3.3. Proportion Prymnesiales of the total phytoplankton biovolume
Possible effects of Prymnesiales cells on plankton filtering organisms may be related not only to the total abundance, or the abundance of specific species, but also to the proportion of the total phytoplankton biovolume that consists of Prymnesiales cells. The proportion of large P. polylepis cells of the total phytoplankton biovolume was high in 2008 at sites BY2, BY5, BY15, BY31 and B1 ( Fig. 5a). In March 2008, at site BY15, large P. polylepis cells constituted almost 90% of the total phytoplankton biovolume. Later in April 2008, large P. polylepis cells constituted between 27 and 53% of the total biovolume at all sites. The proportion of large P. polylepis cells of the total phytoplankton biovolume was low in 2009 and close to zero in 2007 and 2010.