Teaching · food-web nutrient fluxes

Nutrients move through animals as well as through water

Biological nutrient fluxes run across the food web — not phytoplankton alone. Guilds, grazers, fishes, and marine mammals recycle iron and nitrogen into the sunlit ocean. Ecology KPIs and stop hooks sit above any carbon story.

Open Flux Explorer Read disclaimer

Ocean Flux framing only · restoration literacy, not a dosing product.

Phytoplankton guilds — base of the pump

Functional groups matter more than bulk chlorophyll: picophytoplankton, nanoflagellates, diatoms, dinoflagellates, and diazotrophs such as Trichodesmium.

Guild shifts change export efficiency, silicon demand, toxin risk, and food quality for zooplankton. The explorer’s diatom-fraction slider is a teaching proxy for “export-prone” communities — Assumption, not a surveyed ETP community.

Grazers, fishes, and the whale pump

  1. Zooplankton — Grazing regenerates NH₄⁺, DON, and Fe-binding organics in the mixed layer; fecal pellets contribute to export. Recycling in the sunlit zone and packaging for sinking are both fluxes.
  2. Fishes — Fact Moreno & Haffa (2014): marine fish store and recycle substantial Fe; commercial harvest removes Fe from the ocean reservoir and forgoes excretion cycling. Global storage and excretion orders reported in that paper are literature estimates; mass-specific rates in the explorer remain Assumption / synthesised (global totals ≠ local ETP rates).
  3. Marine mammals / whale pump — Fact Roman et al. (2014): whales as ecosystem engineers — surface fecal plumes recycle N and Fe after deep feeding; migrations move nutrients across latitudes. Fact Savoca et al. (2021): tag-based prey consumption revises mysticete intake upward; Southern Ocean mysticetes recycled on the order of ~1.2×10⁴ t Fe yr⁻¹ pre-whaling versus ~1.2×10³ t Fe yr⁻¹ today (paper estimates).
  4. Microbial loop & ligands — Bacterial remineralisation and organic exudates contribute Fe-binding ligands. Biology supplies ligand-rich organic matter; chemistry sets bioavailability.

Ocean Flux uses restoration of recycling services as a scientific framing — not a credit claim and not a field-dosing recipe.

Ecology-first KPIs

Carbon optionality only after MRV — these teaching KPIs come first.

  • Primary production quality

    Guild mix, not Chl-a alone — avoids the “green water = success” fallacy. Metrics remain Assumption until Phase B protocols.

  • Mesozooplankton

    Biomass / size spectrum tracks food-web transfer. Explorer defaults are order-of-magnitude teaching values.

  • Higher-trophic indicators

    Forage-fish and predator proxies speak to recycling capacity and fisheries co-benefit ethics.

  • Surface dFe + ligands

    Bioavailability with the chemistry page — not bulk Fe alone. Export proxies are teaching only; no credit output.

Stop hooks — STOP / reassess, never “optimise harder”

Hard teaching interlocks for the page and explorer. Caution bands below are Assumption for COP teaching, not regulatory criteria.

  1. STOP HAB risk — toxic-guild / dinoflagellate fraction above a caution band, or Si drawn down while N remains high (Si∶N stress favouring non-diatoms). Teaching trip: diatom fraction < 0.15 and surface nitrate > 5 µM.
  2. STOP Hypoxia / low O₂ — subsurface O₂ below a caution threshold in the analysis box (physics supplies O₂ context). Teaching trip: subsurface O₂ < 60 µmol kg⁻¹.
  3. STOP Anomalous bloom without grazers — chlorophyll rise with collapsing zooplankton proxy → food-web failure mode.
  4. STOP Ligand saturation + scavenging — adding an “Fe narrative” when ligands are saturated does not raise Febio (bridge to chemistry).

Flux Explorer — biology inputs

Six teaching sliders. Excluded: dosing recipes, credit tCO₂e, confidential protocols as sources.

Symbol Label Unit Default Status
Bpre Pristine higher-trophic biomass density g wet wt m⁻² 25 Assumption / derived productive tropical–upwelling teaching density — not ETP surveys
EFe Mass-specific Fe excretion µmol Fe g⁻¹ d⁻¹ 0.025 Assumption synthesised from Moreno & Haffa (2014) global totals
δ Depletion fraction (recycling capacity lost) fraction 0–1 0.67 Assumption predatory-guild decline order ~two-thirds (literature-informed)
fdiatom Diatom fraction of phytoplankton biomass fraction 0–1 0.40 Assumption teaching export-prone guild mix
Zmeso Mesozooplankton biomass index mg C m⁻³ 20 Assumption order-of-magnitude teaching default
Rwhale Relative whale-recycling index vs pre-whaling fraction 0–1 0.10 Assumption teaching from Savoca et al. (2021) SO Fe recycling ~10× lower today — not a global stock assessment

Explore in the Flux Explorer. Pair with chemistry bioavailability and physics supply timing.

Key citations

  1. Moreno, A. R., & Haffa, A. L. M. (2014). The impact of fish and the commercial marine harvest on the global ocean iron cycle. PLOS ONE, 9(9), e107690. https://doi.org/10.1371/journal.pone.0107690
  2. Roman, J., et al. (2014). Whales as marine ecosystem engineers. Frontiers in Ecology and the Environment, 12(7), 377–385. https://doi.org/10.1890/130220
  3. Savoca, M. S., et al. (2021). Baleen whale prey consumption based on high-resolution foraging measurements. Nature, 599, 85–90. https://doi.org/10.1038/s41586-021-03991-5
  4. Moore, C. M., et al. (2013). Processes and patterns of oceanic nutrient limitation. Nature Geoscience, 6, 701–710. https://doi.org/10.1038/ngeo1765

Disclaimer strip

Teaching model. Ecology KPIs first. No credits. No field dosing. See Disclaimer and Support.