Publication Date:
2014-03-08
Description:
Algicidal and growth-inhibiting bacteria (GIB) are promising tools for mitigating the negative impacts of harmful algal blooms in coastal environments; however, there is a paucity of quantitative data describing their ecological effects. Here, we investigate their temporal and spatial distribution in the southwest Yatsushiro Sea during the summer of 2011, by co-culturing bacterial isolates with an axenic culture of a fish-killing raphidophyte Chattonella antiqua . This novel co-culturing method excludes other biological influences, such as promotion of algal growth by some bacteria. The highest density (1.6 x 10 4 cells mL –1 ) of algicidal bacteria (AB) was detected at the surface of the nearshore station on 3 August 2011 when the maximum chlorophyll a concentration was observed, associated with the high abundance of two centric diatoms, low abundance of dinoflagellates and the absence of C. antiqua . On 10 August, total bacterial abundance increased at 10 m, suggesting that the bacteria used decaying organic matter derived from dead microalgae sinking to the bottom to promote their growth. Most of AB (87.5%) were found to be particle associated, suggesting these bacteria attached to the dead phytoplankton particles after killing them. Two types of GIB impaired co-cultured C. antiqua by inducing unusual cell deformations, including round and elongated cell morphologies. Partial 16S rRNA sequencing showed that algicidal and GIB were mainly comprised of "- and a -proteobacteria". This study provides a new perspective on the dynamics of AB, suggesting that they play a significant role in regulating microalgal composition, physiology and abundance in coastal marine environments.
Print ISSN:
0142-7873
Electronic ISSN:
1464-3774
Topics:
Biology
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