Data for: Prevalent fingerprint of marine macroalgae in Arctic surface sediments

Macroalgal forests export much of their production, partly supporting food
webs and carbon stocks beyond their habitat, but evidence of their
contribution in sediment carbon stocks is poor. We test the hypothesis
that macroalgae contribute to carbon stocks in arctic marine sediments. We
used environmental DNA (eDNA) fingerprinting on a large-scale set of
surface sediment samples from Greenland and Svalbard. We evaluated eDNA
results by comparing with traditional survey and tracer methods. The
eDNA-based survey identified macroalgae in 94% of the sediment samples
covering shallow nearshore areas to 1,460 m depth and 350 km offshore,
with highest sequence abundance nearshore and with dominance of brown
macroalgae. Overall, the eDNA results reflected the potential source
communities of macroalgae and eelgrass assessed by traditional surveys,
with the most abundant orders being common among different methods. A
stable isotope analysis showed a considerable contribution from macroalgae
in sediments although with high uncertainty, highlighting eDNA as a great
improvement and supplement for documenting macroalgae as a contributor to
sediment carbon stocks. Conclusively, we provide evidence for a prevalent
contribution of macroalgal forests in arctic surface sediments, nearshore
as well as offshore, identifying brown algae as main contributors.