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David Fields

David Fields
Senior Research Scientist
Bigelow Laboratory for Ocean Sciences
P.O. Box 475
180 McKown Point Road
West Boothbay Harbor, ME   04575-0475
U.S.A.
Phone: 207 633 9600
Fax: 207 633 9641

Curriculum Vitae

Education

Basic outline of research

My current research projects investigate the role of chemical and fluid mechanical signals in mediating zooplankton behavior. I am interested in the fine scale structure of signals, how signals are detected, zooplankton behavioral responses to fluid signals, and how zooplankton behavior is manifested in their local and global distribution. This work combines small-scale fluid mechanics, neurophysiology and animal behavior. I apply information derived from examining small-scale interactions towards understanding large-scale distribution patterns.

Active Projects

Research Council of Norway - The sensory biology of host detection in the parasitic salmon lice Lepeophtheirus salmonis: electrophysiological and behavioral investigations The project investigates the sensory cues (visual and olfactory) associated with host location in the salmon louse. Our longer-term goal is to generate sufficient information to establish a basis for disruption of the louse life cycle by interfering with their ability to locate a host.

NSF- Bio Oce. Collaborative Research: The role of phytoplankton ballast material in deterring copepod grazing Many groups of marine protists (algae and protozoa) are "armored" with thickened cell walls, coatings of scales, hard "cases" (tests, loricas), or latticework "skeletons". The inferred evolutionary function of these mineral deposits is to deter grazing. However, to date there are no direct measurements of grazing rates on protists as a function of their mineral content. With the recent development of silica specific stains and state of the art flow cytometry techniques we are poised to make these measurements.In this study, we directly test the relationship between the per cell minerals quota and the ingestion rates of copepods. Using well controlled algal rearing techniques, we will create phytoplankton cells that differ in the relative degree of mineral armor. Mineral load will be determined chemically (chemical digestion), visually (SEM) and photometrically (mineral and cell surface specific dyes and flow cytometry). The grazing protection conferred by biogenic minerals will be examined against copepod predation with detailed examination (microcinematography) of the behavioral mechanisms that underlie the selective process.

PI - NSF (IOB) has provided us with three years of support to examine the characteristics of the setal motion (and the required fluid motion and force) that gives rise to the neurophysiological response in copepod mechanoreceptors. The work will elucidate the salient features of a fluid disturbance that copepods use to differentiate among the myriad of fluid signals in their environment and it will address how copepods code these complex signals in a rapid yet highly accurate manner.

ONR - Energy Transfer to Upper Trophic Levels on a Small Offshore Bank. We propose to combine field observations and laboratory experiments to understand the coupling of physical and biological processes that transfer energy from lower to higher trophic levels on a small offshore bank. Our proposed study builds on observations made in 2005 and 2006 on Platts Bank, western Gulf of Maine. We will focus on the interaction of internal waves with the bank (topographic effects) and its planktonic organisms (especially euphausiids), and the relationship of these processes to the distribution, feeding and residence times of upper trophic level predators (especially humpback whales). Platts Bank is an area of intense feeding relative to surrounding waters, and there is strong evidence from other studies in the Gulf of Maine and elsewhere that offshore features such as Platts Bank are focal points for feeding by a variety of migratory animals. Our goal is to understand the mechanisms behind these patterns and their temporal variability. Linkages among networks of these sites are crucial to the long-term success of highly migratory species. Understanding the dynamics and roles of offshore features such as Platts Bank thus has a number of management implications, both short and long term. Operationally (e.g., for non-combat naval activities, shipping lanes, fishing), this knowledge can help predict feeding and migration patterns and reduce conflicts between humans and marine vertebrates. Understanding how specific places and processes support upper trophic level predators can inform management about measures needed to sustain the diversity and function of the Gulf of Maine ecosystem. Our study will introduce a new interdisciplinary focus to four Maine institutions. We envision expansion of this research to include a range of offshore topographic features that have mostly received little attention, and collaboration with groups elsewhere in the Gulf of Maine.

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Professional Affiliations and Memberships