Andrew W. Howell and Dr. Robert J. Richardson
North Carolina State University; Dept. Crop and Soil Sciences
Why do we want to sample submersed vegetation biomass using sonar?
Invasive aquatic plants, such as non-native hydrilla (Hydrilla verticillata), negatively impact waterway systems in the southeastern United States and on a global scale. Often, these aquatic weed species impede recreational activities, power generation, and disrupt native ecological systems. Costs associated with aquatic weed management include expenses accompanied with monitoring, mapping, and implementing control measures. Prompt detection and accurate mapping of submersed aquatic vegetation (SAV) are critical components when formulating management decisions and practices. Therefore, SAV management protocols are often reliant upon the perceived extent of invasion. Traditional biomass sampling techniques have been widely utilized, but often require significant labor inputs, which limits repeatability, the scale of sampling, and the rapidness of processing. Advances in consumer available hydroacoustic technology (sonar) and data post-processing offer the opportunity to estimate SAV biomass at scale with reduced labor and economic requirements.
The objectives of this research were to document the use of an off-the-shelf consumer sonar/gps chartplotter to: 1) describe and characterize a relationship between hydroacoustic biovolume signature to measured hydrilla biomass; 2) develop algorithm for on-the-fly assessment of hydrilla biomass from interpolated biovolume records; 3) define seasonal hydrilla growth patterns at two NC piedmont reservoirs; and 4) create a visual representation of SAV development over time. From these objectives, the expected outcome was to describe a protocol for passive data collection while reducing the economic inputs associated with labor efforts involved in biomass sampling and post-processing evaluations. In our research, a Lowrance HDS-7 Gen2 was utilized to correlate biomass from monospecific stands of hydrilla within two different North Carolina piedmont reservoirs using BioBase 5.2 (now marketed as EcoSound – http://www.biobasemaps.com), cloud-based algorithm to aid in post-processing.
Continue reading “Guest Blog: Correlations between EcoSound Biovolume and Aquatic Plant Biomass”
A primary strength of BioBase EcoSound is its simplicity and that is reflected in the easy 3 step process of “Collect,” “Upload,” and “Analyze” (Figure 1).
|Figure 1. The core process of EcoSound depicting the 3 Steps of “Collect,” “Upload,” and “Analyze.”
But there are many strategies that users can employ that will ensure that they will get the best EcoSound outputs possible. We’ll focus on several questions under each of the three categories
Continue reading “BioBase 3 Step Process: Important Details!”
We are happy to report the first BioBase-focused paper finally published in the peer-reviewed literature: “Combining hydroacoustic and point-intercept survey methods to assess aquatic plant species abundance patterns and community dominance.” The paper is co-authored by Navico staff and researchers from Minnesota (Donna Dustin), Florida (Dean Jones), and North Carolina (Justin Nawrocki) and published in the January 2015 issue of the Journal of Aquatic Plant Management. The paper describes a simple technique for combining aquatic plant species presence/absence information with detailed aquatic plant abundance metrics processed by BioBase [EcoSound] from Lowrance sonar logs to generate detailed information on what aquatic plant species are dominating a mapped lake. The technique has the potential to greatly advance our understanding of the conditions that cause invasive aquatic plants to “take-over” (a colloquial term for dominate) lakes and provide an objective benchmark from which to evaluate aquatic plant management interventions.
Below is the abstract. Please contact corresponding author Ray Valley (firstname.lastname@example.org) if you are interested in a copy of the paper.
Many ecosystem goods and services are derived from aquatic plant–dominated environments and the abundance and composition of aquatic plant communities affects habitat, recreation, angling, aesthetics, and commerce. We describe standardized hydroacoustic methodology that complements species composition surveys and generates comprehensive aquatic plant abundance data with little additional assessment or analysis effort than is already put forth for species surveys. Using data from 22 lakes across the United States, collected by biologists with varying levels of expertise, we compare hydroacoustically derived biovolume with two other semiquantitative measures of whole-lake abundance (frequency of occurrence and ‘‘rake fullness’’). Although we documented some significant correlations between hydroacoustically derived biovolume and frequency and rake fullness, frequency or rake fullness was difficult to interpret biologically on a lakewide scale. We also describe a dominance index that incorporates both species composition and vegetation biovolume to evaluate the degree that a species dominates a local assemblage. We found that the extent of aquatic plant growth and invasive dominance was related to lake productivity with highest biovolume and dominance occurring in mesotrophic to eutrophic study lakes. Using both empirical and simulated data, we also found no significant differences between dominance calculated from a simple metric that gives equal weight to all species at a survey site and a metric that incorporated rake fullness for each species.
Earlier this year, Senior Biologist Scott Bryan from the Central Arizona Project (CAP) blogged about how the CAP is using BioBase to manage sedimentation in Arizona’s lifeblood 336-mile aqueduct. Since then, CAP GIS Wizard Glenn Emanuel has worked some amazing magic on the BioBase grid exports using Spatial and 3D Analyst Extensions for ArcGIS (Figure 1).
|Figure 1. Images showing the change in sediment volume prior to and after experimental dredging activities in a Forebay of the CAP canal. The Raster Calculator in ArcGIS’s Spatial Analyst was used to subtract a “current” bathymetry from a baseline bathymetry (e.g., “as built”) to estimate sediment height and volume. Images are 3-dimensionally enhanced using 3D Analyst for ArcGIS. Image courtesy of Scott Bryan and Glenn Emanuel, Central Arizona Project
The data and images allow CAP to make informed decisions regarding the efficiency of sediment removal operations. In addition, ArcScene was used to produce a 3D scene of the forebay (Figure 2), which can then be animated with a video fly-through.
|Figure 2. “Fly-through” images of sediment height in Little Harquahala Forebay in the CAP Canal collected by Lowrance HDS sonar and GPS, BioBase cloud processing software, and finally exported/imported into ArcScene. Image courtesy of Scott Bryan and Glenn Emanuel, Central Arizona Project.
Any user of BioBase properly equipped with the proper third party GIS software can create these amazing map products that are more than just pretty pictures. They create a real-life, tangible perspective of aquatic resource conditions that BioBase users are interested in managing, protecting, and restoring.
We love to show off the accuracy of our submerged vegetation mapping algorithm. Check out this break in the weeds that was picked up and clearly displayed in the ciBioBase vegetation layer:
The BioBase vegetation layer is automatically generated by powerful cloud computers so you receive an objective output every time. The white line on the right and red dot on the left show the boat position as a cross section and aerial view of the water column respectively.
Submerged vegetation is displayed as percent biovolume (BV%) which represents the percent of the water column occupied by plants. This provides a clear picture of total plant abundance from each trip on the water. Data can be passively logged because none of our users have to do any of the processing when they get back to the office. Do what you were already planning to do and our automated system will take care of the rest.
Let us know if you have any questions about how this process works!