This consideration is critical because P. parvum is present
in a number of inland water bodies (e.g. Lakes Waco
and Somerville) and coastal areas of Texas (e.g.
Galveston Bay) where blooms do not form (Roelke et al.,
2010b; Southard et al., 2010). In the first experiment of
this study, P. parvum cell-free filtrates maintained in the
dark at 4 and 268C were acutely toxic to fish whereas
filtrates exposed to full or partial sunlight for 8 h did
not result in fish mortality (Fig. 1). In the second experiment,
toxicity to fish was completely ameliorated after
just 2 h of exposure to full sunlight (Fig. 3).