一座季节性休渔湖泊——洱海轮虫的季节动态特征

Seasonal dynamics of rotifer in a seasonal fishing moratorium lake — Lake Erhai,Yunnan Province,China

于2009年2-11月对洱海轮虫进行月际采样,分析洱海轮虫的多样性及其群落结构季节动态特征.洱海作为一个高原湖泊,其轮虫种类组成仍然呈现出热带-亚热带的主要特征.本研究共鉴定轮虫68种,多数种类为广布性或暖水性种类,隶属17科25属,异尾轮属、腔轮属和臂尾轮属是种类最多的三个属,占鉴定轮虫种类的37%.Lecane arcuata和Tricho-cera inermis为我国新纪录种.轮虫生物量的季节分布呈"双峰型",并分别出现在休渔期的中期和捕鱼期前期.在休渔期中期,轮虫主要以前节晶囊轮虫为优势种;在捕鱼期前期,轮虫先以螺形龟甲轮虫和广生多肢轮虫为优势,后以前节晶囊轮虫为优势.季节性休渔不仅使鱼类对轮虫的捕食压力出现季节性变化,而且还通过影响枝角类的群落结构改变枝角类对轮虫的竞争压力.在捕食和竞争的双重作用下,轮虫主要以大型杂食性种类———前节晶囊轮虫为优势种类,并呈现"双峰型"的季节分布模式.

Rotifers were sampled monthly from February to November in 2009 in Lake Erhai, Yunnan Province, China, in order to study their diversity and seasonal dynamics. Lake Erhai has a rotifer composition with tropical-subtropical characteristics： 68 spe- cies belonging to 25 genera of 17 families were identified, the majority of which were eurythermal or mesophilic. The genera of Tr/- chocerca, Lecane and Brachionus were more abundant than others, accounting for 37% of the total community. Lecane arcuata and Trichocera inermis are new records in China. Biomass of the rotifer communities in Lake Erhai exhibited a bimodal seasonal cycle. An increase occurred during spring from low winter levels to an annual maximum in the mid fishing moratorium and a second in- crease in the early fishing season. In the mid fishing moratorium, the rotifer biomass was dominated by Asplanchna priodonta; while in the early fishing season, it was dominated by the small-sized Keratella cochlearis and Polyarthra vulgaris, then by A. pr/- odonta again. The seasonal fishing moratorium affected not only the predation pressure on retifers, but also competitive pressure on rotifer through influencing the community structure of Cladocera. Through the influence of predation and competition, rotifers were dominated by large omnivorous A. pr/odonta, which showed a bimodal seasonal, distribution pattern.