Publication Date:
2022-05-26
Description:
Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 103 (2014): 112–119, doi:10.1016/j.dsr2.2013.05.010.
Description:
Both observations and models suggest that large-scale coastal blooms of Alexandrium fundyense in the
Gulf of Maine are seeded by deep-bottom cyst accumulation zones (“seed beds”) where cysts
germinate from the sediment surface or the overlying near-bottom nepheloid layers at water depths
exceeding 100 m. The germling cells and their vegetative progeny are assumed to be subject to modest
mortality while in complete darkness as they swim to illuminated surface waters. To test the validity of
this assumption we investigated in the laboratory cyst viability and the survival of the germling cells
and their vegetative progeny during prolonged exposure to darkness at a temperature of 6°C,
simulating the conditions in deep Gulf of Maine waters. We isolated cysts from bottom sediments
collected in the Gulf of Maine under low red light and incubated them in 96-well tissue culture-plates
in culture medium under a 10:14h light: dark cycle and under complete darkness. Cyst viability was
high, with excystment frequency reaching 90% in the illuminated treatment after 30 days and in the
dark treatment after 50 days. Average germination rates were 0.062 and 0.038 d-1 for light and dark
treatments, respectively. The dark treatment showed an approximately two-week time lag in maximum
germination rates when compared to the light treatment. Survival of germlings was considerably lower
in the dark treatment. In light treatments, 47% of germinated cysts produced germlings that were able to survive for 7 days and produce vegetative progeny, i.e. there were live cells in the well along with an
empty cyst at least once during the experiment. In the dark treatments 12% of cysts produced germlings
that were able to survive. When dark treatments are scaled to take into account non-darkness related
mortality, approximately 28% of cysts produced germlings that were able to survive for at least 7 days.
Even though cysts are able to germinate in darkness, the lack of illumination considerably reduces
survival rate of germling cells. In addition to viability of cysts in surface sediments and the near-bottom
nepheloid layer, survivability of germling cells and their vegetative progeny at aphotic depths is an
important consideration in assessing the quantitative role of deep-coastal cyst seed beds in bloom
formation.
Description:
E. Vahtera was funded by the Academy of Finland (grant #130934) and B. Gomez-Crespo was
supported by a Xunta de Galicia Ángeles Alvariño fellowship. Additional funding support was also
provided by the National Oceanic Atmospheric Administration ECOHAB program through grants
NA06NOS4780245 and NA09NOS4780193 and from National Science Foundation grants OCE-
0430724 and OCE-0911031 and National Institute of Environmental Health Sciences grant 1P50-
ES01274201 through the Woods Hole Center for Oceans and Human Health.
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
Format:
application/pdf
Permalink
