Unit:
Κατεύθυνση Βιολογική ΩκεανογραφίαLibrary of the School of Science
Author:
Apostolopoulou Natalia-Georgia
Supervisors info:
Αθηνά Οικονόμου-Αμίλλη (επιβλέπουσα), Ομότιμη καθηγήτρια, Τμήμα Βιολογίας, ΕΚΠΑ
Σοφία Σπαθάρη, Λέκτορας, Τμήμα Βιοεπιστημών και Βιολογίας ζώων ,Πανεπιστήμιο της Γλασκώβης, UK
Διονύσιος Ε. Ραΐτσος, Επίκουρος Καθηγητής, Τμήμα Βιολογίας, ΕΚΠΑ
Original Title:
Response strategies of microalgae under the effect of allelopathic chemicals from competitor species
Translated title:
Response strategies of microalgae under the effect of allelopathic chemicals from competitor species
Summary:
Studies on microalgae biomass suppression, have so far focused either on nutrient competition or potential toxicity due to allelochemical substances i.e. interference competition. Although certain microalgae species can be characterized as ‘storage strategists’ (i.e. store excess P in P-rich environments), increased nutrient storage has not been explicitly attributed to a response to interference competition by any empirical study to date. The aim of this research is to investigate the impact of interspecific chemical interactions of target species on shifts in their survival strategy and re-allocation of resources from growth to nutrient storage.
The allelopathic effect of harmful microalgae (i.e. toxin producers) has been thoroughly investigated on natural plankton communities. However, the drivers affecting coexistence and productivity beyond harmful species are still unknown. In this study, four different phytoplankton species. i.e. Thalassiosira sp., Phaeocystis sp., Tetraselmis sp. and Heterosigma akashiwo, were cultivated in monocultures. In each monoculture, only the cell-free filtrate from the other species was added. The response of each species to the filtrate of the other was examined by measuring cell number, chlorophyll-a (Chl-a), residual phosphorus (PO4) in the medium and intracellular P. A supplementary analysis of excreted metabolites (i.e. exometabolites) from the control species’ filtrate was carried out in order to interpret the cause of the indirect interactions among species.
Significantly higher Chl-a production was observed in H. akashiwo and Tetraselmis sp. under the effect of Phaeocystis sp. and Thalassiosira sp. filtrate and this was attributed to the greater Myo-inositol content found in their cell-free filtrate (i.e. excreted metabolites). Furthermore, a consistently positive and significant impact of H. akashiwo filtrate on intracellular phosphorus of all other species was detected, despite the fact that this filtrate had no higher P concentration than the other species. The only metabolite detected in H. akashiwo filtrate in higher concentration than all other species was Thiamine. However, Thiamin is an essential vitamin of algal growth and from our results it is inconclusive that this substance affected the other species’ growth. A combination of metabolomics and microalgal physiological experiments is an integrated approach to changes in microalgal biomass due to allelopathy and nutrient storage simultaneously enabling a mechanistic understanding of what controls microalgae biomass. In this way, high-value applications can be achieved within priority areas related to ecosystem and human health such as bioenergy and biotechnology.
Main subject category:
Science
Keywords:
microalgae, allelopathy, exo-metabolites, nutrient storage, intracellular phosphorus
Number of references:
103
