Changes in macroalgal communities in the vicinity of a Mediterranean sewage outfall after the setting up of a treatment plant

Benthic macroalgal communities of the upper rocky sublittoral were studied in 1995-1996 in the vicinity of the Marseille (Mediterranean, France) sewage outfall, 8 years after the setting up of a wastewater treatment plant and compared to a previous study carried out in 1972-1974. The number of taxa has increased, a clear stational and seasonal gradient of differentiation of the vegetation appeared, and a turf of ephemeral species is taking place of Corallina elongata at sites close to the outfall. These changes may be due to a decrease in pollutant load, the discharge of ferric chlorates used in the treatment process. However, the overall change is much less conspicuous than that described for deeper soft bottom communities, in particular the Cystoseira amantacea community is not still restored. Biological traits of this species (short distance dispersal) and the nature of most pollutants removed from the effluent (solids and organic matter) may explain this phenomenon.     

珊溪水库地震小震震源机制解特征研究

利用P波初动和直达P、S波最大速度振幅比联合求解小震震源机制的方法求出珊溪水库ML2.0以上地震的震源机制,得到了珊溪水库震源机制各参数时空特征如下:主压应力为SN向,主张应力为EW向,应力主要为水平应力,发震断层倾角较大且多为走滑断层。在个别4级左右地震前P轴方位都有偏离再恢复的现象。在北纬27.65°～27.69°间,P轴方位集中在0°±30°或者180°±30°,节面走向集中在45°±15°或者135°±15°。震源深度大于4km的地震倾角多集中在70°～90°度之间。