Seagrasses continue to release methane after their die-off https://www.mpg.de/18255203/0211-mbio-dead-or-alive-seagrasses-continue-to-release-methane-after-their-die-off-154772-x
Methane is formed from seagrass meadows, even decades after the plants died off
On the one hand, they sequester carbon dioxide from the atmosphere and store it underground