Aarhus University Seal / Aarhus Universitets segl

Om CARMA

Background

Seagrass meadows accumulate carbon (C) in sedimentary deposits under the meadows and are widely acknowledged hotspots of C-sequestration with their C-sink capacity readily measured from analyses of sediment cores taken in the meadows. Seaweed forests have, by contrast, typically been ignored as C-sinks, as they typically grow on rocky shores where carbon does not accumulate, thus preventing use of conventional methods to estimate their role in sequestration. Yet, a significant fraction of seaweed production, estimated at 173 Tg C yr-1, is exported and sequestered in C-reservoirs beyond their habitat. But, direct estimates of the contribution of seaweed forests to C-sequestration, and their C-sink capacity, are lacking for the Arctic and elsewhere.

In the Arctic, seaweed forests and seagrass meadows are projected to expand with warming and reduced ice cover and, as a result, Arctic blue C-sinks may increase. With the Arctic representing 34% of the global shoreline, and the predominant rocky shores providing suitable habitat, the potential for expansion of Arctic marine forests and their contribution to blue C is therefore significant.

Methods

We apply an interdisciplinary approach at the intersection of marine ecology, geology, oceanography, remote sensing, biochemistry and genetics, with Greenland as a case study. We do so by coupling new conceptual advances with the use of newly developed techniques for tracing carbon (C) from marine forests in marine sediments (e.g. eDNA & amino acid isotopic signatures). We combine measurements of bulk C, isotopic signatures of bulk C/amino acids and eDNA to resolve the sources of C to Arctic sediments.

Environmental DNA (eDNA)

A novel approach to identify macroalgae in environmental samples is based on DNA metabarcoding. Environmental DNA (eDNA) represents DNA extracted from environmental samples (e.g. soil, water, air) and metabarcoding of eDNA enables us to get a wide palette of taxonomic information about the environmental sample. The total DNA from an environmental sample holds both intra- and extracellular DNA traces. Intracellular is the DNA inside active or dormant cells, while the extracellular DNA have been released to the environment from decaying cells or sloughed material (i.e. tissue, feces or other secretion types).

Isotopic signatures

Tekst kommer - Sarah skriver

Remote sensing

 Tekst kommer - Sarah skriver

Work packages

WP 1. Fingerprinting C from marine forests in Greenland sedimentary C-stocks

Billedet skal skiftes

Tasks:

  1. Test and compare state-of-the-art tracing techniques (eDNA, bulk and amino acid isotopic signatures) for fingerprinting C from marine forests in marine sediments.
  2. Fingerprint C from marine forests in surface samples and 5-7 deep cores (ca. 50 sections of each) with state-of-the-art tracing techniques.
  3. Investigate potential of state-of-the-art tracing techniques to quantify C from marine forests in marine sediments.

WP 2. Assessing the C-sink capacity of Greenland marine forests along climatic gradients

Billedet skal skiftes

Tasks:

  1. Derive contemporary and long-term C-sequestration rates from Greenland, using 210Pb and 14C-datings, combined with estimates on density and C-content.
  2. Assess latitudinal and long-term changes in the contribution of marine forests to the organic C pool using sediment cores as historical archives and applying state-of-the-art tracing techniques from WP 1.
  3. Reconstruct the chronology of potential changes in the importance of marine forests in relation to past climate regimes in order to compare the importance of marine forests for C-sequestration during past and recent warming periods.
  4. D)Derive temperature thresholds for the presence of Greenland marine forests and reconstruct the sequence of their appearance across latitudinal ranges during warming periods, by coupling information on vegetation tracers and dating with existing evidence of past climate conditions derived from climate proxies.

WP 3. Developing first-order estimates of the distribution area and C-sequestration potential of Greenland kelp forests

Illustration / Photo: Scott Bennett ©t
Tidal area in Greenland / Photo: Scott Bennett ©

Tasks:

  1. Develop first-order map of Greenland kelp forests using satellite imagery, ocean models, and historical in situ data as inputs to an ecological model.
  2. Calculate total- and exported kelp production along latitude degree bands, combining published relationships between kelp growth and latitude along the Greenland coast with estimates of density and biomass, and by using different export estimates.
  3. Calculate C-export and -sequestration associated with Greenland kelp forests.
  4. Detect drifting kelp mats by modifying algorithms developed to detect Sargassum.
  5. Investigate ocean currents in transporting kelp to remote deposition areas using ocean models and Lagrangian particle tracking techniques.