东海亚强真哲水蚤种群生态特征

Ecological characters of the Eucalanus subcrassus population in the East China Sea

根据1997～2000年东海23°30′～33°N、118°30′～128°E海域4个季节海洋调查资料,运用多种生态学指标和方差贡献等统计方法对东海亚强真哲水蚤(Eucalanussubcrassus)自然种群特征及动力学进行了研究,并与1979～1980年资料进行比较。结果表明:东海亚强真哲水蚤丰度和优势度有明显的季节变化,丰度均值分别为秋季5.40indm3>夏季2.09indm3>冬季0.93indm3>春季0.17indm3。该种在东海的优势性主要表现在夏秋季。春季该种丰度占桡足类总丰度的百分比仅为2.46%,秋季为9.32%,冬季为8.42%,夏季(9.94%)是四季中的最高值。秋季该种在东海有很高的出现率(98.22%),春季较低,仅为49.62%。该种群聚集强度丛生指标(I)均为正值,其中秋季最高,有明显的聚集现象。亚强真哲水蚤对桡足类总丰度的贡献,在夏冬季仅次于中华哲水蚤(Calanussinicus),秋季仅次于精致针刺水蚤(Euchaetaconcinna)。比较20a前同水域的调查结果,该种在东海浮游桡足类中的重要性近年有所提高,尤其在秋冬季特别显著,这可能与全球变暖相关。底层水环境的变化是影响东海亚强真哲水蚤种群数量变化的主要因子,该种数量变化与暖流势力有密切的关系,是一个暖水种。

Data presented in this paper were obtained during four cruises conducted in the East China Sea （23°30′～33°N, 118°30′～128°E） during four different seasons from 1997 to 2000. Ecological characters of the population of a copepod, Eucalanus subcrassus in the East China Sea was analyzed using different methods, such as ecological index and the variance contribution analysis, and further compared with the historical data of 1979 ～ 1980. Results show a clear seasonal pattern of the E. subcrassus with an abundance on average： autumn （5.40 ind/m^3） 〉 summer （2.09 ind/m^3） 〉 winter （0.93 ind/m^3） 〉 spring （0.17 ind/ m^3）. The dominance of E. sttbcrassus also changed seasonally with the same tendency as its abundance, autumn （0.10） 〉 summer （0.08） 〉 winter （0.07） 〉 spring （0.01）. As a dominant species of copepods in the East China Sea, E. sttbcrassus predominated in summer and autumn. The percentages of the E. subcrassus in total abundance of copepods were 9.94% in the summer and 9.32% in the autumn, respectively, compare to the lowest （2.46%） in the spring. Occurrence was the highest （98.22%） in the autumn, then the winter （84.62%） and the lowest （49.62%） in the spring. E. subcrassus was the second dominant species in copepods in the summer, fall and winter. Its contributions to total abundance of copepods （β） in summer and winter were 0.39 and 0.27, respectively, following Calanus sinicus （0.88 and 0.45）, and 0.46 in autumn that was only lower than Euchaeta concinna （0.56）. In thespring, the occurrence was very low. Another character, indices of clumping （Ⅰ） of E. subcrassus in four seasons were positive. The index was higher in autumn and summer. In spring, E. subcrassus mainly distributed at the Taiwan Strait where water temperature was higher than other zones. As water temperature rose, E. subcrassus moved toward north and distributed widely in waters where water temperature and salinity were higher than 24.0℃ and 32.5‰, respectively, from summer to autumn. The variation of its abundance was associated to bottom water temperature, which was only temperature-dependent in spring and summer, surface and bottom salinity as well as bottom temperature related in autumn, and neither temperature nor salinity associated in winter. Comparison between the data presented in this paper and the data obtained from 1979 ～ 1980 indicates that the average abundance of E. subcrassus in 1997 was 10 times higher than in 1979; the dominance and percent in total abundance of copepods in 1997 was higher than in the autumn, winter and summer of 1979 ; the occurrence in the winter and autumn of 1997 also was higher than in 1979, but in the spring. This phenomenon might be related to global warming, because the bottom water temperature and salinity, the key environmental factors that affect the abundance of E. subcrassus was closely related to warm current. The close relationship between the abundance variation of E. subcrassus and warm current in the sea suggests that E. subcrassus is a warm water species in the East China Sea.