Diatom assemblages in sediments of Lake Juusa, Southern Estonia with an assessment of their habitat

Diatom analysis of surface sediments and two sediment cores from different sedimentation areas of a small closed lake was undertaken with the aim of acquiring knowledge on the dependence of the distribution of diatom assemblages on lake bathymetry. Lake Juusa was selected for the study because we have for this lake a large data set about the lithological composition of sediments and macrofossil and cladoceran records for the Holocene. A high carbonate content (20–60%) in the sediment sequence indicates high carbonacity and relatively stable pH values during the Holocene. On the basis of comprehensive analysis, abrupt water-level fluctuations and changes in the trophic status were established. Results of this study showed that the fluctuations of the water-level were the leading factor determining the habitats of diatom assemblages in the lake. In the surface sediment samples planktonic species such as Cyclotella spp., Stephanodiscus spp. and Aulacoseira spp. had a depth optimum at 3–4 m and the most abundant periphytic taxa were distributed mostly at depths shallower than 3.5 m. The same regularity was established in sediment cores where a good correlation between planktonic species and lake water depth was found in sediments accumulated at water depths >4 m. Lake Juusa appears to be a proper site for detailed environmental reconstructions over the Holocene, and the results will give us a good opportunity to analyse the history of water-level fluctuations in other small Estonian lakes. Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Handling editor: K. Martens     

Stratification of alkaline phosphatase in sediments of two urban lakes and its effect on phosphorus cycle

Phosphorus loadings in sediments play an important role in lake eutrophication and the progress of its recovery. The phosphorus release is controlled by physical, chemical and biological mechanisms. Alkaline phosphatase catalyzes remineralization of organic phosphorus and then it may be an important factor accelerating phosphorus cycling in sediments. In this paper, distributions, properties and function of alkaline phosphatase with depths in sediments of two urban lakes were discussed. Alkaline phosphatase activity (APA) in the sediments of Lake Yuehu decreased with the sediment depth. APA in sediments of Lake Yuehu was, mostly, inhibited by Phe and L-Cys; and inhibiting ability of Phe could be stronger than L-Cys. APA in deeper layer (20–30 cm) of sediments was more sensitive to the inhibitors than other layers, but range of variation in APA was most wide in the subsurface layer (10–20 cm). All the facts implied that alkaline phosphatase occurred in various forms (isoenzymes). APA in the sediments with different depths of Lake Donghu responded Phe differently. Reacted with Phe and incubated for 1 day, the amounts of SRP released by these sediments varied correspondingly. SRP on the overlying water in deeper layers (5–10 cm and 15–20 cm) of Site T1 was higher than that in surface layer (0–5 cm) of the same site, 1 day after incubation. Hence, the SRP release resulted, at least partially, from the hydrolysis of some liable organic phosphorus mediated by APA. Alkaline phosphatase in lake sediments plays an important role in the release of internal phosphorus loadings and eutrophication. A possible explanation for the sensitivity at deeper layers could be another active region of hydrolysis by alkaline phosphatase from organic phosphorus, which added a new dimension in phosphorus cycling mediated by some biochemical mechanisms.     

长江中下游部分湖泊沉积物碱性磷酸酶分布及其作用研究

沉积物磷负荷在湖泊富营养化的发生与恢复过程中具有关键作用,其释放受物理、化学与生物机制调节,而碱性磷酸酶催化有机磷的矿化,故当为促进沉积物磷循环的重要因素。本文讨论了长江中下游部分湖泊沉积物碱性磷酸酶分布及其在磷释放过程中的作用。五里湖疏浚与未疏浚区以及太湖、巢湖、龙感湖、东湖、月湖、龙阳湖、莲花湖等不同湖泊的不同区域表层沉积物碱性磷酸酶活性(APA)明显不同,这种空间异质性与湖泊富营养化程度相联系。此外,APA随沉积物的深度递减,或在中间与较深层次出现峰值,且具明显的季节性。上述事实以及APA对抑制剂的不同响应方式暗示酶存在形态的多样性(同工酶)。苯丙氨酸(Phe)明显提高月湖与五里湖沉积物APA,沉积物与Phe相互作用并静置一天之后,生物可利用性磷(SRP)的释放量明显增加。再者,Phe可抑制月湖沉积物APA,沉积物与Phe相互作用并静置一天之后,SRP释放量无明显变化,溶解有机磷(DOP)的释放量则明显增加。因此,释放的SRP部分来自某些活跃的有机磷的酶促水解,沉积物碱性磷酸酶在内源磷的释放以及富营养化过程中具有重要作用。     

Recent variations in sediment organic carbon content in Lake Soyang (Korea)

Four gravity cores were taken from Lake Soyang, which was created by the construction of an artificial dam in 1973. The variation of organic carbon content of the bottom sediments since the construction was interpreted using a variety of sedimentological and geochemical measurements. Based on the textural properties of sediments and the total organic carbon (TOC) content, it is clear that sediment organic carbon has been deposited very consistently throughout the postconstruction period, except for local sudden inputs caused by summer flooding events near fish farms or farmland areas. The autochthonous input resulting from the enhanced primary production led by phytoplanktons each year is likely to become a major problem at downstream sites within Lake Soyang. The vertical variation of δ¹³C values of sediment organic matter also reflects the fact that the level of autochthonous supply of organic carbon becomes high downstream.An erratum to this article can be found at .     

Sedimentary multiproxy response to hydroclimatic variability in Lagunillo del Tejo (Spain)

Lagunillo del Tejo is a small groundwater-fed sinkhole lake in the karst region of the Iberian Range (central-eastern Spain), which undergoes significant lake level fluctuation in response to rainfall variability. The aim of this study is to understand the record of water level fluctuations in Lagunillo del Tejo over the last two-and-a-half centuries. This information could be used in future studies to interpret longer sedimentary sequences. We analysed photosynthetic pigments, diatoms and cladoceran remains in sediment sequences recovered from the deepest part of the lake. The paleoecological proxies traced two different communities which have switched their prevalence during the past: (1) a planktonic community of algae, including diatoms, chlorophytes, cryptophytes and cyanobacteria, and phototrophic bacteria associated with higher lake level and water column seasonal stratification; (2) a littoral community with the higher levels of macrophyte pigments and associated epiphytic diatoms and chydorids, all of which indicate lower lake level. The levels of coherence between different proxies, each having an independent mechanistic link to lake-level variability, enhance the reliability of palaeolimnological inferences. The high-resolution stratigraphical data from the upper part of the core was compared with lake-level inferences from instrumental rainfall series (1859–2005) to establish the correspondence between Lagunillo del Tejo sediment sequences and climate record. Guest editors: K. Buczkó, J. Korponai, J. Padisák & S. W. Starratt Palaeolimnological Proxies as Tools of Environmental Reconstruction in Fresh Water     

Evaluating diatom community composition in the absence of marked limnological gradients in the high Arctic: a surface sediment calibration set from Cornwallis Island (Nunavut,Canada)

Fossil diatom assemblages preserved within the sedimentary record in Arctic lakes provide the potential to reconstruct past changes in important limnological variables. During the summers of 1992 and 1993, we examined previously unstudied freshwater ecosystems on Cornwallis Island, Arctic Canada, with the specific objectives of (1) documenting the limnology and modern diatom assemblages from this region, and (2) determining which environmental variables most influence diatom species distributions. The Cornwallis Island study sites displayed the least amount of variance in measured water chemistry variables in comparison to nearly all of our labs’ previous freshwater surveys in the Arctic. The small limnological gradients precluded the development of a statistically robust diatom inference model, but perhaps more importantly, allowed us to explore variations in diatom composition in the absence of marked variations in water chemistry. Diatom species turnover was minimal, with the most common diatom taxa being Achnanthidium minutissima, Nitzschia perminuta, N. frustulum, with lesser percent abundances of Chaemaepinnularia soehrensis, Navicula chiarae, Psammothidium marginulata, and A. kryophila. A small number of study sites differed from the majority with respect to water chemistry (e.g., coastal sites with high specific conductivities) and habitat availability (e.g., ephemeral ponds with extensive moss habitats), and these sites had markedly different diatom assemblages. These data reinforce previous observations that water chemistry and other climate-related factors are the primary environmental controls influencing diatom distributions at high latitudes. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The impact of regulation and salinisation on floodplain lakes: the lower River Murray,Australia

Floodplain lakes along the lower River Murray are subject to a wide range of human impacts including regulation, abstraction, elevated saline groundwater tables, increased nutrient and sediment fluxes and introduced biota. These perturbations are superimposed on those arising from high inter-annual rainfall variability, driven, at least in part, by variations in the southern oscillation. Sediment-based archives from two lakes within a complex of wetlands, situated near to the first site of irrigation development in the lower River Murray, reveal substantial changes over the last 800 years. While high levels of salinity are not foreign to the sites, the recent trend is towards sustained high salinity levels. As a result of European impact, freshwater diatom plankton now dominates Loch Luna, whilst Loveday Wetland is both more saline and nutrient rich than in the pre-European period. In Loveday Wetland, the post-1960 increase in Haslea spicula (Hickie) Lange-Bertalot, may be driven by increases in sulphur salt concentrations that are believed to be a cause of recent acidification episodes. A recent increase in more salt tolerant diatoms in Loch Luna suggests that this site, which has been largely buffered from substantial change, is becoming more vulnerable to perturbation. Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users.     

湖泊富营养化治理的生态工程

1996年对长春南湖的富营养化实施了生治理工作,调查结果表明,通过收获水生高等植物和鱼产品带出湖体的P量分别为149．6和189．9kg,通过蚌体生长固定的P量为153.4kg,三者合计492.9kg,与湖体会年P输入量大体持平,生态工程运转后,水质明显好转,湖水中的总P浓度逐年下降,浮游植物个体密度减小,种类数增加,生态工程是城市湖泊富营养化治理较为理想的方法。     

Release of phosphorus from sediments in Lake Biwa

Two sulfur-mediated reactions are resulting in the eutrophication of Lake Biwa, Japan. The iron (II) phosphate mineral vivianite is dissolving in sulfide-enriched sediments that in places results in porewater concentrations of phosphate exceeding 3 mg l⁻¹. The dissolution of phosphate is evident in profiles of total phosphorus where zones of dissolution and a zone of precipitation in the most oxic surface sediments are visible. At times sulfate reduction in these surface sediments results in pH values as high as 9.9, which can dissolve phosphate adsorbed to iron (III). This release of phosphorus from sediments is at least partially responsible for the recent appearance of blue-green algal blooms. Received: August 4, 2000 / Accepted: March 19, 2001     

Sediment diatom assemblages and composition of pore-water dissolved organic matter reflect recent eutrophication history of Lake Peipsi (Estonia/Russia)

A paleolimnological approach was used for the assessment of the recent eutrophication history and identification of possible reference conditions in the large, shallow, eutrophic Lake Peipsi. Lake Peipsi is the fourth largest lake by area, and the largest transboundary lake in Europe, being shared between Estonia and Russia. Lake Peipsi has been anthropogenically impacted over a longer time-scale than that covered by instrumental limnological monitoring. The ²¹⁰Pb record and down-core distribution of fly-ash particles in the 40-cm core from the middle part of the lake suggest 130 years of sediment accumulation. Diatom assemblages indicate alkaline mesotrophic conditions and a well-illuminated water column, sediment pore-water fluorescence index values suggest low autochthonous productivity and a stable aquatic ecosystem similar to natural reference conditions during the second half of 19th and early 20th century. Near-synchronous stratigraphic changes including the expansion of the eutrophic planktonic diatom Stephanodiscus parvus, the appearance of new species associated with eutrophic lakes and the decrease in the relative abundance of littoral diatoms, together with changes in the fluorescence properties of sediment pore-water dissolved organic matter, imply increased nutrient availability, enlarged phytoplankton crops, reduced water-column transparency and the onset of human-induced disturbances in the lake since the mid-20th century. The most conspicuous expansion of eutrophic planktonic diatoms and maximum concentration of siliceous microfossils occur simultaneously with changes in the fluorescence indexes of pore-water dissolved organic matter, indicating a pronounced increase in the contribution of autochthonous organic matter to the lake sediment. This implies that nutrient loading and anthropogenic impact was at a maximum during the 1970s and 1980s. Sedimentary diatom flora may reflect a reduction of phosphorus loading since the 1990s. However, the absolute abundance of planktonic diatoms and sediment pore-water fluorescence index values vary greatly implying that the lake ecosystem is still rather unstable.     

Vertical distribution and release characteristics of phosphorus forms in the sediments from the river inflow area of Dianchi Lake,China

Columnar sediment samples were collected from five representative river inflow areas of Dianchi Lake, China. The vertical distribution of each form of P were tested. Results showed that the concentration of TP in the sediments from areas A, B, C, D and E in the order of D > B > A > C > E, and the average concentration of D, B, A, C and E were 2991, 2064, 1308, 879, and 759 mg?kg^?1, respectively. The concentration of Ex-P, Fe/Al-P, Ca-P and Org-P all decreased with increasing depth. The release of Ex-P was significantly related to TP whereas the Fe/Al-P was not significantly related to TP in the samples from areas polluted by domestic sewage. However, the release of Ex-P and Fe/Al-P were both significantly related to TP in the samples from areas polluted by phosphate mining and phosphate fertilizer application. The results of equilibrium P concentration (EPC0) analysis showed that P in the sediments of areas A, D and E were the source of P in Dianchi Lake, and the P in the sediments of areas B and C were in relative equilibrium with the overlying water.     

Dissolved reactive manganese as a new index determining the trophic status of limnic waters

Dissolved reactive manganese seems to be one of the parameters which determines the trophic status of limnic waters, as suggested by its strong correlations with total phosphorus, chlorophyll a, and water pH. The determination of the trophic status involved the application of reactive manganese due to its bioavailability, providing information on the actual, not just the potential (as in the case of total phosphorus or total organic carbon), threat of water eutrophication.The calculation of trophic states index (TSI) based on the reactive manganese concentration, as determined by TSI_DRMn = 20.61 ln (DRMn) − 35.03, permits the rational assessment of the trophic status of lakes. Oligotrophic lakes are distinguished by concentrations of DRMn < 25 μg/L, mesotrophic by 25–60 μg/L, eutrophic by 60–150 μg/L, and hypertrophic by >150 μg/L.The trophic status of 25 lakes located in central Europe in north-eastern Poland was determined based on the proposed “manganese index” and verified by commonly applied indices proposed by Carlson, Kratzer and Brezonik, and Dunalska.     

Against the tide: the freshening of naturally saline coastal lakes, southeastern South Australia

Diatom analyses of sediment cores extracted from three lakes in coastal southeastern South Australia reveal that, for most of the mid-late Holocene, they were shallow, brackish to saline systems with limited flow of water from continental sources. The construction of a substantial network of drains in the early years of settlement, to maximise transportation and agricultural production through wet winters, lead to abrupt freshening of the lakes. Interestingly, despite substantial nutrient loads to Lake Bonney SE (there are two Lakes Bonney and Frome in South Australia, which is why the lakes in the southeast of the state are differentiated with ‘SE’) associated with the commissioning and expansion of pulp and paper mills, a wastewater treatment plant discharge and agricultural runoff, there is only moderate evidence of nutrient enrichment in the lake, possibly because the post-impact assemblages are dominated by taxa with broad ecological preferences. Despite being preserved within a conservation park, eutrophication associated with agriculture is evident in the diatom assemblages of Lake Frome SE, which has a catchment more than twice that of Lake Bonney SE. Mullins Swamp, on the other hand, supports few indicators of eutrophic conditions. The freshening of these lakes is against the tide of salinisation from rising saline groundwaters in most wetlands across southeastern Australia.     

Analysis of trophic relationships in two shallow equatorial lakes Lake Naivasha (Kenya) and Lake Ihema (Rwanda) using a multispecifies trophic model

A multispecifies trophic model called ECOPATH II, which can be used to describe the trophic relationships in aquatic ecosystems on a quantitative basis, is briefly presented. When properly used, it can help to explain the trophic relationships in ecosystems and possible evolution of fishstocks after modifications of the environment (e.g. eutrophication, introduction of a new population and/or a significant increase of the fishing effort), and to compare the trophic structure of several ecosystems. Examples are provided on two shallow lakes: Lake Ihema and Lake Naivasha. They are compared with Lake George which was previously documented.     

Population responses of Lake Michigan phytoplankton to nitrogen and phosphorus enrichment

A natural phytoplankton assemblage from Grand Traverse Bay, Lake Michigan, was treated with factorial enrichments of nitrate and phosphorus, with maintained nutrient concentrations ranging from 5 to 60 μg total soluble phosphorus liter⁻¹ and 0.225 to 1.12 mg nitrate-nitrogen liter⁻¹.One container was spiked with added vitamins, a chelator, and trace metals. The assemblage response was monitored at the species level. Significant differences in growth rates as a function of nutrient enrichment were detected at both the division and the species levels. Growth rates associated with the various levels of enrichment are reported for several diatom taxa. Many of the diatom taxa exhibited highly significant (P < 0.01) increases in growth rate after phosphorus enrichment, with the largest effects occurring between 5 and 15 μg total soluble phosphorus liter⁻¹. Significant (P < 0.05) N effects were also observed, and the nature of these effects was found to be taxon-specific. Taxa also showed significant changes in percent composition, due both to time and to nutrient enrichment, indicating a substantial heterogeneity in response at the species level. Experimentally induced population changes were qualitatively similar to those observed in regions of the Great Lakes which have undergone anthropogenic eutrophication. Contribution No. 222 of the Great Lakes Research Division, University of Michigan. Work was supported by funds from the Michigan Sea Grant Program and the Environmental Protection Agency. Contribution No. 222 of the Great Lakes Research Division, University of Michigan. Work was supported by funds from the Michigan Sea Grant Program and the Environmental Protection Agency.     

Changes in spatial distribution of phosphorus and nitrogen in the large north-temperate lowland Lake Peipsi (Estonia/Russia)

We investigated changes in the spatial distribution of nitrogen (N) and phosphorus (P) in Lake Peipsi using limnological data from 1970 to 2005. The results show differences in nutrient content between the northern and southern parts of the lake (polarity) and indicate possible causes of eutrophication of this large international lake. The results show a steady gradient in total P (TP) and total N (TN) content along the lake: the northern and deepest part, Lake Peipsi s.s., is significantly less loaded with nutrients than the southern and very shallow part, Lake Pihkva, into which the main inflow, the Velikaya River, discharges. However, the long-term temporal patterns of N and P polarity are different. Statistical analysis, using a parametric functions technique in the framework of general linear analysis provided by the SAS procedures GLM and MIXED, revealed that the polarity of N compounds has been relatively stable over the years and can be related to differences in natural conditions between different parts of the lake. Our study indicates that Lake Peipsi is quite resistant to year-to-year changes in N load, and the in-lake N concentrations are quite stable on a long-term scale. In contrast, the increasing difference in P concentrations between the northern and southern parts of the lake clearly shows that the input of P from the south is increasing. Our results confirm that the anthropogenic input of P is the main reason for the deterioration of the Lake Peipsi ecosystem.     

Role of benthic diatoms in the implementation of the Urban Wastewater Treatment Directive in the River Wear, North-East England

The use of diatoms to monitor rivers in the UK was stimulated largely bythe requirements of the European Union's Urban Wastewater TreatmentDirective. The Trophic Diatom Index (TDI) was developed to assist theinterpretation of benthic diatom assemblages from UK rivers. This paperdescribes how data collected from one river, the River Wear in N-E England,sampled over a five-year period, was used to provide information about thepotential benefits of nutrient removal on major sewage treatment works.Althoughthe TDI indicated a clear increase in eutrophication with distance downstream,interpretation was confused by considerable within-site variability.Multivariate techniques such as TWINSPAN, when used alongside diatom indices,provide a more rigorous interpretation of longitudinal changes. The potentialfor using statistical power analysis to design sensitive monitoring programsusing benthic diatoms is also described.     

Water quality management in the River Gudenaa,a Danish lake-stream-estuary system

Waste water purification has been established to some extent throughout the 3,260 km² catchment area of the River Gudenaa water system during the last 20 years. Biological treatment and phosphorus removal are now undertaken in almost all towns, and organic matter and phosphorus loading from fishponds and farms has been reduced. The pollution abatement strategy employed has been to coordinate and differentiate waste water treatment so as to maximise the environmental benefit/cost ratio. The time lag between implementing an abatement measure and observing an improvement in water quality varies considerably depending on the nature and cultural history of the water bodies involved and the processes occurring during the passage of water between them.Nutrient transformation and retention within water bodies of the Gudenaa system is of great importance for nutrient loading of the downstream lakes and of the estuary (Randers Fjord), and even for the Danish Belt sea. When loading is reduced retention changes, but to a different extent in different water bodies.     

The effect of eyestalk ablation on haemolymph osmotic and ionic concentrations during acute salinity exposure in the freshwater shrimp Macrobrachium olfersii (Wiegmann) (Crustacea,Decapoda)

The location, morphometry, climatic conditions, water balance, hydrology and hydrochemistry of lake Manzala were investigated.Mean annual salinity declined by about 82.7% since 1921, from 16.7 to 2.9% during 1985/86. The nutrient loading increased two or threefold over the past 20 years.These changes are attributed to an increase of the inflow of sewage and agricultural drainage water and restriction of water inflow at the Gamil Lake-Sea Connection since the late 1960's and early 1970's.     

The trophic state of shallow lakes in The Netherlands

A study has been carried out on the development of an ecological assessment method for shallow lakes in The Netherlands. Analyses of eutrophication characteristics of 93 lakes with, in total, 127 sampling localities gave insight into some of the steering variables, such as total-P, total-N, chlorophyll-a and transparency. On the basis of phytoplankton species composition, three main groups of lakes could be distinguished. The first group, characterized by persistent filamentous Cyanobacteria, had the highest summer means of chlorophyll-a and total-P. The second group was characterized by non-persistent filamentous Cyanobacteria, occurring in low abundancies, and at lower chlorophyll-a and total-P concentrations. The third group of lakes was characterized by the absence or very low abundance of the filamentous Cyanobacteria. As a result of these analyses, criteria for the abatement of eutrophication in shallow lakes could be refined.