Methane emissions from macrophyte beach wrack on Baltic seashores

• Published in: Ambio Vol. 52; no. 1; pp. 171 - 181
• Main Authors: Björk, Mats, Rosenqvist, Gunilla, Gröndahl, Fredrik, Bonaglia, Stefano
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.01.2023; Springer Nature B.V
• Subjects: Annan geovetenskap och miljövetenskap; Aquatic plants; Atmospheric Sciences; Baltic Sea; Beach cast; Beaches; Climate change; Daily temperatures; Earth and Environmental Science; Ecology; Ekologi; Emissions; Environment; Environmental Engineering/Biotechnology; Environmental Management; Environmental Sciences; Geochemistry; Geokemi; Global temperatures; Greenhouse gas; Greenhouse gases; Macrophytes; Marine macrophytes; Mathematical analysis; Methane; Methane emissions; Miljövetenskap; Other Earth and Related Environmental Sciences; Physical Geography; Plant Biotechnology; Research Article; Seashores; Seasonal variations; Temperature data; Växtbioteknologi; Methane; Climate change; Marine macrophytes; Greenhouse gas; Baltic Sea; Beach cast
• ISSN: 0044-7447; 1654-7209; 1654-7209
• DOI: 10.1007/s13280-022-01774-4

Beach wrack of marine macrophytes is a natural component of many beaches. To test if such wrack emits the potent greenhouse gas methane, field measurements were made at different seasons on beach wrack depositions of different ages, exposure, and distance from the water. Methane emissions varied greatly, from 0 to 176 mg CH 4 -C m −2  day −1 , with a clear positive correlation between emission and temperature. Dry wrack had lower emissions than wet. Using temperature data from 2016 to 2020, seasonal changes in fluxes were calculated for a natural wrack accumulation area. Such calculated average emissions were close to zero during winter, but peaked in summer, with very high emissions when daily temperatures exceeded 20 °C. We conclude that waterlogged beach wrack significantly contributes to greenhouse gas emissions and that emissions might drastically increase with increasing global temperatures. When beach wrack is collected into heaps away from the water, the emissions are however close to zero.