Midwater ecology
Project Manager: Kim Reisenbichler
Lead Scientist: Bruce Robison

The long-term goal of MBARI’s midwater research program is to develop an ecological model of the natural communities that occupy the oceanic water column. In 2001 we began to shift the emphasis of our field work from mesopelagic animals in the upper 1000 m of the water column, to the bathypelagic species that live down to 4000 m. These animals have never been studied with the kind of technology that MBARI can bring to bear on this problem, and they represent the largest gap in our understanding of carbon flux through the oceanic water column.

Our preliminary deep dives this year revealed a rich and diverse bathypelagic fauna that contains a large number of unknown animals. We are learning which species are present, which are most important, their relative abundances, and which parts of the water column they inhabit. In years 2002 and 2003 we will make quantitative measurements to elucidate community structure, function, and dynamics, much as we have done with Ventana at shallower depths. This will allow us to determine the ecological links between Chavez’ upper water column studies, our mesopelagic studies, and Barry’s benthic community work.

Our work on mesopelagic animals is shifting from surveys to process studies. We will conduct laboratory studies to follow up on recent results, which indicate the ability of gelatinous animals to take up dissolved organic compounds from seawater. Laboratory work will also include oxygen consumption measurements of keystone species in order to determine their metabolic rates, which will allow us to factor energetics into the community model. 

We are working to develop two instruments for deep water applications; both are off-the-shelf technologies which we will adapt for our research. The first is a class of very small acoustic transmitters that we will implant in or on gelatinous animals so that we can track their movements over time. The second is an electromagnetic field sensor that we believe may provide a revolutionary new perspective on the midwater habitat. We plan to acquire commercial examples of these instruments and to test them in shallow water, then adapt them for use by ROVs and AUVs during years 2002 and 2003.