Trophic Assessment in Chinese coastal systems-review of methods and application to the Changjiang (Yangtze) Estuary and Jiaozhou Bay   总被引：3，自引：0，他引：3  

Yongjin Xiao  João G. Ferreira  Suzanne B. Bricker  João P. Nunes  Mingyuan Zhu  Xuelei Zhang 《Estuaries and Coasts》2007,30(6):901-918

Coastal eutrophication has become one of the main threats to Chinese coastal areas during the last two decades. High nutrient loads from human activities have modified the natural background water quality in coastal water bodies, resulting in a range of undesirable effects. There is a need to assess the eutrophic level in coastal systems and to identify the extent of this impact to guide development of appropriate management efforts. Traditional Chinese assessment methods are discussed and compared with other currently-used methods, such as the Oslo-Paris Convention for the Protection of the North Sea (OSPAR) Comprehensive Procedure and Assessment of Estuarine Trophic Status (ASSETS). The ASSETS method and two Chinese methods were tested on two Chinese systems: the Changjiang (Yangtze) Estuary and Jiaozhou Bay. ASSETS is process based, and uses a pressure-state-response model based on three main indices: Influencing Factors, Overall Eutrophic Condition, and Future Outlook. The traditional methods are based on a nutrient index. ASSETS was successfully applied to both systems, classifying the Changjiang Estuary as Bad (high eutrophication) and Jiaozhou Bay as High (low eutrophication). The traditional methods led to ambiguous results, particularly for Jiaozhou Bay, due to the high spatial variability of data and a failure to assess the role of shellfish aquaculture in nutrient control. An overview of the Chinese coastal zone identifies 50 estuaries and bays that should form part of a national assessment. A comparison of methods and results suggests that ASSETS is a promising tool for evaluating the eutrophication status of these systems.  相似文献   

A Note on Extension Variances in IR2     

Chadœuf  Joël  Moran  Chris  Goulard  Michel 《Mathematical Geosciences》1998,30(6):575-587

Matheron (1971) proposed an approximation of the extension variance in IR. We propose in this note an extension of this formula in IR ² , based on a MacLaurin formula. Its application is shown in an example, the estimation of the maximum depressional storage of a soil surface.  相似文献   

The 200 mJy Subsample at 1.4 GHz     

Mercedes Esteves Filho  Maria João Marchã 《Astrophysics and Space Science》1998,261(1-4):259-260

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Thermal alteration experiments on organic matter in recent marine sediment—II. Isoprenoids     

Raphael Ikan  Mary Jo Baedecker  Isaac R. Kaplan 《Geochimica et cosmochimica acta》1975,39(2):187-194

Several isoprenoid compounds were isolated from a heat-treated marine sediment in the southern California continental shelf (from Tanner Basin) which were not present in the original sediment. Among the compounds identified were: phytol, dihydrophytol, C₁₈-isoprenoid ketone, phytanic and pristanic acids, C₁₉- and C₂₀-monoolefins, and the alkanes 2,6,10-trimethylpentadecane, pristane and phytane. The significance and possible routes leading to these compounds is discussed.  相似文献   

Thermal alteration experiments on organic matter in recent marine sediment—III. Aliphatic and steroidal alcohols     

Raphael Ikan  Mary Jo Baedecker  Isaac R Kaplan 《Geochimica et cosmochimica acta》1975,39(2):195-203

Recent sediments from Tanner Basin (off southern California) and Bandaras Bay (in Gulf of California) have been analyzed for normal, isoprenoid and steroidal alcohols using chromatographic (column, GLC, TLC), and spectroscopic (u.v., i.r., MS) methods, prior to and after heat-treatment (from 65 to 150°C). Normal saturated alcohols (C₁₄-C₂₄) and monounsaturated alcohols (C₂₂-C₂₄) were identified, as well as the isoprenoid alcohols, phytol and dihydrophytol.Two series of sterols (Δ⁵ and Δ⁷) were found in Tanner Basin, and Δ⁵-sterols and triterpenes, in Bandaras Bay sediment. Sterols from both sediments contained the corresponding stanols.  相似文献   

Currents and sediment transport in the Mississippi Canyon and effects of Hurricane Georges     

Cheryl Burden Ross  Wilford D. Gardner  Mary Jo Richardson  Vernon L. Asper 《Continental Shelf Research》2009,29(11-12):1384-1396

The temporal variability in currents, temperature, and particulate matter concentration were measured in the Mississippi Canyon axis where the thalweg was 300 m deep from May–July and August–November 1998 using current meters, thermographs, a light-scattering sensor, and sediment traps. Canyon sediments were sampled by coring and observed using an ROV video camera. Currents in the upper Mississippi Canyon generally oscillated up/down canyon with diurnal periodicity and were bottom-intensified. Mean current speed at 3.5 mab was approximately 8 cm s^?1 during both deployments, reaching maximum speeds of over 50 cm s^?1 under normal conditions. Based on current velocities, critical bed shear stress for resuspension of canyon-floor sediments was exceeded about 30% of the time during both deployments. In late September, Hurricane Georges passed 150 km NE of the study site, significantly intensifying current velocities, bed shear stress, resuspension, trap fluxes and temperature fluctuations. As the hurricane passed, maximum current speed reached 68 cm^?s and temperature decreased ～7 °C in less than two hours. Critical bed shear stress for sediment resuspension was exceeded approximately 50% of the time during the five days of hurricane influence. Further evidence for sediment resuspension was the five-fold (and perhaps 70–130 fold) increase in trap fluxes and compositional similarities between canyon surface sediment and material collected by traps.  相似文献   

Concurrent imaging of chlorophyll fluorescence,Chlorophyll a content and green fluorescent proteins‐like proteins of symbiotic cnidarians          下载免费PDF全文

Miguel Costa Leal  Bruno Jesus  João Ezequiel  Ricardo Calado  Rui Jorge Miranda Rocha  Paulo Cartaxana  João Serôdio 《Marine Ecology》2015,36(3):572-584

Research on photosynthetic cnidarians has been mainly focused on the symbiosis established between the cnidarian host and its dinoflagellates endosymbionts from genus Symbiodinium. Despite the potential of imaging techniques for assessing the spatial distribution of key parameters of cnidarian photobiology, such as photochemical activity, chlorophyll a content or green fluorescent proteins (GFPs), to our best knowledge, no study has ever attempted to simultaneous map these three features. In this study, we developed a modified imaging pulse amplitude fluorometer by applying excitation light of different wavelengths and selectively detecting short spectral bands through bandpass filters. The imaging system was used to sequentially excite and quantify chlorophyll variable fluorescence (maximum quantum yield of photosystem II, F_v/F_m), Chl a content (normalized difference vegetation index) and relative content of GFPs. The spatial distribution of these photophysiological parameters was mapped both horizontally, across the surface of the soft corals Sarcophyton cf. glaucum and Sinularia flexibilis and the zoanthid Protopalythoa sp., and vertically, throughout a vertical section of S. cf. glaucum. Results showed bleached areas within each individual coral colony and registered photophysiological changes with S. cf. glaucum tissue depth. Analysis of Protopalythoa sp. polyps’ expansion revealed differential surface patterns of NDVI and GFP concentration, and a negative relation between these latter parameters within each polyp. This novel non‐invasive approach allowed a high‐resolution characterization of the spatial relationship between these key parameters through the analysis of image information on a pixel‐by‐pixel basis, which has great potential for investigating the physiological state of symbiotic associations.  相似文献   

On using a generalized linear model to downscale daily precipitation for the center of Portugal: an analysis of trends and extremes     

Mário Pulquério  Pedro Garrett  Filipe Duarte Santos  Maria João Cruz 《Theoretical and Applied Climatology》2015,120(1-2):147-158

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Sulfur isotope variations from orebody to hand-specimen scale at the Mežica lead–zinc deposit, Slovenia: a predominantly biogenic pattern     

Uroš Herlec  Jorge E. Spangenberg  Jošt V. Lavrič 《Mineralium Deposita》2010,45(6):531-547

The Mississippi Valley-type (MVT) Pb–Zn ore district at Mežica is hosted by Middle to Upper Triassic platform carbonate rocks in the Northern Karavanke/Drau Range geotectonic units of the Eastern Alps, northeastern Slovenia. The mineralization at Mežica covers an area of 64 km² with more than 350 orebodies and numerous galena and sphalerite occurrences, which formed epigenetically, both conformable and discordant to bedding. While knowledge on the style of mineralization has grown considerably, the origin of discordant mineralization is still debated. Sulfur stable isotope analyses of 149 sulfide samples from the different types of orebodies provide new insights on the genesis of these mineralizations and their relationship. Over the whole mining district, sphalerite and galena have δ ³⁴ S values in the range of –24.7 to –1.5‰ VCDT (–13.5 ± 5.0‰) and –24.7 to –1.4‰ (–10.7 ± 5.9‰), respectively. These values are in the range of the main MVT deposits of the Drau Range. All sulfide δ ³⁴ S values are negative within a broad range, with δ ³⁴ S _pyrite <δ ³⁴ S _sphalerite <δ ³⁴ S _galena for both conformable and discordant orebodies, indicating isotopically heterogeneous H₂S in the ore-forming fluids and precipitation of the sulfides at thermodynamic disequilibrium. This clearly supports that the main sulfide sulfur originates from bacterially mediated reduction (BSR) of Middle to Upper Triassic seawater sulfate or evaporite sulfate. Thermochemical sulfate reduction (TSR) by organic compounds contributed a minor amount of ³⁴S-enriched H₂S to the ore fluid. The variations of δ ³⁴ S values of galena and coarse-grained sphalerite at orefield scale are generally larger than the differences observed in single hand specimens. The progressively more negative δ ³⁴ S values with time along the different sphalerite generations are consistent with mixing of different H₂S sources, with a decreasing contribution of H₂S from regional TSR, and an increase from a local H₂S reservoir produced by BSR (i.e., sedimentary biogenic pyrite, organo-sulfur compounds). Galena in discordant ore (–11.9 to –1.7‰; –7.0 ± 2.7‰, n = 12) tends to be depleted in ³⁴ S compared with conformable ore (–24.7 to –2.8‰, –11.7 ± 6.2‰, n = 39). A similar trend is observed from fine-crystalline sphalerite I to coarse open-space filling sphalerite II. Some variation of the sulfide δ ³⁴ S values is attributed to the inherent variability of bacterial sulfate reduction, including metabolic recycling in a locally partially closed system and contribution of H₂S from hydrolysis of biogenic pyrite and thermal cracking of organo-sulfur compounds. The results suggest that the conformable orebodies originated by mixing of hydrothermal saline metal-rich fluid with H₂S-rich pore waters during late burial diagenesis, while the discordant orebodies formed by mobilization of the earlier conformable mineralization.  相似文献   

The Response of Estuarine Macrobenthic Communities to Natural- and Human-Induced Changes: Dynamics and Ecological Quality     

João Magalhães Neto  Heliana Teixeira  Joana Patrício  Alexandra Baeta  Helena Veríssimo  Rute Pinto  João Carlos Marques 《Estuaries and Coasts》2010,33(6):1327-1339

Anthropogenic activities are a disturbance factor of coastal systems and can be widely recognized as a major threat to the health of coastal systems. However, natural events cannot be disregarded from management issues because of their significant influence on the communities living in these areas. Based on long-term subtidal data from the Mondego Estuary (Portugal), the effects of natural events (e.g., floods and droughts) on macrobenthic communities were compared with the anthropogenic events. Sampling stations were grouped into characteristic zones (mouth, north arm, south arm) so the community dynamics of each of these estuarine areas could be followed over time. Environmental assessment was performed for stations using the Benthic Assessment Tool (BAT), and compared with the existing pressures. Human impacts persist over a number of years and gradually reduce ecosystem health, as discussed in the European Water Framework Directive. Paradoxically, natural events cause stronger impacts but are of a shorter duration, which allows for a faster recovery of macrobenthic communities. The study showed that caution should be taken when developing and implementing water policies so as not to disregard the importance of the different events (natural and human-caused) on the ecosystem health (e.g., community degradation and water quality and ecological quality status assessment).  相似文献