Welcome

Methods

Monitoring

Each summer (June - August), the St Johns River Water Management District monitors a network of 200 SAV transects on the banks of the St Johns River Estuary and Lake George. Scientists from the Bureau of Environmental Sciences document the SAV species present, the distance that SAV beds extend perpendicular to shore, and record percent cover, canopy height, and water depth within small plots called quadrats along the length of each transect. Due to the large number of transect locations, staff typically aren’t able to reach every one, so we prioritize visiting transects with longer periods of record to best assess how SAV in the river changes over time. The transect sites are grouped into 6 regions for the purpose of this dashboard: The estuarine main stem, transitional main stem, freshwater main stem, Doctors Lake, Crescent Lake, and Lake George.

2020 sampling was constrained to the estuarine only region due to staffing and sampling limitations that occurred during COVID-19.

Terms and Metrics

• Site: Specific location visited each year for SAV monitoring

• Transect: A line placed perpendicular to shore at each site, along which the identity and spatial extent of SAV is recorded.

• Quadrats: Small areas incrementally located along each transect where SAV canopy height is recorded.

• Percent Occurrence: Percent of sites where SAV was observed when performing a transect during monitoring for each region. This is a measure of how widespread SAV is across a given area.

• Bed Width: Distance perpendicular to shore between closest and farthest observed SAV along the transect. This metric reflects the general extent of an SAV bed.

• Bed Width Minus Bare Patches: Distance perpendicular to shore that SAV would extend if all bare patches along the transect were excluded. Similar to Bed Width but accounts for patchiness of SAV.

• Canopy Height: Vertical distance in centimeters from the river bottom to the top of SAV present within a quadrat. For this dashboard canopy height is only tallied for quadrats where SAV was present, empty quadrats were ignored. For example, a transect made up of 10 quadrats, 5 empty and 5 with canopy heights of 6 cm, would have an average canopy height of 6 cm. This metric provides information on the size of plants present in each SAV bed. Due to how quadrats are incrementally spaced, it is possible for SAV to be identified along a transect, but absent from all quadrats. When this uncommon case occurs on a map, an individual canopy height may be listed as “Bare” despite having a nonzero bed width.

• Percent Cover: Percentage of a quadrat covered by any species of SAV. This metric reflects both the size and density of the plants in each bed. Average percent cover per transect was calculated in the same manner as canopy height.

• Not Sampled, Too Deep: The water depth at shore for these sites were too deep for sampling protocols.

Figures

• Bar Graphs: This dashboard contains bar graphs of SAV percent occurrence, average bed width, average bed width minus bare patches, and average canopy height for each region of the LSJR over time. These graphs contain error bars that indicate the standard error of each mean, a metric of how reliable the means may be. The larger the error bars, the more uncertainty there is.

• Maps: Each page contains interactive maps. Click on the layers button on the regional maps to change the data displayed. Click or hover over individual points to see more detailed information on each site, including monitoring dates.

2024 Regional Summary

2024 Regional Summary

2024 Regional Summary

2024 Regional Summary

2024 Regional Summary

2024 Regional Summary