stoichiometry or limitation claim is retained. | — |
| SOFeX North | Treatment input / patch | Fe, SF6 and ³He | — | — — | Observed | Tracers defined treatment and comparison waters; no public ambient numeric row is retained. | Coale et al. (2004) ↗ |
| SOFeX North | Regional transect context | Nutrients and trace metals | — | — — | Local baseline required | No Southern regional numeric context is carried into the v16 public model. | — |
| SOFeX North | Regional transect context | Mn, Zn, Co, Cu, Ni, Cd and B12 | — | — — | Not measured in cited study | Not measured in the cited study; no value is implied. | Coale et al. (2004) ↗ · Bishop et al. (2004) ↗ |
| SOFeX North | Cellular function | Fe and silicic acid | — | — — | Context only | Fe supports photosynthetic/electron-transfer and nitrogen-assimilation machinery; silicic acid forms diatom frustules. This is physiological context, not a demonstrated limitation or species-specific stoichiometry. | — |
| SOFeX North | Cellular function | Mn, Zn, Co, Cu, Ni, Cd and B12 | — | — — | Not reported | No route-specific cellular-function, stoichiometry or limitation claim is retained. | — |
| SOFeX South | Treatment input / patch | Fe, SF6 and ³He | — | — — | Observed | Tracers defined treatment and comparison waters; no public ambient numeric row is retained. | Coale et al. (2004) ↗ |
| SOFeX South | Regional transect context | Nutrients and trace metals | — | — — | Local baseline required | No Southern regional numeric context is carried into the v16 public model. | — |
| SOFeX South | Regional transect context | Mn, Zn, Co, Cu, Ni, Cd and B12 | — | — — | Not measured in cited study | Not measured in the cited study; no value is implied. | Coale et al. (2004) ↗ · Buesseler et al. (2005) ↗ |
| SOFeX South | Cellular function | Fe and silicic acid | — | — — | Context only | Fe supports photosynthetic/electron-transfer and nitrogen-assimilation machinery; silicic acid forms diatom frustules. This is physiological context, not a demonstrated limitation or species-specific stoichiometry. | — |
| SOFeX South | Cellular function | Mn, Zn, Co, Cu, Ni, Cd and B12 | — | — — | Not reported | No route-specific cellular-function, stoichiometry or limitation claim is retained. | — |
| EIFEX | Treatment input / patch | FeSO4·7H2O | — | — 7000 kg FeSO4·7H2O day 1 · 7000 kg FeSO4·7H2O day 14 | Observed | 7,000 kg added on day 1 and another 7,000 kg on day 14 in the tracked eddy; added material, not ambient dissolved Fe. | Berg et al. (2011) ↗ |
| EIFEX | Regional transect context | Nutrients and trace metals | — | — — | Local baseline required | No Southern regional numeric context is carried into the v16 public model. | — |
| EIFEX | Regional transect context | Mn, Zn, Co, Cu, Ni, Cd and B12 | — | — — | Not measured in cited study | Not measured in the cited study; no value is implied. | Smetacek et al. (2012) ↗ · Berg et al. (2011) ↗ |
| EIFEX | Cellular function | Fe and silicic acid | — | — — | Context only | Fe supports photosynthetic/electron-transfer and nitrogen-assimilation machinery; silicic acid forms diatom frustules. This is physiological context, not a demonstrated limitation or species-specific stoichiometry. | — |
| EIFEX | Cellular function | Mn, Zn, Co, Cu, Ni, Cd and B12 | — | — — | Not reported | No route-specific cellular-function, stoichiometry or limitation claim is retained. | — |
| SAGE | Treatment input / patch | Fe, SF6 and ³He | — | — — | Observed | The labelled patch defined the treatment frame; no public ambient numeric row is retained. | Harvey et al. (2011) ↗ |
| SAGE | Regional transect context | Nutrients and trace metals | — | — — | Local baseline required | No Southern regional numeric context is carried into the v16 public model. | — |
| SAGE | Regional transect context | Mn, Zn, Co, Cu, Ni, Cd and B12 | — | — — | Not measured in cited study | Not measured in the cited study; no value is implied. | Harvey et al. (2011) ↗ · Peloquin et al. (2011) ↗ · SAGE carbon-system study ↗ |
| SAGE | Cellular function | Fe and silicic acid | — | — — | Context only | Fe supports photosynthetic/electron-transfer and nitrogen-assimilation machinery; silicic acid forms diatom frustules. This is physiological context, not a demonstrated limitation or species-specific stoichiometry. | — |
| SAGE | Cellular function | Mn, Zn, Co, Cu, Ni, Cd and B12 | — | — — | Not reported | No route-specific cellular-function, stoichiometry or limitation claim is retained. | — |
| LOHAFEX | Treatment input / patch | Fe | — | — — | Local baseline required | Treatment and comparison waters are retained, but no public ambient numeric row is carried. | Martin et al. (2013) ↗ |
| LOHAFEX | Regional transect context | Nutrients and trace metals | — | — — | Local baseline required | No Southern regional numeric context is carried into the v16 public model. | — |
| LOHAFEX | Regional transect context | Mn, Zn, Co, Cu, Ni, Cd and B12 | — | — — | Not measured in cited study | Not measured in the cited study; no value is implied. | Martin et al. (2013) ↗ |
| LOHAFEX | Cellular function | Fe and silicic acid | — | — — | Context only | Fe supports photosynthetic/electron-transfer and nitrogen-assimilation machinery; silicic acid forms diatom frustules. This is physiological context, not a demonstrated limitation or species-specific stoichiometry. | — |
| LOHAFEX | Cellular function | Mn, Zn, Co, Cu, Ni, Cd and B12 | — | — — | Not reported | No route-specific cellular-function, stoichiometry or limitation claim is retained. | — |
| Study | Carrier / process | Method | Depth / timing | Status | Inference limit | Source |
|---|---|---|---|---|---|---|
| SOIREE | short-window trap and ²³⁴Th context POC/BSi export did not increase measurably over the reported short record. | drifting particle traps, upper-100 m standing stocks and ²³⁴Th | traps near 110 m; 13-day record | Not resolved | The record did not resolve fertilisation-enhanced export or later fate. | Boyd et al. (2000) ↗ · Nodder & Waite (2001) ↗ · Charette & Buesseler (2000) ↗ |
| EisenEx | in/out-patch ²³⁴Th comparison The observations did not distinguish in-patch export enhancement from surrounding waters. | ²³⁴Th in/out-patch observations | upper-ocean comparison; no single public horizon retained; three-week campaign | Not resolved | No carrier-specific transfer or later-fate conclusion is retained. | Gervais et al. (2002) ↗ · EisenEx ²³⁴Th dataset ↗ |
| SOFeX North | subduction-associated carbon transfer Two- to six-fold carbon transfer through 100 m was recorded as the patch subducted below a front. | autonomous Carbon Explorer floats | through 100 m; about 40 days | Observed | Carrier type, later remineralisation, deep circulation and atmospheric durability remain unresolved. | Coale et al. (2004) ↗ · Bishop et al. (2004) ↗ |
| SOFeX South | ²³⁴Th-derived POC flux Derived POC flux through 100 m increased by more than 700%. | ²³⁴Th-derived POC flux | through 100 m; study observation | Derived | The estimate does not identify a carrier or establish permanence. | Coale et al. (2004) ↗ · Buesseler et al. (2005) ↗ |
| EIFEX | one-eddy diatom-aggregate transfer Large porous diatom aggregates transferred across 100 m and at least half bloom biomass was observed below 1,000 m in one eddy. | multiple observations | across 100 m and at least half bloom biomass below 1,000 m; study window in one tracked eddy | Observed | Later remineralisation, circulation and atmospheric fate remain unresolved after the observed horizon. | Smetacek et al. (2012) ↗ · Berg et al. (2011) ↗ |
| SAGE | mixing/recycling with no induced deep-export event No iron-induced deep-export event was established. | study particle/carbon observations | no induced deep horizon established; 15.5-day record | Not resolved | The short record and mixing/recycling context do not resolve later export or atmospheric fate. | Harvey et al. (2011) ↗ · Peloquin et al. (2011) ↗ · SAGE carbon-system study ↗ |
| LOHAFEX | grazing/recycling with flux attenuation No fertilisation-induced downward particle-flux increase was observed; flux attenuated across the stated horizons. | particle-flux observations | mixed layer, 100 m and 200–450 m; 39-day record | Observed | No induced deep-transfer carrier or atmospheric-removal outcome is established. | Martin et al. (2013) ↗ |
Scroll the table horizontally to view Source.
| Study | Observed response | Morphology / food-web control | Source |
|---|---|---|---|
| EIFEX / LOHAFEX | EIFEX diatom aggregate case; LOHAFEX small-cell/grazer recycling contrast | Study-specific morphology; grazing and later fate remain context-dependent. | DOI |
| Nitrate / phosphate / silicic acid | Fe | Mn / Zn / Co / B12 | Measurement need | Source / evidence |
|---|---|---|---|---|
| Not reported in cited study | Fe addition tracked; Mn/Zn/Co/B12 local baseline required | Not reported in cited study | Local baseline required | Study evidence status · DOI |
03 · evidence pathway
Field observations, model outputs and unresolved questions answer different parts of the pathway. Together, the records describe study-specific responses; net atmospheric removal and legal status remain separate questions.
Primary evidence: Boyd et al. (2000) — SOIREE · Charette & Buesseler (2000) — SOIREE export · Gervais et al. (2002) — EisenEx · Coale et al. (2004) — SOFeX · Bishop et al. (2004) — SOFeX North · Buesseler et al. (2005) — SOFeX South · Smetacek et al. (2012) — EIFEX · Peloquin et al. (2011) — SAGE · Martin et al. (2013) — LOHAFEX · Yu et al. (2026)
SOIREE, EisenEx, SOFeX North, SOFeX South, EIFEX, SAGE and LOHAFEX were separate interventions; natural analogues remain distinct.
Diatom-dominated, mixed, non-diatom and small-cell, grazer-influenced responses make a single algal outcome invalid.
Short-window SOIREE and EisenEx observations, SOFeX 100 m transfer, EIFEX deep aggregates and SAGE/LOHAFEX recycling records address different depth horizons.
Deep transfer does not independently resolve air–sea equilibration, winter ventilation, circulation or later return to the atmosphere.
Scenario studies explore efficiency, re-emission and displaced productivity. Model outputs are not project measurements.
Biological response
Cell size, silica demand, aggregation, grazing, toxins and food-web pathways influence whether fixed carbon is recycled or transported.
Diatom blooms characterised SOIREE, EisenEx, SOFeX South and EIFEX. SOFeX North was a mixed low-silicate response; SAGE was largely non-diatom and LOHAFEX small-cell, grazer-influenced.
Taxonomy and chlorophyll alone do not determine grazing, aggregation, dissolved-carbon release, toxin response or later remineralisation.
Taxonomy, size structure, primary production, grazing, particle size, toxins, oxygen, pH, trace gases and food-web indicators form a matched time series.
Carbon pathway
SOIREE and EisenEx did not resolve fertilisation-enhanced export in their short windows. SOFeX North and South recorded 100 m transfer; EIFEX observed substantial biomass transfer below 1,000 m in one eddy; SAGE and LOHAFEX did not establish induced deep flux.
Deep particle observations do not alone quantify additional atmospheric CO₂ uptake, later re-emission, nutrient displacement or life-cycle emissions.
Open the five-breakpoint explorer →Observation design
Matched physical, biological, chemical and ecological observations separate intervention effects from background variability across time and space.
Air–sea exchange, particle fate, remineralisation, winter mixing, return pathways, trace gases and downstream ecology across seasons.
Explore instruments and limits →Long transit, severe weather windows, deep observing systems, winter follow-up and a large downstream observation corridor.
Operational costs depend on vessel time, instrumentation, sampling design and follow-up; no regional cost estimate is available here.
Featured evidence contexts
These records connect regional mechanisms to specific experiments, observatories and natural analogues without ranking the settings.
Can biological carbon change be separated from mixing, low silica, small-cell ecology and shallow recycling?
Southern OceanRead the evidence context →05Natural iron-fertilisation analogueWhich export mechanisms depend on sustained topographic supply and island seeding rather than iron relief alone?
Southern OceanRead the evidence context →06Natural analogue + deep-export observationsHow much deep flux reflects island-specific seed populations and a longer export season rather than a transferable open-ocean pathway?
Southern OceanRead the evidence context →07Recurring natural analogue + deep trapsWhat share of deep resting-spore flux is additional to natural production, and how do food webs, circulation and protected-area constraints shape the interpretation?
Southern OceanRead the evidence context →Governance context
High-seas experiments, protected island systems, EEZ research locations and disputed maritime spaces have distinct institutional and legal contexts.
Coordinates, water-column and downstream domains, vessel flag, ports, material, research purpose and potential effects shape the applicable routes.
Authority can depend on the exact activity, location, vessel, operator, material, duration, effects and applicable law.
Open governance & legal context →
