| Obey the LAW: Calanus finmarchicus dormancy explained |
| Slide 2 |
| Proxies for dormancy entry and exit |
| Entry: Fifth copepodid (CV) half-max proxy Dormant whenÉ CV proportion >= x-bar /2 where x-bar = average max. CV proportion over all years |
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| Exit: Emergence whenÉ 1. Adult (CVI) proportion >= 0.1 |
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| 2. Back-calculation from early copepodid appearance, using development time-temperature relationship |
| Data sources |
| AG: Anticosti Gyre, NW Gulf of St. Lawrence |
| Photoperiod at emergence and onset |
| Temperature at 5 m |
| Climatological temperature at 5 m |
| Mean chlorophyll-a, 0 – 50 m |
| 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 propose a ÒLipid-Accumulation WindowÓ hypothesis to explain observed life history patterns. | |
| Slide 11 |
| Slide 12 |
| Slide 13 |
| Lipid Accumulation Window
hypothesis: Step 1 - Conditions allowing dormancy: suppose only copepods with > 50% lipid content can enter |
| Lipid accumulation window
hypothesis: Step 2 - Temporal Filter |
| Lipid accumulation window
hypothesis: Step 2 - Temporal Filter |
| Lipid accumulation window
hypothesis: Step 3 - Predation Filter |
| Lipid accumulation window
hypothesis: Step 4 - Emergence Timing linked to Entry Emergence survival linked to entry and Env. |
| Testing the hypothesis |
| Utility of the model for this calculation |
| Growth and development are decoupled | |
| Ability to include temporally variable forcing data (food and temperature) | |
| Can include or ignore predation filter | |
| Mechanistic and physiological basis for growth and development |
| Slide 21 |
| Final Conclusions |
| Our findings for C. finmarchicus, C. pacificus and C. marshallae strongly suggest that multiple environmental factors are the likely cues for dormancy, as these copepods enter and exit dormancy over a wide range of times and conditions. | |
| Our modeling results (for C. pacificus so far) suggest that lipid accumulation (or some equivalent storage compound) is a likely player in how dormancy is triggered. | |
| OBEY THE LAW!!!! |
| Implications |
| Previous coupled 3-d physical-biological models of Calanus have forced dormancy transitions empirically using an advective-diffusive approach | |
| While these models provide diagnostic insight, they cannot be used for prediction | |
| A mechanistic, coupled IBM-physical model that tracks lipid accumulation is needed to understand and predict Calanus population responses to climate changes |