scholarly journals Seagrass community-level controls over organic carbon storage are constrained by geophysical attributes within meadows of Zanzibar, Tanzania

2018 ◽  
Vol 15 (14) ◽  
pp. 4609-4626 ◽  
Author(s):  
Elizabeth Fay Belshe ◽  
Dieuwke Hoeijmakers ◽  
Natalia Herran ◽  
Matern Mtolera ◽  
Mirta Teichberg
Keyword(s):  
Organic Carbon ◽  
Plant Traits ◽  
Sediment Cores ◽  
Belowground Biomass ◽  
Shoot Density ◽  
Seagrass Meadows ◽  
Seagrass Community ◽  
Seagrass Ecosystems ◽  
Organic Carbon Storage ◽  
Thalassodendron Ciliatum

Abstract. The aim of this work was to explore the feasibility of using plant functional traits to identify differences in sediment organic carbon (OC) storage within seagrass meadows. At 19 sites within three seagrass meadows in the coastal waters of Zanzibar, Tanzania, species cover was estimated along with three community traits hypothesized to influence sediment OC storage (above and belowground biomass, seagrass tissue nitrogen content, and shoot density). Sediments within four biogeographic zones (fore reef, reef flat, tidal channel, and seagrass meadow) of the landscape were characterized, and sediment cores were collected within seagrass meadows to quantify OC storage in the top 25 cm and top meter of the sediment. We identified five distinct seagrass communities that had notable differences in the plant traits, which were all residing within a thin veneer (ranging from 19 to 78 cm thick) of poorly sorted, medium to coarsely grained carbonate sands on top of carbonate rock. One community (B), dominated by Thalassodendron ciliatum, contained high amounts of above (972±74 g DW m−2) and belowground (682±392 g DW m−2) biomass composed of low-elemental-quality tissues (leaf C : N = 24.5; rhizome C : N = 97). While another community (C), dominated by small-bodied ephemeral seagrass species, had significantly higher shoot density (4178 shoots m−2). However, these traits did not translate into differences in sediment OC storage and across all communities the percentage of OC within sediments was similar and low (ranging from 0.15 % to 0.75 %), as was the estimated OC storage in the top 25 cm (14.1±2.2 Mg C ha−1) and top meter (33.9±7.7 Mg C ha−1) of sediment. These stock estimates are considerably lower than the global average (194.2±20.2 Mg C ha−1) reported for other seagrass ecosystems and are on the lower end of the range of estimates reported for the tropical Indo-Pacific bioregion (1.9 to 293 Mg C ha−1). The uniformly low OC storage across communities, despite large inputs of low-quality belowground tissues in community B, indicates that the geophysical conditions of the coarse, shallow sediments at our sites were not conducive to OC stabilization and outweighed any variation in the quantity or quality of seagrass litter inputs. These results add to a growing body of evidence showing that geophysical conditions of the sediment modulate the importance of plant traits in regards to retention of OC within blue carbon ecosystems and cautions against the use of plant traits as a proxy for sediment OC storage across all seagrass ecosystems.

scholarly journals Seagrass community-level controls over organic carbon storage are constrained by geophysical attributes within meadows of Zanzibar, Tanzania

2017 ◽  
Author(s):  
E. Fay Belshe ◽  
Dieuwke Hoeijmakers ◽  
Natalia Herran ◽  
Matern Mtolera ◽  
Mirta Teichberg
Keyword(s):  
Organic Carbon ◽  
Carbon Storage ◽  
Plant Traits ◽  
Belowground Biomass ◽  
Shoot Density ◽  
Plant Litter ◽  
Coarse Grained ◽  
Seagrass Meadows ◽  
Seagrass Ecosystems ◽  
Sediment Carbon

Abstract. The aim of this work was to explore the feasibility of using seagrass functional traits to predict differences in sediment carbon storage. At 19 sites within highly diverse seagrass meadows of Zanzibar, Tanzania, species cover was estimated along with three community traits hypothesized to influence sediment carbon storage (amount of above and belowground biomass, seagrass tissue nitrogen content, and shoot density). We identified five distinct seagrass communities that had notable variations in key plant traits but these differences did not translate into differences is sediment organic carbon (OC) storage. Across all communities, sediment OC was very low (ranging from 0.15 % to 0.75 %) and there were no differences in OC storage among communities, which was considerably lower (33.97.7 Mg C ha−1) than the global average (194.220.2 Mg C ha−1) reported for other seagrass ecosystems. In spite of high seagrass diversity and clear zonation among plant communities, sediments in all communities were shallow (ranging from 19 to 78 cm) and composed of medium-coarse grained carbonate sand on top of carbonate rock. We propose that geophysical conditions of the sediment were not conducive to OC stabilization, and outweighed any variation in the quantity or quality of plant litter inputs, ultimately leading to low OC storage within all seagrass communities. This highlights the complexity of OC cycling in seagrass ecosystems and cautions against the use of plant traits as a proxy for OC storage across all seagrass ecosystems.

scholarly journals Variation of carbon contents in eelgrass ( Zostera marina ) sediments implied from depth profiles

2019 ◽  
Vol 15 (6) ◽  
pp. 20180831 ◽  
Author(s):  
Theodor Kindeberg ◽  
Emilia Röhr ◽  
Per-Olav Moksnes ◽  
Christoffer Boström ◽  
Marianne Holmer
Keyword(s):  
Organic Carbon ◽  
Zostera Marina ◽  
Large Scale ◽  
Environmental Changes ◽  
Sediment Cores ◽  
Depth Profiles ◽  
Seagrass Meadows ◽  
Spatio Temporal ◽  
Organic Carbon Storage ◽  
Eelgrass Beds

Seagrass meadows are able to store significant amounts of organic carbon in their underlying sediment, but global estimates are uncertain partly owing to spatio-temporal heterogeneity between and within areas and species. In order to provide robust estimates, there is a need to better understand the fate of, and mechanisms behind, organic carbon storage. In this observational study, we analyse a suite of biotic and abiotic parameters in sediment cores from 47 different eelgrass ( Zostera marina ) beds spanning the distributional range of the Northern Hemisphere. Depth profiles of particulate organic carbon (POC) revealed three patterns of vertical distribution where POC either increased, decreased or showed no pattern with sediment depth. These categories exhibited distinct profiles of δ 13 C and C:N ratios, where high POC profiles had a proportionally larger storage of eelgrass-derived material whereas low POC profiles were dominated by phytoplanktonic and macroalgal material. However, high POC did not always translate into high carbon density. Nevertheless, this large-scale dataset provides evidence that the variability in organic matter source in response to natural and anthropogenic environmental changes affects the potential role of eelgrass beds as POC sinks, particularly where eelgrass decline is observed.

Ten years of conservation efforts enhance seagrass cover and carbon storage in Thailand

2018 ◽  
Vol 61 (5) ◽  
pp. 441-451 ◽  
Author(s):  
Ekkalak Rattanachot ◽  
Milica Stankovic ◽  
Supaphon Aongsara ◽  
Anchana Prathep
Keyword(s):  
Organic Carbon ◽  
Carbon Storage ◽  
Seagrass Meadow ◽  
Seagrass Meadows ◽  
Rate Of Increase ◽  
Southern Thailand ◽  
Seagrass Cover ◽  
Conservation Projects ◽  
Organic Carbon Storage ◽  
Total Coverage

Abstract Seagrasses are known as engineering ecosystems that play important roles in coastal environments. Globally, seagrass areas have been declining, and many conservation projects have been carried out to prevent further decline. The goal of this work was to determine how successful conservation efforts have been in a seagrass meadow at Koh Tha Rai in the Nakhon Si Thammarat Province of southern Thailand in terms of meadow extent, coverage and organic carbon storage. A study was conducted in 2017 and compared to a previous study from 2006 to determine the effects of the various conservation efforts devoted to this area. The results show that the total seagrass area increased by 0.7 ha with a rate of increase of approximately 0.06 ha year−1. The total coverage of seagrass increased by approximately 3 times. The organic carbon in existing seagrass meadows (2006) was 53.35 Mg ha−1, while growth was 32.34 Mg ha−1 in the areas of new seagrass. Moreover, the total organic carbon storage in the sediment increased by 26.86 MgC from 2006 to 2017 (from 211.60 MgC to 235.46 MgC). In conclusion, this study demonstrated the importance of successful conservation efforts in terms of increasing seagrass meadow areas, seagrass coverage and carbon storage within the meadow.

scholarly journals Can mud (silt and clay) concentration be used to predict soil organic carbon content within seagrass ecosystems?

2016 ◽  
Author(s):  
O. Serrano ◽  
P. S. Lavery ◽  
C. M. Duarte ◽  
G. A. Kendrick ◽  
A. Calafat ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Carbon Content ◽  
Clay Content ◽  
Cost Effective ◽  
Blue Carbon ◽  
Organic Carbon Content ◽  
Terrestrial Organic Matter ◽  
Seagrass Meadows ◽  
Clay Concentration ◽  
Seagrass Ecosystems

Abstract. The emerging field of blue carbon science is seeking cost-effective ways to estimate the organic carbon content of soils that are bound by coastal vegetated ecosystems. Organic carbon (Corg) content in terrestrial soils and marine sediments has been correlated with mud content (i.e. silt and clay), however, empirical tests of this theory are lacking for coastal vegetated ecosystems. Here, we compiled data (n = 1345) on the relationship between Corg and mud (i.e. silt and clay, particle sizes <63 μm) contents in seagrass ecosystems (79 cores) and adjacent bare sediments (21 cores) to address whether mud can be used to predict soil Corg content. We also combined these data with the δ13C signatures of the soil Corg to understand the sources of Corg stores. The results showed that mud is positively correlated with soil Corg content only when the contribution of seagrass-derived Corg to the sedimentary Corg pool is relatively low, such as in small and fast growing meadows of the genera Zostera, Halodule and Halophila, and in bare sediments adjacent to seagrass ecosystems. In large and long-living seagrass meadows of the genera Posidonia and Amphibolis there was a lack of, or poor relationship between mud and soil Corg content, related to a higher contribution of seagrass-derived Corg to the sedimentary Corg pool in these meadows. The relative high soil Corg contents with relatively low mud contents (i.e. mud-Corg saturation) together with significant allochthonous inputs of terrestrial organic matter could overall disrupt the correlation expected between soil Corg and mud contents. This study shows that mud (i.e. silt and clay content) is not a universal proxy for blue carbon content in seagrass ecosystems, and therefore should not be applied generally across all seagrass habitats. Mud content can only be used as a proxy to estimate soil Corg content for scaling up purposes when opportunistic and/or low biomass seagrass species (i.e. Zostera, Halodule and Halophila) are present (explaining 34 to 91% of variability), and in bare sediments (explaining 78% of the variability).

scholarly journals Can mud (silt and clay) concentration be used to predict soil organic carbon content within seagrass ecosystems?

2016 ◽  
Vol 13 (17) ◽  
pp. 4915-4926 ◽  
Author(s):  
Oscar Serrano ◽  
Paul S. Lavery ◽  
Carlos M. Duarte ◽  
Gary A. Kendrick ◽  
Antoni Calafat ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Carbon Content ◽  
Low Cost ◽  
Cost Effective ◽  
Scaling Up ◽  
Blue Carbon ◽  
Organic Carbon Content ◽  
Terrestrial Organic Matter ◽  
Seagrass Meadows ◽  
Seagrass Ecosystems

Abstract. The emerging field of blue carbon science is seeking cost-effective ways to estimate the organic carbon content of soils that are bound by coastal vegetated ecosystems. Organic carbon (Corg) content in terrestrial soils and marine sediments has been correlated with mud content (i.e., silt and clay, particle sizes < 63 µm), however, empirical tests of this theory are lacking for coastal vegetated ecosystems. Here, we compiled data (n =  1345) on the relationship between Corg and mud contents in seagrass ecosystems (79 cores) and adjacent bare sediments (21 cores) to address whether mud can be used to predict soil Corg content. We also combined these data with the δ13C signatures of the soil Corg to understand the sources of Corg stores. The results showed that mud is positively correlated with soil Corg content only when the contribution of seagrass-derived Corg to the sedimentary Corg pool is relatively low, such as in small and fast-growing meadows of the genera Zostera, Halodule and Halophila, and in bare sediments adjacent to seagrass ecosystems. In large and long-living seagrass meadows of the genera Posidonia and Amphibolis there was a lack of, or poor relationship between mud and soil Corg content, related to a higher contribution of seagrass-derived Corg to the sedimentary Corg pool in these meadows. The relatively high soil Corg contents with relatively low mud contents (e.g., mud-Corg saturation) in bare sediments and Zostera, Halodule and Halophila meadows was related to significant allochthonous inputs of terrestrial organic matter, while higher contribution of seagrass detritus in Amphibolis and Posidonia meadows disrupted the correlation expected between soil Corg and mud contents. This study shows that mud is not a universal proxy for blue carbon content in seagrass ecosystems, and therefore should not be applied generally across all seagrass habitats. Mud content can only be used as a proxy to estimate soil Corg content for scaling up purposes when opportunistic and/or low biomass seagrass species (i.e., Zostera, Halodule and Halophila) are present (explaining 34 to 91 % of variability), and in bare sediments (explaining 78 % of the variability). The results obtained could enable robust scaling up exercises at a low cost as part of blue carbon stock assessments.

scholarly journals Contributions of the direct supply of belowground seagrass detritus and trapping of suspended organic matter to the sedimentary organic carbon stock in seagrass meadows

2018 ◽  
Vol 15 (13) ◽  
pp. 4033-4045 ◽  
Author(s):  
Toko Tanaya ◽  
Kenta Watanabe ◽  
Shoji Yamamoto ◽  
Chuki Hongo ◽  
Hajime Kayanne ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Belowground Biomass ◽  
Blue Carbon ◽  
Back Reef ◽  
Major Mechanism ◽  
Seagrass Meadows ◽  
Sedimentary Organic Carbon ◽  
Seagrass Biomass ◽  
Dead Plant

Abstract. Carbon captured by marine living organisms is called “blue carbon”, and seagrass meadows are a dominant blue carbon sink. However, our knowledge of how seagrass increases sedimentary organic carbon (OC) stocks is limited. We investigated two pathways of OC accumulation: trapping of organic matter in the water column and the direct supply of belowground seagrass detritus. We developed a new type of box corer to facilitate the retrieval of intact cores that preserve the structures of both sediments (including coarse sediments and dead plant structures) and live seagrasses. We measured seagrass density, total OC mass (OCtotal) (live seagrass OC biomass (OCbio) + sedimentary OC mass (OCsed)), and the stable carbon isotope ratio (δ13C) of OCsed and its potential OC sources at Thalassia hemprichii dominated back-reef and Enhalus acoroides dominated estuarine sites in the tropical Indo-Pacific region. At points with vegetation, OCbio accounted for 25 % and OCsed for 75 % of OCtotal; this contribution of OCbio to OCtotal is higher than in globally compiled data. Belowground detritus accounted for ∼ 90 % of the OC mass of dead plant structures (> 2 mm in size) (OCdead). At the back-reef site, belowground seagrass biomass, OCdead, and δ13C of OCsed (δ13Csed) were positively correlated with OCsed, indicating that the direct supply of belowground seagrass detritus is a major mechanism of OCsed accumulation. At the estuarine site, aboveground seagrass biomass was positively correlated with OCsed but δ13Csed did not correlate with OCsed, indicating that trapping of suspended OC by seagrass leaves is a major mechanism of OCsed accumulation there. We inferred that the relative importance of these two pathways may depend on the supply (productivity) of belowground biomass. Our results indicate that belowground biomass productivity of seagrass meadows, in addition to their aboveground morphological complexity, is an important factor controlling their OC stock. Consideration of this factor will improve global blue carbon estimates.

scholarly journals Seagrass contribution to blue carbon in a shallow karstic coastal area of the Gulf of Mexico

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e12109
Author(s):  
Tania C. Cota Lucero ◽  
Jorge A. Herrera-Silveira
Keyword(s):  
Organic Carbon ◽  
Carbon Stock ◽  
Carbon Sink ◽  
Anthropogenic Impacts ◽  
Regional Scale ◽  
Mitigation Strategies ◽  
Conservation Strategies ◽  
Seagrass Meadows ◽  
Seagrass Community ◽  
Organic Carbon Stock

Seagrass meadows provide multiple ecosystem services, including carbon sequestration. However, seagrass meadows are among the most threatened ecosystems worldwide. Determining the magnitude of the carbon stocks in seagrass meadows at the regional scale allows for the estimation of their global magnitude and identification of their importance in regional environmental mitigation strategies. The objective of the present study was to determine the structure of seagrass meadows in the Los Petenes Biosfera Reserve (LPBR) and evaluate their contributions to sinks of carbon in this system, located in Yucatan, which is considered the region with the largest seagrass extension in Mexico. Analyses of the seagrass meadows were executed following standardized protocols (spectral analysis, and isotope and carbon stock analyses). The LPBR stores an average of 2.2 ± 1.7 Mg C ha−1 in living biomass and 318 ± 215 Mg C ha−1 in sediment (top 1 m), and this carbon stock decreases with water depth. The seagrass community extends 149,613 ha, which represents the largest organic carbon stock (47 Tg C) documented in seagrass meadows in Mexico. Macroalgae and seagrass represent 76% of the organic carbon stored in sediment. If LPBR seagrass meadows are lost due to natural or anthropogenic impacts, 173 Tg CO2eqemissions could be released, which corresponds to the emissions generated by fossil fuel combustion of 27% of the current Mexican population. This information emphasizes the importance of seagrass meadows as a carbon sink in the region and their contribution to climate change mitigation, thus allowing for the implementation of necessary conservation strategies.

scholarly journals Contributions of the direct supply of belowground seagrass detritus and trapping of suspended organic matter to the sedimentary organic carbon stock in seagrass meadows

2017 ◽  
Author(s):  
Toko Tanaya ◽  
Kenta Watanabe ◽  
Shoji Yamamoto ◽  
Chuki Hongo ◽  
Hajime Kayanne ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Belowground Biomass ◽  
Blue Carbon ◽  
Back Reef ◽  
Major Mechanism ◽  
Seagrass Meadows ◽  
Sedimentary Organic Carbon ◽  
Seagrass Biomass ◽  
Dead Plant

Abstract. Carbon captured by marine living organisms is called blue carbon, and seagrass meadows are a dominant blue carbon sink. However, our knowledge of how seagrass increases sedimentary organic carbon (OC) stocks is limited. We investigated two pathways of OC enrichment: trapping of organic matter in the water column and the direct supply of belowground seagrass detritus. We developed a new type of box corer to facilitate the retrieval of intact cores that preserve the structures of both sediments (including coarse sediments and dead plant structures) and live seagrass bodies. We measured seagrass density, total OC mass (OCtotal) [= live seagrass OC biomass (OCbio) + sedimentary OC mass (OCsed)], and the stable carbon isotope ratio (δ13C) of OCsed at back-reef and estuarine sites in the tropical Indo-Pacific region. OCbio accounted for 19 % and OCsed for 81 % of OCtotal; this contribution of OCbio to OCtotal is the highest in globally compiled data. Belowground detritus accounted for ~ 90 % of the OC mass of dead plant structures (> 2 mm in size) (OCdead). At the back-reef site, belowground seagrass biomass, OCdead, and δ13C of OCsed (δ13Csed) were positively correlated with OCsed, indicating that the direct supply of belowground seagrass detritus is a major mechanism of OCsed enrichment. At the estuarine site, aboveground seagrass biomass was positively correlated with OCsed but δ13Csed did not correlate with OCsed, indicating that trapping of suspended OC by seagrass leaves is a major mechanism of OCsed enrichment there. We inferred that the relative importance of these two pathways may depend on the supply (productivity) of belowground biomass. Our results indicate that belowground biomass productivity of seagrass meadows, in addition to their aboveground morphological complexity, is an important factor controlling their OC stock. Consideration of this factor will improve global blue-carbon estimates.

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