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 : P 106 : 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

source 1) atmosphere source 1) not biological, not atmospheric 2) fluvial C : N : P source 1) from N2 atmosphere gas 2) ocean subsurface 3) remineralization of dead organic matter 4) biological (e.g. excretions) Nitrogen appears to be the limiting factor in ocean productivity in todays oceans

Simple Nitrogen Model Zooplankton Phytoplankton Detritus Nutrients The arrows indicate fluxes between the pools of nitrogen

NO 3 Chlorophyll Large detritus Organic matter N2N2 NH 4 NO 3 Water column Sediment Phytoplankton NH 4 Mineralization Uptake Nitrification Grazing Mortality Zooplankton Susp. particles Aerobic mineralization Denitrification N2N2 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 Gyres2) 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 during modern time. (but was not always this way e.g. during lat glacial maxima) 1) Ocean nutrient inventory What are the controls on Export Production?

N* = N – 16 P (Gruber & Sarmiento 1997) N = N 2 fixation Denitrification Modern TIME

2) Utilization of nutrients in HNLC What are the controls on Export Production?

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 Chemosynthetic bacteria