Seagrass meadows are an important component of nearshore marine ecosystems as they create structured habitat similar to that of a forest; seagrasses provide sustenance, shelter, and nursery habitat for a myriad of fish and invertebrate species. The rhyzomatic root networks anchoring the long narrow leaves of the plant into the soft coastal sediment help to stabilize shorelines while the leafy canopy buffers against wave action. Unfortunately, increasing coastal development has put significant pressure on seagrass habitats, currently experiencing worldwide decline. Aerial photography provides a valuable tool for seagrass mapping applications. This project will explore the use of Unmanned Aerial Vehicles (UAVs) to deliver high resolution, affordable aerial photography for local-scale eelgrass (Zostera marina) mapping projects. Archived aerial photography will then be used to map historic distribution of eelgrass from the 1930’s to present. By assessing the changes in historic distribution of eelgrass in the Salish Sea, we will be able to identify priority sites for conservation and restoration, as well as suggest opportunities to mitigate the impact of continued coastal development on our nearshore marine ecosystems.
01. Assess the feasibility of eelgrass mapping using digital photography acquired by UAV and explore photo-interpretive and digital mapping methodologies for delineating eelgrass distribution.
02. Using archived historic aerial photography (1932-2014) and UAV photography (2016), map historic eelgrass distribution and assess: changes of areal extent; shape and edge characteristics; potential impacts of shoreline and watershed alterations; priority sites for conservation and restoration.
Eight small to medium sized, protected bays in the Salish Sea will be studied. These sites should have a known presence of eelgrass, with reasonable historic air photo quality, be accessible without the need of a boat, and be suitable for UAV study according to the Canadian regulatory framework regarding UAV operation. Seven sites in the Southern Gulf Islands were selected: Village Bay, Horton Bay, Gallagher Bay, and Campbell Bay on Mayne Island; Lyall Harbour, Boot Cove, and Narvaez Bay on Saturna Island. The eighth site, located at the North end of the Salish Sea, is the K’omoks Estuary. This site provides an example of a medium-large bay with an intense history of industrial and residential development, where extensive estuarine conservation and restoration has occurred in recent years, and additional clearance and logistical considerations are required for UAV operation.
The SPECTRAL Lab is partnering with High Angle UAV to collect high resolution aerial imagery of eelgrass beds at our study sites.
July 12-15: Eelgrass Surveying on Saturna Island
July 12: Boot Cove
Unfortunately, our surveys on Saturna Island began with a rough start; a lethal combination of high turbidity and heavy cloud cover resulted in very poor conditions for eelgrass mapping.
July 13-14: Narvaez Bay
Our second and third survey days were spent in Narvaez Bay, part of the Parks Canada Gulf Islands National Park Reserve. While water clarity was quite high, the clouds did not want to cooperate, causing a fair amount of cloud reflectance on the water. We were surprised to find bull kelp where we did not expect it, as well as a giant Pacific Octopus puttering along the shoreline.
July 15: Lyall Harbour
Our original plans for surveying Lyall Harbour were thwarted by an unexpected and intense algae bloom. While water visibility was minimal, we did get a few very cool photos of the bloom. By the next day, the bloom had receded and the water had cleared substantially, making it possible for us to actually see the eelgrass in our photos.
June 27-30: Eelgrass surveys on Mayne Island
June 27: Campbell Bay, Mayne Island
With a pitiful secchi depth of 2.25m, we relinquished any hope of attaining imagery of the deep water eelgrass edge at Campbell Bay. However, with the nice afternoon low tide, we were able to acquire some gorgeous shots of the shallow eelgrass right at the surface, creating a fabulous contrast between the shallow eelgrass and the surrounding turbid waters.
June 28: Village Bay, Mayne Island
Our survey of Village Bay returned a glimmer of hope to our dreams of crystal clear waters, with a secchi depth of 4.75m, doubling the depth of water visibility at Campbell Bay. The survey went off without a hitch, and the deep water edge of the eelgrass is clearly visible in the imagery. A great success!
June 29: Gallagher Bay, Mayne Island
Gallagher Bay is the site of this year's eelgrass survey conducted by the Mayne Island Conservancy Society and the Vancouver Apneist Freediving Club. We flew a preliminary survey of the bay, but due to poor water clarity we will be flying this bay again. The photo on the right shows a potential Zostera japonica sighting
June 30: Horton Bay, Mayne Island
Horton Bay hosts eelgrass meadows around the perimeter of the bay, and as a result, an incredible diversity of marine life. While we conducted our survey, a gaggle of Canada geese puttered about the eelgrass on the South shore, munching on Ulva. We counted 40 adult geese, and 17 juveniles. While kayaking, we were surrounded by a school of shiner perch. It seemed like there were thousands of them racing about the shallow brackish waters near the outlet of Horton Creek. Due to its sheltered nature, Horton Bay is a very popular mooring location for boats.
June 22, 2016: Final field methods testing at Whiffin Spit, Sooke BC
With the blessings of the Municipality of Sooke, the SPECTRAL team joined High Angle UAV for a final day of flight tests at Whiffin Spit. Here we practiced our field procedures for the UAV and kayak surveys to be conducted next week on Mayne Island. From our survey we were able to produce a high resolution mosaic of the area with concurrent ground truthing by kayak videography. While the vegetation you see on the shoreline is a collection of macroalgae, mostly Ulva, you can see how interesting this will be for eelgrass mapping! The Sooke basin is fairly turbid (2.2m secchi depth at our site), so we're looking forward to surveying the crystal clear waters of the Southern Gulf Islands next.
Check out the article in the Sooke News Mirror!