1. Secondary Productivity
Dr. Jason Turner
MARE 444

3. Secondary Production
Secondary production, however, is harder to measure, due to longer generation times, patchiness, and smaller populations

4. Secondary Production
Using primary production figures and our knowledge of trophodynamics
Indirect - we need to know how much energy is transferred to each successive trophic level

5. Food Webs and Trophic Dynamics

6. Ecological Efficiency
The amount of energy extracted from the lower trophic level divided by the energy supplied to the upper trophic level
Hard to measure - can be estimated by the transfer efficiency

7. Food chains and energy transfer
Rather, rates of production (productivity) are more important
Chaetognaths in Hilo Bay
Standing stock of phytoplankton don’t get above 4x whale stock, although x biomass is needed to support whales

8. Generation Times
Phytoplankton (h-d), zooplankton (w-m), small fish (m-y), marine mammals and large fish (y-d)

9. DOM and POM Sloppy feeding, molting, waste generation
Detritus (detritivores)
Microbial loop
Nutrient regeneration

11. Phytoplankton Growth How can you measure growth? productivity
cell counts versus time

12. Phytoplankton Growth

13. Modeling Phytoplankton Growth
Maximum rate of photosynthesis
Light attenuation/compensation
Nutrient Concentration

14. Modeling Phytoplankton Growth
Grazing rate
Change in grazing rate versus phytoplankton concentrations

15. Transfer Efficiency Et = transfer efficiency
Pt = productivity at trophic level t
Pt-1 = productivity at lower trophic level
Et = Pt/Pt-1
*not all organisms are eaten - some die by other causes (and support the detritus cycle)

16. Transfer Efficiency ~20% from phytoplankton to herbivores
10-15% thereafter
Energy losses between trophic levels amount to 80-90%, mainly respiration

17. How many trophic levels?
Number of trophic levels is dependent on the size of phytoplankton (WHY?)
phytos tend to be large in upwelling regions (WHY?) and small in open ocean areas (WHY?)

19. Estimating Secondary Productivity
P(n+1) = P1En
P is productivity at the (n+1)th trophic level
n is number of trophic transfers (trophic levels minus one)
P1 is annual primary production
E is ecological efficiency

20. First Name: Mister, Last Name E

21. Webs & Chains
a linear sequence that reveals which organisms consume which other organisms in an environment
– a more complicated diagram of feeding interactions often involving multiple food chains

22. Productivity Measuring productivity
numbers or biomass often measured as gC/m2/yr = average 100 gC/m2/yr
rates of growth (or excretion, grazing, sinking, etc.)
organism interactions with the environment and/or each other

23. Consumer - Food Interactions

24. Match-Mismatch Hypothesis
Interannual variation in larval survival could be explained by the match or mismatch between the timing of the production cycle and the peak of spawning time e.g., - Cushing, Mertz & Myers, Pope et al.

25. Productivity For primary productivity For secondary productivity
growth rate varies with light, nutrients, and temperature
loss rate includes respiration, grazing, sinking, and death
For secondary productivity
growth rate varies with ingestion of food
loss rate includes respiration, egestion, excretion, and death

26. Grazing
Grazing can have no impact, prevent a bloom, or terminate a bloom (depending on timing)
90% of carbon and energy is lost at each step of trophic pyramid
material loss due to respiration, DOC, and POC
DOC and POC utilized by microbial loop, detritivores, etc.

27. Global Patterns of Productivity
Fish production

32. Bottom-Up Estimates
eutrophic systems (PP>>grazing)
HABs/selective grazing
In such cases, excess primary production may enter the microbial-detritus circuit

33. Top-Down Estimates
omission of production of competing, unharvested species

34. Zooplankton Productivity
B = Xw
B = biomass, X = number of individuals, w = average weight of an individual

35. Zooplankton Productivity
Pt = (X1-X2)((w1+w2)/2) + (B2 - B1)
Pt = production between time intervals t1 and t2
B2 - B1 refers to increase in biomass
the remainder of the equation refers to biomass produced, but lost, during the time interval

36. Zooplankton Productivity
cohort = one identifiable generation of progeny of a species
Practically impossible to do
cannot follow and sample same water mass long enough to get meaningful results

37. Zooplankton Productivity

39. Zooplankton Productivity
rates vary over the course of a year
in temperate regions, growth will be greatest in the spring when food is plentiful and zooplankton are young
productivity may be negative in the winter as individuals utilize food reserves rather than eating

40. Long-term Changes Long-term climate changes (regime shifts)
El Niño? NAO? PDO?
Zooplankton interactions
calanoid copepods being replaced by echinoderm larvae as main Z group in NA