chapter11 Flashcards
(71 cards)
Examples for decreasing the abundance of dead zones
- Implement and Enforce Agricultural Runoff Regulations
Description: Limit the use of fertilizers and pesticides in agriculture through regulations, buffer zones, and best management practices (BMPs) to reduce nutrient runoff into water bodies.
Pros:
* Directly targets one of the main sources of nutrient pollution.
* Encourages sustainable farming practices.
* Can lead to long-term soil health improvement.
Cons:
* May face resistance from agricultural industries due to increased costs.
* Requires monitoring and enforcement, which can be resource-intensive.
* Potential impact on crop yields in the short term.
Upgrade Wastewater Treatment Plants
Description: Invest in technologies that remove nitrogen and phosphorus from municipal and industrial wastewater before it is discharged into rivers and oceans.
✅ Pros:
* Reduces point-source pollution effectively.
* Benefits urban areas with large populations.
* Promotes cleaner water for recreation and fishing.
❌ Cons:
* High upfront costs for infrastructure upgrades.
* May require ongoing maintenance and specialized staff.
* Smaller communities may struggle with funding.
- Restore Wetlands and Natural Buffers
Description: Rehabilitate wetlands, marshes, and riparian buffers that naturally filter out nutrients before they reach open water.
✅ Pros:
* Provides multiple ecological benefits (e.g., biodiversity, flood control).
* Low maintenance after establishment.
* Visually enhances landscapes and offers recreation spaces.
❌ Cons:
* Land use conflicts; may require converting agricultural or developed land.
* Takes time for restored ecosystems to become fully functional.
* Not always feasible in densely populated coastal areas.
Biomass
the mass of organisms per unit area
Units:
g carbon m-2
g carbon m-3
tonnes dry weight ha-1
J m-2
Standing crop (or standing stock)
total biomass in a certain area
Units:
g carbon
tonnes dry
J
Primary productivity
Rate of production of organic carbon by autotrophic organisms per unit area
Units:
g carbon m-2 day-1
g carbon m-3 day-1
tonnes dry weight ha-1 year-1
J m-2 s-1
Gross primary productivity
Total rate of carbon production
Net primary productivity
gross primary productivity minus respiration
Secondary productivity
rate of biomass production by heterotrophs per unit area
Unit: same as primary productivity
Primary consumer
Consumer of primary producer (i.e. herbivore)
Second trophic level of the community
Decomposers
bacteria and fungi living of dead organic matter
Detritivores
animals living of dead organic matter
Primary productivity
Turnover rate
primary productivity per biomass
Unit: day-1 or year-1
NPP/standing crop
What causes the global increase in primary productivity?
- In the tropics: less cloudiness, increased solar exposure, CO2 fertilization
- At Northern latitudes: increased temperature, water availability
What limits primary productivity?
- Photosynthetic efficiency is never higher than 10% and generally much lower
- Water shortage
- Temperature (is a condition, not a limiting factor)
- Temperature effects often interfere with water availability
- Part of the year, plants bear no photosynthetically active foliage
- Nitrogen, phosphorus and other nutrients often limit plant growth
- E.g. Belize mangroves fertilized for 5 years (left) and control (right)
- In aquatic communities, NPP is most often determined by nutrient availability
- Primary productivity may be limited by a succession of factors
- E.g. phytoplankton is limited by light, silicate, nitrogen, light
Energy conversion
- Primary productivity and secundary productivity are generally correlated
- Secundary productivity is usually <10% of primary productivity because:
- Plants are not consumed
- Food is excreted by the consumer
- Food is respired by the consumer
Energy conversion
Consumption efficiency (CE)
- The percentage of energy available that is actually consumed at a trophic level.
- In the case of herbivores it is the percentage of net primary productivity that is ingested.
Energy conversion
Estimates of herbivore consumption efficiency
Forests: 5%
Grasslands: 25%
Phytoplankton communities: 50%
Energy conversion
Assimilation efficiency (AE)
The percentage of energy ingested by an animal that is assimilated into its body.
Energy conversion
Estimates of assimilation efficiency:
Bacteria and fungi: 100%
Herbivores, detritivores: 20-50%
Carnivores: 80%
Energy conversion
Production efficiency (PE)
The percentage of energy assimilated by an organism that becomes incorporated into new biomass
Energy conversion
Estimates of production efficiency
Microorganisms: >50%
Invertebrates: 30-40%
Ectothermic vertebrates: 10%
Endothermic vertebrates: 1-2%
Energy conversion
Trophic transfer efficiency (CE x AE x PE):
The percentage of energy transfered from one trophic level to the next
Energy conversion
10% Law
Trophic transfer efficiency is generally 10%
Large variation in energy conversion between different communities
Decomposition
Mineralization
the conversion of elements from organic to inorganic forms
Decomposition
Immobilization
The incorporation of inorganic nutrients into an organic form
