eas 4300 guest lecture georgia tech biological oceanography jpm plankton and productivity...

EAS 4300 Guest Lecture

Georgia Tech Biological Oceanography

JPM

Plankton and Productivity• Phytoplankton

– Diversity

– Nutrients and light

• Primary production

• New production



JPMPublished by AAAS

P. G. Falkowski et al., Science 305, 354 -360 (2004)

Fig. 1. Examples of representative marine eukaryotic phytoplankton



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Tricho&Picos

N2-fixing cyanobacteria (Synechocystis) from Station ALOHA (10 µm scale bar)

Trichodesmium tufts



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Diatom Diversity (4)

Images from the Microscopy-UK Library: http://www.microscopy-uk.net/micropolitan/index.html

Top left: Chaetoceros debilis: spiny chain diatomBottom left: Ditylum brightwelliTop right: Coscinodiscus granii

NB: Much of the internal volume of the cell is filled by a vacuole. Strands of cytoplasm can be seen running through the vacuole.



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Emiliana huxleyi coccoliths

From the E. huxleyi site: http://www.soes.soton.ac.uk/staff/tt/eh//coccoliths.html



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Emiliana huxleyi World

From the E. huxleyi site: http://www.soes.soton.ac.uk/staff/tt/eh/



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Dinoflagellate Diversity (1)

Dinophysis & Ceratium http://www.whoi.edu/science/B/redtide/rtphotos/rtphotos.html



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Dinoflagellate Diversity (3)

Citharistes sp. Arrow points to chamber containing cyanobacteria.

Images from Carpenter 2002 Proc. Roy. Irish Acad. 120B: 15-18.

Ornithocercus magnificus. Arrow points to girdle list, which contains cyanobacteria. Inset shows epifluorescence image with

cyanobacteria fluorescing orange-yellow.



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Phytoplankton Growth• Specific growth rate

N(t) = Noeµt

– N = biomass (cell number, PN, PC, etc.)

– µ = specific growth rate (t-1)

• Note that µ really reflects the net growth rate

N(t) = Noe(p-r)t

– p = specific production rate (t-1)

– R = specific respiration rate (t-1)



JPMKrebs, Fig. 25.08

Marine N Limitation (Ryther & Dunstan 1971)



JPMData: eWOCE Line A16. Figure prepared with ODV

“Biolimiting” Behavior – NO3-



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North Atlantic Nutrient Ratios

Data: eWOCE. Plot prepared with ODV



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Redfield Ratio• The major nutrients occur in roughly constant ratios in deep

water and in plankton.– Nutrients are removed from warm surface waters by plankton and

released at depth by biological remineralization of organic matter.

– The average ratio of nutrients is called the Redfield ratio after A.C. Redfield.

– Biological activity drives the ocean to this state!

Pool C Si N P

Deep water 1000 50 15 1

Warm surface waters 870 0 0 0

Bulk particles 105 50 15 1



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Nutrient Limitation: N vs. P

• The N:P ratio of plankton is the same as the N:P ratio of the deep ocean (Redfield ratio).– Since N & P therefore enter the upper ocean in the same

proportions as they’re required by phytoplankton, why does N appear to be limiting?

– Food webs preferentially export N from the upper ocean.

Process N Budget P Budget

Growth 30% 17%

Fecal pellets 35% 23%

Dissolved excreta 35% 60%



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Light in the Water Column• The deeper you go, the darker it gets…

Mann & Lazier Fig. 3.05b (left), Miller Fig. 3.3 (right)

I(z) = Ioe-kz



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P/I Relationship

Lalli Parsons Fig. 3.5



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Stratification and Production

Mann&Lazier Fig.3.05

• Size of circles reflects intensity of mixing. Note inhibition of mixing by the pycnocline (A & C).

• Light decreases exponentially and determines where phytoplankton become light-limited.

• Below the euphotic depth, phytoplankton die.



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Production vs. Depth

Miller, Fig. 3.9

• Gulf of Alaska data for May (closed circles) and September (open circles)



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Patterns in Primary Production

Lalli & Parsons, Figs. 3.9 & 3.17

• Above: Typical annual cycles of primary production. Solid lines show phytoplankton biomass, blue lines show zooplankton biomass.

• Left: Schematic of relative abundance of light and nutrients at the sea surface as a function of latitude. Lines show relative seasonal change in primary production at three latitudes.



JPMMiller, Fig. 1.3

Riley-Sverdrup Bloom Model

• Assumptions– Biomass uniformly distributed

– P scales with I

– R is constant

• Compensation depth (Dc)

– P = R for individual phytoplankton.

• Critical depth (Dcr)

– Community between surface and Dcr in balance.

– Blooms occur when Dcr > Dmix.



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NH4+

New vs. Regenerated Production

modified from http://www.up.ethz.ch/research/nitrogen_cycle/index

BiologicalPump



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Measurement of Primary Production• ∆Biomass

– Practical difficulties in separating phytoplankton from other components of the ecosystem.

• Oxygen light-dark bottle method– The dark bottle measures community respiration.

– The light bottle measures net community photosynthesis.

• 14C Incorporation– The dark bottle provides ambiguous information.

– The light bottle measures something near net production.

– Long incubations may lead to recycling and equilibration.

• Bottle effects may compromise all these approaches!



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Distribution of Primary Production

Habitat P gC m-2 y-1

% Ocean Area

% 1° Production

Open Ocean 50 90 81.5

Coastal Ocean 150 9.9 17.9

Upwelling 300 0.1 0.005 • Open ocean production dominates the budget despite the low areal rates.

• Bottle effects may lead to underestimates in all environments, but especially in the open ocean.



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Chl Distribution: Atlantic

Composites: Sep 97 - Aug 98

eas 4300 guest lecture georgia tech biological oceanography jpm plankton and productivity...

Documents

biological activity

odv slide

n o e t n

specific growth rate

specific production

p ratio of plankton

specific respiration

n o e prt p