Characteristics of Calanus finmarchicus dormancy patterns in the northwest Atlantic
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Characteristics of Calanus finmarchicus dormancy patterns in the northwest Atlantic
GLOBEC NWA 4B SI meeting, Woods Hole, 29 Oct 2007
Catherine Johnson Fisheries and Oceans, Bedford Institute of Oceanography
Andrew LeisingNOAA, Southwest Fisheries Science Center
Jeffrey RungeSchool of Marine Sciences, U. of Maine and Gulf of Maine Research Institute
Erica HeadFisheries and Oceans, Bedford Institute of Oceanography
Pierre Pepin Fisheries and Oceans, Northwest Atlantic Fisheries Centre
Stéphane Plourde Fisheries and Oceans, Institut Maurice Lamontagne
Edward DurbinGraduate School of Oceanography, University of Rhode Island
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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, test quantitative hypotheses to explain patterns
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Data sourcesData 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)
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Proxies for dormancy entry and exitEntry (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
B. Zakardjian
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AG: Anticosti Gyre, NW Gulf of St. Lawrence
Sta
ge P
ropo
rtion
Abu
ndan
ce (n
o. m
-2)
Onset
Emergence
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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)
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Onset of dormancy ANOVA
Parameter Equal variance? F p Multiple comparisons
Onset
Year day Y 22.32 <0.001 NS≠LSLE,SS; AG≠SS; LSLE≠SS
Day length N 18.38 <0.001 NS≠LSLE,SS; AG≠SS; LSLE≠SS
Temperature at 5m Y 8.059 <0.001 NS≠LSLE,SS; AG≠LSLE,SS
Chlorophyll a (0–50 m) N 2.427 0.12
NS, Newfoundland Shelf; AG, Anticosti Gyre; LSLE, lower St Lawrence estuary; SS, Scotian Shelf.
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Climatological temperature at 5 m
OnsetEmergence
Day of Year
Tem
pera
ture
(°C
)
Rimouski
Anticosti Gyre
Newfoundland
Scotian Shelf
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Mean chlorophyll-a, 0 – 50 m
Log(
chl-a
(mg
m-3))
Rimouski
Anticosti Gyre
Newfoundland
Scotian ShelfOnset
Emergence
Day of Year
--- half-saturation [Chl-a]
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Emergence from dormancy ANOVA
Parameter Equal variance? F p Multiple comparisons
Emergence
Year day N 54.68 <0.001 AG ≠LSLE; LSLE≠SS
Day length N 119.2 <0.001 NS≠LSLE; AG≠LSLE; SS≠LSLE
NS, Newfoundland Shelf; AG, Anticosti Gyre; LSLE, lower St Lawrence estuary; SS, Scotian Shelf.
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Dormancy duration is not related to deep water temperature during
dormancy
Dormancy duration is inversely related to surface temperature at
onset
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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.The lipid accumulation hypothesis is a possible multiple-factor dormancy control mechanism.
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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 • An additional cue acting prior to stage CV may be required • Mortality also influences probability of reaching CV stage
Individuals can only enter dormancy if their food and temperature history allows them to accumulate sufficient lipid
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Calanus IBM overview
Egg
N1-2N3
N4-6C1-3C4C5
C5Female
diapauseDVM
Non-feeding
ForagingBehavior
The model groupingsGrowth rate, G:G = gmax * Food / (ks + Food)Where, gmax = b + m*ln (T)b and m are empirically fit*Development rate, R:R = Ω* a (T + b) -2.05 a and b are empirically fitWhere Ω is a penalty function that decreases development rate at extremely low food levelsMortality:Each stage has a fixed mortality rate (decreasing logarithmically by stage)Copepods also die if their age within stage is greater than that predicted at their minimum allowable T
*Data for empirically fit parameters from Campbell et al. (2001), Vidal (1980), and/or Peterson (1986), depending on species
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Lipid accumulation window hypothesis:Decision to enter dormancy in stage CV is made in stage
CIV. Criterion is attainment of 30% lipid content by weightFo
od in
dex
(rel
ativ
e to
hal
f-sa
tura
tion
cons
tant
)
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Model objective
Identify a dormancy response that allows the model to simulate the seasonal cycle at all stations using the same parameters.
Run IBM at four stations using
- Climatological temperature and food conditions of each station
- Same parameters and dormancy response at all stations
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Anticosti Gyre
Model simulation
Observed climatology
males
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Rimouski
Observed climatology
Model simulationmales
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Next Steps• 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 metabolic limitation of diapause duration (Saumweber and Durbin, 2006)
• 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
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Individual-based model
Lipid fraction(i.e. the fraction of food that goes to lipid)
FL = Fmax*Prey/(Ksf+prey)
Fmax is the maximum fraction of food that can be allocated to lipidKsf is a half saturation constant, which is different from Ks
*There is a threshold below which FL = 0
EmergenceCopepods develop at a reduced rate during dormancy (1/25th). They emerge either
at the end of the slow CV stage or when lipid levels decline to 10%.