Fixed Sampling Sites Research Articles

High-resolution spatial and spatiotemporal modelling of air pollution using fixed site and mobile monitoring in a Canadian city

The development of high-resolution spatial and spatiotemporal models of air pollutants is essential for exposure science and epidemiological applications. While fixed-site sampling has conventionally provided input data for statistical predictive models, the evolving mobile monitoring method offers improved spatial resolution, ideal for measuring pollutants with high spatial variability such as ultrafine particles (UFP).The Quebec Air Pollution Exposure and Epidemiology (QAPEE) study measured and modelled the spatial and spatiotemporal distributions of understudied pollutants, such as UFPs, black carbon (BC), and brown carbon (BrC), along with fine particulate matter (PM2.5), nitrogen dioxide (NO2), and ozone (O3) in Quebec City, Canada. We conducted a combined fixed-site (NO2 and O3) and mobile monitoring (PM2.5, BC, BrC, and UFPs) campaign over 10-months. Mobile monitoring routes were monitored on a weekly basis between 8am–10am and designed using location/allocation modelling. Seasonal fixed-site sampling campaigns captured continuous 24-h measurements over two-week periods. Generalized Additive Models (GAMs), which combined data on pollution concentrations with spatial, temporal, and spatiotemporal predictor variables were used to model and predict concentration surfaces.Annual models for PM2.5, NO2, O3 as well as seven of the smallest size fractions in the UFP range, had high out of sample predictive accuracy (range r2: 0.54–0.86). Varying spatial patterns were observed across UFP size ranges measured as Particle Number Counts (PNC). The monthly spatiotemporal models for PM2.5 (r2 = 0.49), BC (r2 = 0.27), BrC (r2 = 0.29), and PNC (r2 = 0.49) had moderate or moderate-low out of sample predictive accuracy. We conducted a sensitivity analysis and found that the minimum number of ‘n visits’ (mobile monitoring sessions) required to model annually representative air pollution concentrations was between 24 and 32 visits dependent on the pollutant.This study provides a single source of exposure models for a comprehensive set of air pollutants in Quebec City, Canada. These exposure models will feed into epidemiological research on the health impacts of ambient UFPs and other pollutants.

Assessing the utility of shellfish sanitation monitoring data for long-term estuarine water quality analysis

Regular testing of coastal waters for fecal coliform bacteria by shellfish sanitation programs could provide data to fill large gaps in existing coastal water quality monitoring, but research is needed to understand the opportunities and limitations of using these data for inference of long-term trends. In this study, we analyzed spatiotemporal trends from multidecadal fecal coliform concentration observations collected by a shellfish sanitation program, and assessed the feasibility of using these monitoring data to infer long-term water quality dynamics. We evaluated trends in fecal coliform concentrations for a 20-year period (1999–2021) using data collected from spatially fixed sampling sites (n = 466) in North Carolina (USA). Findings indicated that shellfish sanitation data can be used for long-term water quality inference under relatively stationary management conditions, and that salinity trends can be used to investigate management-driven bias in fecal coliform observations collected in a particular area.

Quantifying metallic components in aerosol filter samples using micro-synchrotron radiation X-ray fluorescence: With quartz filter as an example

Metals in atmospheric fine particulate matter (PM2.5) are presumed to have toxic effects. For environmental epidemiological studies, measuring the metallic components of PM2.5 collected by personal samplers and quartz fiber filters (QFF) has two key advantages: reducing exposure misclassification and enabling analyses of multiple (organic and inorganic) components on a single filter. We developed a sensitive, low-sample-consumption method to quantify the metallic components of PM2.5 collected on QFFs using micro-synchrotron radiation X-ray fluorescence (μ-SRXRF). Teflon filter is used here as a reference to test the substrate applicability of QFF. This method requires only a 5-mm-diameter portion of a QFF and can simultaneously quantify 15 metals with atomic numbers Z = 19–34 (i.e., K–Se, excluding Sc). The analysis time for each sample was 120–360 s, and the method detection limits were 0.04–36.6 ng/m3. We validated this method by performing cross-comparisons with two external methods: offline inductively coupled plasma mass spectrometry (ICP-MS) and online X-ray fluorescence (XRF). The slopes of the linear fits between the μ-SRXRF and offline ICP-MS methods varied from 0.40 to 1, with R2 values ranging from 0.62 to 0.98. The slopes of the linear fits between the μ-SRXRF and online XRF methods were between 0.29 and 0.89, with R2 values ranging from 0.39 to 0.80. We applied the proposed method to analyze 391 personal PM2.5 samples collected in an epidemiological study conducted in urban Beijing. By comparing the results with the ambient concentrations from a fixed monitoring site, we found that the concentrations of some metallic components in personal PM2.5 samples were significantly different from those in the corresponding fixed-site samples, with up to an order of magnitude difference. Because personal sampling can reduce the potential for exposure misclassifications, the high-resolution temporal analysis of metallic components in personal samples using the μ-SRXRF method could be a useful approach for exploring the health risks and identifying the sources of metallic components of PM2.5.

Distribution characteristics of microplastics and corresponding feeding habits of the dominant shrimps in the rivers of Chongming Island

There is increasing global concern regarding microplastics. Rivers play a key role in the transportation and storage of microplastics on the Earth's surface. Here, we aimed to investigate the spatial-temporal variations in the distribution of microplastics in water as well as in the dominant species of the macrobenthic fauna Exopalaemon modestus and Macrobrachium nipponense in the river system of Chongming Island by setting up 16 fixed sampling sites. We found that the abundance of microplastics in the water of the rivers on the Chongming Island was 0.48 ± 0.10 n/L. There was no significant difference among different reaches. The abundance of microplastics in the major rivers was significantly higher in summer than in the other seasons. Detection rates of microplastics in Exopalaemon modestus and Macrobrachium nipponense were 50.12 % and 64.58 %, with mean abundances of 1.92 ± 0.52 n/g and 1.49 ± 0.30 n/g, respectively. The composition characteristics of the microplastics in shrimps were affected by the microplastics in the aquatic environment. The microplastic content in the shrimps and water were linearly correlated in terms of the same characteristics (shape, color, and polymer). Shrimps showed a stronger feeding preference {Target Group Index (TGI) > 1} for microplastics with fibrous shapes, transparent and green colors, rayon (RA) and polyethylene (PE) polymers, and relatively small sizes (<400 μm). These results indicate that shrimps prefer to consume microplastics that have similar appearance to their prey. Their benthic dwelling habits may limit their feeding space to the bottom of the water, which in turn leads to an increase in the feeding probability on microplastics of greater densities (e.g., RA). The catabolism of microplastics in shrimps may lead to an overestimation of their feeding preference for smaller sizes. Further controlled experiments should be carried out to obtain deeper insights into the preferences of shrimp for microplastics.

Fixed Site Sampling Versus Modified Fixed Site Sampling with a Random Sampling Component for Optimizing Early Detection Monitoring of Non-Native Fishes

Standardized sampling of fishes is either probabilistic (i.e., random) or non-probabilistic (i.e., fixed), with each having advantages and disadvantages. Our study objective was to evaluate whether a fixed site-survey design for early detection monitoring of non-native fishes could be improved by modifying fixed site selection and adding random sampling. Results were largely similar but varied by evaluation metric; accumulation curves of species suggested that performance of the fixed survey design was 10% higher than the modified survey and also accumulated species significantly faster from 1 to 42 units of effort. Results indicated the fixed site survey previously took advantage of the patchiness in fish distribution, leaving little potential efficiency to gain using the modified survey design. We would like to emphasize that the modified survey design was effective, just not as effective as the fixed site survey, and could likely optimize early detection monitoring (EDM) for programs with less available fish data to draw observations from or if only random sampling was used for monitoring.

A novel approach to discriminate sedimentary characteristics of deltaic tidal flats with terrestrial laser scanner: Results from a case study

AbstractSediments in deltaic tidal flats regulate physical and chemical processes. Grain‐size distribution plays an important role in determining sediment dynamics and substrate properties. However, it is challenging to quantify large‐scale depositional environments in intertidal flats, due to time‐consuming grain‐size analyses and sparse sedimentary information extracted from scattered sediment samples. In this study, a novel terrestrial laser scanner (TLS) based method was developed to characterize the substrate of an intertidal flat. Surface sediment samples in the Nanhui flats in the Yangtze Delta, China, and the corresponding waveform amplitudes of TLS echoes at fixed sampling sites were collected for a total of 22 months. A negative logarithmic relationship was found between the sediment sand fraction, average grain size, D50, and corrected waveform amplitude of TLS echo in different hydro‐meteorological conditions. The mean of average grain size of five sediment sampling sites along a transect was 58.78 μm when measured by traditional grain‐size analysis, and 49.48 μm when calculated with the proposed logarithmic equation. The mean error at each site was up to 21.77%. The mean error for the sand and silt fraction at each location was as high as 27.28% and 21.75%, respectively. The spatial distribution pattern of TLS‐based average grain size in the entire study area was consistent with the measured pattern with a Root Mean Square Error of 13.83 μm. These errors could be caused by the accuracy of the TLS waveform amplitude correction and by limits of the method in recognizing different substrates. The effects produced by the presence of microphytobenthos (for example, cyanobacterial mats or diatom biofilms) or bedforms have not been investigated and may have affected the results. The TLS‐based grain‐size measurements can rapidly and effectively discriminate sediment characteristics, thus avoiding traditional time‐consuming measurements. It is expected that the TLS‐based method proposed here will have wide applications in shoreline studies, especially in inaccessible tidal flats.

Seasonal Phenological Patterns and Flavivirus Vectorial Capacity of Medically Important Mosquito Species in a Wetland and an Urban Area of Attica, Greece.

Seasonal patterns of mosquito population density and their vectorial capacity constitute major elements to understand the epidemiology of mosquito-borne diseases. Using adult mosquito traps, we compared the population dynamics of major mosquito species (Culex pipiens, Aedes albopictus, Anopheles spp.) in an urban and a wetland rural area of Attica Greece. Pools of the captured Cx. pipiens were analyzed to determine infection rates of the West Nile virus (WNV) and the Usutu virus (USUV). The data provided were collected under the frame of the surveillance program carried out in two regional units (RUs) of the Attica region (East Attica and South Sector of Attica), during the period 2017–2018. The entomological surveillance of adult mosquitoes was performed on a weekly basis using a network of BG-sentinel traps (BGs), baited with CO2 and BG-Lure, in selected, fixed sampling sites. A total of 46,726 adult mosquitoes were collected, with larger variety and number of species in East Attica (n = 37,810), followed by the South Sector of Attica (n = 8916). The collected mosquitoes were morphologically identified to species level and evaluated for their public health importance. Collected Cx. pipiens adults were pooled and tested for West Nile virus (WNV) and Usutu virus (USUV) presence by implementation of a targeted molecular methodology (real-time PCR). A total of 366 mosquito pools were analyzed for WNV and USUV, respectively, and 38 (10.4%) positive samples were recorded for WNV, while no positive pool was detected for USUV. The majority of positive samples for WNV were detected in the East Attica region, followed by the South Sector of Attica, respectively. The findings of the current study highlight the WNV circulation in the region of Attica and the concomitant risk for the country, rendering mosquito surveillance actions and integrated mosquito management programs as imperative public health interventions.

Spatial and temporal variability of airborne ultrafine particles in the Greater Montreal area: Results of monitoring campaigns in two seasons

It has been hypothesized that ultrafine particles (UFP) in air pollution may cause lung cancer. In preparation for an epidemiologic case-control study to assess this hypothesis in Montreal, Canada, we conducted a UFP measurement campaign in order to create an exposure surface with which we could assign UFP exposure to subjects corresponding to their residential addresses. The purpose of this paper is to describe the temporal and spatial variability that underlies the creation of an exposure surface in the Montreal area, and to consider the implications for epidemiological exposure assessment.We identified 249 fixed sampling sites, selected to provide a dense spatial representation of the areas of residence of Montreal residents. We conducted a winter campaign and a summer campaign, and each of the sites was visited three times during each seasonal campaign. Each visit entailed a 20-minute measurement period for UFPs with a separate measurement each second. This provided data for temporal comparisons at each site between seasons, between visits and between seconds. The median of UFP measurements was 16,593 particles/cm3 in winter and 8919 particles/cm3 in summer. Across the 249 sampling sites the Spearman correlation coefficient between the UFP measurements of winter and summer was 0.35. Within each visit, correlation was below 0.50 between pairs of UFP measurements taken more than 60 s apart, and there was hardly any correlation among measurements taken more than 300 s apart. When sites were grouped by proximity to certain types of pollution sources, and the seven resulting groups compared, there were modest, albeit statistically significant, differences in UFP levels. There was moderate positive spatial autocorrelation in UFPs over the study area. High temporal variability of UFPs from short-term measurements campaigns will likely compromise the predictive validity of the exposure surface, and will eventually attenuate the epidemiologic risk estimates.

崇明岛内河夏季鱼类群落组成及分布特征

PDF HTML阅读 XML下载 导出引用 引用提醒 崇明岛内河夏季鱼类群落组成及分布特征 DOI: 10.5846/stxb202002240321 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 上海市科委项目（19DZ1203801）；国家自然科学基金（41977344，41761144062） Community composition and distribution characteristics of the fish assemblages in the rivers of Chongming Island in summer Author: Affiliation: Fund Project: Science and Technology Committee of Shanghai Municipality, The National Natural Science Foundation of China 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:崇明岛为世界最大的河口冲积沙岛，岛内河网水系发达。2018年6月，选择崇明岛内主要代表性河道包括北横引河、南横引河和竖河（庙港、堡镇港、八滧港），设置16个固定站点，对内河鱼类开展了拖网调查，分析了崇明岛内河夏季鱼类群落组成及分布特征。调查期间共采集到鱼类4417尾，分属6目9科30种，主要为鲤形目鲤科鱼类；其中，淡水鱼类27种，洄游鱼类2种，近海鱼类1种。从空间分布来看，北横引河记录鱼类20种，南横引河记录鱼类17种，竖河记录鱼类18种，不同河道鱼类种类组成及优势种特征存在明显差异，其共有优势种为鲫Carassius auratus、似鳊Pseudobrama simoni和翘嘴红鲌Erythroculter ilishaeformis，部分种类只在特定的河段有记录。北横引河各站点平均物种数、丰度和生物量均高于南横引河和竖河，但3类河道间不存在显著差异（P>0.05）；主要优势种鲫、翘嘴红鲌和似鳊平均体长均以北横引河为最大，且在南横引河与北横引河中的个体体长均存在极显著差异（P<0.01）。聚类和排序分析结果表明，北横引河和南横引河鱼类组成差异较大，而竖河介于两者之间。相似性分析的结果也表明，南、北横引河鱼类群落结构差异极显著（R=0.524，P=0.008），且这两组间鱼类种类组成的平均相异性最高，为43.92%，造成两组间差异的主要物种有10种（贡献率均大于5%）。综合来看，崇明岛内河鱼类群落组成与分布特征不同于一般的内陆河流，而具有河口型岛屿的特点。未来需要在长期监测基础上，综合多种因素，对崇明岛内河鱼类组成、分布、变化趋势及内在机理开展系统研究。 Abstract:Chongming Island is the largest estuarine alluvial island in the world. It has a well-developed river network. In June 2018, trawl surveys on the fish were carried out in 16 fixed sampling sites in the representative rivers of Chongming Island, including the Nanheng Canal, Beiheng Canal and also the vertical canals Miaogang, Baozhengang, and Bayaogang. The composition and distribution characteristics of the fish communities in summer were analyzed based on these surveys. A total of 4417 specimens belonging to 6 orders, 9 families and 30 species of the fishes were collected in the surveys. Among them, 27 species were freshwater fish, 2 species were migratory fish and 1 species was coastal marine fish. And 20, 17 and 18 fish species were recorded in the Beiheng Canal, Nanheng Canal, and the vertical canals respectively. The characteristics of the fish assemblages, including the dominant species, varied among the rivers. The common dominant species of all the rivers were Carassius auratus, Pseudogramma simoni and Erythroculter ilishaeformis. Some species were only recorded in some specific reaches. The average species number, abundance and biomass of the fish in the Beiheng Canal were much higher than those in the Nanheng Canal and also the vertical canals, but there was no significant difference among the rivers (P>0.05). The average body length of major dominant species, Carassius auratus, Pseudogramma simoni and Erythroculter ilishaeformis in the Beiheng Canal were also the largest, and there was a very significant difference in individual body length between the Nanheng Canal and the Beiheng Canal (P<0.01). Cluster and nMDS analysis showed the greater difference between the fish assemblages in the Beiheng Canal and the Nanheng Canal, while those in the vertical canals were between these two. The results of ANOSIM also showed that the difference of the fish community structure between the Beiheng Canal and the Nanheng Canal was extremely significant (R=0.524, P=0.008), the average dissimilarity between these two groups appeared to be the highest at 43.92%, and there were 10 main species causing such difference (contribution rate was greater than 5%).In general, we found out that the community composition and distribution characteristics of the fish assemblages in the rivers of Chongming Island were different from those of general inland rivers, while had some characteristics of the estuarine islands. In the future, comprehensive studies on the community composition, distribution characteristics, developing trends and the corresponding mechanisms of the fishes in the rivers of Chongming Island should be carried out based on the long term monitoring. 参考文献 相似文献 引证文献

A multi-pollutant methodology to locate a single air quality monitoring station in small and medium-size urban areas

Air quality management is underpinned by continuous measurements of concentrations of target air pollutants in monitoring stations. Although many approaches for optimizing the number and location of air quality monitoring stations are described in the literature, these are usually focused on dense networks. However, there are small and medium-size urban areas that only require one monitoring station but also suffer from severe air pollution. Given that target pollutants are usually measured at the same sampling points; it is necessary to develop a methodology to determine the optimal location of the single station. In this paper, such a methodology is proposed based on maximizing an objective function, that balances between different pollutants measured in the network. The methodology is applied to a set of data available for the city of Cartagena, in southeast Spain. A sensitivity analysis reveals that 2 small areas of the studied city account for 80% of the optimal potential locations, which makes them ideal candidates for setting up the monitoring station. The methodology is easy to implement, robust and supports the decision-making process regarding the siting of fixed sampling sites.

Highly resolved spatiotemporal simulations for exploring mixed fishery dynamics

To understand how data resolution impacts inference on mixed fisheries interactions we developed a highly resolved spatiotemporal discrete-event simulation model MixFishSim incorporating: i) delay-difference population dynamics, ii) population movement using Gaussian Random Fields to simulate patchy, heterogeneously distributed and moving fish populations, and iii) fishery dynamics for multiple fleet characteristics based on population targeting under an explore-exploit strategy. We applied MixFishSim to infer community structure when using data generated from: commercial catch, a fixed-site sampling survey design and the true (simulated) underlying populations. In doing so we thereby establish the potential limitations of fishery-dependent data in providing a robust characterisation of spatiotemporal distributions. Different spatial patterns were evident and the effectiveness of a simulated spatial closure was reduced when data were aggregated across larger spatial areas. The simulated area closure showed that aggregation across time periods has less of a negative impact on the closure success than aggregation over space. While not as effective as when based on the true population, closures based on high catch rates observed in commercial data were still able to reduce fishing on a protected species. Our framework allows users to explore the assumptions in modelling observational data and evaluate the underlying dynamics of such approaches at fine spatial and temporal resolutions. From our application we conclude that commercial data, while containing bias, provides a useful tool for managing catches in mixed fisheries if applied at the correct spatiotemporal scale.

Seasonality of the dinoflagellate Amphidinium cf. carterae (Dinophyceae: Amphidiniales) in Bahía de la Paz, Gulf of California

Monthly phytoplankton samples were collected from January 2013 to December 2015 at a fixed sampling site in Bahía de La Paz, Gulf of California. During this study 26 samplings were Amphidinium cf. carterae positive. The highest densities of A. cf. carterae (754.2 × 103 to 1022.4 × 103 cells L−1) were recorded during a bloom detected in January 2015 when water temperatures were 20–22 °C. This dinoflagellate showed a well-marked seasonal variation, being found mainly from November to April. Blooms of the species were linked to the upwelled water due to the northwesterly wind. Cysts surrounded by a mucilaginous membrane of A. cf. carterae were found. We also observed these hyaline cysts inside zooplankton fecal pellets. Other benthic/tychoplanktonic dinoflagellates and diatoms, including some potentially toxic species were also found. The occurrence of blooms of A. cf. carterae in Bahía de La Paz could represent a risk for aquaculture activities and human health.

Over 50 years of fish community monitoring in Illinois’ large rivers: The evolution of methods used by the Illinois Natural History Survey’s Long-term Survey and Assessment of Large-River Fishes in Illinois

This document describes the methodological evolution of the Long-Term Illinois Rivers Fish Population Monitoring Program since its inception. The principal changes include a shift from fixed-site sampling to stratified random sampling at the reach scale to benefit statistical robustness and a concurrent shift from AC electrofishing to pulsed-DC electrofishing to increase the breadth of the diversity and size classes of fishes encountered. These changes in methodology were implemented during the 2016 field season and are based on quantitative assessments of program data and other results from recent peer-reviewed publications. These refinements will likely improve the program’s ability to detect and describe patterns and trends in the fish assemblages of the Illinois River and other large rivers of Illinois and the Midwest.

Representation of the Pacific Arctic seabird community within the Distributed Biological Observatory array, 2007–2015

An array of eight Distributed Biological Observatory (DBO) sites serve as long-term monitoring areas for three geographic regions: the northern Bering, eastern Chukchi, and Beaufort seas. The locations of the DBO sites were largely determined based on abundance and diversity of benthic invertebrates. It is not clear how well these fixed sampling sites can detect changes in processes and populations that operate over spatial scales that are 1–3 orders of magnitude greater than the areas sampled by the DBO sites. In this paper, we examine whether the DBO array provides a reasonable method by which to describe and monitor the distribution and community composition of seabirds in the eastern Pacific Arctic, and if it captures areas of high seabird abundance. We used vessel-based survey data totaling ∼115,860 km of transects within the study area from July–October 2007–2015. We compared species richness, diversity, abundance, and community composition of seabirds among DBO sites and to the broader geographic regions. In general, the avifauna of DBO sites were representative of their respective surrounding region, although sampling effort in the Beaufort was limited. Species richness (totaling 63 species) was highest in the Bering region and lowest in the Beaufort region. Species diversity indices were similar among DBO sites and regions, except for exceptionally low diversity in the two easternmost DBO sites of the Beaufort region. Total seabird abundance was highest in and near Bering Strait, and dropped abruptly northward and eastward of Point Barrow. We used K-means cluster analysis to identify six community types across the entire study area, with five community types identified as having at least one numerically dominant species, and one community type defined by very low densities of a variety of species. Several community types were associated with major current systems (e.g. Anadyr Current, Alaska Coastal Current), and for two community types, breeding colony locations were also influential. Short-tailed shearwaters were the most abundant species in five of the eight DBO sites, and they were the numerically dominant species in a community that was represented from DBO 1 through DBO 6. Overall, variance in abundance was much greater by DBO site (or region) than by year for total birds and for seven of eleven taxa. Taxa with greater interannual variance than spatial variance were shearwaters and phalaropes (among regions), and murrelets (among DBO sites), all of which are late summer migrants to the study area, and glaucous gulls, a circumpolar species. The consistency in species’ abundance by site indicates that DBO sites will be useful for monitoring seabirds in each region. As an array, the DBO sites captured major hotspots of seabird abundance as well as the seabird communities, except for the fulmar-dominated community in the outer Bering Shelf. However, all DBO sites will need to be surveyed to capture the full range of seabird communities in this study area. The Beaufort DBO sites require more survey coverage than currently achieved to fully evaluate their effectiveness to monitor changes in seabirds for that region.

A comparison between fixed and random sampling of a low density spotted bass population in a large river

Characterizing the structure of riverine fish populations that are patchily distributed and at low densities is often difficult. Due to the wide distribution but low abundance of Spotted Bass, Micropterus punctulatus, throughout the lower Wabash River (LWR), captures from fixed and random sampling designs were compared to assess their performance in determining relative abundance and size structure. The LWR is monitored using both sampling regimes—the Long Term Electrofishing Program monitors community assemblages uses a stratified-random sampling, whereas the Illinois Department of Natural Resources monitors the fish community using a fixed-sampling design. Mean CPUE was significantly higher for fixed site sampling compared to random sites. However, the size structure of Spotted Bass sampled by each design were similar. These results suggest random-sampling designs should be used when monitoring low density populations of fishes in large riverine systems because this method provides the greatest spatial coverage of habitats, evaluates heterogeneity in distribution, and provides a representative measure of abundance throughout an entire aquatic system. In situations where size distribution or temporal trends are the only goal, fixed site sampling would be sufficient.

Collapse of macrophytic communities in a eutrophicated coastal lagoon.

Collapse of macrophytic communities in a eutrophicated coastal lagoon.

Distribution of functional groups of phytoplankton in the euphotic zone during an annual cycle in Bahía de La Paz, Gulf of California

Irradiance plays an important role in the distribution of functional groups of phytoplankton in the euphotic zone. To characterize the environmental variability of the euphotic zone (in three levels of irradiance, 100, 10 and 1%) and its influence on the functional groups, the latter were studied. Similarly, changes in the structure of the microphytoplankton functional groups were determined as a response to the variability of hydrological conditions. Thus, results of the vertical distribution of microphytoplankton at three light quantity levels during an annual cycle (June 2000-June 2001) at a fixed sampling site in Bahí­a de La Paz (24° 21.284 N; 110° 26.294 W) are presented. A total of 62 taxa were identified: 45 diatom species (72.58%), 11 dinoflagellate species (17.74%), 3 species of silicoflagellates (4.83%), 1 ciliate species (1.61%), 1 cyanophyte (1.61%), and 1 coccolithophorid (1.61%). A higher abundance of diatoms was observed in the uppermost surface layer, while dinoflagellates were more abundant at the 10% irradiance level of the euphotic zone lower limit; silicoflagellates, although in a lesser magnitude, associated with the limit of the euphotic zone. Diatoms usually dominated, followed by dinoflagellates; this occurred at all three light quantity levels of the euphotic zone through the year. Environmental conditions during the warm period (&gt;23°C) favored dinoflagellates; during the water-column homogenization period (December-April) conditions favored heterotrophic Protoperidinium species inhabiting the layers above or below the thermocline. However, the integration of species assemblages during the period of the homogenous water column was not clear due to mixing of different phytoplankton assemblages coming from different depth levels.

长江口九段沙湿地海三棱藨草生物量分配特征及其影响因子

PDF HTML阅读 XML下载 导出引用 引用提醒 长江口九段沙湿地海三棱藨草生物量分配特征及其影响因子 DOI: 10.5846/stxb201710241903 作者: 作者单位: 华东师范大学,华东师范大学 作者简介: 通讯作者: 中图分类号: 基金项目: 上海市科委自然科学基金（15ZR1411200） Biomass allocation characteristics of Scirpus mariqueter and corresponding influencing factors in Jiuduansha Shoals of the Yangtze Estuary Author: Affiliation: East China Normal University,East China Normal University Fund Project: the Natural Science Foundation of Shanghai, China 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:海三棱藨草（Scirpus mariqueter）为长江河口盐沼湿地先锋植物。以长江口九段沙湿地为主要研究区域，在江亚南沙、上沙、中下沙等不同区域设置固定站点，进行植被和环境因子的取样调研，分析研究了海三棱藨草的生物量分配特征及其主要影响因子，以期为海三棱藨草的培育与恢复、盐沼湿地生态系统的保护与利用提供科学依据。结果表明：（1）不同站点海三棱藨草的茎基高度、球茎生物量占比、根茎与球茎之比均不存在显著差异（P > 0.05），而植株密度、植株高度、根茎生物量占比、果实生物量占比、茎叶生物量占比、须根生物量占比、果实与根茎之比、果实与球茎之比在不同站点间存在显著差异（P < 0.05）；（2）不同站点的沉积物电导率、盐度、容积密度（5-10、25-30 cm土层）、总碳含量（10-15、20-25、25-30 cm土层）、总氮含量（5-10 cm土层）存在显著差异（P < 0.05）；（3）海三棱藨草的果实与根茎的生物量之比和沉积物5-10、25-30 cm总碳含量，0-5、5-10 cm总氮含量，0-5 cm容积密度，茎基高度6种因子的组合存在极显著相关（P < 0.01）；而其他生物量分配指标与本文涉及到的环境因子、植物表形参数均不存在显著相关性（P > 0.05）。海三棱藨草生物量分配特征是其自身生长特征与环境因子综合作用的结果。在今后的研究中需拓展生境因子涵盖范围，深入分析多因子综合作用对海三棱藨草生物量分配特征的影响。 Abstract:Scirpus mariqueter is a typical pioneer plant in the salt marshes of the Yangtze Estuary. A study on the morphological and biomass allocation characteristics, as well as environmental factors, of Scirpus mariqueter were carried out in fixed sampling sites in the Jiuduansha Shoals of the Yangtze Estuary. We aim to provide the scientific basis for the cultivation and restoration of Scirpus mariqueter and the utilization and protection of salt marsh ecosystems. The results showed the following:(1) among the different sites, the stembase height, corm biomass allocation rate, and ratio of rhizome to corm biomass did not show a significant difference (P > 0.05), while the shoot height, shoot density, rhizome allocation rate, fruit allocation rate, shoot biomass allocation rate, root biomass allocation rate, ratio of fruit to corm biomass, and ratio of fruit to rhizome biomass varied significantly (P < 0.05); (2) the sediment salinity, electroconductibility, bulk density (0-5 cm, 25-30 cm), total carbon content (10-15 cm, 20-25 cm, 25-30 cm), and total nitrogen content (5-10 cm) varied significantly among sites (P < 0.05); (3) only the combination of six factors, including the bulk density (0-5 cm), total carbon content (5-10 cm, 25-30 cm), total nitrogen content (0-5 cm, 5-10 cm) of the sediment, and stembase height of the plant had significant effects on the ratio of fruit to rhizome biomass of Scirpus mariqueter (P < 0.01), but the other environmental factors as well as plant morphological parameters did not show significant correlations with other biomass allocation indices. The biomass allocation characteristics of Scirpus mariqueter were the result of comprehensive effects of the plant growth characteristics and environmental factors. More factors should be included in further studies to reveal the synthetic effects of different factors on the biomass allocation of Scirpus mariqueter. 参考文献 相似文献 引证文献

Sampling designs for contaminant temporal trend analyses using sedentary species exemplified by the snails Bellamya aeruginosa and Viviparus viviparus

Environmental monitoring typically assumes samples and sampling activities to be representative of the population being studied. Given a limited budget, an appropriate sampling strategy is essential to support detecting temporal trends of contaminants. In the present study, based on real chemical analysis data on polybrominated diphenyl ethers in snails collected from five subsites in Tianmu Lake, computer simulation is performed to evaluate three sampling strategies by the estimation of required sample size, to reach a detection of an annual change of 5% with a statistical power of 80% and 90% with a significant level of 5%. The results showed that sampling from an arbitrarily selected sampling spot is the worst strategy, requiring much more individual analyses to achieve the above mentioned criteria compared with the other two approaches. A fixed sampling site requires the lowest sample size but may not be representative for the intended study object e.g. a lake and is also sensitive to changes of that particular sampling site. In contrast, sampling at multiple sites along the shore each year, and using pooled samples when the cost to collect and prepare individual specimens are much lower than the cost for chemical analysis, would be the most robust and cost efficient strategy in the long run. Using statistical power as criterion, the results demonstrated quantitatively the consequences of various sampling strategies, and could guide users with respect of required sample sizes depending on sampling design for long term monitoring programs.

Observations of particle extinction, PM2.5 mass concentration profile and flux in north China based on mobile lidar technique

Fine particle with diameter <2.5 μm (PM2.5) have important direct and indirect effects on human life and activities. However, the studies of fine particle were limited by the lack of monitoring data obtained with multiple fixed site sampling strategies. Mobile monitoring has provided a means for broad measurement of fine particles. In this research, the potential use of mobile lidar to map the distribution and transport of fine particles was discussed. The spatial and temporal distributions of particle extinction, PM2.5 mass concentration and regional transport flux of fine particle in the planetary boundary layer were investigated with the use of vehicle-based mobile lidar and wind field data from north China. Case studies under different pollution levels in Beijing were presented to evaluate the contribution of regional transport. A vehicle-based mobile lidar system was used to obtain the spatial and temporal distributions of particle extinction in the measurement route. Fixed point lidar and a particulate matter sampler were operated next to each other at the University of Chinese Academy of Science (UCAS) in Beijing to determine the relationship between the particle extinction coefficient and PM2.5 mass concentration. The correlation coefficient (R2) between the particle extinction coefficient and PM2.5 mass concentration was found to be over 0.8 when relative humidity (RH) was less than 90%. A mesoscale meteorological model, the Weather Research and Forecasting (WRF) model, was used to obtain profiles of the horizontal wind speed, wind direction and relative humidity. A vehicle-based mobile lidar technique was applied to estimate transport flux based on the PM2.5 profile and vertical profile of wind data. This method was applicable when hygroscopic growth can be neglected (relatively humidity<90%). Southwest was found to be the main pathway of Beijing during the experiments.