How does plankton distribution and activity influence the variability of carbon dioxide uptake in the North Atlantic?

Ostle, Clare (2015) How does plankton distribution and activity influence the variability of carbon dioxide uptake in the North Atlantic? Doctoral thesis, University of East Anglia.

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Abstract

This study combines two invaluable datasets that have been collected on-board volunteer
observing ships to analyse the variability of the carbon dioxide (CO2) sink
in the North Atlantic at a range of spatial and temporal scales. Phytoplankton indices
collected from the continuous plankton recorder (CPR) and the concentration
of CO2 within the surface waters show that at seasonal time-scales phytoplankton
play an important role in maintaining the carbon drawdown within the northeast
Atlantic, while sea surface temperature (SST) drives the seasonal signal in CO2
flux in the subtropics. The North Atlantic remained a significant sink of CO2 between
2002 and 2013, despite strong inter-annual variability in CO2 flux that was
correlated to changes in the North Atlantic Oscillation and the influence that this
had on SST.
Discrete dissolved inorganic carbon, total alkalinity and dissolved oxygen samples
were collected during 4 voyages between April 2012 and February 2013. Using
these measurements this study successfully developed and implemented a simple
and inexpensive technique to estimate net community production in the surface
ocean, with the potential to extend coverage of such measurements over wider regions
at low cost.
Two key observations were made in the northeast Atlantic. Firstly, the increase
in SST was significantly correlated with the increase in phytoplankton colour index
measured by the CPR between 1960 and 2012, despite other micro and nanophytoplankton
counts decreasing over this time frame. This suggests that as the
surface ocean warms and stratification is enhanced, pico-phytoplankton (which
contribute to the colour index but not the phytoplankton counts) may be better
equipped to dominate the system, compared to larger species that are more nutrient
dependent. Secondly, the CO2 uptake capacity has decreased compared to the
1990s. Combined, these two results will likely have a significant impact on carbon
flux, export efficiency and ecosystem dynamics.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Environmental Sciences
Depositing User: Vailele Chittock
Date Deposited: 29 Jan 2016 09:56
Last Modified: 29 Jan 2016 09:56
URI: https://ueaeprints.uea.ac.uk/id/eprint/56866
DOI:

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