Secondary Productivity

Question 1

What is secondary production?

Answer 1

The amount of new zooplankton tissue elaborated per unit time

Question 2

Who are secondary producers?

Answer 2

Zooplankton (copepods are the main group)

Question 3

What regulates secondary production?

Answer 3

Food availability, temperature, predation

Question 4

Why is determining secondary production important?

Answer 4

Zooplankton are the key link between the primary producers and higher tropic levels

Question 5

What is tropic transfer efficiency?

Answer 5

An estimate for secondary productivity

Question 6

What are the problems with TTE?

Answer 6

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

Question 7

What are the problems with measuring secondary production?

Answer 7

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

Question 8

What are the traditional methods of measuring secondary production?

Answer 8

The physiologic method, cohort analysis

Question 9

What is the physiologic method?

Answer 9

Calculated inputs and outputs, biomass grazer.

Question 10

What are the problems with the physiologic method?

Answer 10

Very theoretical, nearly impossible to apply in field or lab settings

Question 11

What is the cohort analysis method?

Answer 11

Theoretically secondary production=sum(weight-specific growth rate of stage i*biomass of stage i) using different stages of a zooplankton cohort

Question 12

What was the one study that collected enough samples to employ cohort analysis under field conditions?

Answer 12

Daily production estimates for the copepod Acartia hudsonica in Jakle’s Lagooon

Question 13

What are mesocosms?

Answer 13

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

Question 14

What is the artificial cohort method?

Answer 14

Incubate specific stages/size classes for short periods

Question 15

What are the problems with artificial cohort method?

Answer 15

Repeated handling-damage, container effects (food, temperature), assumes asynchrony, time consuming and laborious

Question 16

What is the chitobiase method?

Answer 16

The biochemical method for rapid estimation of secondary production as the amount of chitobiase release is proportional to body size

Question 17

What is chitobiase?

Answer 17

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

Question 18

What are the main advantages of the chitobiase method?

Answer 18

Speed and simplicity

Question 19

What data is needed for the chitobiase method?

Answer 19

The rate of decay of chitobiase from seawater samples which requires short time incubation of filtered seawater

Question 20

What is food in zooplankton used for?

Answer 20

Growth, reproduction, routine metabolism and respiration

Question 21

How much food do zooplankton need?

Answer 21

Smaller zooplankton have higher weight-specific food requirements. Food required is an inverse function of size

Question 22

How much of the phytoplankton do zooplankton consume?

Answer 22

Varies within a day, seasons, ecosystems. Usually 10-40%, occasionally 100% consumption of PP

Question 23

Do copepods encounter food limiting conditions?

Answer 23

No, this is rarely ever found. More likely under oceanographic conditions than coastal waters. More likely to affect large copepods.

Question 24

What effects zooplankton growth rate?

Answer 24

Temperature (proportional), younger stages (highest), threshold food concentration

Question 25

What did the Huntley-Lopez model find?

Answer 25

Temperature alone often explained >90% of variation in copepod growth rates. Secondary Production could be estimated as B*0.0445e^0.111T

Question 26

Why has the Huntley-Lopez model come under attack?

Answer 26

Relies mostly on lab data collected under unrealistic conditions, mode often doesn’t predict the response observed in the field

Question 27

How does food quality affect secondary production?

Answer 27

Bioindicatiors such as fatty acids have shown food quality affect the reproductive success and development of copepods

Question 28

What can affect copepod reproductive success?

Answer 28

Favourable DHA:EPA ratio can cause higher growth rates and reproductive success in zooplankton