Doney, 2006 Nature 444: 695-696.

Behrenfeld et al., 2006 Nature 444: 752-755.

The changing ocean – Labrador SeaThe changing ocean – Labrador SeaEcosystem perspectiveEcosystem perspective

The changing ocean – Labrador SeaThe changing ocean – Labrador SeaEcosystem perspectiveEcosystem 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

The changing ocean – Labrador SeaThe changing ocean – Labrador SeaEcosystem perspectiveEcosystem 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)

The changing ocean – Labrador SeaThe changing ocean – Labrador SeaEcosystem perspectiveEcosystem 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)

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. Pmax, 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?

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

Climate change in the Labrador Sea:

Change: warmer/fresher warmer/fresher surface ocean – lessless ice/longerlonger open water (shelves), strongerstronger stratification, shallower shallower MLD, (reduced reduced winter deep mixing?), increased increased acidification

Consequence: enhancedenhanced and longerlonger production season where phytoplankton strongly light-limited – otherwise:

earlierearlier, lower magnitudelower magnitude and shorter-livedshorter-lived spring bloom, lessless summer production, smallersmaller autumn bloom and lessless export. earlier earlier zooplankton reproduction, fasterfaster development

Changes in water masses (Atlantic vs Arctic) – altered mixing, light, nutrient supply?

Species changes (e.g. increaseincrease in Atlantic temperate species, fewerfewer calcifiers)?

Changes in phytoplankton growth cycles and community composition effect grazer production and community composition

Yet, complex/unpredictable interactions and 2nd order effects. What do bio-physical models tell us?

Sustained ecosystem observations - Labrador Sea:

Seasonal growth cycles are key to understanding plankton dynamics and Seasonal growth cycles are key to understanding plankton dynamics and ecosystem structure/functionecosystem structure/function

Observational requirements: annual survey(s) supplemented with satellites, moorings, floats and gliders. How do we remotely monitor 2ndary 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), CO2, O2, pH

Biological measurements: POC & DOC, PIC (CaCO3), bacteria, chlorophyll, phytoplankton (species), zooplankton (biomass and species), sediment traps? Seabirds (CWS), marine mammals (seals and whales)?

Biophysical models

QUESTIONS?