2012). Hence, there is an urgent need to understand the mechanisms underlying the outbreak of red tides, which is significant in developing effective management strategies to control them. However, the outbreak mechanisms of red tides are very complex and are not fully understood (Cai et al. 2013). In particular, no satisfactory explanations have been provided to explain why some microalgal species are replaced in a phytoplankton community. Recent studies have shown that the forming of red tides can be dependent on multiple physical, chemical, meteorological and biological factors, such
as wind, water current, disturbance, temperature, salinity, nutrient availability, Forskolin purchase predation of zooplankton, and so on (Smayda, 1997, Laanaia et al., 2013 and Persson PD-332991 et al., 2013). Allelopathy, a widely existing natural phenomenon, refers to any direct or indirect, inhibitory and stimulatory effects of plants or microorganisms on others, by producing
chemical compounds that are released into the environment (Rice, 1984 and Meiners et al., 2012). It is believed to be a competitive strategy to adapt to the environment (Cummings et al. 2012). Allelopathy is not a contributory factor towards the formation of harmful algal blooms, but may be important in the maintenance of these blooms (Jonsson et al. 2009). For a long time, research on allelopathy concentrated on terrestrial higher plants (Feng et al., 2010 and Khan et al., 2012). The existing published research work
on allelopathy in marine microalgae is somewhat limited (Addisie & Medellin 2012). Understanding the allelopathic interactions in marine microalgae can provide deeper insight into successions in natural algal communities and outbreak mechanisms of harmful algal blooms (Legrand Ergoloid et al., 2003 and Żak et al., 2012). The dinoflagellate Prorocentrum donghaiense is an ecosystem-harmful algal bloom species that frequently occurs in Chinese coastal waters ( Hu et al. 2012). For instance, in May 2002 a large-scale P. donghaiense causative bloom formed in the East China Sea. It lasted for about one month, and the affected area was larger than 1000 km2; it had significant negative impacts on the aquatic environment, marine fisheries and even public health ( Lu et al. 2005). Meanwhile, the phytoplankton organism Phaeodactylum tricornutum is a marine diatom. Under certain environmental conditions, it can also over-proliferate in coastal waters, with the potential to destroy the natural marine ecosystems in the vicinity, and hence to cause great losses to the economy ( Cai et al. 2009). However, until now no report has been available on the allelopathic interactions between the disruptive P. donghaiense and P.