Drivers of Harmful Algal Blooms in the North Sea

99 Pages·2015·2.71 MB·English

Faculty Bioscience Engineering

Academy year 2014 – 2015

Drivers of Harmful Algal Blooms in the North Sea

Effect of Global Change on future bloom development

Simon Coppen

Promotors: Prof. Dr. Colin Janssen
Prof. Dr. Ir. Karel De Schamphelaere
Tutor: Maarten De Rijcke

Master dissertation to obtain the degree of
Master in de bio-ingenieurswetenschappen: Milieutechnologie
II
Faculty Bioscience Engineering

Academy year 2014 – 2015

Drivers of Harmful Algal Blooms in the North Sea

Effect of Global Change on future bloom development

Simon Coppen

Promotors: Prof. Dr. Colin Janssen
Prof. Dr. Ir. Karel De Schamphelaere
Tutor: Maarten De Rijcke

Master dissertation to obtain the degree of
Master in de bio-ingenieurswetenschappen: Milieutechnologie
IV
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Acknowledgements

Finishing this master thesis would have been impossible without the help of a few people:

First of all, I would like to show my gratitude to my tutor Maarten De Rijcke for his incredible
patience, support and feedback. The lab has no more secrets thanks to his help and he was always
around for a good laugh. Of course, I have to thank my academic promotors professor dr. Colin
Janssen and professor dr. ir. Karel De Schamphelaere who gave me the opportunity to conduct this
research in their research department. Jan Baert, thank you for the incredible help with all the
R-code in the data analysis. It would have not been as exhaustive and good looking without your
help. Last but not least I would like to show my recognition to Francis Vanryckeghem, my lab partner
whom I performed this research with. It was a joy to work with you.

Naturally, I want to thank my parents for giving me the opportunity to study and for their support
during difficult periods. And where would I be without the help and support of my friends? Thank
you Veerle, Wout and Francis. Finally I would like to say thank you to my girlfriend Laura for her
loving support during stressful times and corrections to my final text.
Simon
August 2015

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Abstract
Harmful Algal blooms are in essence a completely natural phenomenon but can have devastating
effects: poisoning (and even death) of people, millions of euros in damage to aquaculture, decline in
tourism… HAB events have occurred in the pre-human era. Yet a strong increase in events is
recorded since the industrial revolution. Main causes of this increase are all human influences:
ballast water dispersal, eutrophication and global warming.
This research focuses on the potential bloom of a select group of North Sea dinoflagellates
(Prorocentrum micans, Prorocentrum lima, Protoceratium reticulatum, Scrippsiella trochoidea and
Alexandrium reticulatum) under elevated temperature. We tried to discover fundamental differences
between toxic and non-toxic species in acquiring dissolved nitrogen and phosphorous. To do so, the
first subject that was investigated is whether or not a change in nitrogen to phosphorus ratio would
have a differential influence on the growth of the marine dinoflagellates. Ratios were varied from 8
to 24 with the naturally occurring ratios of the North Sea in the middle (N:P of 14-18). In the other
experiment, the effects of the community composition and the initial density were investigated.
In general the effect of this varying N:P ratio was insignificant: only the carrying capacity of P. micans
was significantly influenced. This conclusion is in contrast with the widespread hypothesis that
changes in the N:P ratio can trigger a HAB event. From these experiments, it seems that nutrient
ratios are of little to no importance in a bloom initiation event. Since this does not seem to be a
correct approach, it might be more beneficial and more correct to focus the studies on real available
nutrient concentrations. This is both more comprehensive and allows for better regulations in
regards to discharges in the North Sea.
Furthermore, it is obvious from the second part of the research that interspecific competition and
starting density (seeding) play a much bigger role in the HAB occurrence, although the initial
densities of individual algae will not always determine which species will dominate a bloom. Instead,
the species composition and the allelopathic properties of each species are deemed most important.

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