MarineSediment-BlueC-eDNA v1

Abstract

This protocol was established for the Nordic Blue Carbon Project (2017–2020) for tracking the presence of kelp DNA in marine sediments, providing preliminary quantitative information on the original kelp biomass. Nordic blue forests are coastal vegetated habitats, such as kelp forests, eelgrass meadows and rockweed beds, that are important natural sinks for carbon and thereby climate regulation. They also play an important role in climate adaptation. Simultaneously, blue forests are at high risk from climate change and other human impacts, such as eutrophication and coastal development. The advent of eDNA methods for tracking animal or vegetal organisms in water or sediment matrices, has enabled not only geographical detection without collection of the organism but also temporal study of their presence in dated sediment cores. The fate of eDNA and its persistence in the environment is intimately related to its biophysical surroundings. eDNA entrapped in sediments may be preserved on long time scales, up to centuries, enabling historical tracking of the presence of a species on a site. The present protocol was developed for tracking eDNA of a predominant Norwegian kelp species, Laminaria hyperborea, in dated marine sediment cores. This approach enables confirmation of species specific contribution to carbon sequestration in an effort to evaluate marine sediments operating as carbon sinks. This work was financed by the Norwegian Environment Agency (Miljødirektoratet) contract #17080044 and published in a NIVA report ISBN 978-82-577-7384-7, Norwegian Environment Agency Report M-2090|2021, Blue Carbon eDNA – A novel eDNA method to trace macroalgae carbon in marine sediments. .

Identifying and protecting macroalgae detritus sinks toward climate change mitigation

“…This provides important evidence that helps to understand the ecological processes underpinning macroalgal blue carbon (Ortega et al, 2020; Queirós et al, 2019). However, given the spatial and temporal contextual specificity of the seabed processes that determine carbon sequestration rates (Legge et al, 2020; Queirós et al, 2019; Snelgrove et al, 2018) and the dynamic nature of transport pathways connecting macroalgal beds to potential sedimentary carbon sinks sites, it seems ill advised to expect that any site‐specific relationship between sedimentary macroalgal eDNA and POC stores should be expected to hold ubiquitously (Anglès d'Auriac et al, 2021; Ortega et al, 2019).…”

“…Because macroalgal blue carbon science is in its infancy, in the present study, as in others (Ortega et al, 2019, 2020), universal 18S rRNA PCR primers that amplify short (~260‐bp) DNA fragments have been used to enable the detection of as wide a range of macroalgal taxa as possible, but these offer a limited taxonomic resolution for some taxa. Advances in DNA sequencing technology that enable the sequencing of longer DNA fragments will provide more detailed identification (Anglès d'Auriac et al, 2021). Together with the population of public DNA databases with sequences of as many taxa as possible, the accuracy of taxonomic identification via eDNA studies will also increase (Queirós et al, 2019).…”