AME 43:289-302 (2006)  -  doi:10.3354/ame043289

ABSTRACT: Dinoflagellate parasites, e.g. Parvilucifera infectans Norén et Moestrup, 1996 can potentially control dinoflagellate blooms and thereby modify plankton communities and nutrient fluxes. Parvilucifera infectans has been detected in Swedish waters, but its distribution is largely unknown. Based on 18S rRNA sequences of 2 P. infectans isolates of different geographic origin (Sweden and Tasmania), we designed 2 primer pairs for specific PCR amplification of rRNA fragments from these parasites. We screened for presence of P. infectans in a salinity gradient along the Swedish coastline (2 to 30‰, 13 stations) from June to August 2004. Parasites were only detected in July and August at 3 stations in the region with highest salinity (Skagerrak). Presence of parasites was correlated with high abundances of dinoflagellate hosts (Prorocentrum spp., Ceratium spp.) but was also restricted to warm and saline waters. In addition, these stations were characterized by low bacterial abundances, low chl a and low nutrient levels. Parasites were not detected in this region in June, when temperatures were lower (<15°C) and microzooplankton predators were most abundant. Hence, our study reveals both temporal and spatial patchiness of P. infectans in coastal waters.

KEY WORDS: Parvilucifera infectans · Eukaryotic parasite · 18S rRNA probe · Dinoflagellate · Harmful algal bloom · Skagerrak · Öresund · Baltic Sea