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831.
The influence of long emersion on biota, ammonium fluxes and nitrification in intertidal sediments of Marennes-Oléron Bay, France 总被引:2,自引:0,他引:2
Laima M Brossard D Sauriau PG Girard M Richard P Gouleau D Joassard L 《Marine environmental research》2002,53(4):381-402
A comparative study between waterlogged and reflooded intertidal sediments was undertaken in March and June 1999 through statistical analysis of selected sediment parameters (biota, salinity, O2, Eh), pool sizes and benthic fluxes of nutrients (NH4+, NO2-, NO3-) and nitrification rates. In March samples, absence of polychaetes and oligochaetes from upper sediment horizons were due to erosional events sweeping away surface sediments. Presence of richer annelid assemblages in June samples indicated more stable hydrodynamic conditions that favoured the development of benthic microalgae biofilms. Dewatering of sediments during a 3-day emersion period promoted a salinity rise on top layers, migration of pore water ions towards the sediment surface, and created sediment fissures that accelerated water exchange on reflooding. Reflooded and waterlogged sediment systems were comparable with respect to the release of NH4+ to overlying water but were different with respect to nitrification rates. Sediment-water NH4+ fluxes were higher (P = 0.011) in March (3.3 mmol m(-2) day(-1) compared to June (1.4 mmol m(-2) day(-1) due to higher macrofauna biomasses and lower benthic microalgae concentrations in March samples. Potential nitrification rates (range from 19 to 60 mmol NO3- (-2) day(-1)) were not statistically different between March and June. A thinner oxic layer in reflooded compared with waterlogged systems reflects a decrease of O2 diffusion into sediment at high salinities which resulted in the fall of the actual nitrification rates (P < 0.05). Our data suggest that long term dessication of intertidal sediments may depress the nitrification process at the ecosystem level. 相似文献
832.
南极西部埃尔斯沃思山脉罗斯造山运动的地层学证据:冈瓦纳古太平洋边缘的演化P.M.Goldstrand等冈瓦纳重建过程中存在着一个长期的疑问,即埃尔斯沃思山脉的古生代地层的明显整合与横贯南极山脉的大地构造史相矛盾,这两座山脉在中生代冈瓦纳分裂之前通常认... 相似文献
833.
印度洋马约特(Mayotte)礁过去34ka以来的海平面变化和δ ̄(18)O记录MichelColonna等很少有资料证明以冰期后时期珊瑚礁为依据的海平面曲线,只有一条过去17000多年的参考曲线取自巴巴多斯近海处区域上受晚第四纪隆起影响的化石礁。考... 相似文献
834.
Marin M Legros H Poret A Leboulenger F Le Foll F 《Marine environmental research》2004,58(2-5):209-213
Multi-drug resistance (MDR) in MCF7 breast cancer cells and multi-xenobiotic resistance (MXR) in mussel (Mytilus edulis) blood cells (MBC) are well known mechanisms that contribute to the decrease in intracellular concentrations of many unrelated but cytotoxic compounds. In the present work, we have carried out comparative investigations of the MDR/MXR protective mechanisms using a rapid colorimetric assay for cell viability and calcein accumulation for MDR/MXR activities. These studies were performed using cultured MCF7 and MBC before and after in vitro exposure to xenobiotics. Our results indicate that a 5-day exposure to doxorubicin or vincristine decreased calcein accumulation in MBC which is consistent with an induction of multi-xenobiotic resistance. The increase in calcein accumulation provoked by 1-h treatment with 50 microM verapamil was much lower in MBC when compared to the P-glycoprotein overexpressing MCF7 cell line. We conclude that such microplate assays could be used in primary cultures of MBC to estimate the effects of various chemicals on MXR activity. 相似文献
835.
弗拉斯-法门期(晚泥盆世)动物灭绝事件是显生宙五次主要生物事件中的一次,在此事件中,大约有21%的海洋生物科和50%的生物属消亡,低纬度热带生物礁生态系和浅水海洋动物所受影响最为严重,而高纬度生态系,深水生物和陆地动、植物群仅受到微弱影响,对于该事件的持续时期和最终原因存在广泛分岐。 相似文献
836.
837.
838.
Rebouças do Amaral MC de Freitas Rebelo M Torres JP Pfeiffer WC 《Marine environmental research》2005,59(4):277-285
In order to study Zn and Cd accumulation and depuration, a set of oysters, Crassostrea rhizophorae, were transplanted to a metal contaminated coastal lagoon and another one was harvested there and transplanted to a non-polluted site. C. rhizophorae oysters and Perna perna mussels native from both sites were collected in order to monitor variability of metal concentration in resident populations. After three months exposure, oysters transplanted to the polluted site accumulated fourfold Zn (307-1319 microgg(-1)) without reaching the concentration level of resident oysters (9770 microgg(-1)). Cadmium concentrations had a slight but significant decrease during the same period (1.25-0.54 microgg(-1)). Oysters transplanted to the non-polluted site, showed threefold Zn depuration (6727-2404 microgg(-1)), while Cd had no significant variation (0.90-1.45 microgg(-1)). Results showed that transplanted oysters do not reach heavy metal concentrations in indigenous populations suggesting transplanted organisms would be better used to evaluate bioavailability instead of environmental concentrations. 相似文献
840.
两种涡鞭毛藻生长特性的研究 总被引:4,自引:1,他引:4
运用单种培养的方法研究了分别于1987年和1989年采自葡萄牙沿海和德国湾的两种赤潮涡鞭毛藻Alexandrium lusitanicum(A.L.)和Y-100在不同光、温、盐条件下的生长特性,结果表明,在较低温度条件下,藻的生长在较低的光照强度时就显示了光饱和现象;在较高温条件下,藻的生长随光照增加而加快,两种藻生长的最适温度随光照强度增加而增加,在低于最适温度条件下生长速率都随温度升高而加快 相似文献