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Can increases in temperature stimulate blooms of the toxic benthic dinoflagellate Ostreopsis ovata?
Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences. (Plankton Ecology)
Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences. (Plankton Ecology)
Istituto Superiore di Sanità, Rome, Italy.
University of Ruhuna, Sri Lanka.
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2011 (English)In: Harmful Algae, ISSN 1568-9883, E-ISSN 1878-1470, Vol. 10, no 2, 165-172 p.Article in journal (Refereed) Published
Abstract [en]

Ostreopsis ovata Fukuyo is an epiphytic, toxic dinoflagellate, inhabiting tropical and sub-tropical waters worldwide and also in certain temperate waters such as the Mediterranean Sea. Toxic blooms of O. ovata have been reported in SE Brazil in 1998/99 and 2001/02 and the French-Italian Riviera in 2005 and 2006. These blooms had negative effects on human health and aquatic life. Chemical analyses have indicated that O. ovata cells produce palytoxin, a very strong toxin, only second in toxicity to botulism. Increase in water temperature by several degrees has been suggested as the reason for triggering these blooms. Four laboratory experiments were performed with O. ovata isolated from Tyrrhenian Sea, Italy to determine the effects of water temperature and co-occurring algae on the cell growth and/or the toxicity of O. ovata. The cells were grown under different temperatures ranging from 16 °C to 30 °C, and cell densities, growth rates and the cell toxicities were studied. Results indicated high water temperatures (26-30 °C) increased the growth rate and biomass accumulation of O. ovata. In mixed cultures of O. ovata with other co-occurring algae, biomass decreased due to grazing by ciliates. Cell toxicity on the other hand was highest at lower temperatures, i.e., between 20 and 22 °C. The present study suggests that sea surface temperature increases resulted by global warming could play a crucial role inducing the geographical expansion and biomass accumulation by blooms of O. ovata.

Place, publisher, year, edition, pages
Elsevier , 2011. Vol. 10, no 2, 165-172 p.
National Category
Ecology
Research subject
Natural Science, Aquatic Ecology
Identifiers
URN: urn:nbn:se:lnu:diva-7041DOI: 10.1016/j.hal.2010.09.002OAI: oai:DiVA.org:lnu-7041DiVA: diva2:337830
Available from: 2010-08-09 Created: 2010-08-09 Last updated: 2014-02-25Bibliographically approved
In thesis
1. Influence of Human-induced Environmental Changes on the Physiology of the Harmful Benthic Marine Microalga Ostreopsis ovata
Open this publication in new window or tab >>Influence of Human-induced Environmental Changes on the Physiology of the Harmful Benthic Marine Microalga Ostreopsis ovata
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis focus on the influence of human-induced environmental changes on the physiology of Ostreopsis ovata; a toxic, benthic dinoflagellate, which form blooms in tropical and temperate marine waters. O. ovata produces palytoxin and ovatoxins and copious amount of mucilage, all of which have significant negative ecological impacts on the benthic ecosystems where they occur. Understanding the factors affecting O. ovata growth and toxin production is therefore of great importance if we are to understand how this species form such successful blooms. To accomplish this, growth, toxicity, carbohydrate accumulation and related physiological traits of two strains of O. ovata (one from Japanese waters and the other from Mediterranean waters) were studied in laboratory experiments. The cells were grown under the conditions simulating climate-induced changes (higher temperatures and acidification of marine waters) and eutrophication (increase of nitrogen and phosphorus in coastal ecosystems).

O. ovata showed strain-specific responses to the tested environmental changes. Higher temperatures increased growth and reduced the cell toxin quota of the Mediterranean strain while it decreased the growth and toxicity of the Japanese strain. Nutrient (nitrogen-N and phosphorus-P) sufficiency significantly increased O. ovata biomass accumulation. N deficiency markedly decreased the growth while it increased cell toxicity. Lower temperatures (20 - 25 °C) increased the particulate carbohydrate accumulation in both strains. Cell volumes, C (carbon), N and P cell quotas and atomic ratios of O. ovata were significantly higher when grown at 20 °C, than those grown at 30 °C. Acidification did not significantly affect growth and cell toxicity, but increased particulate carbohydrate accumulation. The combined effect of higher temperature and acidification delayed the onset of the blooms by 3 - 5 days, in relation to present temperature and pH conditions.

When extrapolating these results to natural marine ecosystems, it can be inferred that O. ovata occurring in lower-latitudes are growing optimally in the present climate conditions. On the other hand, the strains of O. ovata in higher-latitudes seem to have higher temperature optima than they have now at present conditions. Therefore, further expansion of O. ovata blooms is most likely possible in the warm, eutrophic coastal waters in higher-latitudes.

Place, publisher, year, edition, pages
Växjö: Linnaeus University Press, 2013
Series
Linnaeus University Dissertations, 127/2013
Keyword
Ostreopsis ovata, benthic dinoflagellate, climate change, temperature increase, nutrient enrichment, acidification, physiology, cell growth, cell toxicity, carbohydrate accumulation
National Category
Natural Sciences
Research subject
Natural Science, Aquatic Ecology
Identifiers
urn:nbn:se:lnu:diva-24901 (URN)978-91-87427-17-6 (ISBN)
Public defence
2013-04-26, Fullriggaren, Barlastgatan 11, Kalmar, 09:30 (English)
Opponent
Supervisors
Available from: 2013-04-10 Created: 2013-03-26 Last updated: 2014-02-25Bibliographically approved

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