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Facilitation of DON on population growth of Alexandrium sp. in Daya Bay |
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Abstract Population dynamics of Alexandrium sp. and DON were investigated in aquaculture areas of Daya Bay from January to December in 2008 while environmental factors including nutrients, water temperature and salinity were investigated simultaneously. The concentration of DON was higher from April to June than that in other months. The maximum value for DON was 21.27μmolN/L while the annual average value was 7.44μmol N/L. Urea was one of the most important components of DON. The annual average concentration of urea was 1.98μmol N/L which represented about 20%~30% of DON. DFAA fluctuated significantly ranging from 1 to 5μmol N/L. Cell densities of Alexandrium sp. were found higher from April to June than those in other months. Alexandrium sp. bloom was observed in Aotou aquaculture area with the highest cell density of 3319 cells/mL on April 21. The concentrations of DON and urea and the cell density of Alexandrium sp. peaked synchronously, and DON and urea fell sharply to 23.84% and 62.86% of the maximum when the bloom attenuated. Significant correlations were revealed between cell density of Alexandrium sp. and environmental factors representing the extent of organic pollution such as DON, urea and CODMn. The increase of DON favored the growth of some harmful algal species and may play key roles in the formation of blooms provided suitable water temperature and salinity.
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Received: 30 June 2011
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