Lead Scientist: Bruce Robison
Project Manager: Kim Reisenbichler
The midwater ecology project focuses on three groups of gelatinous
animals: larvaceans, siphonophores, and hydromedusae. Filter-feeding larvaceans are the
principal consumers of particulate matter such as phytoplankton cells and marine snow at
mesopelagic depths down to 1,000 meters. Siphonophores and medusae are dominant
mesopelagic predators, feeding on a broad range of other species. Despite the importance
of these animals to the ecology of midwater communities, their fragile, gelatinous
structures make them nearly impossible to study by conventional methods. With the advent
of ROV-based in situ research, significant progress is now being made toward
assessing their ecological roles and measuring their contribution to midwater
As in 1999, we will continue to use ROV transects to make quantitative measurements of the vertical
distributions, abundances, and seasonal variations of these animal groups. In situ
observations will provide data on trophic (feeding) relationships and behavior patterns.
The collection of live specimens will provide material for stomach content analyses
and for laboratory studies on respiration and reproduction, and feeding, digestion and
assimilation. Each of these parameters is important for accurately modeling energy flow
through these fundamental links in the mesopelagic food web.
At depths between 650 and 850 meters, a pronounced oxygen-minimum layer constitutes the
physical and chemical lower boundary of the mesopelagic community in Monterey Bay. This
layer is an ecologically important transition zone between the mesopelagic and
bathypelagic faunas, and contains a unique assemblage of species. We will continue to
investigate this layer, working with other institute researchers to collect and identify
microbes from within the region of reduced oxygen, and from the "milky layer"
just below it. We believe that microorganisms are essential agents in the creation and
maintenance of these layers.
Bioluminescence is a pervasive characteristic of midwater animals. Understanding its
mechanisms and how it is utilized is a key to understanding mesopelagic ecology. In 1999
we broadened this avenue of our research by initiating studies on the molecular biology
of luminescent and fluorescent proteins from gelatinous zooplankton. This work
continues to expand
our knowledge of the kinds of photoproteins found in deep-sea animals, and
to progress in ecology, taxonomy, and biochemistry. This research is being conducted in
conjunction with MBARIs program in molecular biology.