Document Detail

Alexandrium fundyense cyst viability and germling survival in light vs. dark at a constant low temperature.
MedLine Citation:
PMID:  25076814     Owner:  NLM     Status:  Publisher    
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 mortality while in complete darkness, as they swim to illuminated surface waters. To test the validity of this assumption we conducted laboratory investigations of 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 10:14 h 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 2-week time lag in maximum germination rates compared to the light treatment. Survival of germlings was considerably lower in the dark treatment. In the 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 the cysts produced germlings that were able to survive for the same length of time. When dark treatments are scaled to take into account non-darkness related mortality, approximately 28% of the 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.
Emil Vahtera; Bibiana G Crespo; Dennis J McGillicuddy; Kalle Olli; Donald M Anderson
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Publication Detail:
Journal Detail:
Title:  Deep-sea research. Part II, Topical studies in oceanography     Volume:  103     ISSN:  0967-0645     ISO Abbreviation:  Deep Sea Res. Part II Top. Stud. Oceanogr.     Publication Date:  2014 May 
Date Detail:
Created Date:  2014-7-31     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100955507     Medline TA:  Deep Sea Res Part 2 Top Stud Oceanogr     Country:  -    
Other Details:
Languages:  ENG     Pagination:  112-119     Citation Subset:  -    
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