2.3.2. Optical microscope analysis
This approach aimed to detect potential toxic phytoplankton species in the samples collected during mortality outbreaks. Preservation of 100 ml of five samples was directly implemented on site with 1% Lugol's iodine solution (final concentration) stored in the dark. Microscopic screening was achieved at the Ifremer laboratory using a counting chamber and inverted microscope (N = 5). Five other samples were collected at the same farm in 2010 and 2011 during mortality outbreaks to complete our sampling campaign and to identify more precisely certain taxa. After microscopic screening, cells were further identified using single cell PCR methodology (Auinger et al., 2008).