BIOVADIA

Biodiversity and Valorisation of blue Diatoms

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 Obiettivo del progetto (Objective)

'This program aims to increase our knowledge about the biology and biodiversity of ‘blue diatoms’, unique among microalgae by their ability to produce specific water-soluble bluish pigments. Up to now the terms ‘blue diatoms’ have referred exclusively to the pennate marine diatom Haslea ostrearia, and to its blue pigment, the so-called marennine, a polyphenolic molecule with biological activities, which is produced during algal growth and ageing. In oyster ponds of western France, H. ostrearia may year on year become dominant, and marennine released in the seawater is responsible for the ’greening’ of oysters, a phenomenon which has a noticeable local economical impact. The diatom H. ostrearia has long been considered the only microalga ever known, worldwide in distribution, to produce marennine. Indeed in the literature, diatoms with blue tips described as H. ostrearia were reported in almost all seas and oceans in northern and southern hemispheres. Their presence was deduced either directly from the observation of living cells, or indirectly from a greening effect of bivalves. In most cases, a careful identification of the ‘blue diatoms’ at the species level did not rely on detailed studies of morphology and morphometrics. This paradigm has been recently questioned following the discovery, in phytoplanktonic samples taken on rocky shores of Crimea (Ukraine), of diatoms presenting similarities with H. ostrearia, with bluish apices, but in which the pigment seemed different from marennine. Preliminary results indicate that these diatoms could be two different species, which raises a concern about occurrences of ‘blue diatoms’ and their identification as H. ostrearia in all other marine environments. Hence the present project is aiming to deepen our knowledge of the biology, physiology and pigments of ‘blue diatoms’, to study their biodiversity, and to unravel their taxonomy, especially regarding the genus Haslea.'

Introduzione (Teaser)

Oysters cultivated in the Bay of Biscay make a valuable contribution to the local economy, with gourmets paying a premium for 'green oysters'. The microscopic marine algae responsible for the colouring are the subject of an EU-funded initiative.

Descrizione progetto (Article)

The 'Biodiversity and valorisation of blue diatoms' (http://biovadia.univ-lemans.fr/fr/index.html (BIOVADIA)) project is investigating the biology and biodiversity of blue diatoms, a form of microalgae. Researchers are investigating their specific blue pigments as well as their taxonomy, focusing on their position within the genus Haslea. The consortium comprises partners from Canada, France, Ukraine, the United Kingdom and the United States.

Haslea ostrearia, the first blue diatom ever described, is well known for its water-soluble blue pigment, marennine, which is responsible for producing green oysters. In addition to changing the oysters' colour, the greening also makes the flesh sweeter and tastier. This phenomenon gives the famous emerald green-tinged oysters of western France, which are of economic importance to the region.

Project partners collect and identify blue diatoms from different geographical areas. New species of marennine-producing diatoms have been found and described with the aid of morphometrics (the analysis of their structure) and molecular genetic markers. Researchers also investigate the way in which the diatoms' physiology is adapted to their environment, including their life cycle and how they reproduce.

Methods for extracting and purifying the blue pigments are improved by the consortium. A study of their biological properties (antioxidant, antiproliferative) has been conducted in order to increase understanding of these extraordinary biomolecules and how they can be used economically. Antibacterial and antiviral activities have also been evidenced, which could be helpful for counteracting the severe mortality events observed in cultured bivalves, in particular mussels and oysters.

BIOVADIA will help scientists gain a better understanding of marennine-type pigments and blue diatoms. This will improve the cultivation of green oysters and their contribution to Europe's economy, while enabling gourmets to continue enjoying their tasty treat.