Comparison of epiphytic diatom communities on Padina sp. during blue Haslea blooms in the Ligurian Sea and the Adriatic SeaJulie Séveno 1, Ana Car 2, Damien Sirjacobs 4, Andrzej Witkowski 3, Romain Gastineau 3, Denis Baurain 4, Pierre Lejeune 5, Sylvie Gobert 5,6, Myriam Badawi 1, Vincent Leignel 1, and Jean-Luc Mouget 1

1 Laboratoire Mer Molécule Santé (EA 2160, FR CNRS 3473 IUML), Le Mans Université, 72000 Le Mans, France
2 Institute for Marine and Coastal Research, University of Dubrovnik, Kneza Damjana Jude 12, 20000 Dubrovnik, Croatia
3 Faculty of Geosciences, Institute of Marine Sciences, University of Szczecin, Mickiewicza 16a, 70383 Szczecin, Poland
4 InBioS–PhytoSYSTEMS, Eukaryotic Phylogenomics, University of Liège, Liège, Belgium 5 STARESO Research Station, Revellata Cape, 20260 Calvi, France
6 FOCUS-Oceanology- University of Liège, Liège, Belgium

Contact: julie.seveno(@)

Diatom communities are important environmental indicators, thus knowing their diversity is essential for a better understanding of the biotope dynamics. Benthic diatoms are one of the first components in coastal trophic chains and they play a key role in nutrient cycles and sedimentary flux,1 however, they still remain poorly investigated. For instance, little is known about the epiphytic communities on Padina sp, a representative macroalgae in the Mediterranean submarine costal landscape.2 As for many other microphytic communities, biotic and abiotic parameters structure diatom assemblages.3 Padina sp. is an annual species so its epiphytic community should mainly be impacted by the current year environmental parameters.

In the frame of the H2020 GHaNA (The Genus Haslea, New marine resources for blue biotechnology and Aquaculture) program, the aim of this research project is about the development of blue Haslea blooms in some natural marine coastal environments. Blue Haslea species are pennate diatoms able to synthetize a blue-green water-soluble pigment, like marennine produced by H. ostrearia (Gaillon) Simonsen 1974. These marennine-like pigments have allelopathic, antioxidant, antiviral and antibacterial properties, as demonstrated in laboratory conditions.4–6 Benthic blooms of blue Haslea spp. occur regularly in natural environments (e.g., France, Croatia, USA, Australia). For instance, in Calvi Bay, (Corsica, France) Haslea spp. was first mentioned in spring 1996 and large biomass developments were recurrently observed during the last years. First observations of blue Haslea spp. bloom in Croatia were recorded in 2012.

Here, we analysed the changes in diatom communities developing on Padina sp. during blue Haslea spp. blooms. We explored two sites of the Mediterranean Sea, the Ligurian Sea (Calvi, Corsica) and the Adriatic Sea (Dalmatia). The species of blue Haslea involved in the blooms were identified, using morphological and molecular approaches and diatom communities on Padina sp. were determined using light and scanning electron microscopy. As investigated in previous studies on benthic diatoms in Mediterranean Sea, the main genera identified are Cocconeis, Navicula, Nitzschia, Mastogloia and Haslea. Statistical analyses are currently conducted to link environmental factors to the bloom and communities dynamics. This work represents the first study on the bloom of blue Haslea species in natural environment in open waters. It represents a key step to increase our knowledge about benthic diatom communities (diversity and ecology) in the Mediterranean Sea.

Keywords: bloom, diatom, diversity, epiphytes, Haslea, Mediterranean Sea.



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