National Committee on Marine Sciences (NCMS)
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- Dissolved and particulate carbon export from a tropical mangrove‐dominated riverine systemRay, Raghab; Miyajima, Toshihiro; Watanabe, Atsushi; Yoshikai, Masaya; Ferrera, Charissa M.; Orizar, Iris; Nakamura, Takashi; San Diego‐McGlone, Maria Lourdes; Herrera, Eugene C.; Nadaoka, Kazuo (Wiley, 2021-09-24)Despite being a major component in the mangrove carbon (blue carbon) budget, “outwelling” flux (or export to the sea) has gained little attention relative to other biogeochemical fluxes and reservoir carbon stock estimations. This study aims to estimate lateral exchange fluxes of dissolved and particulate organic carbon (DOC, POC) and dissolved inorganic carbon (DIC) from the watershed through a microtidal mangrove-dominated estuary to the coastal sea in Panay Island, Philippines. Along the estuarine transect, consistent addition of DOC, DIC, and POC at higher salinities were attributed to mangrove organic matter input. Upstream groundwater input (carbonate weathering) and downstream mangrove organic matter decomposition (possibly sulfate reduction) were the main controls on DIC. DOC corresponded to relatively pure mangrove sources in creek water, while POC was a mixture of detrital and algal organic matter. The mangrove system acted as net exporter of carbon to the sea in both dry and wet seasons. From short-term observations, outwelling fluxes of mangrove-derived DOC, DIC, and POC contributed 27–53%, 8–31%, and 42%, respectively, to their estuarine outflow. Unlike other studies, such low percentage for DIC might result from other external nonmangrove input (e.g., watershed carbonate weathering). Overall estuarine carbon flux was dominated by DIC (90–95%) with only minor contribution from DOC. The approach utilized in this study to estimate lateral carbon flux specific to a small mangrove setting can be useful in delineating blue carbon budgets that avoid geographical and methodological biases.We are grateful to the Japan International Cooperation Agency (JICA) and Japan Science and Technology Agency (JST) through the Science and Technology Research Partnership for Sustainable Development Program (SATREPS) for financially supporting the Project “Comprehensive Assessment and Conservation of Blue Carbon Ecosystems and their Services in the Coral Triangle (BlueCARES).” We are indebted to Dr Gerd Gleixner and Steffen Ruehlow (MPI-Jena, Germany) for providing support in δ13DOC analyses, and Dr Naoko Morimoto for POM analyses. We sincerely thank Dr Kenji Ono for sharing fine root production data. We are thankful to Dr Ariel Blanco (Department of Geodetic Engineering, UP Diliman) for providing delineation of mangrove area and Dr. Enrico C. Paringit, program leader of Phil-LiDAR 1, for providing the LiDAR products for map preparation. We thank Jeffrey Munar, Jesus Abad, John Michael Aguilar, Dominic Bautista, Bryan C. Hernandez and Mr Tsuyoshi Kanda for their assistance during field surveys. We are grateful for the overall support given by the University of the Philippines, Diliman and Aklan State University to the project. Finally, we thank the Journal Editor, Associate Editor, and three reviewers for their valuable comments and corrections on the manuscript.
- Relationship between sediment conditions and mangrove Rhizophora apiculata seedling growth and nutrient statusDuarte, C. M.; Geertz-Hansen, O.; Thampanya, U.; Terrados, J.; Fortes, M. D.; Kamp-Nielsen, L.; Borum, J.; Boromthanarath, S. (Inter-Research Science Center, 1998)The growth rate and nutritional status of Rhizophora apiculata seedlings were analyzed across mangrove stands with different sediment composition in The Philippines and Southern Thailand. Plant growth differed 10-fold and the production of new leaves, roots and branches varied between 50- and 100-fold across sites. Most (>60%) of the variance in mangrove growth rate across systems could be accounted for by differences in the nutrient concentration of the leaves, which was in turn related to the interstitial nutrient concentration and the silt plus clay content of the sediments. Nutrient-poor coarse sediments were characteristic of mangroves located in the mouths of rivers draining small watersheds, while sediments at the mouths of large rivers had high silt, clay, and nutrient contents, thus allowing the development of nutrient-sufficient, fast-growing R. apiculata seedlings. The growth of R. apiculata seedlings increased significantly when the plants grew adjacent to rivers draining areas >10 km2. The results provide evidence that growth of R. apiculata seedlings at the edge of the progressing mangrove forests is often nutrient limited, and that the extent of nutrient limitation depends on the delivery of silt and nutrients from the rivers. The coastal zones adjacent to small (<10 km2) drainage areas seem unsuitable to support adequate growth of R. apiculata seedlings, and afforestation programmes should, therefore, target mud flats adjacent to large rivers instead.
- Total polyphenol content of tropical marine and coastal flora: Potentials for food and nutraceutical applicationsNarvarte, Bienson Ceasar V.; Genovia, Tom Gerald T.; Hinaloc, Lourie Ann R.; Gonzaga, Shienna Mae C.; Tabonda-Nabor, April Mae; Palecpec, Flora Maye R.; Dayao, Helen M.; Roleda, Michael Y. (Springer, 2023-07-08)The marine environment is abundant in natural products that are beneficial to humans. Among these compounds are the polyphenols produced by marine flora as secondary metabolites and used as a defense against stressful environmental conditions. Accordingly, recent pharmacological and biomedical studies showed that polyphenols from marine and coastal floras have several important bioactivities including antioxidant property. In this study, we measured the total polyphenol content (TPC) of 75 species of marine-associated flora. The TPC of their methanolic extracts was measured spectrophotometrically using the Folin-Ciocalteu assay and was expressed both as mg phloroglucinol equivalent per g of dry weight (mg PGE g−1 DW) and as mg gallic acid equivalent per g dry weight (mg GAE g−1 DW). The TPC values are higher when expressed in terms of GAE compared to PGE. Also, the mean TPC of tracheopytes (229 ± 43.0 mg PGE g−1 DW) was higher compared to the mean TPC of macroalgae (69.4 ± 9.59 mg PGE g−1 DW). For macroalgae, ochrophytes (97.9 ± 22.7 mg PGE g−1 DW) had the highest mean TPC followed by chlorophytes (80.0 ± 20.5 mg PGE g−1 DW) and rhodophytes (49.5 ± 8.60 mg PGE g−1 DW). Moreover, our study also showed that TPC varied between young and mature tissues, among different color morphotypes and different parts of the plants. Although the concentrations of total polyphenols varied among species, ages, strains and parts of the plant, our study showed that marine and coastal floras are rich sources of polyphenols that could be further examined for their biological activities and other applications in food industry.
- Sedimentary blue carbon dynamics based on chronosequential observations in a tropical restored mangrove forestRay, Raghab; Suwa, Rempei; Miyajima, Toshihiro; Munar, Jeffrey; Yoshikai, Masaya; San Diego-McGlone, Maria Lourdes; Nadaoka, Kazuo (Copernicus GmbH, 2023-03-03)Among the many ecosystem services provided by mangroves, the sequestration of large amounts of organic carbon (OC) in marine ecosystems (also known as “blue carbon”) has given these unique ecological environments enormous global attention. While there are many studies on the blue carbon potential of intact mangroves (i.e., naturally growing), there have been very few studies on restored mangroves (i.e., planted). This study aims to address this knowledge gap by examining the sediment development process during the early colonization (rehabilitation) of mangroves in an OC-poor estuary in Panay Island, Philippines. Based on source apportionment of multiple end-members in the sedimentary organic matter, the contribution of mangrove plant material was higher at the older sites compared to the younger sites or bare sediments where there is a higher contribution of riverine input. A clear increasing gradient according to mangrove development was observed for bulk OC (0.06–3.4 µ mol g−1, porewater OC (292–2150 µmol L−1, sedimentary OC stocks (3.13–77.4 Mg C ha−1), and OC loading per surface area (7–223 µmol m−2). The estimated carbon accumulation rates (6–33 mol m−2 yr−1) based on chronosequence are within the global ranges and show an increasing pattern with the age of mangroves. Hence, the sediments of relatively young mangrove forests appear to be a significant potential C sink, and short-term chronosequence-based observations can efficiently define the importance of mangrove restoration programs as a potential carbon sequestration pathway.We are grateful to the Japan International Cooperation Agency (JICA) and the Japan Science and Technology Agency (JST) through the Science and Technology Research Partnership for Sustainable Development (SATREPS) program for financially supporting the project Comprehensive Assessment and Conservation of Blue Carbon Ecosystems and their Services in the Coral Triangle (Blue CARES). We thank Jesus Abad, John Michael Aguilar, Dominic Bautista, Bryan C. Hernandez, and Tsuyoshi Kanda for their assistance during field surveys. We are grateful for the overall support given to the project by the University of the Philippines, Diliman, and Aklan State University. We are thankful to our Blue CARES colleague Charissa Ferrera for the support in language edits. Finally, authors sincerely thank AE (Jack Middelburg) and the reviewers for their constructive comments that have greatly improved the revised version of the manuscript.