The influence of ocean acidification and species shifts on algal exudate production: Case study Alexandrium minutum, Protoceratium reticulatum, Phaeodactylum tricornutum
Van de Weyer, N. (2024). The influence of ocean acidification and species shifts on algal exudate production: Case study Alexandrium minutum, Protoceratium reticulatum, Phaeodactylum tricornutum
. MSc Thesis. Ghent University, Faculty of Bioscience Engineering: Gent. 104 pp.
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Document type: Dissertation
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| Keywords |
Alexandrium minutum Halim, 1960 [WoRMS]; Phaeodactylum tricornutum Bohlin, 1897 [WoRMS]; Protoceratium reticulatum (Claparède & Lachmann) Bütschli, 1885 [WoRMS]
Marine/Coastal |
| Abstract |
In this research, three algal species—the diatom Phaeodactylum tricornutum and the dinoflagellates Alexandrium minutum and Protoceratium reticulatum—were exposed to different levels of acidification in their growth medium. The objective was to investigate the impact of ocean acidification, a consequence of climate change, on their growth and exudate production. The study quantified 2 classes of exudates: Extracellular Polymeric Substances (EPS) through an extraction method followed by Bradford reagent colouring and Transparent Extracellular Particles (TEP), a planktonic subclass of EPS, by staining with Alcian Blue. Understanding how environmental changes affect EPS production is vital, as EPS plays a key role in the structure and functionality of microbial biofilms, aiding in surface adhesion and providing a protective buffer for organisms. The protein content in EPS is particularly important for these functions. Therefore, ATR spectra were also used to determine the protein-to-carbohydrate (P/C) ratio over time and compare it across different pH treatments (pH 8.10, pH 7.80, and pH 6.37). The impact of ocean acidification on TEP production is also important to understand since this will impact the vertical carbon flux in the marine water column. The findings illustrate that cell density measurements under varying pH conditions revealed species-specific responses: Phaeodactylum tricornutum showed increased growth at moderate acidification compared to severely acidified or normal conditions, while Alexandrium minutum and Protoceratium reticulatum displayed varied but insignificant growth rate changes. EPS production generally increased under acidified conditions, with species-specific trends (logarithmic, linear, exponential). TEP production initially rose at lower pH levels but later decreased, except for Protoceratium reticulatum. EPS quality, characterized by protein-to-carbohydrate ratio, also showed species-specific responses to pH changes. No clear conclusions could be drawn however, due to the big interspecies variability and a lot of hiatuses still present in the used methodology, making statistical analysis hard at times. |
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