Analysis of Phytoplankton Community Structure Using Similarity Indices: A New Methodology for Discriminating Among Eutrophication Levels in Coastal Marine Ecosystems

Nine similarity indices based on phytoplankton community structure were examined for their sensitivity to assess different levels of eutrophication. Two phytoplankton data sets, one from an open coastal system and one from a semi-enclosed gulf, associated with different nutrient dynamics and circulation patterns were used for evaluating the indices. The results have shown that similarity indices, measuring interspecific association and resemblance of phytoplankton communities between enriched areas and control sites, were effective for detecting spatial and temporal dissimilarities in coastal marine ecosystems. The structure of the oligotrophic habitat as a potential source of ambiguity for the results was discussed, whereas the validity ranges and the potential applicability of this method were deemed to be dependent on the size of the fraction of the common species among the samples, and the similarity of the classification patterns resulted from this subcategory and those extracted from the overall community data. Furthermore, the study provides a new technique based on the use of the “Box and Whisker Plot” designed to distinguish opportunistic and rare phytoplanktonic species. The similarity indices, applied solely to the dominant species abundance, were more sensitive to resolve eutrophic, mesotrophic and oligotrophic conditions. This procedure can be proposed as an effective methodology for water characterization and can also be used as a qualitative tracer for detecting renewal processes of coastal marine ecosystems.     

A critique of EPA's index of watershed indicators

Numerous indices have been developed to assess water quality and the impact of programs to improve quality. The Index of Watershed Indicators (IWI) is one such index created by the US Environmental Protection Agency to assess watershed vulnerability and condition in the United States. The credibility and applicability of subjective indices such as IWI depends upon their ability to withstand tests that challenge their internal consistency and interpretation. This paper critiques IWI on the basis of these tests and other considerations, and suggests that explicitly basing the index on multiattribute utility theory and methods could help resolve many of these difficulties.     

SIMULATED RELATIONSHIPS BETWEEN SPECTRAL REFLECTANCE,THERMAL EMISSIONS,AND EVAPOTRANSPIRATION OF A SOYBEAN CANOPY1

ABSTRACT: A canopy reflectance model is incorporated into a routine for simulating water and energy flows in the soil-plant-atmosphere system. The reflectance model is structured tocalculate canopy albedo throughout each simulation period and to determine spectral reflectances at a specified time during the day. Spectral vegetation indices are then calculated from the reflectances and related to the evapotranspiration and thermal response of the canopy. The canopy reflectance model is also used to establish the photo-sytheticaily active radiation load at various depths in the canopy. Stomatal resistances are calculated using these radiation values and integrated to give the minimum canopy resistance. Actual canopy resistance is obtained by adjusting minimum canopy resistance for environmental stresses such as leaf water potential and leaf temperature. Using data for a soybean canopy, canopy evapotranspiration and temperatures are simulated for a range of leaf area index values and compared with the corresponding spectral vegetation indices. The resuits indicate that the normalized difference spectral index has an inverse linear relationship with canopy temperature, concurring with results obtained from satellite observations. The possibility of using a spectral vegetation index and thermal observations together to parameterize surface moisture availability for evapotranspiration is considered.     

p-Cresol mineralization and bacterial population dynamics in a nitrifying sequential batch reactor

The ability of a nitrifying sludge to oxidize p-cresol was evaluated in a sequential batch reactor （SBR）. p-Cresol was first transformed to p-hydroxybenzaldehyde and p-hydroxybenzoate, which were later mineralized. The specific rates of p-cresol consumption increased throughout the cycles. The bacterial population dynamics were monitored by using denaturing gradient gel electrophoresis 0DGGE） and sequencing of DGGE fragments. The ability of the sludge to consume p-cresol and intermediates might be related to the presence of species such as Variouorax paradoxus and Thauera mechernichensis, p-Cresol （25 to 200 mg C/L） did not affect the nitrifying SBR performance （ammonium consumption efficiency and nitrate production yield were close to 100% and 1, respectively）. This may be related to the high stability observed in the nitrifying communities. It was shown that a nitrifying SBR may be a good alternative to eliminate simultaneously ammonium and p-cresol, maintaining stable the respiratory process as the bacterial community.     

Is urban development an urban river killer? A case study of Yongding Diversion Channel in Beijing, China

The high population and concrete environment alter urban areas by changing temperature, rainfall runoff, and water resource utilization activities. This study was conducted to investigate the water quality features of the Yongding Diversion Channel in Beijing, China, and its relationship with rainfall and urban development. Monthly water quality data were obtained from April to October of 2004 at monitoring sites of Sanjiadian, Gaojing, Luodaozhuang, and Yuyuangtan. The monthly water quality grades from 2007 to 2011 were also investigated and compared with those of other rivers. Dissolved oxygen and pH showed greater decreases after one or two moderate rainfall events than several light rainfall events. The potassium permanganate index （CODMn）, ammonia nitrogen （NH3-N） and total phosphorus （TP） increased more after several light rainfall events than after one or two moderate or heavy rainfall events. Pollutant concentrations （CODMn, NH3-N, TP） in downstream regions showed greater changes than those in upstream areas after heavy rainfall events. Intense human activities around the channel greatly influenced the water quality of the channel in rainy season because of runoff pollution; however, heavy rainfall had a strong dilution effect on the pollutant concentrations in rivers. Overall, urban development has obviously deteriorated the water quality of the Yongding Diversion Channel as indicated by an increase in the water quality index from 3.22 in 2008 to 4.55 in 2010. The Pearson correlation between monthly rainfall and water quality indices from 2007 to 2011 ranged from 0.1286 to 0.6968, generally becoming weaker as rainfall and rainfall runoff became more random and extreme.     

基于P-S-R模型的焦作市生态安全评价

文章基于焦作市社会、经济及生态环境现状分析,借鉴压力-状态-响应(P-S-R)模型,运用层次分析法构建一个涵盖指标层、因素层、准则层及目标层等4层次的城市生态安全评价指标体系。在用熵权法确定各指标权重的基础上,结合时间趋势法评价焦作市2001～2007年的生态安全状况。结果表明:2001～2003年间生态安全综合指数值分别为0.277 7、0.384 5、0.505 3,表示生态安全水平较低;2004～2007年间生态安全综合指数值在0.573 5～0.683 1之间,生态安全有所提高。整体来看,近些年来,焦作市的生态安全水平呈现不断好转态势。该研究可为了解焦作市生态安全现状,及其未来生态环境质量改善和生态安全规划管理提供依据。     

Estimation and validation of biomass of a mountainous agroecosystem by means of sampling,spectral data and QuickBird satellite image

Biomass estimation in agroecosystems (AESs) is important to understand their role in carbon exchange for a sustainable environment. We used field spectra and sampled biomass of an AES including cultivated and abandoned croplands to develop a simple biomass estimation model. The digital number (DN) of a QuickBird (QB) satellite image was converted to a reflectance factor using the dark object subtraction method and the spectral reflectance of asphalt. The relationship between the reflectance factor of field-based spectra and the QB image obtained in early July 2007 was insignificant in the blue (R ² = 0.15) and green (R ² = 0.18) bands but was significant (p < 0.05) in the red (R ² = 0.57) and near-infrared (NIR, R ² = 0.45) bands in the AES. Better correlations were obtained between field-based and QB-based vegetation indices (VIs). The best correlations were obtained with the normalized difference vegetation index (NDVI) (R ² = 0.97, p < 0.001) and the ratio vegetation index (RVI) (R ² = 0.99, p < 0.001). Biomass was significantly correlated with both field-based NDVI and RVI (R ² = 0.79 and 0.72, respectively, p < 0.001). Although RVI saturated at higher biomass densities (>600 g m^?2), NDVI showed a linear relationship. Other field-based VIs showed poorer correlations with biomass. The model was evaluated by incorporating it into high-resolution QB images to obtain the observed biomass. The relationship between field-estimated and QB-observed biomass appeared to be a one-to-one linear relationship (R ² = 0.79). Thus, models using field spectra and sampled biomass can be applied to QB images for remote estimation of biomass in an AES.     

历山山核桃群落物种多样性特征

采用Patrick指数、Simpson指数、Shannon指数、Pielou指数、Alatalo指数等5个多样性指数,结合TWINSPAN分类,研究历山自然保护区山核桃(Juglans mandshurica)群落的物种多样性与群落类型、结构及环境因子的关系.结果表明:TWINSPAN分类将35个样方分为7个群丛,各群丛的物种丰富度指数、多样性指数和均匀度指数之间存在差异,各群丛乔木层、灌木层和草本层之间的丰富度指数和均匀度指数也存在差异,山核桃群落物种多样性受其所处的坡向、坡度、土壤类型等物理微环境及群落物种组成、干扰等共同影响.方差分析结果表明:各群丛间丰富度指数、多样性指数和均匀度指数差异不显著,各群丛乔木层、灌木层和草本层之间的丰富度指数和均匀度指数也差异不显著,这说明山核桃群落生境异质性小,物种对地带性气候有相似的适应特征以及相似的资源利用方式.