江汉平原47号钻孔中的化石硅藻及其在古环境分析上的意义

江汉平原47号钻孔,位于湖北省江汉平原的江陵县,在其上段的46.6-2.2m层位上,有丰富的化石硅藻,约有26属148种,其中绝大多数是现存的淡水种类,并以附生性、沿岸带和浅水性的种类为主。种类较多的属有:Navicula(28种)、Cymbella(23种)、Achnanthes(15种)、Gomphonema(14种)和Eunotia(13种)。主要种类有Gomphonema tropicale var. nonpunctatum、Cyclotella comta、Cocconeis placemula vat. lineata和Stephanodiscus dubius等。硅藻中的种数(种/层)和数量(个/每克干沉积物)经历了一个从无到有、由少到多再逐渐减少直至消失的过程。这反映了水体环境也相应地经历了一个漫长的变迁过程:河流(可能是长江古道)→边滩和河漫滩→泛滥平原的积水洼地(湖泊或沼泽)→水体变深加宽→水体消失。从不同沉积相中各种类型(适酸碱度不同)的硅藻比例(即硅藻种谱),可以推测当时水体的酸碱度的变化不大,在中性或中性偏碱的范围。由化石硅藻并结合孢粉的矿物分析,可以推测当时硅藻大量生长繁殖时期的水温较凉,气候可能偏冷。硅藻的数量与沉积物的平均粒度呈明显的相关性,硅藻的种数与沉积物的平均粒度也呈明显的相关性。     

Fossil Diatoms in No.47 Borehole of Jianghan Plain and Their Significance to Paleoenvironmental mental Analysis

The No. 47 borehole is located at Jiangling County in the Jianghan Plain, Hubei Province, China. There are abundant sedimentary diatoms (about 26 genera and 148 taxa) in the upper section (46.6 – 2.2 m) of the borehole. Most of them belong to the existent freshwater diatoms, being mainly epiphytic, littoral and shallow-water-inhabitant species. Among them some gerera are rich in taxa such as Navicula (28 taxa), Cymbella (23 taxa),Achnanthes (15 taxa), Gomphonema (14 taxa) and Eunotia (13 taxa). The dominant species are Gomphonema tropic& var. nonpunctatum, Cyclotella comta, Cocconeis placentula var. lineata and Stephanodiscus dubius, etc. From the lower to the upper section of the sediment, species number (Sp./strat. ) and amount ( Ind./g dry sed. ) of the diatoms underwent a change from scantiness to plenty, then gradually decline to final disappearance. The change of the diatoms obviously reflects a paleoenvironmental change of water bodies in this area, i. e. :at the early stage, this area was possibly a river (might have been an obsolete course of the Yangtze River), then it gradually became a side bank in the river, which later turned into a depression retaining water perphaps in the form of a lake or a swamp in a flood plain. Then it gradually became deepened and widened with final disappearance of the retained water. According to the diatom assemblages in different sedimentary phases, it may be inferred that the pH range in these water bodies were basically stable, ranging from neutral (pH = 7) to slightly alkaline (pH > 7). Combining pollen amdysis (mainly the pollens of Pinus and Betula ) and mineral analysis with diatoms,it might be deduced that the paleoclimate of this area during the period of luxuriant growth of diatoms was somewhat colder than the present time. In the sediment, the amount and species number of the diatoms all significantly correlated with the mean grain size of the sediment.     

唐鱼自然群体栖息地水环境调查

于2005年6月至12月,每两个月一次调查从化市鹿田镇唐鱼自然群体栖息地的水环境,分析了水质、底泥以及浮游生物数量和组成特点。结果表明,栖息地水体6月,12月水质较好,8月总氮含量偏高,10月总氮、总磷含量都高,而COD值一直都较高。底泥的凯氏氮和有机质含量高,而磷含量相对较低。8月浮游植物密度达到最大值,其群落组成特点是,硅藻种数多,蓝藻、绿藻种数少,而数量上,硅藻少,蓝藻多,绿藻次之。8月浮游动物密度大,种数多,其他月份数量和种数相对较少。     

The use of diatoms in monitoring the development of created wetlands at a sandmining site in Western Australia

Former sand-mining pits at Capel, 200 km south of Perth in Western Australia, have been rehabilitated into artificial wetlands since 1975–1979. A chain of fresh water lakes was created as a potential waterbird refuge and an area for passive recreation. Initially, the lakes had low pH, high ammonium, iron and manganese levels and low phosphorus concentration. The lakes were characterised by low diversity of diatoms dominated by acidophilous species. Following an increase in pH in the effluent water discharged into the lake from the mining process plant and landscaping of the lakes since 1988, the diversity of diatoms gradually increased. The system is now dominated by periphytic diatom communities, preferring high conductivity. There has been a marked transition in the diatom community from acidophilous to alkaliphilous species. Planktonic diatom blooms replaced dinoflagellate blooms. Concomitantly, there has been a dramatic increase in the diversity of invertebrates and waterbirds in these lakes. The value of diatoms in assessing the progressive development of created wetlands as self-sustaining ecosystems at sand mines in Australia is discussed.     

Littoral diatoms as indicators for the eutrophication of shallow lakes

The littoral zone of shallow water bodies in the Czech Republic has been studied quite consistently at several fishponds. The use of algae, especially diatoms, for the monitoring of the state of lotic freshwater also has a long tradition. The main objective of the presented paper is to validate the feasibility of the use of littoral periphyton comunities for the biomonitoring of standing waters. At the investigated sites, littoral periphytic diatoms were studied together with selected enviromental variables (pH, conductivity, nutrients – especially total phosphorus) on three types of natural substrates (epilithon, epiphyton, epipelon). The evaluation of the diatom community was performed on the basis of the checklists of algal indicator species published by authors from the Czech Republic, Austria and the Netherlands. The data were subjected to statistical software NCCS 2000 (GLM Anova and ``Ward's minimum'' variance cluster analysis). Littoral periphytic diatoms appear to be good indicators of the fishpond water quality. The selected substrates show non-significant differences therefore the average values from all substrates were used. The best indicatory system for evaluation of Czech fishponds was van Dam's index.

     

扎龙湿地硅藻植物群落季节变化及其对环境的响应

扎龙湿地位于黑龙江省西部、松嫩平原乌裕尔河下游,是我国北方同纬度地区最完整的湿地。于2012年春、夏、秋3季,对扎龙湿地6个代表性区域进行硅藻标本采集,经观察鉴定,发现硅藻植物140个分类单位,包括121种19变种,隶属于2纲6目9科30属。羽纹纲物种较丰富,占总种类数的95%。硅藻植物群落呈现明显的季节演替,秋季硅藻种类丰富度及相对丰度明显高于春、夏两季,优势种多以淡水、半咸水、喜弱碱的种类为主,优势种与水体的盐度和酸碱度存在一定的响应关系。应用典范对应分析(Canonical Correspondence Analysis,CCA)探讨硅藻植物群落变化与环境因子之间的关系。CCA结果显示在扎龙湿地中,水温、电导率、pH、溶解氧是影响硅藻群落结构变化的主要因素,此外总氮、总磷也是硅藻群落季节演替的重要驱动因子。结合硅藻植物多样性指数和硅藻商对扎龙湿地水质进行综合评价,结果显示扎龙湿地整体为中-寡污带水体,部分水域水质较清洁,少数样点受人为因素影响,呈轻污染。     

Benthic Diatom Communities in Subalpine Pools in New Zealand: Relationships to Environmental Variables

In spite of their potential use as indicators of both present and past environmental conditions, little is known about the diatom communities in the many small water bodies at high altitudes in New Zealand. We sampled benthic diatoms at 20 sites in a typical subalpine mire pool/tarn complex near Arthur’s Pass in South Island, New Zealand in the austral spring 2001. The aims were to characterise the diatom communities, including identification of a possible endemic component, and to investigate relationships with environmental variables. The community at genus level was consistent with the peat-bog diatom flora reported from elsewhere except for the common occurrence of the Tasmania/New Zealand endemic genus Eunophora. At the species level, 27 of the 52 most common taxa appear to correspond to known species from the Northern Hemisphere and are therefore presumed to be cosmopolitan in their distribution. Just two taxa are known from the Southern Hemisphere only, however identification of the remaining common species proved problematic. Analysis using the BIO-ENV procedure of the PRIMER computer program confirmed an expected strong association between diatom community composition and pH, with water conductivity and gilvin also important. Weighted averaging regression and cross-validation using C² software enabled selection of four diatom species as potentially sensitive indicators of certain pH levels. Neither species of Eunophora showed a strong preference for pH or for any of the other environmental variables measured, indicating that other factors are determining their distributions. The strength of the species–environment relationships found in this small survey suggests good potential for monitoring current conditions and for palaeoecological applications. Extension of the dataset with information from other alpine/subalpine areas is desirable, as is the compilation of a regional diatom identification guide for these habitats.     

Barcoding diatoms: evaluation of the V4 subregion on the 18S rRNA gene,including new primers and protocols

Diatoms are present in all types of water bodies and their species diversity is influenced greatly by environmental conditions. This means that diatom occurrence and abundances are suitable indicators of water quality. Furthermore, continuous screening of algal biodiversity can provide information about diversity changes in ecosystems. Thus, diatoms represent a desirable group for which to develop an easy to use, quick, efficient, and standardised organism identification tool to serve routine water quality assessments. Because conventional morphological identification of diatoms demands specialised in-depth knowledge, we have established standard laboratory procedures for DNA barcoding in diatoms. We (1) identified a short segment (about 400 bp) of the SSU (18S) rRNA gene which is applicable for the identification of diatom taxa, and (2) elaborated a routine protocol including standard primers for this group of microalgae. To test the universality of the primer binding sites and the discriminatory power of the proposed barcode region, 123 taxa, representing limnic diatom diversity, were included in the study and identified at species level. The effectiveness of the barcode was also scrutinised within a closely related species group, namely the Sellaphora pupula taxon complex and relatives.     

GRADIENT ANALYSIS OF DIATOM ASSEMBLAGES IN WESTERN KENTUCKY WETLANDS1

Diatom and water chemistry data from 35 wetland sites in western Kentucky were used to assess diatoms as indicators of ecological conditions in wetlands. The wetlands were affected by different degrees of acid mine drainage and agriculture. Canonical correspondence analysis indicated that the distribution of diatoms was highly correlated with conductivity and total phosphorus (TP), two variables commonly associated with acidic mine drainage and agriculture, respectively. Diatom-based inference models were developed for use as quantitative indicators of two important environmental variables in wetlands: conductivity and TP. Diatom-inferred conductivity and TP values were highly correlated with measured values. Cross-validation with jackknifing procedures suggested that high apparent r² between inferred and measured conductivity was overly optimistic and should be treated with caution. Jackknifing-derived TP inference models performed poorly in predicting TP toward the ends of low and high TP concentrations. In general, the conductivity inference models based on plankton had better predictability than those based on epiphyton. Epiphyton-based inference models can predict TP better than plankton. Therefore, diatoms in planktonic and epiphytic assemblages could provide complementary information on ecological conditions. Our data suggest that diatoms can reflect major regional environmental gradients and therefore can be used as indicators of the ecological conditions in wetlands. Quantitative inference models with known predictive power can aid the development of realistic and ecologically sound biotic indices for this region.     

Stream epilithic, epipelic and epiphytic diatoms: habitat fidelity and use in biomonitoring

We compared the use of epilithic, epiphytic, and epipelic diatom communities in stream biomonitoring by investigating species composition and relationships with measured water quality variables in two tributaries of the Grand River, Ontario, Canada. Although ordination showed some separation of the epilithon from other habitats, clear habitat preferences and seasonality were not identified. Canonical correspondence analysis showed that measured water quality variables explained the major gradients in the diatom data for all three habitats. The diatoms from each habitat were strongly related to alkalinity, suspended solids, biological oxygen demand and conductivity, and in addition, epipelic and epiphytic diatoms showed significant relationships with total phosphorus. It was concluded that although some species were more abundant in one habitat than the others, the community structure of the epilithic, epiphytic and epipelic habitats from these streams was not consistently different. The results indicate no apparent benefit to sampling discrete habitats for water quality monitoring using diatoms, however, the best relationship are obtained using the sum of the diatom data from all three habitats.     

Subfossil Cladocera in relation to contemporary environmental variables in 54 Pan-European lakes

1. Changes in cladoceran subfossils in the surface sediments of 54 shallow lakes were studied along a European latitude gradient (36–68°N). Multivariate methods, such as regression trees and ordination, were applied to explore the relationships between cladoceran taxa distribution and contemporary environmental variables, with special focus on the impact of climate. 2. Multivariate regression tree analysis showed distinct differences in cladoceran community structure and lake characteristics along the latitude gradient, identifying three groups: (i) northern lakes characterised by low annual mean temperature, conductivity, nutrient concentrations and fish abundance, (ii) southern, macrophyte rich, warm water lakes with high conductivity and high fish abundance and (iii) Mid‐European lakes at intermediate latitudes with intermediate conductivities, trophic state and temperatures. 3. Large‐sized, pelagic species dominated a group of seven northern lakes with low conductivity, where acid‐tolerant species were also occasionally abundant. Small‐sized, benthic‐associated species dominated a group of five warm water lakes with high conductivity. Cladoceran communities generally showed low species‐specific preferences for habitat and environmental conditions in the Mid‐European group of lakes. Taxon richness was low in the southern‐most, high‐conductivity lakes as well as in the two northern‐most sub‐arctic lakes. 4. The proportion of cladoceran resting eggs relative to body shields was high in the northern lakes, and linearly (negatively) related to both temperature and Chl a, indicating that both cold climate (short growing season) and low food availability induce high ephippia production. 5. Latitude and, implicitly, temperature were strongly correlated with conductivity and nutrient concentrations, highlighting the difficulties of disentangling a direct climate signal from indirect effects of climate, such as changes in fish community structure and human‐related impacts, when a latitude gradient is used as a climate proxy. Future studies should focus on the interrelationships between latitude and gradients in nutrient concentration and conductivity.     

大亚湾澳头水域浮游植物群落结构及周年数量动态

对1997年至1998年广东省大亚湾澳头水域的浮游植物群落进行调查和分析。结果发现浮游植物65属198种;硅藻在种类组成和数量上都比甲藻占有优势,存在春季和秋季高峰,主要优势类群依次是角毛藻、骨条藻、拟菱形藻等;甲藻只存在春季高峰,代表种类有裸甲藻、原甲藻等。主要优势种类的生长与调查水域的盐度没有明显关系,但全年水温的季节性变化对优势种类的消长影响显著。Simpson多样性指数、Shannon-Weaver多样性指数、均匀度的年平均值分别是0.611、2.107、0.557,多样性指数没有明显的季节变化规律和水平分布规律。       

Mercury in the muscle tissue of fish in the Central and South Vietnam

The content of mercury has been determined in the muscle tissue of 18 fish species in rivers, lakes, and reservoirs of Central and South Vietnam. The region is characterized by lower metal concentrations than those in water bodies in temperate and northern latitudes. In 76% of samples (n = 986), the content of Hg was ≤0.5 μg Hg/g of dry (≤0.1 μg/g of wet) tissue weight. In water bodies and watercourses of tropical latitudes, interspecific variations in fish can be one of the factors responsible for a wide range of Hg variation within the same species.     

Comparative study of monitoring South-Finnish rivers and streams using macroinvertebrate and benthic diatom community structure

In southern Finland, most of the rivers are turbid and suffer from eutrophication and leaching of suspended solids from diffuse sources. We first related benthic diatom and macroinvertebrate structure to environmental factors using direct ordination. Second, benthic diatoms and macroinvertebrates were simultaneously sampled in several South-Finnish rivers and streams to compare two monitoring methods. The study sites constituted of some large, moderately nutrient rich rivers and some smaller, less eutrophic streams situated on the south coast of Finland. Diatom species distribution was most affected by conductivity, total P and latitude. Species distribution of macroinvertebrates was mostly related to channel width, conductivity and pH. For diatoms, separation of community structure between sampling stations was clear, but corresponding macroinvertebrate communities were more similar to each other. Correlation between diatom and macroinvertebrate pollution indices was rather low and insignificant (r = 0.28). As a whole, variation of macroinvertebrate index values (CV = 4.7%) among replicate samples was slightly lower than for diatom index (CV = 6.0%). On the contrary, community similarity between the replicate samples was slightly lower among macroinvertebrates (r = 0.770) due probably to their larger local scale spatial variation, sampling of more habitats and lower density compared to diatoms (r = 0.874). In conclusion, multiple pressures affecting the river ecosystems at different spatial and temporal scales should lead to choosing more than one biological monitoring method with clearly identifiable responses.     

The epipsammon; a relatively unknown freshwater algal association

A freshwater diatom flora has been shown to exist on sand grains. The species have been determined from samples of four bodies of water. This epipsammic flora is composed of minute diatoms, many of which require electron microscope study before their identification can be made certain. The chemistry of the water undoubtedly influences the association of species.     

Algal communities of a geothermally heated lagoon on Deception Island (South Shetland Islands)

Kroner Lake, located at Deception Island (Maritime Antarctica), is a unique geothermally heated lagoon in Antarctica. It is declared as special site of scientific interest (SSSI) by Scientific Committee for Antarctic Research (SCAR) for its high biodiversity. A sharp environmental heterogeneity is registered in this lagoon, due to its connection to the sea in its southern margin, and to the input of warm freshwater in the northern one (because of hot springs). This study analyses the biodiversity and abundance of the algal communities (phytoplankton and benthic assemblages) and their relationship with environmental factors. In particular, strong spatial differences of both temperature and conductivity were recorded. The biological studies revealed that the phytoplankton (nanoplankton and microplankton) was dominated by marine diatom species, while the pico-sized fraction was composed by Cyanobacteria Synechococcus-like cells. The epipelon was mainly represented by chain and tubicolous diatoms, among which, Melosira nummuloides was one of the most abundant species. Filamentous Cyanobacteria were also frequently recorded in the algal mats. Kroner Lake is subject to a strong marine influence. Phytoplankton is absolutely dominated by marine diatoms. Spatial variations in temperature and conductivity recorded in the lagoon influence the distribution of the aquatic communities. The greater abundance of pico-sized cells coincided with the warmest site of the water body. Regarding the benthic community, the contribution of freshwater and brackish species is comparatively more important than for the phytoplankton, although the high contribution of marine-derived algae was also evident.     

The use of periphytic diatoms as a means of assessing impacts of point source inorganic nutrient pollution in south-eastern Australia

1. Periphytic diatoms are used as indicators of water quality because their ecological tolerances or preferences to environmental variables are thought to be predictable. However, much of the present autecological information for periphytic diatoms has been derived from studies conducted in the northern hemisphere. In this present study we used periphytic diatoms to determine the impacts of inorganic nutrient pollution in a tidal river system in the temperate latitudes of south‐east Australia. In so doing, we assess the suitability of the use of the ‘northern hemisphere’ ecological tolerance/preference data for periphytic diatoms. 2. Artificial substrates were used to collect periphytic diatoms at 35 sites, which were positioned along the riverbanks and the middle of the river at various distances upstream and downstream of the sewage outfall. The sampling design took into account tidal excursions and the observed sewage plume dynamics. Periphytic diatoms were collected during the austral winter month of August and the austral spring months of September and October. We deployed the artificial substrates for 4 weeks to allow the periphytic diatoms to recruit and colonise, before identifying and enumerating the assemblages. 3. Data analysis included two approaches: multivariate visualisations of combinations of environmental and biological data to investigate shifts in species structure of the periphytic diatom assemblage and multimetric indices based on ecological tolerance/preference data. 4. We found that the spatial patterns inferred from multivariate and multimetric analyses were consistent. Temporal variation in the composition of the periphytic diatom assemblage was greater than the spatial variation along horizontal sections of the river (in any one deployment) due mainly to shifts between winter and spring species. 5. Outfall effects were most apparent in winter, possibly because subsequent deployments were swamped by growth of spring periphytic diatoms. The outfall effects included a shift towards pollutant tolerant species and a reduction in the variability of the periphytic diatom assemblage across the river. 6. We conclude that the use of periphytic diatoms and associated ecological tolerance/preference data as a means of assessing impacts of point source inorganic nutrient pollution is effective. An understanding of river and sewage flow patterns is essential to the design of appropriate monitoring programmes and to the interpretation of results, especially as periphytic diatoms are sensitive to many environmental variables.     

Bacterial community composition over a dry winter in meso- and eutrophic Portuguese water bodies

In order to investigate the bacterial diversity in a number of rivers, reservoirs and lakes in northern and central Portugal during the winter of 2004/5 (atypically dry), we applied molecular methodologies, namely denaturing gradient gel electrophoresis with primers targeting fractions of the bacterial 16S rRNA gene. Environmental parameters such as pH, conductivity, inorganic nutrients, total suspended solids and chlorophyll a were determined in order to characterize the trophic status of the studied water bodies. We found water bodies with oligotrophic to hypereutrophic characteristics. Organisms belonging to the Bacteroidetes and Alphaproteobacteria were found at the highest pH environment. Bacteroidetes were also related to high nutrient concentrations. Verrucomicrobia were associated with the most oligotrophic reservoir and low pH values. Actinobacteria were present in all samples from lakes and reservoirs, indicating its preference for lentic water bodies. Cyanobacteria dominance was related to high pH and conductivity levels. In general the conductivity values recorded in winter 2005 were the highest over recent years and chlorophyll a also reached very high levels. The data emphasize an enhanced risk of eutrophication for the studied water bodies, especially in the subsequent months when the temperature rises.     

Epidiatomic diatoms: An insight into interaction specificity

Little is known about direct interactions between diatoms. In this study, small diatoms attaching onto larger benthic and motile diatoms were considered. This phenomenon is commonly considered as epiphytism (with diatom epiphytes) although the exact nature of this interaction has not been investigated yet. The question that was addressed here is the specificity of the interaction, simply by observing species associations in their natural environment. A comparison of this special form of epiphytism was carried out between two sites, on a Mediterranean river and one of its tributaries. The results showed both host and epiphyte selection, but with some variability in species associations. This excludes the two alternative hypotheses that (i) large diatoms are a neutral substrate for smaller diatoms and that (ii) the interactions are strictly specific between two species.     

Melosira distans var. tenella and Eunotia zasuminensis, two poorly known planktonic diatoms in Finnish lakes

The occurrence and ecology of two poorly known planktonic diatoms, Melosira distans var. tenella (Nyg.) M.-B. Florin and Eunotia zasuminensis (Cabejsz.) Körner in central Finland is discussed. Both species have their maximum in late summer when water temperature is > 15°C and they prefer slightly acid water (pH < 7), low conductivity (less than 4 mS/m) and a moderate degree of dystrophy with C.O.D. 10–20 mg O₂/l and water colour 60–120 mg Pt/1. Melosira distans var. tenella was found in ca. 80% of the central Finnish lakes studied, but it is not reported in previously published papers. Eunotia zasuminensis is rarer, but is, however, recorded in at least 22 lakes in central Finland.