Benthic Diatom Communities Along pH and TP Gradients in Hungarian and Swedish Streams

Benthic diatoms are widely used in Europe to assess ecological status of running waters. The aim of this study was to develop models to predict average pH and total phosphorus (TP) for European stream monitoring using combined diatom data-sets from Hungary and Sweden. As first step, the relationship between the measured environmental variables and the distribution of the taxa was checked by classification by using cluster-analysis and CCA. Diatom data separated clearly along the main hydrogeochemical parameters (e.g. alkalinity, pH). Concerning nutrients, TP was the most determinant factor. Predictive value of the TP model (r = 0.96) is high only for the Hungarian data and the pH model (r = 0.97) can be used in both phycogeographical regions.     

The Influence of Environmental,Biotic and Spatial Factors on Diatom Metacommunity Structure in Swedish Headwater Streams

Stream assemblages are structured by a combination of local (environmental filtering and biotic interactions) and regional factors (e.g., dispersal related processes). The relative importance of environmental and spatial (i.e., regional) factors structuring stream assemblages has been frequently assessed in previous large-scale studies, but biotic predictors (potentially reflecting local biotic interactions) have rarely been included. Diatoms may be useful for studying the effect of trophic interactions on community structure since: (1) a majority of experimental studies shows significant grazing effects on diatom species composition, and (2) assemblages can be divided into guilds that have different susceptibility to grazing. We used a dataset from boreal headwater streams in south-central Sweden (covering a spatial extent of ∼14000 km²), which included information about diatom taxonomic composition, abundance of invertebrate grazers (biotic factor), environmental (physicochemical) and spatial factors (obtained through spatial eigenfunction analyses). We assessed the relative importance of environmental, biotic, and spatial factors structuring diatom assemblages, and performed separate analyses on different diatom guilds. Our results showed that the diatom assemblages were mainly structured by environmental factors. However, unique spatial and biological gradients, specific to different guilds and unrelated to each other, were also evident. We conclude that biological predictors, in combination with environmental and spatial variables, can reveal a more complete picture of the local vs. regional control of species assemblages in lotic environments. Biotic factors should therefore not be overlooked in applied research since they can capture additional local control and therefore increase accuracy and performance of predictive models. The inclusion of biotic predictors did, however, not significantly influence the unique fraction explained by spatial factors, which suggests low bias in previous assessments of unique regional control of stream assemblages.     

天津海域底栖线虫群落结构的多元统计分析

应用多元统计分析方法(等级聚类分析和非度量多维标度)研究了天津近岸海域的底栖线虫群落结构情况.结果表明,等级聚类分析和非度量多维标度分析的结果具有很好的一致性.15个取样站位的线虫群落存在差异,根据线虫种类组成和丰度不同,调查站位可以分为4组.中南部近岸海域多数站位的线虫种类组成相似,深水区域的底栖线虫种类变化最大,而北部湾顶海域的线虫组成近似,但与其他站位相差较大.     

Spatial and Temporal Variation of Macroinvertebrate Drift in Two Neotropical Streams1

The detection of spatial variation in macroinvertebrate drift depends on the spatial scale of investigation in streams of the La Selva Biological Station, Costa Rica. Drift samples were taken in a spatially nested design, with two streams, two reaches per stream, two riffles per reach, and four replicate samples per riffle. Drift showed little variation among streams, but varied significantly at the scales of reach and riffle, with variation among samples also high. In addition, sampling took place at two temporal scales: diel and at two different periods that differed in rainfall conditions. Drift diel periodicity was a clear pattern, while only density of individuals varied among sampling periods. This is the first study of macroinvertebrate drift at multiple spatial scales, despite the recognition that multi‐scale studies are essential for a more complete understanding of community patterns and processes.     

Benthic Macroinvertebrates in Streams of the Jaragua State Park (Southeast of Brazil) Considering Multiple Spatial Scales

The study of the distribution of macroinvertebrates, considering multiple hierarchic scales and incorporating different spatial dimensions to assess the role of disturbance in aquatic environments, can contribute to conservation, environmental evaluation and improvement of analytical tools in ecology. The object of this study was to evaluate the diversity of macroinvertebrates in streams of the Jaraguá State Park (SP-Brazil), considering three spatial scales: mesohabitats, segments, and hydrographic basins with different land use parameters (forest, mixed agriculture, organic pollution and deforestation). The samples, collected with a Surber collector, were taken in the beginning of the dry season of 1998. Analysis of data through multiple correspondence analysis showed the importance of variables in macroscale (land use) for the distribution of the fauna in general and the relevance of variability in mesoscale for some taxa in particular. The work points to the necessity of considering different levels of spatial heterogeneity for the conservation of biodiversity in the streams of the park.     

Ecology and Assessment of the Benthic Diatom Communities of Four Lake Erie Estuaries using Lange-Bertalot Tolerance Values

Diatom composition of four Lake Erie estuaries was related to seasonal factors, year, location within the estuaries, and water quality parameters including nutrient and metals concentrations. Canonical correspondence analysis (CCA) revealed seasonality as the most important factor determining variability in diatom species composition among sites and dates. Alkalinity, pH, silicate, orthophosphate, and nitrite concentrations were water chemistry parameters correlated with diatom community composition. Eigenvalues for the first two CCA axes of nutrient/physical data and species data were higher than the first two CCA axes of metals data and species data. In addition, the water quality of these estuaries was evaluated using an index composed of Lange-Bertalot pollution tolerance values. The Lange-Bertalot index scores indicated that the Ashtabula estuary had the best water quality of the study sites. Lange-Bertalot index scores were highly correlated with a gradient of disturbance represented by the first axis of a principle components analysis of sites and nutrient data (Spearman ρ = 0.7). The Lange-Bertalot tolerance values could be useful for discriminating ‘good’ sites from “bad” sites among the Lake Erie estuaries.     

Spatial Scale or Amplitude of Predictors as Determinants of the Relative Importance of Environmental Factors to Plant Community Structure

The literature on tropical rain forest plant‐community relationships with environmental factors usually does not recognize that the relative importance of environmental factors recorded in each study might be due to their amplitude of variation within sites. Geographic scale, however, is recognized as an important modulator of this relative importance. To disentangle the effects of scale and environmental amplitude, ferns and trees in two landscapes of the same size (each 25 km²) with different soil‐fertility amplitudes but similar soil‐texture range were sampled in central Amazonia. We found that major determinants of community structure were the same for ferns and trees. Texture was the main predictor of community structure in the site with homogeneous soil fertility, while availability of exchangeable cations was the main predictor in the site with a wider fertility range. When both sites were analyzed together, soil fertility was the main predictor of community structure and soil texture segregated floristic subgroups within certain ranges of the soil‐fertility gradient. We conclude that: (1) floristic patterns for trees and ferns are congruent; (2) floristic variation depends on the amplitude of the studied gradients, more than on geographical scale; (3) limiting factors are not necessarily the most important predictors of compositional patterns; and (4) communities are structured hierarchically. Therefore, landscape structure (meaning which combinations of environmental factors, their amplitude of variation and which part of the gradient is found within the landscape) affect our perception of the relative importance that environmental factors will have as predictors of species composition.     

Impact of Urban Pollution from the Hanoi Area on Benthic Diatom Communities Collected from the Red, Nhue and Tolich Rivers (Vietnam)

The effects of urban pollution from Hanoi city on the benthic diatom communities of the Nhue–Tolich river system were studied during the 2003 dry season. Benthic diatoms were allowed to grow on glass slides suspended in the water flow for 4 weeks. To reveal the relationship between water quality and diatom communities, Canonical correspondence analysis (CCA) was used on data concerning relative abundances of diatom species and environmental variables. Two diatom indices, IPS and DAIpo, were applied to evaluate water quality in the three rivers. A total of 291 diatom taxa were found in the Red, Nhue and Tolich Rivers. These were mainly cosmopolitan taxa, with some tropical, subtropical and endemic taxa. The most abundant taxa at the Red site were Aulacoseira granulata, Achnanthidium minutissimum, Encyonema minutum, Navicula recens and other halophilous taxa such as Nitzschia kurzii, Seminavis strigosa, Entomoneis paludosa, Bacillaria paradoxa. Diatom assemblages at the Tolich site consisted mainly of Nitzschia umbonata, Nitzschia palea and Eolimna minima. Diatom density ranged from 660 to 30,000 cells/cm². Environmental variables and diatom assemblage composition at all sites were significantly correlated. Two diatom indices gave similar results and indicate the Tolich River with the lowest values as a highly polluted site.     

Regional isolation in the Balkan region: an analysis of craniofacial variation

Biological variation is investigated among contemporary Croatians, Bosnians, American whites, and other multitemporal Balkan populations (World War II Croatians, Macedonians, and Greeks) via multivariate statistics and distance measures of the craniofacial complex. This study demonstrates that there is considerable variation among groups of European ancestry. Bosnians and Croatians who are thought to be relatively homogenous and historically to originate from the same Slav ancestry show local variations. While environmental plasticity has been used to explain cranial changes among human groups, it does not adequately explain the variation observed between Bosnians and Croatians. It is an oversimplification to exclusively attribute the vast range of variability observed among local as well as geographic populations to environmental adaptations.     

Comparative Environmental Assessment in the Studies of Benthic Diatom,Macroinvertebrate, and Fish Communities

Community response to environmental gradients operating at hierarchical scales was assessed in studies of benthic diatoms, macroinvertebrates and fish from 44 stream sites in the New York City watershed. Hierarchical cluster analysis (TWINSPAN) of diatoms and fish partitioned the study sites into four groups, i.e., acid streams, reservoir outlets and wetland streams, large eutrophic streams, and small eutrophic streams; macroinvertebrate TWINSPAN distinguished an additional group of silty eutrophic streams. The correspondence among the three assemblage TWINSPAN groupings was moderate, ranging from 51 to 57%. The similarity across the four major group types was the highest among large eutrophic stream and acid stream assemblages, and the lowest among small eutrophic stream assemblages. Stepwise discriminant function analysis revealed that environmental factors discriminated most effectively the diatom grouping and least effectively the fish grouping. The best environmental predictors for diatom and macroinvertebrate grouping were conductance and percent surface water, while population density was most powerful in separating the fish groups. Carbaryl was the only pesticide that correlated with macroinvertebrate grouping. Partial redundancy analyses suggested a differential dependence of freshwater communities on the scale of the environmental factors to which they respond. The role of small‐scale habitat and habitatland cover/land use interaction steadily increased across the diatom, macroinvertebrate, and fish assemblages, whereas the effect of large‐scale land cover/land use declined.     

Diatom Communities and Water Quality Assessment in Mountain Rivers of the Upper Segre Basin (La Cerdanya,Oriental Pyrenees)

Epilithic diatoms of mountain rivers from the upper Segre catchment (Oriental Pyrenees) were studied in 1998, during three different seasons: March, July and September. Four rivers, the river Segre and its three most important tributaries, Duran, Molina and Querol, were sampled in upstream and downstream stretches. The diatom communities were comparable in all upstream stretches of these mountain rivers draining siliceous substrates. Dominant taxa were Achnanthidium subatomus, Diatoma mesodon, Encyonema cf. minutum, E. silesiacum, Fragilaria arcus, F. capucina, Gomphonema calcifugum, G. pumilum, Meridion circulare and Nitzschia pura. Changes in water quality in the downstream stretches lead to the appearance of pollution tolerant taxa, such as Eolimna minima, Gomphoneis minuta, Navicula gregaria, and Nitzschia inconspicua. As a result, the values obtained with the diatom water quality indices (IPS Specific Polluosensitivity Index, CEE and IBD Biological Diatom Index) decreased. The diatom community composition and the derived water quality values did not change in the upstream stretches over the year. In contrast, significant changes were observed in the downstream stretches with best water␣quality in July, during high flows due to melting snow, and worst values in September, during low␣discharge. The diatom indices, especially the IPS, showed a good performance in these mountain rivers.     

The Effects of Environmental Risk Factors on City Life Cycle: A Link Analysis

ABSTRACT

Due to rapid industrialization and urbanization, social economy develops in an unparalleled speed, while it certainly fosters the consumption of natural resources and the pressure to protect the ecological environment. Hence, there is a two-way relationship between the well-being of humans and the natural environment. In this study, link analysis techniques along with multivariate statistical analysis were employed to discover the effects of environmental risk factors on city life cycle, where suicides, immigration, and emigration were considered as the fundamental indicators of how cities evolve. Association rules, classification trees, MANOVA, and linear discriminant analysis were applied to data on air quality, socioeconomic development, and demographical factors belonging to the cities of Turkey. The results indicate that socioeconomic development levels of cities differ along attraction and life satisfaction dimensions. People tend to choose a city with better development level and better air quality in order to increase their life satisfaction. Additionally, developed cities are less likely to have issues with air quality and citizens who live in a poorly developed city are least satisfied with their lives.     

Iceberg Disturbance and Successional Spatial Patterns: The Case of the Shelf Antarctic Benthic Communities

High-latitude, shelf Antarctic benthic communities are highly diversified and structured, dominated by benthic suspension feeders, and are subject to major natural disturbances. This study focuses on spatial patterns of the Antarctic benthos emphasizing the succession process after iceberg disturbance. For this purpose, underwater photographs (1 m² each) from the southeastern Weddell Sea shelf (<300 m depth) were analyzed using techniques from the field of landscape ecology. Here, we examine measurements of spatial patterns (landscape indices) to describe changes in structural patterns along successional stages on these Antarctic benthic communities. We show a gradual separation from the early to older stages of succession based on sessile benthic cover area, size, shape, diversity, and interspersion and juxtaposition indices. Conceptually, the results describe a gradient from samples belonging to first stages of recovery with low cover area, low complexity of patch shape, small patch size, low diversity and patches poorly interspersed to samples from later stages with higher values of these indices. Cover area was the best predictor of recovery. We conclude that a variety of factors affect the observed successional sequences of Antarctic shelf benthic communities after iceberg disturbance, including the existence and dispersal abilities of propagules, growth rates, and competition between species. Overall, changes in the magnitude, frequency, and duration of disturbance regimes and alterations of ecosystem resilience pose major challenges for conservation of Antarctic benthos. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Mapping the Spatial Extent of Depositional Areas in Agricultural,Urban, and Residential California Streams: Implications for Pyrethroid Toxicity

Wetted stream-bed mapping at randomly selected sites in an agricultural stream (Del Puerto Creek), urban stream (Arcade Creek), and residential stream (Pleasant Grove Creek) in California was conducted to determine the spatial extent of depositional and non-depositional areas. This study evaluated the “representativeness” of standard sediment sampling approaches used in California by using hydrophobic pyrethroids as an example. Measured background concentrations of eight pyrethroids in sediment and potential sediment toxicity for each stream were discussed within the context of depositional areas. Four percent, 15%, and 12% of the randomly selected transects in Del Puerto Creek, Arcade Creek, and Pleasant Grove Creek, respectively, were depositional areas. For all three streams, depositional areas were more dominant in downstream segments. Pyrethroid concentrations in sediment were higher in depositional areas versus non-depositional areas in Del Puerto Creek and were also higher downstream. Pyrethroid concentrations in sediment were also higher in downstream areas of Arcade Creek but generally higher in upstream areas of Pleasant Grove Creek. The results from this study demonstrate the importance of determining “representativeness” of depositional areas for an entire stream if hydrophobic chemicals (pyrethroids) measured in sediment from depositional areas are suspected to be toxic.     

Coral Community Adaptability to Environmental Change at the Scales of Regions, Reefs and Reef Zones

SYNOPSIS. Projected global increases in temperature, sea level,storminess and atmospheric carbon dioxide (CO₂) are likely tocause changes in reef coral communities which the present humangeneration will view as deleterious. It is likely coral communitytrajectories will be influenced as much by the reduction inintervals between extreme events as the projected increasesin means of environmental parameters such as temperature, atmosphericCO₂ and sea-level. Depressed calcification rates in corals causedby reduced aragonite saturation state of water may increasevulnerability of corals to storms. Moreover, reduction in intervalsbetween storms and other extreme events causing mass mortalityin corals (coral predators, diseases, bleaching) are likelyto more frequently "set back" reef coral communities to earlysuccessional stages or alternate states characterized by non-calcifyingbenthos (plants, soft corals, sponges). The greater the areaand the longer the duration of dominance of putative "coral/corallinealgae" zones of coral reefs by non-calcifying stages, the lesswill be the reefs capacity to accrete limestone bulk lockedup in the big skeletal units of late successional stages (i.e.,very large old corals). Averaged over decades to centuries,the effects of such changes on the coral community's carryingcapacity for other biota such as fish are unpredictable. A "shiftingsteady-state mosaic" null model may provide a useful conceptualtool for defining a baseline and tracking changes from thatbaseline through time.     

Bacterial and Archaeal Community Structure in the Surface Diatom Sediments of Deep Freshwater Lake Baikal (Eastern Siberia)

Diatom sediment records of large lakes can be used to decipher the history of ancient phytoplankton. The upper layer of the sediment is an important area of remineralization of the sedimenting phytoplankton biomass. It hosts a bacterial community different from those of both the water column and deeper sediment layers. In this work, we analyzed the structure and diversity of the communities of Bacteria and Archaea in the surface sediment core containing valves of diatoms, the major producers in Lake Baikal. Pyrosequencing of the bacterial V3–V4 region of the 16 S ribosomal RNA (rRNA) and archaeal V1–V3 16 S rRNA gene regions yielded 29,168 and 36,997 reads, respectively. In total, we have identified 33 bacterial phyla; uncultured Actinobacteria were the most abundant in the upper layers, while lower sediment was dominated by Firmicutes and Alphaproteobacteria. The composition of the archaeal community changed with depth, but was generally dominated by Crenarchaeota from the classes Marine Group I and Miscellaneous Crenarchaeotic Group, as well as Euryarchaeota from the class Thermoplasmata. These dominant bacterial and archaeal taxa are presumed to participate in the destruction of buried organic matter, which eventually leads to degradation of the diatom valves.     

Relationships between local population persistence, local abundance and regional occupancy of species: distribution patterns of diatoms in boreal streams

Aims We have two aims: (1) to examine the relationship between local population persistence, local abundance and regional occupancy of stream diatoms and (2) to characterize the form of the species–occupancy frequency distribution of stream diatoms. Location Boreal streams in Finland. There were three spatial extents: (1) across ecoregions in Finland, (2) within ecoregions in Finland, and (3) within a single drainage system in southern Finland. Methods Diatoms were sampled from stones (epilithon), sediment (epipelon) and aquatic plants (epiphyton) in streams using standardized sampling methods. To assess population persistence, diatom sampling was conducted monthly at four stream sites from June to October. The relationships between local population persistence, local abundance and regional occupancy were examined using correlation analyses. Results There was a significant positive relationship between local persistence and abundance of diatoms in epilithon, epipelon and epiphyton. Furthermore, local abundance and regional occupancy showed a significant positive relationship at multiple spatial extents; that is, across ecoregions, within ecoregions and within a drainage system. The relationships between occupancy and abundance did not differ appreciably among impacted and near pristine‐reference sites. The occupancy–frequency distribution was characterized by a large number of satellite species which occurred at only a few sites, whereas core species that occurred at most sites were virtually absent. Main conclusions The positive relationship between local population persistence and abundance suggested that a high local abundance may prevent local extinction or that high persistence is facilitated by a high local cell density. High local persistence and local abundance may also positively affect the degree of regional occupancy in stream diatoms. The results further showed that anthropogenic effects were probably too weak to bias the relationship between occupancy and abundance, or that the effects have already modified the distribution patterns of stream diatoms. The small number of core species in the species–occupancy frequency distribution suggested that the regional distribution patterns of stream diatoms, or perhaps unicellular microbial organisms in general, may not be fundamentally different from those described previously for multicellular organisms, mainly in terrestrial environments, although average global range sizes may differ sharply between these two broad groups of organisms.     

北京八达岭地区灌木群落空间分布格局与土壤环境因子的关系分析

于2007年8月,在北京八达岭地区野外实地踏查的基础上,按海拔梯度每升高100 m布设10个典型灌木样地,共40个样地,分别进行灌木群落调查.采用TWINSPAN方法、依据各样地灌木各物种的重要值对研究区灌木群落进行分类,采用DCCA方法对分类结果进行验证,并选取代表地形因素和土壤因素在内的环境因子共16个指标进行相关分析.结果显示:(1)北京八达岭地区灌木群落共划分为10个类型.(2)北京八达岭地区灌木群落与各环境因子之间有较好的独立性,土壤环境因素对灌木空间分布格局影响较大(特征值为0.90);土壤环境因素中,灌木群落格局与土壤容重因子具有极显著的相关性(P＜0.01).(3)土壤环境因子对灌木群落格局变异的解释能力达到36%;而单纯由地形环境因子的解释能力只有9%,二者交互解释能力为3%,说明土壤环境因素是影响北京八达岭地区灌木群落格局的主导因素. 研究结果表明,北京八达岭地区灌木群落分布格局与土壤容重和海拔因子间存在极显著相关性.     

Measuring Spider Richness: Effects of Different Sampling Methods and Spatial and Temporal Scales

Assessing the richness of invertebrate taxa to aid conservation and management requires a better understanding of the potential sources of error. Patterns of richness for heathland spiders at the species and family levels were compared across three sampling methods, four spatial scales, and monthly intervals (for 16 months). A total of 33 families and 130 species was collected: pitfall traps collected 94% of species, sweep net, 25%, and visual search, 41%. The sampling methods produced variable results. Pitfall trap and sweep net techniques identified significant, yet contrasting spatial differences in the number of families and species at one spatial scale. Pitfall trap data reflected strong temporal variation that influenced spatial patterns in richness (across one spatial scale for families and two for species). The use of broader temporal scales introduced a potential failure to detect significant differences in the richness of ground active spiders, and this risk varied spatially. The sweep net is not recommended for this habitat, although a method that targets the foliage is required for a more complete faunal assessment. Visual searches detected no significant patterns in richness, yet given its potential and increasing use for rapid biodiversity surveys, ways to improve sampling efficiency are suggested.     

Spatial Heterogeneity and Soil Nitrogen Dynamics in a Burned Black Spruce Forest Stand: Distinct Controls at Different Scales

We evaluated spatial patterns of soil N and C mineralization, microbial community composition (phospholipid fatty acids), and local site characteristics (plant/forest floor cover, soil pH, soil %C and %N) in a 0.25-ha burned black spruce forest stand in interior Alaska. Results indicated that factors governing soil N and C mineralization varied at two different scales. In situ net N mineralization was autocorrelated with microbial community composition at relatively broad scales (∼ ∼8 m) and with local site characteristics (`site' axis 1 of non-metric scaling ordination) at relatively fine scales (2–4 m). At the scale of the individual core, soil moisture was the best predictor of in situ net N mineralization and laboratory C mineralization, explaining between 47 and 67% of the variation (p < 0.001). Ordination of microbial lipid data showed that bacteria were more common in severely burned microsites, whereas fungi were more common in low fire severity microsites. We conclude that C and N mineralization rates in this burned black spruce stand were related to different variables depending on the scale of analysis, suggesting the importance of considering multiple scales of variability among key drivers of C and N transformations.