1. Doney, 2006 Nature 444: 695-696. Behrenfeld et al., 2006 Nature 444: 752-755. The changing ocean – Labrador Sea Ecosystem perspective

2. The changing ocean – Labrador Sea Ecosystem perspective  An understanding of the dynamics of ecosystems and their response to a changing ocean climate starts with the realization that the generation times of plankton at the base of the foodweb are on the order of days to months  Thus, a meaningful observation program must capture seasonal growth and production cycles

3. The changing ocean – Labrador Sea Ecosystem perspective C-cycle (i.e. feedbacks to climate system – efficiency of “biological pump”)  biogenic-C inventories  production (surface) / respiration (column) balance  DOM production / fate (“twilight zone” 100-1000m)  vertical biogenic-C flux (organic & carbonate) Local ecosystem processes:  seasonal cycles  productivity  community structure  trophic-interactions Large-scale ecosystem processes:  “Regime-Shifts” (individual species, populations)

4. The changing ocean – Labrador Sea Ecosystem perspective Environmental changes (light, temp, nutrition, substrate):  atmospheric changes (clouds, fog, winds)  rising temperatures  decreasing ice  changing upper ocean mixing increasing freshwater changing density structure  water-mass changes (transport in/out/downstream)  Increasing acidification Lower trophic-level changes:  timing, magnitude and duration of growth/reproductive cycles  community structure  food supply (primary producers) Higher trophic-level changes:  Habitat  food supply (secondary producers)

5. Climate change impacts - phytoplankton: Our observations to date: warmer temperatures, less ice or earlier ice retreat leads to earlier blooms Direct effects: Temperature (higher)  Altered metabolic rates, e.g. P max, respiration (differential: R>P)  Changes in community composition (shift to smaller species)  Thermal boundaries = abrupt ecosystem changes Ice (less)  Altered photosynthetic rates and seasonal cycles  Changes in community composition (epontic versus pelagic), C-export? Ocean Acidification (lower pH)  Changes in community composition (reduced calcifiers), C-export? Indirect effects: Vertical density structure (warmer-fresher) Shallower mixed-layer depth (light environment)  Altered photosynthetic rates and seasonal cycles, C-export?  Changes in community composition, C-export? Stronger stratification (nutrient environment)  Altered nutrient supply  Altered photosynthetic rates and seasonal cycles, C-export?  Changes in community composition, C-export? Large-scale circulation (as it affects local phys & chem environment)  Altered seasonal cycles and community composition, C-export?

6. Climate change impacts - zooplankton: Our observations to date: warmer temperatures lead to earlier appearance of young Calanus stages due to faster development rates and earlier reproduction - related to earlier phytoplankton blooms Direct effects: Temperature (higher)  Altered metabolic rates  Changes in community composition  Altered seasonal cycles (phenology) Ice (less)  Altered seasonal cycles (via food supply)  Changes in community composition (epontic versus pelagic) Ocean Acidification  Changes in community composition (reduced calcifiers) Indirect effects: Vertical density structure (warmer-fresher) Shallower mixed-layer depth (via food supply)  Altered seasonal cycles  Changes in community composition Stronger stratification (via food supply)  Altered seasonal cycles  Changes in community composition Large-scale circulation (as it affects local phys environment and food supply)  Altered seasonal cycles and community composition

7. Climate change in the Labrador Sea: warmer/fresher lesslongerstronger shallower reduced increased Change: warmer/fresher surface ocean – less ice/longer open water (shelves), stronger stratification, shallower MLD, (reduced winter deep mixing?), increased acidification enhancedlonger Consequence: enhanced and longer production season where phytoplankton strongly light-limited – otherwise:  earlierlower magnitudeshorter-lived  earlier, lower magnitude and shorter-lived spring bloom,  less  less summer production,  smaller  smaller autumn bloom and  less  less export.  earlier faster  earlier zooplankton reproduction, faster development Changes in water masses (Atlantic vs Arctic) – altered mixing, light, nutrient supply? increasefewer Species changes (e.g. increase in Atlantic temperate species, fewer calcifiers)? Changes in phytoplankton growth cycles and community composition effect grazer production and community composition Yet, complex/unpredictable interactions and 2 nd order effects. What do bio-physical models tell us?

8. Sustained ecosystem observations - Labrador Sea: Seasonal growth cycles are key to understanding plankton dynamics and ecosystem structure/function Observational requirements: annual survey(s) supplemented with satellites, moorings, floats and gliders. How do we remotely monitor 2 nd ary producers? Supplementary physical measurements or derived products: ice, T&S, density structure (MLD, stratification, eddies), large-scale transport (Atlantic vs Arctic) Supplementary chemical measurements: primary nutrients (N, P, Si), CO 2, O 2, pH Biological measurements: POC & DOC, PIC (CaCO 3 ), bacteria, chlorophyll, phytoplankton (species), zooplankton (biomass and species), sediment traps? Seabirds (CWS), marine mammals (seals and whales)? Biophysical models

9. QUESTIONS?