During the past 100 years or so, the ocean surface has become more acidic by 0.1 pH units and has warmed by 0.6¿C. In recent decades,temperature and salinity changes suggest modifications in ocean circulation and thus in the distribution of surface nutrients. Surface nutrients also are being modified by changes in fluvial supply and by changes in aeolian transport of nutrient-enriched dust. In addition, over-fishing modifies the predation on large zooplankton by small fish and could have topdown effects on the lower food web. These changes affect marine ecosystems in ways that are neither well understood nor quantified.