Oceanography -- Biological Productivity and Energy Transfer

Primary Productivity

The conversion of carbon dioxide into organic compounds (usually sugar)

What are the ways we measure primary productivity

• Plankton nets- used to sample plankton

• Phytoplankton biomass- estimated using chloropyhll filters

• Satellites- SeaWifs, MODIS

Biomass

How much carbon there is

Different kinds of primary productivity? How do they occur

• Energy can come through photosynthesis

• Energy can come through chemical reactions (chemosynthesis)

Which primary productivity generates more biomass

Photosynthesis

Factors that affect photosynthesis- Nutrient Availability

• Nutrient availability includes nitrogen(protiens,amino acids), phosphorus(DNA membranes), iron (photosynthesis, RUBisCO abundant protien), and silica

• Productivity high along continental margin

• Redfield Ratio - C:N:P required by phytos at 106:16:1

Factors that affect photosynthesis- Solar Radiation

• Uppermost surface seawater and shallow seafloor

• Compensation depth – net photosynthesis becomes zero

• Euphotic zone—from surface to about 100 m (light for photosynthesis)

Factors that affect photosynthesis- Compensation Depth

(approx 100m in ocean, 20m in coastal ocean)

• Solar radiation light penetrates atomsphere in <1% of light penetrates below 100m in the ocean

• Photosynthesis is restricted to the euphotic zone which extends from the surface to the compensation depth for photosynthesis.

• The compensation depth for photosynthesis is where net production is zero

• The compensation depth for photosynthesis is approximately 100 m in the open ocean and may be less than 20 m in the coastal zone where the waters are more turbid

Factors that affect photosynthesis- Color of the Ocean

• Color of ocean ranges from deep blue (oligotrophic, low productivity) to yellow-green (eutrophic, coastal, upwelling)

• Factors include turbidity from runoff and photosynthetic pigment (chlorophyll).

• Secchi Disk – measures water transparency

Factors that affect photosynthesis- Light Transmission

• Visible light is a proportion of the electromagnetic spectrum

• Blue light wavelengths penetrate the deepest

• Longer wavelengths (red/orange) are absorbed first, red by upper 10 meters, yellow by 100 meters

Four Major Groups of Phytoplankton

Diatoms, Dinoflagellates, Cyanobacteria, and Coccolithophores

Diatoms

Phytoplankton. They are shells made of silica

Dinoflagellates

Phytoplankton. They have flagella for locomotion and their cell walls made of cellulose plates.

• They can cause “red tides” and other harmful algal blooms

Cyanobacteria

Phytoplankton known for ruining the party for everything that lived on Earth prior to their arrival which caused the “rise of oxygen”. They are the most abundant phylum in the photic zone.

Coccolithophores

Phytoplankton. Plates of calcium carbonate (chalk) and found on the seafloor.

Biological Pump

The removal of biomass produced in surface waters to the deep ocean, especially if it is buried. Carbon sinks to the bottom and is eventually subducted.

• Carbon is considered buried if it makes it to the sediment because it will take thousands to millions of years before it is released to the atmosphere again

Trophic Levels

The position organisms occupy in a food chain or food web. Each level represents a feeding stage of energy transfer in an ecosystem. Trophic levels are the building blocks of food chains and food webs, illustrating the transfer of 10% energy per level.

Biotic Community

Assemblage of organisms in a definable area

Ecosystem

Biotic community plus the environment around it

Compensation Depth

The ocean depth where phytoplankton photosynthesis exactly balances respiration, meaning net primary production is zero.

How is the compensation depth related to Spring Bloom

The compensation depth determines the onset of the Spring Bloom by defining the boundary for net phytoplankton growth

Spring Bloom

A massive annual explosion of phytoplankton (microscopic algae) growth, primarily occurring in high-latitude temperate and sub-polar oceans.

Temperate Region Productivity- Winter

Low Productivity

• Many nutrients, little sunlight

Temperate Region Productivity- Spring

High (Spring bloom)

Temperate Region Productivity- Summer

Low productivity

• Sunlight is abundant but Spring Bloom used nutrients

Temperate Region Productivity- Fall

High Productivity

• Fall Bloom (Smaller peak than spring)

Compensation Depth

The point in the water column where photosynthesis equals respiration, leading to zero net production (biomass)

Factors that affect photosynthesis

• Nutrient Availability

• Solar Radiation

• Compensation Depth

• Color in the ocean

• Light Transmission