C. Biomass & Productivity a. Gross primary production ...

Geol 117 Oceans
Lecture 20b: Production
IV. Primary Production (p.p.) Continued from Lecture 20a
C. Biomass & Productivity
1. Biomass = mass of organic matter (in grams)
a. Gross primary production = total amount of organic material synthesized by
photo & chemosynthesis
b. Net primary production = Gross p.p. – organic material consumed by respiration
- Net p.p. is available for consumption by herbivores.
2. Primary production, latitude, nutrients
a. High latitude
i. Overturn in winter brings nutrients to surface
ii. Summer sun brings phytoplankton bloom
iii. Short but v. productive because of all the nutrients
b. Mid latitude
i. Winter overturn brings nutrients to surface
ii. Spring bloom with sun
iii. Biomass decreased by grazing
iii. Late summer bloom (separate species) smaller due to low nutrients
c. Equatorial region
i. Slight summer increase
ii. Overall low productivity – why?
iii. Little vertical mixing – nutrients not brought to surface
d. Depth and photic zone – producers are photosynthetic
e. Seasons: Solar Radiation for photosynthesis

D. Nutrients and Dead Zones
1. Recall that N and P are the nutrients we have talked about
a. Abundance on E: that they are not made or added to earth
b. Source:
i. Geologic: either released from mantle or weathered rocks
ii. Biological (dominant): Recycled from decay of organics – BACTERIA!

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Geol 117 Oceans
Lecture 20b: Production
2. What are each used for?
a. N (as nitrate NO3-) is necessary for making proteins
b. P, as phosphate (PO4) required for DNA, making cell walls and in respiration
3. How do they make it to the oceans?
a. Nitrogen cycle
i. Organisms die and BACTERIA produce nitrate in soil during decomposition
ii. Fertilizes into groundwater
– Too much can kill
– Plankton blooms, they die, sink and bacteria decompose them consuming all
Oxygen and kill aerobic organisms = dead zones of gulf coast, Chesapeake
estuary, Baltic and Black seas!
iii. Nitrate discharged to rivers from GW and then to oceans
iv. Decaying marine plants and animals (and waste) release NO3-
- Deposited in sediments
- Recycled to photic zone by upwelling deep waters
b. Phosphorous cycle
i. P Sources: plant and animal tissue, animal waste (guano), rocks
ii. Bacteria in soil convert organic P into soluble phosphates
iii. Phosphate discharged to rivers from GW and then to oceans
iv. Decaying marine plants and animals (and waste) release PO4
- Deposited in sediments
- Recycled by upwelling

E. Global Primary Production

1. Areas of high productivity

a. Coastal areas appear more productive than open oceans

i. Estuaries

ii. Coastal upwelling

b. Areas of freshwater mixing (deltas & estuaries & melting sea ice)

i. Fresh water floats forming a poorly mixed layer
ii. Stable layer for phytoplankton to live
iii. Estuaries, Amazon, Nile, Congo

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Geol 117 Oceans
Lecture 20b: Production
c. Areas of divergence (open ocean upwelling) – bring nutrients to surface
i. Equatorial Pacific
ii. Note areas of convergence (downwelling) in geostropic gyres have low
productivity
2. Comparing productivity
a. Notice
i. Upwelling zones have greatest Primary Productivity, but small area => small
Total Primary Productivity.
- However, productivity is concentrated in upwelling and coastal zones
ii. Open oceans lowest P. Prod., but vast size => greatest total P.P.
- However, productivity ‘diluted’
b. Compared to agriculture
i. Upwelling zones and estuaries approach productivity of agriculture!
ii. i.e. estuaries and upwelling are dense with life!

V. Webs
A. Base of food chain/webs = phytoplankton!
1. Photosynthetic protists: Require sunlight and nutrients
2. Supply nutrients to all other organisms
B. Zooplankton = link in all marine food chains
1. Zooplankton = herbivore plankton, most numerous herbivores by number & mass
2. Primary consumers
a. Convert all plant material into animal tissue
b. Feed all carnivores (directly or indirectly)
C. Webs
1. Complex relationship of interconnected food chains
a. Notice
i. Organisms feed at various ‘levels’ of the web
ii. Organisms occupy various levels throughout life cycles
iii. Thus disruption of one level effects all higher levels!
b. Webs represent pathways for nutrients and food energy

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Geol 117 Oceans
Lecture 20b: Production
2 Trophic pyramids
a. Primary Producer at base
i. Input Solar Energy and nutrients at base
ii. Zooplankton at second trophic level
iii. Carnivores above
iv. Organic matter out at each level -> bacteria for nutrient cycling
b. Trophic levels
i. Numbers and total mass greatest at base
ii. Size increases with level
iii. Total number decreases with level
c. Energy transfer = 10% (or 90% loss)
i. To produce 10 kg of salmon, 100 kg of small fish, 1000 kg of zooplankton
ii. 90% loss to metabolism, living, loss by decay after death
3. Revisit Antarctic food web
a. Decline in baleen whale (hunting)
b. Killer whale begins feeding on lower levels – requires LOTs of mass to replace
whale!
c. Begins to disrupt entire food web by taking other predators in greater numbers.
- = Over harvesting! -> disrupts nutrient recycling

VI. Chemosynthesis and Extremophiles

A. Chemosynthetic communities

1. Base of food web = Chemotrophic bacteria

a. Use S-compounds to make organic molecules from CO2 and H2O (like

photosynthesis)

b. Live in water and in crust
c. Extremophiles – live at extreme conditions

i. Some up to >500ºC
ii. Live near volcanic eruptions and in vents
iii. Live in the crust too.
iv. Stop reproducing at v. high Temperatures – then start again
v. Others are cold bacteria

- Living in ice, deep water and sediment
- Reproducing at T < 12ºC (i.e. cold water reproducing) – life on Europa?

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Geol 117 Oceans
Lecture 20b: Production

2. Higher trophic levels in vent community
a. Feed directly on bacteria – some shrimp
b. Or, feed on bacteria bi-products = symbiotic relationship
i. Tube worms have bacteria in ‘gut’
ii. As do many other organisms e.g. clams & mussels
c. Some predators from open ocean feed on these organisms (or feed part of chain)

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