近十年青海湖水生态系统生产总值变化及其影响因素

受气候变化和人类活动影响,湖泊水生态系统及其服务功能发生改变,研究湖泊水生态系统生产总值动态变化及其影响因素,对于维护湖泊健康生命、实现湖泊功能永续利用具有重要意义。选择位于气候敏感区和生态脆弱区的青海湖作为研究对象,根据青海湖水生态系统特征及当前保护状况,筛选调节服务及文化服务2类8个评估指标,构建湖泊水生态系统生产总值指标体系,核算2010—2020年青海湖水生态系统生产总值,分析其变化趋势及主要影响因素。结果表明,2010—2020年青海湖水生态系统生产总值总体呈波动上升趋势,变化范围为6903.47亿～7848.55亿元;调节服务是青海湖水生态系统主要的服务类型,占比高达91%。近十年,气候调节和水质净化价值有所减少,其他服务功能价值均呈增加趋势。水源涵养价值增加最多,增长760.70亿元;气候调节价值下降最多,减少658.59亿元。偏最小二乘回归分析表明,水温、水位是影响青海湖水生态系统生产总值的主要因素。气候变化影响下,水温升高引起初级生产力增加及鱼类数量增长,同时近年来水体矿化度下降有利于水生生物生长,提高了固碳释氧和物种保育价值。水位与水面面积增加引起水源涵养、洪水调蓄...     

Effects of pollen leaching and microbial degradation on organic carbon and nutrient availability in lake water

Nutrient fluxes across terrestrial-aquatic boundaries and their subsequent integration into lake nutrient cycles are currently a major topic of aquatic research. Although pollen represents a good substrate for microorganisms, it has been neglected as a terrestrial source of organic matter in lakes. In laboratory experiments, we incubated pollen grains of Pinus sylvestris in water of lakes with different trophy and pH to estimate effects of pollen input and its subsequent microbial degradation on nutrient dynamics. In this ex situ experiment, we measured concentrations of organic carbon, phosphorus and nitrogen in the surrounding water as well as microbial dynamics (bacteria and fungal sporangia) at well-controlled conditions. Besides leaching, chemical and microbial decomposition of pollen was strongest within the first week of incubation. This led to a marked increase of soluble reactive phosphorus and total dissolved nitrogen (up to 0.04 and 1.5 mg L⁻¹, respectively, after 5 days of incubation) in the ambient water. In parallel, pollen grains were rapidly colonized by heterotrophic bacteria and aquatic fungi. Leaching and microbial degradation of pollen accounted for ≥80, ≥40, ≥50% for organic C, N and P, respectively, and did not significantly differ among water samples from the studied lakes. Thus, pollen introduces high amounts of bio-available terrestrial organic matter and nutrients into surface waters within a short time. A rough calculation on P input into oligotrophic Lake Stechlin indicates that pollen plays an important ecological role in nutrient cycling of temperate lakes. This requires further attention in aquatic ecology.     

The Analysis of the Seasonal,Spatial, and Compositional Distribution of Humic Substances in a Subtropical Shallow Lake

The spatial and temporal distribution of humic substances in aquatic ecosystems can have important effects on ecosystem productivity, negatively impacting primary productivity while positively impacting secondary productivity. In the present investigation, a large shallow lake ecosystem was studied to determine the spatial and seasonal variation of the composition and concentration of humic substances. Concentrations of total dissolved organic matter, humic acid, and fulvic acid were found to display significant spatial distributions (1.3…13.5 mg/L, DOM; 0.1…5.4 mg/L, HA). The distribution is described by using mapping techniques and the analysis of the spatial distribution of the lake. An analysis of the seasonal variations also indicated the dependence of the occurrence of these compounds on meteorological and hydrological conditions. To identify the potential sources of these organic materials, an analysis was made of the ratio of humic and fulvic acid fractions and total DOM. It was found that areas of high DOM concentration coincided with the areas of highest HA percentage of total DOM. Furthermore using the ratio of the normalised concentrations of HA, FA, and residual DOM (< 5000 g/mol) it was found that areas dominated by each are spatially distinct. This confirms the hypothesis that in these shallow lakes, photodegradation and bacterioplankton activity will create a residence time dependent zonation of each component of the total DOM.     

Implementing environmental flows in integrated water resources management and the ecosystem approach

Abstract

In many of the world’s river basins, the water resources are over-allocated and/or highly modified, access to good quality water is limited or competitive and aquatic ecosystems are degraded. The decline in aquatic ecosystems can impact on human well-being by reducing the ecosystem services provided by healthy rivers, wetlands and floodplains. Basin water resources management requires the determination of water allocation among competing stakeholders including the environment, social needs and economic development. Traditionally, this determination occurred on a volumetric basis to meet basin productivity goals. However, it is difficult to address environmental goals in such a framework, because environmental condition is rarely considered in productivity goals, and short-term variations in river flow may be the most important driver of aquatic ecosystem health. Manipulation of flows to achieve desired outcomes for public supply, food and energy has been implemented for many years. More recently, manipulating flows to achieve ecological outcomes has been proposed. However, the complexity of determining the required flow regimes and the interdependencies between stakeholder outcomes has restricted the implementation of environmental flows as a core component of Integrated Water Resources Management (IWRM). We demonstrate through case studies of the Rhône and Thames river basins in Europe, the Colorado River basin in North America and the Murray-Darling basin in Australia the limitations of traditional environmental flow strategies in integrated water resources management. An alternative ecosystem approach can provide a framework for implementation of environmental flows in basin water resources management, as demonstrated by management of the Pangani River basin in Africa. An ecosystem approach in IWRM leads to management for agreed triple-bottom-line outcomes, rather than productivity or ecological outcomes alone. We recommend that environmental flow management should take on the principles of an ecosystem approach and form an integral part of IWRM.

Editor D. Koutsoyiannis

Citation Overton, I.C., Smith, D.M., Dalton J., Barchiesi S., Acreman M.C., Stromberg, J.C., and Kirby, J.M., 2014. Implementing environmental flows in integrated water resources management and the ecosystem approach. Hydrological Sciences Journal, 59 (3–4), 860–877.     

富营养化湖泊围隔中重建水生植被及其生态效应

水体富营养化导致水生植被衰退、蓝藻水华暴发、水质恶化和水生生态系统崩溃.恢复水生植被被认为是改善受损水体水质和提高其生态系统稳定性的重要手段.本研究通过构建大型围隔,根据水生植物的耐污程度及其对水质和底质等条件的需求,选取几种适宜的水生植物在围隔内进行移栽与群落构建,并以不移栽水生植物的围隔和围隔外水体作为对照.实验期间(2011年4月至2012年6月),围隔内移栽的几种水生植物全部存活,并建立了相对稳定的群落.同时还跟踪监测了3个处理组的水质情况,结果显示,移栽水生植物的围隔内水质明显优于围隔外,与未移栽水生植物围隔相比,也有很大程度的改善,其中移栽水生植物围隔内水体的总氮、铵态氮、总磷、水下消光系数相比于围隔外水体分别低30.55%、44.09%、36.04%和42.13%,相比于未移栽水生植物围隔内水体分别低5.96%、13.40%、6.70%和7.60%,透明度分别比围隔外水体和未移栽水生植物围隔水体高74.59%和8.70%,浮游植物生物量也大大低于围隔外,而浮游动物生物量却明显高于后者.此外,实验后移栽水生植物围隔内沉积物氮、磷含量及其间隙水总氮、总磷、铵态氮浓度明显低于围隔外和未移栽水生植物围隔.研究表明,在富营养化浅水湖泊中通过建立围隔进行合理的群落配置,进而逐步恢复水生植物是完全可行的,而水生植物恢复后加强对其管理和维护至关重要.     

Ecological–economic modeling as a tool for watershed management: A case study of Lake Qionghai watershed, China

This paper presents an ecological–economic model for a lake and its watershed systems. We describe the linkage between the watershed system and the lake aquatic ecosystem and the modeling process. The lake–watershed system was divided into six subsystems: social system, economic system, terrestrial ecosystem, lake water system, pollutant system, and lake aquatic ecosystem. The model equations were constructed based on five main assumptions. The Lake Qionghai watershed in southwestern China, which is undergoing rapid eutrophication, was used as a case study. The targeted goals for total phosphorus (TP) and chlorophyll a (Chl a) concentrations in the lake in 2015 are 0.025 and 10.0 mg m⁻³, respectively. We present two scenarios from 2004 to 2015 based on the ecological–economic model. In both scenarios, the TP and Chl a concentrations in the lake are predicted to increase under the effects of watershed pressures and the targeted goals cannot be met. The application of techniques to reduce pollutants loading and the corresponding pollutants reductions are reflected again in the constructed model. The model predicts that TP and Chl a concentrations will decrease to 0.024 and 7.71 mg m⁻³, respectively, which meet the targeted thresholds. The model results provide directions for local government management of watersheds and lake aquatic ecosystem restoration.     

Ecological engineering in a eutrophic lake: A case study of large aquatic macrophyte enclosures in Baima Lake,China

Ecological restoration of eutrophic lakes using aquatic macrophytes is an important and practical technology. Here, we investigated the response of phytoplankton and zooplankton to a large-scale 2015-built aquatic macrophyte enclosure (AME, 200,000 m²) screened of by a PVC net in Baima Lake, a eutrophic lake, from spring to autumn of 2019. AME significantly improved water quality by increasing water transparency, and reducing total nitrogen, total phosphorus, and chlorophyll-a content during the growing season. AME significantly decreased phytoplankton abundance and biomass and marginally increased zooplankton abundance and biomass. Phytoplankton and zooplankton communities were closely related to environmental factors, such as water temperature, conductivity, total phosphorus, chemical oxygen demand, and chlorophyll-a inside and outside the AME. The zooplankton:phytoplankton biomass ratio inside was slightly higher than outside the AME. Zooplankton and phytoplankton biomass were significantly positively correlated inside and outside the AME, as were chlorophyll-a and total phosphorus. We found phosphorus to be a key factor limiting primary productivity in Baima Lake, and that bottom-up effects were the main driver to control phytoplankton in the AME. Using aquatic macrophytes to reduce nutrient loads is an effective way to manage eutrophication in Baima Lake.     

洞庭湖和鄱阳湖水体细菌空间分布特征及驱动机制

为了探讨洞庭湖和鄱阳湖水体细菌的群落组成、空间分布特征及其驱动机制,于2017年9月,采用高通量测序技术、基于16S rRNA分子标记进行单分子测序,分别对两湖共57个位点的水体细菌群落组成进行了研究,同步监测了水体的理化指标。结果表明：洞庭湖和鄱阳湖共发现水体细菌20门42纲93目191科533属,在门水平上,洞庭湖和鄱阳湖的水体细菌组成均以放线菌门、蓝细菌门和变形菌门为主;主成分分析结果表明,两湖水环境条件有显著性差异,鄱阳湖的空间差异性大于洞庭湖;Mantel分析表明显著影响蓝细菌类群和其他类群组成的因素较为一致,在洞庭湖以物理环境因子和营养盐因子为主,而鄱阳湖以物理环境因子为主;零模型分析结果显示随机性过程为两湖水体细菌的群落构建机制的主要成分,占比分别为58.8%和79.7%。总体来说,鄱阳湖水环境空间异质性更高,水体细菌受到一些水文水动力学因子介导的物理环境因子影响,且其群落构建机制由随机性过程主导;洞庭湖水环境空间异质性较低,水体细菌受到物理环境因子和营养盐因子的共同影响,其群落构建机制由随机性过程和确定性过程共同决定。认识两湖水体细菌在空间上的分布及影响因素差异,对两湖...     

Food web manipulation without nutrient control: A useful strategy in lake restoration?

The results of long-term, full-scale experiments in biomanipulation (in the closer sense of top-down control of the food web) in water bodies having extremely different phosphorus loads reveal that there is a close connection between the efficiency of food web manipulation and the nutrient situation in the particular water body. Top-down control provides a high probability of improving water quality with respect to Secchi depth and algal biomass only if it is connected with a decrease in the in-lake phosphorus. If that decrease in phosphorus is not achieved for different reasons, the high probability of an efficient top-down control is limited to zooplankton and to structural changes in the phytoplankton. A lake-specific ‘biomanipulation-efficiency threshold’ of the phosphorus load should not be exceeded. The results show that integrated water quality control, i.e. a combination of the strategy of load reduction with the strategy of ‘ectotechnology’, seems to be a very promising way. Presented at the International Conference on Lake Restoration of Zürich, 3–4 November 1986     

POTENTIAL EFFECTS OF CLIMATE CHANGE ON AQUATIC ECOSYSTEMS OF THE GREAT PLAINS OF NORTH AMERICA

The Great Plains landscape is less topographically complex than most other regions within North America, but diverse aquatic ecosystems, such as playas, pothole lakes, ox-bow lakes, springs, groundwater aquifers, intermittent and ephemeral streams, as well as large rivers and wetlands, are highly dynamic and responsive to extreme climatic fluctuations. We review the evidence for climatic change that demonstrates the historical importance of extremes in north–south differences in summer temperatures and east–west differences in aridity across four large subregions. These physical driving forces alter density stratification, deoxygenation, decomposition and salinity. Biotic community composition and associated ecosystem processes of productivity and nutrient cycling respond rapidly to these climatically driven dynamics. Ecosystem processes also respond to cultural effects such as dams and diversions of water for irrigation, waste dilution and urban demands for drinking water and industrial uses. Distinguishing climatic from cultural effects in future models of aquatic ecosystem functioning will require more refinement in both climatic and economic forecasting. There is a need, for example, to predict how long-term climatic forecasts (based on both ENSO and global warming simulations) relate to the permanence and productivity of shallow water ecosystems. Aquatic ecologists, hydrologists, climatologists and geographers have much to discuss regarding the synthesis of available data and the design of future interdisciplinary research. © 1997 John Wiley & Sons, Ltd.     

洪湖湿地生态系统演变及稳态转换关键驱动因子阈值研究

利用1990—2020年洪湖水环境监测数据和2011—2020年洪湖沉水植物调查数据,探讨洪湖湿地生态环境演化规律,识别稳态转换关键驱动因子并确定其阈值。研究结果表明:1990—2020年以来洪湖水质变化主要总结为5个阶段和3个时期,整体上呈现出不断恶化的趋势;2011—2020年以来洪湖沉水植物Margalef物种丰富度指数、Shannon-Wiener多样性指数、Simpson和Pielou均匀度指数分别降低32%、59%、60%和46%,特别是2016年洪涝灾害后沉水植物出现严重衰退;洪湖生态系统发生稳态转换的关键时期是2002和2011年,总磷是洪湖湿地生态系统稳态转换的关键驱动因子;清水态向浊水态转换的总磷阈值为0.092 mg/L,浊水态向清水态转化的阈值为0.051 mg/L。本研究可为洪湖入湖污染负荷削减量估算提供参考,为洪湖湿地生态修复的营养盐优先控制策略提供指导。     

巢湖流域双桥河底泥疏浚对浮游甲壳动物群落结构的影响

为研究河流底泥疏浚工程对富营养化河流水生生态系统的影响,选取巢湖双桥河开展为期一年的河流生态监测与调查,对比分析了巢湖双桥河疏浚前和疏浚后的水质指标、浮游甲壳动物群落结构及生物多样性指数.研究发现：底泥疏浚后双桥河水质得到明显改善,其中氮、磷营养盐分别削减48.09%和19.09%;底泥疏浚对浮游甲壳动物群落结构影响显著,疏浚后浮游甲壳动物生物量从1.86 mg/L下降到0.25 mg/L,下降了86.40%;疏浚后生物多样性指数高于疏浚前,且受季节影响较大;浮游甲壳动物与水环境因子相关性研究发现：pH、温度、铵态氮、硝态氮、可溶性氮、总氮和氮磷比对浮游甲壳动物总生物量均有极显著影响.研究结果表明,河流底泥疏浚工程能显著削减水体中氮、磷营养盐,并从一定程度上改善河流浮游甲壳动物群落结构,促进河流水生生态系统向健康、安全的方向发展.因此,对于双桥河这种受城市外源污染影响较大的城市污染型河流,在削减外源营养盐特别是氮输入的条件下,实施底泥疏浚工程可以促进其水生生态系统的修复.     

Photochemical degradation of dissolved organic matter from streams in the western Lake Superior watershed

The input and fate of dissolved organic matter (DOM) can have important consequences for coastal zone productivity in large lakes and oceans. Chromophoric DOM (CDOM) is often delivered to coastal zones from rivers and streams and affects light penetration in a water column. CDOM can protect biota from damaging ultraviolet (UV) light by acting as sunscreen, resulting in increased ecosystem productivity. Alternatively, CDOM can decrease ecosystem productivity by absorbing light needed for photosynthesis and forming photoreaction products that are harmful to coastal zone biota. Increased urbanization of watersheds and seasonal differences in weather patterns change the delivery pathways, reactivity, input, and energy flow of DOM (and its CDOM component) into aquatic systems. This study investigated the effects of watershed and season on the concentrations and potential photodegradation of stream-derived DOM in Lake Superior tributaries, chosen to be geographically and geologically similar but differing in land use. Organic carbon analysis, UV–Visible spectrophotometry, and terrestrial (land use) analysis were used to investigate differences among samples and sample treatments. The major differences in DOM concentration and photochemical response appeared seasonal rather than site specific, with snow-melt samples showing stronger and more consistent changes in UV–Visible parameters while base-flow samples showed stronger and more consistent losses in DOC.     

Effects of ultraviolet radiation on the abundance,diversity and activity of bacterioneuston and bacterioplankton: insights from microcosm studies

The effects of ultraviolet-B (0.4 W m⁻²) radiation on the abundance, diversity and heterotrophic metabolism of bacterioneuston and bacterioplankton communities from Ria de Aveiro (Portugal) were assessed and compared to those of freshwater communities from Lake Vela (Portugal) in microcosm experiments. Exposure to 9 h of artificial ultraviolet radiation (UVR) led to 24–33% reduction in bacterial abundance and up to a 70% decrease in bacterial diversity. Maximum extracellular enzyme activity and monomer incorporation rates were reduced by 16–90% and 80–100%, respectively. Recovery of bacterial activity during post-UV dark incubations ranged from 10 to 100% for extracellular enzyme activity and 40% for monomer incorporation rates. In general, the heterotrophic activity of bacterioneuston was more inhibited by UVR than that of bacterioplankton. However, DGGE profiles revealed greater UVR-induced reductions in the diversity of bacterioplankton compared to bacterioneuston. The similarity between bacterioneuston and bacterioplankton communities in samples collected at early morning was lower than at noon (pre-exposed communities) and increased upon experimental irradiation, possibly indicating selection for UV-resistant bacteria. The observation that UV exposure resulted in enhanced reduction of bacterioneuston activity, but a lower reduction in bacterial diversity accompanied by enhanced dark recovery potential compared to bacterioplankton, indicates re-directioning of bacterioneuston metabolism towards stress defence/recovery strategies rather than the sustained heterotrophic metabolism. Our results indicate that UVR can significantly decrease the abundance, diversity and activity of bacteria inhabiting the surface and sub-surface layers of freshwater and estuarine systems with potentially important impacts on the biogeochemical cycles in these environments.     

福建敖江流域水域生态系统健康评估

以敖江流域为研究区,通过采集底栖动物、鱼类等样品,结合监测数据分析流域水域生态系统健康状况,并采用指标体系评估方法对水域生态系统进行评估.结果表明:敖江流域水质总体良好,但山仔水库总氮、总磷浓度长期超标,水体存在富营养化和藻类水华暴发生态环境问题;底栖动物种类呈现支流多于干流、河流多于水库的规律;鱼类种类上、中、下游各科物种组成差异不显著,鱼类区系特点具有较明显的热带、亚热带区系特点;流域上游、中游水域生态健康良好,下游水域生态健康一般.     

Eutrophication and drought disturbance shape functional diversity and life-history traits of aquatic plants in shallow lakes

Theories that link plant strategies and abiotic filters discriminate between three strategies: competitive, ruderal or stress-tolerant species, and suggest that functional diversity is higher at intermediate values along the gradients of productivity and disturbance. The mechanism by which abiotic filters screen plant traits in aquatic plant communities has been poorly tested and has led to contrasting results. The present study aimed to test whether functional diversity and abundance of life-history traits corresponding to morphology, fecundity and longevity of aquatic plants were linked to disturbance and productivity. Fifty-nine shallow lakes that were arranged along a gradient of productivity (estimated through total phosphorus concentration) and drought-disturbance frequency were sampled for aquatic plants. Species traits were documented and functional diversity was calculated (richness, dispersion and evenness) for each lake. Increasing total phosphorus concentration was associated with decreased functional richness and dispersion but not functional evenness. Functional diversity did not differ according to disturbance frequency, regardless of the index that was measured. High productivity favoured floating species with storage organs and vegetative reproduction, especially at low disturbance frequency. For all disturbance frequencies, low productivity favoured small species without storage organs and sexual reproduction. The present study partly supports the theoretical model. At high productivity levels, because phytoplankton is a better competitor for light than aquatic plants, plant traits are screened stringently, and species with traits that allow them to reach the photic zone are selected.     

蓝藻膦酸酯代谢及其生态意义研究进展

膦酸酯是新近发现的一类生物可利用磷,其广泛存在于水生生态系统,是水体有机磷库的重要组成,构成水体磷氧化还原循环的关键环节。随着研究的深入,越来越多的蓝藻藻株被证实参与膦酸酯的生物利用与合成,有助于阐明其适应低磷环境的机制,促进了对蓝藻磷策略与水体磷循环的全面理解,具有重要的生态学意义。与此同时,蓝藻对膦酸酯的利用性状,使得膦酸酯作为环境污染物与蓝藻磷源的双重作用开始显现,这会对水体浮游生物竞争格局的研究产生深远影响;而蓝藻的甲基膦酸代谢也被认为是水体好氧甲烷发生的来源之一。本文回顾了蓝藻膦酸酯利用与合成的研究历史,对目前蓝藻膦酸酯代谢过程生态风险与生态意义的研究进展进行了梳理,并对这一领域未来发展趋势进行了评述。     

土地利用和水环境因子对大型底栖动物次级生产力的影响:以东北地区连环湖为例

土地利用和水环境因子是影响湖泊生态系统的关键因素,探究大型底栖动物次级生产力受环境因子的作用机制,可揭示底栖动物栖息地的生态系统与外源环境的关系。为了解土地利用和水环境因子对大型底栖动物次级生产力的影响,2020年对连环湖13个主要湖泊的土地利用类型及6、8和10月的大型底栖动物、水环境因子进行调查,共采集到大型底栖动物75种,隶属于3门32科56属,其中优势种属及重要种属以摇蚊幼虫和腹足纲为主,前突摇蚊(Procladius sp.)为第一优势种。主成分分析表明,土地利用及水环境因子具备明显的时空梯度,而大型底栖动物次级生产力也存在明显的时空变化。春季、夏季、秋季次级生产力和P/B值分别为5.65、6.06、4.31 g/(m²·a)和2.74、2.55、2.40 a^-1,其中春季次级生产力集中于东北部湖区,龙虎泡集中于湖心区;夏季次级生产力逐渐向各湖区扩散,龙虎泡整体偏低;秋季次级生产力集中于西北部及东南部湖区,龙虎泡集中于东北部湖区。P/B值随季节的推移呈现由东部湖区向西部湖区逐渐递增的趋势,而龙虎泡始终集中于南部湖区。次级生产力和P/B值的结构分析表明,春季次级生产力主要由腹足纲构成,进入夏、秋季后以双壳纲对次级生产力的贡献最高。其中腹足纲、双壳纲、摇蚊幼虫和寡毛纲次级生产力主要集中于北部湖区、东南部湖区、中部湖区和龙虎泡,而甲壳纲仅出现于阿木塔泡。寡毛纲和双壳纲P/B 值随季节的推移逐渐降低,摇蚊幼虫和腹足纲P/B 值呈先升后降的趋势。通径分析表明,pH、人造地表和叶绿素a是影响年均大型底栖动物次级生产力的关键环境因子。典范对应分析表明,总磷和电导率是影响不同季节大型底栖动物次级生产力的重要环境变量。耕地、人造地表与总磷、电导率和悬浮物呈显著正相关,农业生产和城镇建设的增加是连环湖呈富营养化状态的重要原因,且此现象已对大型底栖动物次级生产力形成威胁。未来应通过控制农业面源污染、秸秆腐熟还田、鼓励粪便施肥、科学规划用地等措施改善连环湖流域的生态环境,以促进大型底栖动物资源合理的开发利用。     

Specific features of Lake Ladoga ecosystem under the effect of anthropogenic eutrophication

The evolution of Lake Ladoga ecosystem under the effect of a long period of critical anthropogenic phosphorus load is analyzed. It is shown that relatioships between organic matter accumulation and mineralization with considerable predominance of destruction over autochthonous production have formed in the lake by the moment when the input of P of anthropogenic origin dropped to the estimated admissible level. Studying the transformation of aquatic organic matter of tributaries in the water of Lake Ladoga suggest that a considerable portion of it, primarily, the conservative humic fraction, is now involved in turnover and serves as an additional source of C and P both for producer and destructor organisms. The processes taking place in Lake Ladoga suggest the allochthonous variant of ecosystem evolution.