| 英文摘要: | Low oxygen levels in tropical oceans shape marine ecosystems and biogeochemistry, and climate change is expected to expand these regions. Now a study indicates that regional dynamics control tropical oxygen trends, bucking projected global reductions in ocean oxygen. The subsurface ocean in the eastern tropical Pacific contains a large volume of water with very low dissolved oxygen (O2) levels. Reduced O2 in the ocean can exclude fish and other marine life that need O2 for aerobic respiration and, at low enough O2 levels, even alter key pathways of microbial biogeochemical cycling1, 2, 3. Historical observations indicate that the size of oxygen minimum zones (OMZs) around the world are growing with time4, consistent with a global trend of ocean deoxygenation that has been linked to ocean warming and climate change2, 5. Writing in Science, Curtis Deutsch and colleagues6 argue the opposite, that the size of the eastern tropical North Pacific OMZ (Fig. 1) has been shrinking over a century timescale in response to weakening tropical trade winds and that this trend should continue in a future, warmer world.
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