High-Resolution Drone Images Show That the Distribution of Mussels Depends on Microhabitat Features of Intertidal Rocky Shores

Type Article
Date 2022-11
Language English
Author(s) Barbosa Romina1, Jaud MarionORCID2, 3, Bacher CedricORCID4, Kerjean Yann1, Jean Frederic1, Ammann Jérôme3, Thomas Yoann1
Affiliation(s) 1 : IRD, Ifremer, University of Brest, CNRS, LEMAR, 29280 Plouzané, France
2 : European Institute for Marine Studies (IUEM)—UAR 3113, University of Brest, CNRS, IRD, IUEM, Rue Dumont d’Urville, 29280 Plouzané, France
3 : UMR Geo-Ocean 6538, University of Brest, CNRS, Ifremer, IUEM, Rue Dumont d’Urville, 29280 Plouzané, France
4 : Ifremer, DYNECO, 29280 Plouzané, France
Source Remote Sensing (2072-4292) (MDPI AG), 2022-11 , Vol. 14 , N. 21 , P. 5441 (17p.)
DOI 10.3390/rs14215441
Note This article belongs to the Special Issue Remote Sensing Applied to Marine Species Distribution
Keyword(s) remote sensing, structure from motion photogrammetry, species distribution, habitat mapping, topography, slope, orientation, monitoring

In this study, we used orthomosaics and a digital surface model (DSM) generated from drone surveys to (1) characterize the distribution of mussel (Mytilus galloprovincialis) aggregations at high resolution (centimeters), and (2) evaluate the role of topographic features, intertidal height, slope, and orientation angle in determining mussel distribution on two rocky shores oriented differently on both sides of a beach on the French Brittany coast. We first developed and tested a mussel visualization index (MVI) for mapping mussel aggregations from drone images. Then, we analyzed mussel distribution on the two shores. The results showed a contrasted total mussel-occupied area between the two rocky shores, with a higher occupation rate and a clear pattern of distribution depending on topographic features on the rocky shore oriented to the west. Intertidal height, and its associated immersion time, was the main factor determining mussel distribution. An optimum intertidal height was found in the center of the distribution height range, at c.a. 4.5 m above the lowest astronomical tide (LAT), where individuals are under immersion phase on average 43% of the time. Within this optimum, the occupation rate of the mussels was significantly higher in microhabitats facing south and west, particularly at intermediate slope angles. These results demonstrate the role of microhabitat topographic features on the development of intertidal mussels and their final distribution. Furthermore, the results highlight the importance of mesoscale structures of habitats (e.g., 100 m), which seem to be responsible for the differences we observed between the two shores. Our methodological approach highlights the main advantage of using high-resolution drone images to address ecological processes in intertidal ecosystems. Indeed, drone imagery offers the possibility to assess small-scale interactions between individuals and habitat conditions over a wide area, which is technically infeasible from fieldwork approaches or by using satellite remote sensing due to their lower resolution. Scale integration and methodological complementarity are powerful approaches to correctly represent the processes governing the ecology of intertidal ecosystems. We suggest using this methodology to monitor long-term changes of sentinel sessile species.

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Barbosa Romina, Jaud Marion, Bacher Cedric, Kerjean Yann, Jean Frederic, Ammann Jérôme, Thomas Yoann (2022). High-Resolution Drone Images Show That the Distribution of Mussels Depends on Microhabitat Features of Intertidal Rocky Shores. Remote Sensing, 14(21), 5441 (17p.). Publisher's official version : https://doi.org/10.3390/rs14215441 , Open Access version : https://archimer.ifremer.fr/doc/00800/91247/