Challenge 06: Increase community resilience to ocean hazards

Permanent URI for this collectionhttps://repository.unesco.gov.ph/handle/123456789/25

Ocean Decade

Challenge 06:
Increase community resilience to ocean hazards

Enhance multi-hazard early warning services for all geophysical, ecological, biological, weather, climate and anthropogenic related ocean and coastal hazards, and mainstream community preparedness and resilience.

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A synthesis and review of historical eruptions at Taal Volcano, Southern Luzon, Philippines
Delos Reyes, Perla J.; Bornas, Ma. Antonia V.; Dominey-Howes, Dale; Pidlaoan, Abigail C.; Magill, Christina R.; Solidum, Renato Jr. U. (Elsevier BV, 2018-02)
The Philippines is an area of persistent volcanism, being located in one of the most tectonically active regions in the world. Taal Volcano in Southern Luzon is the second most frequently erupting volcano of the 24 active volcanoes in the Philippines. A comprehensive and critical review of published and unpublished references describing the 33 known historical eruptions of Taal may provide answers to knowledge gaps on past eruptive behavior, processes, and products that could be utilized for hazard and risk assessment of future eruptions. Data on the prehistoric eruptions and evolution of Taal Caldera and subsequent deposits are limited. Only four caldera-forming events were identified based on four mapped ignimbrite deposits. From oldest to youngest, these are the silicic Alitagtag (ALI) and Caloocan (CAL) Pumice Flow deposits, the dacitic Sambong Ignimbrite (SAM), and the basaltic-andesitic Taal Scoria Flow, renamed Scoria Pyroclastic Flow (SFL). Except for SFL with 14C dating yielding 5380 ± 70 to 6830 ± 80 ky, there are no age constraints or estimates of extent for the three older deposits. A comprehensive review of the historical eruptions of Taal Volcano is the central element of this paper and includes all eruptions from AD1572 (the first known historic event) to AD1977. Eruption styles and the interplay between processes and products for each eruption are reinterpreted based on the narrative descriptions from all available accounts. A change of classification of eruption styles and eruptive products is undertaken for some events. At least nine reported eruptions were deemed uncertain including the AD1605-AD1611 event (more likely seismic swarms), the AD1634, AD1635, and AD1645 (may simply be solfataric or hydrothermal activity) events, and the AD1790, AD1825, AD1842, AD1873 and AD1903 events that were listed in recent published and unpublished documents but do not provide any details to describe and confirm the eruptions except for listing a default VEI of 2. Pyroclastic density currents brought devastating impacts to the communities around Taal during the AD1749, AD1754, AD1911 and AD1965 eruptions and remain the biggest threat in the case of renewed volcanic activity. Significant implications for aviation are implied by the narrative of tephra fall dispersal towards Manila, the central gateway of international aviation operation in the Philippines, during the AD1754 eruptions. The dispersal of tephra in the event of an explosive eruption at Taal towards Metro Manila would have catastrophic effects to transport, utilities and business activity, potentially generating enormous economic losses. Hazards from earthquake events associated with future volcanic activity may also have localized impacts. Occurrences of liquefaction phenomena as a consequence of severe ground shaking are interpreted during the AD1749, AD1754, and AD1911 eruptions. More work needs to be done to develop a comprehensive understanding of the hazards and risks associated with an explosive eruption at Taal Volcano, especially related to the older Quaternary caldera-forming eruptions that produced large-volume pyroclastic deposits that are extensively distributed and exposed. We acknowledge that there may be additional prehistoric eruptions where the eruptive products have not been preserved, recognized or reported. Events that cannot be verified or do not have sufficient details to confirm the eruption, have been downgraded to “uncertain”. Eruptions that are confirmed with identified dispersal and emplacement of tephra fall and other eruptive deposits, as interpreted from narrated records, could provide crucial information that may be utilized in hazard assessment.
Asterocladon ednae sp. nov. (Asterocladales, Phaeophyceae) from the Philippines
Sasagawa, Eriko; Santiañez, Wilfred John E.; Kogame, Kazuhiro (Wiley, 2022-06-21)
Members of the brown algal order Asterocladales are characterized by stellate arrangement of its chloroplasts, in which a stellate configuration has a protruding central pyrenoid complex. The order is represented by the genus Asterocladon, which consists of only three species so far. Similar to other small and filamentous seaweeds, studies on Asterocladon remain scant and their diversity poorly understood. To fill this gap, we conducted molecular-assisted taxonomic studies on Asterocladon based on seven culture isolates collected from Okinawa Prefecture, Japan and Cebu, the Philippines. One culture isolate from the Philippines was revealed to be a new species of Asterocladon based on morpho-anatomical and molecular analyses using rbcL and psaA genes and is described here as Asterocladon ednae. The other isolates were attributed to A. rhodochortonoides. A. ednae was most closely related to A. rhodochortonoides in morphology and molecular phylogeny but was distinguished from the latter by its elongately ellipsoid plurilocular sporangia. This is the first report of the genus and species A. ednae in the Philippines, further increasing the diversity of seaweeds in the country.
Biochemical mapping of Pyrodinium bahamense unveils molecular underpinnings behind organismal processes
Subong, Bryan John J.; Malto, Zabrina Bernice L.; Lluisma, Arturo O.; Azanza, Rhodora V.; Salvador-Reyes, Lilibeth A. (MDPI, 2021-12-11)
Proteins, lipids, and carbohydrates from the harmful algal bloom (HAB)-causing organism Pyrodinium bahamense were characterized to obtain insights into the biochemical processes in this environmentally relevant dinoflagellate. Shotgun proteomics using label-free quantitation followed by proteome mapping using the P. bahamense transcriptome and translated protein databases of Marinovum algicola, Alexandrium sp., Cylindrospermopsis raciborskii, and Symbiodinium kawagutii for annotation enabled the characterization of the proteins in P. bahamense. The highest number of annotated hits were obtained from M. algicola and highlighted the contribution of microorganisms associated with P. bahamense. Proteins involved in dimethylsulfoniopropionate (DMSP) degradation such as propionyl CoA synthethase and acryloyl-CoA reductase were identified, suggesting the DMSP cleavage pathway as the preferred route in this dinoflagellate. Most of the annotated proteins were involved in amino acid biosynthesis and carbohydrate degradation and metabolism, indicating the active roles of these molecules in the vegetative stage of P. bahamense. This characterization provides baseline information on the cellular machinery and the molecular basis of the ecophysiology of P. bahamense.
C30 — A simple, rapid, scientifically valid, and low-cost method for citizen-scientists to monitor coral reefs
Licuanan, Wilfredo Y.; Mordeno, Princess Zyrlyn B.; Go, Marco V. (Elsevier, 2021-09)
The extent and speed of recent changes in reef coral abundances due to ocean warming and human impacts require more widespread capability to map and measure these changes, especially in countries like the Philippines. We present “C30”, a simple, rapid, scientifically valid, and low-cost method for skin divers or freedivers to take random photo-quadrat images within predefined stations on the upper reef slope. C30 yields coral cover data similar to those collected using the more intensive C5 method and can be as powerful in detecting small differences in reef cover. Less time is also needed for training personnel and sampling. However, more photo-quadrat images, better cameras, and closer collaboration with local scientists are required if higher precision data and estimates of coral diversity are needed from C30. C30 is a valuable tool for participatory, community-based citizen science monitoring of coral reefs.
We thank the Department of Science and TechnologyPhilippine Council for Agriculture, Aquatic and Natural Resources Research and Development (QMSR-MRRD-COR-0-1209 and PCAARRD-GIA 4478), and the Department of Environment and Natural Resources Coral Reef Visualization and Assessment, The Philippines Project for funding some of the fieldwork. The initial research on citizen-science monitoring was undertaken with funding from Oscar M. Lopez Center for Climate Change Adaptation and Disaster Risk Management Foundation, Inc., The Philippines (Grant number OMLC RG 2017-18). We also thank the DLSU Innovation and Technology Office for the patent application for the C30 monopod in the Intellectual Property Office of the Philippines. The comments and suggestions of the reviewers are acknowledged and are very much appreciated. WY Licuanan is the holder of the Br H Alfred Shields FSC Professorial Chair in Biology and Br Cresentius Richard Duerr FSC Professorial Chair in Biochemistry.
Characteristics of marine heatwaves in the Philippines
Edullantes, 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.
Characterization of Alexandrium tamutum (Dinophyceae) isolated from Philippine waters, with the rare detection of paralytic shellfish toxin
Benico, Garry; Azanza, Rhodora (Association of Systematic Biologists of the Philippines, 2022-04-01)
Alexandrium tamutum M.Montressor, A.Beran & U.John is a non-toxic, bloom-forming dinoflagellate species commonly reported in temperate waters. In this study, 8 cultures of A. tamutum established from Bolinao Channel and Manila Bay, Philippines were characterized in terms of their morphology, phylogeny and toxicity. Cells were roundish, measuring 25.5 –29.84 µm long and 26.2–28.45 µm wide. The nucleus is equatorially elongated and located at the center of the cell. The chloroplasts are numerous, golden brown in color and radially arranged. Thecal tabulation is typical of Alexandrium: APC, 4', 6'', 6c, 6s, 5''', 2''''. Shape of the taxonomically informative thecal plates such as sixth precingular plate (6'') and posterior sulcal plate (sp) was similar to A. tamutum, which confirms the species identity. However, the presence of anterior and posterior attachment pores observed in our cultured isolates is the first case in this species. Molecular phylogeny inferred from LSU rDNA and ITS supports our identification by forming a well-supported clade composed of A. tamutum strains from other geographic regions. HPLC analysis showed that A. tamutum is generally non-toxic except for strain ATC9 which has low amount of decarbamoylsaxitoxin (dcSTX), resulting to a toxicity of 0.07 fmole STX eq per cell. The present study reports the first verified occurrence of Philippine A. tamutum with reliable morphological and molecular information, including the first record in Manila Bay and first detection of PST in one strain at a certain culture period.
We acknowledge the Department of Science and Technology Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development (DOST PCAARRD) and the University of the Philippines-The Marine Science Institute (UP-MSI) for the funding support. We are grateful for the assistance of Joshua Vacarizas, Keith Pinto and Jenelyn Mendoza for the molecular and toxicity analyses of the cultures. We also acknowledge Estrelita Flores, Emelita Eugenio and Jayson Orpeza for their assistance during the fieldwork and other logistical support.
Characterizing the vertical phytoplankton distribution in the Philippine Sea off the northeastern coast of Luzon
Cordero-Bailey, Kristina; Bollozos, Iris Salud F.; Palermo, Joseph Dominic H.; Silvano, Kathleen M.; Escobar, Ma. Teresa L.; Jacinto, Gil S.; San Diego-McGlone, Maria Lourdes; David, Laura T.; Yñiguez, Aletta T. (Elsevier BV, 2021-06)
The vertical distribution of phytoplankton in the open ocean shows an increase in biomass at a depth referred to as the Subsurface Chlorophyll Maximum (SCM) that contributes significantly to the primary production of the water column. Hence, it is important to understand the dynamics that lead its formation and maintenance. This study examines the SCM in the Philippine Sea off the northeast coast of Luzon, utilizing bio-optical and empirical phytoplankton data from two oceanographic cruises conducted northeast of the island of Luzon in May/June 2011 and April/May 2012. Chlorophyll (Chl) profiles were converted to smoothed chlorophyll functions by using a b-spline basis. In 2011, the mean SCM depth was 97.24 m ± 22.33 m with mean SCM concentration of 0.43 μg/L ± 0.09 μg/L while in 2012, mean SCM was deeper at 115.45 m ± 24.25 m and mean SCM concentration of 0.31 ± 0.09 μg/L. Functional principal component analysis showed that the first principal component (PC) explained variability in the SCM depth, the second PC showed variability in the magnitude of the SCM concentration while the third PC accounted for the presence of multiple peaks. K-means clustering using the principal components resulted in three clusters which represented the offshore stations with the deepest SCM, stations within an observed cyclonic eddy with intermediate SCM and stations with coastal and shelf waters showing shallow SCM. Correlation analyses between Chl and physico-chemical and bio-optical parameters showed that Chl was positively correlated to beam attenuation, a bio-optical property that has been used as an alternative proxy for phytoplankton. This suggests that the observed SCMs represent actual increase in phytoplankton biomass. When the influence of the Kuroshio recirculation gyre was dominant in 2011, cooler temperature in surface waters was seen to significantly increase surface Chl. In 2012, highly saline waters from the tropical North Equatorial Current (NEC) waters appeared to lower the Chl distribution, particularly at the SCM. Phytoplankton abundance was recorded to be higher at the SCM than the surface in both years. In 2011, different species of diatoms dominated all clusters, except at the SCM of the coastal and shelf cluster wherein the dinoflagellate Gyrodinium grossestriatum was dominant. Most dominant species from 2011 were conspicuously absent in 2012 and there was a shift to the diatoms Fragilariopsis (surface), Thalassiosira and Rhizosolenia spp. in all clusters. These provide new insights on the phytoplankton community in relation to the changes in the oceanic circulation from subtropical North Pacific water in 2011 to tropical NEC water in 2012.
This work is Marine Science Institute contribution number 482. We would like to acknowledge Dr. Cesar Villanoy and Dr. Olivia Cabrera and the anonymous reviewers who provided invaluable inputs for the development and improvement of the paper.
Co-occurrence of a marine heatwave and a reported tomato jellyfish (Crambione mastigophora Maas, 1903) bloom in March 2020 at El Nido, Palawan, Philippines
Quilestino-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).
Complex patterns of genetic structure in the sea cucumber Holothuria (Metriatyla) scabra from the Philippines: implications for aquaculture and fishery management
Lal, Monal M.; Macahig, Deo A. S.; Juinio-Meñez, Marie A.; Altamirano, Jon P.; Noran-Baylon, Roselyn; de la Torre-de la Cruz, Margarita; Villamor, Janine L.; Gacura, Jonh Rey L.; Uy, Wilfredo H.; Mira-Honghong, Hanzel; Southgate, Paul C.; Ravago-Gotanco, Rachel (Frontiers Media SA, 2024-06-04)
The sandfish Holothuria (Metriatyla) scabra, is a high-value tropical sea cucumber harvested from wild stocks for over four centuries in multi-species fisheries across its Indo-Pacific distribution, for the global bêche-de-mer (BDM) trade. Within Southeast Asia, the Philippines is an important centre of the BDM trade, however overharvesting and largely open fishery management have resulted in declining catch volumes. Sandfish mariculture has been developed to supplement BDM supply and assist restocking efforts; however, it is heavily reliant on wild populations for broodstock supply. Consequently, to inform fishery, mariculture, germplasm and translocation management policies for both wild and captive resources, a high-resolution genomic audit of 16 wild sandfish populations was conducted, employing a proven genotyping-by-sequencing approach for this species (DArTseq). Genomic data (8,266 selectively-neutral and 117 putatively-adaptive SNPs) were used to assess fine-scale genetic structure, diversity, relatedness, population connectivity and local adaptation at both broad (biogeographic region) and local (within-biogeographic region) scales. An independent hydrodynamic particle dispersal model was also used to assess population connectivity. The overall pattern of population differentiation at the country level for H. scabra in the Philippines is complex, with nine genetic stocks and respective management units delineated across 5 biogeographic regions: (1) Celebes Sea, (2) North and (3) South Philippine Seas, (4) South China and Internal Seas and (5) Sulu Sea. Genetic connectivity is highest within proximate marine biogeographic regions (mean Fst=0.016), with greater separation evident between geographically distant sites (Fst range=0.041–0.045). Signatures of local adaptation were detected among six biogeographic regions, with genetic bottlenecks at 5 sites, particularly within historically heavily-exploited locations in the western and central Philippines. Genetic structure is influenced by geographic distance, larval dispersal capacity, species-specific larval development and settlement attributes, variable ocean current-mediated gene flow, source and sink location geography and habitat heterogeneity across the archipelago. Data reported here will inform accurate and sustainable fishery regulation, conservation of genetic diversity, direct broodstock sourcing for mariculture and guide restocking interventions across the Philippines.
Effect of the Intensified Sub‐Thermocline Eddy on strengthening the Mindanao undercurrent in 2019
Azminuddin, Fuad; Lee, Jae Hak; Jeon, Dongchull; Shin, Chang‐Woong; Villanoy, Cesar; Lee, Seok; Min, Hong Sik; Kim, Dong Guk (American Geophysical Union, 2022-02)
The northward-flowing Mindanao Undercurrent (MUC) was directly measured by acoustic Doppler current profilers from a subsurface mooring at about 8°N, 127°E during 2 years (November 2017–December 2019). Its depth covers a range from 400 m to deeper than 1,000 m with its core appearing at around 900 m. The mean velocity of MUC's core was approximately 5.8 cm s−1 with a maximum speed of about 47.6 cm s−1. The MUC was observed as a quasi-permanent current with strong intraseasonal variability (ISV) with a period of 70–80 days. Further analyses with an eddy-resolving circulation model output suggest that the ISV is closely related to sub-thermocline eddies (SEs). In this study, two types of SEs near the Philippine coast are disclosed: the westward propagating SE (SE-1) and the quasi-stational SE southeast of Mindanao Island (SE-2). The SE-1 has both cyclonic and anticyclonic polarities with the propagation speed of 7–8 cm s−1, while the SE-2 is an anticyclonic eddy that moves erratically within 4–8°N, 127–130°E with the mean translation speed of about 11 cm s−1. Even though the SE-1 plays an important role in modulating the MUC, our results show that the observed strong MUC event (May–July 2019) is evidently induced by the intensified SE-2 that moves northwestward. This study emphasizes that the SE-2 when intensified, receives more energy from the strengthened New Guinea Coastal Undercurrent and loses the energy northward along the Philippine coast by intensifying the MUC.
This study was part of the project entitled “study on air–sea interaction and process of rapidly intensifying Typhoon in the northwestern Pacific” (PM61670) funded by the Ministry of Oceans and Fisheries, Rep. of Korea. This study was also partly supported by the project entitled “Influences of the Northwest Pacific circulation and climate variability on the Korean water changes and material cycle I—The role of Jeju warm current and its variability” (PEA0011) funded by Korea Institute of Ocean Science and Technology (KIOST). The mooring data used in this study were provided by KIOST and are available from the KIOST live access server (http://las.kiost.ac.kr/data_adcp/). The model data are freely available from Mercator Ocean (https://resources.marine.copernicus.eu/?option=com_csw&view=details&product_id=GLOBAL_ANALYSIS_FORECAST_PHY_001_024).
Effects of monsoons and storms on the structuring and diversity of picoeukaryotic microbial communities in a tropical coastal environment
De La Cruz, Maria Anna Michaela; Hingpit, Brian William; Guillou, Laure; Onda, Deo Florence L. (Elsevier, 2023-06)
Picoeukaryotes are key components in marine ecosystems that play crucial roles in food webs and biogeochemical cycles. Despite their significance, many aspects of their community ecology and diversity remain understudied. Here, we investigated the taxonomic and functional diversity of picoeukaryotic communities in response to monsoonal patterns and weather disturbances brought about by storms, characterizing tropical coastal regions. To do this, water samples were collected almost weekly or bi-weekly at a single location in a tropical coastal environment covering the late northeast (NE) and southwest (SW) monsoons. We then performed high-throughput amplicon sequencing of the V4 region of the 18S rRNA gene to generate taxonomic profiles of the communities across time. Clustering based on environmental parameters grouped our samples into months associated with NE monsoon, SW monsoon, and stormy SW monsoon, demonstrating seasonality influenced by monsoons and storms, typically observed in tropical coastal waters. In comparison, clustering based on abundance only grouped the samples into NE and SW monsoon, with most communities during storm period joining the NE monsoon samples. These samples exhibited greater diversity, with smaller taxa such as Syndiniales, Prymnesiophyceae, Picozoa, Cercozoa, Stramenopiles, and Chlorophytes being the most abundant groups present. In contrast, SW monsoon samples have lower diversity but have become generally dominated by large-celled taxa, mostly diatoms. Multivariate and correlation analyses both revealed nitrate as the strongest environmental driver of the picoeukaryotic community structuring. Meanwhile, network analysis grouped the taxa into three modules, more consistent with the clustering based on environmental parameters, implying that although storms may not significantly change the community composition, they may however influence the dominating taxa. Each module was composed of a unique set of co-occurring taxa, highlighting high turnover of picoeukaryotic communities between each season. In addition, our results showed that SW monsoon-associated module had higher interconnectivity than other modules, suggesting that the interactions during this period may be less species-specific, thus, more adaptable than during NE monsoon. However, we observed that extreme fluctuations caused by storms could have possibly allowed for selection of dominant taxa. Shotgun metagenomic sequencing of representative samples from each monsoon period also revealed that differently abundant functional genes, particularly genes associated to nitrogen metabolism, might have also helped in adaptation to the changing nutrient conditions. Our observations provide new insights on the potential trajectory of microbial communities under environmental stresses, which are important in understanding the implications of emerging threats such as coastal eutrophication and climate change.
Elevated seawater temperatures affect embryonic and larval development in the giant clam Tridacna gigas (Cardiidae: Tridacninae)
Enricuso, Odette B.; Conaco, Cecilia; Sayco, Sherry Lyn G.; Neo, Mei Lin; Cabaitan, Patrick (Oxford Academic, 2018-11-17)
Giant clams are the largest bivalve molluscs and play a key role in coral reef ecosystems. Almost all species are considered endangered or vulnerable to extinction, thus requiring intervention through culturing and restocking. Although successful culture techniques have been developed, the responses of giant clam embryos and larvae to environmental factors, such as seawater temperature, are not yet fully understood. In this study, fertilization, development and survival of Tridacna gigas larvae were observed at low (28 °C), medium (30 °C) and high (33 °C) seawater temperatures. Fertilization success was not significantly different between the water temperatures tested. At 28 °C, ciliated gastrulae appeared first at 12 h postfertilization (hpf) and trochophore larvae at 24 hpf. In contrast, more rapid development was observed at 30 °C and 33 °C, with ciliated gastrulae first appearing at 9 hpf and trochophore larvae at 18 hpf. Veliger larvae were observed after 48 h at 28 °C and 30 °C. No veligers were observed at 33 °C, but a greater proportion of embryos and larvae exhibited developmental abnormalities at this temperature compared with the other treatments. Larval survival was lowest at 33 °C at the 12 and 24 h timepoints, although there was no longer a significant difference across treatments after 48 h. Furthermore, post-settlement survival of juveniles subjected to different seawater temperatures for 22 d starting at 8 d postfertilization (dpf) was lowest at 33 °C. These findings reveal that higher water temperatures promote rapid progression through early development, but result in lower overall survival as a consequence of abnormal development and reduced post-settlement survival.
The authors acknowledge Julio Curiano and the staff of the Bolinao Marine Laboratory for assistance with experiments. This work was supported in part by the University of the Philippines Marine Science Institute; a grant from the National Geographic Society (ASIA-08-15) to PCC; a grant from the Department of Science and Technology Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development (QMSR-MRRD-MEC-295-1449) to PCC and CC; and a Department of Science and Technology Science Education Institute graduate scholarship to OBE. MLN acknowledges the support of the National Research Foundation Singapore for research at the St John’s Island National Marine Laboratory.
Endosymbiotic dinoflagellates pump iron: differences in iron and other trace metal needs among the Symbiodiniaceae
Reich, Hannah G.; Rodriguez, Irene B.; LaJeunesse, Todd C.; Ho, Tung-Yuan (Springer, 2020-03-06)
Iron (Fe) is essential to the physiology and growth of marine phytoplankton. It remains unclear how important iron is to the functional ecology of symbiotic dinoflagellates in the family Symbiodiniaceae, and whether limitations in iron ultimately affect the health and productivity of coral hosts, especially during episodes of ocean warming. Five Symbiodiniaceae species (spanning three genera) were used to investigate the effects of reduced iron availability on cell growth and the acquisition of other trace metals. When grown under iron replete conditions, intracellular iron quotas (content) reflected a large biochemical demand and ranged from 7.8 to 23.1 mmol Fe mol Phosphorus−1. Symbiodinium necroappetens was the only species that acclimated and maintained high growth rates while subjected to the lowest iron treatment (250 pM Fe′). Cultures surviving under low iron concentrations experienced changes in cellular concentrations (and presumably their use as cofactors) of other trace metals (e.g., zinc, copper, cobalt, manganese, nickel, molybdenum, vanadium), in ways that were species-specific, and possibly related to the natural ecology of each species. These changes in trace metal contents may have cascading effects on vital biochemical functions such as metalloenzyme activities, photosynthetic performance, and macronutrient assimilation. Furthermore, these species-specific responses to iron limitation provide a basis for investigations on how iron availability effects cellular processes among species and genera of Symbiodiniaceae, and ultimately how metal shortages modulate the response of coral–algal mutualisms to physiological stressors.
The authors thank Jie-Cheng Chang, Wan-Yen Cheng, and Wan-Chen Tu for technical support. This work was funded by NSF-EAPSI and MOST #1713926 (to HGR), NASA PA Space Grant Fellowship (to HGR), NSF-BIO-OCE #1636022 (to TCL), MOST 106-2611-M-001-003 (to TYH), MOST 107-2611-M-001-001 (to TYH), and Academia Sinica Career Development Award (to TYH). We are grateful to the two anonymous reviewers whose comments improved the quality of the paper.
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.
Expanding ocean food production under climate change
Free, Christopher M.; Cabral, Reniel B.; Froehlich, Halley E.; Battista, Willow; Ojea, Elena; O’Reilly, Erin; Palardy, James E.; García Molinos, Jorge; Siegel, Katherine J.; Arnason, Ragnar; Juinio–Meñez, Marie Antonette; Fabricius, Katharina; Turley, Carol; Gaines, Steven D. (Springer, 2022-04-27)
As the human population and demand for food grow, the ocean will be called on to provide increasing amounts of seafood. Although fisheries reforms and advances in offshore aquaculture (hereafter ‘mariculture’) could increase production, the true future of seafood depends on human responses to climate change. Here we investigated whether coordinated reforms in fisheries and mariculture could increase seafood production per capita under climate change. We find that climate-adaptive fisheries reforms will be necessary but insufficient to maintain global seafood production per capita, even with aggressive reductions in greenhouse-gas emissions. However, the potential for sustainable mariculture to increase seafood per capita is vast and could increase seafood production per capita under all but the most severe emissions scenario. These increases are contingent on fisheries reforms, continued advances in feed technology and the establishment of effective mariculture governance and best practices. Furthermore, dramatically curbing emissions is essential for reducing inequities, increasing reform efficacy and mitigating risks unaccounted for in our analysis. Although climate change will challenge the ocean’s ability to meet growing food demands, the ocean could produce more food than it does currently through swift and ambitious action to reduce emissions, reform capture fisheries and expand sustainable mariculture operations.
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