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Lin J, He S, Liu X, Huang Z, Li M, Chen B, Hu W. Identifying conservation and restoration priorities for degraded coastal wetland vegetations: Integrating species distribution model and GeoDetector. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 906:167491. [PMID: 37778559 DOI: 10.1016/j.scitotenv.2023.167491] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 08/20/2023] [Accepted: 09/28/2023] [Indexed: 10/03/2023]
Abstract
The ongoing degradation of seagrass and seaweed is of global concern. Comprehending the spatial distribution of these wetland vegetation types and the threats they face becomes critical for effective conservation and restoration efforts. In this study, we combined a species distribution model and geographical detector to propose a novel framework for mapping the distribution and disturbance of degraded coastal wetland vegetation in sparsely recorded areas and identifying conservation and restoration priorities. Guangxi is a province in China known for its extensive coastal wetland vegetation. In our study of Guangxi, habitats suitable for two degraded vegetation types, i.e., seagrass and seaweed, were mapped using the maximum entropy model; 669.44 km2 of seagrass habitat and 929.69 km2 of seaweed habitat were identified. The geographical detector model was used to analyze anthropogenic disturbance caused by four local disturbance factors: shoreline development, fisheries, waterways, and ports and anchorages. Shoreline development was identified as the disturbance factor with the strongest impact on potential habitats of both vegetation types. According to these findings, 48.40 %-64.23 % of the vegetation habitats suffered from high anthropogenic disturbance. Preexisting nature reserves had not effectively protected wetland vegetation from human disturbance. Based on the spatial pattern of vegetation habitat and comprehensive anthropogenic disturbance, conservation and restoration priorities for seagrasses and seaweeds covering an area of 302.26 km2 were further mapped. Our results thus help improve wetland vegetation conservation by providing basic information, and they provide a tool to support site planning for seagrass and seaweed conservation and restoration.
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Affiliation(s)
- Jinlan Lin
- College of Marine Sciences, Shanghai Ocean University, Shanghai 201306, China; Guangxi Academy of Oceanography, Nanning 530022, China
| | - Sixuan He
- Key Laboratory of Marine Ecological Conservation and Restoration, Third Institute of Oceanography, Ministry of Natural Resources, Xiamen 361005, China
| | - Xinming Liu
- Institute of Marine Drugs, Guangxi University of Chinese Medicine, Nanning 530200, China
| | | | - Meng Li
- Guangxi Academy of Oceanography, Nanning 530022, China
| | - Bin Chen
- College of Marine Sciences, Shanghai Ocean University, Shanghai 201306, China; Key Laboratory of Marine Ecological Conservation and Restoration, Third Institute of Oceanography, Ministry of Natural Resources, Xiamen 361005, China.
| | - Wenjia Hu
- Key Laboratory of Marine Ecological Conservation and Restoration, Third Institute of Oceanography, Ministry of Natural Resources, Xiamen 361005, China.
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Suwandhahannadi WK, Wickramasinghe D, Dahanayaka DDGL, Le De L. Blue carbon storage in a tropical coastal estuary: Insights for conservation priorities. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 906:167733. [PMID: 37820813 DOI: 10.1016/j.scitotenv.2023.167733] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Revised: 10/03/2023] [Accepted: 10/08/2023] [Indexed: 10/13/2023]
Abstract
Seagrass ecosystems have been determined as necessary sinks in the global carbon cycle and contribute towards climate change mitigations. In the recent past, there has been an increase of studies focused on blue carbon opportunities provided by seagrasses but large knowledge gaps and uncertainties remain, particularly in tropical seagrass meadows in the South Asian regions. Therefore, the current study aims to quantify the organic carbon stocks in the seagrass meadows on the tropical estuary in southern coast of Sri Lanka and highlights the need of conserving seagrasses specially in the context of effective management of lagoons to achieve Sustainable Development Goals. Landsat 9 (OLI/TIRS) images were used to develop seagrass distribution maps for 2022 and the data were verified with ground truthing. Vegetation and soil samples were taken from eight sampling locations representing the Rekawa Lagoon. Aboveground biomass (AGB) and belowground biomass (BGB) were determined by multiplying the biomass with the carbon conversion factor whereas the loss-on-ignition (LOI) technique was applied to calculate the soil organic carbon. Results revealed that the soil core carbon content of the study site were ranged between 2.56 ± 0.29 to 3.04 ± 0.44 Mg C/ha. The calculated total carbon content of the 0.0324 km2 study area in Rekawa Lagoon was 10.21 Mg C, giving 87.06 % contribution from sediment organic carbon pool. This study provides insights for the conservation of these critical ecosystems and highlights the need of policy and action agendas for better management.
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Affiliation(s)
- W K Suwandhahannadi
- Department of Zoology and Environment Sciences, Faculty of Science, University of Colombo, PO Box 1490, Colombo 03, Sri Lanka; National Aquatic Resources Research and Development Agency (NARA), Crow Island, Mattakkuliya, Sri Lanka.
| | - D Wickramasinghe
- Department of Zoology and Environment Sciences, Faculty of Science, University of Colombo, PO Box 1490, Colombo 03, Sri Lanka
| | - D D G L Dahanayaka
- Department of Zoology, Faculty of Natural Sciences, The Open University of Sri Lanka, Nawala, Nugegoda, Sri Lanka
| | - Loic Le De
- School of Public Health and Interdisciplinary Studies, Auckland University of Technology, Auckland, New Zealand
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3
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Zheng P, Chen G, Lan W, Li S, Li M, Chen S, An W, Chen J, Yu S, Chen B. Determining effect of seagrass-mediated CO 2 flux on the atmospheric cooling potential of a subtropical intertidal seagrass meadow. MARINE POLLUTION BULLETIN 2023; 188:114676. [PMID: 36764143 DOI: 10.1016/j.marpolbul.2023.114676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2022] [Revised: 01/23/2023] [Accepted: 01/25/2023] [Indexed: 06/18/2023]
Abstract
Atmospheric greenhouse gas (GHG) emissions from seagrass meadows that determine the ecosystem atmospheric cooling effect have rarely been quantified. This study measured the simultaneous fluxes direct to the atmosphere of three GHGs (CO2, CH4 and N2O) within a Halophila beccarii seagrass meadow and an adjacent unvegetated bare intertidal flat, and their relationships to seagrass abundance and relevant soil parameters. The results showed that seasonal variation in seagrass abundance was strongly linked with the CO2 exchange rate. The CH4 and N2O fluxes were similarly low at both sites and comparable between winter and summer. The global warming potential of CH4 and N2O reduced the ecosystem CO2 uptake by only 5 % at the seagrass site. The results indicated that the H. beccarii meadow had a stronger atmospheric cooling effect than the bare flat and that the seagrass-mediated CO2 flux in this oligotrophic seagrass meadow primarily determined the atmospheric cooling effect.
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Affiliation(s)
- Pengxiang Zheng
- Shanghai Ocean University, Shanghai, China; Third Institute of Oceanography, Ministry of Natural Resources, Xiamen, China
| | - Guangcheng Chen
- Shanghai Ocean University, Shanghai, China; Third Institute of Oceanography, Ministry of Natural Resources, Xiamen, China; Observation and Research Station of Coastal Wetland Ecosystem in Beibu Gulf, Ministry of Natural Resources, Beihai, China.
| | - Wenlu Lan
- Marine Environmental Monitoring Center of Guangxi, Beihai, China
| | - Shiman Li
- Observation and Research Station of Coastal Wetland Ecosystem in Beibu Gulf, Ministry of Natural Resources, Beihai, China
| | - Mingmin Li
- Marine Environmental Monitoring Center of Guangxi, Beihai, China
| | - Shunyang Chen
- Third Institute of Oceanography, Ministry of Natural Resources, Xiamen, China; Observation and Research Station of Coastal Wetland Ecosystem in Beibu Gulf, Ministry of Natural Resources, Beihai, China
| | - Wenshuo An
- Third Institute of Oceanography, Ministry of Natural Resources, Xiamen, China; Observation and Research Station of Coastal Wetland Ecosystem in Beibu Gulf, Ministry of Natural Resources, Beihai, China
| | - Jiahui Chen
- Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, College of the Environment and Ecology, Xiamen University, Xiamen, China
| | - Shuo Yu
- Observation and Research Station of Coastal Wetland Ecosystem in Beibu Gulf, Ministry of Natural Resources, Beihai, China
| | - Bin Chen
- Shanghai Ocean University, Shanghai, China; Third Institute of Oceanography, Ministry of Natural Resources, Xiamen, China; Observation and Research Station of Coastal Wetland Ecosystem in Beibu Gulf, Ministry of Natural Resources, Beihai, China.
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Björk M, Rosenqvist G, Gröndahl F, Bonaglia S. Methane emissions from macrophyte beach wrack on Baltic seashores. AMBIO 2023; 52:171-181. [PMID: 36029461 PMCID: PMC9666566 DOI: 10.1007/s13280-022-01774-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Revised: 06/27/2022] [Accepted: 07/18/2022] [Indexed: 06/15/2023]
Abstract
Beach wrack of marine macrophytes is a natural component of many beaches. To test if such wrack emits the potent greenhouse gas methane, field measurements were made at different seasons on beach wrack depositions of different ages, exposure, and distance from the water. Methane emissions varied greatly, from 0 to 176 mg CH4-C m-2 day-1, with a clear positive correlation between emission and temperature. Dry wrack had lower emissions than wet. Using temperature data from 2016 to 2020, seasonal changes in fluxes were calculated for a natural wrack accumulation area. Such calculated average emissions were close to zero during winter, but peaked in summer, with very high emissions when daily temperatures exceeded 20 °C. We conclude that waterlogged beach wrack significantly contributes to greenhouse gas emissions and that emissions might drastically increase with increasing global temperatures. When beach wrack is collected into heaps away from the water, the emissions are however close to zero.
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Affiliation(s)
- Mats Björk
- Department of Ecology, Environment and Plant Sciences, Stockholm University, 106 91 Stockholm, Sweden
| | - Gunilla Rosenqvist
- Blue Centre Gotland, Uppsala University-Campus Gotland, 621 67 Visby, Sweden
| | - Fredrik Gröndahl
- KTH, Royale Institute of Technology, KTH Teknikringen 10B, Stockholm, Sweden
- Department of Sustainable Development, Environmental Science and Engineering, 100 44 Stockholm, Sweden
| | - Stefano Bonaglia
- Department of Marine Sciences, University of Gothenburg, Box 461, 405 30 Gothenburg, Sweden
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Dahl M, Ismail R, Braun S, Masqué P, Lavery PS, Gullström M, Arias-Ortiz A, Asplund ME, Garbaras A, Lyimo LD, Mtolera MSP, Serrano O, Webster C, Björk M. Impacts of land-use change and urban development on carbon sequestration in tropical seagrass meadow sediments. MARINE ENVIRONMENTAL RESEARCH 2022; 176:105608. [PMID: 35358909 DOI: 10.1016/j.marenvres.2022.105608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 03/13/2022] [Accepted: 03/14/2022] [Indexed: 06/14/2023]
Abstract
Seagrass meadows store significant carbon stocks at a global scale, but land-use change and other anthropogenic activities can alter the natural process of organic carbon (Corg) accumulation. Here, we assessed the carbon accumulation history of two seagrass meadows in Zanzibar (Tanzania) that have experienced different degrees of disturbance. The meadow at Stone Town has been highly exposed to urban development during the 20th century, while the Mbweni meadow is located in an area with relatively low impacts but historical clearing of adjacent mangroves. The results showed that the two sites had similar sedimentary Corg accumulation rates (22-25 g m-2 yr-1) since the 1940s, while during the last two decades (∼1998 until 2018) they exhibited 24-30% higher accumulation of Corg, which was linked to shifts in Corg sources. The increase in the δ13C isotopic signature of sedimentary Corg (towards a higher seagrass contribution) at the Stone Town site since 1998 points to improved seagrass meadow conditions and Corg accumulation capacity of the meadow after the relocation of a major sewage outlet in the mid-1990s. In contrast, the decrease in the δ13C signatures of sedimentary Corg in the Mbweni meadow since the early 2010s was likely linked to increased Corg run-off of mangrove/terrestrial material following mangrove deforestation. This study exemplifies two different pathways by which land-based human activities can alter the carbon storage capacity of seagrass meadows (i.e. sewage waste management and mangrove deforestation) and showcases opportunities for management of vegetated coastal Corg sinks.
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Affiliation(s)
- Martin Dahl
- Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden; School of Natural Sciences, Technology and Environmental Studies, Södertörn University, Huddinge, Sweden.
| | - Rashid Ismail
- Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden; Institute of Marine Sciences (IMS), University of Dar es Salaam, Zanzibar, Tanzania
| | - Sara Braun
- Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden
| | - Pere Masqué
- School of Science and Centre for Marine Ecosystems Research, Edith Cowan University, Joondalup, Western Australia, Australia; International Atomic Energy, Principality of Monaco, Monaco
| | - Paul S Lavery
- School of Science and Centre for Marine Ecosystems Research, Edith Cowan University, Joondalup, Western Australia, Australia
| | - Martin Gullström
- School of Natural Sciences, Technology and Environmental Studies, Södertörn University, Huddinge, Sweden
| | - Ariane Arias-Ortiz
- Ecosystem Science Division, Department of Environmental Science, Policy and Management, University of California, Berkeley, CA, USA; Institute of Marine Sciences, University of California Santa Cruz, California, USA
| | - Maria E Asplund
- Department of Biological and Environmental Sciences, University of Gothenburg, Kristineberg, Fiskebäckskil, Sweden
| | | | - Liberatus D Lyimo
- Department of Crop Science and Horticulture. Sokoine University of Agriculture, Morogoro, Tanzania
| | - Matern S P Mtolera
- Institute of Marine Sciences (IMS), University of Dar es Salaam, Zanzibar, Tanzania
| | - Oscar Serrano
- School of Science and Centre for Marine Ecosystems Research, Edith Cowan University, Joondalup, Western Australia, Australia; Centro de Estudios Avanzados de Blanes, Consejo Superior de Investigaciones Científicas (CEAB-CSIC), Blanes, Spain
| | - Chanelle Webster
- School of Science and Centre for Marine Ecosystems Research, Edith Cowan University, Joondalup, Western Australia, Australia
| | - Mats Björk
- Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden
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Soonthornkalump S, Ow YX, Saewong C, Buapet P. Comparative study on anatomical traits and gas exchange responses due to belowground hypoxic stress and thermal stress in three tropical seagrasses. PeerJ 2022; 10:e12899. [PMID: 35186485 PMCID: PMC8840093 DOI: 10.7717/peerj.12899] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 01/17/2022] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND The ability to maintain sufficient oxygen levels in the belowground tissues and the rhizosphere is crucial for the growth and survival of seagrasses in habitats with highly reduced sediment. Such ability varies depending on plant anatomical features and environmental conditions. METHODS In the present study, we compared anatomical structures of roots, rhizomes and leaves of the tropical intertidal seagrasses, Cymodocea rotundata, Thalassia hemprichii and Halophila ovalis, followed by an investigation of their gas exchange both in the belowground and aboveground tissues and photosynthetic electron transport rates (ETR) in response to experimental manipulations of O2 level (normoxia and root hypoxia) and temperature (30 °C and 40 °C). RESULTS We found that C. rotundata and T. hemprichii displayed mostly comparable anatomical structures, whereas H. ovalis displayed various distinctive features, including leaf porosity, number and size of lacunae in roots and rhizomes and structure of radial O2 loss (ROL) barrier. H. ovalis also showed unique responses to root hypoxia and heat stress. Root hypoxia increased O2 release from belowground tissues and overall photosynthetic activity of H. ovalis but did not affect the other two seagrasses. More pronounced warming effects were detected in H. ovalis, measured as lower O2 release in the belowground tissues and overall photosynthetic capacity (O2 release and dissolved inorganic carbon uptake in the light and ETR). High temperature inhibited photosynthesis of C. rotundata and T. hemprichii but did not affect their O2 release in belowground tissues. Our data show that seagrasses inhabiting the same area respond differently to root hypoxia and temperature, possibly due to their differences in anatomical and physiological attributes. Halophila ovalis is highly dependent on photosynthesis and appears to be the most sensitive species with the highest tendency of O2 loss in hypoxic sediment. At the same time, its root oxidation capacity may be compromised under warming scenarios.
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Affiliation(s)
- Sutthinut Soonthornkalump
- Division of Biological Science, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla, Thailand,Coastal Oceanography and Climate Change Research Center, Prince of Songkla University, Hat Yai, Songkhla, Thailand
| | - Yan Xiang Ow
- St John’s Island National Marine Laboratory, Tropical Marine Science Institute, National University of Singapore, Singapore, Singapore
| | - Chanida Saewong
- Division of Biological Science, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla, Thailand,Coastal Oceanography and Climate Change Research Center, Prince of Songkla University, Hat Yai, Songkhla, Thailand
| | - Pimchanok Buapet
- Division of Biological Science, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla, Thailand,Coastal Oceanography and Climate Change Research Center, Prince of Songkla University, Hat Yai, Songkhla, Thailand
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Sun Y, Song Z, Zhang H, Liu P, Hu X. Seagrass vegetation affect the vertical organization of microbial communities in sediment. MARINE ENVIRONMENTAL RESEARCH 2020; 162:105174. [PMID: 33099080 DOI: 10.1016/j.marenvres.2020.105174] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 09/11/2020] [Accepted: 10/06/2020] [Indexed: 06/11/2023]
Abstract
Seagrasses represent high primary productivity and provide important ecosystem services to the marine environment. Seagrass-associated microbial communities are playing essential ecological functional roles in biogeochemical cycles. However, little is known about the effect of seagrass vegetation on microbial communities in sediment. In the present study, the sediment cores of seagrass bed (dominated by Zostera japonica and Zostera marine) and degradation area in Swan Lake (China) were sampled; then, biogeochemical parameters were analyzed, and microbial community composition was investigated by using high-throughput sequencing of the 16S rRNA gene. The results showed that the presence of seagrass could lead to a decrease in the richness and diversity of the microbial community. In the vertical direction, a pronounced shift from Proteobacteria-dominated upper layers to Chloroflexi and Crenarchaeota-dominated deep layers in all sediment cores were observed. Besides, Bathyarchaeia is more abundant at degradation area, while Vibrionaceae, Sulfurovum and Lokiarchaeial overrepresent at the seagrass bed area. Vibrionaceae was abundant in the rhizosphere of Z. marina and Z. japonica, and the proportions reached 84.45% and 63.89%, respectively. This enrichment of Vibrio spp. may be caused by the macrobenthic species near the seagrass rhizosphere, and these Vibrio spp. reduced the diversity and stability of microbial community, which may lead to the degradation of seagrass. This study would provide clues for the distribution patterns and niche preferences of seagrass microbiome. The conservation strategy of seagrass would be further elucidated from the perspective of the microbiome.
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Affiliation(s)
- Yanyu Sun
- Key Laboratory of Coastal Biology and Bioresource Utilization, Yantai Institute of Costal Zone Research, Chinese Academy of Sciences, Yantai, Shandong, 264003, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, Shandong, 266237, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Zenglei Song
- Key Laboratory of Coastal Biology and Bioresource Utilization, Yantai Institute of Costal Zone Research, Chinese Academy of Sciences, Yantai, Shandong, 264003, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, Shandong, 266237, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Haikun Zhang
- Key Laboratory of Coastal Biology and Bioresource Utilization, Yantai Institute of Costal Zone Research, Chinese Academy of Sciences, Yantai, Shandong, 264003, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, Shandong, 266237, China
| | - Pengyuan Liu
- Key Laboratory of Coastal Biology and Bioresource Utilization, Yantai Institute of Costal Zone Research, Chinese Academy of Sciences, Yantai, Shandong, 264003, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, Shandong, 266237, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xiaoke Hu
- Key Laboratory of Coastal Biology and Bioresource Utilization, Yantai Institute of Costal Zone Research, Chinese Academy of Sciences, Yantai, Shandong, 264003, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, Shandong, 266237, China.
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Al-Haj AN, Fulweiler RW. A synthesis of methane emissions from shallow vegetated coastal ecosystems. GLOBAL CHANGE BIOLOGY 2020; 26:2988-3005. [PMID: 32068924 DOI: 10.1111/gcb.15046] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Accepted: 01/09/2020] [Indexed: 06/10/2023]
Abstract
Vegetated coastal ecosystems (VCEs; i.e., mangroves, salt marshes, and seagrasses) play a critical role in global carbon (C) cycling, storing 10× more C than temperate forests. Methane (CH4 ), a potent greenhouse gas, can form in the sediments of these ecosystems. Currently, CH4 emissions are a missing component of VCE C budgets. This review summarizes 97 studies describing CH4 fluxes from mangrove, salt marsh, and seagrass ecosystems and discusses factors controlling CH4 flux in these systems. CH4 fluxes from these ecosystems were highly variable yet they all act as net methane sources (median, range; mangrove: 279.17, -67.33 to 72,867.83; salt marsh: 224.44, -92.60 to 94,129.68; seagrass: 64.80, 1.25-401.50 µmol CH4 m-2 day-1 ). Together CH4 emissions from mangrove, salt marsh, and seagrass ecosystems are about 0.33-0.39 Tmol CH4 -C/year-an addition that increases the current global marine CH4 budget by more than 60%. The majority (~45%) of this increase is driven by mangrove CH4 fluxes. While organic matter content and quality were commonly reported in individual studies as the most important environmental factors driving CH4 flux, they were not significant predictors of CH4 flux when data were combined across studies. Salinity was negatively correlated with CH4 emissions from salt marshes, but not seagrasses and mangroves. Thus the available data suggest that other environmental drivers are important for predicting CH4 emissions in vegetated coastal systems. Finally, we examine stressor effects on CH4 emissions from VCEs and we hypothesize that future changes in temperature and other anthropogenic activites (e.g., nitrogen loading) will likely increase CH4 emissions from these ecosystems. Overall, this review highlights the current and growing importance of VCEs in the global marine CH4 budget.
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Affiliation(s)
- Alia N Al-Haj
- Department of Earth and Environment, Boston University, Boston, MA, USA
| | - Robinson W Fulweiler
- Department of Earth and Environment, Boston University, Boston, MA, USA
- Department of Biology, Boston University, Boston, MA, USA
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George R, Gullström M, Mtolera MSP, Lyimo TJ, Björk M. Methane emission and sulfide levels increase in tropical seagrass sediments during temperature stress: A mesocosm experiment. Ecol Evol 2020; 10:1917-1928. [PMID: 32128125 PMCID: PMC7042687 DOI: 10.1002/ece3.6009] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 12/18/2019] [Accepted: 12/23/2019] [Indexed: 11/11/2022] Open
Abstract
Climate change-induced ocean warming is expected to greatly affect carbon dynamics and sequestration in vegetated shallow waters, especially in the upper subtidal where water temperatures may fluctuate considerably and can reach high levels at low tides. This might alter the greenhouse gas balance and significantly reduce the carbon sink potential of tropical seagrass meadows. In order to assess such consequences, we simulated temperature stress during low tide exposures by subjecting seagrass plants (Thalassia hemprichii) and associated sediments to elevated midday temperature spikes (31, 35, 37, 40, and 45°C) for seven consecutive days in an outdoor mesocosm setup. During the experiment, methane release from the sediment surface was estimated using gas chromatography. Sulfide concentration in the sediment pore water was determined spectrophotometrically, and the plant's photosynthetic capacity as electron transport rate (ETR), and maximum quantum yield (Fv/Fm) was assessed using pulse amplitude modulated (PAM) fluorometry. The highest temperature treatments (40 and 45°C) had a clear positive effect on methane emission and the level of sulfide in the sediment and, at the same time, clear negative effects on the photosynthetic performance of seagrass plants. The effects observed by temperature stress were immediate (within hours) and seen in all response variables, including ETR, Fv/Fm, methane emission, and sulfide levels. In addition, both the methane emission and the size of the sulfide pool were already negatively correlated with changes in the photosynthetic rate (ETR) during the first day, and with time, the correlations became stronger. These findings show that increased temperature will reduce primary productivity and increase methane and sulfide levels. Future increases in the frequency and severity of extreme temperature events could hence reduce the climate mitigation capacity of tropical seagrass meadows by reducing CO2 sequestration, increase damage from sulfide toxicity, and induce the release of larger amounts of methane.
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Affiliation(s)
- Rushingisha George
- Department of Ecology, Environment and Plant SciencesSeagrass Ecology and Physiology groupStockholm UniversityStockholmSweden
- Tanzania Fisheries Research Institute (TAFIRI)Dar es SalaamTanzania
| | - Martin Gullström
- Department of Ecology, Environment and Plant SciencesSeagrass Ecology and Physiology groupStockholm UniversityStockholmSweden
- Department of Biological and Environmental SciencesUniversity of GothenburgKristineberg, FiskebäckskilSweden
| | | | - Thomas J. Lyimo
- Department of Molecular Science and BiotechnologyUniversity of Dar es SalaamDar es SalaamTanzania
| | - Mats Björk
- Department of Ecology, Environment and Plant SciencesSeagrass Ecology and Physiology groupStockholm UniversityStockholmSweden
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10
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Nascimento FJA, Dahl M, Deyanova D, Lyimo LD, Bik HM, Schuelke T, Pereira TJ, Björk M, Creer S, Gullström M. Above-below surface interactions mediate effects of seagrass disturbance on meiobenthic diversity, nematode and polychaete trophic structure. Commun Biol 2019; 2:362. [PMID: 31602411 PMCID: PMC6778119 DOI: 10.1038/s42003-019-0610-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Accepted: 09/12/2019] [Indexed: 11/08/2022] Open
Abstract
Ecological interactions between aquatic plants and sediment communities can shape the structure and function of natural systems. Currently, we do not fully understand how seagrass habitat degradation impacts the biodiversity of belowground sediment communities. Here, we evaluated indirect effects of disturbance of seagrass meadows on meiobenthic community composition, with a five-month in situ experiment in a tropical seagrass meadow. Disturbance was created by reducing light availability (two levels of shading), and by mimicking grazing events (two levels) to assess impacts on meiobenthic diversity using high-throughput sequencing of 18S rRNA amplicons. Both shading and simulated grazing had an effect on meiobenthic community structure, mediated by seagrass-associated biotic drivers and sediment abiotic variables. Additionally, shading substantially altered the trophic structure of the nematode community. Our findings show that degradation of seagrass meadows can alter benthic community structure in coastal areas with potential impacts to ecosystem functions mediated by meiobenthos in marine sediments.
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Affiliation(s)
| | - Martin Dahl
- Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden
| | - Diana Deyanova
- Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden
| | - Liberatus D. Lyimo
- School of Biological Sciences, University of Dodoma, Box 338, Dodoma, Tanzania
| | - Holly M. Bik
- Department of Nematology, University of California—Riverside, 900 University Avenue, Riverside, CA 92521 USA
| | - Taruna Schuelke
- Department of Nematology, University of California—Riverside, 900 University Avenue, Riverside, CA 92521 USA
| | - Tiago José Pereira
- Department of Nematology, University of California—Riverside, 900 University Avenue, Riverside, CA 92521 USA
| | - Mats Björk
- Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden
| | - Simon Creer
- Molecular Ecology and Fisheries Genetics Laboratory, School of Biological Sciences, Bangor University, Bangor, LL57 2UW UK
| | - Martin Gullström
- Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden
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George R, Gullström M, Mangora MM, Mtolera MSP, Björk M. High midday temperature stress has stronger effects on biomass than on photosynthesis: A mesocosm experiment on four tropical seagrass species. Ecol Evol 2018; 8:4508-4517. [PMID: 29760891 PMCID: PMC5938440 DOI: 10.1002/ece3.3952] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Revised: 01/19/2018] [Accepted: 01/27/2018] [Indexed: 11/24/2022] Open
Abstract
The effect of repeated midday temperature stress on the photosynthetic performance and biomass production of seagrass was studied in a mesocosm setup with four common tropical species, including Thalassia hemprichii, Cymodocea serrulata, Enhalus acoroides, and Thalassodendron ciliatum. To mimic natural conditions during low tides, the plants were exposed to temperature spikes of different maximal temperatures, that is, ambient (29–33°C), 34, 36, 40, and 45°C, during three midday hours for seven consecutive days. At temperatures of up to 36°C, all species could maintain full photosynthetic rates (measured as the electron transport rate, ETR) throughout the experiment without displaying any obvious photosynthetic stress responses (measured as declining maximal quantum yield, Fv/Fm). All species except T. ciliatum could also withstand 40°C, and only at 45°C did all species display significantly lower photosynthetic rates and declining Fv/Fm. Biomass estimation, however, revealed a different pattern, where significant losses of both above‐ and belowground seagrass biomass occurred in all species at both 40 and 45°C (except for C. serrulata in the 40°C treatment). Biomass losses were clearly higher in the shoots than in the belowground root–rhizome complex. The findings indicate that, although tropical seagrasses presently can cope with high midday temperature stress, a few degrees increase in maximum daily temperature could cause significant losses in seagrass biomass and productivity.
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Affiliation(s)
- Rushingisha George
- Seagrass Ecology and Physiology Research Group Department of Ecology, Environment and Plant Sciences Stockholm University Stockholm Sweden.,Tanzania Fisheries Research Institute (TAFIRI) Dar es Salaam Tanzania
| | - Martin Gullström
- Seagrass Ecology and Physiology Research Group Department of Ecology, Environment and Plant Sciences Stockholm University Stockholm Sweden
| | | | | | - Mats Björk
- Seagrass Ecology and Physiology Research Group Department of Ecology, Environment and Plant Sciences Stockholm University Stockholm Sweden
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