Lecture 9 Flashcards
What is the Von Bertalanffy Growth Model?
A model predicting asymptotic growth, where growth slows as individuals mature
What is the Ursin Metabolic Model?
A model that balances ingested food and metabolic losses.
What assumptions are made in the Ursin model?
- Caloric Content: Consistent caloric content in consumed food.
- Assimilation Efficiency: Constant fraction of food digested.
- Size Scaling: Food intake and metabolism scale with body size.
How can the Ursin model inform fisheries management?
By predicting optimal harvesting times and accounting for metabolic constraints to avoid overfishing.
What does Lambert-Beer’s law describe in terms of light extinction?
It describes the exponential decay of light intensity as it passes through a homogeneous medium: I(z) = I(0) * e^(-kz).
What is k in Lambert-Beer’s law?
The extinction coefficient (k) represents the medium’s ability to absorb or scatter light.
What influences the extinction coefficient (k)?
- The medium’s properties (e.g., water or air),
- the wavelength of light
- and the concentration of particles.
How is optical depth defined?
Optical depth (k * z) is a measure of how much the layer can block light, where z is the depth.
What happens when the medium is stratified?
Different extinction coefficients (k) apply to different layers, and the light output from the upper layer becomes the input for the next.
Why does light path length increase at low sun angles?
As the sun moves closer to the horizon, the angle increases the distance light travels, making extinction more pronounced.
What are Rayleigh and Mie scattering?
Rayleigh scattering occurs with small particles (d < 1/10 of the wavelength), while Mie scattering involves larger particles.
How does feedback from phytoplankton affect light extinction?
Phytoplankton absorb light and create shading, resulting in a self-limiting feedback loop.
What does Secchi disk depth measure?
It measures water clarity and is inversely related to the extinction coefficient (k).
How does total suspended solids (TSS) influence light extinction?
TSS increases turbidity and the extinction coefficient, thereby reducing water transparency.
What is the empirical relationship for light extinction in water?
- when I do an experiment or measure it myselft I use this formula:
k = b + c * [A], where [A] is the concentration of chlorophyll-a, b is background turbidity, and c is a proportionality constant.
What is the Leaf Area Index (LAI), and how is it related to light extinction?
LAI represents the total one-sided leaf area per unit ground area and influences the amount of light reaching the ground.
Can Lambert-Beer’s law be applied in terrestrial systems?
Yes, but the medium (e.g., forest canopy) is often heterogeneous, requiring adjustments for leaf orientation and species differences.
Why can Lambert-Beer’s law fail at low sun angles?
At angles greater than 60°, factors like
- atmospheric density,
- refraction, and
- cloud cover
cause deviations.
