Sentinel-2 unveils the seasonal rhythm of intertidal seagrass

The intertidal zone is the realm the place the ocean meets the land between excessive and low tides, and right here seagrasses can type intensive meadows. These flowering marine vegetation present important habitats, performing as shelter, nurseries, and feeding and spawning grounds for a various vary of birds, fish and invertebrates. Past their ecological significance, seagrass meadows additionally stabilise sediments and defend coastlines from erosion.

Monitoring the incidence, extent, situation and variety of intertidal seagrass as a key biodiversity variable is crucial for assessing the general well being of native ecosystems.

Present international estimates of seagrass protection don’t differentiate between seagrasses within the intertidal zone and people within the subtidal zone, which stay submerged beneath the ocean floor.

Nevertheless, a latest paper, printed in Communications Earth & Surroundings, particulars how a crew of scientists used high-resolution imagery from the Copernicus Sentinel-2 mission to display its skill to map intertidal seagrass meadows and their seasonal adjustments throughout continents with consistency and precision.

Their analysis was funded by one in every of ESA’s Science for Society tasks referred to as Biodiversity of the Coastal Ocean, or BICOME.

Bede Ffinian Rowe Davies from Nantes College in France and lead writer of the paper, stated, “Coastal areas, like a lot of the world, are experiencing speedy and alarming biodiversity loss. To deal with this, it’s essential to develop environment friendly monitoring strategies in order that well timed and acceptable motion might be taken to protect delicate ecosystems.

“Utilizing knowledge from Sentinel-2 throughout the BiCOME undertaking, we have been in a position to reveal vital differences due to the season in intertidal seagrass. The peaks in extent shifted by as a lot as 5 months – difficult earlier assumptions that there was little or no seasonal fluctuation.”

As examples, the satellite tv for pc photographs displayed above present the adjustments in intertidal seagrass cowl within the Cádiz Lagoon, Spain. One was taken in Could 2018 and the opposite in November 2021.

The satellite tv for pc photographs beneath illustrate adjustments in intertidal seagrass cowl within the Bay of Bourgneuf, situated north of the Bay of Biscay, off the western coast of France. The picture on the left, from April 2021, exhibits sparse intertidal seagrass, whereas the picture on the precise, from September 2021, reveals ample development.

Victor Martinez Vicente, BiCOME undertaking principal investigator, famous, “This research demonstrates the potential of satellite tv for pc observations to trace adjustments within the extent of pure coastal ecosystems, offering beneficial insights for indicators within the International Biodiversity Framework. Additional analysis is required to develop long-term satellite-based monitoring techniques and datasets to help international progress towards reaching the framework targets.”

ESA’s Marie-Helene Rio, added, “These new findings clearly display the worth that Sentinel-2 can convey to monitoring intertidal seagrass. We now consider that these intertidal meadows behave in a different way to the kind of seagrass that spends most of its life submerged by seawater. This implies that earlier estimates, which grouped the 2 sorts collectively, may very well be deceptive.”

“The analysis paves the best way to additional monitoring and evaluation of intertidal seagrass meadows utilizing Sentinel-2 knowledge.”

The Sentinel-2 satellites every carry a multispectral imager that takes high-resolution photographs of Earth’s land, islands, and inland and coastal waters. And with a big swath width of 290 km, it offers these photographs in 13 spectral bands with resolutions of 10 m, 20 m and 60 m.

The third Sentinel-2 satellite tv for pc, Sentinel-2C, was launched on 5 September 2024, and has already delivered its first photographs of Earth.