FATE OF INVASION BY GREEN-TIDE FORMING SPECIES (Ulva compressa and U. procera) OFF THE SOUTHWEST COAST OF KOREA

Abstract

The occurrence of an ulvoid algal bloom resulting from anthropogenic activities is one of the annual events in the Yellow Sea. The rbcL tree shows that the identity of bloom consists of two Ulva species (U. compress and U.procera). Our phylogenetic trees based on rbcL gene sequences from drifting samples do not coincide with previous reports that a green-tide forms a clade with representatives of the Ulva linza-procera-prolifera (LPP) complex or U. prolifera. Although there was a large year-to-year variability, green algal bloom in the Yellow Sea have occurred in the past few years (2006-2009). The images of high spatial-resolution optic satellites, MODIS, Landsat, ALOS and Kompsat-2 data in spring/early summer show the extensive stripes of the green algae that cover approximately 900 &#8211

23,000 square kilometers. We collected thalli of floating U. procera from the middle of Yellow Sea in July 2009. Laboratory experiments were conducted to investigate the physiological effects of temperature (five levels), irradiance (ten levels) and salinity (five levels) on these wild thalli and their laboratorygrown progeny as well. From short-term acclimation experiments, we found that temperature did not significant impact maximum O2 production rates (PB max) or photosynthesis efficiency (α), and nor did irradiance impact photosynthetic saturation irradiance (Ek). Changes in photosynthetic rate of U. procera were observed at various salinities, showing higher rates within the salinity range of 10 and 30 psu. These results are important to understand and increase the knowledge on drift green-tide processes in the Yellow Sea.