Eutrophication Of Aquatic Ecosystems Research Articles

Responses of Degraded Tibetan Kobresia Pastures to N Addition

AbstractKobresia pastures on the Tibetan Plateau are the largest alpine pastoral ecosystems. Kobresia pastures have experienced severe degradation in recent decades, inducing large nitrogen (N) losses from these ecosystems. This is particularly problematic, as it intensifies prevailing N limitation in these regions. Simultaneously, anthropogenic N deposition has increased across these ecosystems, but the fate of added N on variously degraded Kobresia pastures remains unclear. Kobresia pastures of three degradation stages were investigated: living, dying and dead root mats. High and very low (as a tracer) amounts of 15N‐labelled ammonium nitrate (NH4NO3) were applied to root mats under controlled conditions. Leaching was simulated over 3 months, and 15N recovery was measured in the plant–soil system. N addition promoted aboveground biomass and foliar N content of Kobresia during the early growth period, indicating a short‐term offset of N limitation. After 7–8 weeks, plant growth and 15N uptake were reduced in plants with initial N addition, reflecting a transition to N limitation induced by N uptake and leaching from soil. This limitation was also indicated by the strong decline of NO3− in leachates from living root mats compared with degraded root mats. Leaching N losses from dying and dead root mats increased 2⋅2 and 6⋅3 times, respectively, compared with those of living root mats. We conclude that N addition can facilitate plant growth in living root mats but contributes to N leaching in degraded pastures. This contribution to N leaching may weaken ecosystem recovery, increase NO3− loading of adjacent lower landscape parts and cause eutrophication of aquatic ecosystems. Copyright © 2017 John Wiley & Sons, Ltd.

Response of Microcystis aeruginosa BCCUSP 232 to barley (Hordeum vulgare L.) straw degradation extract and fractions

The eutrophication of aquatic ecosystems is a serious environmental problem that leads to increased frequency of cyanobacterial blooms and concentrations of cyanotoxins. These changes in aquatic chemistry can negatively affect animal and human health. Environment-friendly methods are needed to control bloom forming cyanobacteria. We investigated the effect of Hordeum vulgare L. (barley) straw degradation extract and its fractions on the growth, oxidative stress, antioxidant enzyme activities, and microcystins content of Microcystis aeruginosa (Kützing) Kützing BCCUSP232. Exposure to the extract significantly (p<0.05) inhibited the growth of M. aeruginosa throughout the study, whereas only the highest concentration of fractions 1 and 2 significantly (p<0.05) reduced the growth of the cyanobacterium on day 10 of the experiment. The production of reactive oxygen species (ROS), lipid peroxidation and antioxidant enzyme activities were significantly (p<0.05) altered by the extract and fractions 1 and 2. Phytochemical profiling of the extract and its fractions revealed that the barley straw degradation process yielded predominantly phenolic acids. These results demonstrate that barley straw extract and its fractions can efficiently interfere with the growth and development of M. aeruginosa under laboratory conditions.

Effects of snails, submerged plants and their coexistence on eutrophication in aquatic ecosystems

Eutrophication resulting from nutrient loading to freshwater habitats is a severe problem, leading to degradation of ecosystems, including deterioration of water quality, water clarity and loss of biodiversity. Measures enacted to restore degraded freshwater ecosystems often involve the reintroduction of submerged plants and aquatic animals with beneficial ecological functions. In a mesocosm experiment, three treatments (planting with Vallisneria natans , introduction of the snail Bellamya aeruginosa and a combined treatment with both plants and snails) were compared with controls to evaluate their effects on trophic state. The total nitrogen (TN), total phosphorus (TP) and chlorophyll a (Chl a ) concentrations of planktonic and benthic algal samples were determined every two weeks, along with light intensity at the sediment surface. The plant-only treatment significantly reduced the TN levels and planktonic and benthic algal biomass and increased the light intensity at the sediment surface. The snail-only treatment reduced the concentrations of TN and reduced planktonic and benthic algal biomass. The combined treatment decreased the concentrations of TN and TP, reduced planktonic algal biomass and increased the light intensity on the sediment surface. The results indicate that while submerged plants and snails can both improve water quality, the most pronounced effect in aquatic ecosystems is achieved by their presence in combination. A combined reintroduction approach may provide enhanced benefits in restoring the eutrophic ecosystems, following the reduction of external nutrient loading.

Characterization of akinetes from cyanobacterial strains and lake sediment: A study of their resistance and toxic potential

Nostocalean cyanobacteria are known to proliferate abundantly in eutrophic aquatic ecosystems, and to produce several cyanotoxins, including anatoxin-a. In this study, we investigated both the resistance and toxic potential of the akinetes (resistant cells), using cyanobacterial cultures and akinetes extracted from the sediment of Lake Aydat (France) sampled in the winter and spring. Intact and lysed akinetes were differentiated using a double control based on the autofluorescence of akinetes and SYTOX-green staining. The percentage of resistant akinetes found in several different abiotic stress conditions was highly variable, depending on the species and also on the sampling season. Thus, the resistance of akinetes and their ability to germinate seems to follow a species-specific process, and akinetes can undergo physiologic changes during the sedimentary phase of the Nostocale life cycle. This study also revealed the first evidence of anatoxin-a genes in akinetes, with anaC and anaF genes detected in akinetes from all cyanobacterial producer cultures. The low number of anaC genes, almost exclusively detected using nested PCR, in the sediment at Lake Aydat suggests a limited but existent past population of toxic Nostocales in this lake. Given the key role of akinetes in the annual cycle and subsequent summer proliferation, it can be interesting to integrate the surveillance of akinetes in the management of lakes exposed to recurrent cyanobacterial blooms.

Process evaluation of energy requirements for feed production using dairy wastewater for algal cultivation: Theoretical approach

Dairy production is an intensive agricultural practice that elicits many environmental concerns including noxious emissions, potential health risks to nearby human communities and eutrophication of aquatic ecosystems. These environmental impacts can be reduced by using the emissions and dissolved nutrients including nitrogen available in dairy wastewaters to produce algal biomass, which can be recycled for animal feed with higher protein content compared to alfalfa. However, energy demand is a major criterion for selecting an algal biomass cultivation system. Traditionally algae have been cultivated in raceways to minimize energy input, but raceways tend to have lower areal biomass productivity compared to photobioreactors. However, higher productivity may be achievable through growth in innovative designs utilizing gravity to provide reduced cultivation depths and temperature control strategies. The feasibility of animal feed production in raceways is compared to gravity fed production systems for evaluating production cost and direct energy demand. Agricultural style gravity fed production systems have an estimated cultivation energy consumption of 25Whm−2d−1 compared to raceways at 15.4Whm−2d−1. However, these systems can significantly increase areal biomass productivities reducing the energy required for biomass production from 2.01kWhkg−1 to 1.41kWhkg−1. Total cost of energy for biomass cultivation and harvesting, when sedimentation is combined with centrifugation to achieve 25% solid content, is estimated to be $176 and $256 per mton in gravity fed systems and raceways, respectively. This can be compared to $334 and $1407 per mton of biomass when only using centrifugation for processing in gravity fed systems and raceways, respectively.

Interactions of metal oxide nanoparticles with extracellular polymeric substances (EPS) of algal aggregates in an eutrophic ecosystem

Nanoparticle binding with organic ligands in natural waters is important to understand their environmental behavior and fate. In this study, the interaction of two metal oxide nanoparticles (nano-CuO and nano-Fe3O4) with extracellular polymeric substances (EPS) from algal aggregates was studied through using fluorescence emission-excitation matrix (EEM) quenching titration combined with parallel factor (PARAFAC) analysis. Spectroscopy analysis detected two protein-like peaks in the loosely bound EPS (LB–EPS) fraction, while both protein-, fulvic- and humic-like peaks can be found in the tightly bound EPS (TB–EPS) fraction. PARAFAC analysis identified three independent fluorescence components, including one tryptophan-, one tyrosine- and one humic-like component, from 68 original EEM spectra. A quenching experiment showed that humic-like components in the TB–EPS fraction exhibited higher nanoparticle binding capacities (logKM>6.23) than that in the LB–EPS fraction (logKM: <5.72), while tryptophan-like components were characterized with a high nano-CuO affinity in the LB–EPS fraction (logKM: 5.66). Further analysis revealed that the LB–EPS fraction was responsible for the transportation of nano-CuO (logKM>5.66), while the mobility of nano-Fe3O4 would be influenced by organic ligands in the TB–EPS fraction (logKM>6.28). Based on the results, the toxicity of nanoparticles in the eutrophic waters would be higher than those in the oligotrophic ecosystems. This study facilitates a deeper understanding of the environmental behavior and fate of metal oxide nanoparticles in eutrophic aquatic ecosystems.

Nitrogen dynamics in managed boreal forests: Recent advances and future research directions.

Nitrogen (N) availability plays multiple roles in the boreal landscape, as a limiting nutrient to forest growth, determinant of terrestrial biodiversity, and agent of eutrophication in aquatic ecosystems. We review existing research on forest N dynamics in northern landscapes and address the effects of management and environmental change on internal cycling and export. Current research foci include resolving the nutritional importance of different N forms to trees and establishing how tree–mycorrhizal relationships influence N limitation. In addition, understanding how forest responses to external N inputs are mediated by above- and belowground ecosystem compartments remains an important challenge. Finally, forestry generates a mosaic of successional patches in managed forest landscapes, with differing levels of N input, biological demand, and hydrological loss. The balance among these processes influences the temporal patterns of stream water chemistry and the long-term viability of forest growth. Ultimately, managing forests to keep pace with increasing demands for biomass production, while minimizing environmental degradation, will require multi-scale and interdisciplinary perspectives on landscape N dynamics.

The environmental impacts of home and community gardening.

Abstract Gardening has been practiced by humans for food and aesthetic purposes for thousands of years. As urbanization intensifies globally, gardening is increasing in both popularity and extent in urban and suburban regions of the world, thus increasing its impact on the environments. Here we discuss the health benefits and risks of home-grown vegetables followed by an in-depth examination of how home and community gardening impacts the biological and physical environments of the world with a focus on North America. In addition to offering multiple health benefits, gardens may promote biodiversity by providing critical habitats for a variety of native plant and animal species. At the same time, gardening has the potential to alter cycles of carbon, nutrients and water in urban and suburban areas, consequently contributing to global environmental changes. Conversely, gardening may have a range of adverse impacts on the environment, for instance, higher nutrient runoff and increased risk of eutrophication in aquatic ecosystems. Intensive lawn care, particularly in North America because of its large lawn areas, could divert essential resources, such as manpower, fertilizers and water, away from more ecologically and economically important activities. Exotic plants commonly grown in home gardens could escape cultivation and become noxious in their non-native habitats as already demonstrated by an increasing number of ornamental species, such as Callery pear and non-native honeysuckle, in the USA. As the world becomes more and more urbanized, the increasingly popular gardening will have greater impact on the abiotic and biotic environments of the world.

PH-dependent phosphatization of ZnO nanoparticles and its influence on subsequent lead sorption

Phosphatization of ZnO nanoparticles (ZNPs) at various pHs and its influence on subsequent lead sorption were investigated. Results showed that, in presence of phosphate, both the chemical speciation and crystalline phase of ZNPs were pH dependent that most of them were converted to crystalline Zn3(PO4)2 at acidic pHs, but only little amorphous hopeites can be formed under alkaline condition. Phosphatization process significantly enhanced subsequent lead sorption with the order of acidic process > alkaline > pristine ZNPs. Spectroscopic analysis including ATR-FTIR and XPS revealed main mechanisms of lead phosphate precipitation and inner-sphere complexes for lead sorption on acidic and alkaline treatment products, respectively. The potential toxicity of ZNPs and heavy metals in eutrophic aquatic ecosystems would thus be reduced due to the ubiquitous phosphatization process. This study highlights the importance of environmental variables in exploring the environmental behavior and fate of heavy metals as well as nanoparticles in natural waters.

A multi-stable isotope framework to understand eutrophication in aquatic ecosystems

Eutrophication is a globally significant challenge facing aquatic ecosystems, associated with human induced enrichment of these ecosystems with nitrogen (N) and phosphorus (P). However, the limited availability of inherent labels for P and N has constrained understanding of the triggers for eutrophication in natural ecosystems and appropriate targeting of management responses. This paper proposes and evaluates a new multi-stable isotope framework that offers inherent labels to track biogeochemical reactions governing both P and N in natural ecosystems. The framework couples highly novel analysis of the oxygen isotope composition of phosphate (δ18OPO4) with dual isotope analysis of oxygen and N within nitrate (δ15NNO3, δ18ONO3) and with stable N isotope analysis in ammonium (δ15NNH4). The River Beult in England is used as an exemplar system for initial evaluation of this framework. Our data demonstrate the potential to use stable isotope labels to track the input and downstream fate of nutrients from point sources, on the basis of isotopic differentiation for both P and N between river water and waste water treatment work effluent (mean difference = +1.7‰ for δ18OPO4; +15.5‰ for δ15NNH4 (under high flow); +7.3‰ for δ18ONO3 and +4.4‰ for δ15NNO3). Stable isotope data reveal nutrient inputs to the river upstream of the waste water treatment works that are consistent with partially denitrified sewage or livestock sources of nitrate (δ15NNO3 range = +11.5 to +13.1‰) and with agricultural sources of phosphate (δ18OPO4 range = +16.6 to +19.0‰). The importance of abiotic and metabolic processes for the in-river fate of N and P are also explored through the stable isotope framework. Microbial uptake of ammonium to meet metabolic demand for N is suggested by substantial enrichment of δ15NNH4 (by 10.2‰ over a 100 m reach) under summer low flow conditions. Whilst the concentration of both nitrate and phosphate decreased substantially along the same reach, the stable isotope composition of these ions did not vary significantly, indicating that concentration changes are likely driven by abiotic processes of dilution or sorption. The in-river stable isotope composition and the concentration of P and N were also largely constant downstream of the waste water treatment works, indicating that effluent-derived nutrients were not strongly coupled to metabolism along this in-river transect. Combined with in-situ and laboratory hydrochemical data, we believe that a multi-stable isotope framework represents a powerful approach for understanding and managing eutrophication in natural aquatic ecosystems.

Global changes and the new challenges in the research on cyanotoxin risk evaluation

Global c hanges and the new challenges in the research on cyanotoxin risk evaluation Global changes comprehend a series of changes in populations, climate, economy, atmospheric and oceanic circulations, water cycle, pollution, biodiversity among many others that have significant impacts in the eutrophication of aquatic ecosystems and consequently on the occurrence of bloom forming toxic cyanobacteria and on their toxins. The development of sensitive and specific techniques together with an increased effort in the research related to cyanobacteria and cyanotoxins has contributed to a significant increase on the knowledge of these toxins. The understanding of the dynamics of cyanotoxins along food chains and about their biological activity allows us to estimate environmental and human health risks. Nevertheless, there is still much to do in what concerns with effective management measures and risk communication concerning cyanotoxins. Scientists, environmental and health technicians as also politicians and common population should all be involved so as to minimize animal and humans intoxications due to cyanotoxins. In this paper we discuss also the challenges for the scientists working on cyanotoxins and also the future needs in terms of research so as to minimize risks.

Lake Taihu, a large, shallow and eutrophic aquatic ecosystem in China serves as a sink for chromophoric dissolved organic matter

Abstract Photochemical reactions and microbial activity often result in chromophoric dissolved organic matter (CDOM) being lost to downstream cycles. The role of a specific lake ecosystem serving as a sink for CDOM was elucidated in Lake Taihu, China. The lake was divided into CDOM-enriched and CDOM-depleted regions based on principal component analysis (PCA) results. The spatial distribution of molecular size ( M ), spectral slope ratio ( S R ) and humification index (HIX) of CDOM suggested that CDOM in Lake Taihu was mainly from exogenous sources. Parallel factor analysis (PARAFAC) identified four components, including a microbially humic-like component (C1), two protein-like components (C2 and C3) and a terrestrial humic-like component (C4). Strong conservative mixing behaviors of C4 and C1 were observed in the lake, and River Yincun is likely responsible for high CDOM concentration in Zhushan Bay. Compared with C2, C3 seemed to be more independent of the terrestrial humic-like CDOM. HIX decreased and S R increased significantly from the CDOM-enriched region to the CDOM-depleted region ( t -test, p a (350), dissolved organic carbon (DOC) and summed fluorescence intensity of the four components in the CDOM-enriched region were significantly higher than in the CDOM-depleted region ( t -test, p 9 m 3 m − 1 yr − 1 and 16.91 × 10 3 t yr − 1 , respectively.

Long-term trends in nitrogen and phosphorus concentrations in the Hii River as influenced by atmospheric deposition from East Asia

Deposition of atmospheric nutrients is known to alter oligotrophic ecosystems such as the open ocean, but the role of such nutrients in the further deterioration of eutrophic aquatic ecosystems is largely unknown. The Hii River watershed in Japan encompasses lagoons that have been eutrophic since 1980s. This study examined the atmospheric deposition of nitrogen and phosphorus in the Hii River watershed and the nitrogen and phosphorus concentrations in the Hii River over an 11-yr period. Total nitrogen (TN) concentrations of both precipitation and river water were significantly higher in cold months (November–March) than in warm months (April–October). Most of the TN was nitrate, which suggests that the TN source was atmospheric nitrogen from East Asia transported by seasonal winds. In contrast, total phosphorus (TP) concentrations of both precipitation and river water were significantly higher in warm months. Over time, the TN concentration in the river water showed a decreasing trend although the trend was not significant, while the TP concentration increased significantly. This was attributed to an increase in the atmospheric deposition of TP originating from East Asia since 2000. The increase in the deposition of atmospheric phosphorus might also have increased phosphorus leakage from the soils. In this work, the TN : TP ratios for both atmospheric deposition and river water indicate that changes in atmospheric nutrient deposition affect loading rates and N : P ratios. These changes, especially the latter, could have significant ecological effects in eutrophic systems by lowering the N : P ratios, which could induce cyanobacteria blooms.

Comparison of sampling methodologies for nutrient monitoring in streams: uncertainties, costs and implications for mitigation

Abstract. Eutrophication of aquatic ecosystems caused by excess concentrations of nitrogen and phosphorus may have harmful consequences for biodiversity and poses a health risk to humans via water supplies. Reduction of nitrogen and phosphorus losses to aquatic ecosystems involves implementation of costly measures, and reliable monitoring methods are therefore essential to select appropriate mitigation strategies and to evaluate their effects. Here, we compare the performances and costs of three methodologies for the monitoring of nutrients in rivers: grab sampling; time-proportional sampling; and passive sampling using flow-proportional samplers. Assuming hourly time-proportional sampling to be the best estimate of the "true" nutrient load, our results showed that the risk of obtaining wrong total nutrient load estimates by passive samplers is high despite similar costs as the time-proportional sampling. Our conclusion is that for passive samplers to provide a reliable monitoring alternative, further development is needed. Grab sampling was the cheapest of the three methods and was more precise and accurate than passive sampling. We conclude that although monitoring employing time-proportional sampling is costly, its reliability precludes unnecessarily high implementation expenses.

Accelerated removal of pyrene and benzo[a]pyrene in freshwater sediments with amendment of cyanobacteria-derived organic matter

The removal of pyrene and benzo[a]pyrene (BaP) were investigated in freshwater sediments with amendment of seven different organic matters including cyanobacteria-derived organic matter (COM), plant-derived organic matter (POM), and humic substances (HS). During the 210 days of experiments, the amendment of COM or HS enhanced significantly the removal of pyrene and BaP in sediments, especially with fresh COM (FCOM) treatment much superior to HS. On the contrary, degradation of these polycyclic aromatic hydrocarbons (PAHs) was not significantly improved and even inhibited in POM-amended sediments. The first-order rate constants of pyrene and BaP degradation in the FCOM-amended sediments reached 0.00540±0.00017d−1 and 0.00517±0.00057d−1, respectively, and were about three and five folds of those in the control treatment. The enhanced PAHs degradation in FCOM-amended sediments was related to higher PAH-degrading bacteria number and bioavailability with a result of biostimulation and priming effect by labile carbon and high-value nutrition in FCOM. Thus, this study improved our understanding about effects of settled biomass from cyanobacterial blooms, which occurred frequently in eutrophic aquatic ecosystems, on the natural attenuation of PAHs in sediments. Furthermore, this study would also help develop a new promising approach to remediate PAH-contaminated sediments through utilization of cyanobacterial bloom biomass.

Real-time estimation of TP load in a Mississippi Delta stream using a dynamic data driven application system

Elevated phosphorus (P) in surface waters can cause eutrophication of aquatic ecosystems and can impair water for drinking, industry, agriculture, and recreation. Currently, no effort has been devoted to estimating real-time variation and load of total P (TP) in surface waters due to the lack of suitable and/or cost-effective wireless sensors. However, when considering human health, drinking water supply, and rapidly developing events such as algal blooms, the availability of timely P information is very critical. In this study, we developed a new approach in the form of a dynamic data driven application system (DDDAS) for monitoring the real-time variation and load of TP in surface water. This DDDAS consisted of the following three major components: (1) a User Control that interacts with Schedule Run to implement the DDDAS with starting and ending times; (2) a Schedule Run that activates the Hydstra model; and (3) a Hydstra model that downloads the real-time data from a US Geological Survey (USGS) website that is updated every 15 min with data from USGS monitoring stations, predicts real-time variation and load of TP, graphs the variables in real-time on a computer screen, and sends email alerts when the TP exceeds a certain value. The DDDAS was applied to monitor real-time variation and load of TP for 30 days in Deer Creek, a stream located east of Leland, Mississippi, USA. Results showed that the TP concentrations in the stream ranged from 0.24 to 0.48 mg L−1 with an average of 0.30 mg L−1 for a 30-day monitoring period, whereas the cumulative load of TP from the stream was about 2.8 kg for the same monitoring period. Our study suggests that the DDDAS developed in this study was useful for estimating the real-time variation and load of TP in surface water ecosystems.

Periphyton response to nitrogen and phosphorus enrichment in a eutrophic shallow aquatic ecosystem

We examined changes in biomass and species dominance of periphyton in response to nitrogen (N) and phosphorus (P) enrichment in 12 mesocosms representing eutrophic aquatic ecosystems. The 100-L mesocosms consisted of lake water and pond sediment, and N and P were applied weekly. Periphyton samples were taken to assess the biomass (as estimated by the concentration of chlorophyll a (chl a)) and to determine which species were dominant. The mean periphyton biomass (chl a) in the P-enriched treatment did not differ from that in the control group, but increased with N enrichment. Compared with that in the control group, the chl a concentration increased with N+P enrichment in the early stages of the experiment, but decreased in the later stages. The decline in periphyton biomass at the later stages of the experiment was due to limited light availability, which resulted from the increased phytoplankton density in the experiment. The nutrient enrichment treatments resulted in changes in the dominant algal species in the periphyton, suggesting that various algal species showed different responses to different nutrients. The results of this study have implications for nutrient management in aquatic ecosystems.

Calcium nitrate addition to control the internal load of phosphorus from sediments of a tropical eutrophic reservoir: Microcosm experiments

The main objective of this study was to perform laboratory experiments on calcium nitrate addition to sediments of a tropical eutrophic urban reservoir (Ibirité reservoir, SE Brazil) to immobilize the reactive soluble phosphorus (RSP) and to evaluate possible geochemical changes and toxic effects caused by this treatment. Reductions of 75 and 89% in the concentration of RSP were observed in the water column and interstitial water, respectively, after 145 days of nitrate addition. The nitrate application increased the rate of autotrophic denitrification, causing a consumption of 98% of the added nitrate and oxidation of 99% of the acid volatile sulfide. As a consequence, there were increases in the sulfate and iron (II) concentrations in the sediment interstitial water and water column, as well as changes in the copper speciation in the sediments. Toxicity tests initially indicated that the high concentrations of nitrate and nitrite in the sediment interstitial water (up to 2300 mg L−1 and 260 mg L−1, respectively) were the major cause of mortality of Ceriodaphnia silvestrii and Chironomus xanthus. However, at the end of the experiment, the sediment toxicity was completely removed and a reduction in the 48 h-EC50 of the water was also observed. Based on these results we can say that calcium nitrate treatment proved to be a valuable tool in remediation of eutrophic aquatic ecosystems leading to conditions that can support a great diversity of organisms after a restoration period.

Rethinking the Role of Nitrogen and Phosphorus in the Eutrophication of Aquatic Ecosystems

For many years, environmental agencies have sought to improve the water quality of lakes and estuaries by reducing inputs of phosphorus. New research indicates that we must reduce both phosphorus and nitrogen to reverse eutrophication symptoms. This 3-page fact sheet was written by Karl Havens and Thomas Frazer, and published by the UF Department of Sea Grant, June 2012. SGEF190/SG118: Rethinking the Role of Nitrogen and Phosphorus in the Eutrophication of Aquatic Ecosystems (ufl.edu)

全球CO2水平升高对浮游植物生理和生态影响的研究进展

工业革命以来由于化石燃料的大量燃烧,大气CO₂水平不断增加,预计在21世纪末将增至现有水平的两倍,达到750 μL/L。作为全球初级生产力的重要贡献者,浮游植物应对CO₂水平升高的生理生态响应必然会对水生生态系统和碳、氮等元素的生物地球化学循环产生重要影响。全球CO₂水平的升高将显著改变水体的碳化学环境,淡水生态系统(湖泊和河流)由于容量小变化比海洋更为显著。水体碳化学环境的改变首先会影响浮游植物个体,在高CO₂水平下,浮游植物的细胞会有变小的趋势,并且细胞的光合作用强度也会有不同程度的增加,其中细胞较小或者不具有碳浓缩机制(CCM)的浮游植物增加较多,此外浮游植物细胞的化学元素计量值也将显著改变。随后浮游植物个体水平上的变化会进一步影响水生生态系统,例如水体初级生产力水平的提高,浮游植物、浮游动物群落结构组成以及水体微食物网结构的变化等。此外浮游植物对CO₂水平升高的生理生态响应程度还与水体的营养水平有关。总结了大气CO₂水平升高对浮游植物生理生态影响的研究方法,展望了未来可能的研究方向。;With the increase of global carbon emissions since the industrial revolution, atmospheric CO₂ level is expected to be twice higher than the present level at the end of this century, reaching to 750 μL/L. As atmospheric CO₂ is the most important source of soluble CO₂ in water due to the deliberate CO₂ sequestration, global CO₂ elevation would significantly alter carbonate chemical environments of aquatic ecosystems. When atmospheric CO₂ concentration doubles at the end of century, it is predicted that pH value of surface oceans would drop approximately 0.3 units, the concentration of bicarbonate ion would increase by 6%, and carbonate ion concentration would decrease by 50%. Considering the smaller buffering capacity of freshwater ecosystems than that of oceans, carbonate chemical environments of freshwater lakes and rivers may change more notably after the increase of CO₂ level. The shift of carbonate chemistry would in turn have dramatic effects on aquatic ecosystems. Phytoplankton has been used widely as an indicator of changes of aquatic ecosystems because this relatively short-lived organism responds rapidly to subtle changes. Meanwhile, it contributes approximately 50% of the total global primary productivity, which plays a vital role in global carbon cycling. Therefore, the physiological and ecological responses of phytoplankton to global CO₂ elevation would have great significance on water ecosystems and biogeochemical cycle. Elevated carbon resource could enhance the photosynthetic activity of phytoplankton, particularly small phytoplankton or non-CCM (non-carbon concentration mechanism) phytoplankton. When CO₂ level increases, the cell size of phytoplankton would potentially decrease, and the elemental ratio of carbon to nitrogen in phytoplankton cell would increase up to more than 10%. Then, those changes in the individual phytoplankton cell would cause certain variations in the ecological level. Primary productivity would rise significantly as a result of enhanced photosynthetic activity of phytoplankton. The shift in assemblage composition of phytoplankton, and the variation of elemental ratio could affect the edibility of phytoplankton, which would alter the abundances and the community structure of zooplankton. Furthermore, the accumulating concentration of organic carbon in water would promote the growth and reproduction of heterotrophic bacterioplankton, which would strengthen the competition between bacterioplankton and phytoplankton for nutrients, such as nitrogen and phosphorus. More importantly, elevated CO₂ effects differ between oligotrophic and eutrophic water body. It is expected that effects on algal productivity in eutrophic aquatic ecosystems could be potentially larger, since in eutrophic water the input of nitrogen and phosphorus to the global biochemical cycle exceeds that of the carbon input by several orders of magnitude. Finally, we summarized the development of the methodology for studying the effect of enhanced CO₂ level on water ecosystems. Long-term in situ simulating experiment would be the best approach for studying the effect of enhanced CO₂ on natural phytoplankton community. In future research, picophytoplankton will attract more attention, since they are sensitive to the change of CO₂ level compared with large ones because of their high surface-area-to-volume ratio. In addition, more efforts should be exerted for freshwater ecosystems with respect to elevated CO₂ effects, as they are far less investigated than marine ecosystems even though they are closely linked to the survival of human being.