Biogeochemical Controls and Feedbacks on the Ocean Primary Production

Biogeochemical Controls and Feedbacks on the Ocean Primary Production

Carbon Cycle

Marine Biota

Export Production

Export Production of Organic Carbon

Trophic levels and dynamics

Ocean Ecosystem Structure

Example of a more complex Food Web

Ocean Ecosystem Structure

Energy Transfer between Trophic Levels is not efficient

Ocean Ecosystem Structure

Trophic levels and dynamics

Food Web

Energy

ENERGY

How about Mass Transfer?

How do we measure Biomass?

Alaska

200 km

Large scale Eddies

A simplified diagram of an ecosystem

A useful way to keep track of biomass in the lower trophic levels is to follow the path of MACRONUTRIENTS

Carbon C Nitrogen N

Phosphorus P

Redfield Ratio

C : N : P106 : 16 : 1

Redfield A.C., On the proportions of organic derivations in seawater and their relation to the composition of plankton. In James Johnson Memorial Volume. (ed. R.J. Daniel). University Press of Liverpool, pp. 177-192.

source 1) atmosphere

source 1) not biological, not atmospheric2) fluvial

C : N : P

source 1) from N2 atmosphere gas2) ocean subsurface3) remineralization of dead organic matter4) biological (e.g. excretions)

Nitrogen appears to be the limiting factorin ocean productivity in todays oceans

Simple Nitrogen Model

Zooplankton

Phytoplankton

Detritus

Nutrients

The arrows indicate fluxes between the pools of nitrogen

NO3

Chlorophyll

Largedetritus

Organic matter

N2 NH4 NO3

Water column

SedimentSediment

Phytoplankton

NH4

Mineralization

Uptake

Nitrification

Nitrification

Grazing

Mortality

Zooplankton

Susp.particles

Aerobic mineralizationAerobic mineralizationDenitrificationDenitrification

N2

Fixation

Mix Layer depth

Description of the oceanic ecosystem based on Nitrogen exchanges

Carbon Cycle

Marine Biota

Export Production

Export Production of Organic Carbon

Nutrient Sources for Primary Production

The fluxed of organic carbon must be sustained by an adeguate flux of macronutrients

If macronutrients are unavailable then the CO2 flux is reduced!

What are the controls on Export Production?

1) Ocean nutrient inventory

2) Utilization of nutrients in HNLC

3) Change Redfield Ratio

What are the controls on Export Production?

Surface CHL-A

1) Central Gyres 2) Upwelling Regions

Detailed structure of the oceanic ecosystem

Phytoplankton Blooms and Physical Environement

Phytoplankton Blooms and Physical Environement

Bands of the dionflagellate Lingulodinium polyedrum moving onshore over the troughs of a series of internal waves

Nonlinear Internal Waves and Phytoplankton

Isopycnals

Why do we care about the Export Production?

Nitrogen appears to be the control duringmodern time.

(but was not always this way e.g. duringlat glacial maxima)

1) Ocean nutrient inventory

What are the controls on Export Production?

N* = N – 16 P (Gruber & Sarmiento 1997)N* = N – 16 P (Gruber & Sarmiento 1997)

N = 25790

NN22 fixation fixation

DenitrificationDenitrification

Modern TIME

2) Utilization of nutrients in HNLC

What are the controls on Export Production?

Southern Ocean HNLC

Southern Ocean HNLC

3) Change Redfield Ratio

Do not know much about this!

What are the controls on Export Production?

Southern Ocean HNLC

Biologically Mediated Exchange of CO2 Between the Ocean and Atmosphere

The fluxed of organic carbon must be sustained by an adeguate flux of macronutrients

Phytoplankton Blooms

Bands of the dionflagellate Lingulodinium polyedrum moving onshore over the troughs of a series of internal waves

Trophic levels and dynamics

Food Web

Energy

How about Cyanobacteria?

Hydrothermal vents and Chemosyntheticbacteria