Primary Productivity

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Primary Production
Production:
Formation of Organic Matter
• Autotrophic Organisms
(Plants, algae and some bacteria)
– Photosynthesis
– Chemosynthesis
CO2 + Electron Donor + energy  CH2O + other
• Heterotrophic Organisms
(most bacteria and animals)
RESPIRATION
(Autotrophs & Heterotrophs)
CH2O + O2  CO2 + H2O + Energy (ATP)
Primary Production
Photosynthesis
6CO2 + 6H2O +light  C6H12O6 + O2
Need: Co2, H2O, Light and…..
N  DNA, RNA, Proteins
P  Energy Transport, DNA, RNA
Fe  Photosynthetic electron chain
….
Nutrients
• Macronutrients: N, P, Si, S, Mg, K…
• Micronutrients: Cu, Fe, Se…
Redfield Ratios:
P
SW
1
Phytopl. 1
N
15
16
C
1000
106
SW and FW Phytoplankton
macronutrient limitation
Oceanic Productivity Limiting
Factors
• Light
• Nutrients
Bristlecone Pine:
4.723 years old!
Kelp Forest
Macroalgae: 3% Ocean Photosynthesis
www.underwaterplanet.com
Phytoplankton
Phytoplankton: 97% Ocean Photosynthesis
Phytoplankton Dominance
• Phytoplankton
– Optimize surface area/volume
(4/3Пr2) / (4/3Пr3)
• Smaller size  larger surf. area/volume
• 5μm = 1/5
• 10μm = 1/10
– Small Particles sink slower
• Larger surf. area/volume  Slower sinking
Phytoplankton spines: increase in surface
for higher floatability
Energy – Mass models
Measuring Productivity
Measuring Productivity
• Plant Biomass
– How much phytoplankton is there
(mg Chl/m3) or (μg Chl/liter)
• Productivity
– A rate of how much carbon is produced
per time
• g Carbon / m3 / day
– GROSS Productivity = Carbon fixed through
Photosynthesis per time
– NET Productivity = Gross Prod - Respiration
Standing Crop: Plant Biomass
Grass clippings after 1 week: Productivity
What do Chl maps really measure?
Biomass!
Measurement of Productivity:
C14 incorporation experiments
Phytoplankton consumption: grazing
So Chl concentration is reasonable estimation
of primary productivity in surface waters
Ecosystem Productivity
(Annual net productivity)
Ocean primary productivity
Productivity and depth
Open water
(low productivity)
Coastal and Estuarine waters
(high productivity)
Productivity measurements with DEPTH
Photic Zone and Compensation
Depth
Upper Pelagic
HabitatsPhotic Zone
Vertical distribution of Primary production
•
•
•
•
Surface photoinhibition (UV light?)
Photosynthetic Maximum
Compensation depth
Critical Depth
– Refers to the whole population
– Photosynthesistotal = Respirationtotal
Productivity and depth
Critical Depth
• CRITICAL DEPTH: Depth at which total
primary productivity = Total respiration
• MIXING DEPTH – Depth above which all
water is throughly mixed (WIND)
THE PUNCHLINE:
• MIXING DEPTH > CRITICAL DEPTH: Then
Phytopl. are partially swept down and a
bloom cannot not occur
• MIXING DEPTH < CRITICAL DEPTH: then
a Phytopl. Bloom can occur
CRITICAL DEPTH
Nitrogen Cycle
Phosphorous Cycle
Figure 13.8
Vertical distribution of
Nutrients
Atlantic & Pacific nutrient distribution
Atlantic & Pacific oxygen distribution
Nutrients & distance to shore
Phytoplankton and distance to coast
Nutrient upwelling
July Chlorophyll
January Chlorophyll
Latitudinal effects on Primary
productivity
Seasonal stratification
Seasonal effects on Primary
Productivity
Consumers or Grazers
Temperate Ocean Spring Bloom
Absorption Spectrum
Adapted Algae
PI Curves
www.iku.sintef.no
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