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Impacts of wetland dieback on carbon dynamics: A comparison between intact and degraded mangroves
Abstract and Figures
Mangroves are effective blue carbon sinks and are the most carbon rich ecosystems on earth. However, their areal extent has declined by over one-third in recent decades. Degraded mangrove forests result in reduced carbon captured and lead to release of stored carbon into the atmosphere by CO2 emission. The aim of this study was to assess changes in carbon dynamics in a gradually degrading mangrove forest on Bonaire, Dutch Caribbean. Remote sensing techniques were applied to estimate the distribution of intact and degraded mangroves. Forest structure, sediment carbon storage, sediment CO2 effluxes and dissolved organic and inorganic carbon in pore and surface waters across intact and degraded parts were assessed. On average intact mangroves showed 31% sediment organic carbon in the upper 30 cm compared to 20% in degraded mangrove areas. A loss of 1.51 MgCO2 ha⁻¹ yr⁻¹ for degraded sites was calculated. Water samples showed a hypersaline environment in the degraded mangrove area averaging 93 which may have caused mangrove dieback. Sediment CO2 efflux within degraded sites was lower than values from other studies where degradation was caused by clearing or cutting, giving new insights into carbon dynamics in slowly degrading mangrove systems. Results of water samples agreed with previous studies where inorganic carbon outwelled from mangroves might enhance ecosystem connectivity by potentially buffering ocean acidification locally. Wetlands will be impacted by a variety of stressors resulting from a changing climate. Results from this study could inform scientists and stakeholders on how combined stresses, such as climate change with salinity intrusion may impact mangrove's blue carbon sink potential and highlight the need of future comparative studies of intact versus degraded mangrove stands.
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... For example, one of the largest mangrove diebacks globally was caused by hypersalinity, which resulted from impaired hydrological connection after construction of causeways in combination with warmer temperatures (Jaramillo et al., 2018). As impacts of combined stressors are likely to intensify with climate change, more research is needed on comparing intact and degraded mangrove (Senger et al., 2021). ...
... Hypersalinity, defined as salinity > 40 (Whitfield et al., 2012;Tweedley et al., 2019), has caused mangrove dieback around the world (Barreto, 2004;Lovelock et al., 2017a;Jaramillo et al., 2018;Senger et al., 2021). Mangroves are adapted to live in saline habitats with regular tidal inundation (Krauss et al., 2008;Lovelock et al., 2016). ...
... While A. marina is adapted to high salinities, widespread canopy loss (leaves and branches) occurred with porewater salinities of 68.5 (Lovelock et al., 2017a). Mortality of other mangrove was observed at salinities of >74 (Cardona and Botero, 1998), >80 (Barreto, 2004), or >93 (Senger et al., 2021). ...
Mangrove forests provide essential ecosystem services, but are threatened by habitat loss, effects of climatic change and chemical pollutants. Hypersalinity can also lead to mangrove mortality, although mangroves are adapted to saline habitats. A recent dieback event of >9 ha of temperate mangrove (Avicennia marina) in South Australia allowed to evaluate the generality of anthropogenic impacts on mangrove ecosystems. We carried out multidisciplinary investigations, combining airborne remote sensing with on-ground measurements to detect the extent of the impact. The mangrove forest was differentiated into “healthy,” “stressed,” and “dead” zones using airborne LIDAR, RGB and hyperspectral imagery. Differences in characteristics of trees and soils were tested between these zones. Porewater salinities of >100 were measured in areas where mangrove dieback occurred, and hypersalinity persisted in soils a year after the event, making it one of the most extreme hypersalinity cases known in mangrove. Sediments in the dieback zone were anaerobic and contained higher concentrations of sulfate and chloride. CO2 efflux from sediment as well as carbon stocks in mangrove biomass and soil did not differ between the zones a year after the event. Mangrove photosynthetic traits and physiological characteristics indicated that mangrove health was impacted beyond the immediate dieback zone. Normalized Difference Vegetation Index (NDVI), photosynthetic rate, stomatal conductance and transpiration rate as well as chlorophyll fluorescence were lower in the “stressed” than “healthy” mangrove zone. Leaves from mangrove in the “stressed” zone contained less nitrogen and phosphorous than leaves from the “healthy” zone, but had higher arsenic, sulfur and zinc concentrations. The response to extreme hypersalinity in the temperate semi-arid mangrove was similar to response from the sub-/tropical semi-arid mangrove. Mangrove in semi-arid climates are already at their physiological tolerance limit, which places them more at risk from extreme hypersalinity regardless of latitude. The findings have relevance for understanding the generality of disturbance effects on mangrove, with added significance as semi-arid climate regions could expand with global warming.
... Mangroves are effective carbon sinks, storing large amounts of carbon in their biomass and soil. However, when degraded or destroyed, this stored carbon is released back into the atmosphere [9,10]. In addition, mangrove degradation also leads to the decomposition of accumulated organic matter in the soil, releasing more CO 2 and CH 4 into the atmosphere. ...
... According to Lovelock et al. [83] the disturbance and exposure of sediment in degraded mangroves accelerates the erosion of the upper layer, leaving it exposed to physical forces that lead to chemical weathering and higher decomposition rates, which leads to lower carbon storage. Senger et al. [10] found that carbon is rich in the upper 30cm of the sediment in intact sites and is poor in degraded sites. Likewise, intact plots have more SOC associated with higher CO 2 fluxes, while degraded plots have a higher SOC low and poorer CO 2 fluxes, which is like our results. ...
... These numbers correspond to the average of the five Sentinel-2 images analysed in this study. A recent study that used two Sentinel-2 images taken on 30 October 2018 and 8 January 2019 reported that the extent of the mangrove area in Lac Bay covered 247 ha, of which 199 ha was identified as intact mangroves and 48 ha as degraded mangroves (Senger et al., 2021). If we compare these data with the estimations obtained in this study in 2022, for example for the image registered on 23 March 2022, we obtain a loss of 10 % in the extent of the mangrove area in just over 3 years (i.e., between 8 January 2019 and 23 March 2022). ...
... If we compare these data with the estimations obtained in this study in 2022, for example for the image registered on 23 March 2022, we obtain a loss of 10 % in the extent of the mangrove area in just over 3 years (i.e., between 8 January 2019 and 23 March 2022). Although this potential decline in mangrove cover is in line with the general trend of mangrove loss reported for the Caribbean region over the last two decades (Bunting et al., 2022), comparison of our results with those reported by Senger et al. (2021) should be taken with care, as different classification methods were used (i.e., Random Forest compared to ML in this study). ...
... Kandelia obovata is the dominant mangrove species along the southeast coast of China and is tolerant to a variety of complex environments such as high organic matter, low oxygen, and tidal flooding in the sea-land ecotone (Senger et al., 2021;Jiang et al., 2022). In addition, it is an integral part of blue carbon ecosystems, which can absorb large quantities of carbon dioxide from the atmosphere and alleviate the negative impact of global climate change. ...
... As one of the most carbon-rich ecosystems worldwide (Senger et al., 2021), mangroves are mostly found in tropical and subtropical coastal regions. Carbon sequestration by mangroves also plays a vital role in mitigating global warming and reducing greenhouse gas emissions (Gu et al., 2022). ...
As an important mangrove species, Kandelia obovata plays an irreplaceable role in the coastal ecosystem. However, due to a lack of genetic technology, there is limited research on its functional genes. As such, establishing an efficient and rapid functional verification system is particularly important. In this study,tobacco rattle virus (TRV) and the phytoene desaturase gene KoPDS were used as the vector and target gene, respectively, to establish a virus-induced gene silencing system (VIGS) in K. obovata. Besides, the system was also used to verify the role of a Chlorophyll a/b binding protein (Cab) gene KoCAB in leaf carbon sequestration of K. obovata.
RNA-Seq and qRT-PCR showed that the highest gene-silencing efficiency could reach 90% after 10 days of inoculation and maintain above 80% after 15 days, which was achieved with resuspension buffer at pH 5.8 and Agrobacterium culture at OD600 of 0.4-0.6. Taken together, the TRV-mediated VIGS system established herein is the first genetic analysis tool for mangroves, which may greatly impel functional genomics studies in mangrove plants.
... Nevertheless, mangrove coasts have become increasingly exposed to changing environmental conditions, a trend that has resulted in a declining mangrove cover on a global scale. At the protected Ramsar site of Lac Bay, Bonaire ( Figure 1), large areas of mangroves have been subject to deterioration and tree mortality (Senger et al., 2021). Excessive sediment inputs from the land and mangrove growth have clogged existing creeks and reduced hydrodynamic circulation through the mangrove system. ...
... Lac Bay has an extent of about 700 ha, comprising coral reefs and a lagoon surrounded by mangroves. The forest fringe consists of Rizophora mangle, while the more saline and muddier inland forest is dominated by Avicennia germinans and Laguncularia racemosa (Senger et al., 2021). During a 6-week field campaign we monitored concurrent water levels and flow speeds throughout the area (Figure 1) and surveyed both the bathymetry and mangrove vegetation. ...
Mangroves provide natural buffers between land and sea, protecting both coastal communities and nature as they attenuate waves and stabilize shorelines but also filter terrestrial runoff. Tropical mangroves are also biodiversity hotspots and provide other ecosystem services such as supporting fish and shellfish habitat, accommodating ecotourism and sequestering carbon. Nevertheless, mangrove coasts have become increasingly exposed to changing environmental conditions, a trend that has resulted in a declining mangrove cover on a global scale. At the protected Ramsar site of Lac Bay, Bonaire, large areas of mangroves have been subject to deterioration and tree mortality (Senger et al., 2021). Excessive sediment inputs from the land and mangrove growth have clogged existing creeks and reduced hydrodynamic circulation through the mangrove system. Resulting changes in sedimentation rates, submergence and water quality affect the survival of the inland mangroves in Lac Bay. The (re-)creation of suitable morphological and hydrodynamic conditions is key for mangrove restoration (Friess et al., 2019). This study investigates the potential of creek restoration to increase the hydrodynamic circulation in the mangroves of Lac Bay, thereby accommodating their survival.
... In this respect, the carbon stock of mangroves ecosystems is site-specific. It depends on the method used, latitudes, and site characteristics that influence mangroves' community composition and productivity (Pérez et al., 2018;Atwood et al., 2017;Senger et al., 2021). For instance, the results obtained from Al-Qurm Nature Reserve in Oman (Al-Nadabi and Sulaiman, 2018), coastal Red sea of Saudi Arabia , and Khor Kalba in UAE (Crooks et al., 2019) of carbon sequestration by mangroves explain the enormous differences obtained and the shortcoming of absolute use of these values. ...
... Thus, a comparison of the findings is not possible. However, the total carbon stock of mangrove in Tubli Bay (i.e., 106.5 Mg C ha −1 ) is within the range reported in other regions (e.g., 45 Mg C ha −1 in north-west Australia (Hickey et al., 2018), 60-140 Mg C ha −1 in Bonaire, Dutch Caribbean (Senger et al., 2021). ...
... In this respect, the carbon stock of mangroves ecosystems is site-specific. It depends on the method used, latitudes, and site characteristics that influence mangroves' community composition and productivity (Pérez et al., 2018;Atwood et al., 2017;Senger et al., 2021). For instance, the results obtained from Al-Qurm Nature Reserve in Oman (Al-Nadabi and Sulaiman, 2018), coastal Red sea of Saudi Arabia , and Khor Kalba in UAE (Crooks et al., 2019) of carbon sequestration by mangroves explain the enormous differences obtained and the shortcoming of absolute use of these values. ...
... Thus, a comparison of the findings is not possible. However, the total carbon stock of mangrove in Tubli Bay (i.e., 106.5 Mg C ha −1 ) is within the range reported in other regions (e.g., 45 Mg C ha −1 in north-west Australia (Hickey et al., 2018), 60-140 Mg C ha −1 in Bonaire, Dutch Caribbean (Senger et al., 2021). ...
The grey mangrove Avicenna marina, constructs one of the most critical coastal ecosystems in the Kingdom of Bahrain which has been severely deteriorated by increasing anthropogenic pressures. This study aimed to assess the spatiotemporal changes in the mangrove habitat around Tubli Bay, Kingdom of Bahrain, over the last 50 years through achieving the following: (1) detect the progressive reduction in the mangrove cover using Geographic Information Science and Systems (GISs) techniques and remote sensing data, (2) estimate the changes of above-below ground (AGB-BGB) carbon sequestered in the mangroves using a GIS-based spatial analysis approach, and (3) estimate the potential carbon emission change from the loss of original mangrove habitats. Various GIS and remotely sensed data were employed in the study, including high-resolution satellite images from Worldview-3. Worldview-2, IKONOS, and QuickBird, coupled with true-color orthorectified aerial photographs. Additional data was acquired from fieldwork and the ancillary GIS maps. Image processing of the satellite data was conducted using ENVI 5.5 software. ArcGIS 10.8 was used for digitizing the mangrove areas in all satellite imagery. The final maps were used to assess and calculate mangrove area changes. The spatiotemporal process was used to calculate carbon values and estimate the amount of carbon loss due to land reclamation activities. Our results indicated that Bahrain lost more than 95% of the natural mangrove cover during the period from 1967 to 2020. The net loss in the mangrove extent area reached 280 ha during 1967–2020, as it declined from 328 ha in 1967 to 48 ha in 2020. The primary cause of the decline was land reclamation associated with urban development. The rates and causes of the loss varied both spatially as well as temporally. Due to land clearing, the total carbon stored in the mangrove habitat declined from 34932.2 Mg C ha ⁻¹ in 1967 to 5112 Mg C ha ⁻¹ in 2020. Consequently, the potential carbon Sequestration decreased from 128,200.44 Mg CO2 eq. ha-1 in 1967 to 18,761.04 Mg CO2 eq. ha ⁻¹ in 2020. Our study urges for more efficient conservation of the remaining mangroves in Bahrain to sustain their valuable ecosystem services particularly the Sequestration of carbon.
... At local scales, the alteration of natural ecosystems degrades local climate regulation and reduces the protection from natural risks they provide (Bradshaw et al., 2007;The World Bank, 2009;Hoffmann and Sgrò, 2011;Pielke Sr. et al., 2011;Ferrario et al., 2014;Beugnon et al., 2021;Senger et al., 2021). As above, biodiversity enhances the capacity of ecosystems to sustain extreme climatic events, and biodiversity loss impairs the resilience of ecosystems and reduces their ability to regulate the climate (Loreau and de Mazancourt, 2013;Carrick and Forsythe, 2020 (Ismail et al., 2021;Guisan et al., 2022b). ...
... The degradation of mangroves must be taken seriously, as the destruction of mangroves not only leads to a decrease in the OC deposition rate but also accelerates the decomposition of stored carbon in sediments, releasing greenhouse gases into the atmosphere. Ultimately, this could transform mangroves from a carbon sink into a carbon source (Senger et al., 2021). The effects of human activities on the mangroves in the study area are expected to gradually decrease in the future. ...
Mangrove forests serve as significant carbon sinks and play a crucial role in mitigating climate change. Currently, the response of mangroves to intensified climate change and human activities, and the factors that influence the magnitude of carbon storage in their sediments remain uncertain. To address these questions, two sediment cores were collected from the mangrove reserve in Pearl Bay, Guangxi, China. The activity of ²¹⁰Pb in the sediment, grain size, bulk elemental composition, stable carbon isotopes, lignin, and different sediment organic matter (OM) fractions were investigated to determine the local mangrove’s response to climate change and human activities, as well as the factors influencing its carbon storage. The results showed mangrove forests with lower tidal ranges, slower sedimentation rates, and where OM predominantly originated locally tend to have larger carbon stocks. The mangrove OM (MOM) decreased progressively from the bottom to the top of the cores, indicating that the mangroves in Pearl Bay have possibly undergone degradation, which was further substantiated by the decrease in lignin content. Based on these results, the entire cores were divided into two stages: stable stage 1 (1963–2001) and degradation stage 2 (2001–2020). The cause of the mangrove degradation is likely due to the impact of human activities; however, these impacts are anticipated to gradually lessen in the future due to mangrove protection policies. Our results indicate that lignin can track and predict mangrove growth trends and provide guidance for the sustainable management of mangrove ecosystems.
... Concurrently, climate change can markedly alter the carbon storage capacity of coastal wetlands. Under extreme weather conditions, mangroves may perish, with degraded mangroves resulting in a substantial reduction of blue carbon and markedly decreased carbon storage capacity (Senger et al., 2021;Chatting et al., 2022;Han et al., 2022). Recent in-depth research has underscored the significant role of blue carbon in regulating climate change and its substantial impact on global climate dynamics (Wang et al., 2021). ...
Blue carbon refers to the carbon fixed in marine ecosystems such as mangroves, salt marshes, and seagrass beds. Considered a treasure house for capturing and storing carbon dioxide, it can alleviate environmental issues linked to climate change and positively influence the environments where people live. Thus, to clarify the hotspots and development trends of blue carbon research, bibliometric analysis incorporating ScientoPy and VOSviewer software were used to quantitatively analyze 4,604 blue carbon publications from Web of Science and Scopus databases between 1993 and 2023. The results indicate a rapidly growing number of published studies on blue carbon, with blue carbon research being multifaceted and gradually becoming an interdisciplinary and international topic. This study on blue carbon, which is based on keyword clustering analysis, comprises three stages. The analysis of the strength of the cooperative connections between scholars in various countries who have published work on blue carbon. found that the cooperation networks of developed countries are strong and those of developing countries are relatively weak. Quantitative trend analysis reveals a growing focus on the restoration and conservation of blue carbon ecosystems, with remote sensing being the predominant technology used in the blue carbon research field in recent years. In blue carbon research, increasing carbon sequestration capacity, climate change mitigation, and carbon sequestration in macroalgae remain potential hotspots for research and development.
... Numerous wetland restoration initiatives have been put in place to improve C storage and vegetation structure to reduce wetland deterioration (Dung et al., 2016). Innovative pecuniary incentives are being developed, particularly in emerging economies, to promote local and national level forest conservation (Senger et al., 2021). Sustainable strategies like Reducing Emissions from Deforestation and Deg-radation (REDD+) are currently introduced to calculate net carbon reductions. ...
... Ningthoujam et al. (2018) presented a regression-based woody biomass estimation for tropical deciduous mixed forest dominated by Shorea robusta using ALOS PALSAR images and field data at the lower Himalayan belt of Northern India. Many studies show vegetation indices, texture factors, and topographical variables are important variables used in remote sensing to estimate forest biomass (Hojo et al., 2020;Nandy et al., 2017;Senger et al., 2020). Environmental variables (e.g., rainfall, humidity and soil) can affect the horizontal distribution of species biomass . ...
As an important forest type, deciduous broad-leaved forest is crucial for estimating forest carbon sequestration capacity and evaluating forest carbon balance. This study focuses on the natural deciduous broad-leaved forest of Mazongling Nature Reserve in Jinzhai County of China. WorldView-2 images were selected as data source. 36 candidate factors including vegetation indices, texture features, and topographic factors were used for modelling. Three machine learning algorithms (i.e., random forest, k-nearest neighbor, and artificial neural network) were used to establish the optimal quantitative retrieval model for natural deciduous broad-leaved biomass. Results showed that the ANN model was the best predictor with R ² = 0.69 and RMSE = 31.53 (Mg·ha ⁻¹ ). Combining the ANN model with the complete spatial coverage of remote sensing data, we developed a distribution map of natural deciduous broad-leaved biomass in the Mazongling forest farm. The estimated average biomass of the study area was 90.34 ± 47.96 Mg·ha ⁻¹ . In addition, the influence of light saturation on model accuracy is also discussed. This study confirms that remote sensing data in temporal and spatial space can improve the model estimation accuracy.
... formation of blue carbon was a complex process that mainly involves several disciplines such as biological oceanography, enzymology, metabolic organization, and atmospheric science (Billah et al., 2022;Senger et al., 2021). Blue carbon sequestration and storage mechanisms mainly included microbial carbon pumps, biological carbon pumps, physical dissolved carbon pumps, and ocean carbonate pumps (Abbasi & Erdebilli, 2023;Battin et al., 2023). ...
Global climate change has become the primary environmental issue in the international community. Blue carbon is an effective way to build a community of destiny for the oceans and achieve carbon neutrality. And it has become a frontier area of global climate governance, which has received extensive attention from the academic circle. Based on analyzing the origin and conceptual connotation of blue carbon research, the article organized 4530 related papers from 1990 to 2023 based on the Web of Science Core Collection database. Adopting the bibliometric method with CiteSpace 6.1.R3, the paper analyzed the main characteristics of the blue carbon research literature in terms of temporal distribution, spatial distribution, journals, institutions, and authors. Then, through mapping the keywords under the high-citation articles, the alluvial map of research hotspots, the keywords co-occurrence, the keywords emergence, and the keywords clustering, the article explored the research hotspots and thematic evolution trends of blue carbon. There were four results: Firstly, there is an overall increasing trend in the number of blue carbon research publications over time. Secondly, the spatial distribution of blue carbon shows a multipolar development trend. Thirdly, blue carbon research has mainly experienced four periods. Fourthly, the research hotspots have evolved from a single ecosystem type to multiple ecosystem types and from conceptual understanding research to systems theory research. Based on the results, the study makes some policy recommendations. It is necessary to strengthen the basic research and innovation on blue carbon, to accelerate the research and development of cutting-edge technologies for blue carbon sequestration and sink enhancement, to improve the theoretical and practical research on the protection and restoration of blue carbon ecosystems, and to carry out international exchanges and cooperation on blue carbon in various fields. The purpose of this paper is to summarize the research status of blue carbon, promote a more scientific and rational development of the research field, and provide a reference for follow-up scholars to carry out related research.
... Mangrove typically grow at the interface of freshwater and seawater, and tides have a significant impact on the distribution of MPs in mangrove ecosystems [44]. Previous studies have demonstrated that hydrodynamic factors (tidal velocity and tidal range) affect the distribution of MPs in sediments in mangrove zones [26]. ...
Mangrove leaves have been acknowledged as crucial sink for coastal microplastics (MPs). Whereas, the temporal dynamics of MPs intercepted by mangrove leaves have remained poorly understood. Here, we detected MPs intercepted by submerged and non-submerged mangrove leaves over time and the potential driving factors. Abundance and characteristics of MPs interception by mangrove leaves exhibited dynamic fluctuations, with the coefficient of variation (CV) of submerged mangrove leaves (CV = 0.604; 1.76 n/g to 15.45 n/g) being approximately twofold higher than non-submerged mangrove leaves (CV = 0.377; 0.74 n/g to 3.28 n/g). Partial least squares path model (PLS-PM) analysis further illustrated that MPs abundance on submerged mangrove leaves were negative correlated to hydrodynamic factors (i.e., current velocity and tidal range). Intriguingly, secreted salt as a significantly driver of MPs intercepted by mangrove leaves. Results of this work highlights that MPs intercepted by mangrove leaves is characterized by dynamic fluctuations and reveals the importance of hydrodynamic factors and secreted salt. Overall, this work identifies the pivotal buffering role played by mangrove leaves in intercepting MPs, which provides basic knowledge for better understanding of microplastic pollution status and control from mangrove plants.
... Carbon sequestration also increased with advanced mangrove age (Sahu and Kathiresan 2019). Degraded forests typically showed lower carbon stock compared to the natural type (Senger et al. 2021). ...
Fatonah S, Hamidy R, Mulyadi A, Efriyeldi. 2023. Biomass, carbon stock and sequestration in various conditions of mangrove forests in Sungai Apit, Siak, Riau, Indonesia. Biodiversitas 24: 5837-5846. The value of aboveground carbon is influenced by differences in conditions of the mangrove. Therefore, this study aimed to estimate biomass, as well as carbon stock and sequestration in various mangrove forests within Sungai Apit Siak, including natural, rehabilitated, and degraded forests. The Line Transect Plot method was used for sampling. Aboveground biomass was determined using an allometric equation based on mangrove stem diameter. Stem diameter measurements were taken from mangrove vegetation in three forest conditions across three villages in Sungai Apit, Siak. The findings revealed that natural forests contained higher values of biomass, carbon stock, and sequestration at 256, 128, and 470 tons/ha, respectively, compared to rehabilitated and degraded forests. The variability in these parameters across different mangrove forests was influenced by stands characteristics, specifically basal area and mean tree diameter, which were associated with the age of mangrove vegetation and recovery duration. Notably, Rhizophora mucronata, Sonneratia caseolaris, and Avicennia alba exhibited the highest carbon sequestration. These results highlighted that Sungai Apit mangrove forests store a relatively high carbon stock, emphasizing the importance of implementing proper conservation and management measures to ensure sustainability.
... For this reason, roots are highly important in carbon capture and storage in these arid regions due to their high rates of below-ground carbon rotation and fixation. In fact, higher below-ground carbon values relative to biomass have been reported in several studies of mangroves [54,55]. As forests age, forest biomass and C stocks increase. ...
Estimation of carbon (C) stocks revealed a very high carbon sequestration potential of mangroves, which play a major role in the global C cycle. The C stored in the biomass of live trees can be estimated from above-and below-ground measurements, i.e., tree diameter and height, leaf litter, root biomass, necromass, and soil. The allocation of biomass and C in the scrub mangrove forest is influenced by various factors, including low structural development. The objective of this study was to estimate the carbon stock (in relation to biomass) and storage in the soil of the San Ignacio and El Dátil lagoons in an arid region of the north Pacific. Above-ground biomass (AGB) was estimated based on mangrove structure and leaf litter; below-ground biomass (BGB) was measured by extracting root cores (45 cm depth) and soil (1.2 m depth). Biomass values were converted to carbon with allometric equations. We found an inverse relationship between BGB content (roots) and above-ground structural development, with a mean total biomass (AGB + BGB) of 101.7 MgC ha −1. Below-ground carbon content (roots, necromass, and soil) was 2.8 times higher than above-ground carbon content (trees and litter). Control sites (devoid of vegetation) adjacent to the mangrove have recorded low carbon stocks of 7.3 MgC ha −1 , which supports the recommendations for conserving and restoring degraded areas. The present study contributes valuable information on carbon related to mangrove biomass and stored in the soil of arid mangrove areas of northwestern Mexico.
... Marchio et al. 2016). Significant decreases in SOC have been documented in degraded mangrove areas as compared to undisturbed mangrove areas(Senger et al. 2021). The degradation of mangroves leads to an increase in deterioration, decomposition by chemicals, and breakdown rates of the top layer of sediment, which ultimately results in reduced carbon capture and storage capacity at heavily impacted sites(Lovelock et al. 2017b). ...
Mangroves represent highly important coastal ecological systems on a global scale. Despite being highly examined ecosystems, the literature reveals several knowledge gaps regarding the impact of soil-water relationships in mangrove forests. This comprehensive literature review integrates extant studies on the impact of soil-water relationships within mangrove ecosystems at global and local levels, with the aim of identifying the factors that facilitate or impede their capacity to flourish productivity. Our findings demonstrate that various biogeochemical processes that take place in soil and water have an impact on the functioning and balance of mangrove ecosystems. These processes prompt mangroves to develop ecophysiological adaptations that enable them to mitigate the effects of harsh environmental stressors and changes, predominantly caused by anthropogenic activities. Alterations in both the physical and chemical properties of soil and water within mangrove ecosystems can have a direct impact on their distribution, density, and diversity. The review underscores the necessity of establishing appropriate policies and governance mechanisms for the protection and conservation of mangroves. The interplay between soil and water has a significant bearing on the functioning of mangrove ecosystems, with potential implications for productivity and functionality as anthropogenic and natural phenomena constantly alter their physicochemical properties.
... Former research has provided a report on how water stress could exasperate the deleterious effect of salt via disrupting nutrient uptake and photosynthesis, leading to the inhibition of plant growth (Alvarez and Sánchez-Blanco 2015;Alam et al. 2021). Both drought and salinity enhance stress conditions on crops, thereby hindering their capacity to absorb water and decrease the water potential of the plant tissues as well (Li et al. 2019b;Senger et al. 2021;Méndez-Alonzo et al. 2016;Al-Yasi et al. 2020). Salinity can force ionic stress on plants via the accumulation of Na + and Cl − influx with attendant implications on plant physiology and biochemistry which could culminate in the expression of toxicity symptoms including chlorosis (Wiszniewska et al. 2021;Tweedley et al. 2019;Panda et al. 2019). ...
Under natural conditions, most plants are exposed to a plethora of stress factors like salinity and drought which can act in synergy to undermine their growth responses. The red mangrove, Rhizophora mangle, is endemic to estuarine ecosystems and is prone to salinity and drought stresses under changing climatic conditions. This work aimed at elucidating the combined impact of drought and salinity on the growth pattern and physiology of red mangroves. The use of factorial experimental layout in a completely randomised design was employed in the study to impose either a single or a combination of different drought regimes and levels of salt stress on red mangrove plants, which culminated in nine treatments to uncover both the combined and individualistic impact of salinity and drought stresses on the red mangrove. Morphological, physiological and biochemical responses of the facultative halophyte were evaluated following the imposition of salinity and drought stress. The results revealed that application of both salinity and drought stresses simultaneously on red mangrove seedlings led to a decline in plant growth indices, chlorophyll content, transpiration rate [E], stomatal conductance [gs] and net photosynthesis rate [PN], as compared to other plants exposed to single stress treatment. Besides, combined salinity and drought treatment increased oxidative stress rapidly, thereby increasing malondialdehyde (MDA) and hydrogen peroxide (H2O2) accumulation. However, the red mangrove exhibited a certain level of stress resistance to the simulated salinity and drought stresses which was attributable to the mechanisms such as hyperactivation of catalase (CAT) and superoxide dismutase (SOD) activities and accumulation of osmoprotectants (soluble sugar, Na+ and Cl−). The results recorded indicate that gas exchange attributes, photosynthetic content, CAT and APX activities and MDA are reliable screening parameters for salinity and drought stress in the plants because they have roles in the level of combined stress tolerance exhibited by the red mangrove.
... Increasing sea temperatures, increasing frequency and intensity of heat waves, and extreme weather events lead to positive, negative or complex changes in blue carbon dynamics. A long-term record of sediment C ORG stocks in a restored Zostera marina meadow [50] , depending on the position in the meadow, showed that a single heat wave led to significant losses of sediment C ORG , with patterns of C ORG losses and re-accumulation lagging seagrass recovery times within the central meadow. However, in the outer meadow, there was a net increase of 60% of sediment C ORG throughout the following 3-year. ...
Blue carbon ecosystems require conservation and restoration to maximize organic carbon (C ORG) sequestration to ameliorate greenhouse gas emissions. Salt marshes, mangrove forests and seagrass meadows are all autotrophic and are considered blue carbon ecosystems. Macroalgae and tidal flats are currently not considered blue carbon habitats. Blue carbon ecosystems contribute globally to climate change mitigation and at local and national scales, especially in the provision of other ecosystem goods and services. Financial investment is constrained by large uncertainties in C ORG dynamics and best practices in restoration, rehabilitation and conservation. Several key emerging perspectives include (1) the fact that groundwater discharge of dissolved carbon is a major pathway of blue carbon loss; (2) allochthonous C ORG inputs are required to achieve ecosystem carbon mass balance; (3) blue carbon dynamics are enhanced by habitat connectivity and biotic activities; (4) CH 4 and N 2 O emissions reduce blue carbon potential; (5) habitat destruction causes blue carbon stock losses, but variable gas emissions; (6) sediment blue carbon stocks are increasing at the poles; and (7) land-use and land-cover changes (LULCC) drive changes in blue carbon stocks and emissions. Further research is needed to clarify the applicability of these emerging perspectives.
... During the period 1985 to 2005, there are about 0,66% of mangroves in the world has lost every year [5]. It also has been observed in the last decades of 20 th century that mangrove forests are degraded over one-third of the world [6]. Another research found that from 1988 to 2017, about 25% of non-water areas changed to the water area, and 5% of water areas changed to shoreline margin [7]. ...
North Java, Indonesia's Shoreline degradation has become a severe problem along its coast. The gradually vanishing of the mangrove greenbelt indicates starting of coastal erosion. To overcome that problem, the adaptive concept using Building with Nature (BwN) is expected to become a part of the solution by enhancing the natural process. Construction of permeable structures was started in 2013. Its implementation was modeled using Delft3D. A coupling between Delft3DFlow and Delft3DWave is proposed. The model is conducted in two scenarios, coastal areas without and with permeable structures. Both were simulated in wet and dry seasons. It is analyzed on three years morphological scale. 10 observation points were determined in the front and back of structures. Those are utilized as control points to check the height of sediment trapped. Accumulation of sediment trapped in wet and dry seasons, and the coverage area was a dry season without structures. By adding a permeable structure, the maximum amount of sediment trapped in the wet season reaches 1.52 m in three years of simulation. It can be concluded that permeable structures constructed along the coast can trap the sediment. The placement, length, and number of structures should be considered to produce a wider coverage area. In the future, the sustainability of this adaptive concept is expected to enhance the coastal restoration in Demak coastal area.
... One very important ecosystem value of mangroves is its ability to store large quantities of carbon above and below ground. Degradation of the health of mangrove forests is immediately reflected in this potential by the carbon fluxes (Senger et al., 2021). ...
The Bonaire National Marine Park was established in 1979. The marine park protects 2,700 hectares of coral reefs, seagrass beds and mangrove forests. Seventy-five IUCN Red List critically endangered, endangered or vulnerable species, and 15 CITES Appendix I species, are recorded in the marine park. The marine park includes two Ramsar sites: Lac Bay (the largest semi-enclosed bay in the Dutch Caribbean) and Klein Bonaire (an uninhabited satellite island located approximately 700 m offshore). Bonaire’s coral reefs are considered some of the healthiest in the Caribbean. The marine park forms the cornerstone of the island economy.
The management plan provides specific recommendations for the period 2022-2028, centered around six conservation strategies:
1. Optimize protection of key habitats and species.
2. Improve sustainable recreation.
3. Encourage sustainable fishing.
4. Control invasive species and disease.
5. Support restoration of key habitats and species.
6. Influence policy and legislation to improve park management.
This management plan was developed in close co-operation with local stakeholders. This document also serves as the management plan for the Ramsar sites Lac Bay and Klein Bonaire.
... Under-lake mining significantly influences aquifer connectivity and surface flows via subsidence disturbance [12]. To protect the sensitive eco-environment and ensure the delivery of ecosystem services, it is essential to quantify the transmutation of the ecosystem in order to develop ecological compensation criteria and a decision-making basis [11,13]. ...
Under the growing restrictions of the Chinese eco-environmental policies, the impact of under-lake coal mining on wetlands is receiving increasing attention from both coal mining enterprises and local governments. This paper focuses on the impact of under-lake coal mining on the Nansi Lake wetland from 1991 to 2021. Field measurements, resident surveys, and remote sensing inversion were comprehensively employed to quantitatively assess the impact. The calculation of the assessment indicators refers to the elastic coefficient, the information for which comes from four major categories of ecosystem service values (ESVs) and eight sub-ESVs. According to the results of the remote sensing interpretation and inversion, by 2021 the range had enlarged by 32.3 km2, and the water depth had increased by 1.9 m in the mining-disturbed area relative to 1991. The ESV fluctuations in the Nansi Lake wetland also exhibited a generally increasing trend over time. Our results show that the under-lake mining disturbs the ESVs, but the disturbance is not sufficient to result in significant consequences. Based on the data analysis, we suggest several well-directed, appropriate restoration strategies to achieve the desired objectives and target the response of the ESV changes. Such measures will help to relieve some of the anxiety and concern about the wetland changes caused by the under-lake mining.
... Hal tersebut juga yang membuat stasiun 1 memiliki nilai kandungan karbon dan stok karbon yang tertinggi diantara stasiun lain. Lokasi stasiun 3 yang berdekatan dengan pantai akan memiliki paparan pasang surut yang lebih sering, daripada stasiun 1 dan 2. Kondisi pasang surut akan meningkatkan kadar oksigen pada wilayah tersebut naik, sehingga dapat memacu bakteri untuk mengoksidasi karbon dan melepaskannya ke atmosfer melalui respirasi (Senger et al., 2021). Hal tersebut dapat membuat nilai kandungan karbon pada lokasi yang dekat dengan pantai akan menurun, ditambah lagi dengan kondisi tutupan sampah di lokasi sebesar 25%. ...
Mangrove memiliki peranan penting baik secara fisik, ekonomi maupun ekologi. Salah satu fungsi ekologi tersebut adalah sebagai penyimpan karbon di alam. Upaya perlindungan dan pelestarian mangrove membutuhkan data sebagai acuan pembuatan kebijakan pengelolaan mangrove yang berkelanjutan. Tujuan penelitian ini untuk mengetahui komposisi dan struktur vegetasi mangrove serta mengetahui stok karbon sedimen di Hutan Mangrove Pandansari, Kabupaten Brebes. Penentuan lokasi ditetapkan berdasarkan tahun penanaman mangrove hasil program rehabilitasi, yaitu tahun penanaman 2005, 2008, 2011, 2014 dan 2017. Pengambilan data vegetasi dilakukan dengan metode purposive sampling dengan setiap stasiun dipasang plot berukuran 10 x 10 m. Pengambilan sampel sedimen karbon menggunakan bor gambut pada tiga kedalaman, yaitu 5 – 10 cm, 72,5 – 77,5 cm dan 197,5 – 202,5 cm. Hasil penelitian menunjukkan bahwa di Hutan Mangrove Pandansari ditemukan tiga jenis mangrove, yaitu Rhizophora mucronata, Avicennia marina dan A. alba. Secara umum, vegetasi mangrove di lokasi penelitian memiliki nilai kerapatan >1.500 ind/ha yang didominasi oleh R. mucronata. Nilai Indeks Keanekaragaman (H’) dan Keseragaman (J’) mangrove di lokasi penelitian termasuk dalam kategori rendah. Stok karbon sedimen secara berturut-turut di stasiun 1 – 5 sebesar 1053,53 ton/ha, 747,63 ton/ha, 381,67 ton/ha, 612,11 ton/ha dan 798 ton/ha. Berdasarkan hasil tersebut, semakin tua usia pohon tidak mempengaruhi jumlah stok karbon yang disimpan di sedimen. Kedalaman 197,5–202,5 cm menjadi kedalaman yang paling banyak menyimpan karbon. Mangrove is one type of dicotyledonous vegetation found in coastal areas, and is influenced by tides. Mangroves have an important role both physically, economically and ecologically. One of these ecological functions is to store carbon in nature. Efforts to protect and conserve mangroves require data as a reference for making sustainable mangrove management policies. This study aims to determine the composition and structure of mangrove vegetation and to determine the carbon stock of sediments in the Pandansari Mangrove Forest, Brebes. The research location was determined based on the year of planting of mangroves as a result of the rehabilitation program, namely the planting years of 2005, 2008, 2011, 2014 and 2017. Vegetation data was collected by purposive sampling method with each station installed a plot measuring 10 x 10 m. Carbon sediment samples were taken using peat drills at three depths, namely 5 – 10 cm, 72.5 – 77.5 cm and 197.5 – 202.5 cm. The results showed that in the Pandansari Mangrove Forest, three types of mangroves were found, namely Rhizophora mucronata, Avicennia marina and A. alba. In general, the mangrove vegetation at the study site had a density value of > 1,500 ind/ha which was dominated by R. mucronata. The value of the Diversity Index (H') and Uniformity (J') of the mangroves at the study site was included in the low category. Sedimentary carbon stocks at stations 2005, 2008, 2011, 2014 and 2017 were 1053.53 tons/ha, 747.63 tons/ha, 381.67 tons/ha, 612.11 tons/ha and 798 tons/ha, respectively. Based on these results, the older the tree age does not affect the amount of carbon stock stored in the sediment. The depth of 197.5–202.5 cm is the depth that stores the most carbon.
... In addition, climate and human-induced stressors, such as increasing nutrients and temperatures are increasing and interacting to reduce seagrasses in this and other regions (Burkholder et al. 2007). Multiple stressors can increase mangrove mortality (Radabaugh et al. 2020;Lagomasino et al. 2021) and also impact trait development and carbon sequestration (Senger et al. 2020). How interacting stressors in coastal wetlands affect functional trait development, carbon sequestration, and storage remains a global research goal. ...
Mangrove forests and seagrass meadows provide critical ecosystem services, including the accumulation of “blue carbon.” Plants' functional traits could influence this blue carbon accumulation. To test for interactions among functional traits and blue carbon accumulation, we conducted a study in connected mangrove‐seagrass coastal ecosystems in southeast Florida (USA). We quantified how plants' above‐ground traits correlated with sediment nutrient content, and how changes in traits along inland‐to‐coastal gradients influenced inorganic and organic carbon storage potential. Physical traits of Thalassia testudinum were higher at sites with higher sediment phosphorus (SP) and nitrogen (SN) concentrations. Sediment organic carbon concentrations were positively correlated to T. testudinum physical traits. Root density, pneumatophore abundance, specific leaf area, leaf toughness, leaf nitrogen, and phosphorus content were positively correlated with SN concentrations in the mangrove forest coastal fringe. Mangrove leaf thickness and root complexity index were negatively correlated with SP concentrations in the coastal fringe. Our results also indicate that seagrass above‐ground traits and blue carbon were strongly correlated in areas with higher sediment nutrient concentrations. Moreover, mangrove root complexity is coupled with phosphorus limitation, whereby highly complex root systems develop with decreasing phosphorus concentrations. Distinct functional traits of plants drive variation in carbon retention capacity even in interconnected ecosystems.
... Investigations of GHG fluxes across different restoration stages of mangrove forests have revealed variable responses of CO 2 fluxes to deforestation. Higher, lower and no difference from deforested/ degraded or bare mangrove sediment compared to forested mangrove sediment have been observed (Alongi et al., 1998;Bulmer et al., 2017;Castillo et al., 2017;Hien et al., 2018a;Senger et al., 2021). Lower CH 4 fluxes and emissions have been observed from deforested mangrove sediment and mudflats compared to forested mangrove sediments (Castillo et al., 2017;Soper et al., 2019). ...
Forested coastal wetlands are globally important systems sequestering carbon and intercepting nitrogen pollution from nutrient-rich river systems. Coastal wetlands that have suffered extensive disturbance are the target of comprehensive restoration efforts. Accurate assessment of restoration success requires detailed mechanistic understanding of wetland soil biogeochemical functioning across restoration chrono-sequences, which remains poorly understood for these sparsely investigated systems. This study investigated denitrification and greenhouse gas fluxes in mangrove and Melaleuca forest soils of Vietnam, using the ¹⁵N-Gas flux method. Denitrification-derived N2O was significantly higher from Melaleuca than mangrove forest soils, despite higher potential rates of total denitrification in the mangrove forest soils (8.1 ng N g⁻¹ h⁻¹) than the Melaleuca soils (6.8 ng N g⁻¹ h⁻¹). Potential N2O and CO2 emissions were significantly higher from the Melaleuca soils than from the mangrove soils. Disturbance and subsequent recovery had no significant effect on N biogeochemistry except with respect to the denitrification product ratio in the mangrove sites, which was highest from the youngest mangrove site. Potential CO2 and CH4 fluxes were significantly affected by restoration in the mangrove soils. The lowest potential CO2 emissions were observed in the mid-age plantation and potential CH4 fluxes decreased in the older forests. The mangrove system, therefore, may remove excess N and improve water quality with low greenhouse gas emissions, whereas in Melaleucas, increased N2O and CO2 emissions also occur. These emissions are likely balanced by higher carbon stocks observed in the Melaleuca soils. These mechanistic insights highlight the importance of ecosystem restoration for pollution attenuation and reduction of greenhouse gas emissions from coastal wetlands. Restoration efforts should continue to focus on increasing wetland area and function, which will benefit local communities with improved water quality and potential for income generation under future carbon trading.
... Mangrove forests (MFs) are of great ecological and economic importance to humans, especially from coastal communities [1]; they are highly productive [2][3][4], generate large amounts of nutrients and organic matter that subsequently contributes to soil formation and coastal erosion control [5,6], they are ecosystems that provide food, shelter and breeding to a wide variety of flora and fauna including commercial species, and they are key to reductions in the greenhouse gases (GHG) effect. The conditions of the floodable soil of MFs allow GHG to be purified and hijacked in the soil by biogeochemical processes, degradating organic matter which is then incorporated into the soil [7,8]. ...
The pigment content in leaves has commonly been used to characterize vegetation condition. However, few studies have assessed temporal changes of local biotic and abiotic factors on leaf pigments. Here, we evaluated the effect of local environmental variables and tree structural characteristics , in the chlorophyll-a leaf concentration (Chl-a) associated with temporal change in two mangrove species. Rhizophora mangle (R. mangle) and Avicennia germinans (A. germinans) trees of a fringe mangrove forest (FMF) and lower basin mangrove forest (BMF) were visited over a period of one year, to obtain radiometric readings at leaf level to estimate Chl-a. Measurements on tree characteristics included diameter at breast height (DBH), basal area (BA), and maximum height (H). Environmental variables included soil interstitial water temperature (Ti), salinity (Si), and dissolved oxygen (Oi), flood level (fL), ambient temperature (Tamb), and relative humidity (Hrel). Generalized linear models and covariance analysis showed that the variation of Chl-a is mainly influenced by the species, the interaction between species and mangrove forest type, DBH, seasonality and its influence on the species, soil conditions, and fL. Studies to assess spatial and temporal change on mangrove forests using the spectral characteristics of the trees should also consider the temporal variation of leave chlorophyll-a concentration.
Coastal wetlands including mangrove play a vital role in regulating the local and global carbon cycle. Coastal areas contribute greatly to the carbon exchange process due to the complex interactions that occur between the atmosphere, land, and oceans. One of the important components in coastal carbon dynamics is CO2 gas exchange between soil, water and the atmosphere. This study aims to assess CO2 efflux across various land covers (namely natural mangrove, restored mangrove, and converted mangroves to oil palm and aquaculture pond) in the coastal areas of North Sumatra Province, and analyze the effect of sea tides and ebbs on the rate of CO2 efflux and their connection with the number and area of macrozoobenthos burrows. We applied direct sampling by using the static closed chamber method attached to portable CO2 analyzer. The mean of CO2 efflux in natural mangrove forest land covers was 866±585 mgCO2/m2/h during low tide conditions and 1137±792 mgCO2/m2/h during high tide conditions, followed by oil palm plantations at 760.71±341 mgCO2/m2/h, restored mangroves during low tide of 575.24±326 mgCO2/m2/h and 597.11±180 mg CO2/m2/h during high tide conditions, and the lowest was recorded in ponds at 588.55±358 mgCO2/m2/h. Further, we observed that tidal conditions affect the magnitudes of CO2 efflux in natural and restored mangrove forests, and we did not observe similar pattern in oil palms and ponds since these land covers were not influenced by regular tidal input. We also observed that no significant relationship between the number and area of macrozoobenthos burrows and CO2 efflux. Our findings suggest that CO2 effluxes in coastal wetlands are highly dynamic and presumably driven by complex factors and therefore, understanding their magnitudes and drivers requires extensive measurement covering large spatial and temporal scales.
Mangroves are among the most productive ecosystems worldwide, providing numerous ecological and socio- economic co-benefits. Though highly adapted to fluctuating environmental conditions, increasing disturbances from climate change and human activities have caused significant losses. With increasing environmental un- certainties, adaptive management is necessary to monitor and evaluate changes, and to understand drivers of mangrove decline. Effective management requires access to accurate, current, and multitemporal data on mangrove cover, but such data is often lacking or inaccessible to managers. We present mangrove cover maps for Puerto Rico, the U.S. Virgin Islands, and the British Virgin Islands for the years 2020, 2021, and 2022. We used the Random Forest machine learning technique in Google Earth Engine (GEE) to classify Sentinel-2 multispectral imagery (MSI) and created mangrove vegetation maps at 10 m resolution, with classification accuracies greater than 85%. We host and present the maps in an easy-to-use GEE decision support tool (DST) for managers and policy makers that allows for evaluation of change over time. We also provide a mapping workflow fully implemented in GEE that allows for the production of subsequent maps with minimal technical expertise required. The DST and mapping workflow can help users to detect impacts of disturbances on mangrove vege- tation and to monitor progress of conservation interventions such as rehabilitation or legal protection. Furthermore, our mapping approach differentiates between intact and degraded mangrove vegetation, and the increased spatial resolution of Sentinel-2 MSI imagery allowed us to capture mangrove patches that had not been previously mapped by studies using coarser resolution imagery. Our assessment of mangrove cover change be- tween years indicated patterns of loss and recovery likely associated with disturbances, natural recovery and/or human driven restoration.
This systematic literature review examines mercury contamination in the mangrove ecosystems, associating the complex interactions between climate change and mercury contamination, amplifying risks to the environment and human populations. Mercury, a highly toxic non-essential trace element, exist naturally and can be massively produced through anthropogenic activities such as artisanal gold mining, coal combustion, and non-ferrous metals production poses a significant threat to public health, particularly over the ingestion of polluted fish. Atmospheric deposition and conversion of inorganic mercury into the more toxic methylmercury are major pathways for mercury contamination in mangrove ecosystems. Climate change worsens the issue by impacting mercury distribution, bioavailability, and fate in mangrove environments. This has implications for marine and freshwater biodiversity, disrupting ecological interactions and endangering populations. Rising sea levels, altered precipitation patterns, and elevated temperatures associated with climate change influence mercury dynamics and concentrations in aquatic organism such as fish. As mercury in fish, a significant part of diets across the globe, raises concerns for human health, the development of successful measures to reduce mercury pollution and its related dangers relies on a thorough understanding of these relationships. The review will support policymaking aligned with the Minamata Convention and aid in developing effective strategies to mitigate mercury pollution. Protecting human health and the mangrove biodiversity is crucial for the sustainability of fish in the face of climate change.
Blue carbon has been proposed as a nature-based solution for climate change mitigation; however, a limited number of published works and data and knowledge gaps hinder the development of small island developing states' (SIDS) national blue carbon resources globally. This paper reviews the blue carbon ecosystems of Seychelles as a case study in the context of SIDS, comparing estimations by the Blue Carbon Lab and recent blue carbon (mangrove and seagrass) evaluations submitted to the Seychelles national government. Mangroves (2195 ha, 80% in Aldabra Atoll) and seagrasses (142,065 ha) dominate in Seychelles, with coral reefs having the potential for carbon sequestration (169,000 ha). Seychelles is on track to protecting its blue carbon, but these systems are threatened by rising sea levels, coastal squeeze, erosion, severe storms, and human activities. The importance of carbon inventories, accounting institutions, and continuous monitoring of blue carbon systems is discussed. Blue accounting is necessary for accurate accounting of carbon sequestration and carbon storage, generating carbon credits, and representing impactful reductions in greenhouse gases for NDCs. Challenges and opportunities include policy legislation regarding ownership rights, accreditation and certification for carbon credits, sustainable financing mechanisms like natural asset companies and blue tokens, local engagement for long-term success, and carbon market dynamics following COP27. The restoration and regulation of blue carbon resources for optimal ecosystem services delivery, carbon inventories, and blue carbon policy are recommended development priorities. Blue carbon ecosystems have the potential to contribute to NDCs of SIDS while simultaneously offering sustainable development pathways for local communities through the multiple ecosystem services they provide.
Non-destructive approaches for estimating the carbon sequestration potential of mangroves are growing in acceptance, as they are eco-friendly and do not harm trees. The present study was piloted for mangroves, especially the Avicennia marina of the Red Sea region. The study aimed to use allometric models for mangrove biomass estimation based on the normalized difference vegetation index (NDVI) derived from satellite imagery. The method was validated by comparing the results with the previous studies that adopted the destructive method. To achieve the study aim, three major steps were adopted; namely, (1) Mangrove mapping using satellite imagery, (2) Calculation of carbon sequestration potential by applying the allometric equations, and (3) Mangrove sediments sampling and analysis were carried out in three stations along the Egyptian coast to determine soil organic carbon stock. Results from the study revealed that mangroves grew at 56 locations along the Red Sea coast. The results of the present study showed that the average carbon stock value for the Red Sea mangroves was 0.33 (ton C/ hectare) (1.2 ton CO2/ hectare). Thus, the Red Sea mangroves can share by at least USD 27.5M value of mangrove forest ecosystem services. Middle station on the Saudi Arabia coast was found to be the most carbon-rich mangrove region with 26.9 ton C/ hectare, while one station in northern Egypt recorded the lowest carbon sequestration potential, with a total carbon stock of 0.06 ton C/ hectare. Therefore, the current study suggested that the satellite imagery analysis combined with allometric equations can be applied far more rapidly and inaccessibly compared to traditional field inventory techniques, and it can potentially be an effective tool for estimating mangrove biomass and carbon storage with increased accuracy through further model calibration.
Abs tract Mangrove forests are considered one of the most productive components of coastal food chains and a source of energy supply. They provide various goods and services with ecological, economic, socio-cultural, and aesthetic benefits to meet society's needs. However, mangrove forests are considered one of the most sensitive and vulnerable habitats in the face of environmental hazards and human pressures. Accordingly, the study investigated the natural features of the Khamir and Qeshm mangrove forests and management boundaries in this area. According to previous studies, it cannot be limited to administrative borders and country divisions to protect and plan this natural habitat according to its conservation history. Instead, it should be protected and managed by considering the biological border and the distribution of mangrove forest cover in this area. Therefore, multifaceted conservation management of the country's unique mangrove habitat requires that its ecosystem services be planned in the framework of a management plan based on habitat zoning. In addition, the development of human activities in this area should be planned within management and protection limits.
Ocean & Coastal Management (OCMA) has significantly contributed to international ocean and coastal management, policy-making, governance, and other related research fields. This article highlights the contributions OCMA has made in these areas by summarizing the trends in 3782 articles published from 1992 to 2021. Using bibliometric and knowledge graph visualization analyses, this article systematically reviews the historical research contributions in each field and identifies emerging topics in recent years, such as the Blue Economy, shipping, and marine litter. OCMA has made a substantial positive impact on global ocean and coastal management by fostering collaboration among scholars and practitioners, advancing policy and regulatory development, enhancing management practices, increasing public awareness of environmental protection, and promoting sustainable development. In addition to its critical academic role in the field of ocean and coastal management, OCMA has also facilitated advancements in related research and practice (such as coastal erosion, litter, port management), ultimately contributing to the protection of global ocean and coastal ecosystems.
Mangroves provide multiple ecosystem services and are essential for mitigating global warming owing to their capacity to store large carbon (C) stocks. Due to widespread mangrove degradation, actions have been implemented to restore them worldwide. An important representative case in Colombia is the Ciénaga Grande de Santa Marta’s restoration plan. This management intervention focused on restoring the natural hydrological functioning after massive mangrove mortality (~25,000 ha) due to soil hyper-salinization after river water input from the Magdalena River was eliminated. A partial recovery occurred during subsequent years, and hydrological management is still being implemented today. To understand how the degradation and subsequent management have affected mangrove C stocks, we compared C stocks in stands with different intervention levels reflected in their current forest structure. We found that the total C stock (398–1160 Mg C ha−1) was within the range measured in other neotropical mangroves without vegetation deterioration. The aboveground C was significantly higher in the stands where hydraulic connectivity was restored. By contrast, the belowground C was higher in the stands with low hydraulic connectivity due to channel clogging and a lack of sufficient maintenance. Our results show that hydrological management measures influenced above- and belowground C stocks, even at a 2 m depth. In addition, a strong indirect relationship useful for estimating carbon content from organic matter content was found.
Mangrove ecosystems are an important natural carbon sink that accumulate and store large amounts of organic carbon (Corg), in particular in the sediment. However, the magnitude of carbon stocks and the rate of carbon accumulation (CAR) vary geographically due to a large variation of local factors. In order to better understand the blue carbon sink of mangrove ecosystems, we measured organic carbon stocks, sources and accumulation rates in three Indonesian mangrove ecosystems with different environmental settings and conditions; (i) a degraded estuarine mangrove forest in the Segara Anakan Lagoon (SAL), Central Java, (ii) an undegraded estuarine mangrove forest in Berau region, East Kalimantan, and (iii) a pristine marine mangrove forest on Kongsi Island, Thousand Islands, Jakarta. In general, Corg stocks were higher in estuarine than in marine mangroves, although a large variation was observed among the estuarine mangroves. The mean total Corg stock in Berau (615 ± 181 Mg C ha-1) is twice as high as that in SAL (298 ± 181 Mg C ha-1). However, the Segara Anakan Lagoon displayed large within-system variation with a much higher Corg stock in the eastern (483 ± 124 Mg C ha-1) than in the central lagoon (167 ± 36 Mg C ha-1). The predominant accumulation of autochthonous mangrove organic matter likely contributed to the higher Corg stocks in Berau and the eastern SAL. Interestingly, the CAR distribution pattern in SAL is opposite to that of its Corg stocks. The central SAL that receives high sediment inputs from the hinterland has a much higher CAR than the eastern SAL (658 ± 311 g C m-2 yr-1 and 194 ± 46 g C m-2 yr-1, respectively), while Berau has one of the highest CAR (1722 ± 183 g C m-2 yr-1) ever measured. It appears that these large differences are driven by the environmental setting and conditions, mainly sediment dynamics and hydrodynamics, landform, and vegetation conditions. It is inferred that quantifying carbon accumulation in sediments is a useful tool in estimating the present-day carbon storage of mangrove ecosystems. This is a precondition for taking measures under REDD+ (Reducing Emissions from Deforestation and Forest Degradation and the role of conservation, sustainable management of forests and enhancement of forest carbon stocks in developing countries) schemes.
The blue carbon paradigm has evolved in recognition of the high carbon storage and sequestration potential of mangrove, saltmarsh and seagrass ecosystems. However, fluxes of the potent greenhouse gases CH4 and N2O, and lateral export of carbon are often overlooked within the blue carbon framework. Here, we show that the export of dissolved inorganic carbon (DIC) and alkalinity is approximately 1.7 times higher than burial as a long-term carbon sink in a subtropical mangrove system. Fluxes of methane offset burial by approximately 6%, while the nitrous oxide sink was approximately 0.5% of burial. Export of dissolved organic carbon and particulate organic carbon to the coastal zone is also significant and combined may account for an atmospheric carbon sink similar to burial. Our results indicate that the export of DIC and alkalinity results in a long-term atmospheric carbon sink and should be incorporated into the blue carbon paradigm when assessing the role of these habitats in sequestering carbon and mitigating climate change.
Quantification the Dissolved and Particulate organic carbon in marine waters is an essential step towards ecosystem modeling and understanding carbon sequestration processes. A detailed view of estimated and recorded carbon concentration from Arctic to Antarctic is the prime goal of this review. This review compiles some of the important research work carried out in quantifying the organic carbon available in off shore and open waters and in coral reef environment. The cited literatures were collected, grouped and carefully analyzed to give a comprehensive view on current status of marine environment with regard to distribution of dissolved and particulate organic carbon.
Keywords: DOC, POC, continental shelf waters, open sea waters, coral reef environment.
This book presents a comprehensive overview and analysis of mangrove ecological processes, structure, and function at the local, biogeographic, and global scales and how these properties interact to provide key ecosystem services to society. The analysis is based on an international collaborative effort that focuses on regions and countries holding the largest mangrove resources and encompasses the major biogeographic and socio-economic settings of mangrove distribution. Given the economic and ecological importance of mangrove wetlands at the global scale, the chapters aim to integrate ecological and socio-economic perspectives on mangrove function and management using a system-level hierarchical analysis framework. The book explores the nexus between mangrove ecology and the capacity for ecosystem services, with an emphasis on thresholds, multiple stressors, and local conditions that determine this capacity. The interdisciplinary approach and illustrative study cases included in the book will provide valuable resources in data, information, and knowledge about the current status of one of the most productive coastal ecosystem in the world.
Mangrove soils represent a large sink for otherwise rapidly recycled carbon (C). However, widespread deforestation threatens the preservation of this important C stock. It is therefore imperative that global patterns in mangrove soil C stocks and their susceptibility to remineralization are understood. Here, we present patterns in mangrove soil C stocks across hemispheres, latitudes, countries and mangrove community compositions, and estimate potential annual CO2 emissions for countries where mangroves occur. Global potential CO2 emissions from soils as a result of mangrove loss were estimated to be ~7.0 Tg CO2e yr⁻¹. Countries with the highest potential CO2 emissions from soils are Indonesia (3,410 Gg CO2e yr⁻¹) and Malaysia (1,288 Gg CO2e yr⁻¹). The patterns described serve as a baseline by which countries can assess their mangrove soil C stocks and potential emissions from mangrove deforestation.
In this article, the predictive accuracy of 48 published pedotransfer functions (PTFs) for predicting soil bulk density (BD) was evaluated using soil database from the United States. In addition, new PTF for predicting BD using inputs of organic carbon content (OC) was proposed and validated. The results showed that 8 of the evaluated PTFs showed high performances (EF > 0.50, RMSE < 0.18 Mg m À3), 7 PTFs showed moderate performances (0.20 < EF < 0.50, 0.17 < RMSE < 0.20), 9 PTFs showed low performances (0 < EF < 0.20), while the rest of PTFs showed poor performances (EF < 0, RMSE > 0.24). New PTF has been developed using the entire database. The proposed PTF (BD = 1.449e À0.03OC , R 2 = 0.6802) requires only the organic carbon content as input. The developed PTF was compared to the best 10 performing PTFs evaluated in the study using dataset of 45,195 samples. The results showed that the new PTF had the best performance (EF = 0.59, RMSE = 0.13 Mg m À3). Ó 2016 Ain Shams University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Aim
To provide high‐resolution local, regional, national and global estimates of annual mangrove forest area from 2000 through to 2012 with the goal of driving mangrove research questions pertaining to biodiversity, carbon stocks, climate change, functionality, food security, livelihoods, fisheries support and conservation that have been impeded until now by a lack of suitable data.
Location
Global, covering 99% of all mangrove forests.
Methods
We synthesized the Global Forest Change database, the Terrestrial Ecosystems of the World database and the Mangrove Forests of the World database to extract mangrove forest cover at high spatial and temporal resolutions. We then used the new database to monitor mangrove cover at the global, national and protected area scales.
Results
Countries showing relatively high amounts of mangrove loss include Myanmar, Malaysia, Cambodia, Indonesia and Guatemala. Indonesia remains by far the largest mangrove‐holding nation, containing between 26% and 29% of the global mangrove inventory with a deforestation rate of between 0.26% and 0.66% per year. We have made our new database, CGMFC‐21, freely available.
Main conclusions
Global mangrove deforestation continues but at a much reduced rate of between 0.16% and 0.39% per year. Southeast Asia is a region of concern with mangrove deforestation rates between 3.58% and 8.08%, this in a region containing half of the entire global mangrove forest inventory. The global mangrove deforestation pattern from 2000 to 2012 is one of decreasing rates of deforestation, with many nations essentially stable, with the exception of the largest mangrove‐holding region of Southeast Asia. We provide a standardized spatial dataset that monitors mangrove deforestation globally at high spatio‐temporal resolutions. These data can be used to drive the mangrove research agenda, particularly as it pertains to monitoring of mangrove carbon stocks and the establishment of baseline local mangrove forest inventories required for payment for ecosystem service initiatives.
Among the many ecosystem services provided by mangrove ecosystems, their role in carbon (C) sequestration and storage is quite high compared to other tropical forests. Mangrove forests occupy less than 1 % of tropical forested areas but account for approximately 3 % of global carbon sequestration by tropical forests. Yet there remain many areas where little data on the size and variation of mangrove C stocks exist. To address this gap and examine the range of C stocks in mangroves at landscape scales, we quantified C stocks of Honduran mangroves along the Pacific and Caribbean coasts and the Bay Islands. We also examined differences in ecosystem C stocks due to size and structure of mangrove vegetation found in Honduras. Ecosystem C stocks ranged from 570 Mg C ha−1 in the Pacific coast to ~1000 Mg C ha−1 in Caribbean coast and the Bay Islands. Ecosystem C stocks on the basis of mangrove structure were 1200, 800 and 900 Mg C ha−1, in low, medium and tall mangroves, respectively. We did not find significant differences in ecosystem C stocks on the basis of location (Pacific coast, Caribbean coast and Bay Islands) or mangrove type (low, medium and tall). Mangrove soils represented the single largest pool of total C in these ecosystems, with 87, 81 and 94 % at the Pacific coast, Caribbean coast and the Bay Islands, respectively. While there were no significant differences in total ecosystem stocks among mangrove types, there were differences in where carbon is stored. Mangrove soils among low, medium and tall mangroves contained 99, 93 and 80 % of the total ecosystem C stocks. In addition, we found a small yet significant negative correlation between vegetation C pools and pore water salinity and pH at the sampled sites. Conversion of mangroves into other land use types such as aquaculture or agriculture could result in loses of these soil C reserves due to mineralization and oxidation. Coupled with their other ecosystem services, an understanding of the size of mangrove ecosystem C stocks underscores their values in the formulation of conservation and climate change mitigation strategies in Central America.
The production of shrimp (Penaeus spp.) by means of coastal pond systems has been a traditional practice in Asia for hundreds of years. However, advances in technology coupled with an increased international market demand for shrimp led to the development of intensive aquaculture systems that departed from traditional sustainable systems. In many instances these intensive systems were poorly planned and/or managed and have since proven to be unsustainable, with the result that large areas of “land, ”much of it former coastal wetlands, now lie idle and unproductive, and new sites are being developed in an effort to maintain production output (Stevenson 1997).
Temperate mangrove forests in New Zealand have increased in area over recent
decades. Expansion of temperate mangroves in New Zealand is associated with
perceived loss of other estuarine habitats, and decreased recreational and
amenity values, resulting in clearing of mangrove forests. In the tropics,
changes in sediment characteristics and carbon efflux have been reported
following mangrove clearance. This is the first study in temperate mangrove
(Avicennia marina) forests investigating the impact of clearing on sediment CO2 efflux
and associated biotic and abiotic factors.
Sediment CO2 efflux rates from intact (168.5 ± 45.8 mmol m−2 d−1) and cleared (133.9 ± 37.2 mmol m−2 d−1) mangrove
forests in New Zealand are comparable to rates measured in tropical mangrove
forests. We did not find a significant difference in sediment CO2
efflux rates between intact and cleared temperate mangrove forests.
Pre-shading the sediment for more than 30 min prior to dark chamber
measurements was found to have no significant effect on sediment CO2
efflux. This suggests that the continuation of photosynthetic CO2
uptake by biofilm communities was not occurring after placement of dark
chambers. Rather, above-ground mangrove biomass, sediment temperature and
chlorophyll a concentration were the main factors explaining the variability
in sediment CO2 efflux in intact mangrove forests. The main factors
influencing sediment CO2 efflux in cleared mangrove forest sites were
sediment organic carbon concentration, nitrogen concentration and sediment
grain size. Our results show that greater consideration should be given
regarding the rate of carbon released from mangrove forest following
clearance and the relative contribution to global carbon emissions.
Riverine wetlands are created and transformed by geomorphological processes
that determine their vegetation composition, primary production and soil
accretion, all of which are likely to influence C stocks. Here, we compared
ecosystem C stocks (trees, soil and downed wood) and soil N stocks of
different types of riverine wetlands (marsh, peat swamp forest and
mangroves) whose distribution spans from an environment dominated by river
forces to an estuarine environment dominated by coastal processes. We also
estimated soil C sequestration rates of mangroves on the basis of soil C
accumulation. We predicted that C stocks in mangroves and peat swamps would
be larger than marshes, and that C, N stocks and C sequestration rates would
be larger in the upper compared to the lower estuary. Mean C stocks in
mangroves and peat swamps (784.5 ± 73.5 and 722.2 ± 63.6 MgC ha−1, respectively) were higher than those of marshes
(336.5 ± 38.3 MgC ha−1). Soil C and N stocks of mangroves were
highest in the upper estuary and decreased towards the lower estuary. C
stock variability within mangroves was much lower in the upper estuary
(range 744–912 MgC ha−1) compared to the intermediate and lower estuary
(range 537–1115 MgC ha−1) probably as a result of a highly dynamic
coastline. Soil C sequestration values were 1.3 ± 0.2 MgC ha−1 yr−1 and were similar across sites. Estimations of C stocks
within large areas need to include spatial variability related to vegetation
composition and geomorphological setting to accurately reflect variability
within riverine wetlands.
Mangroves provide a wide range of ecosystem services, including nutrient cycling, soil formation, wood production, fish spawning grounds, ecotourism and carbon (C) storage1. High rates of tree and plant growth, coupled with anaerobic, water-logged soils that slow decomposition, result in large long-term C storage. Given their global significance as large sinks of C, preventing mangrove loss would be an effective climate change adaptation and mitigation strategy. It has been reported that C stocks in the Indo-Pacific region contain on average 1,023 MgC ha−1 (ref. 2). Here, we estimate that Indonesian mangrove C stocks are 1,083 ± 378 MgC ha−1. Scaled up to the country-level mangrove extent of 2.9 Mha (ref. 3), Indonesia’s mangroves contained on average 3.14 PgC. In three decades Indonesia has lost 40% of its mangroves4, mainly as a result of aquaculture development5. This has resulted in annual emissions of 0.07–0.21 Pg CO2e. Annual mangrove deforestation in Indonesia is only 6% of its total forest loss6; however, if this were halted, total emissions would be reduced by an amount equal to 10–31% of estimated annual emissions from land-use sectors at present. Conservation of carbon-rich mangroves in the Indonesian archipelago should be a high-priority component of strategies to mitigate climate change.
Mangrove forests have survived a number of catastrophic climate events since first appearing along the shores of the Tethys Sea during the late Cretaceous-Early Tertiary. The existence of mangrove peat deposits worldwide attests to past episodes of local and regional extinction, primarily in response to abrupt, rapid rises in sea level. Occupying a harsh margin between land and sea, most mangrove plants and associated organisms are predisposed to be either resilient or resistant to most environmental change. Based on the most recent Intergovernmental Panel on Climate Change (IPCC) forecasts, mangrove forests along arid coasts, in subsiding river deltas, and on many islands are predicted to decline in area, structural complexity, and/or in functionality, but mangroves will continue to expand polewards. It is highly likely that they will survive into the foreseeable future as sea level, global temperatures, and atmospheric CO2 concentrations continue to rise.
The importance of mangrove forests in carbon sequestration and coastal protection has been widely acknowledged. Large-scale damage of these forests, caused by hurricanes or clear felling, can enhance vulnerability to erosion, subsidence and rapid carbon losses. However, it is unclear how small-scale logging might impact on mangrove functions and services. We experimentally investigated the impact of small-scale tree removal on surface elevation and carbon dynamics in a mangrove forest at Gazi bay, Kenya. The trees in five plots of a Rhizophora mucronata (Lam.) forest were first girdled and then cut. Another set of five plots at the same site served as controls. Treatment induced significant, rapid subsidence (−32.1±8.4 mm yr−1 compared with surface elevation changes of +4.2±1.4 mm yr−1 in controls). Subsidence in treated plots was likely due to collapse and decomposition of dying roots and sediment compaction as evidenced from increased sediment bulk density. Sediment effluxes of CO2 and CH4 increased significantly, especially their heterotrophic component, suggesting enhanced organic matter decomposition. Estimates of total excess fluxes from treated compared with control plots were 25.3±7.4 tCO2 ha−1 yr−1 (using surface carbon efflux) and 35.6±76.9 tCO2 ha−1 yr−1 (using surface elevation losses and sediment properties). Whilst such losses might not be permanent (provided cut areas recover), observed rapid subsidence and enhanced decomposition of soil sediment organic matter caused by small-scale harvesting offers important lessons for mangrove management. In particular mangrove managers need to carefully consider the trade-offs between extracting mangrove wood and losing other mangrove services , particularly shoreline stabilization, coastal protection and carbon storage.
Mangroves are ecologically and economically important forests of the tropics. They are highly productive ecosystems with rates of primary production equal to those of tropical humid evergreen forests and coral reefs. Although mangroves occupy only 0.5% of the global coastal area, they contribute 10-15% (24 Tg C y(-1)) to coastal sediment carbon storage and export 10-11% of the particulate terrestrial carbon to the ocean. Their disproportionate contribution to carbon sequestration is now perceived as a means for conservation and restoration and a way to help ameliorate greenhouse gas emissions. Of immediate concern are potential carbon losses to deforestation (90-970 Tg C y(-1)) that are greater than these ecosystems' rates of carbon storage. Large reservoirs of dissolved inorganic carbon in deep soils, pumped via subsurface pathways to adjacent waterways, are a large loss of carbon, at a potential rate up to 40% of annual primary production. Patterns of carbon allocation and rates of carbon flux in mangrove forests are nearly identical to those of other tropical forests.
Wetlands cover at least 6 % of the Earth’s surface. They play a key role in hydrological and biogeochemical cycles, harbour a large part of the world’s biodiversity, and provide multiple services to humankind. However, pressure in the form of land reclamation, intense resource exploitation, changes in hydrology, and pollution threaten wetlands on all continents. Depending on the region, 30–90 % of the world’s wetlands have already been destroyed or strongly modified in many countries with no sign of abatement. Climate change scenarios predict additional stresses on wetlands, mainly because of changes in hydrology, temperature increases, and a rise in sea level. Yet, intact wetlands play a key role as buffers in the hydrological cycle and as sinks for organic carbon, counteracting the effects of the increase in atmospheric CO2. Eight chapters comprising this volume of Aquatic Sciences analyze the current ecological situation and the use of the wetlands in major regions of the world in the context of global climate change. This final chapter provides a synthesis of the findings and recommendations for the sustainable use and protection of these important ecosystems.
Lac Bay of Bonaire is a shallow non-estuarine lagoon of about 700 hectares, separated from the open sea by a shallow coral barrier-reef. It possesses the only major concentration of seagrass beds and mangroves of the island. It is a designated Ramsar wetland of international significance, an Birdlife International IBA (Important Bird Area) and also fulfills a critical fish nursery function for the reefs of the island. The bay has consequently been designated as a protected area and is managed by Stinapa-Bonaire. The bay has been losing effective seagrass nursery habitat surface and quality as a consequence of mangrove-driven land acclamation. This in-turn is potentially being exacerbated by human-mediated eutrophication and erosion caused by agricultural and animal husbandry in the wider watershed, as well as other factors. The number of visitors to Bonaire and to Lac has been increasing dramatically over the last decades particularly from cruise ships. Yet little has been done to document and map the various types of human use that occur on and in the vicinity of the bay which might affect the ecological carrying capacity of the bay and the critical roles it plays. In this survey we do preliminary mapping and analysis of the level and distribution of human activity in and around Lac and discuss what possible threats these may entail for the environment of the bay.
Carbon fluxes from a mangrove creek with adjacent seagrass meadows and coral reefs (at 4 km from the creek) were investigated in Gazi Bay (Kenya). Analysis of the stable isotope signature of sediment carbon in the seagrass zone and data on the sediment carbon content indicate that outwelling of particulate organic matter (POM) from the mangrove forest occurs, but that deposition of this POM rapidly decreases away from the forest. No evidence for any input of mangrove POM in the seagrass zone was found at a distance of 3 km from the mangrove creek, near the reefs. The gradient in sediment deltaC-13 values in the seagrass zone was paralleled by a similar gradient of deltaC-13 values in Thalassodendron ciliatum, the dominant subtidal seagrass. This gradient probably reflects the availability of respiratory CO2 derived from mangrove POM as a carbon source for the seagrass. Analysis of C:N ratios of particulate material (< 1 mm) collected with sediment traps in the seagrass zone yielded values ranging from 8.5 to 11.2. This range is remarkably low compared to C:N ratios of plant material produced in the mangrove forest, and suggests that some of the mangrove-derived organic particles deposited in the seagrass zone have gone through a phase of intensive processing. During flood tides conspicuous decreases were found in deltaC-13 values of seston flowing over the seagrass zone, coinciding with significant increases in the carbon content of the seston. These findings point to a reversed flux of organic particles from the seagrass zone to the mangrove forest. Our data indicate that, as far as POM fluxes are concerned, the mangrove forest and adjacent seagrass meadows are tightly coupled, but that the nearby coral reefs may exist in relative isolation.
Carbon gas balance was evaluated in an anthropogenically impacted (Mtoni) and a pristine (Ras Dege) mangrove forest in Tanzania. Exchange of carbon dioxide (CO2) was measured for inundated and air-exposed sediments during day and night using in situ and laboratory incubations. In situ methane (CH4) emissions were measured in the dark during air exposure only. Emission of CO2 and CH4 from open waters (e.g. creeks) was estimated from diurnal measurements of CO2, partial pressure (pCO2) and CH4 concentrations. CO2 emission from darkened sediments devoid of biogenic structures was comparable during inundation and air exposure (28 to 115 mmol m–2 d–1) with no differences between mangrove forests. Benthic primary production was low with only occasional net uptake of CO2 by the sediments. Emissions of CH4 from air-exposed sediment were generally 3 orders of magnitude lower than for CO2. Presence of pneumatophores and crab burrows increased low tide emissions several fold. Emissions from open waters were dependent on tidal level and wind speed. Lowest emission occurred during high tide (1 to 6 mmol CO2 m–2 d–1; 10 to 80 µmol CH4 m–2 d–1) and highest during low tide (30 to 80 mmol CO2 m–2 d–1; 100 to 350 µmol CH4 m–2 d–1) when supersaturated runoff from the forest floor and porewater seepage reached the creek water. Based on global average primary production and measured gas emissions, the carbon gas balance of the 2 mangrove forests was estimated. The densely vegetated Ras Dege forest appears to be an efficient sink of greenhouse carbon gases, while extensive clear-cutting at the Mtoni forest apparently has reduced its capacity to absorb CO2, although it is seemingly still a net sink for atmospheric CO2.
Coastal wetlands can have exceptionally large carbon (C) stocks and their protection and restoration would constitute an effective mitigation strategy to climate change. Inclusion of coastal ecosystems in mitigation strategies requires quantification of carbon stocks in order to calculate emissions or sequestration through time. In this study, we quantified the ecosystem C stocks of coastal wetlands of the Sian Ka'an Biosphere Reserve (SKBR) in the Yucatan Peninsula, Mexico. We stratified the SKBR into different vegetation types (tall, medium and dwarf mangroves, and marshes), and examined relationships of environmental variables with C stocks. At nine sites within SKBR, we quantified ecosystem C stocks through measurement of above and belowground biomass, downed wood, and soil C. Additionally, we measured nitrogen (N) and phosphorus (P) from the soil and interstitial salinity. Tall mangroves had the highest C stocks (987±338 Mg ha) followed by medium mangroves (623±41 Mg ha), dwarf mangroves (381±52 Mg ha) and marshes (177±73 Mg ha). At all sites, soil C comprised the majority of the ecosystem C stocks (78-99%). Highest C stocks were measured in soils that were relatively low in salinity, high in P and low in N∶P, suggesting that P limits C sequestration and accumulation potential. In this karstic area, coastal wetlands, especially mangroves, are important C stocks. At the landscape scale, the coastal wetlands of Sian Ka'an covering ≈172,176 ha may store 43.2 to 58.0 million Mg of C.
A majority of the global net primary production of mangroves is unaccounted for by current carbon budgets.
It has been hypothesized that this ‘‘missing carbon’’ is exported as dissolved inorganic carbon (DIC) from
subsurface respiration and groundwater (or pore-water) exchange driven by tidal pumping. We tested this
hypothesis by measuring concentrations and d13C values of DIC, dissolved organic carbon (DOC), and
particulate organic carbon (POC), along with radon (222Rn, a natural submarine groundwater discharge tracer),
in a tidal creek in Moreton Bay, Australia. Concentrations and d13C values displayed consistent tidal variations,
and mirrored the trend in 222Rn in summer and winter. DIC and DOC were exported from, and POC was
imported to, the mangroves during all tidal cycles. The exported DOC had a similar d13C value in summer and
winter (, 230%). The exported d13C-DIC showed no difference between summer and winter and had a d13C
value slightly more enriched (, 222.5%) than the exported DOC. The imported POC had differing values in
summer (, 216%) and winter (, 222%), reflecting a combination of seagrass and estuarine particulate organic
matter (POM) in summer and most likely a dominance of estuarine POM in winter. A coupled 222Rn and carbon
model showed that 93–99% of the DIC and 89–92% of the DOC exports were driven by groundwater advection.
DIC export averaged 3 g C m22 d21 and was an order of magnitude higher than DOC export, and similar to
global estimates of the mangrove missing carbon (i.e., , 1.9–2.7 g C m22 d21).
The assessment of net ecosystem exchange (NEE) and respiration of ecosystem (Reco) of terrestrial ecosystems is necessary to improve our knowledge about the carbon cycle. The aims of this paper were to present reliable measurements of CO2 fluxes of a temperate bog ecosystem located in Poland using a closed dynamic chamber system and to obtain a daily dynamic course of CO2 fluxes over the 2007 vegetation season.
Measurements of CO2 fluxes were carried out at Rzecin peatland ecosystem located in northwestern Poland using the set of two chambers (dark and transparent). Reco during the experiment period ranged
2.65 to 14.76 μmolCO2·m-2·s-1. The daily run of NEE was inversed to PPFD and the values of NEE varied from 0.06 to -11.82 μmolCO2·m-2·s-1. We found differences between NEE and Reco in the wetland ecosystem with respect to term of measurements. The PPFD, air and soil temperatures explain most temporal variability of CO2 fluxes at Rzecin. But vegetation structure, its phenology and water-level depth seem also to play important roles. The chamber technique is a useful tool for determining carbon dioxide exchange between wetland surface and the atmosphere.
Mangrove forests occur along ocean coastlines throughout the tropics, and support numerous ecosystem services, including fisheries production and nutrient cycling. However, the areal extent of mangrove forests has declined by 30-50% over the past half century as a result of coastal development, aquaculture expansion and over-harvesting. Carbon emissions resulting from mangrove loss are uncertain, owing in part to a lack of broad-scale data on the amount of carbon stored in these ecosystems, particularly below ground. Here, we quantified whole-ecosystem carbon storage by measuring tree and dead wood biomass, soil carbon content, and soil depth in 25 mangrove forests across a broad area of the Indo-Pacific region--spanning 30° of latitude and 73° of longitude--where mangrove area and diversity are greatest. These data indicate that mangroves are among the most carbon-rich forests in the tropics, containing on average 1,023Mg carbon per hectare. Organic-rich soils ranged from 0.5m to more than 3m in depth and accounted for 49-98% of carbon storage in these systems. Combining our data with other published information, we estimate that mangrove deforestation generates emissions of 0.02-0.12Pg carbon per year--as much as around 10% of emissions from deforestation globally, despite accounting for just 0.7% of tropical forest area.
Mangroves, the only woody halophytes living at the confluence of land and sea, have been heavily used traditionally for food, timber, fuel and medicine, and presently occupy about 181 000 km2 of tropical and subtropical coastline. Over the past 50 years, approximately one-third of the world's mangrove forests have been lost, but most data show very variable loss rates and there is considerable margin of error in most estimates. Mangroves are a valuable ecological and economic resource, being important nursery grounds and breeding sites for birds, fish, crustaceans, shellfish, reptiles and mammals; a renewable source of wood; accumulation sites for sediment, contaminants, carbon and nutrients; and offer protection against coastal erosion. The destruction of mangroves is usually positively related to human population density. Major reasons for destruction are urban development, aquaculture, mining and overexploitation for timber, fish, crustaceans and shellfish. Over the next 25 years, unrestricted clear felling, aquaculture, and overexploitation of fisheries will be the greatest threats, with lesser problems being alteration of hydrology, pollution and global warming. Loss of biodiversity is, and will continue to be, a severe problem as even pristine mangroves are species-poor compared with other tropical ecosystems. The future is not entirely bleak. The number of rehabilitation and restoration projects is increasing worldwide with some countries showing increases in mangrove area. The intensity of coastal aquaculture appears to have levelled off in some parts of the world. Some commercial projects and economic models indicate that mangroves can be used as a sustainable resource, especially for wood. The brightest note is that the rate of population growth is projected to slow during the next 50 years, with a gradual decline thereafter to the end of the century. Mangrove forests will continue to be exploited at current rates to 2025, unless they are seen as a valuable resource to be managed on a sustainable basis. After 2025, the future of mangroves will depend on technological and ecological advances in multi-species silviculture, genetics, and forestry modelling, but the greatest hope for their future is for a reduction in human population growth.
Water-to-air carbon dioxide fluxes from tropical coastal waters are an important but understudied component of the marine carbon budget. Here, we investigate drivers of carbon dioxide partial pressure (pCO2) in a relatively pristine mangrove-seagrass embayment on a tropical island (Bali, Indonesia). Observations were performed over eight underway seasonal surveys and a fixed location time series for 55 hours. There was a large spatial variability of pCO2 across the continuum of mangrove forests, seagrass meadows and the coastal ocean. Overall, the embayment waters surrounded by mangroves released CO2 to the atmosphere with a net flux rate of 18.1 ± 5.8 mmol m-2 d -1. Seagrass beds produced an overall CO2 net
flux rate of 2.5 ± 3.4 mmol m-2 d -1, although 2 out of 8 surveys revealed a sink of CO2 in the seagrass area. The mouth of the bay where coral calcification occurs was a minor source of CO2 (0.3 ± 0.4 mmol m-2 d -1 ). The overall average CO2 flux to the atmosphere along the transect was 9.8 ± 6.0 mmol m-2 d -1, or 3.6 x 103 mol d-1 CO2 when upscaled to the entire embayment area. There were no clear seasonal patterns in contrast to better studied temperate
systems. pCO2 significantly correlated with antecedent rainfall and the natural groundwater tracer radon (222Rn) during each survey. We suggest that the CO2 source in the mangrove dominated upper bay was associated with delayed groundwater inputs, and a shifting CO2
source-sink in the lower bay was driven by the uptake of CO2 by seagrass and mixing with oceanic waters. This differs from modified landscapes where potential uptake of CO2 is weakened due to the degradation of seagrass beds, or emissions are increased due to drainage of coastal wetlands.
Seasonal variations of CO2 and CH4 fluxes were investigated in a Rhizophora mangrove forest that develops under a semi-arid climate, in New Caledonia. Fluxes were measured using closed incubation chambers connected to a CRDS analyzer. They were performed during low tide at light, in the dark, and in the dark after having removed the top 1–2 mm of soil, which may contain biofilm. CO2 and CH4 fluxes ranged from 31.34 to 187.48 mmol m−2 day−1 and from 39.36 to 428.09 μmol m−2 day−1, respectively. Both CO2 and CH4 emissions showed a strong seasonal variability with higher fluxes measured during the warm season, due to an enhanced production of these two gases within the soil. Furthermore, CO2 fluxes were higher in the dark than at light, evidencing photosynthetic processes at the soil surface and thus the role of biofilm in the regulation of greenhouse gas emissions from mangrove soils. The mean δ13C-CO2 value of the CO2 fluxes measured was −19.76 ± 1.19‰, which was depleted compared to the one emitted by root respiration (−22.32 ± 1.06‰), leaf litter decomposition (−21.43 ± 1.89‰) and organic matter degradation (−22.33 ± 1.82‰). This result confirmed the use of the CO2 produced within the soil by the biofilm developing at its surface. After removing the top 1–2 mm of soil, both CO2 and CH4 fluxes increased. Enhancement of CH4 fluxes suggests that biofilm may act as a physical barrier to the transfer of GHG from the soil to the atmosphere. However, the δ13C-CO2 became more enriched, evidencing that the biofilm was not integrally removed, and that its partial removal resulted in physical disturbance that stimulated CO2 production. Therefore, this study provides useful information to understand the global implication of mangroves in climate change mitigation.
Although mangrove forests are efficient natural carbon sinks, most of the atmospheric carbon dioxide (CO2) fixed by its vegetation is believed to be exported via tidal exchange, rather than stored in the vegetative biomass and sediment. However, the magnitude of tidal export is largely unknown because direct measurements are scarce. We deployed a novel experimental design that combined automated high-resolution measurements of hydrodynamic, hydrogeochemical and biogeochemical parameters during the dry season in a mangrove tidal creek in the Can Gio Mangrove Forest in Vietnam. The objective was to quantify the tide-controlled water, porewater, DIC and DOC exchange, and estimate the CO2 evasion throughout tidal cycles contrasted by amplitude. Data from three 25-h time series showed a clear peak of DIC, DOC, pCO2, and ²²²Rn at low tide, particularly during tidal cycles of large amplitude, which directly relate to porewater discharge. Our mass balance models revealed that the tidal creek was a net exporter of dissolved carbon to coastal waters, with an important contribution (38%) coming from DIC in porewater discharge. Porewater exchange varied from 3.1 ± 1.6 to 7.1 ± 2.4 cm day⁻¹. DIC exchange ranged from 352 ± 34 to 678 ± 79 mmolC m⁻² day⁻¹; DOC exchange, 20.6 ± 1.9 to 67.7 ± 7.9 mmol C m⁻² day⁻¹; and CO2 evasion, 69.9 ± 10.5 to 173.7 ± 26.1 mmolC m⁻² day⁻¹. These estimates were in the high range of previous carbon assessments and were explained by (i) the monitoring station being located at equal distance from the head and the mouth of the creek, which minimized carbon degradation and losses associated to transport in water; and (ii) the site being a highly productive mangrove within South East Asia.
Mangroves are known for exchanging organic and inorganic carbon with estuaries and oceans but studies that have estimated their contribution to the global budget are limited to a few mangrove ecosystems which exclude world's largest the Sundarbans. Here, we worked in the Indian Sundarbans and in the Hooghly river/estuary in May (pre-monsoon) and December (post-monsoon), 2014. Aims were, i) to quantify the riverine export of particulate organic carbon (POC) and dissolved organic and inorganic carbon (DOC, DIC)) of the Hooghly into the Bay of Bengal (BoB), ii) to estimate the C export (DOC, DIC, POC) from the Sundarbans into the BoB by using a simple mixing model, as well as iii) to revise the existing C budget constructed for the mangroves. The riverine exports of POC, DOC and DIC account for 0.07 Tg C yr− 1, 0.34 Tg C yr− 1 and 4.14 Tg C yr− 1, respectively, and were largest during the monsoon period. Results revealed that mangrove plant derived organic matter and its subsequent degradation is the primary source of DIC and DOC in the Hooghly estuary whereas POC is linked to soil erosion. Mangroves are identified as a major source of carbon (POC, DOC, DIC) transported from the Sundarbans into the BoB, with export rates of 0.58 Tg C yr− 1, 3.03 Tg C yr− 1, and 3.69 Tg C yr− 1 respectively, altogether amounting to 7.3 Tg C yr− 1. This C export from the Indian Sundarbans exceeds the ‘missing C’ of the previous budget, thus necessitating further research to finally resolve the mangrove C budget. However, these first baseline data on C exports from the world's largest deltaic mangrove improves limited global data inventory and signifies the need of acquiring more data from different mangrove settings to reduce uncertainties.
Mangrove forests are important sinks and sources of carbon especially for connections to coral reefs and seagrass beds. However, they are increasing under threat from anthropogenic influences. We investigated correlations between carbon fluxes from the sediment and water column in deforested and intact mangroves. Our findings show that deforestation has a negative effect on sediment organic carbon storage and CO2 fluxes. However, species richness and density showed a positive correlation with sediment organic carbon storage and CO2 fluxes. An increased density of saplings showed a positive relationship with dissolved inorganic and organic carbon draining the mangrove forest at high tide. This research offers insights into the importance of the key forest characteristics influencing the storage and fluxes of carbon. Alterations in mangrove carbon stocks and retention may affect connected ecosystems.
Mangroves are blue carbon ecosystems that sequester significant carbon but release CO2 , and to a lesser extent CH4, from the sediment through oxidation of organic carbon or from overlying water when flooded. Previous studies, e.g. Leopold et al. (2015), have investigated sediment organic carbon (SOC) content and CO2 flux separately, but could not provide a holistic perspective for both components of blue carbon. Based on field data from a mangrove in southeast Queensland, Australia, we used a structural equation model to elucidate (1) the biotic and abiotic drivers of surface SOC (10 cm) and sediment CO2 flux; (2) the effect of SOC on sediment CO2 flux; and (3) the covariation among the environmental drivers assessed. Sediment water content, the percentage of fine-grained sediment (< 63 μm), surface sediment chlorophyll and light condition collectively drive sediment CO2 flux, explaining 41% of their variation. Sediment water content, the percentage of fine sediment, season, landform setting, mangrove species, sediment salinity and chlorophyll collectively drive surface SOC, explaining 93% of its variance. Sediment water content and the percentage of fine sediment have a negative impact on sediment CO2 flux but a positive effect on surface SOC content, while sediment chlorophyll is a positive driver of both. Surface SOC was significantly higher in Avicennia marina (2994 ± 186 g m − 2 , mean ± SD) than in Rhizophora stylosa (2383 ± 209 g m − 2). SOC was significantly higher in winter (2771 ± 192 g m − 2) than in summer (2599 ± 211 g m − 2). SOC significantly increased from creek-side (865 ± 89 g m − 2) through mid (3298 ± 137 g m − 2) to landward (3933 ± 138 g m − 2) locations. Sediment salinity was a positive driver of SOC. Sediment CO2 flux without the influence of biogenic structures (crab burrows, aerial roots) averaged 15.4 mmol m − 2 d − 1 in A. marina stands under dark conditions, lower than the global average dark flux (61 mmol m − 2 d − 1) for mangroves.
In order to understand the processes that control organic matter preservation in tropical wetlands, we have evaluated the mineralogy, total organic carbon (TOC wt%), soluble organic matter (SOM wt%), bulk density (g/cm3), carbon stock (Mg/ha), FTIR to identify functional groups in SOM of soil in mangrove forest dominated by Rhizophora or Avicennia with different conditions (live, deteriorated and dead). Six locations along the Cuare Inlet and Morrocoy National Park were studied. Mineralogical analysis showed the presence of minerals, such as pyrite and rhodochrosite, from anoxic environments. Rhizophora mangrove soils have higher TOC compared with Avicennia, but we did not find significant differences in SOM. TOC/SOM ratios were lower for Avicennia soils. The carbon content ranges from 11.30 to 59.84 Mg/ha for the first 10 cm of soil. Regardless of stand condition, the TOC/SOM ratio was lower at a depth of 20−40 cm. The results of the TOC/SOM ratio are attributable to: (a) the association of TOC with clays and non crystalline minerals; (b) the leaching processes of soluble compounds of the OM; (c) a higher proportion of recalcitrant compounds; (d) a lower decomposition rate for recalcitrant or non recalcitrant compounds; and (e) physicochemical conditions that limit biological activity, such as high salinity, soil anoxia and hypoxia. The soils can be divided into three groups according to the presence and intensity of functional groups detected by FTIR. The functional groups identified could not be related to the sampling sites, to species composition or conditions. These differences may be due to other sources of organic matter, as well as to degree of preservation. Information of soil organic matter properties and their relationship with mangrove composition and conditions is important to understand carbon sequestration and storage potential in Venezuelan Caribbean mangrove systems.
Mangrove forests are hotspots in the global carbon cycle, yet the fate for a majority of mangrove net primary production remains unaccounted for. The relative proportions of alkalinity and dissolved CO2 [CO2*] within the dissolved inorganic carbon (DIC) exported from mangroves is unknown, and therefore the effect of mangrove DIC exports on coastal acidification remains unconstrained. Here we measured dissolved inorganic carbon parameters over complete tidal and diel cycles in six pristine mangrove tidal creeks covering a 26° latitudinal gradient in Australia, and calculated the exchange of DIC, alkalinity and [CO2*] between mangroves and the coastal ocean. We found a mean DIC export of 59 mmol m-2 d-1 across the six systems, ranging from import of 97 mmol m-2 d-1 to an export of 85 mmol m-2 d-1. If the Australian transect is representative of global mangroves, upscaling our estimates would result in global DIC exports of 3.6 ± 1.1 Tmol C yr-1, which accounts for approximately one third of the previously unaccounted for mangrove carbon sink. Alkalinity exchange ranged between an import of 1.2 mmol m-2 day-1 and an export of 117 mmol m-2 day-1 with an estimated global export of 4.2 ± 1.3 Tmol yr-1. A net import of free CO2 was estimated (-11.4 ± 14.8 mmol m-2 d-1), and was equivalent to approximately one third of the air water CO2 flux (33.1 ± 6.3 mmol m-2 d-1). Overall, the effect of DIC and alkalinity exports created a measurable localized increase in coastal ocean pH. Therefore, mangroves may partially counteract coastal acidification in adjacent tropical waters.
The exchange of nutrients, energy and carbon between soil organic matter, the soil environment, aquatic systems and the atmosphere is important for agricultural productivity, water quality and climate. Long-standing theory suggests that soil organic matter is composed of inherently stable and chemically unique compounds. Here we argue that the available evidence does not support the formation of large-molecular-size and persistent 'humic substances' in soils. Instead, soil organic matter is a continuum of progressively decomposing organic compounds. We discuss implications of this view of the nature of soil organic matter for aquatic health, soil carbon-climate interactions and land management.
This paper reports the results of carbon stored in soil and aboveground biomass
from the most important area of mangroves in Mexico with dominant vegetation
of Red mangrove (Rhizophora mangle L.), Black mangrove (Avicennia
germinans L.), white mangrove (Laguncularia racemosa Gaertn.) and button
mangrove (Conocarpus erectus L.) in three sites located in the Atasta Peninsula,
Campeche, Mexico. Samples were taken in 2009 and 2010 during the dry season
from soils with high fertility. To determine tree biomass (AGB), allometric
equations were used. Greater values of AGB were found for button mangrove
(253.18 ± 32.17 t ha-1) and lower values were found for Black mangrove (161.93
± 12.63), intermediate carbon storage were found in the other two species Red
mangrove 181.70±16.58 t ha-1), and white mangrove (206.07±19.12 t ha-1).
Carbon stored in soil at the three sites was measured in a range of 36.80 ± 10.27
to 235.77 ± 66.11 t C ha-1. The Tukey test (p
Random forests are a combination of tree predictors such that each tree depends on the values of a random vector sampled independently and with the same distribution for all trees in the forest. The generalization error for forests converges a.s. to a limit as the number of trees in the forest becomes large. The generalization error of a forest of tree classifiers depends on the strength of the individual trees in the forest and the correlation between them. Using a random selection of features to split each node yields error rates that compare favorably to Adaboost (Y. Freund & R. Schapire, Machine Learning: Proceedings of the Thirteenth International conference, ∗∗∗, 148–156), but are more robust with respect to noise. Internal estimates monitor error, strength, and correlation and these are used to show the response to increasing the number of features used in the splitting. Internal estimates are also used to measure variable importance. These ideas are also applicable to regression.
Automated in situ instrumentation captured high-resolution surface water pCO2, CH4 and 222Rn data at the creek mouth, and ~ 500m upstream in a sub-tropical mangrove ecosystem (Southern Moreton Bay, Australia, S27.78°, E153.38°) over a spring-neap-spring tidal cycle (~ 15 days) during November 2013. The partial pressure of CO2 (pCO2) ranged from 385 to 26106 µatm, CH4 from 1.8 to 889 nM, and 222Rn from 280 to 108172 dpm m-3. Average surface water pCO2, CH4 and 222Rn were 4-fold higher at the upstream station. Surface water fluxes of CO2 and CH4 ranged from 9.4 to 629.2 mmol CO2 m-2 d-1 and 13.1 to 632.9 μmol CH4 m-2 d-1 depending upon the gas transfer model used and station location. Creek pCO2, CH4 and 222Rn displayed changes over both semi-diurnal and spring-neap-spring tidal scales. Semi-diurnally, all gases had a significant inverse relationship with water depth. Over the spring-neap-spring cycle, all gases exhibited an inverse relationship with tidal amplitude, with higher values during neap tides than spring tides. Estimated fluxes, porewater observations, and the significant positive relationship between surface water pCO2 and CH4, and 222Rn suggests groundwater exchange (i.e. tidal pumping) drives pCO2 and CH4 within the mangrove creek. We hypothesize that a combination of hourly and weekly groundwater-surface water exchange processes drive surface water pCO2 and CH4 in mangrove creeks. Semi-diurnally, flushing of crab burrows leads to high pCO2 and CH4 concentrations at low tide. During the spring-neap-spring cycle, older groundwater enriched in CO2, CH4 and 222Rn seeps into the creek as tidal amplitude decreases, leading to higher concentrations at neap tides.
Mangroves are recognized to possess a variety of ecosystem services including high rates of carbon sequestration and storage. Deforestation and conversion of these ecosystems continue to be high and have been predicted to result in significant carbon emissions to the atmosphere. Yet few studies have quantified the carbon stocks or losses associated with conversion of these ecosystems. In this study we quantified the ecosystem carbon stocks of three common mangrove types of the Caribbean as well as those of abandoned shrimp ponds in areas formerly occupied by mangrove-a common land-use conversion of mangroves throughout the world. In the mangroves of the Montecristi Province in Northwest Dominican Republic we found C stocks ranged from 706 to 1131 Mg/ha. The medium-statured mangroves (3-10 m in height) had the highest C stocks while the tall (> 10 m) mangroves had the lowest ecosystem carbon storage. Carbon stocks of the low mangrove (shrub) type (< 3 m) were relatively high due to the presence of carbon-rich soils as deep as 2 m. Carbon stocks of abandoned shrimp ponds were 95 Mg/ha or approximately 11% that of the mangroves. Using a stock-change approach, the potential emissions from the conversion of mangroves to shrimp ponds ranged from 2244 to 3799 Mg CO2e/ha (CO2 equivalents). This is among the largest measured C emissions from land use in the tropics. The 6260 ha of mangroves and converted mangroves in the Montecristi Province are estimated to contain 3,841,490 Mg of C. Mangroves represented 76% of this area but currently store 97% of the carbon in this coastal wetland (3,696,722 Mg C). Converted lands store only 4% of the total ecosystem C (144,778 Mg C) while they comprised 24% of the area. By these metrics the replacement of mangroves with shrimp and salt ponds has resulted in estimated emissions from this region totaling 3.8 million Mg CO2e or approximately 21% of the total C prior to conversion. Given the high C stocks of mangroves, the high emissions from their conversion, and the other important functions and services they provide, their inclusion in climate-change mitigation strategies is warranted.
The exact size of the wetland area of South America is not known but may comprise as much as 20% of the sub-continent, with river floodplains and intermittent interfluvial wetlands as the most prominent types. A few wetland areas have been well studied, whereas little is known about others, including some that are very large. Despite the fact that most South American countries have signed the Ramsar convention, efforts to elaborate basic data have been insufficient, thereby hindering the formulation of a wetland-friendly policy allowing the sustainable management of these areas. Until now, the low population density in many wetland areas has provided a high level of protection; however, the pressure on wetland integrity is increasing, mainly as a result of land reclamation for agriculture and animal ranching, infrastructure building, pollution, mining activities, and the construction of hydroelectric power plants. The Intergovernmental Panel on Climate Change has predicted increasing temperatures, accelerated melting of the glaciers in Patagonia and the Andes, a rise in sea level of 20–60 cm, and an increase in extreme multiannual and short-term climate events (El Niño and La Niña, heavy rains and droughts, heat waves). Precipitation may decrease slightly near the Caribbean coast as well as over large parts of Brazil, Chile, and Patagonia, but increase in Colombia, Ecuador, and Peru, around the equator, and in southeastern South America. Of even greater impact may be a change in rainfall distribution, with precipitation increasing during the rainy season and decreasing during the dry season. There is no doubt that the predicted changes in global climate will strongly affect South American wetlands, mainly those with a low hydrologic buffer capacity. However, for the coming decades, wetland destruction by wetland-unfriendly development planning will by far outweigh the negative impacts of global climate change. South American governments must bear in mind that there are many benefits that wetlands bring about for the landscape and biodiversity as well as for humans. While water availability will be the key problem for the continent’s cities and agroindustries, intact wetlands can play a major role in storing water, buffering river and stream discharges, and recharging subterranean aquifers.
Mangroves are the major ecosystems of tropical and subtropical coastlines. They are considered as a sink for atmospheric CO2 because they are characterized both by high net primary production, and by low rates of organic matter decomposition. However, a recent reassessment of the global mangrove budget suggests that organic carbon sinks have been underestimated, notably CO2 efflux from sediments and creek waters, and tidal export of dissolved inorganic carbon. Our objective was to understand the influence of mangrove zonation on the magnitude of CO2 fluxes at the sediment–air interface. Transparent and opaque dynamic closed chamber systems, coupled with an infra-red gas analyzer were used to measure CO2 fluxes. In addition, the physico-chemical properties (salinity, redox potential) of pore waters were determined, as well as the carbon content and the origin of surface sediments (Chlorophyll-a and δ13C). Depending on the type of measurement (in the dark with or without biofilm, in the light with biofilm) and mangrove stand (saltflat, Avicennia sp., or Rhizophora spp.), mean surface sediment CO2 fluxes ranged between 40 ± 56 and 199 ± 95 mmol·m− 2·d− 1. We suggest that these differences mainly result both from the organic content and the redox conditions of the sediments, which are influenced by the physiological activities of the root system, and by the position and the elevation of the stand in the intertidal zone. In addition, the quality and abundance of biofilm, which also vary with the mangrove stand, also appear to strongly affect sediment CO2 fluxes as a result of chemical (metabolism) and also physical (barrier) processes.
1] Mangrove wetlands exist in the transition zone between terrestrial and marine environments and as such were historically overlooked in discussions of terrestrial and marine carbon cycling. In recent decades, mangroves have increasingly been credited with producing and burying large quantities of organic carbon (OC). The amount of available data regarding OC burial in mangrove soils has more than doubled since the last primary literature review (2003). This includes data from some of the largest, most developed mangrove forests in the world, providing an opportunity to strengthen the global estimate. First-time representation is now included for mangroves in and Thailand, along with additional data from Mexico and the United States. Our objective is to recalculate the centennial-scale burial rate of OC at both the local and global scales. Quantification of this rate enables better understanding of the current carbon sink capacity of mangroves as well as helps to quantify and/or validate the other aspects of the mangrove carbon budget such as import, export, and remineralization. Statistical analysis of the data supports use of the geometric mean as the most reliable central tendency measurement. Our estimate is that mangrove systems bury 163 (+40; À31) g OC m À2 yr À1 (95% C.I.). Globally, the 95% confidence interval for the annual burial rate is 26.1 (+6.3; À5.1) Tg OC. This equates to a burial fraction that is 42% larger than that of the most recent mangrove carbon budget (2008), and represents 10–15% of estimated annual mangrove production. This global rate supports previous conclusions that, on a centennial time scale, 8–15% of all OC burial in marine settings occurs in mangrove systems.
This report focuses on the management of natural coastal carbon sinks. The produc�on of the report has been s�mulated by an apparent lack of recogni�on • and focus on coastal marine ecosystems to comple- ment ac�vi�es already well advanced on land to ad- dress the best prac�ce management of carbon sinks.
The produc�on of this report is �mely as a number of Governments are now introducing legisla�on to tackle climate change. In the UK, for example, the Climate Change Act sets out a statutory responsibility to quan-
�fy natural carbon sink as part of the overall carbon • accoun�ng process. It is important that such quan��- ca�ons and processes work with the latest science and evidence.
To construct this report we asked leading scien�sts
for their views on the carbon management poten�al
of a number of coastal ecosystems: �dal saltmarshes, mangroves, seagrass meadows, kelp forests and coral • reefs. The resultant chapters wri�en by these scien�sts form the core of this report and are their views on how well such habitats perform a carbon management role. These ecosystems were selected because the belief from the outset was that they are good at sequestering carbon, and are located in situa�ons where manage- ment ac�ons could secure the carbon sinks. There are
of course other features of our ocean that are already • established as good carbon sinks – the key focus for this ini�al work has, however, been on those ecosystems where management interven�on can reasonably read-
ily play a role in securing and improving the future state
of the given carbon sinks. If proven this work could ex- pand the range of global op�ons for carbon manage- ment into coastal marine environments, unlocking many possibili�es for ac�on and possible �nancing of new management measures to protect the important • carbon sinks.
The key �ndings of this report are:
These key marine ecosystems are of high im- portance because of the signi�cant goods and services they already provide as well as the carbon management poten�al recog- nised in this report, thus providing new con- vergent opportuni�es to achieve many po- li�cal goals from few management ac�ons.
The carbon management poten�al of these se- lected marine ecosystems compares favourably with and, in some respects, may exceed the po- ten�al of carbon sinks on land. Coral reefs, rather than ac�ng as ‘carbon sinks’ are found to be slight ‘carbon sources’ due to their e�ect on local ocean chemistry
The table below highlights some of the key car- bon sink data documented in this report for these coastal habitats. It provides summary data on the comparison of carbon stocks and long-term accu- mula�on of carbon in the coastal marine ecosys- tems. Comparisons with informa�on on terrestrial carbon sinks are provided in the body of this report.
The chemistry of some speci�c marine sediments (for example salt marshes) sugges