Future of PP Flashcards
Variability in Production
Production changes include past variability, contemporary shifts and potential future changes driven by OA, nutrient supply changes and stratification
Phyto as indicators of global change
Phytoplankton act as sensitive indicators, reflecting changes from short-term climatic events (e.g., ENSO) to large-scale global alterations.
Key studies include Behrenfeld et al. (2006) and Boyce et al. (2010), which document their importance in the carbon cycle.
Has Oceanic PP changed in the past
Early oceans had no primary production.
Primary producers drove atmospheric oxygenation, significantly altering ocean chemistry and ecosystems.
Changes in primary producers over time
Major shifts in dominant primary producers have occurred through Earth’s history.
The majority of carbon fixation has historically occurred in oceans.
Glacial iron hypothesis
Proposed by John Martin, the hypothesis links increased iron inputs during glacial periods to enhanced ocean productivity and reduced atmospheric CO2.
Paleo studies confirm correlations between iron fluxes, organic material export, and nutrient usage during glacial periods.
Contemporary inter-annual changes
ENSO events drive significant variability in phytoplankton biomass and productivity.
El Niño conditions suppress productivity through thermocline deepening, while La Niña enhances productivity via nutrient upwelling.
Anthropogenic changes
Factors such as rising temperatures, increased nutrient inputs, and declining pH (ocean acidification) alter ocean productivity.
Evidence of human impacts includes increased eutrophication in coastal zones and shifts in open-ocean nutrient cycles.
OA impacts on phytos
Calcifying organisms like coccolithophores are most affected by ocean acidification, though impacts vary widely across species and regions.
Observed responses range from negative to positive growth changes in experiments.
Coastal eutrophication
Anthropogenic nutrient inputs increase coastal productivity, leading to eutrophication in many systems.
This disrupts nutrient cycles and ecosystem balance.
Opean ocean nutrient inputs
Atmospheric deposition of anthropogenic nutrients is approaching the scale of natural nitrogen fixation.
This alters nutrient availability and productivity in open-ocean systems.
Stratification
Ocean stratification, driven by warming, reduces nutrient mixing and availability.
Models predict a decline in primary production at low latitudes due to stronger stratification.
Modelling phyto dynamics
Models incorporate growth rates and losses to simulate phytoplankton population dynamics.
Complex models consider multiple nutrients, phytoplankton types, and zooplankton interactions.
Model Predictions
IPCC-class models suggest increased stratification will reduce primary and export production, particularly at low latitudes.
Predictions vary significantly, especially for high-latitude systems.
Are ocean deserts expanding
Evidence suggests oligotrophic regions (low-nutrient areas) may be expanding.
Longer time series are needed to confirm whether this is a result of anthropogenic changes or natural variability.
Is change happening
Observational evidence indicates declines in phytoplankton biomass (~1% per year).
However, these findings remain controversial and require consistent long-term monitoring for confirmation.
