Lecture 3 - Marine Food Webs & Limits to Fisheries Production Flashcards
How can global production be estimated?
Estimate global primary production and determine which fraction of it is transferred to fish stocks to calculate fisheries productivity
Primary production (definition)
The production of organic materials from inorganic components
What are the most common primary producers in the ocean?
Phytoplankton
What are the 2 main limiting factors for primary production in the ocean?
1) Light
2) Nutrients
Sufficient light for net photosynthesis occurs only in the top 1)___ of the oceans, only 2)___% of its volume
1) ~150 meters
2) 2%
1)___ and 2)___ are usually depleted in 3)___ and must be replenished from 4)___
1) Nitrate
2) Phosphate
3) surface waters
4) below
Mixed layer (definition)
The surface layer of the ocean with relatively uniform temperature and salinity, mixed by windstorms
Pycnocline (definition)
Zone of rapid change in water density that marks the bottom of the mixed layer and acts as a barrier to water mxing
What determines water density?
1) Temperature
2) Salinity
What are the 3 major types of ecosystems?
1) Open ocean gyres
2) Coastal/continental shelves
3) Upwelling zones (coastal and equatorial)
Coastal/Continental shelves have ___ primary production
high
Why are coastal/continental shelves sites of high primary production?
They are not deep, so nutrients return more easily.
Open oceans/gyres have ___ primary production
low
Why are open oceans/gyres sites of low primary production?
They are very deep, so nutrients are easily to to depth and nutrients slowly mix back to the surface
Coastal upwelling results in very ___ primary production
high
Why is coastal upwelling in Pacific ocean basins seasonal?
Winds due to the monsoon
Equatorial upwelling is a site of ___ primary production
high
Trophic level (defintion)
The position of an organism (bottom to top) in a food web
Food chain (definition)
A linear arrangement showing transfer of energy and materials
___ reflect the complex nature of trophic interactions
Food webs
All organisms feed ___
selectively
What determines the optimal range of prey?
1) Sensory mechanisms and thresholds for detecting prey
2) Physical constraints on contact (encounter) frequency
3) Minimum size that can be effectively captured/handled
4) Maximum size that can be effectively captured/handled
What constraints are predators under when prey are too small?
1) Detection
2) Retention effort
What constraints are predators under when prey are too large?
1) Capture efficiency
2) Handling problems
