Influences of abiotic and biotic factors on biochemical composition of selected temperate macroalgae
Cara Ortega, Claudia L.
Cara Ortega, Claudia L.
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Publication Date
2023-02-27
Type
Thesis
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Abstract
Seaweeds, as a foundation species and ecosystem engineers, play an important role in nature by providing food, refuge, and habitat for higher trophic levels, and contributing significantly to primary production. In addition, they present a high economic value due to their applications across various commercial sectors. Due to the environment they inhabit, benthic algae are exposed to a complex and dynamic physico-chemical (abiotic) and biological (biotic) interactions. The vital role of natural marine microbial communities in macroalgal health, functioning and development is increasingly recognized, and the seaweed-microbial association (“holobiont”) is now considered a prospective source of bioactive chemicals. Further, there is potential to stimulate the production and/or release of interesting chemicals through exposure seaweeds to selected microbes under controlled conditions. The study aimed to characterise biochemical spatial-temporal changes in the biochemical compounds of four Irish seaweeds (Ulva sp., Chondrus crispus, Ascophyllum nodosum and Laminaria digitata) in their natural environment and to determine chemical changes in response to abiotic factors (temperature and irradiance). In addition, prior to evaluating the effect of induced microbial strains on seaweeds composition, different sterilisation techniques were developed (UV A, sodium hypochlorite and antibiotics) whilst maintaining seaweed health. Results highlight distinct species-specific patterns of seaweed-environment interactions, with pigments, mycosporine-like amino acids (MAAs) and fatty acids controlled by sampling season and location. In controlled laboratory experiments, photosynthetic pigments were mostly controlled by irradiance, and fatty acids by temperature. In addition, this study identified antibiotics as the most suitable sterilisation treatment to reduce bacteria to non-detectable levels whilst minimising seaweed stress determined by chlorophyll fluorescence. In a culture experiment using the rhodophyte C. crispus as a model species, previously sterilised seaweed thalli exposed to external microbial isolates displayed modified photosynthetic and pigment responses. The present data indicate the importance of sampling location, season, and intra thallus part when harvesting seaweeds. Additionally, information from experimental cultures could elucidate the environmental drivers to optimize biochemical compounds. Considering the holobiont concept, experimental evidence from studying the biochemical impact of exogenous infection of sterilised C. crispus provided novel information how the production of valuable compound in culture can be manipulated.
Publisher
NUI Galway