Lecture 11 Flashcards
What nutrients are essential for algal growth?
Nitrogen (N), phosphorus (P), silica (Si), and sometimes iron (Fe).
What is Liebig’s Law of the Minimum?
Growth is limited by the nutrient present in the lowest concentration relative to requirements.
What is co-limitation?
When multiple nutrients simultaneously limit growth.
What is the Michaelis-Menten uptake model?
A model describing nutrient uptake rates as dependent on nutrient concentration and a half-saturation constant.
How do light and nutrient availability interact to influence algal growth in aquatic environments?
Surface layers receive more light but may have nutrient depletion, while deeper layers have more nutrients but less light.
What is the Redfield Ratio and why is it important?
- The Redfield Ratio (N:P = 16:1) is a rule of thumb indicating the limiting nutrient in aquatic systems.
- A ratio > 7 suggests phosphorus limitation,
- A ratio < 7 indicates nitrogen limitation.
Which nutrients are typically limiting in marine and freshwater environments?
Nitrogen is usually the limiting factor in marine environments, while phosphorus is more commonly limiting in freshwater systems.
What role does silicon play in nutrient limitation?
Silicon is essential for diatoms, as it forms their skeletons. Coastal development and water depth can cause silicon limitation.
What happens during a diatom bloom in terms of chlorophyll-a and silicon?
There is typically a negative correlation: as diatoms grow and use silicon, chlorophyll-a levels deplete.
What is co-limitation at the community level?
In community-level co-limitation:
- Different species are limited by different nutrients.
- Adding either nutrient increases total community biomass, but individual species only respond to the nutrient they are limited by.
What is biochemical limitation?
Biochemical limitation occurs when essential elements for nutrient uptake are lacking, such as iron for photosynthetic machinery.
What is the role of phosphorus in living organisms?
Phosphorus is crucial for ATP production, DNA/RNA structures, and cell membranes, making it essential for energy metabolism.
Why is phosphorus often found in fertilizers?
Phosphorus is a key nutrient for plant growth, commonly added to increase productivity in agriculture.
How does water flow affect nutrient load transport?
Nitrogen, being dissolved, is proportional to water flow, while phosphorus (often particulate) is transported mainly during high-flow events like floods.
What is grazing “G” in ecological models?
Grazing represents zooplankton consumption of algae and is often modeled using Lotka-Volterra equations where zooplankton biomass influences grazing intensity.
How does temperature influence grazing?
Grazing rates are often proportional to temperature due to its effect on metabolic rates.
Why is phosphorus cycling considered slow?
Phosphorus has no gas phase and is mainly stored in sedimentary deposits, making its cycle slower compared to nitrogen.
What is the significance of adsorption in phosphorus availability?
Phosphorus binds to particles like clays or forms complexes with metal ions. Adsorbed phosphorus can become bioavailable under certain conditions (e.g., low oxygen).
What are common sources of phosphorus loads in aquatic systems?
Sources include agricultural runoff, wastewater, industrial discharge, and internal loading from sediment release.
How does internal phosphorus loading occur?
Internal loading happens when phosphorus is released from sediments due to factors like low oxygen (anoxia), turbulence, or bioturbation.
What is co-limitation due to synergistic effects?
This occurs when the addition of one nutrient enhances the uptake of another limiting nutrient, improving growth.
How does grazing overlap between water-quality and fishery models?
Zooplankton grazing impacts both algae biomass (water quality) and fish production, making it essential to couple these models.
what’s the limiting factor?
nitrogen
what’s the limiting factor?
phosphorus
what’s the limiting factor?
what’s the limiting factor?
- Adding P or N alone causes some increase, but +all results in much higher growth than any individual nutrient addition.
- Co-limitation type: Likely biochemical co-limitation, as multiple nutrients are required to enhance growth synergistically.