三门湾网采浮游植物季节变化及影响因素

摘要

Sanmen Bay (28.96-29.18°E,121.58-121.85°N),located off Zhejiang,East China,is a semi-enclosed bay in a relatively still water environment.To understand the main influential factors on the bay environment,we conducted seasonal marine surveys from May 2015 to January 2016 and the follow-up analyses on community structure,temporal-spatial variation,composition and variation of dominant phytoplankton species,and compared them against available historical data.Among all the samples collected,we identified 8 phyla,87 genera,and 199 species,including 149 diatom species,27 dinoflagellate species,and few other 6 species (chlorophyta,euglenophyta,cryptomonad,haptophyte,chrysophyta and cyanophyta).Among the total,13 species of 8 genera were dominant in different seasons,of which Coscinodiscus jonesianus was an annual dominant species.The net-phytoplankton abundance showed a typical seasonal pattern;the highest average value appeared in summer (5548.91× 104cell/m3) and the lowest in spring (53.06× 104cell/m3),in annual average of 1632.04×104cell/m3.Both phytoplankton community parameters and the physico-chemical factors varied significantly (P＜0.05) in season.Clusters and similarity analysis revealed significant variations in phytoplankton community in temporal and special realm,especially at bottom section and at the bay mouth.Canonical correspondence analysis (CCA) presented that temperature,nutrients,and salinity were the main factors on the phytoplankton community.In particular,the phytoplankton abundance has been increasing in the past 30 years,during which phytoplankton community succeeded from large diatom genus to chain-forming diatoms.We believe that the in-bay eutrophication and temperature increase were the main factors responsible for the succession.%于2015-2016年春(5月)、夏(8月)、秋(11月)和冬(1月)四个航次对三门湾18个站位进行拖网采集和理化因子测定,分析了三门湾浮游植物群落结构、优势种组成、时空分布和主要影响因素,并结合历史数据,分析了浮游植物群落结构的变化规律,探讨了其主要驱动因子.调查共检出浮游植物8门87属199种(含变种、变型和未定名种),其中硅藻51属149种,甲藻18属27种,绿藻、裸藻、隐藻、定鞭藻、金藻和蓝藻偶有检出.四季共检出优势种8属13种,其中琼氏圆筛藻(Coscinodiscus jonesianus)为全年优势种.浮游植物年均丰度为1632.04× 104cell/m3,其中春季最低(53.06×104cell/m3),夏季最高(5548.91×104cell/m3).聚类和相似性分析结果表明,浮游植物群落季节变化和区域差异明显.典范对应分析表明,影响三门湾海域浮游植物群落的主要因子依次为温度、盐度、DIN和DSi.结合历史资料发现,三门湾浮游植物群落丰度总体呈增加趋势(排除20世纪80年代冬季赤潮影响),主要种类组成仍以硅、甲藻为主,赤潮藻及嗜氮性硅藻种类数及优势度均上升.此外,三门湾浮游植物由大型硅藻向链状硅藻演替.海域富营养化和水温上升可能是主要驱动因子.