Spectral Properties of Marennine-like Pigments Reveal Minor Differences Between Blue Haslea Species and Strains

Marennine is the specific bluish pigment produced by the marine diatom <i>Haslea ostrearia</i> Gaillon (Simonsen), responsible for the greening of oysters in France's Atlantic coast. For decades, <i>H. ostrearia</i> was considered the only blue diatom and described as such. However, new blue <i>Haslea</i> species have been described recently, among which <i>Haslea karadagensis</i> Davidovich, Gastineau, and Mouget (Black Sea, Crimea, Ukraine); <i>Haslea provincialis</i> Gastineau, Hansen, and Mouget (Mediterranean Sea, southern France)<i>; Haslea silbo</i> Gastineau, Hansen, and Mouget (West Atlantic Ocean, USA); and one not characterized yet, <i>Haslea</i> sp. nov., isolated in Tenerife (Spain). These species produce marennine-like pigments, for which little information is available yet. The present work aims at studying spectral characteristics of these pigments by UV-visible spectrometry, Raman spectrometry, infrared spectrometry, nuclear magnetic resonance, energy-dispersive X-ray spectroscopy, and cyclic voltammetry, and comparing them to those of marennine produced by <i>H. ostrearia</i> strains originating from the north Atlantic Ocean (western France and Macaronesia), and north Pacific Ocean (southwestern USA). Results show that marennine produced by <i>H. ostrearia</i> strains and marennine-like pigments produced by <i>H. provincialis</i>, <i>H. silbo</i>, and <i>Haslea</i> sp. nov. are quite similar regarding their polysaccharide skeleton, and absorption in the UV-visible, infrared, and Raman regions. The most different marennine-like pigment is produced by <i>H. karadagensis,</i> but all <i>Haslea</i> blue pigments studied so far belong to the same family of organic molecules.