The internal processes of Earth’s largest ecosystems have long been obscured by limited access to the ocean’s interior. As a consequence we know very little about the natural variability of oceanic communities at depths below the mixed layer. Understanding how climate change will affect the ocean is a key issue worldwide. As anthropogenic influences multiply and as multiple factors of change become interactive, it is increasingly important to know how oceanic communities respond to change. Whatever the causes of change, without a frame of reference it is very difficult to assess the consequences of change after the fact, much less predict in advance what is likely to happen.

MBARI’s midwater time series provides specific data to investigate the natural variability of oceanic communities at depths below the mixed layer. As an integral part of our Midwater Ecology program we have been conducting quantitative video transects of the local mesopelagic fauna, for the last twenty-five years. This is the only data set of its kind in the world and it is uniquely valuable as a tool for understanding the dynamics of midwater communities and of individual species. The data have been widely used in publications and dissertations. Continuing use for research, teaching, and conservation, both inside and outside MBARI, is expanding.