Notable physiological responses such as toxicity and sinking rates of the red tide forming raphidophyte Heterosigma akashiwo are correlated with high levels of macronutrient stress. Individual cells of this species are also capable of forming benthic vegetative cysts that overwinter in marine sediment and contribute to bloom propagation in subsequent seasons. It was hypothesized that there is variability in the rates of sinking within cell cultures and that sinking cells are more toxic than the neutrally buoyant or floating cells. Using laboratory-based settling columns, various isolates of H. akashiwo were allowed to separate, and the toxicities of sinking and floating populations were analyzed. Sinking and floating rates were significantly higher during the late stationary growth phase for all isolates. For two H. akashiwo isolates, sinking populations were significantly more toxic than those that were positively buoyant. A similar trend was observed in a third strain, however the relationship was not significant. Differences in adaptive ecophysiology among the different strain likely caused the variation. It is suggested that the most toxic cells within a bloom are those found at the lower depths, potentially interacting with the benthic community or ensuring that subsequent bloom propagation contains cells with the potential for toxicity. (C) 2011 Elsevier By. All rights reserved.
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South African Inst Aquat Biodivers, ZA-6140 Makhanda, South Africa
Rhodes Univ, Dept Biochem & Microbiol, ZA-6140 Makhanda, South AfricaSouth African Inst Aquat Biodivers, ZA-6140 Makhanda, South Africa
Matcher, Gwynneth
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Lemley, Daniel A.
Adams, Janine B.
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Nelson Mandela Univ, Bot Dept, ZA-6031 Port Elizabeth, South Africa
Nelson Mandela Univ, Inst Coastal & Marine Res, ZA-6031 Port Elizabeth, South Africa
Nelson Mandela Univ, DSI NRF Res Chair Shallow Water Ecosyst, ZA-6031 Port Elizabeth, South AfricaSouth African Inst Aquat Biodivers, ZA-6140 Makhanda, South Africa
机构:
Univ South Carolina, Belle W Baruch Inst Marine & Coastal Sci, Charleston, SC 29412 USA
Marine Resources Res Inst, South Carolina Dept Nat Resources, Charleston, SC 29412 USA
CUNY, Adv Sci Res Ctr, Grad Sch, New York, NY 10031 USADelaware Dept Nat Resources & Environm Control, Sagamiko, Kanagawa 19901, Japan
Greenfield, Dianne, I
Doll, Cameron
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Marine Resources Res Inst, South Carolina Dept Nat Resources, Charleston, SC 29412 USADelaware Dept Nat Resources & Environm Control, Sagamiko, Kanagawa 19901, Japan
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Natl Res Inst Fisheries & Environm Inland Sea, Red Tide Res Div, Hiroshima 7390452, JapanNatl Res Inst Fisheries & Environm Inland Sea, Red Tide Res Div, Hiroshima 7390452, Japan
Nagasaki, K
Yamaguchi, M
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Natl Res Inst Fisheries & Environm Inland Sea, Red Tide Res Div, Hiroshima 7390452, JapanNatl Res Inst Fisheries & Environm Inland Sea, Red Tide Res Div, Hiroshima 7390452, Japan