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The importance of dead seagrass (Posidonia oceanica)matte as a biogeochemical sink

The importance of dead seagrass (Posidonia oceanica)matte as a biogeochemical sink
The importance of dead seagrass (Posidonia oceanica)matte as a biogeochemical sink
We assessed the potential of dead seagrass Posidonia oceanica matte to act as a biogeochemical sink and provide a coherent archive of environmental change in a degraded area of the Mediterranean Sea (Augusta Bay, Italy). Change in sediment properties (dry bulk density, grain size), concentration of elements (Corg, Cinorg, N, Hg) and stable isotope ratios (δ13C, δ 15N) with sediment depth were measured in dead P. oceanica matte and unvegetated (bare) sediments in the polluted area, and an adjacent P. oceanica meadow. Principal Component Analysis (PCA) revealed a clear clustering by habitat, which explained 72% of variability in our samples and was driven mainly by the accumulation of N and Hg in finer sediments of the dead matte. Assessment of the temporal trends of Corg, N and Hg concentrations in the dead matte revealed changes in the accumulation of these elements over the last 120 years, with an increase following the onset of industrial activities 65 y BP (i.e., yr. 1950) that was sustained even after seagrass loss around 35 y BP. Despite a decrease in Hg concentrations in the early 1980s following the onset of pollution abatement, overall Hg levels were 2-fold higher in the local post-industrial period, with a Hg enrichment factor of 3.5 in the dead matte. Mean stocks of Corg, N and Hg in 25 cm thick sediment deposits (4.08 ± 2.10 kg Corg m-2, 0.14 ± 0.04 kg N m-2, 0.19 ± 0.04 g Hg m-2) and accumulation in the last 120 yr (35.3 ± 19.6 g Corg m-2 y-1, 1.2 ± 0.4 g N m-2 y-1, 0.0017 ± 0.0004 g Hg m-2 y-1) were higher in the dead matte than bare sediment or adjacent P. oceanica meadow. Our results indicate that dead P. oceanica matte maintained its potential as a biogeochemical sink and, like its living counterpart, dead matte can serve as an effective archive to allow for reconstructing environmental change in coastal areas of the Mediterranean where severe perturbations have led to P. oceanica loss. Appropriate management for contaminated areas should be prioritized to prevent release of pollutants and carbon from dead mattes.
anthropogenic impact, blue carbon, contamination, nutrient filters, seagrass archives, seagrass degradation
2296-7745
Apostolaki, Eugenia T.
12482858-e847-43fb-8326-d1d85183270e
Caviglia, Laura
d95e460e-bfd1-4301-ab11-62ab9e0579a9
Santinelli, Veronica
015a3d4c-6a63-4b51-85c6-87a0f637505b
Cundy, Andrew B.
994fdc96-2dce-40f4-b74b-dc638286eb08
Tramati, Cecilia D.
3e254e1e-7fb4-4c2d-b6a1-d1593e76ea6a
Mazzola, Antonio
02eaeb38-3456-45ac-9e13-8ead7b2900eb
Vizzini, Salvatrice
3a3374f8-0dbf-4ddc-b23a-b5008939df53
Apostolaki, Eugenia T.
12482858-e847-43fb-8326-d1d85183270e
Caviglia, Laura
d95e460e-bfd1-4301-ab11-62ab9e0579a9
Santinelli, Veronica
015a3d4c-6a63-4b51-85c6-87a0f637505b
Cundy, Andrew B.
994fdc96-2dce-40f4-b74b-dc638286eb08
Tramati, Cecilia D.
3e254e1e-7fb4-4c2d-b6a1-d1593e76ea6a
Mazzola, Antonio
02eaeb38-3456-45ac-9e13-8ead7b2900eb
Vizzini, Salvatrice
3a3374f8-0dbf-4ddc-b23a-b5008939df53

Apostolaki, Eugenia T., Caviglia, Laura, Santinelli, Veronica, Cundy, Andrew B., Tramati, Cecilia D., Mazzola, Antonio and Vizzini, Salvatrice (2022) The importance of dead seagrass (Posidonia oceanica)matte as a biogeochemical sink. Frontiers in Marine Science, 9, [861998]. (doi:10.3389/fmars.2022.861998).

Record type: Article

Abstract

We assessed the potential of dead seagrass Posidonia oceanica matte to act as a biogeochemical sink and provide a coherent archive of environmental change in a degraded area of the Mediterranean Sea (Augusta Bay, Italy). Change in sediment properties (dry bulk density, grain size), concentration of elements (Corg, Cinorg, N, Hg) and stable isotope ratios (δ13C, δ 15N) with sediment depth were measured in dead P. oceanica matte and unvegetated (bare) sediments in the polluted area, and an adjacent P. oceanica meadow. Principal Component Analysis (PCA) revealed a clear clustering by habitat, which explained 72% of variability in our samples and was driven mainly by the accumulation of N and Hg in finer sediments of the dead matte. Assessment of the temporal trends of Corg, N and Hg concentrations in the dead matte revealed changes in the accumulation of these elements over the last 120 years, with an increase following the onset of industrial activities 65 y BP (i.e., yr. 1950) that was sustained even after seagrass loss around 35 y BP. Despite a decrease in Hg concentrations in the early 1980s following the onset of pollution abatement, overall Hg levels were 2-fold higher in the local post-industrial period, with a Hg enrichment factor of 3.5 in the dead matte. Mean stocks of Corg, N and Hg in 25 cm thick sediment deposits (4.08 ± 2.10 kg Corg m-2, 0.14 ± 0.04 kg N m-2, 0.19 ± 0.04 g Hg m-2) and accumulation in the last 120 yr (35.3 ± 19.6 g Corg m-2 y-1, 1.2 ± 0.4 g N m-2 y-1, 0.0017 ± 0.0004 g Hg m-2 y-1) were higher in the dead matte than bare sediment or adjacent P. oceanica meadow. Our results indicate that dead P. oceanica matte maintained its potential as a biogeochemical sink and, like its living counterpart, dead matte can serve as an effective archive to allow for reconstructing environmental change in coastal areas of the Mediterranean where severe perturbations have led to P. oceanica loss. Appropriate management for contaminated areas should be prioritized to prevent release of pollutants and carbon from dead mattes.

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Accepted/In Press date: 7 March 2022
Published date: 28 March 2022
Additional Information: Funding Information: We thank Andrea Savona, Antonino M. Vaccaro and Rossella Di Leonardo for sampling, Adele E. Aleo for helping with laboratory analyses, and Victoria Litsi Mizan for helping with the graphical representation of the results. AC is grateful to colleagues in GAU-Radioanalytical, University of Southampton, for radiochemical analysis. We highly acknowledge constructive criticism by the three reviewers. Funding Information: The study was funded by the project TETIDE, PON01_03112, Italian Ministry of University and Research (MIUR) and by the project Marine Hazard, PON03PE_00203_1, Italian Ministry of Education, University and Research (MIUR). Publisher Copyright: Copyright © 2022 Apostolaki, Caviglia, Santinelli, Cundy, Tramati, Mazzola and Vizzini.
Keywords: anthropogenic impact, blue carbon, contamination, nutrient filters, seagrass archives, seagrass degradation

Identifiers

Local EPrints ID: 457314
URI: http://eprints.soton.ac.uk/id/eprint/457314
ISSN: 2296-7745
PURE UUID: c96dcff7-64cf-4da1-b2f6-4506acd2adf0
ORCID for Andrew B. Cundy: ORCID iD orcid.org/0000-0003-4368-2569

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Date deposited: 01 Jun 2022 16:30
Last modified: 25 Jan 2023 02:48

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Contributors

Author: Eugenia T. Apostolaki
Author: Laura Caviglia
Author: Veronica Santinelli
Author: Andrew B. Cundy ORCID iD
Author: Cecilia D. Tramati
Author: Antonio Mazzola
Author: Salvatrice Vizzini

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