Development of the Lipid Accumulation Window hypothesis to explain Calanus finmarchicus dormancy
description
Transcript of Development of the Lipid Accumulation Window hypothesis to explain Calanus finmarchicus dormancy
Development of the Lipid Accumulation Window hypothesis to explain Calanus finmarchicus
dormancy
Jeffrey RungeSchool of Marine Sciences, University of Maine and
Gulf of Maine Research Institute
Andrew LeisingNOAA, Southwest Fisheries Science Center
Catherine JohnsonUniversity of British Columbia
Objectives:
•Identify environmental processes that control dormancy in Calanus finmarchicus
•Develop a mechanistic understanding of dormancy for inclusion in population dynamics modeling
Approach:
•Compile Calanus and environmental data across regions in the NW Atlantic
•Look for common patterns and cues
•Using an individual-based model, develop quantitative hypotheses to explain patterns
Data Sources and Collaborators
Data from:
DFO – AZMP: 1999 – 2005 (E.Head, P.Pepin)
DFO – IML:1990 – 1991 (S. Plourde, P. Joly)
US-GLOBEC: 1995 – 1999 (E. DurbIn, M. Casas)
PULSE – NEC: 2003 – 2005 (R. Jones)
Proxies for dormancy entry and exit
Entry (Onset)Fifth copepodid (CV) half-max proxy
Dormant when…
CV proportion ≥ x / 2
where x = average max. CV
proportion over all years
Exit (Emergence)Emergence when…
1. Adult (CVI) proportion ≥ 0.1
2. Back-calculation from early
copepodid appearance, using
development time-temperature
relationship
Dormancy
AG: Anticosti Gyre, NW Gulf of St. Lawrence
Sta
ge P
ropo
rtio
nA
bund
ance
(no
. m
-2)
Onset
Emergence
Possible dormancy cues
OnsetPhotoperiod
(Miller et al., 1991)
Temperature(Niehoff & Hirche, 2005)
Food availability(Hind et al., 2000)
Lipid accumulation (hormonal link?)(Irigoien, 2004)
EmergencePhotoperiod
(Miller et al., 1991; Speirs et al., 2004)
Disturbance(Miller & Grigg, 1991)
Development(Hind et al., 2000)
Climatological temperature at 5 m
OnsetEmergence
Day of Year
Tem
pera
ture
(°C
)
Rimouski
Anticosti Gyre
Newfoundland
Scotian Shelf
Mean chlorophyll-a, 0 – 50 m
Chl
-a (
mg
m-3)
Rimouski
Anticosti Gyre
Newfoundland
Scotian ShelfOnset
Emergence
Day of Year
--- half-saturation [Chl-a]
Analysis of variance
F pMultiple
comparisons
Onset Year day 22.32 <0.001 S27=AG; AG=RIM
Day length 18.38 <0.001 S27=AG; AG=RIM
Temperature 8.059 <0.001 S27=AG,H2; AG=H2
Chlorophyll 2.427 0.12
Conclusions
• No single observed environmental cue explains dormancy patterns
• Dormancy entry and emergence occur over a broad range of times, both among individuals and years
The mechanistic understanding of dormancy transitions must involve interaction of multiple environmental factors.
We develop a “lipid-accumulation window” hypothesis to explain observed life history patterns.
Miller et al. 1977.Growth rules in the marine copepod genus Acartia. L&O. 22: 326-335.
Lipid accumulation window hypothesis:
• Development rate increases faster with temperature than growth rate
• Lipid production integrates temporally variable food and temperature history
•We hypothesize cue for entry occurs prior to stage CV.
• Mortality also influences probability of reaching CV dormant stage
Individuals can only enter dormancy if their food and temperature history allows them to accumulate sufficient lipid
Lipid accumulation window hypothesis:Step 1:Decision to enter dormancy in stage CV is made in stage CIV. Criterion is attainment of 30%
lipid content by wt.F
ood
inde
x
Durbin et al. 2003: Gulf of Maine Runge et al. (2006.): Georges Bank
Calanus finmarchicus: Relationship of egg production to phytoplankton biomass
Lipid accumulation window hypothesis:Step 2 - Temporal Filter
Time
Favorable Env. Conditions
Cumulative conditions that will allow dormancy in CIV and CV
Lipid Threshold
Lipid accumulation window hypothesis: Step 2 - Temporal Filter
Time
Favorable Env. Conditions
Cumulative conditions that will allow dormancy Resulting
period when they go dormant
Lipid accumulation window hypothesis: Step 3 - Emergence Timing linked to Entry
Emergence survival linked to entry and Env.
Time
Favorable Env. Conditions
JanJan
Population entering dormancy
Population exiting dormancy
Successful females
Dormancy Length, f(T during dormancy,% lipids at entry)
AG
Anticosti Gyre climatology
Anticosti Gyre
Model simulation
Observed climatology
Rimouski
Observed climatology
Model simulation
Next Steps
• Work on parameters for model for C. finmarchicus; development of general set for all of NW Atlantic
• Test LAW model against C. finmarchicus life cycle data sets in the NW Atlantic. Does the model reproduce variability in individual years?
• Test refined and alternative hypotheses- Additional conditions required?
• Examine mechanisms for emergence from dormancy: parameterization of Saumweber and Durbin functions for potential diapause duration
• Examine influence of climate change scenarios on Calanus life cycle and population dynamics
• Further testing with time series observations, include measures of lipid levels in CIV and CV