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National Committee on Marine Sciences (NCMS)

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    Update of seagrass cover and species diversity in Southern Viet Nam using remote sensing data and molecular analyses
    Nguyen, Xuan-Vy; Lau, Va-Khin; Nguyen-Nhat, Nhu-Thuy; Nguyen, Trung-Hieu; Phan, Kim-Hoang; Dao, Viet-Ha; Ho-Dinh, Duan; Hayashizaki, Ken-ichi; Fortes, Miguel D.; Papenbrock, Jutta (Elsevier, 2021-05)
    Along with coral reefs and mangroves, seagrass meadows are being threatened globally Southeast Asia is considered within the area of seagrasses’ cradle of diversity. However, information on the current status of seagrass beds from Southern Viet Nam is limited due to lack of reliable data about seagrass species occurring in the Southeast Asian region. One factor is the difficulty of unambiguous species identification. For example, the leaf morphological characteristics of Halophila ovalis and closely related species are overlapping which leads to misidentifications. In this study, the latest satellite Landsat 8 OLI and SENTINEL-2B image analyses were applied to determine the distribution of seagrass beds in Southern Viet Nam. Detailed morphological and genetic marker analyses were used to determine and update the species composition. The present study together with literature reviews indicate that the total area of seagrass beds from Southern Viet Nam are 10,832.1 ha. 2562 ha (or 19.1%) of seagrass coverage has been lost. The seagrass beds at Phu Quoc Island are the largest with 7579 ha. The occurrence of Halophila major is updated for almost all off-shore islands and open-water areas.
    We are deeply indebted to all staff of the Department of Marine Botany, Center for Oceanographic Data, GIS and Remote Sensing, Institute of Oceanography (ION), Viet Nam, for their support, generously providing many valuable suggestions. We thank the VAST Key lab on Food and Environmental Safety (Central Viet Nam) for the ability to use their equipment. We would like to thank the three anonymous reviewers for their suggestions, comments, and editing. We also thank to JSPS Core-toCore Program CREPSUM.JPJSCCB20200009. This work was supported by Vietnam Academy of Science and Technology, grant code VAST04.01/20-21.
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    Estimation of the vertical phytoplankton distribution in the Philippine Sea: Influence of turbulence following passage of typhoons
    Cordero-Bailey, Kristina S.A.; Almo, Aldwin T.; David, Laura T.; Yñiguez, Aletta T. (Elsevier, 2022-11)
    The subsurface chlorophyll-a maximum (SCM) is a phenomenon that contributes significantly to the total primary production of the open ocean but it is not observable from remote sensing, thus primary production based on satellite information is highly underestimated. In a highly dynamic region such as the Philippine Sea, turbulence caused by tropical storms may exert significant impact on the SCM feature. In this study, we attempt to estimate the vertical phytoplankton profile in the Philippine Sea from remote sensing images by applying a generic quantitative approach. Generalized Additive Models (GAM) followed by Generalized Linear Models (GLMs) were used create predictive equations between response variables (Chl-a profile parameters) and predictor variables (RS parameters). GAM was able to predict integrated Chl-a biomass using photosynthetic active radiation (PAR), wind speed and wind stress, the depth of the Chl-a peak using surface Chl-a, wind speed and wind stress, and the baseline Chl-a concentration using sea surface temperature, sea surface salinity and PAR. GLM found wind stress and wind speed as significant predictors for integrated Chl-a biomass, while surface Chl-a, wind speed and wind stress were significant predictors for depth of the Chl-a peak. When the predictive equations were applied to 2020 monthly satellite images, they were seen to adequately estimate the offshore spatial distribution of the two Chl-a parameters. Increased turbulence due to high wind speed and wind stress during passage of tropical storms was seen to result in shallowing of the SCM and subsequent increase in Chl-a within the water column. These equations could be refined if long-term observational data was available. The capacity to estimate vertical distribution of primary productivity in the Philippines provides a means to better understand fisheries productivity and biogeochemical cycling in the region.
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    Ocean mapping and other marine activities of the National Mapping and Resource Information Authority (NAMRIA)
    Carandang, Efren P. (Philippine Council for Aquatic and Marine Research and Development, 2002)
    This paper describes the various marine activities being undertaken by the National Mapping and Resource Information Authority (NAMRIA) pursuant to its mandate as the central surveying, mapping and resource information agency of the government. NAMRIA gathers marine data through periodic hydrographic and oceanographic surveys and remote sensing techniques, and publishes the results in the form of nautical charts, bathymetric maps and other thematic maps. It also creates marine geographic information systems and databases. As steward of the National Oceanographic Data Center (NODC), the agency participates in international oceanographic data exchange programs, and also serves the marine data and information needs of the local marine science community. NAMRIA's data collection capability got a big boost with the acquisition this year of two multi-disciplinary survey vessels with state-of-the-art systems. With these vessels as platforms, NAMRIA will embark on the comprehensive charting of the Exclusive Economic Zone, and collaborate with the different marine science agencies in the conduct of multi-disciplinary oceanographic cruises.
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    Ground deformation analysis caused by post-2013 earthquake in Bohol, Philippines
    Bauzon, Ma. Divina Angela I.; Reyes, Rosalie B.; Blanco, Ariel C.; Siringan, Fernando P. (Springer Science and Business Media LLC, 2022-08-16)
    After the 2013 Mw 7.2 earthquake that occurred in Bohol, the shoreline specifically in Loon and Maribojoc was observed to shift seaward due to ground uplift. This study analyzes the post-earthquake shoreline movement, specifically a 12 km coastal strip in Loon and Maribojoc, and ground deformation of the West Bohol area through Sentinel-1 image processing techniques. From October 2014 to April 2018, the DSAS linear regression shoreline rates were − 4.36 m/yr in Loon and − 1.69 m/yr in Maribojoc, indicative of a landward movement of 91.4% and 88.8% of shoreline transects in Loon and Maribojoc, respectively. PSInSAR revealed varying rates of VLM in the study area from October 2014 to December 2018 such that Loon and Maribojoc exhibit a subsidence rate of − 2 to − 8 mm/yr. The correlation between the shoreline retreat and the land subsidence in the study area is 87%, indicating a possible elastic rebound after the earthquake. The portion of Tagbilaran City on its northern side exhibits land subsidence of − 2 to − 6 mm/yr while its southern side exhibits land uplift of 0–2 mm/yr. The relative sea level fall from TGSL measurements indicates an uplift in the location of the tide gauge in Tagbilaran City.