Phytoplankton Phosphorus Research Articles

Atmospheric deposition and river runoff stimulate the utilization of dissolved organic phosphorus in coastal seas

In coastal seas, the role of atmospheric deposition and river runoff in dissolved organic phosphorus (DOP) utilization is not well understood. Here, we address this knowledge gap by combining microcosm experiments with a global approach considering the relationship between the activity of alkaline phosphatases and changes in phytoplankton biomass in relation to the concentration of dissolved inorganic phosphorus (DIP). Our results suggest that the addition of aerosols and riverine water stimulate the biological utilization of DOP in coastal seas primarily by depleting DIP due to increasing nitrogen concentrations, which enhances phytoplankton growth. This “Anthropogenic Nitrogen Pump” was therefore identified to make DOP an important source of phosphorus for phytoplankton in coastal seas but only when the ratio of chlorophyll a to DIP [Log10 (Chl a / DIP)] is larger than 1.20. Our study therefore suggests that anthropogenic nitrogen input might contribute to the phosphorus cycle in coastal seas.

Significance of phosphate adsorbed on the cellular surface as a storage pool and its regulation in marine microalgae

The increasing prevalence of phosphorus limitation in coastal waters has drawn attention to the bioavailability of cellular surface-adsorbed phosphorus (SP) as a reservoir of phosphorus in phytoplankton. This study examined the storage, utilization, and regulation of SP in the coastal waters of the East China Sea, as well as three cultivated algal bloom species (Skeletonema marinoi, Prorocentrum shikokuense, and Karenia mikimotoi) prevalent in the area. SP accounted for 14.3%–45.5% of particulate phosphorus in the field and laboratory species. After the depletion of external phosphate, the studied species can rapidly transport SP within 3–24 h. The storage of SP is regulated by both external phosphate conditions and the internal growth stage of cells, but it is not influenced by the various cellular surface structures of the studied species. This study highlights the significance of SP as a crucial phosphorus reservoir and the potential use of the SP level as an indicator of phosphorus deficiency in phytoplankton.

Photolysis characteristics and influencing factors of adenosine 5′-monophosphate in seawater

Environmental context Organophosphorus (OP) is bioavailable to phytoplankton with photolysis can play an important role in the process. The photolysis behaviour of an OP (adenosine 5′-monophosphate, AMP) in seawater was investigated, and AMP can release inorganic phosphate under environmentally relevant light conditions, indicating OP photodegradation might be important in the phosphorus biogeochemical cycle. The results are helpful to further understand the bioavailability and cycle of OP in marine environment. Rationale Organic phosphorus (OP) is a potential source of bioavailable phosphorus for phytoplankton through photolysis and other degradation processes. Therefore, OP photodegradation plays an important role in phosphorus biogeochemical cycle. Methodology Taking adenosine 5′-monophosphate (AMP) as a model OP, we investigated the photolysis behaviour in seawater and discussed the mechanism. The photolysis dynamics were studied based on the inorganic phosphorus production at appropriate time intervals, which was analysed by spectrophotometric molybdenum blue method. The effects of medium, light and radicals were investigated. Results It was found that AMP can release inorganic phosphate under photosynthetically active radiation and ultraviolet (UV) with UVB being the most reactive band. The degradation of AMP in seawater was lower than that in deionised water under the same conditions, and the fresh seawater was more beneficial than aged seawater. The kinetics could be described by a pseudo-first order equation. Fe3+ can promote the photolysis due to the generation of ·OH radicals, while within the range of this study, changes of Fe3+ content have no substantial effect on the promotion. The influence of ethanol and tetrahydrofuran as radical inhibitor showed evident inhabitation to the degradation, indicating that ·OH and 1O2 played an important role in the process, and ·OH seemed more important than 1O2. Discussion OP photodegradation is of importance in the phosphorus biogeochemical cycle. Varying properties of the medium and light can affect the OP transformation in seawater. The results are helpful to further understand the bioavailability and cycle of OP in the marine environment.

Total nitrogen and community turnover determine phosphorus use efficiency of phytoplankton along nutrient gradients in plateau lakes

Numerous studies support that biodiversity predict most to ecosystem functioning, but whether other factors display a more significant direct impact on ecosystem functioning than biodiversity remains to be studied. We investigated 398 samples of the phytoplankton phosphorus resource use efficiency (RUEP = chlorophyll-a concentration/dissolved phosphate) across two seasons in nine plateau lakes in Yunnan Province, China. We identified the main contributors to phytoplankton RUEP and analyzed their potential influences on RUEP at different lake trophic states. The results showed that total nitrogen (TN) contributed the most to RUEP among the nine lakes, whereas community turnover (measured as community dissimilarity) explained the most to RUEP variation across the two seasons. Moreover, TN also influenced RUEP by affecting biodiversity. Species richness (SR), functional attribute diversity (FAD2), and dendrogram-based functional diversity (FDc) were positively correlated with RUEP in both seasons, while evenness was negatively correlated with RUEP at the end of the rainy season. We also found that the effects of biodiversity and turnover on RUEP depended on the lake trophic states. SR and FAD2 were positively correlated with RUEP in all three trophic states. Evenness showed a negative correlation with RUEP at the eutrophic and oligotrophic levels, but a positive correlation at the mesotrophic level. Turnover had a negative influence on RUEP at the eutrophic level, but a positive influence at the mesotrophic and oligotrophic levels. Overall, our results suggested that multiple factors and nutrient states need to be considered when the ecosystem functioning predictors and the biodiversity-ecosystem functioning relationships are investigated.

Reversing impact of phytoplankton phosphorus limitation on coastal hypoxia due to interacting changes in surface production and shoreward bottom oxygen influx

Phosphorus (P) limitation of phytoplankton growth is increasingly common in estuarine and coastal waters due to rising anthropogenic nitrogen input faster than that of phosphorus. However, the impact of P limitation on coastal hypoxia remains inconclusive and is challenging to observe. By combining observations with results from a three-dimensional physical-biogeochemical model off the Pearl River Estuary, we illustrate that during the summer upwelling period, the impact of P limitation reverses from suppressing hypoxia to amplifying hypoxia as P-limitation severity decreases. When P limitation is severe in the ecosystem (i.e., P limitation extensively covers the stratified waters where hypoxia tends to develop), the surface primary production and the coupled bottom oxygen consumption are diluted along the upstream-downstream axis because of the P limitation. In addition, the increased downstream bottom oxygen level enhances the shoreward bottom oxygen influx. These effects, together, reduce coastal hypoxia. In contrast, when P-limitation severity is low (i.e., P limitation is spatially constrained), the downstream relocated surface production reduces upstream hypoxia but increases downstream hypoxia, which subsequently weakens the shoreward bottom oxygen influx and hence lowers its capacity to relieve upstream hypoxia. The net effect can amplify the coastal hypoxic extent. Our results emphasize how different P-limitation severity can reverse its impact on coastal hypoxia due to the interacting changes in surface production and bottom oxygen influx. We propose the potential of using the spatial extent of P limitation as a proxy to predict its impact on coastal hypoxia and support ecosystem nutrient management.

Seasonal dynamics of phytoplankton phosphorus stress in temperate Jiaozhou Bay, North China

Alkaline phosphatase activity (APA) is always used to evaluate the phosphorus (P) status of phytoplankton community and considered as a proxy for phosphate (DIP) stress or deficiency. In this study, we presented seasonal distributions of APA [including free APA (F-APA) and particulate APA (P-APA)] and enzyme kinetics and compared to the distribution of phosphorus concentrations, planktonic biomass and other environmental variables reflecting community P status in moderate DIP-deficient Jiaozhou Bay, North China. Low potential APA (Vmax) were detected in winter (mean 51.3 nM h-1), which was probably due to low water temperature, while higher APA corresponded well to high phosphate requirement and high biological productivity in other three seasons. Normalized total APA (specified by chlorophyll a and bacteria biomass) showed an inverse hyperbolic relationship with DIP and the threshold phosphate concentration for the transition from high to low APA was around 0.2 μM in Jiaozhou Bay. Combined with results of APA, P concentrations (including DIP and DOP) and half saturation constant (Km), our findings suggested that phytoplankton and bacteria in Jiaozhou Bay may be experiencing a relief from P-limitation in winter; while in other three seasons, these organisms were mainly under persistent P stress. Moreover, in order to compensate for phosphate deficiency, we hypothesize that plankton not only by means of promoting enzyme production as indicated by increase of Vmax, but also by an improved enzyme affinity as represented by a decrease of the Michaelis constant (Km). Consequently, higher APA and lower DOP stocks in summer were probably a result of greater utilization of the DOP pool to maintain high primary production.

Dredging project caused short-term positive effects on lake ecosystem health: A five-year follow-up study at the integrated lake ecosystem level

Sediment dredging is a controversial technology for lake eutrophication control. A lengthy and holistic assessment is important to understand the effects of a dredging project on a lake ecosystem. In this study, a dredging project was followed for 5 years. To understand the variations of lake ecosystems before, during and after the project, water quality, phytoplankton, zooplankton and benthic animal biomass were monitored; Four subindicators, including eco-exergy (Ex), structural eco-exergy (Exst), buffer capacity of total phosphorus for phytoplankton (β(TP)(phyto)) and trophic level index (TLI) were calculated and developed to an integrated ecosystem health indicator (EHI). The monitoring results showed that the dredging project caused many short-term positive effects such as decreased total nitrogen, total phosphorus, permanganate index and phytoplankton biomass throughout the entire lake water, increased Secchi disk depth in the whole lake and increased benthonic animal biomass in the nondredged regions. However, these positive effects disappeared overtime. Water chemistry and biomass returned to the initial state before dredging. EHI showed that the dredging project caused negative effects on the lake health in the dredged region at first. Subsequently, the health status of the entire lake, including the dredged and nondredged regions, improved until 1–2 years after the project finished. Because of the lack of other timely ecological restoration measures, the lake gradually returned to its initial health status. However, the health status in the dredged regions was only slightly better than before dredging and often worse than that of the nondredged regions. Our study suggested that dredging projects may only cause short-term positive effects on lake ecosystem health. The external interception and dredging ratio were important. A dredging project should be combined with other ecological lake restoration measures when the project has caused positive effects in a lake.

Spatial distributions of external and internal phosphorus loads in Lake Erie and their impacts on phytoplankton and water quality

Re-eutrophication in Lake Erie has led to new programs to reduce external phosphorus loads, and it is important to understand the interrelated dynamics of external and internal phosphorus loads. In addition to developing phosphorus load response curves for algal biomass in the western basin and hypoxia in the central basin, we used a two-dimensional (vertical-longitudinal) hydrodynamic and ecological model to show that both external and internal phosphorus loads were distributed homogeneously in the water column in Lake Erie's western basin. In the stratified central and eastern basins phosphorus released by organic matter decay and crustacean zooplankton excretion was concentrated in the upper water column, contributing 100–119% of the phytoplankton phosphorus demand, while phosphorus released by dreissenids and from anoxic sediments was distributed primarily in the hypolimnion during the growing season. Simulated reductions in external phosphorus loads decreased individual phytoplankton groups most at times when they were normally most abundant, e.g., Microcystis decreased the most during September. Phosphorus was limiting over the simulation periods, but water temperature and light conditions also played critical roles in phytoplankton succession. While water column phosphorus responded quickly to external phosphorus reduction, pulses of phosphorus (riverine input or sediment resuspension) occurring immediately before the Microcystis bloom period could allow it to bloom despite long-term external phosphorus load reduction. Studies are warranted to assess the contribution of seasonal dynamics in phosphorus loading (including sediment resuspension) to Microcystis bloom development.

Virus production in phosphorus-limited Micromonas pusilla stimulated by a supply of naturally low concentrations of different phosphorus sources, far into the lytic cycle.

Earlier studies show that the proliferation of phytoplankton viruses can be inhibited by depletion of soluble reactive phosphorus (SRP; orthophosphate). In natural marine waters, phytoplankton phosphorus (P) availability is, however, largely determined by the supply rate of SRP (e.g. through remineralization) and potentially by the source of P as well (i.e. the utilization of soluble non-reactive P; SNP). Here we show how a steady low supply of P (mimicking natural P recycling) to virally infected P-limited Micromonas pusilla stimulates virus proliferation. Independent of the degree of P limitation prior to infection (0.32 and 0.97μmax chemostat cultures), SRP supply resulted in 2-fold higher viral burst sizes (viruses lysed per host cell) as compared with no addition (P starvation). Delaying these spikes during the infection cycle showed that the added SRP was utilized for extra M. pusilla virus (MpV) production far into the lytic cycle (18 h post-infection). Moreover, P-limited M. pusilla utilized several SNP compounds with high efficiency and with the same extent of burst size stimulation as for SRP. Finally, addition of virus-free MpV lysate (representing a complex SNP mixture) to newly infected cells enhanced MpV production, implicating host-associated alkaline phosphatase activity, and highlighting its important role in oligotrophic environments.

Regime shift in a phytoplankton–phosphorus model with vertical structure and seasonality

Many ecological systems are influenced by positive feedbacks between organisms and abiotic environments, which generates multiple stable equilibria of a mathematical model with a hysteresis structure. In addition, discontinuous shifts of system at equilibrium is predicted, which is often called regime shift in ecosystem sciences. This hysteresis structure is unfavorable from environmental management point of view, because the reconstruction of original equilibrium state requests much lower levels of external forcing. Mathematical models proposed in previous works are simple and mathematically tractable ([7],[2]).However, it is difficult to extrapolate from such simple models the occurrence likelihood of regime shift in natural environments since temporally dynamic features in ecology and physico-chemical environments, and spatial dimension are less explored in those models. In this study, we construct a realistic but mathematically tractable model of interaction between phytoplankton and phosphorus, which incorporates (1) 1-dimensional vertical structure of lake ecosystem and (2) seasonal periodic cycle of water mixing. We aim to understand the impact of changes in seasonality in various types of lakes on the occurrence of multiple attractors (periodic solution) and hysteresis structure.

Using eutrophication and ecological indicators to assess ecosystem condition in Poyang Lake, a Yangtze-connected lake

Poyang Lake, the largest freshwater lake in China, has been facing shrinkage and environmental problems in recent years, making it imperative to assess the status of its ecosystem. In this study, such an assessment was conducted based on the trophic status index, phytoplankton biomass, the ratio of zooplankton biomass to phytoplankton biomass, eco-exergy, structural eco-exergy, and ecological buffer capacity to total phosphorus for phytoplankton. First, the spatial and temporal variations of the ecosystem status in Poyang Lake were assessed based on these six indicators. Then, cluster analysis was utilized to classify the 15 sites based on the various indicators and to identify the most influential indicators. The results showed that the ecological status of Poyang Lake was affected not only by eutrophication but also by hydrological characteristics. All of the 15 sites had deteriorated to a certain degree. An analysis of the relative spatial ecological status showed that the status of the water in the rivers was superior to the status of water in the central lake. Furthermore, the relative ecological status was found to be best in summer and second best in autumn with ecological status deteriorating in winter. There was no significant correlation between eco-exergy and trophic status index, but a very strong relationship was found between eco-exergy and macrozoobenthos biomass with an R2 of 0.92, indicating that macrozoobenthos contributed greatly to the eco-exergy.

Seasonal variations of phytoplankton phosphorus stress in the Yellow Sea Cold Water Mass

The Yellow Sea is located between the China Mainland and the Korean Peninsula, representing a typical shallow epicontinental sea. The Yellow Sea Cold Water Mass (YSCWM) is one of the most important physical features in the Yellow Sea. The characteristics of vertical profiles and seasonal variations of biogenic elements in the YSCWM may lead the variations of nutrient availability (e.g., phosphorus) and phosphorus stress of phytoplankton. In this study, the authors surveyed the seasonal variations of phytoplankton phosphorus stress with emphasis on the effect of the YSCWM during the four cruises in April and October 2006, March and August 2007. Using both bulk and single-cell alkaline phosphatase activity (APA) assays, this study evaluated phosphorus status of phytoplankton community, succession of phytoplankton community and ecophysiological responses of phytoplankton to phosphorus in the typical region of the YSCWM. With the occurrence of the YSCWM, especially the variations of concentration of dissolved inorganic phosphorus (DIP), the results of bulk APA appeared corresponding seasonal variations. Along Transects A and B, the mean APA in August was the highest, and that in March was the lowest. According to the ELF-labeled assay’s results, seasonal variations of the ELF-labeled percentages within dominant species indicated that diatoms were dominant in March, April and October, while dinoflagellates were dominant in August. During the four cruises, the ELF-labeled percentages of diatoms except Paralia sulcata showed that diatoms were not phosphorus deficient in April 2006 at all, but suffered from severe phosphorus stress in August 2007. In comparison, the ELF-labeled percentages of dinoflagellates were all above 50% during the four time series, which meant dinoflagellates such as Alexandrium and Scrippsiella, sustained perennial phosphorus stress.

Primary production and phosphorus modelling in LakeVegoritis, Greece

Primary production and phosphorus are two of the most important determinants of the water quality of lakes. Phytoplankton primary production and phosphorus cycling were modelled within a one-dimensional lake water quality model. The model was calibrated and applied to Lake Vegoritis in Greece for two different years (1981 and 1993) using daily meteorological variables and inflow rates as input data. Monthly profiles of temperature, chlorophyll-a, and oxygen concentration for these two years were used to calibrate the model. Simulation results indicate that the thermal regime of the lake strongly affects phosphorus profiles and that phytoplankton concentrations throughout the year are tightly correlated with soluble reactive phosphorus concentrations. The significant decrease in the depth and the volume of the lake from 1981 to 1993 resulted in important changes in phytoplankton and phosphorus concentrations. A sensitivity analysis was conducted to estimate the errors resulting from the uncertainty in the biochemical variables of the model and the limited data on phosphorus and phytoplankton.

Effect of intensive epilimnetic withdrawal on phytoplankton community in a (sub)tropical deep reservoir

Withdrawal is an important process in reservoir hydrodynamics, removing phytoplankton with flushed water. Zooplankton ， the grazers of phytoplankton, having longer generation times, are even more susceptible than phytoplankton to flushing loss. Therefore phytoplankton are affected not only by abiotic conditions linked to hydrodynamics but also by zooplankton due to weakened grazing pressure. During the Asian Games (November 12-27, 2010 in Guangzhou, China), two intensive epilimnetic withdrawals were conducted in Liuxihe, a deep canyon-shaped reservoir . To examine the influence of the intensive epilimnetic withdrawals on the phytoplankton community, a seven-week field observation and a hydrodynamic simulation were carried out. The observation was divided in two stages: stage 1 represented partial surface vertical mixing period, and stage 2 represented intensive epilimnetic withdrawal period. It was found that phytoplankton abundance and biomass declined with water temperature and partial surface vertical mixing in stage 1. However, the intensive epilimnetic withdrawal reversed this decreasing trend and increased phytoplankton biomass and abundance in stage 2. Phytoplankton showed a higher rate of composition change in stage 2. A numerical model ( DYRESM-CAEDYM ) simulated scenarios with and without epilimnetic withdrawal to test their effects on abiotic factors ( water temperature, suspended sediment and soluble reactive phosphorus ) for phytoplankton. The results showed no obvious difference in the abiotic factors between the two scenarios during stage 2. We therefore suggested that the abiotic factors in the water column were probably driven by a seasonal pattern, not by epilimnetic withdrawal. It is likely that the intensive epilimnetic withdrawal could remove large crustaceans. The reduced grazing pressure probably explained the increase of phytoplankton biomass and abundance after the withdrawal. Thus, we suggest that reservoir operation should pay more attention to grazing from large crustaceans. It is recommended that, in the management of reservoirs, intensive epilimnetic withdrawal during autumn should be avoided in order to control excessive phytoplankton in the tropics and subtropics.

Phytoplankton phosphorus limitation in a North Atlantic coastal ecosystem not predicted by nutrient load

Phytoplankton nutrient limitation patterns were investigated in an anthropogenically influenced coastal ecosystem with a high nutrient load. Weekly nutrient limitation bioassays, and water chemistry and stoichiometry measurements were performed in the Bay of Brest, France, from February to July 2011. Each limitation bioassay included phosphorus, nitrogen, silicate and all possible combined nutrient additions, and lasted over 72 h. Results showed that the phytoplankton community experienced a general P limitation from March to July. N limitation alone was observed only during 1 week in early March. Subsequently, all limitation bioassays revealed primary P limitation, indicated by significantly increased growth rates in all samples containing P additions. Besides P, Si was the second limiting nutrient for phytoplankton during 2 weeks at end of May to mid-June. Seston C:P ratios ranged between 198:1 and 749:1, and N:P ratios between 28:1 and 104:1. The highest effects on phytoplankton growth were reached with NPSi addition, suggesting synergistic macronutrient effects under single nutrient limitation. Our results demonstrate that dissolved nutrient ratios are not reliable in predicting actual phytoplankton nutrient limitation, since other processes and organisms strongly influence nutrient availability and resupply. The dominant P limitation emphasizes its importance for consideration in coastal water management.

Nitrogen and phosphorus phytoplankton growth limitation in the northern Gulf of Mexico

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 68:159-169 (2013) - DOI: https://doi.org/10.3354/ame01607 Nitrogen and phosphorus phytoplankton growth limitation in the northern Gulf of Mexico R. Eugene Turner1,*, Nancy N. Rabalais2 1Coastal Ecology Institute and Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, USA 2Louisiana Universities Marine Consortium, 8124 Highway 56, Chauvin, Louisiana 70344, USA *Email: euturne@lsu.edu ABSTRACT: We conducted 158 bioassays to determine phytoplankton growth limitation in the northern Gulf of Mexico and made the following observations. Light limitation occurred where salinity was <20; at higher salinities, phytoplankton biomass yield became mostly limited by N or by a co-limitation of N plus P (NP). The number of N-limited bioassays was 5 times greater than the P-limited bioassays. NP synergism occurred where salinity was >20, and represented 59% of all samples that were not light-limited. The interaction of N and P co-limitation was frequently synergistically additive, i.e. the combined effects of N and P limitation together created a greater response than the sum of either separately. The dissolved inorganic nitrogen:phosphate ratio (DIN:Pi) and various concentrations of DIN and Pi did not offer reliable chemical boundaries describing likely areas of exclusive N or P limitation in these bioassays. We conclude that reducing N loading to the shelf is a prudent management action that will partially remediate eutrophic conditions, including those that lead to hypoxia, but the omission of a concurrent reduction in P loading would be shortsighted. KEY WORDS: Nutrient limitation · Algal community · Eutrophication · Hypoxia · N:P ratios · Mississippi River Full text in pdf format PreviousNextCite this article as: Turner RE, Rabalais NN (2013) Nitrogen and phosphorus phytoplankton growth limitation in the northern Gulf of Mexico. Aquat Microb Ecol 68:159-169. https://doi.org/10.3354/ame01607 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 68, No. 2. Online publication date: March 01, 2013 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2013 Inter-Research.

白洋淀生态系统健康评价

PDF HTML阅读 XML下载 导出引用 引用提醒 白洋淀生态系统健康评价 DOI: 10.5846/stxb201207050937 作者: 作者单位: 北京师范大学环境学院,北京师范大学环境学院,北京师范大学环境学院,北京师范大学环境学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金创新研究群体科学基金资助项目（51121003）；国家水体污染控制与治理科技重大专项资助项目（2008ZX07209-009）；国家自然科学基金资助项目（51279009） Ecosystem health assessment in Baiyangdian Lake Author: Affiliation: State Key Laboratory of Water Environment Simulation,School of Environment,Beijing Normal University,State Key Laboratory of Water Environment Simulation,School of Environment,Beijing Normal University,State Key Laboratory of Water Environment Simulation,School of Environment,Beijing Normal University,State Key Laboratory of Water Environment Simulation,School of Environment,Beijing Normal University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:涵盖热力学指标的指标体系可全面表征湖泊生态系统在受扰条件下的健康状态。在实地监测的基础上，应用浮游植物生物量（BA）、浮游动物生物量/浮游植物生物量（BZ/BA）浮游植物群落初级生产量（P）、能质（Ex）、结构能质（Exst）和浮游植物对TP的缓冲能力（βp）表征白洋淀的健康状态，并通过集成健康综合指数，确定了白洋淀14个水域的健康等级。结果表明，白洋淀大部分水域健康受损较为严重。枣林庄和采蒲台水域处于亚健康状态，烧车淀、光淀张庄和东田庄水域处于不健康状态，其余9个水域均处于病态。结合各水域人类干扰活动的分布可知，白洋淀健康退化的程度与人类干扰强度密切相关。府河和淀内居民生活及水产养殖污水排放是造成白洋淀健康受损的主要原因。该结果可为白洋淀生态系统的管理和修复提供一定的科学依据。 Abstract:Index system covering thermodynamic indicators specialized by eco-exergy and structural eco-exergy could comprehensively characterize the ecological health condition of lake ecosystems under human disturbances. This system has been widely used for assessing lake ecosystem health in recent decades. For comparing ecological health of one lake across time scale or that of different lakes, integration of comprehensive health index is needed to identify the degree of lake health and to better reflect the discrepancies of the ecological health conditions. In this paper, an integrated index system including indicators of phytoplankton biomass (BA), ratio of zooplankton to phytoplankton biomass (BZ/BA), phytoplankton primary production (P), eco-exergy (Ex), structural eco-exergy (Exst) and ecological buffer capacity to total phosphorus for phytoplankton (βp) collected from field survey was structured to assess the ecological health condition of Baiyangdian Lake which is located in North China. Health classes of fourteen water areas in Baiyangdian Lake were identified using comprehensive health index, which was computed through the sum of normalized indices multiplied by the weights. The results indicate that the ecological health of most water areas in Baiyangdian Lake is deteriorated severely. The water areas of Zaolinzhuang and Caiputai are sub-healthy, those of Shaochedian, GuangdianZhangzhuang and Dongtianzhuang are less healthy, and those of the remaining nine are unhealthy. The spatial variations of ecological health condition of the all water areas across Baiyangdian Lake are notable. The water areas in the northeast and southeast are under relatively better ecological health conditions. The ecological health conditions in the northern, central and southern water areas are deteriorated to some extent while those in the western water area, which is close to Fu River, the ecological health conditions are seriously degraded. The ecological health conditions from good to bad in spatial scale are in the following order: water areas in the northeast and southeast > water areas in the north, center and south > water areas in the west. There is close relationship between intensity of human disturbances and extent of lake health degradation. The water areas in the northeast and southeast with little human disturbances can maintain relatively natural state of the lake ecosystem with good health conditions. The dense non-point source pollution associated with aquaculture and villages is the key factor which leads to the ecological health deterioration in the northern, central and southern water areas. The western water areas have been greatly affected greatly by large amounts of pollutants from Fu River, leading to relatively worse ecological health condition. It can be seen that sewages discharged from the villages and aquaculture into the reservoir are the dominant factors resulting in ecological health degradation in Baiyangdian Lake. In comparison with the pollutants from the aquaculture and villages, there are more impacts of pollutants discharged from Fu River on the ecological health condition of Baiyangdian Lake. The results in the paper could offer foundation for further study of early warning and control of lake ecosystem health. In addition, they can provide scientific evidence for ecosystem restoration and management of Baiyangdian Lake. 参考文献 相似文献 引证文献

Examination of the role of detritus food quality, phytoplankton intracellular storage capacity, and zooplankton stoichiometry on planktonic dynamics

Nutrient stoichiometric ratios are primary driving factors of planktonic food web dynamics. Ecological stoichiometry theory postulates the elemental ratios of consumer species to be homeostatic, while primary-producer stoichiometry may vary with ambient nutrient availability. The notion of phytoplankton intracellular storage is far from novel, but remains largely unexplored in modeling studies of population dynamics. We constructed a seasonally-unforced, zero-dimensional, nutrient–phytoplankton–zooplankton–detritus (NPZD) model that considers dynamic phytoplankton phosphorus reserves and quasi-dynamic zooplankton stoichiometry. A generic food quality term is used to express seston biochemical composition, ingestibility, and digestibility. We examined the sensitivity of the planktonic food web patterns to light and nutrient availability, zooplankton mortality, and detritus food quality as well as to phytoplankton intracellular storage and zooplankton stoichiometry. Our results reinforce earlier findings that high quality seston exerts a stabilizing effect on food web dynamics. However, we also found that the combination of low algal and high detritus food quality with high zooplankton mortality yielded limit cycles and multiple steady states, suggesting that the heterogeneity characterizing seston nutritional quality may have more complicated ecological ramifications. Our numerical experiments identify resource competition strategies related to nutrient transport rates and internal nutrient quotas that may be beneficial for phytoplankton to persevere in resource-limiting habitats. We also highlight the importance of the interplay between optimal stoichiometry and the factors controlling homeostatic rigidity in zooplankton. In particular, our predictions show that the predominance of phosphorus-rich and tightly-homeostatic herbivores in nutrient-enriched environments with low seston food quality can potentially result in high phytoplankton abundance, high phytoplankton-to-zooplankton ratios, and acceleration of oscillatory dynamics. Generally, our modeling study emphasizes the impact of both intracellular/somatic storage and food quality on prey–predator interactions, pinpointing an important aspect of food web dynamics usually neglected by the contemporary modeling studies.

Alkaline phosphatase gene sequence characteristics and transcriptional regulation by phosphate limitation in Karenia brevis (Dinophyceae)

The toxic dinoflagellate Karenia brevis Davis forms harmful algal blooms and has caused devastating consequences in the Gulf of Mexico in the past decades. While phosphorus nutrient is believed to play an important role in the bloom formation, the molecular mechanism is still poorly understood. In this study, we explored alkaline phosphatase (AP) in K. brevis, an enzyme known to facilitate the utilization of dissolved organic phosphorus (DOP) in other phytoplankton when the dissolved inorganic phosphorus (DIP) is limited in the environment. We isolated the full-length cDNAs of AP gene (kbrap) from this species and characterized its expression pattern under contrasting DIP conditions. Analysis of the deduced amino acid sequence revealed that K. brevis AP is a membrane-associated protein, consistent with the predominant cell surface localization of the AP activity detected by enzyme labeled fluorescence labeling. Phylogenetic analyses indicate that kbrap is closest to the homolog from another toxic dinoflagellate, Amphidinium carterae, at both the nucleotide and amino acid levels. The two dinoflagellate APs share similarity in the key domains with diatom APs, and are phylogenetically more closely related to counterparts from diatoms than those from green algae and bacteria. When K. brevis cells were cultured in a DIP-limited medium, the AP activity increased markedly (5–6-fold higher than the initial values), following a slight and brief increase in kbrap expression level, while the cell concentrations in the cultures decreased significantly. The AP enzyme activity and kbrap transcription level were repressed when DIP was resupplied to the DIP-limited cultures. Our results suggest that AP enables K. brevis to grow in DIP-limited and DOP-rich environments, but its mode of response is different from that in A. carterae.

Plasticity of Total and Intracellular Phosphorus Quotas in Microcystis aeruginosa Cultures and Lake Erie Algal Assemblages

Blooms of the potentially toxic cyanobacterium Microcystis are common events globally, and as a result significant resources continue to be dedicated to monitoring and controlling these events. Recent studies have shown that a significant proportion of total cell-associated phosphorus (P) in marine phytoplankton can be surface adsorbed; as a result studies completed to date do not accurately report the P demands of these organisms. In this study we measure the total cell-associated and intracellular P as well as growth rates of two toxic strains of Microcystis aeruginosa Kütz grown under a range of P concentrations. The results show that the intracellular P pool in Microcystis represents a percentage of total cell-associated P (50–90%) similar to what has been reported for actively growing algae in marine systems. Intracellular P concentrations (39–147 fg cell−1) generally increased with increasing P concentrations in the growth medium, but growth rate and the ratio of total cell-associated to intracellular P remained generally stable. Intracellular P quotas and growth rates in cells grown under the different P treatments illustrate the ability of this organism to successfully respond to changes in ambient P loads, and thus have implications for ecosystem scale productivity models employing P concentrations to predict algal bloom events.