Food webs and Nekton

Biomass: Mass of living material present at any time, expressed as grams per unit area or volume

Productivity: Rate of production of living material per unit time per unit area or volume

Primary productivity: productivity due to photosynthesis (algae)

Secondary productivity: Productivity due to consumers of primary producers

Food chain: Linear sequence showing which organisms consume which other organisms, making a series of Trophic Levels. Very simple.

Food web: More complex diagram showing feeding relationships among organisms, not restricted to a linear hierarchy. Complex!!

Transfer of energy and nutrients from one trophic level to the next is not complete. Some material is not eaten, and not all material eaten is converted with 100% efficiency.

Budget for ingested food: Amount ingested = Amount egested (spit out) + amount respired + growth/reproduction investment for predator

Transfer between trophic levels: Production at highest level = primary production x food chain efficiency ^ number of links between trophic levels

Ocean food webs are varied in how efficient they are.

The more trophic levels a food web has, the less efficient it is.

Upwelling zones are the most efficient and productive while opean oceans are the least efficient and productive.