Secondary Productivity Flashcards
What is secondary production?
The amount of new zooplankton tissue elaborated per unit time
Who are secondary producers?
Zooplankton (copepods are the main group)
What regulates secondary production?
Food availability, temperature, predation
Why is determining secondary production important?
Zooplankton are the key link between the primary producers and higher tropic levels
What is tropic transfer efficiency?
An estimate for secondary productivity
What are the problems with TTE?
Assumes TTE of 10% is always a good estimate, assumes we can account for the biomass of all the unfished species in the food web
What are the problems with measuring secondary production?
Zooplankton growth is much smaller than phytoplankton growth, short-term incubations are unlikely to tell us anything, estimates need to focus on one species at a time
What are the traditional methods of measuring secondary production?
The physiologic method, cohort analysis
What is the physiologic method?
Calculated inputs and outputs, biomass grazer.
What are the problems with the physiologic method?
Very theoretical, nearly impossible to apply in field or lab settings
What is the cohort analysis method?
Theoretically secondary production=sum(weight-specific growth rate of stage i*biomass of stage i) using different stages of a zooplankton cohort
What was the one study that collected enough samples to employ cohort analysis under field conditions?
Daily production estimates for the copepod Acartia hudsonica in Jakle’s Lagooon
What are mesocosms?
Used to encircle a large volume of seawater and the plankton community withinit. Typically 2-5m across, 3-10m deep, popularized by Tim Parsons in Saanich Inlet
What is the artificial cohort method?
Incubate specific stages/size classes for short periods
What are the problems with artificial cohort method?
Repeated handling-damage, container effects (food, temperature), assumes asynchrony, time consuming and laborious
What is the chitobiase method?
The biochemical method for rapid estimation of secondary production as the amount of chitobiase release is proportional to body size
What is chitobiase?
A crustacean moulting enzyme that recycles chitin during moulting of an individual. Provides an estimate of the average development rate of the crustacean zooplankton community
What are the main advantages of the chitobiase method?
Speed and simplicity
What data is needed for the chitobiase method?
The rate of decay of chitobiase from seawater samples which requires short time incubation of filtered seawater
What is food in zooplankton used for?
Growth, reproduction, routine metabolism and respiration
How much food do zooplankton need?
Smaller zooplankton have higher weight-specific food requirements. Food required is an inverse function of size
How much of the phytoplankton do zooplankton consume?
Varies within a day, seasons, ecosystems. Usually 10-40%, occasionally 100% consumption of PP
Do copepods encounter food limiting conditions?
No, this is rarely ever found. More likely under oceanographic conditions than coastal waters. More likely to affect large copepods.
What effects zooplankton growth rate?
Temperature (proportional), younger stages (highest), threshold food concentration
What did the Huntley-Lopez model find?
Temperature alone often explained >90% of variation in copepod growth rates. Secondary Production could be estimated as B*0.0445e^0.111T
Why has the Huntley-Lopez model come under attack?
Relies mostly on lab data collected under unrealistic conditions, mode often doesn’t predict the response observed in the field
How does food quality affect secondary production?
Bioindicatiors such as fatty acids have shown food quality affect the reproductive success and development of copepods
What can affect copepod reproductive success?
Favourable DHA:EPA ratio can cause higher growth rates and reproductive success in zooplankton
