Study on the tempo-spatial distribution of green macroalgal micro-propagules along the coasts of Jiangsu and Shandong provinces

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To study the tempo-spatial distribution and species succession of green macroalgal micro-propagules in the coastal waters affected by the green tides in the Yellow Sea, a year-round survey was conducted at the four stations (ZGS, YWG, LSG and YY) along the coasts of Jiangsu and Shandong provinces. Through the lab-culture and molecular analysis, there were six green macroalgal species detected, including 4 ulvoid species (Ulva linza, U. prolifera, U. compressa and U. pertusa), an unclassified Ulva sp. and one Blidingia sp. Quantitative analyses revealed evident tempo-spatial variations of the abundance and species composition of micro-propagules at the four stations. The abundances of micro-propagules were significantly higher at ZGS and YY than those at YWG and LSG. A seasonal bi-peak pattern of the abundances was consistent throughout the four stations. The numbers of micro-propagules were generally highest during the spring to early summer, and reached a minor peak in fall, but were low in other seasons. The U. prolifera propagules (77 individuals/L in average over the year) were existing at ZGS of the Subei Shoal throughout the year, and majority (75.7% in average) of them was the ‘floating’ type, an ecotype causing the green tides in the Yellow Sea. In comparison, species composition of micro-propagules fluctuated significantly at YY of Qingdao. The dominant species switched from U. linza to U. prolifera in summer when the large-scale floating biomass of U. prolifera approached the coasts of Qingdao. The quantity of ‘floating’ type of U. prolifera increased dramatically in this period and descended rapidly with the cessation of the green tide. This study suggested that the Subei Shoal is an important ‘habitat’ for U. prolifera, which plays a crucial role in maintaining the U. prolifera population and causing the successive green tides. Whereas in Qingdao coastal water, the large-scale floating U. prolifera biomass could temporarily influence the local micro-propagule community, and cause a rapid shift of the micro-propagule species during the blooming season of the green tides.