Effects of nutrient enrichment derived from fish farming activities on macroinvertebrate assemblages in a subtropical region of Hong Kong     

Gao QF  Cheung KL  Cheung SG  Shin PK 《Marine pollution bulletin》2005,51(8-12):994-1002

To study the correlation between nutrient enrichment derived from fish farming activities and changes in macrobenthic assemblages, a one-year field study was conducted in Kau Sai Bay marine fish culture zone of Hong Kong. Bimonthly sediment samples were collected at six stations: two at the fish cages, two near the boundary of the fish culture area, and two reference sites further away from the culture area. Sediment physico-chemical characteristics in terms of silt/clay fraction, moisture content, total organic carbon (TOC), total Kjeldahl nitrogen (TKN) and total phosphorus (TP) were analyzed. The macrobenthos (>0.5 mm) present in the sediment were sorted, identified and enumerated. On average, TOC, TKN and TP levels at the fish cage stations were 82.8%, 128.5% and 1315.7% higher than those at the reference stations, respectively. As a result, the N:P molar ratio was greatly reduced from 8.75 at the reference stations to 1.83 at the fish cage stations. Univariate and multivariate analyses revealed that diversity of macrofauna was significantly reduced and community structure differed at the fish cage stations relative to the reference sites. The intermediary stations near the fish culture area showed a transitional state of disturbance. Faunal diversity was negatively correlated with nutrient level, reflecting the adverse impacts of nutrient enrichment derived from fish farming activities on the benthic assemblages. Whilst in subtropical Asia-Pacific trash fish is the major feed for fish culture resulting in a higher nutrient loading and nutrient ratio accumulated in the sediment beneath the fish rafts, the effects of nutrient enrichment on macrobenthic assemblages are comparable to that in temperate waters owing to relatively high sediment metabolism rate and smaller fish culture scale in Hong Kong.  相似文献   

化学风化作用中的稀土元素行为及其影响因素   总被引：22，自引：0，他引：22  

马英军  霍润科  徐志方  张辉  刘丛强 《地球科学进展》2004,19(1):87-094

地表风化作用长期以来一直是地球和环境科学研究的焦点问题。风化作用中微量元素地球化学行为的研究不但有助于对一系列全球性问题的认识和理解,而且有助于许多与人类生存密切相关的环境问题的解决。系统总结了近年来国内外在风化作用中的稀土元素地球化学研究领域的主要内容和最新进展,着重介绍了风化壳中稀土元素的分布特征、Ce异常成因、稀土元素的赋存状态和迁移方式、影响稀土元素分布和循环的主要因素,以及风化作用稀土元素地球化学的主要研究方法。最后,分析指出有机质和微生物作用对稀土行为的影响是未来的重要研究方向。  相似文献   

Variations of foliar carbon isotope discrimination and nutrient concentrations in Artemisia ordosica and Caragana korshinskii at the southeastern margin of China’s Tengger Desert   总被引：1，自引：0，他引：1  

Liangju Zhao  Honglang Xiao  Xiaohong Liu 《Environmental Geology》2006,50(2):285-294

Seasonal variations in foliar stable carbon isotope discrimination (Δ) of Artemisia ordosica and Caragana korshinskii and correlations of foliar Δ with N, P, and K concentrations were studied under different planting regimes at the southeastern margin of China’s Tengger Desert. Foliar Δ, N, P, and K concentrations and the correlations of Δ with N, P, and K differed between the species and planting regimes. Foliar Δ, P and K concentrations in A. ordosica were markedly higher than in C. korshinskii, while foliar N concentrations in C. korshinskii was significantly higher than in A. ordosica. There were no significant differences in N, P, and K concentrations in C. korshinskii between planting regimes, but foliar Δ was significantly increased after June in mixed-species planting. In A. ordosica foliar N concentrations in mixed-species planting and foliar Δ in single-species planting were significantly higher than those of corresponding planting regimes. According to water-use efficiency (WUE) calculated based on foliar Δ, and on N, P, and K concentrations, C. korshinskii’s survival may profit from its higher WUE, whereas A. ordosica can avoid drought damage by its higher P and K concentrations in leaves in arid or semi-arid environments. The complex correlations of foliar Δ with foliar N, P and K suggested that water in C. korshinskii and water and P nutrition in A. ordosica were the key factors limiting their growth.  相似文献   

Suspended basaltic glass–seawater interactions     

Matthildur B. Stefnsdttir  Sigurdur R. Gíslason 《Journal of Geochemical Exploration》2006,88(1-3):332

The objective of this study was to quantify by experiments the initial seawater–suspended basaltic glass interactions following the 1996 outburst flood from the Vatnajökull glacier, Iceland. The altered basaltic glass dissolved in seawater as recorded by the Si release from the glass. The dissolved concentrations of Na, Ca, Si, Ba, Cd, Co, Cu, Hg, Mn, Ni and total dissolved inorganic N increased with time but the concentrations of Mg, K, S, Sr, Fe, Pb and Zn decreased. Calculated 1 to 10 day fluxes for Si range from 38,000 tons/day to 70,000 tons/10 days. The fluxes for other major elements are more uncertain, but the positive flux (release from suspended matter to seawater) of Ca and Na, and negative flux of Mg, K and S are greater than the Si flux.  相似文献   

Studies on the transfer of mineral nutrients from feed, water, soil and plants to buffaloes under arid environments     

M.Y. Ashraf  A. Khan  M. Ashraf  S. Zafar 《Journal of Arid Environments》2006,65(4):632-643

Studies were conducted at a Livestock Farm in an arid region of Pakistan, to determine the uptake of mineral nutrients from the food of buffaloes. Samples of feed, water, forage, soil as well as blood, milk, urine, and faeces of the animals were collected and analysed for K⁺, Ca²⁺, and Fe²⁺ during summer and winter. The results showed that the concentrations of K⁺ and Ca²⁺ in plants were low, whereas that of Fe²⁺ was high. In animals, K⁺ was not found in the milk in significant amounts, rather it was excreted in the urine. The calcium taken in by the animals was used for the synthesis of milk, as a result of which low Ca²⁺ concentrations were detected in urine. Mineral nutrient concentrations (K⁺ and Ca²⁺) in forage plants and water were lower than the optimum requirement of the animals, as a result of which blood plasma contained lower amounts of minerals (K⁺ and Fe²⁺) than that of the normal animals or critical limits. From the findings of the present study, it can be concluded that the buffaloes raised at the livestock farm had a severe deficiency of mineral nutrients, particularly K⁺ in lactating and Fe²⁺ in both lactating and non-lactating animals. Feed supplements, that can overcome these deficiencies, should be used for the optimum growth, milk production and resistance to diseases.  相似文献   

铁假说和HNLC海区的现场铁加富实验   总被引：3，自引：0，他引：3  

张武昌  孙松 《地球科学进展》2002,17(4):613-616

20世纪90年代,JohnMart in提出的"铁假说（ironhypothesis）"和以此为中心的海洋铁加富实验（ironenrichments）成为海洋科学领域最受瞩目的事件。"铁假说"的主要内容是：铁限制了HNLC海区中浮游生物的生产力,并进而影响了CO₂由海洋上层向深层的输出;如果在HNLC海区加入铁,就可以促进浮游植物的生长,消耗掉过剩的 N、P营养盐,加速C从海洋表层向深层输出,最终降低大气中CO₂含量,缓解温室效应。在赤道太平洋和南大洋进行的现场加富实验证明,加入铁以后,这些海区的浮游植物生物量增加,N、P等营养盐被消耗。但是,这些实验并没有降低大气中CO₂含量。铁假说只被证实了一半。  相似文献   

Submarine groundwater discharge enhances primary productivity in the Yellow Sea,China:Insight from the separation of fresh and recirculated components     

Jianan Liu  Jinzhou Du  Xueqing Yu 《地学前缘(英文版)》2021,12(6):76-89

Submarine groundwater discharge(SGD)is being increasingly recognized as a significant source of nutri-ent into coastal waters,and generally comprises two components:submarine fresh groundwater dis-charge(SFGD)and recirculated saline groundwater discharge(RSGD).The separate evaluation of SFGD and RSGD is extremely limited as compared to the conventional estimation of total SGD and associated nutrient fluxes,especially in marginal-scale regions.In this study,new high-resolution radium isotopes data in seawater and coastal groundwater enabled an estimation of SGD flux in a typical marginal sea of the Yellow Sea.By establishing 226Ra and 228Ra mass balance models,we obtained the SGD-derived radium fluxes,and then estimated the SFGD and RSGD fluxes through a two end-member model.The results showed that the total SGD flux into the Yellow Sea was equivalent to approximately 6.6 times the total freshwater discharge of surrounding rivers,and the SFGD flux accounted for only 5.2％-8.8％of the total SGD.Considering the nutrient concentrations in coastal fresh and saline groundwater,we obtained the dissolved inorganic nutrient fluxes(mmol m-2 yr-1)to be 52-353 for nitrogen(DIN),0.21-1.4 for phosphorus(DIP),34-226 for silicon(DSi)via SFGD,and 69-262 for DIN,1.0-3.9 for DIP,70-368 for DSi via RSGD,with the sum of nutrient fluxes equaling to(1.8-9.3)-fold,(1.3-5.6)-fold and(2.0-9.5)-fold of the riverine inputs.Compared to the conventional estimation of the total SGD flux,the nutrient fluxes derived from the separation of SFGD and RSGD were(1.6-2.1),(1.6-1.8)and(4.0-4.9)times lower for DIN,DIP and DSi,respectively,indicating that the estimates by separating SFGD and RSGD could be conservative and representative results of the Yellow Sea.Furthermore,we suggested that SGD played an important role in nutrient sources among all the traditional nutrient inputs sources,providing 15％-48％,33％-68％and 14％-43％of the total DIN,DIP and DSi input fluxes into the Yellow Sea,and the high nutrient stoichiometric ratios(i.e.,DIN/DIP)in SGD probably contributed to the increasing ratios in the Yellow Sea.In addition delivering large amounts of nutrient into the Yellow Sea,SGD would create primary productivity of 10-49,1.6-6.8 and 8.8-42 g C m-2 yr-1 based on N,P and Si,which were equivalent to 5.2％-27％,0.9％-3.7％and 4.7％-23％of the total primary productivity,respectively.In par-ticular,the SFGD-derived DIN flux can be converted to primary productivity of 4.2-28 g C m-2 yr-1 thus demonstrating the disproportionately large role of SFGD in ecological environment of the Yellow Sea rel-ative to its flux.Therefore,we conclude that SGD,particularly SFGD,plays an important role as a nutrient source for the Yellow Sea,and not only affects nutrient budgets and structures but also enhances the pri-mary productivity.  相似文献   

Impact of open-ocean convection on nutrients,phytoplankton biomass and activity     

《Deep Sea Research Part I: Oceanographic Research Papers》2014

We describe the impact of an open-ocean convection event on nutrient budgets, carbon budget, elemental stoichiometry, phytoplankton biomass and activity in the Northwestern Mediterranean Sea (NWM). In the convective episode examined here we estimated an input of nutrients to the surface layer of 7.0, 8.0 and 0.4×10⁸ mol of silicate, nitrate and phosphate, respectively. These quantities correspond to the annual nutrient input by river discharges and atmospheric depositions in the Gulf of Lion. Such nutrient input is sufficient to sustain new primary production from 46 to 63 g C m⁻² y⁻¹, which is the same order of magnitude found in the NWM open waters. Our results together with satellite data analysis, propose new scenarios that explain the origin of the spring phytoplankton bloom occurring in NWM.  相似文献   

The Chemistry of Niobium Mineralisation at Bayan Obo, Inner Mongolia, China: Constraints on the Hydrothermal Precipitation and Alteration of Nb-Minerals   总被引：1，自引：0，他引：1  

Martin SMITH  John SPRATT 《地质学报》2012,86(5):700-722

As well as world class Fe and REE resources the Bayan Obo mineral deposits also hosts significant niobium resources(estimated as 2.2 Mt Nb with an average grade of 0.13 wt% Nb).Niobium in this study is primarily hosted in aeschynite-(Ce) and(Nd),but with subsidiary amounts of pyrochlore,fergusonite-(Ce),fersmite and columbite.Here we report on the paragenetic and textural setting of aeschynite,pyrochlore and fergusonite in the main ore bodies and in a carbonatite dyke.Niobium in a carbonatite sample is hosted in a phase tentatively(due to significant Ca,Mn and Ti contents) identified as fergusonite-(Ce).Aeschynite occurs overgrowing foliation in banded ores,in fractures and vugs in aegirine-rich rocks and in calcite veins.The composition in all settings is similar,but some examples in banded ores develop significant zonation in Y,Th and the REE,inferred to relate to buffering of halogen acid species to low levels by dissolution and fluoritisation of calcite,and the preferential precipitation of LREE from solution due to lower mineral solubility products compared to the HREE.Although lower in total concentration the ratios of REE in pyrochlore are similar to those of aeschynite and suggest the same metal source.The crystallisation of pyrochlore probably relates to growth in paragenetic settings where carbonates had already been eliminated and hence the buffering of F-species activities in the hydrothermal fluid was reduced.Both aeschynite and pyrochlore show evidence of alteration.Primary alteration of aeschynite resulted in leaching of A-site cations(Ca,REE,Th) and Nb,addition of Fe,and ultimately replacement by Ba-Ti phases(baotite and bafertisite).Secondary,metamictisation enhanced,possibly supergene alteration of pyrochlore resulted in hydration,leaching of A-site cations leading to the development of lattice vacancies and increases in Si.The presence of hydrothermal Nb resources at Bayan Obo suggests there may be potential for further Nb discoveries in the area,whilst the trends in element mobility during alteration have significant implications for the utility of A-B oxides as components of materials for immobilisation of radionuclides.  相似文献   

Characterization of nutrients in the atmospheric wet and dry deposition observed at the two monitoring sites over Yellow Sea and East China Sea   总被引：5，自引：0，他引：5  

Guosen Zhang  Jing Zhang  Sumei Liu 《Journal of Atmospheric Chemistry》2007,57(1):41-57

To investigate the atmospheric deposition of nutrients into the coastal and shelf regions of the northwest Pacific Ocean, observation sites were established upon Qianliyan Island (within the Yellow Sea) and the Shengsi Archipelago (within the East China Sea), respectively. Nutrient concentrations, including , were determined in both aerosols and rainwater samples. The analytical results contain clear seasonal signatures, with high values during the dry season and low values during the rainy season. Similar trends are observed for deposition fluxes. The amount of wet deposition is greater than that of dry deposition for the studied nutrient species. The influence of meteorological factors such as rainfall means that samples from Qianliyan Island record higher nutrient values than those from Shengsi. Along with riverine inputs, atmospheric deposition plays an important role in determining the biogeochemistry of nutrient species in coastal and shelf oceans. An erratum to this article can be found at  相似文献