Lecture 3 Flashcards
What is gross net primary productivity?
The amount of inorganic carbon (CO2) fixed into organic compounds by autotrophs - respiration by autotrophs
Global distribution of areas of high carbon fixation
Highest around coasts, especially west coast of South America and east coast of Asia
Lack of nutrients in oceanic gyres so phytoplankton production low
What marine environments have the highest rates of primary production?
- Coral reefs
- Salt marshes
- Seagrass beds
- Kelp forests
Key primary producers:
Cyanobacteria: Trichodesmium and Prochlorococcus
Diatoms: Bacillariophyta
Dinoflagellates: Dinophyta
Coccolithophorids: Haptophyta
Where are different primary producers found?
Different primary producers found in different areas of the ocean
E.g. in tropical sea, diatoms found in spring and autumn and dinoflagellates in summer as they cope better with heat
Which waters are more productive and why?
Polar and temperate waters, because of overturn and mixing
What is a key primary producer that lives on sea ice?
Benthic diatom species
‘Sea ice algae’
What is upwelling and where does it occur?
Wind-driven motion of dense, cooler, nutrient-rich water towards the surface.
Upwelling occurs in coastal areas, in the Antarctic and along the equator
Upwelling can be more or less continuous, seasonal or sporadic
How does the wind cause coastal upwelling?
Wind blows parallel along the coast and Ekman transport carries surface water away from the shore at a 90 degree angle. Deep, nutrient-rich water is upwelled to fill the gap. These areas have rich fishing grounds as they are highly productive
What causes equatorial upwelling?
North and South equatorial currents cause water to move away at right angles to these currents, so deep water comes up in the middle
What is the El Niño Southern Oscillation?
Ocean temperatures and rainfall veer east. This sets up a feedback loop between the atmosphere and ocean that boosts El Niño conditions.
Warming in the Equatorial Pacific
How did El Niño years cause collapse of Peruvian fisheries?
Normally, thermocline tilting brings nutrient rich upwelled deep water off coasts of Peru and Chile.
The El Niño high atmospheric pressures in the Western Pacific caused offshore winds to be weaker so the thermocline tilted less. As a result less water was upwelled - fish were lost and seabirds died
What is the Southern Oscillation?
Seesawing of atmospheric pressure between Indian and Pacific Ocean - long distance linkage in atmospheric pressure
How does ENSO affect King penguins?
Negatively affects breeding success and adult survival
Increased temperatures affect lower trophic levels of food chain when animals in larval stage - reduced food available
What percentage decrease in king penguin adult survival is caused by a 0.26 degree increase in temperature?
9%
