Lecture 13 Export Production Lecture 12 summary: Primary Productivity is limited mostly by nutrients. In low latitudes (< 45 o ), the limiting nutrient.

Lecture 13 Export Production

Lecture 12 summary:

Primary Productivity is limited mostly by nutrients.

In low latitudes (< 45o), the limiting nutrient is most often NO3.

In high latitudes, iron (Fe) plays an important role.

Net Primary Production

How much of this organic matter production sinks to the deep ocean?

CO2Corg

Phytopl.

Zoopl.Bacteria

Respiration (Heterotrophic)

Photosynthesis “Net Primary Production (NPP)”

Rh

NPP

Export Production

From NPP to Export Production

Define the f-ratio. What happens to export () if primary productivity (NPP) goes up?

Export and sinking

v

Low nutrient areas favor small plankton due to surface area/volume consideration.

High nutrient areas favor large plankton, rapid sinking rates, due to force balance (gravity=friction).

The influences of plankton size lead to the following conclusion: Areas of high nutrients can support larger plankton, and a faster sinking of organic matter to the deep ocean.

DiatomsLarge cellsFast growingRequire high nutrientsRequire Silicate Surface Nitrate

Region of high relative abundance

Prochlorococcus

Synechococcus

PicoplanktonExtremely smallAutotrophic

Regions of high relative abundance.

Respiration and Temperature

Like phytoplankton, heterotrophs (zooplankton and bacteria) are also sensitive to temperature. In warm waters, their rates of respiration (Rh) go way up (this is why we put food in the fridge!). As a result, warmer waters should be more efficient at recycling resources, rather than exporting them.

Nitrosomonas

Nutrient Recycling

Fast sinking Slow Heterotrophs

Large phytoplankton

High nutrients

High NPP

1) High export/low recycling regime

and/or

Zooplankton Bacteria

Cool Temperatures

Heterotrophs very sensitive to temperature

Drag vs. Size

Area/Volume

Nutrient limitation

Nutrient Recycling

Slow sinking Fast Heterotrophs

Small phytoplankton

Low nutrients

Low NPP

2) High recycling/low export regime

and/or

Zooplankton Bacteria

Warm Temperatures

Heterotrophs very sensitive to temperature

Drag vs. Size

Area/Volume

Nutrient limitation

Particle Export Ratio (“f-ratio”)

Empirically derived effect of temperature and Net Primary Productivity on the f-ratio (the fraction of productivity that gets exported), and approximate values for some large ocean regions.

0.1

1.0

10

100

SubtropicalGyres

Equatorial

North Atlantic

Southern Ocean

Coastal

The Particle Export Ratio

Identify regions for each bubble in previous plot.

Export Production

The figure is the product of which two previous maps?

Coccolithophores

Emiliani Huxleyi

Produce CaCO3 shellsCan tolerate low light levelsSize 1-40 μm (microplankton)

Region of high abundance

DiazotrophsCan fix nitrogen

Trichodesmium

Region of high abundance. Why?