Effect of theenvironmental change on the temperate marine plantscommunities at the southern distributional limit

九州岛是众所周知的日本温带海藻和海草的最南端。有人担心，气候变化引起的沿海环境的持续变化可能会推动该区域物种组成的变化。本研究的重点是确定16种温带植物在其南部分布范围内的群落特征。此外，利用溶氧传感器和脉冲幅度调制叶绿素荧光仪测定了这些物种和9种食用红藻的光合作用表现，从而确定了它们的耐温性。这些树种的净光合速率在超过28℃时显著下降。当温度超过这些温度时，各物种的最大量子产额(Fv/Fm)和相对电子传递速率(Retr)也下降。鹿儿岛湾的最高海水温度在30℃左右，表明海水温度的进一步升高可能会影响其光合作用活性，从而导致群落的退化。

Kyushu Island is known as the southernmost limit for commonly known temperate seaweeds and seagrass in Japan. There isconcern that continued changes in the coastal environment caused by climate change may drive shifts in species composition in this region. This study focused on determining the commnunity characteristics of 16 temperate species at their southern distributional limit. Furthermore, temperature tolerance of these species and 9 edible red algae were determined by examining photosynthetic performances using the dissolved oxygen sensors and pulse amplitude modulated-chlorophyll fluorometers. Net photosynthetic rates of these species significantly decreased at more than 28℃. Maximum quantum yield (Fv/Fm) and relative electron transport rate (rETR) of each species also decreased at temperatures beyond these temperatures. Highest seawater temperature in Kagoshima Bay was around 30℃, suggesting that further increase in seawater temperature might influence its photosynthetic activity and contribute to the degradation of the community.