Ocean productivity: A personal perspective since the first Liege Colloquium

I briefly review the changing dominant research agenda in ocean productivity over the time since the first Liege Colloquium, 44 years ago, and coincidentally, about when I started in oceanography. I then consider two lingering issues, the depth of the ocean's productive layer and the dynamics of dissolved organic carbon. These two topics are united through respiration, the former concerning autotrophic respiration, and the latter heterotrophic respiration. (C) 2014 Elsevier B.V. All rights reserved.