Factors influencing the distribution of chironomids and oligochaetes in profundal areas of Spanish reservoirs

A canonical correlation analysis was performed in order to explain the distribution and abundance of the profundal macrozoobenthos in 71 Spanish reservoirs. Two sets of variables were considered: one set consisted of subgroups of benthic organisms based on their feeding strategy, and the other consisted of environmental variables related to the trophic state of the reservoir.The results showed that densities of phytophagous chironomids decreased with water depth and increased with oxygen content in the bottom waters, while Tanypodinae densities increased with rising densities of phytophagous chironomids and/or oligochaetes, revealing their strong dependence on the abundance of available prey. The abundance of oligochaetes and phytophagous chironomids showed a disjunct distribution with season and depth, suggesting the importance of food quality and sediment texture.Oxygen availability and water depth acted as governing factors for the zoobenthos. Chlorophyll-a was of secondary importance and correlated inversely with the abundance of benthic fauna, especially in summer. Autogenic production coupled with inputs of allochthonous coarse particulate organic matter and a long stratification period lead to long lasting anoxia that reduces the benthic fauna in Spanish reservoirs.Only up to 18% of the variability in the biological data could be associated with the environmental factors considered. Thus, factors other than the trophic state are much more important in reservoirs. Fluctuations of the water level and inputs of organic and inorganic materials coming from the basin are greater than in lakes and act as stressing factors for the benthic fauna.     

乌江流域不同营养水平的梯级水库沉积物中磷形态特征

分析了乌江干流及支流不同营养水平的梯级水库(东风-贫营养、红岩-中营养、乌江渡-富营养)沉积物粒度的垂向分布,并以改进的连续提取法(SEDEX)调查了不同磷形态垂向分布特征。结果表明:3水库沉积物粒径均随深度的增加而减小,东风水库粒径最大,红岩水库其次,处于下游的乌江渡水库粒径最小;乌江渡、红岩和东风水库沉积物总磷(TP)的平均含量分别为2.07、1.22和1.11mg.g-1,总无机磷分别占到总磷53.8%、44.5%和81.9%,有机磷占TP的41.9%、55.5%和18.1%;3水库各形态磷所占比例不同,其中,乌江渡水库交换态磷所占比例相对较大,与其富营养化状态一致;乌江渡水库沉积物表层10cm,各形态磷含量随深度的增加呈下降趋势,红岩水库除交换态磷,其他各形态磷变化趋势不明显。东风水库各形态磷变化趋势不明显;河流梯级开发使下游水库颗粒物粒径变小,从而使下游水体中的磷更易吸附和释放,下游水库沉积物与水体交换也更强烈,除总磷外,交换态磷、自生磷和有机磷也可较好地反映水库富营养程度及演变。     

Examination through a principal component analysis of the phosphorus exchanges between sediments and water in trophically different reservoirs

Phosphorus exchange at the sediment-water interface coupled with several parameters were assessed in several reservoirs with geologically different catchment basins and different trophic status in Morocco and France.The results showed that these exchanges were regulated by a combination of factors: physical chemical variability of the environment, the geological composition of catchment basins and the trophic status of the lake.In the hypereutrophic Villerest, iron-bound phosphorus is the major form of phosphorus trapped by the sediment whereas, in Moroccan reservoirs, calcium-bound phosphorus prevailed.We suggest that a drastic control of phosphorus inputs into the waters must be done through a large program of dephosphatization of tributaries to avoid Microcystis aeruginosa bloom formation in Villerest (Aleya et al., 1993) and calcium-bound phosphorus dissociation in Moroccan reservoirs with upward release of bioavailable phosphorus.

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Résumé Les échanges de phosphore au niveau de l'interface eau-sédiment couplés á la distribution temporelle de divers éléments chimiques et biologiques ont été étudiés dans divers réservoirs de niveaux trophiques différents, au Maroc et en France.Nos résultats mettent clairement en évidence une influence directe de l'environnement physico-chimique, de la nature géologique des bassins versants et de l'état trophique du lac sur la dynamique du phosphore au sein de cette interface.De plus, il apparait que dans le lac hypereutrophe de Villerest (Roanne, France), le phosphore est majoritairement complexé au fer alors que dans les retenues marocaines, ce sont les complexes phosphore-calcium qui prédominent.Nous préconisons un contrôle drastique des apports en phosphore á travers l'installation et la multiplication d'unités de déphosphatation afin d'éviter d'une part, la prolifération massive de la Cyanobactérie Microcystis aeruginosa á Villetest (Aleya et al., 1994) et d'autre part la dissociation des complexes phhosphore-calcium au sein des retenues marocaines avec libération de phosphore biodisponible.

     

The phosphorus status of sediments in a hypertrophic impoundment (Hartbeespoort Dam): implications for eutrophication management

The phosphorus status and distribution of sediments in a hypertrophic water supply reservoir (Hartbeespoort Dam) were investigated, with a view to assessing the role of sediments in counteracting the effects of reduced external phosphorus loading as a restoration measure. In comparison with similar water bodies in South Africa, the sediments in Hartbeespoort Dam contained high levels of both total and potentially mobile phosphorus. The potentially mobile fraction constituted about 60% of the total phosphorus content of the sediments, compared with about 11% in other reservoirs. The excessive eutrophication of Hartbeespoort Dam is clearly reflected in the phosphorus status of the sediments. Sediment distribution in the impoundment was found to be extremely heterogeneous, due to the combined influences of morphometry, hydrology and an imbalance in the nutrient loads entering via rivers at remote points in the water body. It is concluded that sufficient mobile phosphorus has accumulated in the sediments to prolong the response time of the impoundment to phosphorus load reductions. Since phosphorus release from sediments is dependent on dynamic processes not addressed in this study, the extent of the delays in trophic response to load reduction cannot be estimated.     

Factors influencing fish distribution in two desert reservoirs,Central Arizona

Fishes introduced into western reservoirs are intrinsically shallow-water, littoral inhabitants and remain so because of inherent limnological factors characteristic of mid-latitude lentic systems. Depth of euphotic zone and thermocline and dissolved oxygen concentrations limited the majority (90%) of fish in two desert reservoirs to the upper 10 m of water.     

乳山湾东流区沉积物中不同形态磷的分布特征

对2003年8月在乳山湾东流区采集的沉积物样品中的不同形态磷的平面和垂直分布特征进行了分析,并探讨了这些磷的形态分布与贝类养殖的关系,结果表明,不同形态磷在贝类高密度养殖区含量大于低密度养殖区.养殖区的垂直分布比较复杂,在1～20cm范围含量均出现较大波动,这与贝类养殖活动有关.Fe-P、Al-P含量出现较大波动还与污染程度有关,Or-P还与浮游植物活动有关.养殖区Ex-P、Fe-P、NAIP占TP的平均百分含量大于非养殖区,De-P、Oc-P恰好相反.Ca-P是乳山湾沉积物中含量最高的磷形态,Fe-P 和Or-P是最主要的两种生物可获得磷.TP、Or-P含量在养殖区与非养殖区之间没有显著差异,养殖区Fe-P含量高于非养殖区,3种磷的平均含量一般大于其它海区.非生物可获得磷约占TP的60%左右.     

Speciation of riverine particulate phosphorus during rain events

Suspended sediments collected during rain events were analysed to assess the maximum potential bioavailability of particulate phosphorus (PP). Physical (separation by particle size) and chemical (sequential extraction) fractionation techniques were applied. Time differentiated sampling during rain events revealed that changes in the concentrations of soluble and particle bound phosphorus, and in the proportion of different PP phases, are due to the changing contribution of various sources of runoff and to flow related variations in particle size. Size fractionation and the extraction of PP phases, can help to distinguish resuspended sediments from sediments coming directly from outside the channel. In light of a former study, investigating PP sedimentation and transformations within the sediments of Lake Sempach, our results lead to the conclusion that, at least 25% (particulate inorganic and reductive soluble P) and at most 70% of the allochthonous PP supply transported during a single rain event, may become bioavailable after early diagenesis in the lake sediments. The uncertainty is due to the unknown time span necessary for the diagenesis, at the lake sediment surface, of particulate organic phosphorus of allochthonous origin.     

A comparison of phosphorus immobilization in sediments of freshwater and coastal marine systems

The extent to which sediments of aquatic systems immobilize or release phosphorus can affect dramatically the P content of overlying waters. Data from 48 different aquatic systems suggests that there may be a major difference between fresh- and salt-water systems in this immobilization. Under oxic conditions (water overlying sediments had dissolved oxygen > 0.5 mg/L) P is strongly immobilized in sediments of most fresh-water systems. In sediments of most salt-water systems P is released from sediments and behaves, essentially, as a conservative tracer of benthic decomposition. This difference in P cycling is large enough to have an influence on the often cited difference in phytoplankton nutrient limitation between fresh- and salt-water systems.     

湿地沉积物对磷的吸附-解吸动力学模型概述

介绍了常用的吸附-解吸动力学模型(Freundlich方程、Langmuir方程及Temkin模型),分析比较了不同模型之间的相互关系,对目前国内外关于磷吸附-解吸动力学模型研究进行了简要概述,介绍了不同模型的统一表达形式,并提出应加强对不同类型湿地中沉积物对磷的吸附-解吸过程及其动力学模型、对吸附-解吸过程的长期监测和不同环境因子间的交叉效应研究等建议,以深化对动力学模型的认识,从净化机理层面充分理解湿地生态系统的运行机制.     

Different patterns of phosphorus release from lake sediments in laboratory experiments

The phosphorus release from surface sediments of eight lakes, mainly shallow lakes in agricultural areas, was studied in laboratory batch experiments with additions of acetate and/ or nitrate. The lake sediments could be separated into three categories. Some sediments did not release phosphorus under any conditions. The second category showed a high phosphorus release rate when acetate was added, in order to stimulate bacterial activity and oxygen consumption. The addition of nitrate, only, stabilized the redox conditions and prevented phosphorus release. This pattern followed the classical theories of Einsele and Mortimer. The third sediment category released phosphorus up to some level which remained constant throughout the experiment, and was independent of acetate and/or nitrate additions.Several extraction procedures and adsorption-desorption experiments were performed in order to characterize the sediment phosphorus and thus explain the different behaviours of the three sediment categories.     

Factors influencing phosphate exchange across the sediment-water interface of eutrophic reservoirs

The results of a survey of the sediment chemistry of 7 East Anglian reservoirs are presented as part of a regional study on the assessment and control of eutrophication. The influence of water quality (dissolved oxygen, pH, temperature) on phosphate (PO₄) adsorption by sediment from hypertrophic Ardleigh Reservoir is also examined. Extractable phosphate-P (extr.-P) varied between 92 and 383 mg kg^–1 dry matter. Extractable P varied between 5.3 and 16.6% of the total phosphate-P (Tot. P) content and increased with the concentration of dissolved reactive phosphate-P (DRP) in the overlying water column. Organically complexed iron (organic Fe) was the determinand which correlated most closely with phosphate adsorption capacity, PAC (r = 0.8). Organic Fe was also related inversely to Extr. P. The rate and extent of PO₄ adsorption by Ardleigh Reservoir sediment increased with the initial concentration of DRP and adsorption equilibria were reached after 24 h. The equilibrium DRP concentration, [DRP], was 0.7 mg P 1^–1 under aerobic conditions indicative of a high potential for PO₄ exchange. The rate and extent of PO₄ adsorption was greater at 7 °C than at 22 °C PO₄ adsorption increased markedly with dissolved oxygen status. Ardleigh sediment exhibited a marked buffering capacity to a change in pH; however, PO₄ adsorption was greatest at an equilibrium pH of 5.6 and decreased progressively either side of this pH value.Options for the artificial control of sediment PO₄ release are discussed in relation to the seasonal variation in sediment PO₄ exchange observed for Ardleigh Reservoir.     

不同磷源对磷高效利用野生大麦根际土壤磷组分的影响

在土培盆栽条件下,以野生大麦磷高效利用基因型IS-22-30、IS-22-25和低效基因型IS-07-07为材料,研究不施磷(CK)、无机磷(KH₂PO₄,Pi)、有机磷(phytate,Po)及二者混合(KH₂PO₄+phytate,Pi+Po)的方式施磷30 mg·kg^-1时,磷高效基因型野生大麦对磷素吸收利用能力及土壤磷组分特征.结果表明： Pi处理野生大麦干物质量和磷素积累量最大,Pi+Po处理其次,Po处理最小,均显著高于CK处理,且磷高效基因型物质生产和磷素吸收能力显著高于磷低效基因型.土壤有效磷在不同磷源处理间差异显著,Pi处理时含量最高,Pi+Po处理次之,且磷高效基因型野生大麦根际有效磷含量显著高于磷低效基因型.磷高效基因型野生大麦根际有效磷呈现亏缺现象,在Pi和Pi+Po处理时亏缺程度较大.根际与非根际土壤无机磷组分含量为Ca₁₀-P>O-P>Fe-P>Al-P>Ca₂-P>Ca₈-P,且其含量随着Pi的增加而增加.各磷源处理下,磷高效基因型野生大麦根际土壤Ca₂-P、Ca₈-P出现亏缺;Pi处理磷高效基因型野生大麦根际土壤Al-P、Fe-P出现富集.土壤中有机磷各组分含量为中活性有机磷>中稳性有机磷、高稳性有机磷>活性有机磷.野生大麦根际土壤活性有机磷和中活性有机磷呈现富集,其富集量在Pi处理时最大;中稳性有机磷和高稳性有机磷呈现亏缺.各磷源处理下,磷高效基因型野生大麦根际土壤活性有机磷含量显著高于磷低效基因型,中稳性有机磷和高稳性有机磷在基因型间差异不显著.Pi缺乏时,磷高效基因型野生大麦活化吸收Ca₂-P、Ca₈-P、Al-P和活性有机磷的能力较强.     

泉州湾洛阳江河口沉积物中磷的形态分布

分析了泉州湾洛阳江河口沉积物中总磷及5种形态磷(可交换态磷(DP)、铁铝结合态磷(Fe/Al-P)、钙结合态磷(Ca-P)、有机磷(OP)和闭蓄态磷(Re-P))的含量,探讨了它们的垂向分布特征、相互关系及环境指示意义。结果表明:沉积物中的总磷(TP)以无机磷为主,占TP比例76%~89%;除可交换态磷外,沉积物中形态磷的垂向分布规律具有相似性,大体随深度增加而减小,且在表层有富集现象,反映了沉积物中总磷和各形态磷的分布受人类活动影响较明显;通过相关性分析,钙结合态磷是总磷和无机磷的主要控制因素,而总磷和其他形态磷(除了可交换态磷外)相互间均具有显著相关性,且有机质对各形态磷的分布均有一定影响;TP和各形态磷含量,以及(Fe/Al-P)/TP、Ca-P/TP、OP/TP都在同一层出现了显著变化,反映了水利设施和围垦工程对沉积环境和各形态磷迁移转化有较大影响。     

Seasonal phosphorus release from exposed,re-inundated littoral sediments of two Australian reservoirs

Water levels in many reservoirs typically fluctuate seasonally, but the effects of re-inundation of exposed sediments on nutrient dynamics in the water column are poorly known. This study concerns the seasonal differences in the potential of sediments from two Australian reservoirs, after having undergone different degrees of in situ desiccation, to release P under aerobic conditions. Differences were determined between biotic and abiotic P release, and results were also examined in relation to sediment chemistry. The two reservoirs, Carcoar Dam and Lake Rowlands, demonstrated different patterns of P release involving an interactive complex of P release mechanisms. Sediment chemistry at the reservoir margins was important because of the higher concentrations of N, P, Fe and Mn in Lake Rowlands. Physical and chemical processes influenced P uptake and release due to desiccation and oxidation of sediments and were of greater importance in Carcoar Dam. Abiotic P release from sterilised sediments was greater than from unsterilised sediments where both biotic and abiotic processes were apparent. Biotic P uptake and release were especially marked in Lake Rowlands where large macrophyte beds provided a rich source of organic matter. Little seasonal difference in P release was detected. The increased P release from dried sediments has ramifications for internal P loading into reservoirs and for the calculation of P budgets. For managers of reservoirs where large expanses of sediment are exposed during drying, it may be better to maintain high water levels, where possible, during the summer by modifying drawdown practices.     

施磷对川西北高寒草地土壤磷形态及有效性的影响

以川西北高寒草地为研究对象,采用随机区组设计,设置0、10、20、30、40、50、60 g/m²的过磷酸钙(P₂O₅,16%)施肥试验,分析土壤不同形态磷含量和有效磷(Olsen-P)含量变化特征,探究施磷对川西北高寒草地土壤磷形态及有效磷的影响。结果表明：(1)随施磷量增加,土壤总磷(TP)含量先增加后趋于平稳而Olsen-P含量减少。高水平(50、60 g/m²)施磷下氢氧化钠有机磷(NaOH-Po)及残留磷(Residual-P)是高寒草地主要的磷素累积形态,其含量显著高于不施磷处理;(2)树脂交换态磷(Resin-Pi)、碳酸氢钠无机磷(NaHCO₃-Pi)、碳酸氢钠有机磷(NaHCO₃-Po)和氢氧化钠无机磷(NaOH-Pi)含量随施磷量增加整体呈先增加后降低趋势,表层土壤30 g/m²磷肥用量下其值均为最高,分别为21.54、22.94、65.86、64.48 mg/kg。酸溶性无机磷(HCl-Pi)随施磷量增加整体呈下...     

Mass balance models of phosphorus in sediments and water

Models are presented in order of progressively more complex spatial resolution in which the effects on the sediment-water interactions are emphasized. For simple models, the diagnostic approach of calculating the net settling and return of total phosphorus is demonstrated with data from Lake Erie. For more complex models, the effects of interbasin transport and vertical mixing are shown to be important in determining the pathways of the sediment-released or sediment-bound phosphorus in the water column.     

Burial rates and stoichiometry of sedimentary carbon,nitrogen and phosphorus in Midwestern US reservoirs

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Zooplankton composition of ten reservoirs in southern Brazil

The zooplankton of ten reservoirs of Sao Paulo State was analyzed as part of a larger project, Typology of Reservoirs of São Paulo State.Twenty-four genera of Rotifera, six species of Copepoda and at least nine species of Cladocera were found in samples collected on four occasions in 1979. In general, Rotifera dominated in most reservoirs, although fluctuations occurred during the year.The reservoirs were arranged in four groups, according to zooplankton density, whose range was 10 to 500 i 1^–1.The average composition of Crustacea, in number of species at any one time is comparable to those of other water bodies, being a little higher than that of Colorado lakes.The number of species of limnetic Cladocera in Brazil is between those of Holarctic Region and Tropical Asia. Ceriodaphnia cornuta and Bosminopsis deitersi, and a few species of Daphnia are typical of Brazilian zooplankton. Thermocyclops crassus is common in the southern reservoirs but T. minutus seems to be more widely distributed in Brazil. Calanoida occurred in relatively few reservoirs in São Paulo and usually one species at one time. Brachionus and Keratella were more abundant closer to the Equator then to the Tropics, where other genera seem to be more abundant.The range in size of the planktonic Crustacea is relatively small when compared to temperate lakes, being similar to that of other tropical lakes.     

杭州湾潮滩表层沉积物中磷的分布、赋存形态及生态意义

对杭州湾潮滩表层沉积物样品中的磷进行了总量、形态分级提取及生物有效性分析.结果表明:沉积物中总磷的含量为595.5～1268.8μg·g-1,空间分布特征总体表现为杭州湾北岸＞钱塘江杭州河段＞杭州湾南岸.总磷中有89.3%以无机磷形式存在,钙磷、残留无机态磷、有机磷和铁铝结合态磷是沉积物中磷的主要赋存形态,平均分别占总磷的68.3%、14.6%、10.7%和5.3%.钙磷的分布受到盐度变化影响,自钱塘江河口向外海方向明显增加;铁铝结合态磷则相反,分布朝外海逐步递减.沉积物中的潜在生物有效磷(BAP)含量为43.62～177.84 μg·g-1,平均含量为94.13 μg·g-1.该地区与国内典型的河口和滨岸带潮滩比较,总磷处于相对较高水平.强烈的水动力作用及咸淡水交汇使得环境因子频繁变化,加大了沉积物中磷作为内源向上覆水体释放及造成水体富营养化的可能性.     

The influence of nitrate on the phosphorus flux to and from oxygen depleted lake sediments

Addition of nitrate to an oxygen depleted sediment leads to a stimulation of the mineralization process if a major part of the nitrate is dissimilatorily reduced. This may cause an increased release of phosphate from some sediments. Nitrate, however, maintains a high redox potential at the sediment surface and thus prevents a release of iron-bound phosphorus. These two counteracting effects of nitrate addition to sediment-water systems were demonstrated in laboratory experiments. A high supply of nitrate to a phosphorus-saturated sediment caused an increased release of phosphate and ammonium once the nitrate had been used up. However, from other sediments there was no or very little release of phosphate but an increased release of ammonium caused by high nitrate dissimilation, probably due to the very high capacity of these sediments to bind liberated phosphate or due to storage of phosphorus in an increased bacterial biomass. Phosphorus fractionation, before and after the experiments with the sediments, provided information on transfers to, from and within the sediments.