Determinism of blue Haslea blooms in natural environments

• Main Author: Séveno, Julie
• Other Authors: Biologie des Organismes, Stress, Santé, Environnement Le Mans Université (BiOSSE), Le Mans Université (UM), Le Mans Université, Jean-Luc Mouget, Vincent Leignel, Myriam Badawi
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2022
• Subjects: Diatoms; Bloom; Dynamics; Taxonomy; Diatomée; Dynamique; Taxonomie; [SDV.BV]Life Sciences [q-bio]/Vegetal Biology; Northwest Atlantic
• Online Access: https://theses.hal.science/tel-04001859; https://theses.hal.science/tel-04001859/document; https://theses.hal.science/tel-04001859/file/2022LEMA1020.pdf

Benthic blooms of blue Haslea have been known since the 17th century in oyster ponds along the northwest Atlantic coast in Europe. The emblematic species Haslea ostrearia (Gaillon) Simonsen produces marennine, a water - soluble blue pigment. Other species of blue Haslea produce marennine - like pigments, which have allelopathic, antioxidant, antiviral and antibacterial properties, as demonstrated in laboratory conditions. Marennine is also responsible for the greening of oysters in the Marennes Oléron region (France), a phenomenon that has economic and patrimonial values. Until now, the dynamics and impacts of blue Haslea blooms had not been studied in open environments. Blooms have however been regularly observed in natural environments, as for example, in Spring in the bay of Calvi since 1996. These blooms have also been observed in Summer in Croatia. This thesis is the first study of the environmental parameters initiating and impacting Haslea blooms. A correlation has been observed between the beginning of Haslea benthic blooms, which follow the spring planktonic blooms. The temperature seems to have a negative impact on the bloom dynamics. The impacts of these blooms on the diatoms and bacteria inhabiting the underlying biofilm have also been investigated. These blooms have no negative impacts on their environment with no significant change in the communities observed. This study also allowed describing new species of non-blue Haslea based on a morphological and molecular taxonomic study. This thesis work has improved the knowledge on the genus Haslea and more generally on the dynamics of diatom blooms. Les blooms benthiques d'Haslea bleues sont connus depuis le 17ème siècle dans les bassins ostréicoles, le long de la côte nord-ouest de l'Atlantique en Europe. L'espèce emblématique Haslea ostrearia (Gaillon) Simonsen, produit la marennine, un pigment bleu soluble dans l'eau. Les pigments de type marennine ont des propriétés allélopathiques, antioxydantes, antivirales et anti-bactériennes, qui ont été ...