杭州湾北部大型无脊椎动物群落结构

Community structure of macroinvertebrates in northern Hangzhou Bay

为研究杭州湾北部海域大型无脊椎动物群落结构及其变化,根据2016年2月、5月、8月和11月于杭州湾北部进行的桁杆拖网调查数据,利用相对重要性指数、多元统计和ABC曲线等方法对该海域大型无脊椎动物的种类组成、优势种及群落结构特征进行研究。结果显示,杭州湾北部共出现大型无脊椎动物22种,隶属4纲5目15科18属,十足目(Decapoda)所占种类数比例最高,达77.3%,其次为狭舌目(Stenoglossa),占比仅为9.1%。调查海域共出现5种优势种,分别是葛氏长臂虾(Palaemon gravieri)、太平洋长臂虾(Palaemon pacificus)、安氏白虾(Exopalaemon annandalei)、黑龙江河篮蛤(Potamocorbula amurensis)和三疣梭子蟹(Portunus trituberculatus)。其中,安氏白虾为四季优势种,葛氏长臂虾为冬季、春季和秋季优势种。CLUSTER聚类和非度量多维标度显示,杭州湾北部大型无脊椎动物群落在44%相似性水平下可分为2个群组,Ⅰ组为冬春组,Ⅱ组为夏秋组,组间差异系数达到57.76%。ANOSIM显示群组间差异极显著(R=0.4,P<0.01)。BIOENV表明,杭州湾北部大型无脊椎动物群落结构与温、盐度组合的相关性最高,相关系数为0.39。研究表明,杭州湾北部大型无脊椎动物群落结构较为简单,优势种以小型虾类为主,群落结构的季节变化显著。群落的演替可能受温度、盐度变化及优势种的洄游习性影响,群落处于严重扰动状态。

Hangzhou Bay,which is located in northeastern Zhejiang Province,is a typical subtropical estuary.Because of the bay’s rich food resources,many fish,shrimp,and crab species migrate from deep sea waters to Hangzhou Bay for spawning and feeding.However,recent coastal pollution and overfishing have seriously damaged the bay’s marine environment and fishery resources.Some commercial species,such as Exopalaemon carinicauda and Portunus trituberculatus,have declined or disappeared,which may contribute to the collapse of the marine ecosystem.Macroinvertebrates are one of the most important groups of marine organisms in estuaries and play an important role in estuary food chains.Therefore,the current macroinvertebrate community structure and condition of the marine environment in Hangzhou Bay must be studied in order to provide scientific information for the ecological remediation efforts in Hangzhou Bay.The macroinvertebrate community structure of northern Hangzhou Bay was characterized,based on a field investigation of fishery resources in February,May,August,and November of 2016.The investigation focused on species composition,seasonal variation in macroinvertebrate community structure,and the relationship between the community and environmental factors.Macroinvertebrates were captured at 12 sampling stations using a beam trawl of 20 m in length and 4 m in width.The beam length was 6 m,and the opening height of the net was 2 m,with the smallest net mesh of 25 mm.Trawling was performed at 1.5-4.4 knots for 15-63 min at each station,and water temperature,salinity,and depth were recorded at the same time.Index of relative importance,cluster analysis,and multivariate statistics were used to analyze species composition,dominant species,and community structure characteristics.A total of 22 species（18genera,15 families,5 orders,and 4 classes）were captured during the study.Decapoda dominated,accounting for77.3%of the total species number,followed by Stenoglossa,which only accounted for 9.1%.Five dominant species were identified（Palaemon gravieri,Palaemon pacificus,E.annandalei,Potamocorbula amurensis,and Portunus trituberculatus）,and E.annandalei was a dominant species during all seasons,whereas P.gravieri was a dominant species during winter,spring,and autumn.CLUSTER analysis and non-metric multidimensional scaling（NMDS）indicated that the macroinvertebrate community of northern Hangzhou Bay could be clustered into two groups at 44%Bray-Curtis similarity level.Group I was classified as the winter/spring assemblage,whereas group II was classified as the summer/autumn assemblage.Group I consisted of 19 stations in February and May,and Group II consisted of 21 stations in August and November.The dissimilarity between Group I and II was as high as 57.76%,and analysis of similarity（ANOSIM）indicated that community structure of the two groups was significantly different（R=0.4,P0.01）.BIOENV indicated that the macroinvertebrate community structure of northern Hangzhou Bay was closely related to water temperature and salinity（correlation coefficient：0.39）.The present research indicated that the macroinvertebrate community structure of northern Hangzhou Bay is simple and that the main dominant species were small shrimps.There was a significant difference in the seasonal variation of the macroinvertebrate community structure of northern Hangzhou Bay,and the dominant species varied each season.Water temperature,salinity,and the ecological migration of dominant species probably impact the replacement of macroinvertebrate community structure in northern Hangzhou Bay,and the macroinvertebrate community structure of northern Hangzhou Bay is seriously disturbed.