辽河水体光学吸收特性的季节变化

吸收特性是水体重要的光学特性,也是建立生物光学模型的基本参数。利用2013年5月和9月辽河流域水体实测数据对总悬浮颗粒物、浮游植物、非藻类颗粒物以及有色溶解有机物(CDOM)的吸收特性、季节变化进行了研究。研究表明,总颗粒物的吸收光谱曲线与非藻类颗粒物的吸收光谱基本保持一致并且与非藻类颗粒物的吸收[a_d(λ)]以及浮游植物的吸收[a_(ph)(λ)]都呈现显著相关。两个季节,a_d(440)均是总吸收的主要组成部分,CDOM的吸收[a_(CDOM)(440)]则大于a_(ph)(440)的贡献率,但9月a_d(440)的吸收所占比例较5月高。辽河水体非藻类颗粒物中矿物颗粒物的含量较其他一般水体要高。通过分析5月及9月的aph(440)/a_(ph)(675)发现浮游植物中辅助色素与叶绿素a浓度(Chla)的组成季节性变化不大,但其空间特征表现较为明显。另外,CDOM的吸收特性与非藻类颗粒物的吸收相似,呈现出较大的空间差异性;辽河S_(CDOM)基本小于其它河流、湖泊、河口等水体,其CDOM主要由大分子物质组成。     

洱海CDOM吸收光谱特征变化及其影响因素

为了解溶解性有机质(CDOM)光学特性及影响因素,在2018年11月至2019年10月期间采集了洱海120个表层水样本,利用紫外吸收光谱解析了CDOM的组成及来源,主成分分析法(PCA)阐明光学特性与环境因子之间的相关性。结果表明:CDOM吸收系数[a(440)]范围为0.22—0.90/m,随时间变化显著(P<0.01),营养水平差异较小(P=0.97)。[a(440)]与溶解性有机碳(DOC)关系显著(P<0.01),有利于建立遥感模型监测CDOM时空分布特征。基于芳香度(SUVA₂₅₄)、斜率比值(SR)、分子量参数(M)和吸收光谱斜率(S275—295)等吸收特征参数发现CDOM光学特性随季节变化差异显著,由非度量多维尺度(NMDS)分析可分为以下2个时期:2018年11月至2019年7月和2019年8—10月,后者CDOM的SUVA254显著低于前者。吸收特征参数表明洱海CDOM分子量较小,主要为内源产生。在不同时期,水温、pH和TP始终对CDOM吸收特征产生较大影响。文章阐明了洱海表层水体CDOM分布特征及影响因素,为洱海水体污染治理提供理...     

太湖梅梁湾夏季水体组分光谱吸收特性

2006年8月16、17日对太湖梅梁湾湖区15个样点水体进行采样,利用分光光度计和定量滤膜技术测量了水体要素CDOM、非藻类颗粒物和浮游植物的吸收系数,同时进行水质参数的测定,分别对各水体要素的光谱吸收特性进行分析,并结合水质参数建立相应的区域模式.其中,分UV-C(250～290nm)、UV-B (290～320nm)、UV-A(320～400nm)和蓝光(400～500nm)4个波段建立CDOM光谱吸收的关系模式,同时发现曲线斜率值S与440nm处吸收系数存在很好的二次函数关系,在紫外和蓝光波段R2分别达到0.958和0.835;总悬浮物的光谱吸收特征在不同深度处有些相近,有些则存在明显差异,主要是由有机和无机颗粒物剖面分布的不确定性和总悬浮物浓度所引起;非藻类颗粒物吸收系数在400～700nm的指数函数拟合斜率值S的变化范围为0.0056～0.0090nm-1(平均值(0.0070±0.0008)nm-1),各样点指数函数拟合的R2在0.91以上.在可见光波段范围各水体要素对总吸收系数的贡献大小顺序是:浮游植物＞非藻类颗粒物＞CDOM.浮游植物在蓝、绿和红光波段的平均贡献率都在0.5以上,是水体吸收的主要贡献者;在蓝、绿和红光波段,非藻类颗粒物的平均贡献率分别为0.350±0.145、0.412±0.162和0.232±0.125,CDOM的分别为0.121±0.052、0.088±0.059和0.050±0.038.     

太湖梅梁湾水体悬浮颗粒物和CDOM的吸收特性

通过测定滤膜上悬浮颗粒物和过滤液中CDOM吸光度的方法计算得到太湖梅梁湾总颗粒物和CDOM的光谱吸收系数,并计算了各吸收组份的贡献份额以及吸收与PAR衰减的比值。总颗粒物的吸收系数从400 nm到600 nm大致呈下降趋势,到675nm附近由于叶绿素a的特征吸收会出现明显峰值,峰值高低随叶绿素a浓度的变化而变化,ap(440)在3.58~9.86 m-1间变化。非藻类颗粒物和CDOM的吸收随波长增加大致按指数规律下降,ad(440)和ag(440)的变化范围分别为2.23~7.07m-1和1.06~1.70 m-1。非藻类颗粒物在400~700 nm波段的指数函数斜率Sd的平均值为(10.91±0.62)μm-1;CDOM在280~500 nm波段指数函数斜率Sg的平均值为(15.52±0.49)μm-1。浮游藻类的光谱吸收表现为在440、675 nm附近存在两个明显的峰值,分别为(2.55±1.14)、(1.34±0.69)m-1。ap(440)与TSS、OSSI、SS均存在显著性正相关,而ad(440)则只与TSSI、SS有显著性相关,aph(440)只与OSS、Chla有显著性相关。CDOM吸收系数与DOC浓度没有显著正相关,但与Chla存在显著幂函数关系,浮游藻类降解产物是水体中CDOM的重要来源之一。水体中物质吸收主要以颗粒物为主,对总吸收的贡献率在70%以上,而颗粒物中又以非藻类颗粒物占主导,一般超过40%,总吸收对漫射衰减的贡献也在40%以上。     

内陆湖泊水体固有光学特性的典型季节差异

固有光学特性是水体光学性质的重要内容,是水色反演分析模型建立的基础.本研究利用定量滤膜技术（QFT）和后向散射测量仪BB9,对太湖梅梁湾夏、冬季水体的有色可溶性有机物(CDOM)吸收系数、总悬浮物吸收系数和总悬浮物后向散射系数进行了观测.在分别对两季节水体组分吸收系数、后向散射系数光谱特征分析的基础上,阐明其季节差异性,并结合水质参数的变化,揭示导致两季节水体固有光学特性不同的原因,达到通过固有光学量反映水环境状态的目的.初步建立了后向散射系数与悬浮物浓度的关系模型,为分析模型的构建提供了参数保障.     

太湖典型草、藻型湖区紫外辐射的衰减及影响因素分析

2004年4月通过野外原位观测和实验室测定相结合的方法对东太湖和梅梁湾典型草、藻型湖区紫外辐射光谱衰减及影响因素进行了研究。结果表明,320nm(UV-B)、380nm(UV-A)的衰减系数在6.33~19.59m-1、3.41~13.64m-1间变化,对应的1%表面光强穿透深度分别为0.24~0.73m、0.35~1.35m,到达湖面的99%UV-B辐射在0.5m左右表层水就衰减完毕,东太湖和梅梁湾紫外辐射衰减系数存在明显的湖区差异;溶解性有机碳(DOC)的浓度在6.60~17.17mg/L间变化,其均值为(9.99±2.48)mg/L;375nm波长处CDOM吸收系数为1.78~6.25m-1,均值为(3.70±1.10)m-1;在短波部分CDOM吸收与DOC浓度存在显著性相关,相关性大致随波长降低而增加,320nm处的线性关系式:ad320=0.885DOC 2.182;紫外辐射衰减主要受制于水体中的CDOM浓度,衰减系数与DOC浓度、CDOM吸收系数存在显著性相关,340nm处的关系式分别为:Kd340=0.82 1.05DOC、Kd340=1.98 1.49ad340。在太湖紫外辐射衰减还要受悬浮物和叶绿素a浓度的影响,衰减系数与DOC、叶绿素a和悬浮物浓度多元回归的结果明显要高于单独与DOC浓度或CDOM吸收系数的回归结果。     

太湖梅梁湾漫衰减系数季节性差异及其主导因素

利用2006-08-16、2007-3-28和2007-11-12三次在太湖梅梁湾15个样点的观测数据,对漫衰减系数(Kd)及其影响因素的时空差异性进行分析,发现:梅梁湾地区Kd的主要决定因素是总吸收系数,后向散射作用对Kd具有一定的影响作用,但非主导作用;梅梁湾地区水体Kd影响因素的主次关系并非固定不变,而是随着水体组分的季节性变化而变化,3月份Kd的主导影响因素是非色素物质,其次是有色可溶性有机物(CDOM)、色素物质和后向散射作用,而8月份的主导影响因素是色素物质,其次是非色素物质、CDOM和后向散射作用,而11月份相对较为复杂,在440nm处主导影响因素是非色素物质,其次是色素物质、CDOM和后向散射作用,595nm处主导影响因素是非色素物质吸收作用,其次是色素物质吸收作用、后向散射作用、CDOM吸收作用,675nm处主导影响因素是色素物质,其次是非色素物质、后向散射作用和CDOM.     

“海蜇-缢蛏-牙鲆-对虾”混养池塘悬浮颗粒物结构及其有机碳库储量

为了阐明"海蜇-缢蛏-牙鲆-中国对虾"混养池塘生态系统的结构和功能特征,并为不同养殖模式的碳循环研究和发展低碳渔业提供参考,于2013年5—10月对辽宁丹东东港地区(N 39°51';E 124°09')两个该种混养池塘的悬浮颗粒物结构及其有机碳储量进行了研究。结果表明,两个实验池塘总悬浮颗粒物含量分别为(67.12±6.03)mg/L和(70.05±7.63)mg/L,其中无机悬浮颗粒物占总悬浮颗粒物的72.57%和75.49%;有机悬浮颗粒物占总悬浮颗粒物的27.43%和24.51%。有机悬浮颗粒物中,腐质及细菌占总悬浮颗粒物的27.15%和24.20%;浮游植物干重占0.15%和0.22%;浮游动物干重占0.13%和0.09%。两个实验池塘悬浮颗粒物中的总有机碳(TOC)含量分别为(7.31±1.51)mg/L和(6.42±1.31)mg/L;其中溶解有机碳(DOC)占总有机碳的76.33%和70.56%;颗粒有机碳(POC)占总有机碳的23.67%和29.44%;细菌碳占总有机碳的7.96%和7.18%;腐质碳占总有机碳的14.70%和20.90%;浮游植物碳占总有机碳的0.56%和0.95%;浮游动物碳占总有机碳的0.45%和0.41%。实验池塘中总悬浮颗粒物含量相对较高,其中无机悬浮颗粒物是主要的组成部分;细菌和腐质是有机悬浮颗粒物主要的组成部分,说明腐质链在该种养殖生态系统的物质循环和能量流动中起主要作用。     

绿藻CO2浓缩机制的研究进展

单细胞绿藻是淡水水体中浮游植物的重要组成部分,也是淡水生态系统中主要的初级生产者,其在适应外界环境CO₂浓度变化的过程中,细胞内形成了一种主动转移无机碳的机制———CO₂浓缩机制(CO₂concentrating mechanism,CCM).该机制能使细胞在核酮糖2磷酸羧化氧化酶(rubisco)固碳位点提高CO₂浓度,以增加光合作用和减少光呼吸.本文综述了这种机制中的无机碳转移模型和不同环境因子(光、温度、CO₂浓度和营养水平)对它的调控作用,以期促进深入开展浮游植物对大气CO₂浓度升高响应的研究.     

太湖春季水体固有光学特性及其对遥感反射率变化的影响

吸收特性和后向散射特性是水体重要的光学特性,同时也是建立生物光学模型的基本参数。利用2009年4月太湖春季实测数据,结合生物光学模型推导了太湖春季水体颗粒物后向散射系数,在此基础上分析了太湖春季水体的吸收特性和后向散射特性,并利用经验正交分解方法对遥感反射率变化的影响因子进行了分析。结果表明：（1）非色素颗粒物是影响太湖春季水体吸收特性的主导因子,色素颗粒物和CDOM对总吸收（不包含纯水）的贡献相对较小,且色素颗粒物在梅梁湾湖区的包裹效应明显大于其他湖区。（2）颗粒物后向散射系数与总悬浮物和无机悬浮物具有很强的相关性（相关系数均在0.88以上）,与有机悬浮物的相关性相对较弱（相关系数均在0.73以下）,且水体中多次散射对水面总辐亮度有较大的贡献,平均贡献率高达93.46%。（3）利用经验正交分解方法将遥感反射率变化光谱分解成3个正交因子,3个正交因子总共解释了约99%的遥感反射率变化信息,其中,第一正交因子解释了93%的变化信息,第二和第三正交因子分别解释了5%和1%的变化信息。通过对各正交因子与水体不同组分的吸收和后向散射系数进行相关性分析得出,颗粒物的后向散射对水面反射光谱的形成具有非常重要的影响,太湖春季水体遥感反射率的变化主要取决于无机颗粒物的吸收和后向散射,有机颗粒物对遥感反射率的变化影响较小。     

三峡库区甘井河水域牧场浮游植物群落结构及水质评价

为了解三峡库区的忠县甘井河段水域牧场生态渔业对水环境的影响, 于2013 年3、6、9 及12 月按季度对该河段4 个站点进行了浮游植物群落结构及水体理化因子的监测, 并采用生物多样性指数法和综合营养状态指数法对水体营养状况进行了评价。结果表明, 该河段浮游植物有7 门93 个属种, 其中绿藻门的物种数最多, 有37 种, 占浮游植物群落总数的39.79%, 其次为硅藻门和蓝藻门, 物种数分别为26 种和13 种,分别占浮游植物群落总数的27.96%和13.98%;浮游植物的年均丰度为757.67104 ind./L, 变化范围(3.065743.99)104 ind./L, 年均生物量为4.40 mg/L, 变化范围0.0317.67 mg/L;水体的年平均透明度为1.18 m, 叶绿素a、总磷、总氮含量分别为8.54 g/L、0.13 mg/L、1.95 mg/L;浮游植物香农多样性指数(H')、均匀度指数(J)年均值分别为2.90 和0.88, 全年综合营养状态指数值为37.5971.86, 由此推断, 甘井河水质属于中污染轻污染状态、中营养型富营养型。在鱼类生长旺季的6 月, 甘井河段养殖区内的水质优于非养殖区, 这可能与养殖区内放养滤食性鱼类有关, 证实了水域牧场没有带来水环境的污染, 反而能提高生物多样性, 在一定程度上改善了水体。       

Colorful niches of phytoplankton shaped by the spatial connectivity in a large river ecosystem: a riverscape perspective

Large rivers represent a significant component of inland waters and are considered sentinels and integrators of terrestrial and atmospheric processes. They represent hotspots for the transport and processing of organic and inorganic material from the surrounding landscape, which ultimately impacts the bio-optical properties and food webs of the rivers. In large rivers, hydraulic connectivity operates as a major forcing variable to structure the functioning of the riverscape, and--despite increasing interest in large-river studies--riverscape structural properties, such as the underwater spectral regime, and their impact on autotrophic ecological processes remain poorly studied. Here we used the St. Lawrence River to identify the mechanisms structuring the underwater spectral environment and their consequences on pico- and nanophytoplankton communities, which are good biological tracers of environmental changes. Our results, obtained from a 450 km sampling transect, demonstrate that tributaries exert a profound impact on the receiving river's photosynthetic potential. This occurs mainly through injection of chromophoric dissolved organic matter (CDOM) and non-algal material (tripton). CDOM and tripton in the water column selectively absorbed wavelengths in a gradient from blue to red, and the resulting underwater light climate was in turn a strong driver of the phytoplankton community structure (prokaryote/eukaryote relative and absolute abundances) at scales of many kilometers from the tributary confluence. Our results conclusively demonstrate the proximal impact of watershed properties on underwater spectral composition in a highly dynamic river environment characterized by unique structuring properties such as high directional connectivity, numerous sources and forms of carbon, and a rapidly varying hydrodynamic regime. We surmise that the underwater spectral composition represents a key integrating and structural property of large, heterogeneous river ecosystems and a promising tool to study autotrophic functional properties. It confirms the usefulness of using the riverscape approach to study large-river ecosystems and initiate comparison along latitudinal gradients.     

The Absorption of Light in Lakes: Negative Impact of Dissolved Organic Carbon on Primary Productivity

Colored dissolved organic matter (CDOM) absorbs a substantial fraction of photosynthetically active radiation (PAR) in boreal lakes. However, few studies have systematically estimated how this light absorption influences pelagic primary productivity. In this study, 75 boreal lakes spanning wide and orthogonal gradients in dissolved organic carbon (DOC) and total phosphorus (TP) were sampled during a synoptic survey. We measured absorption spectra of phytoplankton pigments, CDOM, and non-algal particles to quantify the vertical fate of photons in the PAR region. Area-specific rates of gross primary productivity (PP_A) were estimated using a bio-optical approach based on phytoplankton in vivo light absorption and the light-dependent quantum yield of photochemistry in PSII measured by a PAM fluorometer. Subsequently, we calculated the effects of CDOM, DOC, and TP concentration on PP_A. CDOM absorbed the largest fraction of PAR in the majority of lakes (mean 56.3%, range 36.9–76.2%), phytoplankton pigments captured a comparatively minor fraction (mean 6.6%, range 2.2–28.2%). PP_A estimates spanned from 45 to 993 mg C m^?2 day^?1 (median 286 mg C m^?2 day^?1). We found contrasting effects of CDOM (negative) and TP (positive) on PP_A. The use of DOC or CDOM as predictors gave very similar results and the negative effect of these variables on PP_A can probably be attributed to shading. A future scenario of increased DOC, which is highly correlated with CDOM in these lakes, might impose negative effects on areal primary productivity in boreal lakes.     

Optical gradients and phytoplankton production in the Mackenzie River and the coastal Beaufort Sea

We sampled a 300-km transect along the Mackenzie River and its associated coastal shelf system (western Canadian Arctic) in July–August of 2004 to evaluate the gradients in optical, phytoplankton and photosynthetic characteristics. The attenuation of photosynthetically available radiation (PAR) was best explained by coloured dissolved organic matter (CDOM) and turbidity (non-algal particles), while UV attenuation correlated most strongly with CDOM. Bacillariophyceae and Chlorophyceae dominated in the river, and shifted to Cryptophyceae and Prasinophyceae in the estuarine transition zone. In the coastal shelf waters, picoplanktonic cells dominated the surface autotrophic communities while both large and small cells occurred in the deep chlorophyll maximum. High PAR attenuation reduced the integral primary production rate in the river, while at an offshore marine site, 55% of integral production was at or below the pycnocline, under low PAR. Climate change is likely to increase the sediment and CDOM loading to these waters, which would exacerbate light limitation of photosynthesis throughout the system.     

Light absorption by phytoplankton and chromophoric dissolved organic matter in the drainage basin and estuary of the Neuse River, North Carolina (U.S.A.)

1. We examined the absorption of solar radiation by phytoplankton and chromophoric dissolved organic matter (CDOM) taking into account riparian shading in the rivers, reservoirs, swamps of the Neuse River Estuary and its drainage basin. 2. In the streams, CDOM typically absorbed 55 and 64% of photons in the spectral range of 400–700 nm (photosynthetically active radiation, PAR) and 500–600 nm, respectively. The large proportion of photons absorbed by CDOM indicates high potential for abiotic photochemial reactions in the 500–600 nm region. 3. Despite the high concentration of nutrients, phytoplankton contributed little (2%) to the total absorption of PAR in the streams. Small (<30 m wide) streams typically received only 7% of incident PAR that impinged onto the more exposed reservoirs and estuary. Riparian shading and the low contribution of phytoplankton to the total absorption resulted in conditions where phytoplankton absorbed nearly two orders of magnitude less PAR in the streams than in the estuary and reservoirs. 4. The results indicated that riparian shading and non‐algal absorbing components can significantly restrict phytoplankton production in nutrient‐rich streams with a high concentration of CDOM flowing throughout forested catchments.     

三峡正常蓄水后长江口叶绿素a和溶解氧变化及其成因

根据2010年8月、10月和2011年5月的现场监测数据,对长江口水域在三峡水库175m试验蓄水实施后一个水文年中叶绿素a和溶解氧(DO)的分布特征及其影响因素进行分析。结果表明,叶绿素a平面分布夏季有两个高值中心,春季有一个高值中心;在口门北缘夏季表层叶绿素浓度值最高。垂向上,夏季叶绿素a浓度表层和底层高;春季和秋季叶绿素a浓度中层高。夏季表层和底层DO浓度相差较大,秋季和春季表、底层DO浓度分布比较均匀;整体上秋季和春季的DO浓度高于夏季。工程蓄水后DO低值区和叶绿素a峰值区向口门内位移,对生态系统结构将产生影响。     

A study of absorption characteristics of chromophoric dissolved organic matter and particles in Lake Taihu,China

Absorptions by non-phytoplankton particles and phytoplankton, and chromophoric dissolved organic matter (CDOM) were measured at 50 sites in large, shallow, Lake Taihu in winter and summer 2006 to study their seasonal and spatial variations, and their relative contributions to total absorption. The CDOM absorption was significantly higher in winter than in summer, due to degradation and release of fixed carbon in phytoplankton and submerged aquatic vegetation (SAV). The hyperbolic model was used to model the spectral absorption of CDOM, and the mean spectral slope of 6.38 nm⁻¹ was obtained. At most sites, the spectral absorption of non-phytoplankton particles was similar to that of the total particles, demonstrating that the absorption of the total particles is dominated by the absorption of non-phytoplankton particles. In summer, phytoplankton absorption increased markedly, due to frequent algal blooms especially in Meiliang Bay. In winter, the significant increase in non-phytoplankton particle absorption resulted from the increase of inorganic particulate matter caused by sediment resuspension. Strong linear relationships were found between a _d(440) and total suspended matter (TSM), organic suspended matter (OSM), and inorganic suspended matter (ISM). Strong linear relationships were also found between a _ph(440), a _ph(675) and chlorophyll a (Chl-a) concentration. The total relative contributions of non-phytoplankton particles over the range of photosynthetically active radiation (PAR) (400–700 nm) were 48.4 and 79.9% in summer and winter respectively. Non-phytoplankton particle absorption dominated the total absorption, especially in winter, in Lake Taihu, due to frequent sediment resuspension in the large shallow lake as a result of strong windy conditions. The results indicate that strong absorption by CDOM and non-phytoplankton particles at the blue wavelength has an impact on the spectral availability, and acts as a selection factor for the composition of the phytoplankton community, with cyanobacteria being the dominate species in Lake Taihu. Handling editor: L. Naselli-Flores     

Annual dynamics and production of rotifers in an eutrophication gradient in the Baltic Sea

Spatial and temporal fluctuations in rotifer abundance have been monitored along a trophic gradient in the northern Baltic. The most common rotifer was Synchaeta spp., which had one abundance peak in June and one in September–October. Only during the latter period was the abundance significantly higher in the eutrophic basin compared to the reference area. The annual production of Synchaeta spp. was about double in the eutrophic basin. A positive correlation between Synchaeta spp. biomass and phytoplankton biomass was obtained during the autumn, but not during the early summer peak, although the phytoplankton community was dominated by the same species. Keratella quadrata, K. cochlearis and K. cruciformis were most abundant in August–September, and all three species had increased abundance in the eutrophic basin.     

Temporal and spatial variations of chemical oxygen demand in Lake Taihu,China, from 2005 to 2009

We undertook a study in Lake Taihu, China, from 2005 to 2009 including a total of 639 samples to determine: (i) the seasonal dynamics and spatial distribution of the chemical oxygen demand (COD) and (ii) the relationships between the COD concentration and the biochemical oxygen demand (BOD), phytoplankton pigment, total dissolved nitrogen (TDN), and total dissolved phosphorus (TDP) concentrations, as well as the chromophoric dissolved organic matter (CDOM) absorption coefficient. There were significant spatial differences in the COD concentration, which gradually decreased from Zhushan Bay in the northwest, to the north, the lake center, and the southeast of the lake. The COD concentration was significantly higher at near-shore sites than that at open water sites. The mean COD concentrations were significantly higher in the spring and summer than in the winter and autumn. The lowest annual mean COD concentration appeared in 2009, which could be attributed to improvements in water quality management and high rainfall. The COD concentrations in all four seasons were strongly correlated with phytoplankton pigment, suggesting that extracellular release of COD from phytoplankton was an important COD source. The correlation coefficients between the COD and phytoplankton pigment concentrations were higher in the spring, summer, and autumn than in the winter, showing a more important contribution of phytoplankton degradation to COD in the algal bloom season than in the non-algal bloom season. These new data on the temporal and spatial characteristics of the COD in Lake Taihu will be crucial for developing future strategies for water quality management.