Primary Productivity, Blooms, and Nutrients

Christa Lee Spurrell and Brian Gibbons

The amount of new biomass produced within the world’s marine and freshwater systems during a given time period.

More specifically the conversion of inorganic carbon to organic carbon at a rate of kg/m2/day.

Takes place only in the photic zone and depends upon photosynthesis, and to a lesser degree upon chemosynthesis

Primary Productivity

Function of primary producers or autotrophs, that form the base of the food chain. In the ocean most primary production is produced

through algae with a small contribution from vascular plants.

Distinguished as net or gross primary productivity. Gross(GPP): the rate at which an ecosystems

producers capture and store a given amount of chemical energy as a biomass in a given amount of time. A small portion of this energy is used in the cellular

respiration in primary producers along with maintenance of existing cells.

Primary Productivity

Net(NPP): the remaining fixed energy; the mass of photosynthate. NPP= GDP – respiration (by plant) some of the net energy produced by primary

producers is used in their reproduction.The main source of this energy is obtained through sunlight and a minute fraction is driven by lithotrophic organisms, which use the chemical energy of inorganic molecules.

Primary productivity

Photosynthesis (equation):

CO2 + H2O Ch2O + O2

Chemosynthesis (equation):

CO2 + O2 +4 H2S CH2O + 4 S + 3 H2O

Primary Productivity

The Calvin Cycle of Photosynthesis

Photoautotroph Abundance

The sunlit zone of the Ocean is referred to as the Photic Zone (Euphoric Zone). Roughly 10 to a hundred meters in depth.

The thickness of the photic zone is defined as the depth at which light reaches 1% of it`s surface value.

Net photosynthesis in the water column is determined by the interaction between the photic zone and the mixed layer via turbulent mixing by wind energy.

This mixed layer can vary from being shallower or deeper than the photic zone. When the mixed layer is deeper than the photic zone

the resident phytoplankton does not produce a net growth.

Photic Zone

When the mixed layer is deeper than the photic zone the resident phytoplankton does not produce a net growth.

Critical Depth is the maximum depth of the mixed layer in which net growth can occur.

When the mixed layer is shallower than the critical depth net primary production occurs.

In temperate regions primary production is seasonal, where it varies with both incident light, which is reduced in the winter, and the degree of mixing which is increased in the winter.

In tropical regions light may vary slightly across the year, while mixing occurs episodically; such as during large storms or hurricanes.

Photic Zone

A Algal Bloom is a rapid increase or accumulation in the population of algae in a aquatic system and can occur in both fresh water and salt water systems.

Typically only one or a few plankton species are involved. A discolouring of the water caused by a large density of pigmented phytoplankton cells.

Blooms can range in color depending on the species of Algae involved (green, yellow-brown, red).

Bright green blooms are a result of blue-green algae which are really cyanobacteria.

Blooms may also consist of macro algal species not phytoplankton species, these blooms are recognized by large blades of algae that may wash up onto the shore line

Blooms

Blooms

Harmful algal blooms or HABS are algal events involving harmful phytoplankton such as dinoflagellates of genus Alexandrium and Karenia.

These blooms are also known as red tides because of the red/brown pigment of algae cells.

Habs also commonly produce natural toxins, and cause mechanical damage to nearby organisms.

They are associated with large scale marine mortality events such as: mass mortalities in fish, sea birds, sea turtles, and marine

mammals. Human illness or death caused by the consumption of

contaminated sea food, such as shell fish. Mechanical damage to other organisms such as disruption of the

gill epithelial tissues in fish causing suffocation. Oxygen depletion of the water column(hypoxia or anoxia) from

cellular respiration and bacterial degradation. Zones in which the water column has insufficient supply of oxygen to the point in which organisms are unable to thrive are called dead zones. Which are associated with sewage run off from coastal settlements such as large coastal cities.

Harmful Algal Blooms

Dead Zones

Mixing of nutrients is a limiting factor in primary production. Inorganic nutrients such as nitrate, phosphate and silicic acid,

are necessary for phytoplankton in the creation of their cells and cellular machinery.

Due to the gravitation sinking of particulate material (such as plankton, dead and fecal material) nutrients are constantly lost from the photic zone and are only replenished by mixing and upwelling of deep water masses.

There is reduced mixed layer production in the summer due to the constant uptake of nutrients in primary production, which can lead to nutrient exhaustion in many regions of the ocean.

The excess nutrients from coastal pollution may cause algal blooms which can result in the creation of dead zones and/or fish kills.

Nutrients

Dawson, E.Y. (1966). Marine Botany: An Introduction. Holt, Rinehart and Winston, Inc.: New York.

http://kingfish.coastal.edu/biology/sgilman/770productivitynutrients.htm

http://sogasex.wordpress.com/2008/03/30/primary-productivity/

http://www.science.oregonstate.edu/ocean.productivity/

http://www.sciencedaily.com/articles/a/algal_bloom.htm

http://marine.rutgers.edu/opp/ http://www.wsu.edu/~dybdahl/lec10.html

References