Biogeochemical Controls and Feedbacks on the Ocean Primary

Biogeochemical Controls and Feedbacks on the Ocean Primary Production

Carbon Cycle Marine Biota Export Production

Export Production of Organic Carbon

Ocean Ecosystem Structure 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

Trophic levels and dynamics Food Web Energy

ENERGY

How about Mass Transfer?

How do we measure Biomass?

Alaska

Large scale Eddies 200 km

A useful way to keep track of biomass in the lower trophic levels is to follow the path of MACRONUTRIENTS Carbon C Phosphorus Nitrogen P N

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. 177 -192.

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

A simplified diagram of an NPZD Ecosystem Z P D N

Description of the oceanic ecosystem based on Nitrogen exchanges N 2 Nitrification Mix Layer depth NH 4 NO 3 Uptake Phytoplankton Mineralization Grazing Chlorophyll Zooplankton Mortality Water column Fixation Susp. particles Large detritus Nitrification N 2 NH 4 Denitrification Sediment Organic matter NO 3 Aerobic mineralization

A simplified diagram of an ecosystem

Carbon Cycle Marine Biota Export Production

Export Production of Organic Carbon

A simplified diagram of an ecosystem

What are the controls on Export Production? 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 CO 2 flux is reduced!

What are the controls on Export Production? 1) Ocean nutrient inventory 2) Utilization of nutrients in HNLC 3) Change Redfield Ratio

Surface CHL-A 1) Central Gyres 2) Upwelling Regions

What are the controls on Export Production? 1) Ocean nutrient inventory Nitrogen appears to be the control during modern time. (but was not always this way e. g. during lat glacial maxima)

Modern TIME N 2 fixation Denitrification N = 25790 N* = N – 16 P (Gruber & Sarmiento 1997)

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

High Nutrient, Low (Medium) Chlorophyll Regions Phosphorous Conkright et al. , 1994 Chlorophyll µm Sea. Wi. Fs Why aren’t the nutrients being completely utilized by phytoplankton?

What are the controls on Export Production? 3) Change Redfield Ratio Do not know much about this!

END of Lecture

Southern Ocean HNLC

Biologically Mediated Exchange of CO 2 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