Marc Weissburg, Associate Professor
Ph.D., Ecology and Evolutionary Biology, State University of New York, Stony Brook, 1990
Phone: (404) 894-8433
Fax: (404) 894-0519
Office: ES&T 2238
Research Interests
Chemical ecology: chemically-mediated orientation and guidance in marine invertebrates, behavioral strategies for orientation in relation to fluid flow in aquatic environments, predator-prey and mating behavior mediated by chemical cues. Sensory ecology and physiology: sensory physiology of chemo- and mechanoperception in marine crustaceans, development of chemosensory systems, neuroanatomy of crustacean chemosensory and mechanosensory systems, signal structure and transmission of chemical and fluid mechanical signals.
Sensory biology of chemosensory navigation in turbulent plumes.
Chemical communication may be the most important way in which aquatic animals obtain information about their environment. Many aquatic animals use chemical cues to find food, mates, and shelter. We use studies of behavior, fluid physics and chemistry (often in collaboration with chemists and engineers) to examine the sensory and behavioral strategies that animals employ to navigate through odor plumes (see video of crab foraging in our flume here). We ask, what types of odor properties contain information, how does this vary with flow environment, how do animals use these signals, and why/when do animals use different strategies? Behavioral studies of crabs, whelks, lobsters and urchins across a range of flow environments have helped us to explore the relationship between flow properties and navigational performance, and define the capabilities of animals of different sizes, movement speeds, and body plans. Investigations of chemical signal structures are used to determine the information available to animals, and how this information can be changed depending on the flow environment.
These comparative studies indicate that animal sensory performance is tuned for specific conditions so that the flow environment may be a niche dimension that partially determines competitive superiority (i.e. resource finding). For instance, slow vs. rapidly moving predators use different signal properties and hence, are not equally affected by turbulence. We also have discovered predictable relationships between sensory strategies and animal/sensor morphology that we will continue to explore. Our newest efforts use simultaneous 3D laser visualization of odor plume structure (see an animated view of odor plume structure here) and animal tracking movements. These studies will be used to precisely define the role of spatial and temporal properties of odor plumes in navigation by allowing us to determine the explicit relationship between odor signal structure and animal movements. We hope to use these studies to develop strategies for engineering chemical guidance mechanisms into autonomous or remotely controlled vehicles.
Sensory physiology and ecology of zooplankton
Zooplankton such as copepods are important links in the oceanic food chain, and use their acute mechanosensory system to find prey and escape from predators. We have investigated copepod mechanosensory capabilities by combining high-speed video observations of setal bending with neurophysiological techniques. One of our most surprising findings is that copepod mechanosensory neurons can produce responses that are 3-5 times faster than previously known for other animals. Other efforts have been directed at understanding behavioral mechanisms used by copepods to follow 3D trails during mate finding. Our video motion-analysis of movements of males during pursuit of females has established that these small animals are capable of precise directed orientation in 3D space using chemical and fluid mechanical cues.
In conjunction with oceanographers (Jeannete Yen) and fluid physicists (Don Webster) we are currently exploring how mechano- and chemosensory responses promote the aggregation of copepods to small-scale fluid features in the ocean, such as thin layers. This involves observing copepods in a device where we create and measure fine scale flow and chemical gradients. We find that many different species of copepods aggregate to patterns in velocity, chemical attractants, or both. Thus, structure in the ocean may be as important in maintaing ecological relationships as it is in terrestrial habitats.
Sensory ecology of chemosensory interactions
The ability of animals to identify and locate predators, prey and mates is an important determinant of their ecology. We use our understanding of sensory biology to examine the ecological consequences of chemically-mediated information gathering. Our questions concern how the flow environment changes odor plume structure to impact the ability of animals to employ chemical signals, how this alters the ecological interactions among predators, prey and competitors that use these signals, and the consequences of these alterations for community structure and regulation. Our methods are explicitly field based, and manipulative, and involve measurements of both the physical environment and ecological interactions. We have found that the flow environment sets limits of predator effectiveness and may change the dominance of one competitor over the other. Sensory abilities seem optimized for specific conditions of flow velocity and turbulence such that effective predators in some regions display poor foraging ability in other regions.
Further complexity occurs because prey and predators both detect one another using chemical cues; shifting advantages between predator and prey sensory abilities in different flow environments cause effects of predation to shift from direct consumptive effects to trait mediated effects (effects exerted through changes in prey behavior), and alters the scale over which these interactions occur. Thus, indirect vs. direct effects, the potential for trophic cascades, or trait-mediated interactions may all be contingent on the extent to which predators and prey are able to sense each other. We are extending our studies to determine if larger scale demographic properties of predators and prey are predictable through understanding their sensory abilities.
Biologically-inspired design
Biologically-inspired design, or biomimicry, capitalizes on the rich source of design solutions present in biological processes at all levels. This innovative method trains scientists and engineers to ask, “what problems does this biological system solve?”, teaches biologists to identify potential design solutions relevant to specific problems, and gives designers sufficient knowledge and familiarity with biology to seek solutions from the organic world. As Co-director of the Center for Biologically-inspired Design (www.cbid.gatech.edu), my goal is to help engineers and biologists to develop a common language and mode of thinking that facilitates collaborative problem identification and solving. We pursue this in our own work by using our insights on animal navigation to help develop better autonomous tracking agents. I am also engaged in educational, research and outreach activities that will inform the scientific, business and general communities about the important contributions of biomimicry, and equip our faculty and students with a new tool in our tool kit.
Selected Publications
Dickman, B.D., D.R. Webster, J. L. Page and M.J. Weissburg. 2009. Three-dimensional odorant concentration measurements around actively tracking blue crabs Limnol. Oceanogr. Methods 7:96–108. (PDF).
Smee, D.L. and M.J. Weissburg. 2006. Claming up: environmental force diminish the perceptive ability of bivalve prey. Ecology. 87: 15871598 (PDF)
Woodson, C.B., D.R. Webster, M.J. Weissburg, and J. Yen. Environmental gradients elicit behavioral responses in the calanoid copepod, Temora longicornis: Ecological implications of oceanographic structure. Limnol. Oceangr.
Webster, D.R. and M.J. Weissburg. 2001. Chemosensory guidance cues in a turbulent chemical plume. Limnology and Oceanography 46:1034-1047. (PDF)
Smee, D.L., M.C. Ferner and M.J. Weissburg. 2008. Environmental conditions alter prey reactions to risk and the scales of nonlethal predator effects in natural systems. Oecologia 156: 399-409. (PDF)