黄河口邻近海域浮游植物群落及其多样性的长期变化(1960-2010)

研究了1960―2010年黄河口邻近海域浮游植物群落及其多样性的长期变化,数据来源于19次调查245份样品。使用小型浮游生物网垂直采集浮游植物样品,于光学显微镜下进行分类统计。共鉴定出浮游植物108种,其中硅藻(Bacillariophyta)87种,甲藻(Pyrrophyta)17种,角毛藻(Chaetoceros spp.)和圆筛藻(Coscinodiscus spp.)分别出现了27种和10种。浮游植物总丰度年代际平均为2.74×10~6 ind/m~3,在20世纪80年代出现峰值,高达16.8×10~6 ind/m~3。硅藻在20世纪占据优势,群落以角毛藻、圆筛藻等大的中心硅藻为主,进入21世纪后出现小型化的趋势,舟形藻(Navicula spp.)、新月菱形藻(Nitzschia closterium)等羽纹硅藻以及具槽帕拉藻(Paralia sulcata)等底栖性物种开始形成优势。甲藻丰度出现了上升的趋势,角藻(Ceratium spp.)、夜光藻(Noctiluca scintillans)、原多甲藻(Protoperidiniumspp.)开始增多。50年来,星脐圆筛藻(C.asteromphalus)、辐射圆筛藻(C.radiatus)、柔弱角毛藻(C.debilis)、伏氏海线藻(Thalassionema frauenfeldii)等物种在群落中一直占据较为明显的优势,但是优势种组成演替和格局转换明显。在黄河持续断流和强厄尔诺事件的共同影响下,口区浮游植物丰度和多样性在20世纪末降至最低,平均仅为87.7×10~4 ind/m~3和1.97(Shannon-Weaver指数)。进入21世纪后,调水调沙等人类活动对口区浮游植物丰度和多样性水平的改善产生了积极影响,较20世纪末分别有了2.3倍和16.8%的增加,呈现出稳步回升的趋势。对黄河口浮游植物群落及其多样性长期变化过程的研究,为河口生态系统演变和健康保护、渔业资源的增殖养护提供了基础资料。

Long-term changes of phytoplankton community and diversity in adjoining waters of the Yellow River estuary (1960-2010)

Based on 245 samples collected in 19 cruises from 1960 to 2010 in adjoining waters of the Yellow River estuary,the long-term changes of the phytoplankton community and diversity were analyzed.These samples were towed from the seafloor to the surface at each site by using a standard phytoplankton net and subsequently checked for the species composition and cell abundance under an optical microscope in the laboratory.A total of 108 species were recorded,of which 87 were diatoms and 17 were dinoflagellates.Chaetoceros spp.and Coscinodiscus spp.were the larger groups,with 27 and 10 species documented,respectively.The average total phytoplankton abundance during the last fifty years was 2.74× 106 ind/m3,with a peak of 16.8× 106 ind/m3 in the 1980s.Diatoms dominated the community in the last century,such as the large centric diatoms Chaetoceros spp.and Coscinodiscus spp.However,the species in this century shifted to pennate diatoms like Navicula spp.and Nitzschia closterium,as well as benthic species like Paralia sulcata.There was an increasing trend in abundance of the dinoflagellates Ceratium spp.,Noctiluca scintillans,and Protoperidinium spp.During the past fifty years,Coscinodiscus asteromphalus,Coscinodiscus radiatus,Coscinodiscus debilis,and Thalassionema frauenfeldii were dominant in the community.However,the composition of dominant phytoplanktons had indeed changed and shifted.Under the co-influence of the absence of river flow and a strong E1 Nifio event,the species abundances and diversity had decreased to the lowest levels during the last century,with average values only being 87.7×104 ind/m3 (Shannon-Weaver index=1.97).During this century,however,the phytoplankton community and diversity in the Yellow River estuary have been altering under human activity,such as water-sediment regulation,with a steady recovery of 2.3 times and 16.8％ increase over the levels at the end of the last century.This study on the long-term shift in phytoplankton community and diversity will provide a basic background for future protection of the estuarine ecosystem and enhancement of fishery resources in the adjoining waters of the Yellow River estuary.