Distribution of Alexandrium fundyense (Dinophyceae) cysts in Greenland and Iceland with an emphasis on viability and growth in the Arctic

摘要

The bloom-forming dinoflagellate Alexandrium fundyense has been extensively studied due its toxin-producing capabilities and consequent impacts to human health and economies. This study investigated the prevalence of resting cysts of A. fundyense in western Greenland and Iceland to assess the historical presence and magnitude of bloom populations in the region, and to characterize environmental conditions during summer, when bloom development may occur. Analysis of sediments collected from these locations showed that Alexandrium cysts were present at low to moderate densities in most areas surveyed, with highest densities observed in western Iceland. Additionally, laboratory experiments were conducted on clonal cultures established from isolated cysts or vegetative cells from Greenland, Iceland, and the Chukchi Sea (near Alaska) to examine the effects of photoperiod interval and irradiance levels on growth. Growth rates in response to the experimental treatments varied among isolates, but were generally highest under conditions that included both the shortest photoperiod interval (16h:8h light:dark) and higher irradiance levels (~146–366 μmol photons m⁻² s⁻¹), followed by growth under anextended photoperiod interval and low irradiance level (~37 μmol photonsm⁻² s⁻¹). Based on field andlaboratory data, we hypothesize that blooms in Greenland are primarily derivedfrom advected Alexandrium populations, as low bottomtemperatures and limited light availability would likely preclude in situ bloomdevelopment. In contrast, the bays and fjords in Iceland may provide morefavorable habitat for germling cell survival and growth, and therefore maysupport indigenous, self-seeding blooms.