Collaborative Research: Chemical Orientation in Turbulent Environments Above Natural Stream Substrates: The Role of Bed Roughness and Turbulence Structure on Search Mechanisms

Bowling Green State University, Bowling Green OH

Investigators

Abstract

This collaborative proposal describes research that links stream hydrodynamics, turbulent transport of odor signals, and the sensory ecology and behavior of the crayfish Orconectes rusticus. Crayfish use water-borne chemical signals ("odor plumes") as navigational cues for locating food, burrows, or mates, and for avoiding predators. The nature of the spatial and temporal variability ("structure") of the odor plumes depends on the hydrodynamic conditions, which, in turn, depends on the physical characteristics of the stream. The goal of the proposed research is to understand how crayfish use odor plumes to locate underwater objects. In particular, we plan to investigate how the crayfish navigational behavior varies under different hydrodynamic conditions (associated with different types of stream substrate materials). By focusing our attention to the changes in odorant structure and associated orientation behavior over different substrate types, we hope to gain insight into the specific algorithms and information cues used by the animals. Ultimately, the knowledge gained from the proposed study could be used to design robotic vehicles to search for dangerous underwater objects, or to protect crayfish habitat in managed ecosystems. Environmentally, crayfish are keystone species for many stream habitats and understanding the physical, biological, and chemical factors that influence their behavior will lead to a broader understanding of stream ecology and the human impact on stream ecology. In particular, detailed knowledge of how stream habitats influence the distribution of chemicals will provide the information necessary to understand not only crayfish and stream ecology, but will help elucidate the physical mechanisms behind pollution transportation in streams and their possible impact on stream ecosystems. The work outlined in this proposal is a collaborative effort between a biologist and engineer that will lead to cross-disciplinary training of both graduate and undergraduate students. In addition, new technical advances will be achieved through the development of high-speed and fine-scale three-dimensional measurements of chemical concentrations in different natural flow regimes. The development and quantification of these techniques will benefit a wide array of fields from oceanography to environmental engineering.