象山港游泳动物群落功能群组成与功能群多样性

FUNCTIONAL GROUP COMPOSITION AND FUNCTIONAL DIVERSITY OF NEKTON COMMUNITY IN THE XIANGSHAN BAY

依据2011年4月、7月和11月象山港水域桁杆拖网和单拖网渔业资源定点调查资料,对象山港水域游泳动物群落的功能群组成及功能群多样性特征进行了系统研究。依据摄食习性,本文将调查海域出现的96种游泳动物划分为7个功能群,其中底栖动物/游泳动物食性、游泳动物食性、底栖动物食性和腐屑食性功能群是该水域的优势功能群。相似性分析检验结果显示:不同季节象山港游泳动物群落的功能群结构保持相对稳定,不存在显著性季节差异。4月、7月和11月该水域游泳动物群落的功能群多样性均值分别为1.303、1.261和1.185,亦未呈现显著性季节差异。功能群多样性指数与大个体生物(体重大于50g)的总重量资源密度显著正相关;功能群多样性与物种多样性的关系可用斜率为0.463、截距为0.266的线性方程进行描述,这表明该水域物种多样性的大量丧失可能引起功能群多样性的降低。象山港水域部分功能群所含物种数明显偏少,冗余度较低,在强大的外界干扰下,某些重要物种的衰退可能将使该水域功能群多样性显著降低。

A functional group is a group of species that occupy the same niche in ecology and share resources in a similar way. In the concept of functional group, we simplify the structure and dynamics of nekton community to examine the energy flow and biomass within food webs in the Xiangshan Bay based on the data collected from beam-trawl and single-trawl surveys in April, July, and November of 2011. In terms of feeding habit, seven functional groups were identified: planktivores, planktivores/benthivores, benthivores, benthivores/piscivores, omnivores, piscivores, and detritivores. Similarity analysis revealed that there was no significant seasonal difference in structure of nekton community at functional group level. Benthivores/piscivores, benthivores, piscivores, and detritivores were dominant in biomass of the nekton community. The functional diversity in the bay was 1.303 in April, 1.261 in July, and 1.185 in November, with no significant monthly difference. A strong positive relationship was revealed between functional diversity and total biomass of these individuals whose body weights exceed 50g. A linear relationship between species and functional diversity could be well described in regression. In addition, the number of species in some given functional groups was small, indicative of a low level of functional redundancy. Currently, under the intense fishing pressure, some commercially important species might extinct locally, which might further lead to the removal of the whole functional group from the bay and irreversible degradation of ecosystem functions.