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Growth and Saxitoxin Production by Cylindrospermopsis raciborskii (Cyanobacteria) Correlate with Water Hardness
Institute of Biophysics Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro 21949-902, RJ, Brazil
These authors contributed equally to this work.
* Author to whom correspondence should be addressed.
Received: 13 June 2013; in revised form: 20 July 2013 / Accepted: 30 July 2013 / Published: 15 August 2013
Abstract: The cosmopolitan and increasing distribution of Cylindrospermopsis raciborskii can be attributed to its ecophysiological plasticity and tolerance to changing environmental factors in water bodies. In reservoirs in the semi-arid region of Brazil, the presence and common dominance of C. raciborskii have been described in waters that are considered hard. We investigated the response of a Brazilian C. raciborskii strain to water hardness by evaluating its growth and saxitoxin production. Based on environmental data, a concentration of 5 mM of different carbonate salts was tested. These conditions affected growth either positively (MgCO3) or negatively (CaCO3 and Na2CO3). As a control for the addition of cations, MgCl2, CaCl2 and NaCl were tested at 5 or 10 mM, and MgCl2 stimulated growth, NaCl slowed but sustained growth, and CaCl2 inhibited growth. Most of the tested treatments increased the saxitoxin (STX) cell quota after six days of exposure. After 12 days, STX production returned to concentrations similar to that of the control, indicating an adaptation to the altered water conditions. In the short term, cell exposure to most of the tested conditions favored STX production over neoSTX production. These results support the noted plasticity of C. raciborskii and highlight its potential to thrive in hard waters. Additionally, the observed relationship between saxitoxin production and water ion concentrations characteristic of the natural environments can be important for understanding toxin content variation in other harmful algae that produce STX.
Keywords: cyanobacteria; saxitoxins; paralytic shellfish poisoning; water hardness; ionic effect; growth
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MDPI and ACS Style
Carneiro, R.L.; Pacheco, A.B.F.; de Oliveira e Azevedo, S.M.F. Growth and Saxitoxin Production by Cylindrospermopsis raciborskii (Cyanobacteria) Correlate with Water Hardness. Mar. Drugs 2013, 11, 2949-2963.
Carneiro RL, Pacheco ABF, de Oliveira e Azevedo SMF. Growth and Saxitoxin Production by Cylindrospermopsis raciborskii (Cyanobacteria) Correlate with Water Hardness. Marine Drugs. 2013; 11(8):2949-2963.
Carneiro, Ronaldo L.; Pacheco, Ana B.F.; de Oliveira e Azevedo, Sandra M.F. 2013. "Growth and Saxitoxin Production by Cylindrospermopsis raciborskii (Cyanobacteria) Correlate with Water Hardness." Mar. Drugs 11, no. 8: 2949-2963.