龙须岛浪蚀花岗岩潮间带大型底栖藻类群落的季节变化模式

Seasonal variation patterns of the benthic macroalgal community in a wave-eroded granite intertidal at Longxu DAO,northwest coast of the Yellow sea

采用样方法对龙须岛浪蚀花岗岩潮间带进行了2年的生态学调查。龙须岛浪蚀花岗岩潮间带大型底栖藻类群落的种类组成存在着明显的季节变化 ,群落中最高和较高的藻类物种数量出现在4～8月 ,而最低值出现在10月份。在所有季节中红藻类群种类最为丰富 ,其次是褐藻 ,绿藻最少。群落中生物量的季节变化序列如下 :8月>10月>6月>12月>4月>2月。群落的生物量和各藻类类群的生物量的季节变化与龙须岛潮间带的海水温度变化相吻合 ,只有红藻类群的生物量在8月份略有下降。群落中大型底栖藻类的区系成分和优势种群存在着显著的季节波动或更替。总体来看 ,龙须岛浪蚀花岗岩潮间带大型底栖藻类群落的区系成分以暖温带成分为主 ,其次为冷水性成分、暖水性成分、温带成分和亚寒带成分。大型底栖藻类群落的物种丰富度指数季节变化序列依次为 :4月>6月>8月>2月>12月>10月 ,物种多样性为 :4月>6月>8月>2月>10月>12月 ,均匀度指数为 :4月>10月>2月>6月>8月>12月。龙须岛浪蚀花岗岩潮间带大型底栖藻类群落的季节变化可划分为3个季相 :“肠浒苔、珊瑚藻、石莼为优势种的冬、春季藻类群丛”、“鼠尾藻、石莼、珊瑚藻为优势种的夏季藻类群丛”和“石莼、叉枝藻、鼠尾藻为优势种的秋季藻类群丛”。

Marked differences of macroalgal floristic compositions in different seasonal communities are evident in the wave-eroded granite intertidals at LONGXUDAO,northwest coast of the Yellow Sea.The highest and higher species number in benthic macroalgal communities were found from April to August(32or33),while the lowest levels were obˉserved in October.In all seasonal communities red algae was the chief component with highest species number,brown algae ranked the second,and green algae the last.Seasonal changes in algal biomass in the communities ranked as following:August>October>June>December>April>February.Apart from the shrinkage of red algae in August when other algal communities were recording their highest levels,the biomass variations for the whole algal community,green,brown and red,coincided with surface seawater temperature in the littoral regions of Longxu Dao.Clear seasonal alternation of algal floristic elements exists in the communities of the granite intertidals at Longxu DAO.Obvious variations to algal population dominance,dominant species and community diversity can be observed in seasonal communities around the year.Species richness index was as following:April>June>August>February>December>October.Species diversity and evenness indices followed a similar trend.Through analysis,seasonal communities can be grouped into three seasonal aspects of benthic macroalgal associations:”Enteromorpha-Corallina-Ulva dominanted Winter-Spring association”,”Sargasˉsum-Ulva-Corallina dominanted Summer association”and”Ulva-Gymnogongrus-Sargassum dominated Autumn asˉsociation”.It can be concluded that the variations obtained above in benthic macroalgal communities of granite intertidals at Longxu DAO are mainly attributable to changes of seawater temperature,and to a lener extent to the unique spatial hetˉerogeneity of notches in wave-eroded granite plates and the strong action of waves there.