Passive remote sensing technology for mapping bull kelp (Nereocystis luetkeana): A review of techniques and regional case study

Spatial and temporal persistence of nearshore kelp beds on the west coast of British Columbia, Canada using satellite remote sensing

“…2). The spectral signature of kelp shows high reflectance in the near-infrared (NIR) and low reflectance in red bands, while sparse or submerged kelp beds show lower ratio of NIR to red due to the effect of water, which strongly absorbs NIR (detailed spectral analysis in (Schroeder et al 2019)).…”

“…In this case, images collected prior to or after peak growth may underestimate maximum kelp extent. 3 Differences in image quality due to environmental conditions at the time of acquisition including tide height, glint and water surface (Schroeder et al 2019). Effects of currents can cause changes to surface kelp extent on an hourly and even minutely basis (Britton-Simmons et al 2008).…”

“…A longer time series of data with greater regional coverage would allow better understanding of variability and its relationships to long-and shortterm local and global scale environmental conditions. Other satellite platforms can be used for mapping kelp extent, each with their own strengths and weaknesses (Bennion et al 2019;Schroeder et al 2019). The use of commercial high-resolution satellite imagery as in this study allows the user to acquire images during optimal conditions of tide height, cloud cover, water conditions and kelp growth resulting in the highest quality imagery for mapping kelp.…”

“…Many of these successful analyses focus on species that form large beds, such as giant kelp, Macrocystis pyrifera, allowing the use of lower spatial resolution imagery from Landsat (Cavanaugh et al 2010). However, detecting bull kelp, which may form fringing beds adjacent to the shoreline, may require high spatial resolution satellite, aerial or drone images ranging from 0.2 m to 2-4 m in resolution (Deysher 1993;Schroeder et al 2019). This study uses a time series of high-resolution satellite imagery from 2004 to 2017 to map bull kelp beds on the West Coast of British Columbia, Canada, and provides an analysis of changes in kelp persistence and its relationship to global and local scale environmental conditions.…”

Branching Algorithm to Identify Bottom Habitat in the Optically Complex Coastal Waters of Atlantic Canada Using Sentinel-2 Satellite Imagery

“…Satellite remote sensing of seagrass and coral habitat is widely used in tropical clear waters, where bottom habitat is readily detectable to great depths (<40 m) (Hossain et al, 2015;Kovacs et al, 2018;Wicaksono et al, 2019). Satellite remote sensing is also widely used in a range of water types for certain seaweed habitats, when the vegetation canopy reaches the surface, as the measured signal comes from the sea surface, opposed to the seafloor, and there is negligible interaction of the water-leaving signal with the water column (e.g., Schroeder et al, 2019;Bell et al, 2020;Mora-Soto et al, 2020). A more complicated classification question arises for submerged macrophytes in optically complex temperate waters, where high CDOM, suspended particulate matter, and phytoplankton concentration reduce the maximum depth at which the seafloor is visible compared to tropical habitats (3-10 m vs. <40 m).…”