About this Research Topic
The North Atlantic plankton bloom is among the most remarkable biological events occurring on our planet and its re-occurrence every year has significant ecological, biogeochemical and climate consequences. As such, processes regulating phytoplankton blooms have been a core interest of oceanography for over a century.
The traditional paradigm for the formation of the spring bloom assumes that phytoplankton concentration decreases in parallel with growth rate during autumn and winter as a consequence of light and temperature-limited growth. The bloom is then envisioned to begin when phytoplankton division exceeds a threshold ‘critical’ rate in response to elevated nutrient concentrations and increased light in a shallowing mixed layer. Accordingly, this “resource-based view” predicts that a warmer ocean will yield larger and/or earlier blooms.
A diverse set of global to local observations have recently challenged this century long paradigm, indicating instead that phytoplankton blooms reflect subtle imbalances in predator-prey interactions instigated by climate forcing that, coincidently, also control availability of surface nutrients. Specifically, predator-prey coupling is linked to accelerations and decelerations in phytoplankton division rates due to a short temporal lag between changes in phytoplankton biomass and changes in grazing (and other loss) rates. In addition, physical disturbances can compound impacts on the balances between growth and loss rates of phytoplankton. This explains why accumulation rates are positive and depth integrated biomass begins to accumulate in late autumn when physical processes (convective mixing) and light limitation are greatest. At this time, the deepening of the mixed layer disrupts the balance between growth and mortality allowing for the build-up of phytoplankton biomass in the water column. This ‘ecosystem-based view” envisages that a warmer future ocean may be associated with a decrease in mixed-layer-integrated phytoplankton biomass during early periods of spring stratification.
Atmospheric aerosols are another key player currently limiting our ability to predict future changes in global climate. These particles act as cloud condensation nuclei (CCN) to form clouds that alter Earth radiation balance and therefore climate. Aerosol-cloud interactions remain the single largest uncertainty in current Intergovernmental Panel on Climate Change estimates of global radiative forcing. Relative contributions of various cloud-forming aerosols exhibit a strong seasonal association with ocean biological activity. Understanding how the availability and properties of atmospheric aerosols change in relation to the characteristics of the annual spring bloom will provide essential information for parameterizing ecosystem-atmospheric earth system models necessary to improve our predictions of future change in climate.
Here our overarching goal is to foster an interdisciplinary forum aimed at resolving key mechanisms underlying the annual plankton bloom in the North Atlantic and consequences for biogenic air/sea exchange and marine cloud formation and properties.
Suggested topics include (but are not limited to):
- Inter-annual variability in the timing of the spring bloom maximum
- Consequences of phytoplankton biomass and community composition on gaseous and aerosol emissions.
- Influence of marine ecosystems on marine aerosol concentration, composition and propensity to initiate cloud formation
- Annual patterns in phytoplankton biomass accumulation
- Seasonal trends in phytoplankton mortality
- Spatial and temporal scales of biophysical interactions
- Contrasting mechanisms in other ocean basins
Keywords: Marine Ecology, Biophysical Interactions, Pelagic Ecosystems, Biology-atmosphere Interactions, Physical Forcing
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