Lecture 7 Flashcards
Where are algae most abundant?
At the deep chlorophyll maxima. This is where they are neat the THERMOCLINE and can obtain enough light and nutrients
Where is the meta zooplankton ideal position?
At the deep chlorophyll laxima (as that’s where the algae is)
Explain seasonal algae distribution
- in winter there’s not huge amounts of algae as light is limiting
In spring sunlight becomes more available so spring blooms occur
In summer over predation causes a drop in algae populations
When they recover in late summer they undergo a second bloom
What is the clear water phase?
The drop in algae populations during summer
Which are the edible and inedible algae blooms?
The spring bloom is classed as edible
The late summer bloom begins as edible but progresses to inedible
Why does the summer bloom progress from edible to inedible?
The edible summer bloom is limited by phosphorous.
Diatoms become the prominent species (because of their high efficiency) but because they require silica, silica then become limiting
Cyanobacteria become the next dominant species, and are classed as non edible
How do zooplankton act during the winter algae famine
Cladocereans and Rotifera do reproduce sexually due to unfavourable conditions
Copepods go in DIAPAUSE
What are the triggers for zoopllankton wake up/hatch in spring?
- food concentration
- food quality
- temperature
What is a food threshold density?
The lowest food concentration required to produce a positive growth rate of the population
How does threshold density relate to growth rate?
The greater the threshold density of the population, the greater it’s growth rate
Why do copepods wake up first?
Their nauplius have six stages of development, so they wake up to avoid competition
