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Title: Growth dynamics and physiology of paralytic shellfish toxin producing dinoflagellates
Author: John, E. H.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 1999
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Studies on the growth dynamics and physiology of the paralytic shellfish toxin producing dinoflagellates Alexandrium fundyense, A. minutum and Gymnodinium catenatum were conduced under a number of different nutrient regimes, light, temperature and salinity levels. G. catenatum was very slow to respond to N-refeeding, with relatively low internal amino acid concentrations, a low glutamine:glutamate ratio, and a stable toxin content, showing little variation with N- and P-limitation or with decreased salinity. In contrast Alexandrium sp. respond to N-refeeding with an increased internal amino acid pool, an increased glutamine: glutamate ratio, especially with ammonium as a N-source, and an increased toxin content. P-limitation in A. fundyense leads to a significant increase in the toxin content but only when cells are also N-limited. Sub-optimal temperature and light levels lead to decreased growth rates: low temperature results in larger cells and an increased toxin content in A. fundyense, whilst the effect of low light on A. minutum cells varies with the N-source available. The N-uptake kinetics of G. catenatum revealed that the maximum uptake rates (Vmas) and half-saturation constants (Ks) for transport were higher for ammonium when compared with nitrate. In A. funyense values of Ks were similar at 1 μM for both nitrate and ammonium whilst Vmax for the latter was up to 5-times greater. A. fundyense was shown to be able to utilize organic-N in the form of dissolved free amino acids. Maximum uptake rates of 0.85 pmol cell-1 h-1 occurred during exponential growth and differed from the uptake capabilities of other phytoplankton in that uptake was not enhanced by N- or C-stress. A preliminary model is presented and is capable of simulating the relationship between N-refeeding and P-limitation and cellular toxin content in Alexandrium sp.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available