Trophodynamics

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• Developed by Raymond Lindemann, a limnologist, but

• Largely abandoned by them, and

• Enthusiasticallyemployed by oceanographers

• Basis of productivity studies

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The Major Goal of Biological Oceanography:

“…determination of time-varying plankton productivity in the world ocean…”

-Barber and Hilting (2002)

Simple Model for Productivity, PP

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PP = × aph × Eo

Primary production = ‘fraction’ of Irradiance absorbed x efficiency of conversion

Since Chl-a is the main ocean color data product

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PP = × a*ph × Chla × Eo

Absorption Properties

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atot = aw + acdom + anap + aph

Case 2 waters: acdom and anap

• are significant, or dominant• do not co-vary with aph

PPinsitu may be predictable from the Simple Model

• Gulf of Maine in the ‘90s• Turbid Estonian Lakes• Irish Sea

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Examples from:

Gulf of Maine, ‘90s

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Marra et al. 1993, L&O

Estonian (Turbid) Lakes

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Arst et al., 2008

Irish Sea:Absorption Model explained more

variance

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Tilstone et al., 2005

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Irish Sea:Application to Satellite Data

Tilstone et al., 2005

The Way Forward

1. Need a model for CDOM (at least) dynamics

(‘light utilization index’) models deserve another look

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1. CDOM Dynamics

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Arabian Sea, SE Monsoon

Increasing time near surface?

Increasing photo-oxidation?

2. models

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Falkowski, 1981

= B/4.6

Requires and accurate definition of the euphotic zone!

Platt, 1986

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modeling: Northern Gulf of Mexico

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We need better estimates of the Compensation Depth to define the

Actual Euphotic Zone

ONDEQUE, PP and Rp for

stations in the NW Atlantic

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The Compensation Depth (where P=R)

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ONDEQUE program, NW Atlantic, 2008Marra et al., submitted

1%Eo

P=R

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AUTOTROPH BACTERIAL

RESPIRATION

DISSOLVED ORGANIC MATTER

EUPHOTIC DEPTH