| 1. Primary Production: |
| Learning Objectives: |
- Comprehension of processes involved in photosynthesis and production
- Understanding of controls on primary production: light and nutrients
|
| Characteristics: |
- Production of new organic matter by phytoplankton
- directly measured by 14C uptake (bottle
samples)
- indirectly measured by satellite (chlorophyll); color
- varies spatially and temporally
|
| Photosynthesis: |
- Phytoplankton contain pigments that capture energy from sunlight
- e.g. chlorophyll to make carbohydrates
- 6CO2 + 6H2O +
energy --> C6H12O
6 + 6O2
- Reverse process: respiration
- use of O2 and carbohydrates for energy:
- C6H12O
6 + 6O2 --> 6CO2
+ 6H2O + energy
- total photosynthetic production = gross primary production
- gross primary production - respiration = net primary production
- mass of organisms = biomass
- at any point in time = standing crop
|
| Controls on Primary Production: |
- Light:
- availability, intensity, seasonal change.
- Nutrients:
- N as NO3, P as PO4,
- replenished in surface waters by winter storms
- depleted by plant growth
- Nutrient Cycles:
- role of decomposers:
- release energy and nutrients by decomposition of dead phytoplankton
- control N and P cycles.
|
| Global Primary Production: |
- Distribution of Production:
- mainly (>85%) in less productive areas (130gC/m
2/a) of the open ocean
- food webs more direct in coastal regions (160gC/m
2/a; ~15%)
- especially upwelling areas (640gC/m2
/a; <1%)
- varies seasonally
- associated with light intensity at higher latitudes
|
| 2. Food Chains and Food Webs: |
| Learning Objectives: |
- Recognition of feeding inter-relationships between marine organisms
|
| Classification: |
- Reflect feeding hierarchy, grazing or detritus:
- primary producers --> herbivores --> carnivores
- zooplankton are major herbivores
|
| Trophic Levels and Trophic Pyramids: |
- Variety of marine organisms:
- primary producers, plants, bacteria
- secondary, herbivores
- tertiary, carnivores.
- omnivores (consume plants and animals)
- detritivores: consume organic detritus
- Inter-relationships of organisms from different trophic levels:
- abundance various inversely with size
- energy efficiency is important
- 80 - 90% loss between each trophic level.
|
