珠三角河网浮游植物物种丰富度时空特征

对2012年珠三角河网浮游植物物种丰富度的时空特征进行了系统阐析。季节上,枯水期的物种丰度差异大,丰水期差异小;空间上,广州周边及河网中部个别站位的总种数高于其他站位。不同季节的空间特征显示,枯水期的物种丰度自西江沿线、河网中部、广州周边呈递增趋势;而丰水期呈现三角洲两侧的物种丰富度高于河网中部。各类群相对组成结果显示,硅藻在枯水季节占绝对优势,丰水期优势下降;空间上广州周边站位硅藻百分比明显低于其他站位。分析原因,径流相关的补充和稀释作用和水体搅动引起的底层藻类的悬浮补充不仅影响物种丰富度的季节变动,也影响不同类群的相对组成;水体交换能力和营养盐分别是决定丰水期和枯水期物种丰富度空间分布的关键因素。     

珠三角河网裸藻的多样性特征

珠三角河网是珠江汇入南海的必经之地,2012年对该水域裸藻门及各属的多样性特征及影响因子进行系统阐析。调查期间共发现裸藻12属84种,其中裸藻属是最主要类群,其次为扁裸藻属和囊裸藻属。珠三角河网独特的地理位置和人类活动造成的水体富营养化是该水域裸藻物种多样性丰富的主要原因。季节特征显示,丰水期裸藻的种类丰富度和生物量均明显高于枯水期。除了洪水引发的裸藻物种的外源供给增大外,泄洪所带来的有机质的增加也是有利因素。此外,丰水期对应的高温也是有益条件。空间特征存在明显的季节差异,丰水期河网外侧站位的生物量和种类丰富度高于中部站位,主要原因是受径流影响较大;枯水季节除广州附近站位的值明显偏高外,其它站位间差异不大,营养盐的空间格局是主要决定因素。尽管裸藻主要依赖于沿江静水水体中的外源供给,分析表明,其在随水流下行的过程中存在增长过程。不同藻属相对组成的结果显示,扁裸藻属和囊裸藻属因属于生长缓慢的K-选择策略型,富集营养物质的能力不及裸藻属,仅在枯水期与裸藻属形成互补优势。裸藻门及主要属的生物量与种类丰富度呈线性正相关关系,偏重于多样性单峰模式的上升区。     

珠三角河网浮游植物生物量的时空特征

珠三角河网水域是珠江之水流入南海的必经之地,对2012年该水域浮游植物生物量的时空特征及其影响因素进行系统阐析。调查期间共发现浮游植物7门,383种(包括变种、变型),其中硅藻和绿藻是最主要类群,其次是裸藻和蓝藻。颗粒直链藻原变种是调查水域的本底物种,也是最优势种;而变异直链藻和网球藻分别是枯水季节和丰水季节的指示物种。从季节变动看,浮游植物总生物量呈现枯水季节高、丰水季节低的特征,主要与径流导致的稀释作用和透明度升高引发的沉降损失有关。从空间分布看,总生物量呈现自西南向东北升高的趋势,主要与营养盐的空间分布格局有关,而且空间分布格局无季节差异。从不同类群的相对组成上看,硅藻占据绝对优势地位,绿藻和裸藻次之,这与20世纪80年度初的调查结果基本一致。硅藻在枯水季节占据绝对优势地位,而在丰水季节由于绿藻和裸藻优势的明显增大,导致硅藻的优势下降,这与流域中一些死水区域如水库、浅滩中的蓝绿藻和裸藻在丰水期涌入干流有关,PCA分析结果也证明了这一点。此外,不同站位在相对组成上的季节变动还受盐度的影响。综上,物理因子包括与径流相关的稀释作用和与透明度相关的沉降损失不仅影响总生物量的季节变动,也影响不同类群的相对组成;而化学因素如营养盐含量是决定总生物量空间分布的关键因素,与河口潮汐作用相关的盐度变化对类群相对组成的空间分布起到一定的影响作用。     

珠三角河网链状硅藻物种组成及生态特征

珠三角河网水域是珠江之水流入南海的必经之地,于2012年和2015年对该水域的链状硅藻的时空特征及其影响因素进行了分析。共发现链状硅藻18种(包括变种和变型),颗粒沟链藻是该水域的绝对优势种,也是该区域水体富营养化的重要指示物种。总生物量的时间变化模式呈现枯水期差异较大,丰水期差异较小的特点,主要是受到径流量、透明度和水温差异的影响;空间特征主要表现为广州市周边站位的生物量明显偏高,主要受水体富营养化的影响。不同链状硅藻的相对百分组成显示,颗粒沟链藻是绝对优势种,变异直链藻易在枯水期与其形成竞争优势。沟链藻属的链长一般大于直链藻属,这主要得益于其形态结构较稳固的优势;此外,透明度、营养盐和pH值等也是影响链长的重要因素。     

北部湾近岸海域浮游动物群落结构特征及季节变化

2017年3月(枯水期)、7月(丰水期)和10月(平水期)分别对北部湾近岸海域44个站位的浮游动物进行了调查。结果共检出浮游动物251种和浮游幼体24类,其中枯水期138种(类),丰水期134种(类),平水期191种(类),分属河口低盐、近岸暖温、近岸暖水和外海暖水4个生态类群。优势种9种,其中枯水期以原生动物占绝对优势,丰水期以枝角类、桡足类和浮游幼体类占优势,平水期以十足类和浮游幼体类占优势。浮游动物丰度年均值为789.95个/m~3,呈现出枯水期(1540.19个/m~3)明显高于平水期(457.58个/m~3)和丰水期(372.08个/m~3)的季节变化特征;浮游动物生物量年均值为252.40 mg/m~3,生物量的季节变化与丰度变化不一致,平水期生物量(385.01 mg/m~3)明显高于枯水期(221.41 mg/m~3)和丰水期(150.78 mg/m~3)。多样性指数平水期最高(3.16),丰水期(2.35)次之,枯水期(2.22)最低。枯水期和丰水期北部湾近岸海域浮游动物生物量和丰度水平分布特征基本呈现自河口近岸海域向外海递增的趋势,平水期浮游动物生物量与丰度的空间分布较为均匀。浮游动物的种类组成结构以及优势种的演替对浮游动物的生物量和丰度季节变化有着重要的决定作用。径流导致的悬浮物、营养盐等的变化可能是决定北部湾近岸海域浮游动物生物量和丰度空间分布的主要因素。研究还表明与其他海湾相比,北部湾近岸海域浮游动物群落结构趋于小型化,需加大关注。     

西江下游浮游植物群落周年变化模式

西江肇庆段是珠江干流汇入珠三角河网水域的咽喉通道,对2009年该江段的浮游植物群落组成及变化进行系统阐析.调查期间共发现浮游植物7门,245种(包括变种、变型),其中硅藻和绿藻是浮游植物群落组成的最主要类群,分别占总种数的42.44％和34.69％,其次是裸藻和蓝藻.PCA分析结果显示,浮游植物各类群的种类丰富度和生物量的周年变化趋势主要受水温和径流量的影响.浮游植物种类丰富度的周年变化呈现明显的高温季节高,低温季节低的特征,除因大多数藻类物种直接喜好高温之外,径流量的增大有助于真浮游绿藻种类的外源注入及半浮游和偶然性浮游硅藻种类的增加.浮游植物生物量的周年变化呈现明显的双峰型,峰值分别出现在8月和11月.然而8月份第1个高峰出现之前,生物量波动不大,尽管水温的升高有助于生物量的增加,但是径流量增大所带来的稀释作用掩盖了水温上升对浮游植物生长的促进作用.真浮游植物生物量的变化趋势和数值与总浮游植物极其接近,主要得益于真浮游硅藻物种颗粒直链藻在总种群中的绝对优势地位.综上,水温升高对浮游植物种类丰富度和生物量的增长均有促进,径流量的增大虽然有助于种类丰富度的增加,但不利于生物量的增加.     

珠江三角洲河网浮游轮虫的群落结构

通过2012年4次对珠江三角洲河网浮游动物的生态调查,研究该水域浮游轮虫的群落结构,包括种类组成、优势种、生物量及多样性等的时空分布,探讨了浮游轮虫群落结构与环境因子的相关关系,并阐析了浮游轮虫的聚群结构.结果表明： 共检出53种浮游轮虫.优势种类的季节演替及空间变化明显,针簇多肢轮虫占有较大优势.从季节变化来看,枯水期密度及生物量均大于丰水期,丰水期的生物多样性指数和均匀度要高于枯水期,浮游轮虫生物量和多样性的季节间差异显著;从空间分布来看,平均密度及平均生物量均呈现自西南向东北升高的趋势,最大密度及生物量均出现在市桥,而生物多样性指数和均匀度指数的空间变化趋势则相反,最高值均出现在青岐,浮游轮虫密度在各调查站位间差异显著,生物量及多样性在各调查站位间的差异不显著.浮游轮虫的密度与生物量、生物多样性指数与均匀度指数呈显著正相关,多样性与生物量呈显著负相关,生物多样性指数和均匀度指数随着生物量的增加显著降低.在不同季节,浮游轮虫密度与水温、pH、溶解氧、叶绿素a含量及总磷、总氮等环境因子密切相关.根据浮游轮虫密度对调查站位进行聚群分析得出5种聚群结构,说明相应调查站位的水质状况有显著差异.     

西江颗粒直链藻种群生态特征

西江肇庆段是珠江干流汇入珠三角河网水域的咽喉通道,结合长期定点连续采样和空间季节性调查,重点对2009年西江干流肇庆段的颗粒直链藻(Aulacoseira granulata)的种群生态学特征进行系统分析。结果显示:全年中,颗粒直链藻在总种群中所占百分比均值为25.37%,与总种群丰度存在极显著正相关关系,这表明颗粒直链藻是西江浮游植物群落的重要优势种。调查期间发现了颗粒直链藻的4种形态,包括原变种(var.granulata)、极狭变种(var.angustissima)、弯曲变种(var.curvata)和极狭变种螺旋变型(var.angustissima f.spiralis)。其中,原变种占有绝对优势地位,其相对百分组成的年均值为91.47%,推测为原变种的形态结构比其它3种形态更容易适应外界环境变化,进而形成优势群体。颗粒直链藻总密度的周年变化呈现明显的双峰型,两个峰值分别出现在8月和11月,主要得益于适宜的水温、相对稳定的水体和较高的营养盐水平,这些均有助于颗粒直链藻的生长繁殖。第一个高峰之前,颗粒直链藻总密度未出现明显的波动,这很可能是由于水体径流量增大导致的稀释作用和频繁降雨导致的水体剧烈波动对颗粒直链藻增长的负作用掩盖了水温上升所带来的益处。从空间分布来看,颗粒直链藻总丰度的最大值一般出现在S1、S5和S6站点,这与营养盐最大值的空间分布格局是一致的。     

鹤地水库浮游植物群落的结构与动态

鹤地水库位于雷州半岛北部(21°42'～22°22'N,109°54'～110°25'E),是一座中营养化的大型水库.为了研究其浮游植物群落的结构与变化特点,在水库设置5个采样点,并于2003年2、7、9、12月对其采样.鹤地水库浮游植物生物量变化为O.156～2.548 mg L~(-1),主要由蓝藻和硅藻组成.5个采样点的浮游植物生物量具有明显的季节变化,且变化趋势相同,即丰水期的生物量高于枯水期,主要是由于丰水期水温较高以及入库河水带入的营养盐.5个采样点的浮游植物生物量从主要入库河流至大坝区呈下降趋势,与磷浓度的降低直接相关.浮游植物优势种主要以热带代表性种类为主,且有明显的季节变化,枯水期主要为硅藻的根管藻(Rhizosolenia sp.)、小环藻(Cyclotella sp.)、颗粒直链藻(Melosira granulata)以及模糊直链藻(Melosira ambigua)等.丰水期为蓝藻的拟柱孢藻(Cylindrospermopsis raciborskii)、湖泊假鱼腥藻(Pseudanabaena limnetica)等,浮游植物优势种类的变化主要受磷浓度的影响.浮游植物前8个优势种的生物量占浮游植物群落生物量的850%～92%,显著低于温带地区浮游植物群落结构稳定的湖泊.     

粤东柘林湾根管藻(Rhizosolenia)群落组成的季节特征

于2004年5月至2005年2月对粤东大规模养殖区柘林湾的根管藻(Rhizosolenia)种群的时空分布进行了季节性调查.调查期间,共发现根管藻16种(含变种、变型),其中柔弱根管藻(R. delicatula),脆根管藻(R. fragilissima),刚毛根管藻(R. setigera)和笔尖根管藻粗径变种(R. styliformis var. latissima)均为全年出现种.柘林湾根管藻种类丰富度和群落密度的季节变化均呈现高温季节高低温季节低的特点,而平面分布均表现出由湾内向湾外递增的趋势.整体而言,柘林湾是一个根管藻种类数很高而群落密度处于中等水平的海湾.分析表明,水温是影响柘林湾根管藻种类丰富度和群落密度季节变化的关键因素,而光照、种间竞争和浮游动物群落结构的组成是影响其时空分布的主要因素.     

Environmental and spatial processes influencing phytoplankton biomass along a reservoirs‐river‐floodplain lakes gradient: A metacommunity approach

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Benthic infaunal community variability on the northern Svalbard shelf

Marine benthic communities are effective indicators of environmental change. Yet in the Arctic, there are few empirical tests of how sustained climatic change may influence community structure. Northern Svalbard is influenced by both warm Atlantic and cold Arctic water masses, providing an opportunity to assess potential effects of long-term environmental changes by examining spatial variation in community structure. We examined benthic macroinfaunal communities and sediment pigments under Atlantic and Arctic water masses on the northern shelf and fjords of Svalbard. We report on infaunal biomass, abundance, species composition, and diversity at 10 stations spanning 79°–81°N and ranging in depth from 200 to 500?m. Benthic biomass averaged 128?g?WW?m^?2 (48–253?g?WW?m^?2), mean density was 3,635?ind.?m^?2 (780–7,660?ind.?m^?2), and species richness varied from 45 to 136?taxa?stn.^?1. Abundance-based community structure clustered stations in groups related to water mass characteristics, with Atlantic and Arctic shelf stations being well distinguished from each other. Dominant taxa were different in Atlantic- and Arctic-influenced locations. Faunal biomass was highest in the Atlantic-influenced fjords, followed by Arctic fjords and Arctic shelf stations, with Atlantic shelf stations having the lowest biomass. Species richness and diversity were inversely related to biomass. Patterns in faunal biomass were strongly correlated with sedimentary pigments (R ²?=?0.74 for chl a and R ²?=?0.77 for phaeopigments), with large differences in sedimentary pigment concentration among stations. These relationships suggest that benthic fauna on the northern Svalbard shelf are food limited and dependent on predictable, albeit episodic, delivery of organic matter from the water column.     

Phytoplankton composition and abundance of a central Amazonian floodplain lake

The phytoplankton community of Lake Camaleão, a smallfloodplainlake influenced by a large whitewater river, the Solimões, was monthlyinvestigated for the composition and abundance of itsphytoplankton. The seasonal influence of the floodregime on biomass, species richness and diversity, andits relation with physical and chemical factors(temperature, pH, dissolved oxygen, electricalconductivity, total seston and inorganic nutrients)was analyzed and subjected to principal componentanalysis. Diversity was variable along the seasonalcycle: relatively high values were observed at the endof the dry season supported by high nutrientconcentrations. The phytoplankton was comprised of 262 taxa,with strong dominanceof euglenoids (81%). The three sample stations did not differamong each other, except in the dry season, due todata cluster in relation to theprincipal axis (1 and 2), explaining 63% of thevariation. Biomass accumulation as a function of lakearea reduction contributed to theseresults, indicating that the phytoplankton dynamicswere hydrology-driven.     

Hydrological complexity supports high phytoplankton richness in the Doñana marshland (SW Spain)

Two hundred and twenty-four phytoplanktonic taxa were recorded in a riverine floodplain on the NE side of the Doñana marshland from September 2002 to 2004. This collection of 11 samples included 80 Bacillariophyceae (Diatoms), 71 Chlorophyta, 39 Cyanophyta, 19 Euglenophyta, 6 Chrysophyceae, 5 Cryptophyta, and 4 Dinophyceae. Fifty-five percent of the total taxa had a very low frequency of appearance (<5%), while only three species appeared with a frequency >90% (Monoraphidium contortum Komárková-Legnevorá, Cyclotella atomus Hustedt, and Nitzschia palea W. Smith). According to multivariate analyses, both temporal and spatial factors produced a pattern in the phytoplankton assemblages dominated by freshwater inputs during winter flooding, tidal inputs in summer, and transitional stages during the rest of the year. Spatial segregation of phytoplankton was likely due to differences in retention time and distance to water input. The main taxa involved in this segregation were Chrysidalis sp. 1 (June 2003 and 2004), Chlamydomonas sp. 4 (September 2003), C. atomus (December 2003), and Tetradesmus aff. crocini (February 2004). The hydrologic complexity of the study area could account for this high taxa richness by promoting replacement and colonization episodes following seasonal changes in water source (freshwater versus tidal inputs).     

The hydro-morphological index of diversity: a tool for describing habitat heterogeneity in river engineering projects

Species composition and seasonal succession of phytoplankton were analyzed in a lowland river located in South Banat (Ponjavica, Serbia). As a result of human activity, a network of irrigation channels was built on the Ponjavica River’s upper and lower courses. These channels reduce the water level in the river and help to create favorable conditions for accelerated eutrophication processes. Eight phytoplankton divisions with 444 taxa were present. Physical and chemical testing of water, phytoplankton abundance and biomass, as well as chlorophyll a concentration showed a high level of eutrophication. Cyanobacterial biomass developed in 2002 with dominance of Microcystis aeruginosa and Aphanizomenon flos-aquae. Changes in phytoplankton composition were observed during 2008, characterized by the appearance and dominance of Cylindrospermopsis raciborskii when this species accounted for more than 85% of the total phytoplankton biovolume. The change in dominant phytoplankton functional groups was observed: codons H₁ and M characterizing summer in 2002 were replaced by codons S_N and S₁ in 2008. This study compares the presence of C. raciborskii with other phytoplankton species in relation to water quality parameters. High abundance of this species correlated positively with biochemical oxygen demand and turbidity, and negatively with NO₃-N concentrations during the study period.