How the “Ecumenical Iron Hypothesis” Emerged from

Ocean Station P Data Charlie Miller

Prof. Emeritus of Oceanography Oregon State University

In High-Nitrate-Low-Chlorophyll oceanic ecosystems, “phytoplankton cell size is restricted by iron limitation. The small cells are accessible to grazing by protists.

The high growth potential of protists ensures they will always overtake and suppress increases in phytoplankton

stock.”

Strom, Miller & Frost (2000)

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Seasonal production cycling appears in the biomass of mesozooplankton

Fifth Copepodite

OSU technicians, aboard 1980-81 Harold P. Batchelder Martha Clemons Richard Conway Net Sampling to 2000 m

CCCG Quadra

Limited-mixing and copepod-grazing hypothesis proposed for test as the SUPER Project

SUPER 1 and 2: The IRON hypothesis enters here.

> Solubility of Ferric hydroxide (Fe(OH)3) in seawater is ~0.5 nanomolar, less than 10-9 moles/liter.

> John Martin was asked to join us. He replied, “No, too busy with Vertex.”

> John Reuter (Portland State U.) and Don Anderson (now WHOI) proposed an iron enrichment experiment.

> NSF said project too big. Cutting back, we went with testing grazing (we are grazer/grazing experts). Oops.

RV Wecoma Two SUPER cruises , May & August 1984

SUPER Group: Kenneth L. Denman IOS Charles B. Miller OSU Ann E. Gargett Patricia Wheeler David L Mackas Beatrice Booth UW Nicholas Welschmeyer Bruce W. Frost Harvard Michaek R. Landry Joyce Lewin Carl J. Lorenzen Mary Jane Perry Michael Dagg

1.

Mixing had the long established limitations

Bouyancy frequency, calculations by Ken Denman and Ann Gargett

2. From Beatrice Booth: Phytoplankton in the oceanic Gulf of Alaska are almost all very small

3. Copepods distribute in the two upper mixing layers:

Mackas and Sefton sampling from the CCCG Parizeau Note the new species

Fifth Copepodite

4. Welschmeyer & Lorenzen chlorophyll-budget technique

5. Most grazing is by microzooplankton, by protists

0.133 d-1 61.5% 31.1% 7.3%

6.

Neocalanus plumchrus were not eating phytoplankton, but they were growing. The progression in May of copepodite stage composition demonstrated that. Miller and Nielsen

Back to sea: Super 3 and 4, 1987 Super 5 and 6, 1988

Bruce Frost – modelng in Seattle RV T. Washington Charlie Miller Pat Wheeler Mike Landry Nick Welschmeyer Tom Powell Mike Dagg Suzanne Strom and many more Parizeau – Dave Mackas

1. Strom & Welschmeyer 1991

2.

3.

Wheeler and Kokinnakis

4. Copepods = 1 N. plumchrus C5 per liter Landry and Lerner-Fournier

5. In 1987 John Martin (and Fitzwater,1988) reappeared in our lives:

Tests: SERIES “Ironex-type” mid-ocean iron addition – 2002 (not shown) Right: Mt. Kasatochi (a) ash deposition & (c) resulting phytoplankton bloom

Roberta Hamme et al. (2010)

6.

Bruce Frost (1987, ’91, ’93)

P vs. I

mixed layer depth

temperature

Nitrate irradiance

So, back to weather- ship data to ➤ generate models.

6’. 0-50 m chlorophyll protist biomass

primary production

Mixed layer detritus

Lots of models beside Frost’s, for example: Fasham, MJR (1995) Variations in the seasonal cycle of biological production in subarctic oceans: a model sensitivity analysis. Deep-Sea Res. 42:1111-1149. Denman, KL and Peña, MA (1999) A coupled 1-D biological/physical model of the northeast subarctic Pacific Ocean with iron limitation. Deep-Sea Res. II, 46: 2877-2908. [and several others by Ken and Angelica]

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Strom, Miller & Frost (2000)

. .

7.

What sets lower limits to phytoplankton stocks in high-nitrate, low-chlorophyll regions of the open ocean? MEPS 193: 19-31

1959-1988- surface

7. Strom, Miller & Frost (2000)

1. ”Protists” in the model (“Z”) graze the phytoplankton to nearly zero, unless feeding thresholds are applied. Frost’s formulation assumed positive thresholds.

2. Data then available for protists (11 studies) showed NO food-availability thresholds for feeding by protists.

Prey Concntration, µg carbon/liter

Tintinnopsis fed Isochrysis Verity (1985)

7.

7. Answers: 1. Newer data do (maybe) show grazing thresholds for microherbivores (Paffenhofer, Sherr & Sherr (2007):

Lessard & Murrell (1998): Sargasso field dilution experiment

2. Switching by microheterotrophs (Z) to eating each other at low phytoplankton stocks (P): Lotka-Volterra prey-predator cycle: dP/dt = aP - 0.06PZ, (a=0.69 d-1 ) P increase = growth – grazing

dZ/dt = 0.02PZ - 0.5Z Grazer = grazing – predation increase

7. Answers:

2. Switching by microheterotrophs (Z) to eating each other at low phytoplankton stocks (P): Lotka-Volterra prey-predator cycle: dP/dt = aP - 0.06PZ, (a=0.69 d-1 ) P increase = growth – grazing

dZ/dt = 0.02PZ - 0.5Z – 0.03Z2

Grazer = grazing – predation – cannibalism growth

7. Answers:

CCCG Vancouver

Hang on Martha