Global Biogeochemical cycles and Ocean Productivity

Biological Oceanography Recall: goal is not to understand the biology of one particular organism (or group), but to understand organisms fit into the ocean as a system Examples of Biological Oceanography-type questions: What are main factors which control production in world ocean? What organisms and processes control recycling of matter? What main organisms are here? Why are they here (and not there)? How many are here now, and why now (this time of year)?

Recall: Nutrient Profiles Recall major nutrients are USED UP in surface by photosynthesis (eg: Phosphate (PO4), Nitrate (NO3), Silicate) BUT replaced in deep ocean by remineralization of sinking particles!

I. REVIEW: What actually creates nutrient depth profiles? (introduction to biogeochemical cycling )

Piece 1: PHOTOSYNTHESIS: light Photosynthe sis CO 2 + H 2 O + PO 4, NO 3, (Biolimiting salts = nutrients) CH 2 O + O 2 organic tissue + oxygen NOTE 1: Biolimiting SALTS are used UP, Oxygen is PRODUCED NOTE 2: can only happen in the SURFACE!

Piece 2: PARTICLE SINKING to depth FEEDING by ANIMALS- Wastes and remains..

Piece 3: Respiration at depth ( Animals & bacteria) CH 2 O + O 2 organic tissue + oxygen CO 2 + H 2 O + PO 4, NO 3, (Biolimiting salts = nutrients) NOTE 1: Oxygen is USED UP, Biolimiting SALTS (and CO2) are PRODUCED This PROCESS is called: REMINERALIZATION - because mineral nutrients Salts are replaced into the deeper sea

Result: Nutrient Profiles same shape in all oceans! Recall that nutrients are minor Components of total salts (0.5g) Main Nutrients 1.Phosphate (PO4) 2.Nitrate (NO3) 3. Silicate Trace Nutrients Eg: Iron (parts per trillion) (What is a part per trillion? 1 in 1,000,000,000,000 or a postage stamp on the state of Texas)ll

Profiles II: reactive gas? Gas Equilibrium with the atmpsphere Raining Organic Particles Downwelling and Isolation Respiration and Hence Depletion O2 Stage 1 Stage 2 Stage 3 Gasses Enter Sea from Atmosphere! In Equilibrium with surface ocean Move deeper in sea ( downwelling ) via mixing

OK, but: Why does O 2 change so much in the deep ocean? Profiles II: reactive gas

PO(µmol/kg) 4 0.0 0.5 1.0 1.5 2.0 2.5 3.0 0 500 1000 1500 2000 2500 3000 At surface: Photosynthesis Uses PO 4 Produces O 2 At depth: Respiration O 2 PO 4 1 mole = O 2 PO 4 3500 50 100 150 200 250 300 350 O (µmol/kg) 2 6.023 X 10 23 molecules molecular mass = grams/mole µmol/kg = 1 x 10-6 moles per kg

So with this background what are the main controls on production in different regions of the world ocean?

What are main controls on biological productivity in sea?

Review of Main Terms: Biomass = total standing stock of living matter, expressed as amount of carbon (usually g s C) Productivity = total biomass production in a given area (usually expressed per time, ie g C/ m2/ day ) Remineralization = process by which biological respiration returns key nutrients (=biolimiting salts) back to seawater, so they can be used again.

1. Light

Recall electromagnetic spectrum: Higher energy Lower Energy

Light does not propagate well through water Most is absorbed, but not equally. High energy (blue) light fastest, lower energy (red) light slowest. photic zone - illuminated zone of the surface ocean - aphotic zone - lightless zone beneath the surface - Light is a major factor in determining where photosynthetic organisms can live! Phytoplankton have to be near surface to get enough sunlight.

Light attenuation in the Sea:

Rapid loss of color!

Sunlight in Water Compensation Depth deepest depth at which plankton can get enough light to grow..

Different algae/plant pigments absorb at different wavelengths: Higher energywhat makes it down to deep! Lower Energy

Blue tropical surface water.. Close to shore: at surface Out to sea: 100m! Changes in Chl. Maximum depth heading out to sea..

2. Nutrients

Upper water structure: where do the building blocks come from?

Recall: Stratification Ocean is layered by density

MIXED LAYER is upper layer of water totally mixed up by the wind.. the deeper the mixed layer is, more of those deep- nutrients can reach the surface!

SEASONAL SEAS Good time for BREAK

Change in light availability vs. nutrient availability (= mixed layer depth) through year Seasonal Productivity cycle!

WINTER Light: Minimum Storms: Maximum Thus: Mixed Layer:? DEEPEST. Thus Nutrients are:? Nutrients = Maximum. OVERALL PRODUCTION? LOW

SPRING Light: INCREASING Storms: DECREASING Thus: Mixed Layer:? Getting shallower. Thus Nutrients are:? Nutrients = Still very high until: SPRING BLOOM!!!

SPRING BLOOM - Time of max. burst of production Whole Food chains go off, one after the other. Time of no more clear water its full of plankton. Sometimes, also dangerous toxic algae blooms. Classic Costal or (High Latitude) Chain

SUMMER Light: MAXIMUM (woo-wee..) Storms: Lowest Thus: Mixed Layer:? Shallow. Thus Nutrients are:? Nutrients get used up, soon ~ GONE. Time of lower productivity

FALL Light: Fading Storms: Increasing Thus Mixed Layer:? Deepens... Thus Nutrients are:? Nutrients, ~ Increasing. In many places final productivity BURST for Year = FALL BLOOM

Classical two-bloom seasonal cycle spring bloom fall bloom summer

ALL TOGETHER: B: NUTRIENTS Overall upper lat cycle A. SUNLIGHT D: GRAZERS C: PHYTO-PLANKTON

Overall Ocean Production Cycles

The McGraw-Hill Companies, Inc. Permission required for reproduction or display. World Ocean Primary Production & Gross Zones of world ocean production Primary Production Land & Ocean Data from S. Smith and J. Hollibaugh, Coastal Metabolism and the Oceanic Organic Carbon Balance in Review of Geophysics 31(1): 75-89, 1993

Upwelling: a special ( BUT IMPORTANT!) CASE near coasts (mostly)..

Effect of Coastal UPWELLING Coastal upwelling photo

At Most Mid-Latitude areas global upwelling patterns = production patterns

Higher latitudes: the seasonal seas Highly variable with Season- average picture does not capture!

Mid-Lower latitudes: More Constant, (upwelling driven production mostly near coasts) Central areas (=no upwelling) are deserts

Mid-Latitude Biomass Response The McGraw-Hill Companies, Inc. Permission required for reproduction or display. mid vs Low lat response and Low Latitude Biomass Response

Biomass vs Latitude

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