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Dinophysis blooms in the deep euphotic zone of the Baltic Sea: do they grow in the dark?

Gisselson, L Å; Carlsson, Per LU ; Graneli, E and Pallon, Jan LU (2002) In Harmful Algae 1(4). p.401-418
Abstract
In situ growth rates of the toxin-producing dinoflagellate Dinophysis norvegica collected in the central Baltic Sea were estimated during the summers of 1998 and 1999. Flow cytometric measurements of the DNA cell cycle of D. norvegica yielded specific growth rates (μ) ranging between 0.1 and 0.4 per day, with the highest growth rates in stratified populations situated at 15–20 m depth. Carbon uptake rates, measured using 14C incubations followed by single-cell isolation, at irradiances corresponding to depths of maximum cell abundance were sufficient to sustain growth rates of 0.1–0.2 per day. The reason for D. norvegica accumulation in the thermocline, commonly at 15–20 m depth, is thus enigmatic. Comparison of depth distributions of... (More)
In situ growth rates of the toxin-producing dinoflagellate Dinophysis norvegica collected in the central Baltic Sea were estimated during the summers of 1998 and 1999. Flow cytometric measurements of the DNA cell cycle of D. norvegica yielded specific growth rates (μ) ranging between 0.1 and 0.4 per day, with the highest growth rates in stratified populations situated at 15–20 m depth. Carbon uptake rates, measured using 14C incubations followed by single-cell isolation, at irradiances corresponding to depths of maximum cell abundance were sufficient to sustain growth rates of 0.1–0.2 per day. The reason for D. norvegica accumulation in the thermocline, commonly at 15–20 m depth, is thus enigmatic. Comparison of depth distributions of cells with nutrient profiles suggests that one reason could be to sequester nutrients. Measurements of single-cell nutrient status of D. norvegica, using nuclear microanalysis, revealed severe deficiency of both nitrogen and phosphorus as compared to the Redfield ratio.



It is also possible that suitable prey or substrate for mixotrophic feeding is accumulating in the thermocline. The fraction of cells containing digestive vacuoles ranged from 2 to 22% in the studied populations. Infection by the parasitic dinoflagellate Amoebophrya sp. was observed in D. norvegica in all samples analysed. The frequency of infected cells ranged from 1 to 3% of the population as diel averages, ranging from 0.2 to 6% between individual samples. No temporal trends in infection frequency were detected. Estimated loss rates based on observed infection frequencies were 0.5–2% of the D. norvegica population daily, suggesting that these parasites were not a major loss factor for D. norvegica during the periods of study. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Harmful Algae
volume
1
issue
4
pages
401 - 418
publisher
Elsevier
external identifiers
  • scopus:0242403509
ISSN
1878-1470
DOI
10.1016/S1568-9883(02)00050-1
language
English
LU publication?
yes
id
fbdde65a-e359-4ba2-b704-51939a2abe0a (old id 149870)
date added to LUP
2007-06-28 13:17:25
date last changed
2017-01-08 04:01:19
@article{fbdde65a-e359-4ba2-b704-51939a2abe0a,
  abstract     = {In situ growth rates of the toxin-producing dinoflagellate Dinophysis norvegica collected in the central Baltic Sea were estimated during the summers of 1998 and 1999. Flow cytometric measurements of the DNA cell cycle of D. norvegica yielded specific growth rates (μ) ranging between 0.1 and 0.4 per day, with the highest growth rates in stratified populations situated at 15–20 m depth. Carbon uptake rates, measured using 14C incubations followed by single-cell isolation, at irradiances corresponding to depths of maximum cell abundance were sufficient to sustain growth rates of 0.1–0.2 per day. The reason for D. norvegica accumulation in the thermocline, commonly at 15–20 m depth, is thus enigmatic. Comparison of depth distributions of cells with nutrient profiles suggests that one reason could be to sequester nutrients. Measurements of single-cell nutrient status of D. norvegica, using nuclear microanalysis, revealed severe deficiency of both nitrogen and phosphorus as compared to the Redfield ratio.<br/><br>
<br/><br>
It is also possible that suitable prey or substrate for mixotrophic feeding is accumulating in the thermocline. The fraction of cells containing digestive vacuoles ranged from 2 to 22% in the studied populations. Infection by the parasitic dinoflagellate Amoebophrya sp. was observed in D. norvegica in all samples analysed. The frequency of infected cells ranged from 1 to 3% of the population as diel averages, ranging from 0.2 to 6% between individual samples. No temporal trends in infection frequency were detected. Estimated loss rates based on observed infection frequencies were 0.5–2% of the D. norvegica population daily, suggesting that these parasites were not a major loss factor for D. norvegica during the periods of study.},
  author       = {Gisselson, L Å and Carlsson, Per and Graneli, E and Pallon, Jan},
  issn         = {1878-1470},
  language     = {eng},
  number       = {4},
  pages        = {401--418},
  publisher    = {Elsevier},
  series       = {Harmful Algae},
  title        = {Dinophysis blooms in the deep euphotic zone of the Baltic Sea: do they grow in the dark?},
  url          = {http://dx.doi.org/10.1016/S1568-9883(02)00050-1},
  volume       = {1},
  year         = {2002},
}