There’s oxygen in water. Most oceanic life depends on it. The oxygen is decreasing. In general, the ocean oxygen content has dropped about 2%. More startling is the 40% drop in the tropics in the last 50 years. One simple cause is rising ocean temperatures. Warmer water has more difficulty holding onto free oxygen. Hence, trouble in the tropics. A second cause is warming climate that melts glaciers producing a flood of freshwater to enter the oceans. The freshwater caps the salt water, reducing the opportunity for the ocean to absorb and redistribute captured atmospheric oxygen. Hence, areas in the arctic that are also losing oxygen. Many such consequences are only becoming apparent as we study climate change, especially interactions between effects that were previously studied independently. Unfortunately, few of these interactions are moderating the effects of pollution and global warming. We’re witnessing changes that are happening faster than we can study, and therefore adapt to them.