Yasuhara Moriaki, Cronin Thomas M
U.S. Geological Survey National Center, Mail Stop 926A, Reston, Virginia 20192, USA.
Ecology. 2008 Nov;89(11 Suppl):S53-65. doi: 10.1890/07-1021.1.
Ostracodes are small, bivalved crustaceans with the finest-scale fossil resolution of any metazoan, rivaled only by the fossil record of the protistan Foraminifera. This article presents a synthesis of the patterns and possible causes of alpha species diversity variation in benthic deep-sea ostracodes at drilling sites in the North Atlantic and Arctic Oceans. Taken together, these sites represent a period of great climatic variability covering the past three million years. Sediment cores taken from the Mid-Atlantic Ridge show a positive correlation between warm temperatures and high species diversity. These Mid-Atlantic Ridge cores, at the same latitude as northern Spain, show the same positive correlation during the last two glacial-interglacial cycles (200-0 ka [thousands of years ago]) as they do during the pre-glacial Pliocene 2.85-2.4 Ma (millions of years ago). This positive correlation is also found in Pliocene cores from the Rockall Plateau, at the same latitude as Ireland. During the last 200 thousand years, however, this correlation is reversed in cores taken from both the Rockall and Iceland Plateaus. The discovery of high diversity during colder periods in recent high-latitude Rockall and Iceland cores seems to be explained by spikes in diversity caused by ice-rafting events, which would not affect the lower-latitude Mid-Atlantic Ridge. The Heinrich ice-rafting events reduce North Atlantic surface temperatures and salinity every approximately 6-12 ka, dramatically decreasing surface productivity. This increase in diversity during Heinrich events may be explained either by a negative correlation between surface productivity and benthic diversity or by increase in diversity caused by moderate disturbance when ice rafted debris fall to the bottom of the ocean.
介形虫是小型双瓣甲壳类动物，其化石分辨率是所有后生动物中最精细的，只有原生生物有孔虫的化石记录能与之媲美。本文综合介绍了北大西洋和北冰洋钻探地点底栖深海介形虫α物种多样性变化的模式及可能原因。这些地点共同代表了过去300万年气候剧烈变化的一个时期。从中大西洋海脊采集的沉积物岩芯显示，温暖温度与高物种多样性之间存在正相关。这些与西班牙北部处于同一纬度的中大西洋海脊岩芯，在过去两个冰期 - 间冰期循环（200 - 0千年前）期间与在冰川期前的上新世285 - 240万年前一样，都呈现出相同的正相关。在与爱尔兰处于同一纬度的罗科尔高原的上新世岩芯中也发现了这种正相关。然而，在过去20万年里，从罗科尔和冰岛高原采集的岩芯中这种相关性却相反。近期高纬度罗科尔和冰岛岩芯中在较冷时期发现的高多样性，似乎可以用冰筏事件导致的多样性峰值来解释，而冰筏事件不会影响低纬度的中大西洋海脊。海因里希冰筏事件大约每6 - 12千年就会降低北大西洋的表面温度和盐度，显著降低表面生产力。海因里希事件期间多样性的增加，要么可以用表面生产力与底栖生物多样性之间的负相关来解释，要么可以用冰筏碎片落到海底时适度干扰导致的多样性增加来解释。
