湖北金沙河水库浮游植物群落结构及其与水环境因子的关系

为探明长江中游大型水库水质状况,并为饮用水源安全保障提供科学依据,于2013 2014年按季节对湖北红安金沙河水库浮游植物群落结构及其多样性进行调查,并运用多元统计定量分析浮游植物群落结构与环境因子之间的关系.共鉴定出浮游植物8门94属216种,其中绿藻门为优势种群,其种类数占总物种数的51.39%,其次是硅藻门和蓝藻门.金沙河水库优势种随季节变化而变化,夏季以尖针杆藻(Synedra acus)的优势度最大(0.195),秋季以小胶鞘藻(Phormidium tenus)(0.180)和中华尖头藻(Raphidiopsis sinensia)(0.171)的优势度最大,冬季以具星小环藻(Cyclotella stelligera)(0.220)和圆筒锥囊藻(Dinobryon cylindricum)(0.234)的优势度最大,春季则是链状曲壳藻(Achanthidum catenatum)成为绝对优势种(0.910);金沙河水库浮游植物群落总的变化规律为夏季的硅藻门、蓝藻门和绿藻门,秋季的蓝藻门、绿藻门、硅藻门和隐藻门,向冬季的硅藻门和金藻门转变,春季则是硅藻门为绝对优势类群.Shannon-Wiener多样性指数和Pielou均匀度指数显示,浮游植物在秋季的多样性和均匀度较高,春季的多样性指数和均匀度指数显著低于其它季节,这是因为春季有绝对单一的优势物种,而秋季没有,且秋季的物种数最多,因此其Margalef丰富度指数也最高.将各季节优势种和经Pearson相关性分析筛选出的环境因子进行冗余分析,结果表明筛选的环境因子中磷酸盐、总磷和溶解氧浓度是影响金沙河水库浮游植物群落结构的主要环境因子.从藻类季节变化规律来看,金沙河水库夏、秋季水质污染程度较春、冬季严重;但从藻类丰度和多样性指数来看,春、夏季水质较秋、冬季污染严重.     

钱塘江干流夏季浮游植物群落结构特征及其对水文气象的响应

河流中浮游植物的动态变化能够较好的指示河流水质状况.为探索水文气象过程对筑坝河流浮游植物群落结构的影响,2020年夏季,以钱塘江干流为例,对包括富春江水库在内的11个河段开展了浮游植物群落结构及相关环境因子的调查分析.结果 表明:夏季在钱塘江干流共鉴定出浮游植物6门59属95种,优势属为沟链藻(Aulacoseir、菱...     

Lake Kinneret phytoplankton: Stability and variability during twenty years (1970–1989)

The general features of phytoplankton seasonal succession, abundance and distribution in Lake Kinneret, as based on observations from 1970 through 1989, are summarised. Throughout this period of observation, the large, thecate dinoflagellatePeridinium gatunense formed an annual, late winter to early spring bloom resulting in very high standing stock levels. The dominance of these dinoflagellates has a profound impact upon the lake ecosystem. In the summer and fall the phytoplankton assemblage consisted mainly of nanoplanktonic green and blue-green algae and diatoms. Picophytoplankton, mainly picocyanobacteria, were present in low numbers during the dinoflagellate bloom but reached maximum abundance (10⁵ cells · ml^–1) in the epilimnion during the summer and fall. Within a given year, chlorophyll concentrations correlated well with estimates of wet weight biomass, derived from microscope counts. However, interannual averages of chlorophyll did not correlate closely with those for wet weight biomass. Both wet weight biomass and chlorophyll standing stocks fluctuated more than 2 fold from 1970 through 1989 but no extreme, long-term, continuous trend of increase or decrease was observed. Thus, phytoplankton has remained relatively stable although there has been a significant rise in the levels of summer-fall biomass since 1981. The main factor responsible for this may have been increased available phosphorus; the abundance of phytoplankton did not show any clear, long-term relation to that of herbivorous zooplankton.     

-座富营养化水库—福建山仔水库夏季热分层期间浮游植物垂向分布

对福建省水温分层型富营养化山仔水库夏季大坝断面垂向水体的物理化学参数进行了监测分析,并应用荧光分析法结合显微镜细胞计数法,对垂向分层水体和沉积物中的浮游植物生物量、群落组成及丰度进行了分析.结果表明,水库的水温分层能够引起水化学指标的分层.夏季大坝断面水体中的浮游植物以蓝藻门微囊藻属占绝对优势,垂向分布表现为表层的浮游植物细胞数量高于底层,温跃层以下细胞数急剧减少,水温分层可能决定着浮游植物的垂向分布,底泥中的浮游植物将为水体的水华提供"种源".     

广东省镇海水库拟柱孢藻(Cylindrospermopsis raciborskii)的季节动态及驱动因子分析

拟柱孢藻(Cylindrospermopsis raciborskii)是热带地区普遍存在的蓝藻种类,已在广东省很多水库成为优势种类甚至形成水华,作为一种新的有害水华类型,目前对其成因研究甚少.以广东省江门市镇海水库为研究对象,于2014年11月—2015年10月期间对其进行逐月采样,观测理化因子和浮游植物组成,测定拟柱孢藻的丝体长度,初步探讨该水库拟柱孢藻优势形成的原因.数据表明,拟柱孢藻是镇海水库的绝对优势种,常年生物量较高,介于5.9~15.5 mg/L之间,平均生物量为11.3 mg/L,占浮游植物总生物量的93.5%.从季节上看,拟柱孢藻生物量在2—6月相对较高,最高生物量出现在6月,10月和11月生物量最低.拟柱孢藻的丝体长度具有显著的季节变化,与水温呈极显著负相关.相关性分析表明拟柱孢藻生物量与总氮、总磷浓度呈显著正相关,与氮磷比呈显著负相关,而逐步回归分析表明拟柱孢藻生物量的变化主要由总磷浓度决定,推测该藻对磷的超强吸收和储存能力在其生物量季节变动中起重要作用.     

Monsoon driven changes in phytoplankton populations in the eastern Arabian Sea as revealed by microscopy and HPLC pigment analysis

Like the rest of the Arabian Sea, the west coast of India is subject to semi-annual wind reversals associated with the monsoon cycle that result in two periods of elevated phytoplankton productivity, one during the northeast (NE) monsoon (November–February) and the other during the southwest (SW) monsoon (June–September). Although the seasonality of phytoplankton biomass in these coastal waters is well known, the abundance and composition of phytoplankton populations associated with this distinct and predictable seasonal cycle is poorly known. Here we present for the first time, the results of a study on the community structure of phytoplankton for this region, derived from HPLC pigment analysis and microscopic cell counts. Our sampling strategy allowed for large spatial and temporal coverage over regions representative of the coastal and offshore waters, and over seasons that included the NE and the SW monsoon. Monthly observations at a fixed coastal station in particular, allowed us to follow changes in phytoplankton community structure associated with the development of anoxia. Together these measurements helped establish a pattern of seasonal change of three major groups of phytoplankton: diatoms, dinoflagellates and cyanobacteria that appeared to be tightly coupled with hydrographic and chemical changes associated with the monsoonal cycle. During the SW monsoon when nitrate concentrations were high, diatoms were dominant but prymnesiophytes were present as well. By October, as nitrate fell to below detection levels and anoxic conditions began to develop on the shelf below the shallow pycnocline, both diatom and prymensiophytes declined sharply giving way to dinoflagellates. In the well oxygenated surface waters, where both nitrate and ammonium were below detection limits, pico-cyanobacterial populations became dominant.During the NE monsoon, a mixed diatom-dinoflagellate population was quickly replaced by blooms of Trichodesmium erythraeum and Noctiluca miliaris with higher amounts of zeaxanthin, β-carotene, Chl b and prasinoxanthin. Trichodesmium trichomes were noticed in the water column as early as December when nitrate concentrations became limiting. The low phytoplankton biomass and high ammonium concentrations argue that active grazing populations may be responsible for preventing diatom-dinoflagellate populations from establishing themselves to bloom proportions in the eastern Arabian Sea during the early NE monsoon. Trichodesmium continued its dominance well into May, when nutrient enrichment associated with its death and decay helped simulate the growth of both diatoms and dinoflagellates. Given that anoxic conditions are becoming more pervasive in the eastern Arabian Sea, our observations in particular, those of a shift towards dinoflagellate dominance during the development of anoxia assume particular importance.     

Seasonal and spatial dynamics of nutrients and phytoplankton biomass in Victoria Harbour and its vicinity before and after sewage abatement

This study investigated the seasonal and spatial dynamics of nutrients and phytoplankton biomass at 12 stations in Hong Kong (HK) waters during a three year period from 2004 to 2006 after upgraded sewage treatment and compared these results to observations before sewage treatment. Pearl River estuary (PRE) discharge significantly increased NO(3) and SiO(4) concentrations, particularly in western and southern waters when rainfall and river discharge was maximal in summer. Continuous year round discharge of sewage effluent resulted in high NH(4) and PO(4) in Victoria Harbour (VH) and its vicinity. In winter, spring and fall, the water column at all stations was moderately mixed by winds and tidal currents, and phytoplankton biomass was relatively low compared to summer. In summer, the mean surface phytoplankton chl biomass was generally > 9 microL(-1) in most areas as a result of thermohaline stratification, and high nutrients, light, and water temperature. In summer, the potential limiting nutrient is PO(4) in the most productive southern waters and it seldom decreased to limiting levels ( approximately 0.1 microM), suggesting that phytoplankton growth may be only episodically limiting. The mean bottom dissolved oxygen (DO) remained > 3.5 mg L(-1) at most stations, indicating that the eutrophication impact in HK waters was not as severe as expected for such a eutrophic area. After the implementation of chemically enhanced primary sewage treatment in 2001, water quality in VH improved as indicated by a significant decrease in NH(4) and PO(4) and an increase in bottom DO. In contrast, there were an increase in chl a and NO(3), and a significant decrease in bottom DO in southern waters in summer, suggesting that hypoxic events are most likely to occur in this region if phytoplankton biomass and oxygen consumption keep increasing and exceed the buffering capacity of HK waters maintained by monsoon winds, tidal mixing and zooplankton grazing. Therefore, future studies on the long-term changes in nutrient loading from PRE and HK sewage discharge will be crucial for developing future strategies of sewage management in HK waters.     

Seasonal and spatial dynamics of nutrients and phytoplankton biomass in Victoria Harbour and its vicinity before and after sewage abatement

This study investigated the seasonal and spatial dynamics of nutrients and phytoplankton biomass at 12 stations in Hong Kong (HK) waters during a three year period from 2004 to 2006 after upgraded sewage treatment and compared these results to observations before sewage treatment. Pearl River estuary (PRE) discharge significantly increased NO₃ and SiO₄ concentrations, particularly in western and southern waters when rainfall and river discharge was maximal in summer. Continuous year round discharge of sewage effluent resulted in high NH₄ and PO₄ in Victoria Harbour (VH) and its vicinity. In winter, spring and fall, the water column at all stations was moderately mixed by winds and tidal currents, and phytoplankton biomass was relatively low compared to summer. In summer, the mean surface phytoplankton chl biomass was generally >9 μg L⁻¹ in most areas as a result of thermohaline stratification, and high nutrients, light, and water temperature. In summer, the potential limiting nutrient is PO₄ in the most productive southern waters and it seldom decreased to limiting levels (∼0.1 μM), suggesting that phytoplankton growth may be only episodically limiting. The mean bottom dissolved oxygen (DO) remained >3.5 mg L⁻¹ at most stations, indicating that the eutrophication impact in HK waters was not as severe as expected for such a eutrophic area. After the implementation of chemically enhanced primary sewage treatment in 2001, water quality in VH improved as indicated by a significant decrease in NH₄ and PO₄ and an increase in bottom DO. In contrast, there were an increase in chl a and NO₃, and a significant decrease in bottom DO in southern waters in summer, suggesting that hypoxic events are most likely to occur in this region if phytoplankton biomass and oxygen consumption keep increasing and exceed the buffering capacity of HK waters maintained by monsoon winds, tidal mixing and zooplankton grazing. Therefore, future studies on the long-term changes in nutrient loading from PRE and HK sewage discharge will be crucial for developing future strategies of sewage management in HK waters.     

Phytoplankton biomass size structure and its regulation in the Southern Yellow Sea (China): Seasonal variability

Phytoplankton size structure plays a significant role in controlling the carbon flux of marine pelagic ecosystems. The mesoscale distribution and seasonal variation of total and size-fractionated phytoplankton biomass in surface waters, as measured by chlorophyll a (Chl a), was studied in the Southern Yellow Sea using data from four cruises during 2006–2007. The distribution of Chl a showed a high degree of spatial and temporal variation in the study area. Chl a concentrations were relatively high in the summer and autumn, with a mean of 1.42 and 1.27 mg m⁻³, respectively. Conversely, in the winter and spring, the average Chl a levels were only 0.98 and 0.99 mg m⁻³. Total Chl a showed a clear decreasing gradient from coastal areas to the open sea in the summer, autumn and winter cruises. Patches of high Chl a were observed in the central part of the Southern Yellow Sea in the spring due to the onset of the phytoplankton bloom. The eutrophic coastal waters contributed at least 68% of the total phytoplankton biomass in the surface layer. Picophytoplankton showed a consistent and absolute dominance in the central region of the Southern Yellow Sea (>40%) in all of the cruises, while the proportion of microphytoplankton was the highest in coastal waters. The relative proportions of pico- and nanophytoplankton decreased with total biomass, whereas the proportion of the micro-fraction increased with total biomass. Relationships between phytoplankton biomass and environmental factors were also analysed. The results showed that the onset of the spring bloom was highly dependent on water column stability. Phytoplankton growth was limited by nutrient availability in the summer due to the strong thermocline. The combined effects of P-limitation and vertical mixing in the autumn restrained the further increase of phytoplankton biomass in the surface layer. The low phytoplankton biomass in winter was caused by vertical dispersion due to intense mixing. Compared with the availability of nutrients, temperature did not seem to cause direct effects on phytoplankton biomass and its size structure. Although interactions of many different environmental factors affected phytoplankton distributions, hydrodynamic conditions seemed to be the dominant factor. Phytoplankton size structure was determined mainly by the size-differential capacity in acquiring resource. Short time scale events, such as the spring bloom and the extension of Yangtze River plume, can have substantial influences, both on the total Chl a concentration and on the size structure of the phytoplankton.     

Phytoplankton community in the tropical lake of Lagoa Santa (Brazil): Conditions favoring a persistent bloom of Cylindrospermopsis raciborskii

This study presents data on seasonal changes of the phytoplanktonic community of a small tropical lake, Lagoa Santa, in the Brazilian cerrado. Temporal variation in the community structure was small and we observed a permanent dominance of the cyanobacteria Cylindrospermopsis raciborskii. This dominance could be associated to the stability of several environmental conditions. Especially water temperature, always within the optimal growth range for C. raciborskii, and the constant mixed water column may have been important factors driving to the long term dominance of this species in the lake. Remarkable seasonal variation in rainfall, as well as the occasional and non-seasonal variation in nutrient concentrations, were important to explain changes in environmental and biological variables, but were not related to the dominance of C. raciborskii. Pearson's correlation and PCA could just in part explain the stable dominance of this cyanobacterium. Meteorological and chemical factors seem to have no clear control on the variability of the phytoplankton dynamics in Lagoa Santa. The weak relationship between C. raciborskii abundance and environmental variables points to additional intrinsic factors associated to this species that may be important in structuring the phytoplankton assemblage.     

Effects of nitrogen and phosphorus on phytoplankton composition and biomass in 15 subtropical, urban shallow lakes in Wuhan, China

This study aims at investigating the composition and biomass of the phytoplankton community in 15 urban shallow eutrophic lakes as well as the effects of main environmental factors, including nutrient concentrations and the ratio of nitrogen to phosphorus, temperature, COD, BOD, water depth, etc. on the phytoplankton community structure. Lake water samples were taken and analyzed on a bimonthly basis during the period from March 2004 to March 2006. The redundancy analysis (RDA) and regression analysis (RA) were performed to identify the effects of nutrients on the phytoplankton community and biomass in these typical urban lakes. The results indicate that most of these urban lakes were hypertrophic due to high concentrations of total phosphorus (TP) and total nitrogen (TN), with mean levels of 490 and 5380 mg m⁻³, respectively. The phytoplankton community was dominated by Microcystis aeruginosa and Euglena caudate in summer and Cryptomonas ovata and Cyclotella meneghiniana in winter. The mean biomass of the phytoplankton reached 456.87 mg L⁻¹ in summer months and the annual level was 189.24 mg L⁻¹. Temperature and TP content were found to be the principal limiting factors for phytoplankton growth on an annual basis. On the other hand, the results of RDA and RA demonstrate that the dominant phytoplankton species were not nutrient-limited during summer months. Low TN:TP ratios (<10) were detected accompanied with fewer occurrences of N-fixing cyanobacteria and other filamentous algae in most lakes in summer, which implies that low N:P ratio does not always shifts the dominance of phytoplankton community to the N-fixing cyanobacteria. Moreover, TP always had higher correlation with chlorophyll a (Chl-a) than TN, even when the TN:TP ratios of most samples were lower than 10. Therefore, it is concluded that the TN:TP ratio is not always a suitable index to determine whether nitrogen or phosphorus limits the phytoplankton biomass in urban shallow eutrophic lakes.     

西藏麦地卡湿地的浮游植物——1.优势种的时空生态位

为了解青藏高原湿地浮游植物在时空不同维度上的分布特征,本文选取西藏四大国际湿地之一的麦地卡湿地作为研究地点,于2019年7月和10月在麦地卡湿地主要水系——麦地藏布及其支流和湖泊,设置了14个样点,采集了2个水情期（丰水期和枯水期）浮游植物的水样共252个.通过活体观察和固定染色方法鉴定浮游藻类物种,使用直接计数法统计浮游藻类的数量.计算麦地卡湿地浮游植物优势种的优势度指数（Y）、更替率（r）、生态位宽度（B_i）、生态位重叠值（O_ik）和生态响应速率（R）,运用生态位分化的方法,对麦地卡湿地浮游植物优势种的生态位进行了不同时空维度的研究.结果表明：本研究中鉴定出浮游植物优势种（Y>0.02）共8种,其中克洛脆杆藻（Fragilaria crotomensis）和窗格平板藻（Tabellaria fenestrata）是2个水情期的共有优势种.生态位宽度值差异较大,可分为三大生态位类群,且优势度指数与生态位宽度值呈极显著正相关.总体上浮游植物优势物种的生态位重叠值高,在时间、空间和时空三个维度上O_ik>0.6的分别占89.29%、60.71%和28.57%.生态响应速率之和在时间维度上为负数,在空间和时空维度上为正数,说明该湿地浮游植物群落处于发展阶段.冗余分析表明,酸碱度、溶解氧、总氮和浊度是影响麦地卡湿地浮游植物优势种分布的重要因素,浮游植物优势种在这些环境因子上存在明显的生态分化现象.     

The role of phosphorus in growth of phytoplankton in Lake Vesijärvi,southern Finland – a multitechnique approach

The role of phosphorus in phytoplankton growth was studied in Lake Vesijärvi, a large previously eutrophic body of water with a history of flourishing fishery. The study combined different approaches: long-term algal enrichment experiments with natural phytoplankton assemblages were carried out together with observations on nutrient and chlorophyll a concentrations, elemental ratios (N:P, C:P, C:N) of particulate matter, and analysis of P uptake using [³³P]. None of the approaches revealed periods of P limitation, but some growth experiments as well as elemental ratios indicated slight deficiency in early summer. Concentrations of total dissolved phosphorus (TDP), which were usually 20–30 g l^–1, also indicated luxurious P resources. Thermal stratification was weak and the lake mixed twice during the study period; this was reflected in the phytoplankton biomass that increased up to 4-fold. Results of elemental ratios usually suggested the occurrence of nitrogen limitation, and in general these ratios were low for a lake. All size fractions >0.22 m in the experiments with [³³P] showed P uptake. In August most of the P was taken up by picoplankton, but when the lake turned over in September, the uptake of P by this fraction was absent. Thus, there was always a plentiful supply of P for phytoplankton, but the shortage of inorganic N may have affected those algae not capable of fixing N₂. These conditions should have favoured the growth of heterocystous cyanobacteria, but these prokaryotes never attained high abundances. This may have been due to the weak stability of the water column, or the growth of cyanobacteria may have been limited by trace elements such as molybdenum or iron.     

西藏拉鲁湿地浮游植物群落时空分布特征及其驱动因子

为了解西藏拉鲁湿地浮游植物群落时空分布特征及其驱动因子,于2021年7月、10月和2022年5月在拉鲁湿地主要水系进行定性和定量样品采集,共采集浮游植物水样126个,从不同季节和不同生境浮游植物种类组成、多样性等方面入手,探讨拉鲁湿地浮游植物群落时空分布特征及其驱动因子,为研究拉鲁湿地生态系统和稳定发展提供基础资料。结果表明:1)拉鲁湿地共鉴定出浮游植物532种(含变种和变型),隶属于8门13纲36目74科130属,物种组成表现为硅藻-绿藻-蓝藻型。2)拉鲁湿地浮游植物群落特征参数在不同季节和不同生境之间存在差异。夏季浮游植物群落的Shannon-Wiener多样性指数显著高于秋季和春季,Simpson优势度指数显著高于秋季。秋季浮游植物群落的Pielou均匀度指数显著低于夏季和春季。春季浮游植物群落的Margalef丰富度指数显著低于夏季和秋季。沼泽生境的浮游植物群落的Margalef丰富度指数显著高于湿草甸生境。3)季节是浮游植物群落组成差异的关键因素,生境对浮游植物群落组成的影响较弱,夏季的距离衰减模式比秋季和春季更强。4)拉鲁湿地不同的浮游植物群落参数与不同环境因子之间存在显著的关联。5)空间因素在解释浮游植物群落变异方面具有显著贡献,而快速变化的水质变量在决定浮游植物的季节变化中起着重要作用。季节和缓慢变化水质因子的解释能力相对较弱,但仍对浮游植物群落的变异有一定影响。     

Basic limnological characteristics of the shallow eutrophic lake Grimnitzsee (Brandenburg, Germany)

The medium shallow lake Grimnitzsee (maximum depth: 9.9 m; mean depth: 4.6 m; area: 7.7 · 10⁶ m²) which is situated in the biosphere reserve “Schorfheide-Chorin” in northern Brandenburg (Germany) was studied in 1994 and 1995. A bathymetric map of Grimnitzsee is given for the first time. The lake is usually polymictic although in 1994 and 1995 relatively long summer stratification was observed due to very high global radiation input. Nutrient concentration, light climate, oxygen status, phytoplankton biomass and the species composition of littoral diatoms characterize the lake as eutrophic. Special features deducible from the lake's polymictic character were the multiple development of aerobic or anaerobic strata above the sediment, the fast recovery of silicon concentration in the water column after diatom sedimentation, the importance of resuspension for the success of planktonic diatom populations, and an only moderate correlation between chlorophyll a concentration and light attenuation as well as seston dry weight probably due to the influence of suspended particles.     

鄱阳湖河湖转换期间鱼腥藻(Anabaena)的变化

鄱阳湖作为我国长江目前仅存的两个通江湖泊之一,年内水位变幅巨大.通过在鄱阳湖2013年河湖转换期间(5—11月)对鄱阳湖主航道都昌段进行每月3~4次的高频监测,以考察鄱阳湖水体中鱼腥藻(Anabaena)的动态变化,分析鄱阳湖中鱼腥藻生长并占优势的影响因素.结果表明,蓝藻为鄱阳湖浮游植物的次级优势种,8月蓝藻生物量平均占浮游植物生物量的57%,蓝藻取代硅藻成为暂时的优势种.夏、秋季水华蓝藻以固氮鱼腥藻为主,主要与夏、秋季水温较高以及适宜的营养盐条件等有关.研究期间鄱阳湖水体氮磷比平均在15左右,鱼腥藻能够产生有固氮能力的异形胞,并在水华蓝藻中成为优势种,也反映了鄱阳湖某些湖区存在氮相对缺乏的阶段.     

纳木错水温变化及热力学分层特征初步研究

水温变化是湖泊的重要物理特性,对湖泊的水质特征、湖水能量循环、水生生态系统研究具有重要意义.基于不同季节的实地观测资料,分析青藏高原高海拔、深水大湖纳木错的水温变化特征及季节差异,并着重分析湖水热力学分层的季节变化.结果显示纳木错中部、东部两个湖盆冬季封冻,夏季存在稳定分层,春、秋季混合,是一个典型双季对流、完全混合型湖泊.但两个湖盆水温变化与热力学分层又有各自的特征,东部浅湖盆湖水在春季升温快,夏季分层与秋季翻转均比中部湖盆早,且秋季翻转时水温也比中部湖盆高.初步分析认为两个湖盆不同的湖盆形状及水深分布可能是造成其热力学特征差异的主要原因.     

基于15N稳定同位素示踪技术的太湖梅梁湾浮游植物群落氮吸收动力学研究

浮游植物对氮的吸收与其生长繁殖密切相关,太湖梅梁湾湖区蓝藻水华频频暴发,对该水域浮游植物氮吸收进行研究具有重要意义.本文分别在冬、春、夏、秋4个季节于梅梁湾采样,对水体常规理化指标和浮游植物群落结构进行分析,并利用¹⁵N稳定同位素示踪技术研究了浮游植物对铵态氮（NH₄⁺-N）、硝态氮（NO₃^--N）和尿素态氮（Urea-N）吸收的动力学特征.结果表明,太湖梅梁湾浮游植物群落除了秋季对NH₄⁺-N的吸收不符合米氏方程外,其余均符合.冬季和春季3种形态氮最大吸收速率（V_max）的大小依次为：NH₄⁺-N > NO₃^--N > Urea-N,而夏季为：NH₄⁺-N > Urea-N > NO₃^--N.3种形态氮V_max的季节变化规律为夏季 > 秋季 > 春季 > 冬季.V_max在不同季节以及不同形态氮之间的差异性可能与浮游植物群落组成以及水体中NH₄⁺-N浓度不同有关.浮游植物对NH₄⁺-N吸收的K_S值在冬、春季高于夏季,对Urea-N吸收的K_s值则在夏、秋季高于冬、春季,而对NO₃^--N吸收的K_s值则在夏季显著高于其他3个季节.冬季和春季梅梁湾浮游植物群落最容易受到NO₃^--N限制,而最不容易受到Urea-N的限制;而夏季,则最容易受到NO₃^--N限制,而最不容易受到NH₄⁺-N的限制,且浮游植物群落对NH₄⁺-N的亲和力最高.与NO₃^--N相比,秋季浮游植物更容易受到Urea-N的限制.不同季节,容易对浮游植物产生限制作用的氮的形态不同.     

黑河流域浮游植物群落特征与环境因子的关系

分别于2009年夏季和2010年夏、秋季对黑河流域进行了2次全面调查,共选取76个采样断面进行水样采集,鉴定出浮游植物242种,隶属于8门11纲25目45科94属.其中硅藻门为优势类群,占物种总数的38.43%,绿藻门和蓝藻门次之;黑河流域优势种为尺骨针杆藻(Synedra ulna)、无常蓝纤维藻(Dactylococcopsis irregularis)和尖针杆藻(S.acus),优势度分别为0.060、0.031和0.021,出现频度分别为43.42%、43.42%和46.05%.生物多样性指数及相关指数分析表明,黑河流域中、下游浮游植物群落结构的复杂程度和稳定性均高于上游;同时,综合生物多样性指数及相关指数以及水质理化指标表明,黑河上游水质为无污染或轻度污染,中、下游水质为轻中度污染.浮游植物丰度与环境因子的相关性分析表明,上游浮游植物丰度与水体硬度呈显著正相关;中游浮游植物丰度则与各环境因子无显著相关性;下游浮游植物丰度与水体硬度呈显著负相关,而与总氮×总磷呈显著正相关;总溶解性固体、pH值和水体硬度与全流域浮游植物丰度呈显著正相关.黑河流域浮游植物的空间分布具有与河水水文分带相对应的垂直地带性和水平地带性分异特征.