Lecture 10 Flashcards
What role does light play in aquatic ecosystems?
Light serves as the primary energy source for photosynthesis.
What does Lambert-Beer’s law describe?
The attenuation of light intensity with depth.
What factors affect light extinction?
Water clarity
Phytoplankton density
Turbidity
How is turbidity measured?
Using Secchi disk depth, where higher turbidity corresponds to a shallower depth at which the disk disappears.
What is photosynthetically active radiation (PAR)?
Light in the wavelength range of 400-700 nm used for photosynthesis.
What defines the euphotic zone?
The depth where PAR reaches 1% of surface light.
How do stratified water layers affect light penetration?
Surface layers may allow more light penetration, while deeper layers with higher turbidity reduce light further.
What are the primary limiting factors for photosynthesis in aquatic systems?
Light, inorganic carbon, water, temperature, and nutrients (N, P, Fe, Si).
What does the photosynthesis equation describe?
6 CO₂ + 6 H₂O + light → C₆H₁₂O₆ + 6 O₂. It outlines the conversion of carbon dioxide and water into glucose and oxygen using light energy.
How do light conditions affect photosynthesis efficiency?
Algae adapted to low light perform better in dark conditions but are less efficient in high-light environments.
What is PAR and its role in photosynthesis?
Photosynthetically Active Radiation (400-700 nm) is the light spectrum usable by plants and algae for photosynthesis.
What does the light adaptation parameter (Ik) indicate?
- I(k) is crucial for understanding the light adaptation of algae or phytoplankton, allowing for predictions of photosynthetic performance across light gradients.
- For example, in turbid waters with low light availability, species with a low I(k) are more likely to thrive.
How does temperature influence algal growth?
Growth rate increases up to an optimal temperature (Topt) and decreases steeply beyond it.
What is the significance of sedimentation in algal models?
Sedimentation represents a mortality term, as algae that sink below the euphotic zone cannot photosynthesize and die.
How does respiration respond to changes in temperature?
Respiration increases with temperature until Topt, after which it declines rapidly.
