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