TN : TP ratio and planktivorous fish do not affect nutrient-chlorophyll relationships in shallow lakes

1. In previous work, phytoplankton regulation in freshwater lakes has been associated with many factors. Among these, the ratio of total nitrogen to total phosphorus (TN : TP) has been widely proposed as an index to identify whether phytoplankton are N- or P-limited. From another point of view, it has been suggested that planktivorous fish can be used to control phytoplankton. 2. Large-scale investigations of phytoplankton biomass [measured as chlorophyll a, (chl-a)] were carried out in 45 mid-lower Yangtze shallow lakes to test hypotheses concerning nutrient limitation (assessed with TN : TP ratios) and phytoplankton control by planktivorous fish. 3. Regression analyses indicated that TP was the primary regulating factor and TN the second regulating factor for both annual and summer phytoplankton chl-a. In separate nutrient-chl-a regression analyses for lakes of different TN : TP ratios, TP was also superior to TN in predicting chl-a at all particular TN : TP ranges and over the entire TN : TP spectrum. Further analyses found that chl-a : TP was not influenced by TN : TP, while chl-a : TN was positively and highly correlated to TP : TN. 4. Based on these results, and others in the literature, we argue that the TN : TP ratio is inappropriate as an index to identify limiting nutrients. It is almost impossible to specify a 'cut-off' TN : TP ratio to identify a limiting nutrient for a multi-species community because optimal N : P ratios vary greatly among phytoplankton species. 5. Lakes with yields of planktivorous fish (silver and bighead carp, the species native to China) > 100 kg ha(-1) had significantly higher chl-a and lower Secchi depth than those with yields < 100 kg ha(-1). TP-chl-a and TP-Secchi depth relationships are not significantly different between lakes with yields > 100 kg ha(-1) or < 100 kg ha(-1). These results indicate that the fish failed to decrease chl-a yield or enhance Z(SD). Therefore, silver carp and bighead carp are not recommended as a biotic agent for phytoplankton control in lake management if the goal is to control the entire phytoplankton and to enhance water quality.

The low TN : TP ratio, a cause or a result of Microcystis blooms?

An enclosure experiment in the shallow, subtropical Lake Donghu, China, was performed in the summer of 2001 to examine the effect of TN:TP (total phosphorus) ratios and P-reduction on the occurrence of Microcysitis blooms. The treatments were performed with enough amounts of N but with different amounts of P in the water column and sediment. Microcystis blooms occurred in the enclosures either with an initial TN:TP <29 or TN:TP >29 where the nutrients (N, P) were high enough. Microcysitis blooms never occurred in the treatments with low P concentration in spite of the presence of sufficient N. The P-rich sediments served as an important source for the P supply in the water column, and such a process was activated greatly by the outburst of Microcystis blooms which pumped up selectively P from the sediments and thus decreased the TN:TP ratios. Therefore, the low TN:TP ratio is not a cause but rather a result of Microcystis blooms. (C) 2002 Elsevier Science Ltd. All rights reserved.

长江中下游地区浅水湖泊群中无机氮和TN/TP变化的模式及生物调控机制

对长江中下游地区33个浅水性湖泊的氨态氮(NH_3-N)、硝态氮(NO_3-N)、亚硝氮(NO_2-N)和氮磷比(TN/TP)在生长季节和非生长季节的变化进行了研究。各营养盐浓度之间均呈显著正相关,整体上生长季节的相关性较好。当TP＞0．1 mgL~(-1)时,随TP浓度的升高,非生长季节氨态氮浓度增加较快,硝态氮在生长季节呈增长趋势而在非生长季节有下降的趋势,这主要因为非生长季节超富营养湖泊中的溶氧和温度较生长季节低,而硝化作用对溶氧和温度较敏感所致。当TP为0．035 mg·l~(-1)～0．1 mg

Changes in the patterns of inorganic nitrogen and TN/TP ratio and the associated mechanism of biological regulation in the shallow lakes of the middle and lower reaches of the Yangtze River

The changes of NH3-N, NO3-N, NO2-N and TN/TP were studied during growth and non-growth season in 33 subtropical shallow lakes in the middle and lower reaches of the Yangtze River. There were significant positive correlations among all nutrient concentrations, and the correlations were better in growth season than in non-growth season. When TP > 0.1 mgL(-1), NH3-N increased sharply in non-growth season with increasing TP, and NO3-N increased in growth season but decreased in non-growth season with TP. These might be attributed to lower dissolved oxygen and low temperature in non-growth season of the hypereutrophic lakes, since nitrification is more sensitive to dissolved oxygen and temperature than anti nitrification. When 0.1 mgL(-1)> TP > 0.035 mgL(-1), TN and all kinds of inorganic nitrogen were lower in growth season than in non-growth season, and phytoplankton might be the vital regulating factor. When TP < 0.035 mgL(-1), inorganic nitrogen concentrations were relatively low and NH3-N, NO2-N had significant correlations with phytoplankton, indicating that NH3-N and NO2-N might be limiting factors to phytoplankton. In addition, TN/TP went down with decline in TIP concentration, and TN and inorganic nitrogen concentrations were obviously lower in growth season than in non-growth season, suggesting that decreasing nitrogen (especially NH3-N and NO3-N) was an important reason for the decreasing TN/TP in growth season. The ranges of TN/TP were closely related to trophic level in both growth and non-growth seasons, and it is apparent that in the eutrophic and hypertrophic state the TN/TP ratio was obviously lower in growth season than in non-growth season. The changes of the TN/TP ratio were closely correlated with trophic levels, and both declines of TN in the water column and TP release from the sediment were important factors for the decline of the TN/TP ratio in growth season.

Sediment resuspension as a water quality regulator in lakes

Sediment resuspension, the return of the bottom material into the water column, is an important process that can have various effects on a lake ecosystem. Resuspension caused by wind-induced wave disturbance, currents, turbulent fluctuations and bioturbation affects water quality characteristics such as turbidity, light conditions, and concentrations of suspended solids (SS) and nutrients. Resuspension-mediated increase in turbidity may favour the dominance of phytoplankton over macrophytes. The predator-prey interactions contributing to the trophic state of a lake may also be influenced by increasing turbidity. Directly, the trophic state of a lake can be influenced by the effect of sediment resuspension on nutrient cycling. Resuspension enhances especially the cycling of phosphorus by bringing the sedimentary nutrients back into the water column and may thereby induce switches between phosphorus and nitrogen limitation. The contribution of sediment resuspension to gross sedimentation, turbidity, and concentration of SS and nutrients was studied in a small, deep lake as well as in a multibasin lake with deep and shallow areas. The effect of ice cover on sediment resuspension and thereby on phosphorus concentrations was also studied. The rates of gross sedimentation and resuspen¬sion were estimated with sediment traps and the associations between SS and nutrients were considered. Sediment resuspension, caused by wind activity, comprised most of the gross sedimenta¬tion and strongly contributed to the concentration of SS and turbidity in the lakes studied. Additionally, via the influence on SS, resuspension affected the concentration of total phosphorus (TP) and soluble reactive phosphorus (SRP), as well as the total nitrogen to total phosphorus (TN:TP) ratio. Although contrasting results concerning the dependence between the SS and SRP concentrations were observed, it could be concluded that sediment resuspension during strong algal blooms (pH > 9) led to aerobic release of P. The main findings of this thesis were that in the course of the growing season, sediment resuspension coupled with phytoplankton succession led to liberation of P from resuspended particles, which in turn resulted in high TP concentrations and low TN:TP ratios. This development was likely a cause of strong cyanobacterial blooms in midsummer.

Efeitos do enriquecimento com nutrientes (N e P) em diferentes condições de luz sobre o crescimento do fitoplâncton em um reservatório eutrófico no semi-árido brasileiro

The increasing of pollution in aquatic ecosystems in the last decades has caused an expansion of eutrophication and loss of water quality for human consumption. The increase of frequency and intensity of cyanobacteria blooms have been recognized as a major problem connected to water quality and eutrophication. The knowledge of environmental factors controlling these blooms is a key step towards the management for recovering aquatic ecosystems from eutrophic conditions. Primary productivity in aquatic ecosystems is dependent on light and nutrients availability. In the present work we evaluated the relative importance of the concentration of major nutrients, such as phosphorus and nitrogen, and light for phytoplankton growth in the main water reservoir of Rio Grande do Norte State, named Engenheiro Armando Ribeiro Gonçalves (EARG), which is an eutrophic system, dominated by potentially toxic cyanobacteria populations. Limitation of phytoplankton growth was evaluated through bioassays using differential enrichment of nutrients (N and/or P) under two light conditions (low light and high light) and monthly monitoring of chlorophyll-a and nutrients (total nitrogen and phosphorus) concentrations, and water transparency (Secchi depth) at the pelagic region. Our results confirm that EARG reservoir is an eutrophic system with a low water quality. Results of bioassays on the growth of phytoplankton limitation (N or P) were conflicting with the results predicted by the TN:TP ratios, which indicates that these ratios were not a good indicator of algal growth limitation. Nitrogen was the limiting nutrient, considering both frequency and magnitude. Light and hidrology affected phytoplankton response to nutrient enrichment. The extreme eutrophic conditions of this reservoir, dominated by cyanobacteria blooms, demand urgent managing strategies in order to guarantee the multiple uses for this system, including water supply for human population. Although nitrogen is the limiting nutrient, an effective management program must focus on the reduction of both phosphorus and nitrogen input

Spatial and temporal distributions of epiphytic diatoms growing on Thalassia testudinum Banks ex König: relationships to water quality

The spatial and temporal distributions of the epiphytic diatom flora on Thalassia testudinum was described within the Florida Bay estuary and at one Atlantic site east of the Florida Keys over a 1-year period. Species of the genus Mastogloia dominated the epiphytic diatom flora (82 out of 332 total species). Nonmetric Multidimensional Scaling (NMDS) and Analysis of Similarity (ANOSIM) revealed four distinct spatial assemblages and two temporal assemblages. Eastern and western Florida Bay assemblages were identified within the estuary. The eastern diatom assemblage was characterized by high relative abundances of Brachysira aponina and Nitzschia liebetruthii, while the western assemblage was characterized by the abundance of Reimerothrix floridensis, particularly during summer. Two diverse and distinct marine assemblages, one located in the Gulf of Mexico along the western edge of Florida Bay and the other behind the Florida reef tract in the Atlantic Ocean, were also identified. Analysis of the spatial distribution of diatoms and water quality characteristics within Florida Bay suggest that these assemblages may be structured by salinity and nutrient availability, particularly P. The Gulf of Mexico and the western Florida Bay assemblages were associated with higher water column salinities and TP concentrations and lower DIN concentrations and TN:TP ratios relative to the eastern Florida Bay assemblage. The temporal variation in diatom assemblages was associated with water temperature, though temporal indicator species were few relative to the number of spatial indicators.

Nutrient characteristics in the Yangtze River Estuary and the adjacent East China Sea before and after impoundment of the Three Gorges Dam

From November 2002 to 2006, five cruises were undertaken in the Yangtze River Estuary and the adjacent East China Sea to compare the nutrient concentrations, ratios and potential nutrient limitation of phytoplankton growth before and after impoundment (June 2003) of the Three Gorges Dam (TGD). Concentrations of dissolved inorganic nitrogen (DIN), soluble reactive phosphorus (SRP) and total nitrogen (TN) exhibited an increasing trend from 2002 to 2006. In contrast, total phosphorus (TP) concentration exhibited a decreasing trend. The mean concentrations of DIN, SRP, and TN in the total study area increased from 21.4 mu M, 0.9 mu M, and 41.8 mu M in 2002 to 37.5 mu M, 1.3 mu M. and 82.2 mu M in 2006, respectively. while TP decreased from 2.1 mu M to 1.7 mu M. The concentration of dissolved reactive silica (DRSi) had no major fluctuations and the differences were not significant. The mean concentration of DRSi in the total study area ranged from 52.5 to 92.3 mu M. The Si:N ratio decreased significantly from 2.7 in 2002 to 1.3 in 2006, while TN: TP ratio increased from 22.1 to 80.3. The area of potential P limitation of phytoplankton growth expanded after 2003 and potential Si limitation appeared in 2005 and 2006. Potential P limitation mainly occurred in an area of salinity less than 30 after 2003, while potential Si limitation occurred where the salinity was greater than 30. By comparison with historical data, the concentrations of nitrate and SRP in this upper estuary during November 1980-2006 increased obviously after impoundment of TGD but DRSi decreased. Meanwhile, the ratios of N:P, Si:N and Si:P decreased obviously. (c) 2009 Elsevier B.V. All rights reserved.

Mesocosm experiment 2012 on warming and acidification effects on phytoplankton biomass and chemical composition

We investigated the impacts of predicted ocean acidification and future warming on the quantity and nutritional quality of a natural phytoplankton autumn bloom in a mesocosm experiment. Since the effects of CO2-enrichment and temperature have usually been studied independently, we were also interested in the interactive effects of both aspects of climate change. Therefore, we used a factorial design with two temperature and two acidification levels in a mesocosm experiment with a Baltic Sea phytoplankton community. Our results show a significant time-dependent influence of warming on phytoplankton carbon, chlorophyll a as well as POC. Phytoplankton carbon for instance decreased by more than a half with increasing temperature at bloom time. Additionally, elemental carbon to phosphorus ratios (C:P) increased significantly by approximately 5-8 % under warming. Impacts of CO2 or synergetic effects of warming and acidification could not be detected. We suggest that temperature-induced stronger grazing pressure was responsible for the significant decline in phytoplankton biomass. Our results suggest that biological effects of warming on Baltic Sea phytoplankton are considerable and will likely have fundamental consequences for the trophic transfer in the pelagic food-web.

人工湿地强化净化太湖水体富营养化研究

为了进一步降低水中营养盐浓度、提高水体透明度，为湖泊生态系统的恢复创造条件，促进湖泊水体生态系统良性循环，以太湖五里湖富营养化水体为研究对象，采用中试规模的人工湿地技术来强化净化富营养化水体。重点研究了不同流态、不同基质、不同植物及植物有无条件下各人工湿地系统对富营养化水体的处理效果。此外，还对生长在人工湿地中的7种湿地植物芦苇(Phragmites communis)、香蒲(Typha angustifolia)、茭白(Zizania caduciflora)、水葱(Scirpus validus.)、菖蒲(Acorus calamus)、鸢尾(Iris pseudacorus)和千屈菜(Lythrum salicaria)的生长、生理生态特性如气体交换、叶绿素荧光、光合色素含量及氮、磷吸收能力进行了研究，旨在探索高等植物在富营养化水体净化过程中的机理和规律，为人工湿地污水净化机理奠定一定的科学和理论基础。主要研究结果如下： 通过对垂直潜流、水平潜流和自由表面流三种类型的人工湿地系统对富营养化水体净化效果的对比研究，我们发现在水力负荷0.64 m d-1，进水污染物浓度化学需氧量(COD) 7.37 mg L-1、氨氮(NH4+-N) 1.63 mg L-1、硝氮(NO3--N )1.41 mg L-1、总氮(TN) 4.82 mg L-1和总磷(TP) 0.15 mg L-1的条件下，三种不同流态的人工湿地对富营养化水体均有一定的净化功能。三种类型的人工湿地对主要污染物COD、NH4+-N、NO3--N、TN和TP的去除效果分别为：垂直潜流40.4%、45.9%、62.9%、51.6%和64.3%;水平潜流39.6%、32.0%、65.3%、52.1%和65.7%;自由表面流16.5%、22.8%、34.2%、19.8%和35.1%。相比之下，垂直潜流、水平潜流对主要的污染物的去除效果明显好于自由表面流人工湿地。除垂直潜流湿地NH4+-N的平均去除率显著大于水平潜流外，两人工湿地在其余指标的去除效果上无显著差异。考虑到土地面积的限制，就太湖五里湖富营养化水体治理而言，垂直潜流和水平潜流较自由表面流更为适合。 以沸石为基质的人工湿地较以砾石为基质的人工湿地对NH4+-N有很好的去除效果，除此之外两种基质类型的人工湿地在其余各污染指标的去除效果方面差异不显著。但随着湿地运行时间的延长，沸石对NH4+-N的吸收能力会逐渐减弱，考虑到湿地构建成本，建议就地取材，以当地较为廉价的砾石为人工湿地基质比较经济适用。 有无植物对有机污染物COD的去除效果影响差异不显著，但对TN和TP去除效果影响差异极显著，有植物的人工湿地对TN的去除率比无植物的分别高出12.5%和13.4%，对TP去除率分别高出16.9%和31.0%。不同植物对人工湿地处理效果的影响差异不显著，可见湿地流态对处理效果的影响大于植物的影响。 各湿地植物叶片的净光合速率(Pn)日变化均为双峰曲线，有光合“午休”现象。其中芦苇、茭白、鸢尾、菖蒲、水葱和千屈菜Pn的下降主要是由气孔导度(gs)的下降造成的，而香蒲则更多的受叶肉光合能力下降的影响。除千屈菜的Pn与gs之间呈显著正相关外，其余植物的Pn与gs之间均呈极显著正相关。气孔行为对湿地植物光合作用碳的固定显示了明显的主导控制作用。 各湿地植物的光补偿点(LCP)差异不显著，其均值都在10µmol m-2 s-1以上，显示了阳生植物的特性。但湿地植物的光饱和点 (LSP)差异极显著，LSP大小依次为香蒲1476.3µmol m-2 s-1>水葱1140.0µmol m-2 s-1>菖蒲753.7µmol m-2 s-1>芦苇751.7µmol m-2 s-1>茭白640.7µmol m-2 s-1>千屈菜567.3µmol m-2 s-1>鸢尾479.0µmol m-2 s-1。7种湿地植物的CO2补偿点差异极显著，CO2补偿点大小依次为水葱47.1µmol mol-1>茭白28.4µmol mol-1>香蒲23.7µmol mol-1>鸢尾16.8µmol mol-1>菖蒲16.7µmol mol-1>千屈菜15.2µmol mol-1>芦苇14.8µmol mol-1。与此相反，湿地植物的CO2饱和点差异不显著。 各湿地植物的Fv/Fm值大小差异也极显著，Fv/Fm值大小依次为千屈菜0.8168>水葱0.8348>香蒲0.8262>菖蒲0.8198>芦苇0.8168>茭白0.8040>鸢尾0.7930。由此可见千屈菜、水葱较芦苇和茭白有较高的PSⅡ效率。7种湿地植物叶片的叶绿素a、叶绿素b和类胡萝卜素含量水平差异极显著，芦苇和茭白叶片的叶绿素和类胡萝卜素含量水平都较高，这在客观上解释了他们为何拥有较强的光合能力。 不同湿地植物的生物量大小差异极显著，平均生物量(干重)变化范围在0.26-6.65 kg m-2之间。除香蒲和水葱的地下部生物量显著大于地上部外，其余植物都是地上部生物量大于地下部，这非常有利于人工湿地生态工程中通过收获植物地上部生物量来达到去除氮、磷污染目的。 不同湿地植物植株氮、磷含量差异极显著。湿地植物对氮吸收总量变化范围为6.09-93.96 g m-2，吸收氮最高是芦苇，最低是菖蒲;对磷吸收总量变化范围为0.51-8.95 g m-2，吸收磷最高是香蒲，最低是菖蒲。经测算，植物吸收的总氮量占人工湿地总氮去除量的0.6-17.1%，总磷量占人工湿地总磷去除量的1.4-40.5%。本次试验中香蒲和芦苇对氮、磷的吸收去除能力比较高，茭白、鸢尾、水葱和千屈菜的吸收去除能力中等，而菖蒲的吸收能力较弱。

膜生物反应器-复合垂直流人工湿地(SMBR-IVCW)系统处理混合废水的应用研究

本文采用一体式膜生物反应器(SMBR)-复合垂直流人工湿地(IVCW)组合工艺(SMBR-IVCW)系统,研究了该系统对复合废水的净化效果。结果表明,当系统进水为CODCr397～890mg.L-1、氨氮9.40～27.1mg.L-1、TP4.30～10.7mg.L-1、TN45.9～75.8mg.L-1的条件下,在SMBR和IVCW的水力负荷分别为1000L.d-1和375mm.d-1的最优工况下运行,系统CODCr、NH3-N、TN和TP的去除率分别为97.5%、99.0%、59.6%和65.2%;系

生物膜-人工湿地组合工艺处理城镇生活污水的研究

采用以天然植物中空纤维作为填料的生物质-生物膜反应器(BBFR)串联复合垂直流人工湿地(IVCW)的组合工艺处理系统,研究了5种不同的运行工况,即不同的停留时间、水力及污染负荷条件下对城镇生活污水的处理效果。结果表明,5种工况下组合系统的出水均能达到一级排放标准,COD、TN和TP的平均去除率分别达到89.86%、93.5%和74.78%。各工况条件下因为装置控制参数和稳定程度的不同,各运行阶段下的净化效果也有一定的差异。通过探讨BBFR和IVCW的最佳耦合模式,即系统处理效果达到最佳时的运行参数,实现了

三峡水库香溪河库湾底泥中总氮、总磷含量的时空分布

2004年10月—2006年7月,对三峡水库香溪河库湾底泥中总氮(TN)、总磷(TP)含量的时空分布特征及其影响因素进行了分析.结果表明:香溪河库湾底泥中TN、TP含量均表现为"中间高,两头低"的空间分布规律,其中,TN含量最高值为1.08 mg.g-1,出现在库湾中部区域,最低值为0.89 mg.g-1,出现在河口附近区域;TP含量最高值为1.07 mg.g-1,最低值为0.80 mg.g-1,分别出现在库湾中部和库尾.TN含量按秋季、冬季、春季的顺序依次降低,从春季到夏季则大幅上升,夏季达最高值;TP

三峡水库香溪河库湾夏季藻类水华的时空动态及其影响因素

2008年6—8月,三峡水库香溪河库湾相继暴发蓝藻和绿藻水华.依据香溪河库湾夏季的每周监测,对研究区2次水华分别进行聚类和判别分析,研究了2次水华的时空动态及其影响因素.结果表明:研究区2次水华过程均可划分为无水华组、过渡组和水华组;2次水华的暴发对可溶性硅(DSi)、硝态氮与亚硝态氮(NO3--N+NO2--N)和磷酸盐(PO43--P)3种营养盐的吸收程度不同;蓝藻水华暴发期间的DSi、总氮/总磷(TN/TP)、DSi/TN和DSi/TP值均低于绿藻水华;判别蓝藻水华暴发的参数为叶绿素a(Chla)、

旁路生物稳定塘系统净化滇池入湖河道污水

为削减滇池的入湖污染负荷,基于旁路净化的思路设计并构建了包括水生植物塘和养殖塘在内的生物稳定塘系统,考察了对氮、磷的去除效果。结果表明,系统对TN、TP、NO3--N和NH3-N的平均去除率分别为25.3%、50.6%、38.4%和35.6%,在改善水质的同时还具有一定的生态景观效益,可为其他水体的净化提供示范。