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

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

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)

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

AG: Anticosti Gyre, NW Gulf of St. Lawrence

Sta

ge P

ropo

rtion

Abu

ndan

ce (n

o. 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)

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.

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

Log(

chl-a

(mg

m-3))

Rimouski

Anticosti Gyre

Newfoundland

Scotian ShelfOnset

Emergence

Day of Year

--- half-saturation [Chl-a]

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.

Dormancy duration is not related to deep water temperature during

dormancy

Dormancy duration is inversely related to surface temperature at

onset

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.

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

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

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

)

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

Anticosti Gyre

Model simulation

Observed climatology

males

Rimouski

Observed climatology

Model simulationmales

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

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%.