These areas have particularly low concentrations of iron, and oceanographers hypothesize that this shortage of iron prevents plankton from thriving.
这些地区的铁含量特别低，海洋学家推测，铁的缺乏阻碍了浮游生物的繁殖。
2
This idea was modified in the late twentieth century, when geologists and oceanographers examining oceanic sediment found fossil evidence of warming and cooling of the oceans.