How do the above two types of food sources floating in the water column get incorporated into the sediment, and how does that signal change through the seasons of the year?
This work adds detail on the broader approach above, giving it temporal resolution, identifying key pathways though which the seabed benefits from these food sources, and providing an understanding on whether the carbon in those food sources ends up “locked up” in the sediment habitat, or whether it is recycled and lost again to the water column. This later part is crucial to understand whether the important role played by seaweeds in taking CO2 from the water (and therefore increasing the ability of the ocean to absorb more CO2 from the atmosphere) indeed promotes a permanent sequestration of CO2 from the atmosphere, or whether it is just a seasonal, temporary process.
For this, MERP scientists have been running R.V Plymouth Quest cruises every 8-10 weeks to the reference site known as 'L4', 15 km SW of Plymouth. Here scientists have been using corers to get field data, and bringing sediment cores to the lab where we use different techniques, including stable isotopes for carbon and nitrogen. Key pathways investigated are: feeding processes (from the species filtering what is in the water column as food, to those eating them, small and large); bioturbation (the way in which animals burrowing in the sediment may bury fresh food like seaweed debris and plankton settling on the sediment surface and therefore make it available to deeper burrowing animals); and bioirrigation (the flushing of the sediment by burrowing animals, which may lead to a new release of the carbon that was once eaten (as seaweed and plankton) back to the water column.