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Macroalgal habitats support a sustained flux of floating biomass but limited carbon export beyond a Greenland fjord.
Sci Total Environ. 2023 May 10; 872:162224.ST

Abstract

Despite growing attention on the contribution of macroalgae to carbon cycling and sequestration (blue carbon), more observational data is needed to constrain current estimates. In this study, we estimate the floating macroalgal carbon flux within and beyond a large sub-Arctic fjord system, Nuup Kangerlua, Greenland, which could potentially reach carbon sinks. Our study estimates 1) the fjord-scale area with macroalgal coverage and barrens caused by sea urchin grazing, 2) the floating macroalgal biomass in the fjord, and 3) the annual export flux of floating macroalgae out of the fjord system. ROV surveys documented that macroalgal habitats cover 32 % of the seafloor within the photic zone (0-30 m) with an average coverage of 39.6, 22, and 7.2 % in the depth intervals 0-10, 10-20, and 20-30 m, respectively. 15 % of the area suitable for macroalgae was denuded by sea urchin grazing. Floating macroalgae were common with an average biomass of 55 kg wet weight km-2. Densities and species composition varied seasonally with the highest levels after storms. The floating biomass was composed of intertidal macroalgal species (58 %) (Fucus vesiculosus, Fucus distichus, and Ascophyllum nodosum) and kelps (42 %) (Saccharina longicruris, S. latissima, and Alaria esculenta). We deployed surface GPS drifters to simulate floating macroalgal trajectories and velocity. Data indicated that 80 % of the floating biomass is retained in the fjord where its fate in relation to long-term sequestration is unknown. Export beyond the fjord was limited and indicated an annual floating macroalgal export beyond the fjord of only 6.92 t C yr-1, which is equal to ~0.02 % of the annual net primary production. Our findings suggest that floating macroalgae support a limited blue carbon potential beyond this fjord and that future research should focus on the fate of retained floating macroalgae and subsurface export to resolve the connectivity between macroalgal habitats and long-term carbon sinks.

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Publisher Full Text (DOI)

Authors+Show Affiliations

Ager TG
Department of Biology, Aarhus University, 8000 Aarhus C, Denmark; Department of Ecoscience, Aarhus University, 8000 Aarhus C, Denmark. Electronic address: 201708279@post.au.dk.
Krause-Jensen D
Department of Ecoscience, Aarhus University, 8000 Aarhus C, Denmark; Arctic Research Center, Aarhus University, 8000 Aarhus C, Denmark.
Olesen B
Department of Biology, Aarhus University, 8000 Aarhus C, Denmark; Arctic Research Center, Aarhus University, 8000 Aarhus C, Denmark.
Carlson DF
Optical Oceanography, Institute of Carbon Cycles, Helmholtz-Zentrum Hereon, 21502 Geesthacht, Germany.
Winding MHS
Greenland Climate Research Centre, Greenland Institute of Natural Resources, 3900 Nuuk, Greenland.
Sejr MK
Department of Ecoscience, Aarhus University, 8000 Aarhus C, Denmark; Arctic Research Center, Aarhus University, 8000 Aarhus C, Denmark.

MeSH

BiomassEstuariesCarbonGreenlandEcosystemSeaweedFucus

Pub Type(s)

Journal Article

Language

eng

PubMed ID

36804986

Citation

Ager, Thomas Gjerluff, et al. "Macroalgal Habitats Support a Sustained Flux of Floating Biomass but Limited Carbon Export Beyond a Greenland Fjord." The Science of the Total Environment, vol. 872, 2023, p. 162224.
Ager TG, Krause-Jensen D, Olesen B, et al. Macroalgal habitats support a sustained flux of floating biomass but limited carbon export beyond a Greenland fjord. Sci Total Environ. 2023;872:162224.
Ager, T. G., Krause-Jensen, D., Olesen, B., Carlson, D. F., Winding, M. H. S., & Sejr, M. K. (2023). Macroalgal habitats support a sustained flux of floating biomass but limited carbon export beyond a Greenland fjord. The Science of the Total Environment, 872, 162224. https://doi.org/10.1016/j.scitotenv.2023.162224
Ager TG, et al. Macroalgal Habitats Support a Sustained Flux of Floating Biomass but Limited Carbon Export Beyond a Greenland Fjord. Sci Total Environ. 2023 May 10;872:162224. PubMed PMID: 36804986.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Macroalgal habitats support a sustained flux of floating biomass but limited carbon export beyond a Greenland fjord. AU - Ager,Thomas Gjerluff, AU - Krause-Jensen,Dorte, AU - Olesen,Birgit, AU - Carlson,Daniel F, AU - Winding,Mie Hylstofte Sichlau, AU - Sejr,Mikael K, Y1 - 2023/02/15/ PY - 2022/09/01/received PY - 2023/01/30/revised PY - 2023/02/09/accepted PY - 2023/2/23/pubmed PY - 2023/3/17/medline PY - 2023/2/22/entrez KW - Arctic KW - Blue carbon KW - Carbon export KW - Floating macroalgae KW - Macroalgae SP - 162224 EP - 162224 JF - The Science of the total environment JO - Sci Total Environ VL - 872 N2 - Despite growing attention on the contribution of macroalgae to carbon cycling and sequestration (blue carbon), more observational data is needed to constrain current estimates. In this study, we estimate the floating macroalgal carbon flux within and beyond a large sub-Arctic fjord system, Nuup Kangerlua, Greenland, which could potentially reach carbon sinks. Our study estimates 1) the fjord-scale area with macroalgal coverage and barrens caused by sea urchin grazing, 2) the floating macroalgal biomass in the fjord, and 3) the annual export flux of floating macroalgae out of the fjord system. ROV surveys documented that macroalgal habitats cover 32 % of the seafloor within the photic zone (0-30 m) with an average coverage of 39.6, 22, and 7.2 % in the depth intervals 0-10, 10-20, and 20-30 m, respectively. 15 % of the area suitable for macroalgae was denuded by sea urchin grazing. Floating macroalgae were common with an average biomass of 55 kg wet weight km-2. Densities and species composition varied seasonally with the highest levels after storms. The floating biomass was composed of intertidal macroalgal species (58 %) (Fucus vesiculosus, Fucus distichus, and Ascophyllum nodosum) and kelps (42 %) (Saccharina longicruris, S. latissima, and Alaria esculenta). We deployed surface GPS drifters to simulate floating macroalgal trajectories and velocity. Data indicated that 80 % of the floating biomass is retained in the fjord where its fate in relation to long-term sequestration is unknown. Export beyond the fjord was limited and indicated an annual floating macroalgal export beyond the fjord of only 6.92 t C yr-1, which is equal to ~0.02 % of the annual net primary production. Our findings suggest that floating macroalgae support a limited blue carbon potential beyond this fjord and that future research should focus on the fate of retained floating macroalgae and subsurface export to resolve the connectivity between macroalgal habitats and long-term carbon sinks. SN - 1879-1026 UR - https://www.unboundmedicine.com/medline/citation/36804986/Macroalgal_habitats_support_a_sustained_flux_of_floating_biomass_but_limited_carbon_export_beyond_a_Greenland_fjord_ DB - PRIME DP - Unbound Medicine ER -