Benthic foraminifera and accumulation rates in different time slices of sediment cores from the Equatorial Pacific

Surface productivity is correlated with the rate of accumulation of benthic foraminifera on the deep-sea floor. As a rule of thumb, for each 1 mg of organic carbon arriving at the sea floor, one benthic foram shell >150 µm is deposited. The correlation can be used to reconstruct organic flux to the sea floor in the past, and hence the productivity of past oceans. Applying the appropriate equations to box core data from the Ontong Java Plateau in the western equatorial Pacific, we found that productivity during the last glacial maximum exceeded present productivity by a factor of between 1.5 and 2.0, with intermediate values for the mid-transition period. Accumulation of benthic foraminifera was depressed on top of the plateau during the glacial and transitional period, presumably because increased winnowing removed part of the food supply.

海底沉积的底栖有孔虫积累速率与地表生产力密切相关。通常而言，每有1毫克有机碳抵达海底，便会沉积一个直径大于150微米的底栖有孔虫壳体。这一相关性可用于重建过去海底的有机物质通量，从而推断古代海洋的生产力。通过对西太平洋赤道附近的欧通加雅高原箱式岩芯数据应用相应方程，我们发现，在最后一个冰期峰值时期，生产力较当前水平高出1.5至2.0倍，而在过渡期中值。在冰川及过渡期间，高原顶部底栖有孔虫的积累量有所下降，这可能是由于风化作用加剧，导致部分食物链供应减少所致。