3.2. Abundance and distribution of P. polylepis and Prymnesiales cells
The abundance of large P. polylepis cells at the monitoring sites BY2, BY5, BY15, BY31 and B1 were high, often above 1 × 106 cells l− 1 between March and May in 2008 ( Fig. 3a). At site BY15 in the central Baltic Proper the abundance was up to 2.9 × 106 cells l− 1 in March 2008. In May, abundances between 2.9 × 106 and 3.5 × 106 cells l− 1 were recorded at BY31 and B1 in the northwestern Baltic Proper. It has previously been reported that P. polylepis cells started to slowly increase at sites B1 and BY31 already in late October 2007 although cell concentrations above 1 × 106 cells l− 1 was not reached until March 2008 ( Majaneva et al., 2012). The abundance of large P. polylepis was low or close to zero in 2007, 2009 and 2010 ( Fig. 3a).