Meeting Abstract
59.5 Sunday, Jan. 5 14:30 The Field Measurement of Chemical Plumes in Headwater Streams: Implications for Ecological Interactions EDWARDS, D/D*; MOORE, P/A; Bowling Green State University davide@bgsu.edu
Aquatic organisms use chemoreception in lotic systems for a broad spectrum of ecologically relevant decisions. In order to appreciate behavioral responses to chemical stimuli, one needs an understanding of the physics of chemical transmission within moving fluids (i.e., turbulence). Because of the chaotic nature of turbulence, chemical plumes have a spatial microstructure with fluxes in chemical concentrations. An organism that needs to extract ecological information from these fluxes does so on temporal scales of seconds and spatial scales of millimeters. The purpose of this study was to quantify chemical signal distribution within the field. A section of Carp Creek, Emmett Co., MI was selected to examine the relationship between hydrodynamics and interflow odor plume characteristics. In order to imitate a pollution plume influx 72 hours post heavy rainfall, a chemical tracer was introduced in a way to mimic groundwater flow. Stream velocity and chemical fluxes were measured using an ADV and electrochemical microelectrode simultaneously. Thirty six different downstream locations in grid fashion were chosen for measurements. Measurements of the microscale structure of the chemical plume showed an intermittent signal that consistently changed with distance from the odor source, height above the substrate, and distance from the center line of the plume. Animals exposed to chemical fluctuations would either perceive or be impacted by periods where concentrations were significantly higher than the overall average concentration. These measurements show that standards for pollution exposure need to consider the turbulent dispersion of chemical signals rather than time-averaged models. The relationship between fluid dynamics, pollution exposure and organism physiology are complex and need to be evaluated in natural systems.
