Jun SUN*, Dongyan LIU, Yongqi LI, Marine Life Science College, Ocean University of Qingdao, Qingdao, 266003, China
Abstract
The phytoplankton community changes of a mixed type red tide event of Skeletonema costatum and >Biddulphia regia was observed around Nuekuoshan in the Jiaozhou Bay (China). This study analyzed the changes of phytoplankton community structure and its causes during a two months campaign. During the campaign, 37 genera belonging to 63 species (no include 11 unclear taxa) were found in the phytoplankton community. The phytoplankton community of the campaign was predominant by Bacillariophyceae, accompanying with Pyrrophyceae, Chrysophyceae, Chlorophyceae and Cyanophyceae. The red tide event occurred from 3rd with a light grayish-brown color of seawater to 8th July, cell abundance of the red tide reached maximum 6.26 x 108 ind./m3 according to the chlorophyll a concentration of 30.72 mg/m3 on 5th July. But the chlorophyll a concentration reached its maximum of 36.35 mg/m3 at cell abundance level of 1.16 x 107 ind./m3. Two red tide causal species Biddulphia regia and Skeletonema costatum shown a different life strategy during the occurrence of the red tide. Skeletonema costatum grown more faster than Biddulphia regia, it started to increasing from 2.5 x 104 ind./m3 on 4th July to the maximum 6.2 x 108 ind./m3 on 5th July, then dropped rapidly to 1.3 x 105 ind./m3 on 6th July. This indicated that the forecasting of red tide of Skeletonema costatum is very difficult. Species succession analysis has shown that these two species were allochthonous species of the initial phytoplankton community, physical advection and decrease of salinity had heavily effect on the form of red tide.
Keywords: the Jiaozhou Bay, Red tide, Phytoplankton community, Skeletonema costatum, Biddulphia regia