Biotic variation in coastal water bodies in Sussex, England: Implications for saline lagoons     

Chris B. Joyce  Cristina Vina-Herbon  Daniel J. Metcalfe 《Estuarine, Coastal and Shelf Science》2005,65(4):633-644

Coastal water bodies are a heterogeneous resource typified by high spatial and temporal variability and threatened by anthropogenic impacts. This includes saline lagoons, which support a specialist biota and are a priority habitat for nature conservation. This paper describes the biotic variation in coastal water bodies in Sussex, England, in order to characterise the distinctiveness of the saline lagoon community and elucidate environmental factors that determine its distribution. Twenty-eight coastal water bodies were surveyed for their aquatic flora and invertebrate fauna and a suite of exploratory environmental variables compiled. Ordination and cluster analyses were used to examine patterns in community composition and relate these to environmental parameters. Biotic variation in the coastal water body resource was high. Salinity was the main environmental parameter explaining the regional distribution of taxa; freshwater and saline assemblages were evident and related to sea water ingress. Freshwater sites were indicated by the plant Myriophyllum spicatum and gastropod mollusc Lymnaea peregra, while more saline communities supported marine and brackish water taxa, notably a range of chlorophytic algae and the bivalve mollusc Cerastoderma glaucum. Site community differences were also related to bank slope and parameters describing habitat heterogeneity. A saline lagoon community was discerned within the matrix of biotic variation consisting of specialist lagoonal species with associated typically euryhaline taxa. For fauna, the latter were the molluscs Abra tenuis and Hydrobia ulvae, and the crustaceans Corophium volutator and Palaemonetes varians, and for flora they were the algae Ulva lactuca, Chaetomorpha mediterranea, Cladophora spp. and Enteromorpha intestinalis. One non-native polychaete species, Ficopomatus enigmaticus, also strongly influenced community structure within the lagoonal resource. The community was not well defined as specialist and associated taxa were distributed throughout the spectrum of sites surveyed. Implications for the identification and conservation of saline lagoons are discussed.  相似文献   

Characterisation of Heterotrophic Microorganisms Isolated form the "Grotta Azzura" of Cape Palinuro (Salerno, Italy)     

Francesco Canganella  Giovanna Bianconi  Agata Gambacorta  Chiaki Kato  Katsuyuki Uematsu 《Marine Ecology》2002,23(S1):1-10

Abstract. Hydrothermal vent ecosystems have been extensively investigated during the last 20 years; shallow water hot springs (typically found below 50 m depth) have also been studied, and from these ecosystems many thermophilic and hyperthermophilic organisms were isolated and described.
The submarine caves of Cape Palinuro were discovered long ago, but only during the last decades were geological and biological investigations carried out, yielding a large number of reports on this fascinating environment. During the last two years, several samples of water, mud, and/or bacterial mat were collected within the "Grotta Azzurra", and enrichment experiments were performed using peptone, starch, glucose or pullulan as main organic nutrients. Many heterotrophic strains were isolated and most of them grew optimally between 37 and 43 ° C with the addition of 0-2 % NaCl. Growth was usually observed between 10 and 50 ° C the range of growth pH was 4 to 9, and NaCl concentrations up to 10–12 % were tolerated in most cases.
The analysis of 16S rDNA performed with the most representative isolates showed a close phylogenetic relationship with the genera Bacillus, Vibrio, Citrobacter and Escherichia. Moreover, an isolate showing morphological and physiological similarities with the genus Enterococcus was characterised and taxonomically described based on the 16S rDNA sequence.  相似文献   

Do explicit criteria help in selecting indicators for ecosystem-based fisheries management?   总被引：1，自引：1，他引：1  

Rochet  Marie-Joelle; Rice  Jake C. 《ICES Journal of Marine Science》2005,62(3):528-539

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固城湖生物资源利用和富营养化控制的研究   总被引：7，自引：0，他引：7  

章宗涉  黄昌筑 《海洋与湖沼》1996,27(6):651-656

于１９８９－１９９２年通过野外调查、室内试验，池塘模拟和数学模型等方法。研究江苏省固城湖的理化，初级生产生物生长及其有关因子，水草、藻和鱼，蟹间的相互关系，以及水草渔业利用对水质的影响等。  相似文献   

Establishing habitat-specific indicator species in Tierra del Fuego with freshwater macroinvertebrates     

Christopher B. Anderson  Montana Johnson  María Eugenia Lopez 《新西兰海洋与淡水研究杂志》2018,52(1):145-154

As a tool to understand Tierra del Fuego’s basic ecology and detect changes due to human pressures, this study develops habitat bioindicators. We compared the freshwater benthic macroinvertebrates at 61 study sites in six habitat types: grassland streams, urbanised streams, forested streams, beaver ponds, lakes and peat bog ponds. Forty-nine taxa were identified; insects were the most diverse group. Beaver pond, lake and grassland stream assemblages were similar, as were those from lakes, grassland streams and peat bog ponds. Fourteen taxa were habitat-specific. In forests, these included mayfly scrapers (Andesiops, Meridialaris) and blackfly filterers (Gigantodax). In lakes, two copepod filterers were indicators, and in urban streams, one shredder (Aphroteniella) and three collector-gatherers (springtail, earthworm, aquatic worm). Predators (Corixa, Aeshna) were characteristic of peat bog ponds. Beaver ponds had no indicator species. Establishing links between species and ecosystems constitutes the beginning of a broader effort to understand anthropogenic impacts to Fuegian watersheds.  相似文献   

Drip irrigation enhances shallow groundwater contribution to crop water consumption in an arid area          下载免费PDF全文

Xingwang Wang  Zailin Huo  Huade Guan  Ping Guo  Zhongyi Qu 《水文研究》2018,32(6):747-758

Shallow groundwater plays a key role in agro‐hydrological processes of arid areas. Groundwater often supplies a necessary part of the water requirement of crops and surrounding native vegetation, such as groundwater‐dependent ecosystems. However, the impact of water‐saving irrigation on cropland water balance, such as the contribution of shallow groundwater to field evapotranspiration, requires further investigation. Increased understanding of quantitative evaluation of field‐scale water productivity under different irrigation methods aids policy and decision‐making. In this study, high‐resolution water table depth and soil water content in field maize were monitored under conditions of flood irrigation (FI) and drip irrigation (DI), respectively. Groundwater evapotranspiration (ET_g) was estimated by the combination of the water table fluctuation method and an empirical groundwater–soil–atmosphere continuum model. The results indicate that daily ET_g at different growth stages varies under the two irrigation methods. Between two consecutive irrigation events of the FI site, daily ET_g rate increases from zero to greater than that of the DI site. Maize under DI steadily consumes more groundwater than FI, accounting for 16.4% and 14.5% of ET_a, respectively. Overall, FI recharges groundwater, whereas DI extracts water from shallow groundwater. The yield under DI increases compared with that under FI, with less ET_a (526 mm) compared with FI (578 mm), and irrigation water productivity improves from 3.51 kg m^?3 (FI) to 4.58 kg m^?3 (DI) through reducing deep drainage and soil evaporation by DI. These results highlight the critical role of irrigation method and groundwater on crop water consumption and productivity. This study provides important information to aid the development of agricultural irrigation schemes in arid areas with shallow groundwater.  相似文献   

Multi‐model ensemble prediction of terrestrial evapotranspiration across north China using Bayesian model averaging          下载免费PDF全文

Gaofeng Zhu  Xin Li  Kun Zhang  Zhenyu Ding  Tuo Han  Jinzhu Ma  Chunlin Huang  Jianhua He  Ting Ma 《水文研究》2016,30(16):2861-2879

Using high‐quality dataset from 12 flux towers in north China, the performance of four evapotranspiration (ET) models and the multi‐model ensemble approaches including the simple averaging (SA) and Bayesian model average (BMA) were systematically evaluated in this study. The four models were the single‐layer Penman–Monteith (P–M) model, the two‐layer Shuttleworthe–Wallace (S–W) model, the advection–aridity (A–A) model, and a modified Priestley–Taylor (PT‐JPL). Based on the mean value of Taylor skill (S) and the regression slope between measured and simulated ET values across all sites, the order of overall performance of the individual models from the best to the worst were: S–W (0.88, 0.87), PT‐JPL (0.80, 1.17), P–M (0.63, 1.73) and A–A (0.60, 1.68) [statistics stated as (Taylor skill, regression slope)]. Here, all models used the same values of parameters, LAI and fractional vegetation cover as well as the forcing meteorological data. Thus, the differences in model performance were mainly attributed to errors in model structure. To the ensemble approach, the BMA method has the advantage of generating more skillful and reliable predictions than the SA scheme. However, successful implementation of BMA requires accurate estimates of its parameters, and some degradation in performance were observed when the BMA parameters generated from the training period were used for the validation period. Thus, it is necessary to explore the seasonal variations of the BMA parameters according the different growth stages. Finally, the optimal conditional density function of half‐hourly ET approximated well by the double‐exponential distribution. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

我国水产品市场状况分析     

车斌  孙琛 《广东海洋大学学报》2000,20(4):50-54

文章分析了我国水产品市场的基本状况 ,认为目前我国水产品市场品种丰富 ,价格稳定。究其原因 ,主要是水产品流通体制的改革 ,水产品市场的开放 ,科技贡献率的提高 ,政府在渔业发展方向上的战略性调整和水产品对外贸易的快速发展。文章针对现阶段我国水产品市场存在的问题 ,特别是渔业资源及其生态环境破坏的负面影响及解决办法做了有益的探讨  相似文献   

The use of regional and alluvial groundwater by riparian trees in the wet-dry tropics of northern Australia     

Caroline A. Canham  Clément Duvert  Leah S. Beesley  Michael M. Douglas  Samantha A. Setterfield  Fiona L. Freestone  Steven Clohessy  Robyn C. Loomes 《水文研究》2021,35(5):e14180

Riparian trees play a critical role in the ecological function of rivers, yet are threatened by anthropogenic change to the hydrological cycle. Identifying the sources of water used by riparian trees can inform sustainable water policy. We used isotopic analysis complemented by measurements of plant water relations to assess water sources for riparian trees at two sites with contrasting hydrogeological processes; one with an alluvial aquifer overlaying an aquitard, and one where fault-induced preferential pathways in the aquitard allowed the flow of deeper, older groundwater from a regional aquifer to the alluvium. At both sites, plant water potential, stomatal conductance, and plant water isotope composition in the xylem sap of riparian trees were collected from two landscape positions, the riverbank and floodplain. We used a Bayesian mixing model (MixSIAR) to assess differences in the proportion of water sources for sites and landscape positions. We found that xylem water isotope values differed between the two sites in line with their hydrogeological characteristics, with trees at the regional aquifer site using water sourced from the regional groundwater and trees at the site with only an alluvial aquifer present using a mixture of water sources, with no dominant source identified. Higher plant predawn water potential values at the regional site indicated greater water availability and support the inference that plants were using more groundwater at the regional site compared to the alluvial site. Trees closer to the river had higher isotope values, indicative of surficial water sources i.e. shallow soil water and river water. Our findings show that the water sources used by riparian trees reflect local hydrogeology and resource availability. Water managers should identify and protect plant water sources to ensure maintenance of riparian trees.  相似文献   

The influence of relative sediment supply on riverine habitat heterogeneity   总被引：1，自引：0，他引：1  

Sarah M. Yarnell  Jeffrey F. Mount  Eric W. Larsen 《Geomorphology》2006,80(3-4):310-324

The diversity of aquatic habitats in streams is linked to physical processes that act at various spatial and temporal scales. Two components of many that contribute to creating habitat heterogeneity in streams are the interaction between sediment supply and transport capacity and the presence of local in-stream structures, such as large woody debris and boulders. Data from previously published flume and field studies and a new field study on tributaries to the South Yuba River in Nevada County, California, USA, were used to evaluate the relationship between habitat heterogeneity, local in-stream structural features and relative sediment supply. Habitat heterogeneity was quantified using spatial heterogeneity measures from the field of landscape ecology. Relative sediment supply, as expressed by the sediment supply/transport capacity ratio, which controls channel morphology and substrate textures, two key physical habitat characteristics, was quantified using a dimensionless bedload transport ratio, q. Calculated q values were plotted against an ecologically meaningful heterogeneity index, Shannon's Diversity Index, measured for each study reach, as well as the percent area of in-stream structural elements. The results indicate two potential mechanisms for how relative sediment supply may drive geomorphic diversity in natural river systems at the reach scale. When less mobile structural elements form a small proportion of the reach landscape, the supply/capacity ratio dictates the range of sediment textures and geomorphic features observed within the reach. In these settings, channels with a moderate relative sediment supply exhibit the highest textural and geomorphic diversity. In contrast, when less mobile structural elements are abundant, forced local scour and deposition creates high habitat heterogeneity, even in the presence of high relative sediment supply.  相似文献