National Committee on Marine Sciences (NCMS)
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- Clay mineral nanostructures regulate sequestration of organic carbon in typical fluvial sedimentsSong, Hongzhe; Liu, Zhifei; Lin, Baozhi; Zhao, Yulong; Siringan, Fernando P.; You, Chen-Feng (Elsevier, 2024-02-15)The association between clay minerals and organic carbon is pivotal for understanding transport, burial, and preservation processes of sedimentary organic carbon. However, fine-scale microscopic studies are still limited in assessing the effect of diverse clay mineral structures and properties on organic carbon sequestration. In this study, we employed X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy coupled with energy dispersive spectroscopy and electron energy loss spectroscopy analyses to investigate the nanoscale interaction between clay minerals and organic carbon of two typical fluvial sediment samples with contrasting clay mineral compositions and organic carbon origins. Sample from Taiwan shows abundant illite and chlorite with petrogenic organic carbon, while sample from Luzon has significant smectite with pedogenic organic carbon. We observed that the nanostructure of the clay minerals controls the distribution of organic carbon. In the Luzon sample, the organic carbon is tightly associated with smectite, occupying expandable interlayer spaces. In the Taiwan sample, however, the organic carbon is primarily confined on the surface and edge of illite. These findings offer valuable insights into the selective association of organic carbon with clay minerals and underscore the role of clay mineral nanolayer structures in governing the occurrence and preservation of organic carbon in sediments. A comprehensive understanding of these interactions is crucial for accurate assessments of carbon cycling and sequestration in the natural environment.We sincerely thank Shunai Che and Lu Han for their help in TEM experiments and data processing. We thank Editor Dr. Andrew Hursthouse for handling the manuscript and two anonymous reviewers for their constructive comments on the early version of this paper. This work was supported by the National Natural Science Foundation of China (42130407, 42188102, 42306066) and the Interdisciplinary Project of Tongji University (ZD-22-202102).
- Submerged reef features in Apo and Tubbataha Reefs, Philippines, revealed paleo sea-level history during the last deglaciationMunar, Jeffrey C.; Aurelio, Mario A.; Dumalagan, Edwin E.; Tinacba, Erin Joy C.; Doctor, Ma. Angelique A.; Siringan, Fernando P. (Springer, 2024-02-27)The morphology of coral reefs provides an effective benchmark of past sea levels because of their limited vertical range of formation and good geologic preservation. In this study, we analyze the seafloor morphology around two atolls in the Philippines: Tubbataha Reef, in Palawan, and Apo Reef, in Occidental Mindoro. High-resolution multibeam bathymetry to a depth of 200 m reveals seafloor features including reef ridges and staircase-like terraces and scarps. Depth profiles across the reefs show terraces formed within six and seven depth ranges in Tubbataha Reef and in Apo Reef, respectively. These were further observed through a remotely operated vehicle. The terraces and scarps are interpreted as backstepping reefs that were drowned during an overall rise in sea level from the Last Glacial Maximum (LGM). Terraces are used as indicators of paleo sea level and the separation between terraces as the magnitude of sea-level rises coeval with meltwater pulse events during the last deglaciation. The pattern for both Apo and Tubbataha reefs indicates subsidence, consistent with the absence of Holocene emergent features and their atoll morphologies. Subsidence of up to 17 m since the LGM in Apo Reef is mainly attributed to the downbowing of the crust toward Manila Trench. In Tubbataha Reef, subsidence of up to 14 m is attributed to the continuous cooling of the volcanic crust underlying the atoll. These can be used to fill gaps in the tectonic history of the study sites from the last deglaciation.This study was funded by the Department of Science and Technology–Philippine Council for Agriculture, Aquatic and Natural Resources Research Development (DOST-PCARRD) Geophysical Coral Mapping Project and Acquisition of Detailed Bathymetry for Coastal Erosion Management Project both under F. P. Siringan, and National Assessment of Coral Reef Environment (NACRE) Project under Hazel Arceo. We would like to mention, in particular, Dominic Jone Cabactulan, Timothy Quimpo, Ronald Olavides, Mary Ann Calleja, Patrick Cabaitan, and Cesar Villanoy who were members of the project team. We thank the Tubbataha Management Office, Sablayan Local Government Unit, and Department of Environment and Natural Resources for the work permits and logistical help during the surveys.
- Short-term exposure to independent and combined acidification and warming elicits differential responses from two tropical seagrass-associated invertebrate grazersBaure, Jerwin G.; Roleda, Michael Y.; Juinio-Meñez, Marie Antonette (Springer, 2023-08-10)Ocean acidification and warming could affect animal physiology, key trophic interactions and ecosystem functioning in the long term. This study investigates the effects of four pH−temperature combination treatments simulating ocean acidification (OA), ocean warming (OW) and combined OA and OW conditions (FUTURE) relative to ambient present-day conditions (PRESENT) on the grazing of the juveniles of two seagrass-associated invertebrates namely the sea cucumber Stichopus cf. horrens and topshell Trochus maculatus over a 5-day exposure period. Diel and feeding activity of both species increased under OW and FUTURE to some extent, while the nighttime activity of Trochus but not Stichopus decreased under OA relative to PRESENT during the first 2 days. Fecal production of Stichopus did not differ among treatments, while the lowest fecal production of Trochus was observed under OA during the first 24 h of grazing. These responses suggest that Trochus may be initially more sensitive to OA compared with Stichopus. Interestingly, fecal production of Trochus in FUTURE was significantly higher than OA, suggesting that warming may ameliorate the negative effect of acidification. Diel activity, feeding and fecal production after 5 days did not differ among treatments for both species, suggesting acclimation to the acute changes in temperature and pH after a few days, although Stichopus acclimated rapidly than Trochus. The ability of the two juvenile invertebrate grazers to rapidly acclimate to increased temperature and lowered pH conditions after short-term exposure may favor their survival under projected changes in ocean conditions.This work was supported by the Department of Science and Technology–Philippine Council for Agriculture, Aquatic, and Natural Resources Research and Development under Grant QMSR-MRRD-MEC-295-1449. The authors would like to thank Dr. Ian Enochs for his invaluable help in improving this paper. We also thank Tirso Catbagan, Garry Bucol, Rona Soy and Tomilyn Jan Garpa for their assistance during the conduct of this study. We would also like to thank the Marine Biogeochemistry Laboratory of the UP Marine Science Institute for their assistance in analyzing our water samples as well as the DNA Barcoding Laboratory of the UP Institute of Biology for the species identification of our animals.
- Reproductive consequences of thermal stress-induced bleaching in the giant clam Tridacna croceaSayco, Sherry Lyn G.; Alabort Pomares, Ana; Cabaitan, Patrick C.; Kurihara, Haruko (Elsevier, 2024-01)Reproduction is a fundamental process necessary for maintaining a population. However, reproductive processes are sensitive to thermal stress which can cause bleaching in reef organisms such as corals and giant clams. Here we examined the phototrophic and physiological performances, particularly the reproductive processes, in Tridacna crocea during bleaching and recovery periods. Giant clam individuals were induced to bleach at heated treatment (32-33 °C) for 16 days and allowed to recover at 28-29 °C for 35 days. The control giant clams were kept at 28-29 °C. Heated giant clams showed lower phototrophic performances (Fv/Fm and photosynthesis), but their respiration and survival were similar to control giant clams. The gonadosomatic index (GSI) was lower, and the proportion of regressive eggs (i.e., eggs that are no longer viable) was higher in heated than in control giant clams. However, heated giant clams were able to maintain their egg size. In addition, T. crocea showed recovery of phototrophic potential and color of mantle but not of their reproductive output after a month of recovery. Our results indicate that bleaching reduces the reproductive output in giant clams by disrupting their gametogenesis, such as through egg resorption, but giant clams showed potential reproductive strategy, through maintenance of their egg size, to ensure the quality of their offspring. Furthermore, one month of recovery is not sufficient to restore the normal reproductive processes in T. crocea, which may delay their population recovery after a bleaching disturbance.
- Contrasting reproductive strategies between stress-tolerant and competitive coral taxaBonilla, K. G.; Guest, J. R.; Baria-Rodriguez, M. V. (Springer, 2023-04-19)Reproductive traits such as fecundity (i.e., the number of gametes produced) and the size and age of coral colonies at reproductive onset can vary in predictable ways among life history strategies. However, most studies on the onset of reproductive maturity in corals only report the presence or absence of oocytes with little known about variation in fecundity across size and age classes. This study aimed to determine the colony size and fecundity at the onset of reproductive maturity across size classes of two scleractinian corals with contrasting life history strategies, Acropora millepora (competitive) and Favites colemani (stress-tolerant). Colonies at a site in northwestern Philippines were sampled to determine the smallest colony size class with mature oocytes and to estimate fecundity across size classes. Histological slides were also prepared to verify the presence of mature gametes. Colonies were able to produce mature oocytes when they had attained colony diameters of 4.7 cm for A. millepora and 1.5 cm for F. colemani. A. millepora had lower fecundity, but larger oocytes compared to F. colemani. Although small colonies can contribute to the larval pool, the proportion of mature colonies increased for larger size classes, suggesting that larger colonies make a disproportionately greater contribution to population reproductive output. These findings contribute to our understanding of coral population dynamics, particularly in parameterizing population and demographic models for different coral life histories.We are grateful to Christine Baran, Jue Alef Lalas, Jerry Arboleda, Gabriel de Guzman, the students and research assistants of Community and Ecology and Interactions of Marine Bionts and Benthic Ecosystems Laboratories for their valuable assistance during field and laboratory works, Darryl Valino for the site map, and Liam Lachs for the assistance on the statistical analyses. This research was supported by the University of the Philippines Marine Science Institute’s In-house project, Department of Science and Technology – ASTHRDP Thesis Grant, and University of the Philippines – Office of the Vice President for Academic Affairs’ Balik Ph.D. project (OVPAA-BPhD-2018-02).
- Characteristics of marine heatwaves in the PhilippinesEdullantes, Brisneve; Concolis, Brenna Mei M.; Quilestino-Olario, Raven; Atup, Dale Patrick D.; Cortes, Aiza; Yñiguez, Aletta T. (Elsevier, 2023-09)Marine Heatwaves (MHWs) are prolonged, discrete, and anomalously warm events, which have recently gained global attention due to their far-reaching effects and reported impacts. Although intensive studies have been carried out at global and regional scales, these events remained understudied in the Philippines – a country with high marine biodiversity. The Philippines is highly vulnerable to the impacts of these extreme events as it lies in the western boundary of the Pacific that is considered as a hotspot for MHWs. The present study used multi-year climatic sea surface temperature (SST) record to detect MHWs in the Philippines. The detected events were then characterized using the standardized metrics. Linear trend analysis was conducted to determine the magnitude and direction of the change of the MHW metrics over time. Decadal trend revealed that MHWs in the Philippines significantly increased from seven MHWs in the 1980s to 37 MHWs in the last decade. Moreover, increased duration was remarkable in 2020 with 276 MHW days. MHW frequency and duration were increasing at a rate almost twice as its neighboring waters. Intensities did not significantly increase with time, but the highest SST anomaly is associated with El Niño Southern Oscillation. Furthermore, the eastern and western region of the Philippines is vulnerable to MHWs, but hotspots are mostly confined in the West Philippine Sea and western tropical Pacific. An in-depth investigation of the drivers of MHWs is recommended to understand the physical mechanisms of the development of these extreme thermal events in the Philippine seas. The findings have significant implications for coastal marine resource management, highlighting the need for adaptive management strategies and increased monitoring and research efforts to mitigate the impacts of MHWs on marine ecosystems and local economies in the Philippines.
- Fish and benthic communities in an offshore and well-managed coral reef after bleaching disturbance in the PhilippinesQuimpo, Timothy Joseph R.; Requilme, Jeremiah Noelle; Gomez, Elizabeth; Sayco, Sherry Lyn; Dumalagan, Edwin E.; Siringan, Fernando P.; Conaco, Cecilia; Cabaitan, Patrick C. (Springer, 2023-08-29)Climate change is perhaps the greatest threat to coral reefs worldwide. However, there is spatial variation in the extent and severity of this disturbance, with offshore and well-managed reefs presumed to be less vulnerable to anthropogenic disturbance. Here, fish and benthic communities at the offshore and well-managed reefs of Apo Reef Natural Park, Philippines, were examined during a bleaching disturbance in 2016 and reassessed 2 (2018) and 3 years (2019) after using scuba surveys. Results showed that benthic communities varied more strongly with year attributed to changes in the benthic cover of coral. These changes were influenced by site, with some sites experiencing coral loss of 41–48%, while other sites exhibited minimal changes. Site differences in coral loss may be associated with coral cover, with sites that had high coral cover prior to bleaching incurring larger loss of coral cover. Fish communities varied more with sites and was associated with differences in the predominant benthos. The stability of fish communities with year despite coral loss may be attributed to the minimal loss of coral cover at some sites. For sites that experienced high losses of coral cover, the presence of alternative and deeper habitats may have provided shelter and food for more mobile fishes maintaining taxonomic composition within sites. This study shows that bleaching disturbance circumvents effective management, but impacts are variable even at small (≤ 3 km) spatial scales. Benthic community composition and presence of alternative habitats potentially alleviate the negative impacts of bleaching on reef fish diversity and abundance.We are grateful to the laboratory assistants F Castrence, R de Guzman, B Gabuay, R Valenzuela and K Adolfo for their assistance in the fieldwork. We thank the comments and criticisms of two anonymous reviewers that greatly improved the content of this manuscript.
- Decadal stability in coral cover could mask hidden changes on reefs in the East Asian SeasChan, Y. K. S.; Affendi, Y. A.; Ang, P. O.; Baria-Rodriguez, M. V.; Chen, C. A.; Chui, A. P. Y.; Glue, M.; Huang, H.; Kuo, C-Y.; Kim, S. W.; Lam, V. Y. Y.; Lane, D. J. W.; Lian, J. S.; Lin, S. M. N. N.; Lunn, Z.; Nañola, C. L.; Nguyen, V. L.; Park, H. S.; Sutthacheep, M.; Vo, S. T.; Vibol, O.; Waheed, Z.; Yamano, H.; Yeemin, T.; Yong, E.; Kimura, T.; Tun, K.; Chou, L. M.; Huang, D. (Springer, 2023-06-10)Coral reefs in the Central Indo-Pacific region comprise some of the most diverse and yet threatened marine habitats. While reef monitoring has grown throughout the region in recent years, studies of coral reef benthic cover remain limited in spatial and temporal scales. Here, we analysed 24,365 reef surveys performed over 37 years at 1972 sites throughout East Asia by the Global Coral Reef Monitoring Network using Bayesian approaches. Our results show that overall coral cover at surveyed reefs has not declined as suggested in previous studies and compared to reef regions like the Caribbean. Concurrently, macroalgal cover has not increased, with no indications of phase shifts from coral to macroalgal dominance on reefs. Yet, models incorporating socio-economic and environmental variables reveal negative associations of coral cover with coastal urbanisation and sea surface temperature. The diversity of reef assemblages may have mitigated cover declines thus far, but climate change could threaten reef resilience. We recommend prioritisation of regionally coordinated, locally collaborative long-term studies for better contextualisation of monitoring data and analyses, which are essential for achieving reef conservation goals.
- A multi-framework analysis of stakeholders’ perceptions in developing a localized blue carbon ecosystems strategy in Eastern Samar, PhilippinesQuevedo, Jay Mar D.; Ferrera, Charissa M.; Faylona, Marie Grace Pamela G.; Kohsaka, Ryo (Springer Science and Business Media LLC, 2024-01-25)Blue carbon ecosystems (BCEs) are vital for global climate change mitigation and offer diverse local ecosystem co-benefits. Despite existing literatures on integrating national and international BCE agendas at the local level, the development and implementation of localized BCE strategies often lag behind. To provide insights on this knowledge gap, we present a case study conducted in Eastern Samar, Philippines. Employing a multi-framework analysis- encompassing DPSIR (drivers, pressures, state, impact, responses), SOAR (strengths, opportunities, aspirations, results), and PESTLE (political, economic, social, technological, legal, environmental) frameworks, stakeholder perceptions collected from focus group discussions highlight issues and challenges in developing and implementing a BCE strategy. Findings reveal that the aftermath of Typhoon Haiyan in 2013 in the study sites stimulated conservation efforts and raised awareness, but governance structures and policy enforcement influence the success and longevity of management and conservation efforts. Through the integration of multiple frameworks, this study outlined a potential localized BCE strategy, emphasizing both internal priorities such as stakeholder engagement and alternative livelihoods and external priorities related to policy and technological supports. While developed based on a specific case study in the Philippines, the proposed strategy is presented in a general manner, enabling its potential replication in other provinces in the Philippines or in countries with similar geographic settings.
- Co-occurrence of a marine heatwave and a reported tomato jellyfish (Crambione mastigophora Maas, 1903) bloom in March 2020 at El Nido, Palawan, PhilippinesQuilestino-Olario, Raven; Concolis, Brenna Mei M.; Atup, Dale Patrick D.; Cortes, Aiza; Yñiguez, Aletta T.; Edullantes, Brisneve (The Plankton Society of Japan/The Japanese Association of Benthology, 2023-05-31)Globally, observations on marine species during marine heatwaves (MHWs) help outline the scope of the MHW’s possible biological effects. In line with this effort, this paper presents a 2020 MHW that coincided with a reported ‘tomato jellyfish’ (Crambione mastigophora Maas, 1903) bloom on 23 March 2020 in the Corong-Corong Bay of Palawan, Philippines. Detecting a moderate MHW from 21 March to 04 April 2020, the analysis of sea surface temperatures revealed that most areas surrounding the bloom site attained their peak positive anomalies on the same day as the reported bloom. Certain physical mechanisms present in the first quarter of 2020 may have played a role in the occurrence of both events: the presence of cyclonic eddies and parallel monsoonal winds alongshore can induce upwelling which promotes biological productivity in surface waters, while the observed weakening of winds have been associated with anomalous warming of the sea surface. Further studies are still highly recommended to determine the exact causes of the jellyfish bloom and what conditions make it more likely to happen during MHWs. However, if the C. mastigophora is hypothetically able to continually bloom amidst warming temperatures, the increasing trend of MHW frequency and intensity in the West Philippine Sea (where the reported bloom site is situated) may consequently yield more future co-occurrences. This paper aims to hopefully contribute to the existing knowledge of possible biological impacts associated with extreme marine events, especially in the Philippine context where both jellyfish blooms and MHWs are understudied.The authors would like to express sincere gratitude to the anonymous reviewers whose comments and suggestions helped improve and clarify this manuscript. The authors would also like to thank Mr. Alimar Amor for his permission on the still photos in Figs 1c and 1d from his recorded jellyfish bloom video on 23 March 2020. This paper is also made through the funding of DOST̶ Philippine Council for Industry, Energy, and Emerging Technology Research and Development under the Survey of Heatwaves in the Philippine Seas project (DOST Project No. 9615).