摘要
波罗的本海地表纹层沉积物的形成不断扩大的现象为我们评价过去40年里沉积物积累的年际变化增加了可能性。同一时期,在Gotska Sand(?)n我们连续记载了这个地区的风速和风向。在39km^2范围内,收集了55个岩心,从中选取了3个具有明显纹层的沉积物岩心,对它们的细微结构进行了研究,结果发现,干物质的年累积量和大风出现的频率正相关,风力达到14m/s时,两者关系为最佳。这证实了再次悬浮的沉积物在沉积物积累中占很大比重的观点,在115～145m深处收集的25个地表纹层的岩心,其沉积物积累的平均速率为2mm/a。我们对暴风雨发生的频率和沉积物沉积在10年间的变化都进行了观测,两者的变化可能不仅说明了沉积物及有关营养物和污染物的周转,而且还使我们能用沉积物岩心作为历史档案库来做一些解释。对所有岩心中已确定年代的沉积层进行水平方向的比较揭示了深水条件下物质变化的情况。最近,海底动物群再次大面积定居在水深102～125m范围内的现象说明,90年代早期的暴风雨事件极大地提高了氧的条件。尽管在我们的样品中纹层沉积物生物搅动的深度范围在0.5～5.5cm,但却造成了氧条件很早就已经提高了的假象。
The expanding occurrence of laminated surficial sediments in the Baltic proper has increased the possibilities to assess interannual variation in sediment accumulation over the past four decades. During the same period of time, wind speeds and wind directions in the area have been recorded continuously on Gotska Sandon. When studying the fine structure in three distinctly laminated sediment cores, selected from 55 cores collected within a 39 km2 area, annual dry matter accumulation was found to correlate positively with the frequency of high wind speeds, reaching an optimum at gale force≥14 m s-1. This confirms that resuspended sediments contribute significantly to the sediment accumulation, with a mean rate of 2 mm yr-1 for 25 surficially laminated cores collected at depths of 115-145 m. Decadal changes in both storm frequency and sediment deposition were observed, which may have implications not only for the turnover of sediments and associated nutrients and contaminants, but also for interpretations using sediment cores as historical archives. Horizontal comparison of dated sediment layers in all cores revealed a record of substantial changes in deep-water conditions. Recent recolonization of large areas by benthic fauna, within the depth of 102-125 m, suggests that storm events in the early 1990s are responsible for substantially improved oxygen conditions. Although, bioturbation of laminated sediments, with a depth range of 0.5-5.5 cm in our samples, creates a false picture of an earlier improvement.
