太湖湖岸带浮游植物初级生产力特征及影响因素

利用高频溶解氧监测,估算了太湖梅梁湾湖岸带浮游植物初级生产力的高频变化特征。结合同步气象监测及浮游植物、浮游动物和营养盐的周年逐周观测数据,分析了气象和环境条件对富营养化湖泊浮游植物初级生产力的影响。结果发现,高频溶解氧监测估算的初级生产力变化与浮游藻类生物量的变化一致,能够反映出浮游植物生产力的昼夜变化、季节变化等规律。统计分析表明,气温对太湖这一富营养化湖泊初级生产力影响很大;氮的供给与浮游动物的选择性牧食也是影响浮游植物初级生产力的重要因素。湖岸带的水华堆积过程对初级生产力影响巨大,气象、水文过程又加剧了蓝藻水华初级生产力的变化幅度,反映出富营养化湖泊初级生产力可能存在极大的时空不均一性。研究表明,溶解氧高频监测法估算初级生产力能够捕捉到湖泊初级生产力的快速变化过程,可以用于富营养化湖泊初级生产力监测、蓝藻水华灾害预警中。     

龙感湖沉积物碳、氮同位素记录的环境演化

通过对龙感湖沉积物样品中δ13Corg、δ15N、有机碳与总氮比值(C/N)、总有机碳(TOC)和总氮(TN)含量的测定,分析了自1948年以来龙感湖沉积物有机质的来源,探讨了湖泊生产力变化以及随后的沉积演化过程.结果表明:在这个沉积历史阶段中,湖泊沉积物有机质以自生有机物源为主,大型水草发育,伴有低等藻类参与,湖泊沉积物受陆源输入影响较小,基本不受城市污染物的输入影响,但受流域农业化肥大量使用的影响较大;随着营养物质的输入,湖泊的初级生产力逐渐增大,藻类开始发育;在沉积历史上L2点附近低等藻类相对发育早,但L1点沉积物相对能够固定更多的营养盐.     

异龙湖近百年来湖泊沉积物有机碳、氮稳定同位素变化及其环境指示意义

通过对异龙湖沉积物岩芯(YLH-1)样品有机碳、氮及其稳定同位素、C/N值测定,结合人类活动的阶段性特征,分析了近百年来异龙湖沉积物有机质的来源,探讨受人类活动影响下湖泊的生态环境变化过程。结果表明:异龙湖沉积物中有机质的碳、氮稳定同位素分别为-25.9‰～-22.5‰和0.5‰～4.7‰,C/N值16.4～20.4,表明异龙湖有机质主要受大型水生植物影响,而藻类和陆源有机质贡献较小。δ~(13)C逐渐偏负的过程反映了异龙湖富营养化加剧的过程,可能与藻类吸收有机质降解产生的CO_2有关,而δ~(15)N的变化则与流域内工业污染物、农业化肥和大气氮沉降有关。异龙湖的生态环境变化可以分为3个阶段:19世纪80年代至20世纪60年代初期,湖泊初级生产力较低,水质好,受人类活动干扰较小; 20世纪60年代中后期至20世纪90年代,随着人类活动的加强,湖泊生产力迅速提高,富营养化程度加剧,水质恶化,藻类大量繁殖; 20世纪90年代之后,湖泊处于高生产力水平,湖泊富营养化严重。因此,未来管理部门要重视人类活动对湖泊生态环境影响,加强湖泊生态环境治理,改善湖泊生态环境。     

稳定碳同位素技术在北京市公园湖泊沉积物有机质来源分析与评价中的应用

湖泊是陆地水圈的重要组成部分,湖泊沉积物是水体污染物的源和汇,北京湖泊生态环境和环境质量评价越来越受关注。本研究对2012—2013年北京市19个公园湖泊表层沉积物中δ13Corg、C/N值及TOC、TON含量进行分析,探讨了湖泊生产力分布、湖泊营养输入、表层沉积物营养含量以及各沉积物有机质来源。结果表明,湖泊表层沉积物由于存在地域差异,δ13Corg、C/N、TOC、TON含量的差别较大、湖泊生产力与营养水平各不相同;通过有机指数评价法推断,所研究的湖泊中只有3个湖泊较清洁,其他均受到不同程度的有机污染;结合δ13Corg(-27.6‰~-22.1‰)和C/N(8.2~58.1)2个特征值对沉积物进行有机质来源的定性及半定量分析,推断出北京市公园湖泊有机质大多来源为污水有机质,应主要从控制污水输入方面降低湖泊污染风险。     

汕头南澳养殖区表层沉积物中生源要素的分布及其污染评价

于2010年9月采集南澳海域鱼类养殖区、贝类养殖区、大型藻类栽培区和对照区4个功能区表层沉积物样品,分析沉积物中生物硅(BSi)、总有机碳(TOC)、总氮(TN)和总磷(TP)4种生源要素的含量。结果表明,南澳海域生源要素含量与国内外养殖区相比属于中等水平。鱼类养殖区TOC、TN、TP的含量最高,而BSi的最高含量出现在藻类栽培区(平均含量为0.30%)。鱼类养殖区BSi、TOC、TN和TP的平均含量分别为0.24%、0.89%、0.13%和0.097%。根据沉积物中TOC/TN比值分析,发现鱼类养殖区的TOC主要来源于水生,贝类、藻类和对照区TOC则主要来源于陆源。生源要素污染评价表明,4个功能区的TN均属于Ⅱ类污染,鱼类和贝类养殖区的TP属于Ⅱ类轻度污染。     

罗非鱼对微型生态系统营养物水平的影响

本文总结了罗非鱼不同放养密度的微型生态系统中N、P浓度及P分布动态观测结果。在罗非鱼的影响下,微型生态系统中氨氮、颗粒磷和总磷浓度不同程度地高于对照组,而正磷酸盐浓度和沉积物磷的量显著地低于对照组。不同密度组某些指标的观测值虽有显著差异,但未见任何指标依罗非鱼放养密度而有规律地变动。微型生态系统中正磷酸盐浓度同浮游动、植物密度和初级生产力显著相关,氨氮浓度与浮游植物密度之间亦有显著的相关关系。然而,浮游植物密度与总磷浓度之间不存在营养级联假说所预见的下行影响,相反有前者决定于后者的上行影响的趋向。微型生态系统中P分布的变化可揭示罗非鱼促进系统中营养物循环,从而加速其富营养化的主要机制。     

乌梁素海沉积物中有机质和全氮含量分布特征

针对乌梁素海富营养化日趋严重和湿地面积逐渐萎缩,系统地研究了其生态环境地球化学效应.结果表明,乌梁素海表层沉积物中的全氮含量存在明显的经向和纬向分异特征;沉积物中全氮养分含量与有机质含量显著相关(r＞0.93);沉积物中C/N的平均值介于12.07～19.95之间,表明有机质主要来源于湖中水生植物,水体富营养化具有显著的内源性.TN和有机质在不同粒级表层沉积物中的粒度效应明显,且TN和有机质在IV粒级的含量分别为I粒级的3.1～7.6倍和2.5～8.0倍.     

湖泊沉积中碳酸盐、有机质及其同位素的古气候意义

综述了近几十年来国内外湖泊沉积在全新世尺度上碳酸盐及其同位素、有机质及其同位素的研究进展.主要讨论了湖泊沉积物中碳酸盐含量、δ13Ccarb和δ18Ocarb的环境意义以及二者之间的协同变化,生物成因碳酸盐及其同位素和微量元素等的影响因素及所指示的环境意义,湖泊沉积物中有机质及其同位素和C/N等的影响因素及所指示的气候信息,同时文中还讨论了碳酸盐含量、有机质及其同位素在古气候重建中的应用.     

菹草附着物对营养盐浓度的响应及其与菹草衰亡的关系

在菹草衰亡阶段对5个静水水体中菹草叶片表面附着物进行野外调查,并将其与水体营养盐浓度、沉水植物衰亡程度进行相关性分析。附着物共调查Chl.a含量、干重、有机质含量和藻类数量4个指标,沉水植物衰亡程度用单位面积叶片Chl.a含量表示,水体营养盐含量测量了TP、TN和N/P 3个指标。结果显示：附着物生物量与水体营养盐状况存在一定的正相关;各个点的附着物生物量与菹草衰亡状况存在一定相关性但相关性趋势与水体污染程度有关。在污染程度较高的水体中附着物生物量与菹草衰亡程度呈正相关,在污染程度较低的水体中附着物生物量与菹草衰亡程度呈负相关。结论为富营养化湖泊中营养盐含量的增加会导致附着物生物量的增加,但附着物只在污染程度较高的水体中促进植物衰亡。     

巢湖碳氮地球化学沉积记录揭示全新世以来的环境演化

通过对巢湖湖泊沉积物的总有机碳（TOC）、总氮（TN）、有机碳同位素（δ¹³C_org）、氮同位素（δ¹⁵N）和粒度参数的研究，重建了全新世以来湖泊初级生产力的变化，从而揭示了巢湖地区全新世环境变化历史。早全新世时期（10100-8200 cal a BP），较高的TOC和TN、在波动中逐渐升高的δ¹³C_org值以及高δ¹⁵N值、高黏土（<4 μm）含量指示了较高的湖泊初级生产力，反映气候温暖较湿；中全新世时期（8200-4200 cal a BP），TOC、TN、δ¹³C_org值和黏土（<4 μm）含量总体上较高但呈波动降低趋势，粉砂（4-64 μm）含量升高，δ¹⁵N值总体较低但变化幅度较大，指示初级生产力由较高水平开始逐渐降低，气候由温暖湿润逐渐向凉干方向发展；7300-5800 cal a BP和4300-3800 cal a BP的低δ¹⁵N和高TN值可能受到固氮蓝藻的影响，分别对应着7500-7000 cal a BP和4200-4000 cal a BP气候事件时期夏季风强度的减弱；晚全新世前期（4200-2000 cal a BP），TOC、TN、δ¹³C_org值、黏土（<4 μm）含量的低值和较高的δ¹⁵N值、高粉砂（4-64 μm）含量代表初级生产力继续降低，气候环境进一步向冷干转变。全新世以来湖泊初级生产力的逐渐下降反映了季风的逐步减弱，而逐渐减少的30°N夏季太阳辐射是驱动季风减弱的主要因素。晚全新世后期（2000 cal a BP至今），各环境代用指标的变化表现出不同于全新世环境演化趋势的异常，说明湖泊环境及沉积物受人类活动的影响加剧。     

Eutrophication of mountain lakes in Japan due to increasing deposition of anthropogenically produced dust

Atmospheric dust has wide-reaching effects, not only influencing climate conditions, but also ecosystems. The eastern region of the Asian continent is one of the largest emitters of dust in the world, and recent economic growth in the region has been accompanied by an increase in anthropogenic emissions. However, the effects of increased Asian dusts on aquatic ecosystems are not well understood. We examined fossil pigments and zooplankton remains from ²¹⁰Pb-dated sediments taken from high mountain lakes of Hourai-Numa and Hachiman-Numa, located in the Towada-Hachimantai National Park of Japan Islands, to uncover historical changes in the phyto- and zooplankton community over the past 100?years. Simultaneously, we measured the geochemical variables of TOC, TN, TP, ??¹³C, ??¹⁵N, and lead isotopes (²⁰⁷Pb/²⁰⁶Pb, ²⁰⁸Pb/²⁰⁶Pb) in the sediments to identify environmental factors causing such changes. As a result, despite few anthropogenic activities in the watersheds, alpine lakes in Japan had increased algal and herbivore plankton biomasses by 3?C6 fold for recent years depending on the surrounding terrestrial vegetation and landscape conditions. Biological and biogeochemical proxies recorded from the lake sediments showed that this eutrophication occurred after the 1990s when P deposition increased as a result of atmospheric loading of dust transported from the Asian continent. The continued increase of anthropogenically produced dust may therefore impart damaging impacts on mountain ecosystems even if they are protected from direct anthropogenic disturbances.     

Emerging understanding of the ecosystem silica filter

The annual fixation of dissolved Si (DSi) into terrestrial vegetation has been estimated to range from 60 to 200 Tmole, or 10–40 times more than the yearly export of DSi and biogenic Si (BSi) from the terrestrial geobiosphere to the coastal zone. Ecosystems form a large filter between primary mobilization of DSi from silicate weathering and its eventual export to the oceans, and a large reservoir of BSi accumulates in aquatic and terrestrial ecosystems. Although a number of synthesis activities within the last decade have discussed biological transformations in the terrestrial Si cycle, the timescales at which BSi is stored and recycled within ecosystems, BSi persistence and reactivity throughout soil profiles, the dependence of the BSi storage and recycling on ecological processes, the feedbacks to hydrology, the interaction with man’s activities and ultimately the global relevance in Si budgets are poorly constrained. Here we discuss 5 key controls on the ability of ecosystems to filter and control the export of DSi: ecosystem biodiversity, BSi dissolution rates and reactivity, hydrology, interaction with the geosphere and anthropogenic impacts. These controls need to be further studied to better quantify the global and local importance of the terrestrial biogeochemical Si cycle and specifically the BSi reservoir in ecosystems.     

Impact of eutrophication on the carbon stable‐isotopic baseline of benthic invertebrates in two deep soft‐water lakes

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The response of phytoplankton community to anthropogenic pressure gradient in the coastal waters of the eastern Adriatic Sea

In order to test the response of phytoplankton to anthropogenic pressure, data of chlorophyll a concentration, phytoplankton abundance, and composition are analyzed in relation to anthropogenic pressure gradient and environmental variables such as temperature, salinity and nutrients. Investigated sites encompassed wide tropic range according to a preliminary determination of anthropogenic pressure, quantified through the LUSI index. Statistical analyses indicated nitrates and silicates as proxies of freshwater influence, and phytoplankton single metrics such as concentrations of chlorophyll a and abundances as indicators of anthropogenic pressure. Boundary values for different water quality classes for coastal waters under indirect freshwater influence (Type II) are obtained according to gradient between concentration of chlorophyll a and pressure index (LUSI), which empirically fit to exponential equation. The response of phytoplankton diversity was not linear, as the highest diversity was observed in the area with intermediate disturbance level. CCA analysis identified Skeletonema marinoii, Scrippsiella trochoidea, Guinardia flaccida, Leptocylindrus spp., Prorocentrum spp., Proboscia alata, Eutreptiella spp., and Pseudonitzschia spp. as local eutrophication indicators, whose abundances increased with nutrients loads.     

Contribution of phytoliths to the suspended load of biogenic silica in the Nyong basin rivers (Cameroon)

Particulate biogenic silica (BSi) carried by rivers to estuaries and marine sediments is generally assumed to be primarily composed of diatoms. Phytoliths – biogenic opal formed in plants – are found in some marine sediments where they are interpreted to be the result of atmospheric and river inputs. In this study, we evaluate the contribution of phytoliths to the suspended load of rivers of the Nyong basin (Cameroon). BSi (2 μm to 2 mm fraction) in the soils and the rivers range respectively, from 0.9 to 3.9 wt% and from 1.3 to 4 wt%. About 90% of the BSi pool in both soils and river suspended load are composed of phytoliths. Thecamoebians and fresh water diatoms are minor components. The concentrations of BSi and the phytolith assemblages show great similarities between the waters and the soil samples. This result implies that the erosion of top soils is the major source of the suspended load, in good agreement with the transport-limited weathering regime of the study basin.     

Effects of Holocene Alnus Expansion on Aquatic Productivity, Nitrogen Cycling, and Soil Development in Southwestern Alaska

Numerous pollen records provide evidence for the widespread range expansion of Alnus throughout Alaska and adjacent Canada during the middle Holocene. Because Alnus can fix atmospheric N₂, this vegetational change probably had a profound effect on N availability and cycling. To assess this effect, we analyzed a sediment core from Grandfather Lake in southwestern Alaska for a suite of geochemical indicators, including elemental composition, biogenic silica (BSi) content, and carbon (C) and nitrogen (N) isotopes of organic matter. These data, in conjunction with a pollen record from the same site, are used to infer biogeochemical processes associated with the mid-Holocene Alnus expansion. The increase in Alnus pollen percentages from 10% to 70% circa 8000-7000 BP (¹⁴C years before present) suggests the rapid spread of Alnus shrub thickets on mountain slopes and riparian zones in the Grandfather Lake region. Coincident with this vegetational change, the mean value of the sediment BSi content increases from 20.4 to 106.2 mg/g, reflecting increased diatom productivity within the lake as a result of Alnus N₂ fixation in the watershed soils and the associated N flux to the lake. Elevated aquatic productivity at this time is also supported by increased percentages of organic C and N, decreased C:N ratios, and decreased values of δ ¹³C. Furthermore, the δ ¹⁵N values of sediments increase substantially with the establishment of Alnus shrub thickets, suggesting enhanced N availability and accelerated N cycling within the lake and its watershed. Superimposed on a general trend of soil acidification throughout the postglacial period, soil acidity probably increased as a result of the Alnus expansion, as can be inferred from decreasing ratios of authigenic base cations to allogenic silica (Si) and increasing ratios of authigenic aluminum (Al) to allogenic Si. The ultimate cause of these mid-Holocene ecosystem changes was an increase in effective moisture in the region. Received 21 July 2000; accepted 3 January 2001.     

Stable isotope analyses on archived fish scales reveal the long‐term effect of nitrogen loads on carbon cycling in rivers

Stable isotope analysis of organic matter in sediment records has long been used to track historical changes in productivity and carbon cycling in marine and lacustrine ecosystems. While flow dynamics preclude stratigraphic measurements of riverine sediments, such retrospective analysis is important for understanding biogeochemical cycling in running waters. Unique collections of riverine fish scales were used to analyse δ¹⁵N and δ¹³C variations in the food web of two European rivers that experience different degrees of anthropogenic pressure. Over the past four decades, dissolved inorganic N loading remained low and constant in the Teno River (70°N, Finland); in contrast, N loading increased fourfold in the Scorff River (47°N, France) over the same period. Archived scales of Atlantic salmon parr, a riverine life‐stage that feeds on aquatic invertebrates, revealed high δ¹⁵N values in the Scorff River reflecting anthropogenic N inputs to that riverine environment. A strong correlation between dissolved inorganic N loads and δ¹³C values in fish scales was observed in the Scorff River, whereas no trend was found in the Teno River. This result suggests that anthropogenic N‐nutrients enhanced atmospheric C uptake by primary producers and its transfer to fish. Our results illustrate for the first time that, as for lakes and marine ecosystems, historical changes in anthropogenic N loading can affect C cycling in riverine food webs, and confirm the long‐term interactions between N and C biogeochemical cycles in running waters.     

人为营养物质输入对汉丰湖不同营养级生物的影响--稳定C、N同位素分析

以长江一级支流小江上游的汉丰湖为研究对象,设置了4个采样点(影响组:A, B;对照组:C, D),应用碳、氮稳定性同位素探讨人类生活污水和农业面源污染对汉丰湖水生生态系统中不同营养级水平生物类群的影响。结果表明:影响组POM(颗粒有机物)和螺类碳、氮稳定性同位素比值范围分别为-25.93‰--24.63‰、4.12‰-9.86‰,-14.28‰--21.60‰、7.97‰-19.99‰;对照组POM(颗粒有机物)和螺类碳、氮稳定性同位素比值范围分别为-25.62‰--22.51‰、0.01‰-6.56‰,-22.96‰--19.21‰、6.75‰-8.89‰;不同组间POM和初级消费者螺类碳同位素比值无明显空间变化(P>0.05), 而氮稳定性同位素比值空间变化显著(P<0.05)。因此,在汉丰湖食物网中,氮稳定性同位素特征更好地反应了营养物质(人为输入)吸收和富集的信息。与固着藻类、鱼类等相比,POM和软体动物螺类更适合作为环境评价的指示物。影响组A、B样点的部分生物类群已经受到了人为营养物质输入的影响,影响强度B样点区域>A样点区域。结果建议加强汉丰湖水环境保护,控制污水排放量及提高污水处理水平,对于保护小江和三峡库区水质具有十分重要的意义。     

Response of estuarine phytoplankton to nutrient and spatio-temporal pattern of physico-chemical water quality parameters in Little Vermilion Bay,Louisiana

We studied the response pattern of phytoplankton to nutrient concentrations in Little Vermilion Bay, Louisiana in July and November 2013. It is important to understand the response of phytoplankton to nutrient concentrations in order to find impacts of eutrophication and improve the water quality for survival of fish and other aquatic life. Total Nitrogen and Total Phosphorus were measured in Little Vermillion Bay at several sampling locations along with some other water quality parameters and response of phytoplankton biomass was evaluated. The spatial–temporal pattern of water quality parameters in the study area was assessed using a spatial interpolation method. Phytoplankton biomass was positively correlated with nutrient enrichment in Little Vermillion Bay. Chlorophyll a concentrations were found to be strongly dependent on Total Nitrogen and Total Phosphorus in the water column. Nutrient concentration in the water column has a strong control over phytoplankton biomass and primary production. The TN:TP ratio was evaluated to establish the limiting nutrient for eutrophication in the study area. Both nitrogen and phosphorus were found to have strong relationships with phytoplankton growth and a growth limiting nutrient was not established for Little Vermilion Bay.