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ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Watershed Physical Processes Research » Research » Publications at this Location » Publication #403065

Research Project: Acoustic and Geophysical Methods for Multi-Scale Measurements of Soil and Water Resources

Location: Watershed Physical Processes Research

Title: Determining the relationship between observed algal activity and ultrasonic attenuation measurements

item CARPENTER, BRIAN - University Of Mississippi
item GOODWILLER, BRADLEY - University Of Mississippi

Submitted to: Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 10/15/2022
Publication Date: 10/27/2022
Citation: Carpenter, B., Goodwiller, B. 2022. Determining the relationship between observed algal activity and ultrasonic attenuation measurements. Meeting Proceedings.

Interpretive Summary: Abstract only,

Technical Abstract: A Single Frequency Acoustic Attenuation Surrogate was developed by NCPA to measure suspended sediment concentrations using 20 mega hertz acoustic signals. Previous work hypothesized that biological factors, such as population variation or algal movements, could also be determining factors in increasing acoustic signal attenuation when there is an absence of suspended sediment transport. This change in attenuation may occur in dense colonies because increasing light intensity leads to high photosynthetic rates during the day, which can produce oxygen bubbles within colonies that increase buoyancy and cause algal cells to rise in the water column. In contrast, respiration at night consumes oxygen bubbles, resulting in sinking algal colonies. To test this hypothesis, semi-controlled experiments in still water with large algae populations were initiated in conjunction with United States Department of Agriculture-Agriculture Research Service-National Sedimentation Laboratory. The Single Frequency Acoustic Attenuation Surrogate instrumentation was deployed at The University of Mississippi Biological Field Station to investigate the relationship between acoustic signal attenuation and algal activity. Ancillary measurements were also monitored including light intensity, dissolved oxygen, and water temperature in an environment without sediment transport. Cyanobacteria was the dominant algal group in the limno-corral, and vertical movement of cyanobacteria is modulated by changes in cell density, gas vesicles inside of cells, and gas bubbles between cells in dense colonies. Measurements of dissolved oxygen concentrations were made in attempt to determine if acoustic attenuation was related to diel patterns in dissolved oxygen providing a potential linkage between oxygen concentrations, light, algal biomass and acoustic attenuation.