Laboratory experiments on the physiological response of members of the nanophytoplankton to temperature and light limitation and nutrient saturation were conducted in order to investigate if nanophytoplankton conforms to Plankton Functional Types (PFTs) for modelling purposes. This thesis concluded that nanophytoplankton does not follow all of the assumed physiological traits. The Q10 estimates for members of the nanophytoplankton are considerably lower than Eppley, and since nanophytoplankton does not follow the Eppley curve at warmer temperatures, the results suggest that the Eppley assumptions cannot be used to describe nanophytoplankton. μmax0 is used as a temperature physiological modelling parameter (as well as Q10) which are components of the exponential and linear fits. However, nanophytoplankton best fits to an optimum function which uses μopt, Topt and dT as model parameters. These results are in contrast to the Eppley assumptions. Using a dynamic photosynthesis model five phytophysiological parameters were derived including the maximum photosynthesis rate (Pcm,), respiration rate (resp), the initial slope of the line (achl), light inhibition (βchl) and the maximum chlorophyll to carbon ratio (θmax). These parameters were estimated using an acclimated model which used the instantaneous rates of photosynthesis to estimate the other parameters. The acclimated model gave the best fit (AIC = -3.75 vs. = -0.95). These results are in contrast to those used for PFT modelling purposes. Parameters are comparable for Pcm, resp and θmax but showed significant differences for αchl and βchl the latter of which was underrepresented in the dynamic model, and the former of which is used as a model parameter for PFT parameterization. Chlorophytes had stronger light inhibition (mean βchl= 0.72 g C m2 (mol photons g Chl α)-1) than haptophytes (mean βchl = 0.34 g C m2 (mol photons g Chl α)-1). βchl is significantly lower for haptophytes (P = 0.002). Members of the nanophytoplankton showed relatively high μmax (0.81 d-1 from the acclimated model fit) and mean photosynthesis rates 1.8 Pcm (d-1) mean cell volume 37 μm3). Maximum growth rates increased with increasing cell volume for all of the species. Members of the nanophytoplankton alter their elemental stoichiometry and assimilated nutrients in excess of their requirements but as a PFT, there were no statistically significant deviations from Redfield. Under nutrient replete conditions Chl α:C increased linearly with increasing temperature and increased linearly with decreasing light. Overall, these results suggest that further physiological data is required in order to parameterize models to estimate nanophytoplankton physiological responses to climate change.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:687908 |
| Date | January 2015 |
| Creators | Fôch-Gatrell, Siân |
| Publisher | University of East Anglia |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://ueaeprints.uea.ac.uk/59615/ |
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