The Earth's ocean is central to the conditions experienced on our planet, regulating its atmosphere, climate and biology. Recent evidence, however, suggests that the physical and chemical conditions within the ocean are changing in ways that are rapidly moving outside those experienced for millions of years with major changes to ocean temperature, acidity, sea ice extent, sea level, and storm intensity. These changes are impacting the biological components the ocean, including an array of important microbial systems. Observed changes so far include decreased ocean productivity, altered food web dynamics, declining abundances of habitat forming species such as oysters, mangroves and corals, species range shifts, and an increased incidence of disease and invasion by exotic species. These changes to the marine biosphere are also beginning to amplify changes within major nutrient cycles, adding to impacts driven by other human activities such as coastal land use and overfishing. As we continue to push carbon dioxide and other greenhouse gases into the atmosphere, there is also growing uncertainty as to the risks associated with passing non-linear triggers and tipping points. This talk will examine the totality of changes occurring in the world's oceans as result of anthropogenic climate change, and will explore the consequences for the biological systems that are otherwise crucial for healthy oceans and their many human dependents.