lnu.sePublications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Influence of Human-induced Environmental Changes on the Physiology of the Harmful Benthic Marine Microalga Ostreopsis ovata
Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
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 [en]
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: urn:nbn:se:lnu:diva-24901ISBN: 978-91-87427-17-6 (print)OAI: oai:DiVA.org:lnu-24901DiVA: diva2:612999
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
List of papers
1. Can increases in temperature stimulate blooms of the toxic benthic dinoflagellate Ostreopsis ovata?
Open this publication in new window or tab >>Can increases in temperature stimulate blooms of the toxic benthic dinoflagellate Ostreopsis ovata?
Show others...
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
National Category
Ecology
Research subject
Natural Science, Aquatic Ecology
Identifiers
urn:nbn:se:lnu:diva-7041 (URN)10.1016/j.hal.2010.09.002 (DOI)
Available from: 2010-08-09 Created: 2010-08-09 Last updated: 2014-02-25Bibliographically approved
2. Influence of temperature on growth, toxicity and carbohydrate production of a Japanese Ostreopsis ovata strain, a toxic-bloom-forming dinoflagellate
Open this publication in new window or tab >>Influence of temperature on growth, toxicity and carbohydrate production of a Japanese Ostreopsis ovata strain, a toxic-bloom-forming dinoflagellate
2012 (English)In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 65, no 3, 261-270 p.Article in journal (Refereed) Published
Abstract [en]

Ostreopsis ovata is a benthic dinoflagellate that produces palytoxin and its analogues.Since the end of the 1990s, toxic blooms of O. ovata have been recorded in many tropicaland temperate marine waters. These blooms often kill benthic invertebrates and cause healthproblems for humans. We hypothesize that increases in seawater temperature might induce theseblooms. A strain of O. ovata isolated from the southern coast of Japan was selected for study. O.ovata cells were exposed to 7 different temperatures from 24 to 30°C for 30 d, and growth rateswere noted. The specific growth rate was found to be highest at 25°C, next highest at 24°C andlower at 26, 28, 27, 30 and 29°C, in that order. The hypothesis that increased seawater temperaturecauses increases in growth rate was thus not supported. The cell toxicity and car bohydrate productionof O. ovata were highest at the temperature range that is optimal for cell growth. Increasesingsea surface temperature, as a result of global warming, is therefore not likely to have asubstantial effect on the bloom formation and toxicity of this Japanese strain of O. ovata.

Keyword
Ostreopsis ovata · Benthic dinoflagellate · Palytoxin · Toxicity · Climate change · Carbohydrate production
National Category
Ecology
Research subject
Ecology, Aquatic Ecology
Identifiers
urn:nbn:se:lnu:diva-18056 (URN)10.3354/ame01555 (DOI)
Available from: 2012-03-19 Created: 2012-03-19 Last updated: 2016-12-20Bibliographically approved
3. Physiological responses of Ostreopsis ovata to changesin N and P availability and temperature increase
Open this publication in new window or tab >>Physiological responses of Ostreopsis ovata to changesin N and P availability and temperature increase
2013 (English)In: Harmful Algae, ISSN 1568-9883, E-ISSN 1878-1470, Vol. 21-22, 54-63 p.Article in journal (Refereed) Published
Abstract [en]

Ostreopsis ovata is a benthic dinoflagellate that produces palytoxin and ovatoxins. Blooms of O. ovata causing human health problems and mortality of benthic fauna have been reported from many tropical and temperate marine waters. In the present study we examined the combined effects of temperature and different nutrient conditions on the biochemical composition, growth, toxicity and carbohydrate production of an O. ovata strain originating from the Tyrrhenian Sea. O. ovata cultures with N:P ratios of 1.6, 16 and 160 (N deficient, NP sufficient and P deficient, respectively) were grown at 20 °C and 30 °C. Biomass accumulation, growth rates, cell volumes, biochemical composition, cell toxicity and carbohydrate production in each treatment were studied. Results indicated that under nutrient sufficiency O. ovata biomass accumulation increased significantly compared to N and P deficiency and also that N limitation severely affected growth. The highest growth rates were recorded at 30 °C. Cellular contents and the atomic ratios of C, N and P were higher in the cells grown at 20 °C than in those grown at 30 °C. O. ovata cell volumes increased at 20 °C. N deficiency significantly increased cell toxicity. Toxicity per cell was higher at 20 °C, but per carbon was highest at 30 °C. The highest carbohydrate production was found in conditions of N deficiency and at the lower temperature.

Our study suggests that temperature increases due to global warming and nutrient enrichment of coastal waters stimulate the proliferation of O. ovata, particularly for the strains that have become adapted to warm temperate waters.

Place, publisher, year, edition, pages
Elsevier, 2013
Keyword
Ostreopsis ovata, Benthic dinoflagellate, Haemolytic activity, Temperature, Nutrient deficiency, carbohydrate production
National Category
Ecology
Research subject
Ecology, Aquatic Ecology
Identifiers
urn:nbn:se:lnu:diva-22718 (URN)10.1016/j.hal.2012.11.006 (DOI)000314553800007 ()
Available from: 2012-12-06 Created: 2012-12-06 Last updated: 2016-12-20Bibliographically approved

Open Access in DiVA

No full text

Search in DiVA

By author/editor
Vidyarathna, Nayani K.
By organisation
Department of Biology and Environmental Science
Natural Sciences

Search outside of DiVA

GoogleGoogle Scholar

Total: 198 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf