Northern Palawan Research Articles

Abundance and Distribution of the Larvae of Family Carangidae in the Philippine Waters

A spatio-temporal study on the abundance of the Carangidae larvae in Philippine waters was conducted to minimize the lack of information on their spawning grounds. The study analyzed fish larvae data from M/V DA-BFAR cruises between 2006 and 2018, covering various areas in the Philippines. A total of 589 sampling stations were examined and grouped into seven zones: Batanes-Polillo, Catanduanes-Eastern Samar, Inland waters (Bohol Sea, Davao Gulf, Lagonoy Gulf, Leyte Gulf, Ragay Gulf, Sibuyan Sea, Samar Sea, Tayabas Bay, and the Visayan Sea), Mindanao-Sulawesi Sea, Sulu Sea, West Philippine Sea, and Davao Oriental-Surigao. The results indicated a patchy distribution of carangid larvae, with the highest concentration found in northern Palawan (Sulu Sea and West Philippine Sea areas). The total density of composite samples ranged from 1 to 865 larvae/1000m³. The abundance showed fluctuation over the years, with higher densities in 2016 and 2017 compared to other sampling years. The highest mean density was observed in September 2017 in the West Philippine Sea, while the lowest was recorded in May 2015 in Batanes-Polillo waters. The variations in carangid larvae abundance in Philippine waters are likely related to the species' spawning habits, as the timing of reproduction may vary by region based on ecological factors. Other factors influencing the results include sampling incidence and the sampling period of M/V DA-BFAR.

Blended Learning Modality in Selected Island Elementary Schools of Northern Palawan, Philippines

Blended Learning Modality in Selected Island Elementary Schools of Northern Palawan, Philippines

Preliminary Assessment of Anomalously High Background Radioactivity in Makinit Hot Spring, El Nido, Philippines

Hot springs in the Philippines are found mostly near volcanic regions and are the least places with possibly high background radiation. However, Makinit hot spring in El Nido, Palawan exists not only on the tectonically stable northern Palawan Microcontinental Block but also records anomalously high natural radioactivity. To quantify and determine the nature of radioactivity, this study conducted a preliminary radiological and geochemical study in the vicinity of this hot spring. The measured average specific activities of uranium and thorium were 1528.62 and 920.96 Bq/kg, and these exceed world median values on terrestrial radionuclides in the soil of 35 and 30 Bq/kg by 44 and 31 times higher, respectively. The average values of all seven calculated radiological risk parameters – namely, dose rate with an amount of 13.77 mSv/y, radium equivalent of 2862.10 Bq/kg, external and internal hazard indices of 7.73 and 11.86, respectively, absorbed gamma dose rate of 1271.42 nGy/h, annual effective dose equivalent of 1.56 mSv/y, and excess lifetime cancer risk of 5.46 x 10–3 – go beyond reference limits set by the UNSCEAR. The preliminary assessment of spring water physicochemical properties showed that the water temperature is greater than 55 °C and the pH averages around 6.62, indicating weak acid-neutral hot waters and a low to moderate temperature geothermal system. The sediments surrounding the Makinit hot spring were analyzed to be travertine, composed only of calcite, suggesting that the uranium and thorium ions are potentially bonded or are associated with the Ca-bearing mineral. This study can serve as a baseline for further research regarding the source of radioactivity and geothermal heat source and as a consideration for the development of the Makinit hot spring area.

Re-examination of the Base Miocene Unconformity in west Sabah, Malaysia, and stratigraphic evidence against a slab-pull subduction model

This review chiefly examines data on the regionally important Base Miocene Unconformity , confirming its age and expression in west Sabah, then integrates this with data on the tectono-stratigraphic development of the broader Sabah to Palawan region. The two unconformities described (the Base Miocene Unconformity and the younger Deep Regional Unconformity) were both produced when deformation abruptly stopped, leaving erosional surfaces that were then transgressed. The ages of these two events are c. 24 and 12–13 Ma respectively, and the areas affected by the prior uplift and erosion can be mapped. The results are incompatible with widely cited plate tectonic models that describe closure of a postulated Proto-South China Sea [PSCS]. These prior models had assumed plate drift ended with collision at plate docking over a PSCS suture in about mid Early Miocene times. However, stratigraphic data shows that Early Miocene times were a period of quiescence across Sabah, with mostly mild subsidence . It is therefore proposed that plate drift in the SCS could not have been linked to any type of subduction process anywhere around western Sabah. The absence of any plate docking or any Oligocene through Middle Miocene compression around northern Palawan is a further anomaly to the old subduction based tectonic model.

Onychothemis yvonneae spec. nov. (Odonata: Libellulidae), a new dragonfly from a lowland riverine forest in northern Palawan, Philippines

The Cleopatra’s Needle Mountain Range (CNMR) in northern Palawan includes one of the largest remaining patches of primary forest in the Philippines and has a high conservation value. To provide scientific baseline information to recognize the CNMR as a protected area, biologists mapped its biodiversity during fieldwork conducted from October to December 2014. The present study proposes a new species of Odonata discovered during the survey. Onychothemis yvonneae spec. nov. is described, illustrated, and compared with its nearest allies. The new species is the second member of the genus Onychothemis in the Philippines and is the seventh known overall. Onychothemis yvonneae appears to be most closely related to O. testacea and O. tonkinensis.

Seascape shadows: Life in the ruins of the edible bird's nest harvest in northern Palawan, the Philippines

The intensifying extraction, privatization, and conservation of maritime spaces are transforming seascapes globally. Amidst rapid coastal change and the ambiguous reconfiguration of oceans as frontiers are coastal dwellers who occupy the shadows of these seascapes. In contrast to the capture of high-profile marine species, the harvest of the edible nests of balinsasayaw (swiftlet, Aerodramus fuciphagus) remains largely concealed at the interstitial spaces between land, coast, and sea. In the Philippines, harvesters known as busyador negotiate social relations, political networks, and karst systems to extract these lucrative nests. Despite the nest industry growing in value in Southeast Asia, we show how the busyador struggle in precarious social relations and spaces peripheral to coastal governance in northern Palawan Island. Building on the concept of ‘seascape assemblages’, we emphasize the importance of the less visible human-nonhuman relations that shape the nest harvest and trade. We trace the marginal social histories of the balinsasayaw by highlighting the precarious nature of the harvest, revealing how the busyador are subject to unfair working conditions, dispossession, and violence. We argue that as state actors and local elites reconfigure oceans as frontiers for development and conservation, struggles over labour and tenure rights, livelihood opportunities, and justice at sea are disregarded.

Identification of Priority Sites to Support Management of Commercially Important Sea Cucumber Species by Applying Infomap and Habitat Filters to Larval Dispersal Data

Stocks of commercially valuable sea cucumber species have declined in most tropical countries, which supply majority of the global demand. This work aimed to locate priority sites for the management ofHolothuria scabraandStichopus horrensin the western central Philippines. A passive larval dispersal model was run under four monsoonal regimes (Northeast monsoon, dry-transition, Southwest monsoon, and early Northeast monsoon), and the results subjected to theInfomapnetwork detection algorithm. Three clusters of closely related geographical nodes were identified [southeastern Palawan (Group I), western Panay and eastern Mindoro (Group II), and northern and western Palawan with western Mindoro (Group III)]. Remotely sensed habitat data were used to parameterize the degree of connectivity observed among sites (H. scabraspawning and settlement requires the presence of seagrass and mangrove, whileS. horrensrequires corals and seagrass). Local retention, self-recruitment, settlement success and sink diversity were then calculated for each node with suitable habitat. The locations were ranked according to each metric and those with higher larval export rates, a higher diversity of larval sources and a high degree of successful larval contribution to other sites were deemed crucial for the management of wild populations. Sixteen high-priority sites were identified, distributed mainly along northern Palawan and western Panay. Six sites were common for both species at different seasons, and no single location fulfilled all stated criteria across the four seasons and both sea cucumber species considered. The priority sites for management could serve as broodstock selection and juvenile restocking areas for aquaculture production clusters, which when properly implemented, could lead to an increase in sea cucumber production and contribute to natural populations. On a broader scale, the designation of closely related clusters and incorporation of habitat requirements to dispersal data provided critical input for the delineation of ecologically meaningful management units for sea cucumbers within the region.

Exceptionally species-rich assemblages of modern larger benthic foraminifera from nearshore reefs in northern Palawan (Philippines)

Symbiont-bearing larger benthic foraminifera (LBF) are ubiquitous components of tropical and subtropical carbonate-rich shallow-water habitats and contribute substantially to coral reef accretion and stability. More than 60 species of LBF are currently described from the Indo-Pacific Ocean with the Philippines being recently identified as their potential center of maximum species richness.The Palawan archipelago, also known as the “last ecological frontier” of the Philippines and a hotspot of biodiversity, attracts a growing number of tourists due to its comparatively intact marine environments and picturesque landscapes. Here, we document and illustrate the species-rich fauna of modern LBF from shallow nearshore habitats in northern Palawan. Sampling covered the northernmost part of Palawan's South China and Sulu Sea coasts including the Calamian Islands group. A total of 24 samples were taken from fore-reef slopes, inter-reef areas, a back-reef, seagrass leaves with a nearby mangrove swamp, and a WW2 shipwreck at depths between 0 to 25m. We recorded a total of 44 LBF morphospecies, a number that is among the highest reported so far. Heterostegina depressa and Calcarina mayori were identified as the most widely distributed taxa in the study area. We further describe Peneroplis hoheneggeri nov. sp. as a new species of Peneroplis de Montfort. The newly described peneroplid is characterized by single rows of large pits and was previously also documented from Micronesia. Our survey supports the designation of northern Palawan as an exceptionally biodiverse ecoregion with high priority for marine conservation efforts.

Detrital zircon provenance record of the Oligocene Zhuhai Formation in the Pearl River Mouth Basin, northern South China Sea

Abstract The Oligocene Zhuhai Formation has been proven to be one of the main reservoirs in the Pearl River Mouth Basin in the northern South China Sea but its sedimentary provenance remains uncertain and controversial. Here we conducted a systematic study by U-Pb analysis of detrital zircon of the Zhuhai Formation in order to identify the source terrane, investigate the sedimentary source, and establish the framework for the provenance variation during the Oligocene. The study suggests that the detrital zircon in the different structural units reveal marked spatial differences in their age compositions that correlate with the changing sources. The western and eastern parts of the basin have a significantly different provenance manifested by the age compositions of the detrital sediments. The western basin generally has a relatively complex age spectrum and is characterized by a multi-peak distribution, suggesting that the main source was derived from the southern margin of the South China Block. In contrast, the eastern basin displays a dominant population ranging from 131 to 142 Ma, which implies that the sediments were mainly eroded from a nearby source. Our data demonstrate that the Cathaysia Block hinterland and the intrabasinal sources provided dominant provenance contributions to the Pearl River Mouth Basin during the Oligocene. Additionally, Hainan Island and Central Vietnam (eastern Indochina Block) do not appear to have been important sources, whereas Luzon Island and northern Palawan probably provided negligible contributions to the basin during the same time period.

Satellite tracking of juvenile whale sharks in the Sulu and Bohol Seas, Philippines.

The whale shark Rhincodon typus was uplisted to ‘Endangered’ in the 2016 IUCN Red List due to >50% population decline, largely caused by continued exploitation in the Indo-Pacific. Though the Philippines protected the whale shark in 1998, concerns remain due to continued take in regional waters. In light of this, understanding the movements of whale sharks in the Philippines, one of the most important hotspots for the species, is vital. We tagged 17 juvenile whale sharks with towed SPOT5 tags from three general areas in the Sulu and Bohol Seas: Panaon Island in Southern Leyte, northern Mindanao, and Tubbataha Reefs Natural Park (TRNP). The sharks all remained in Philippine waters for the duration of tracking (6–126 days, mean 64). Individuals travelled 86–2,580 km (mean 887 km) at a mean horizontal speed of 15.5 ± 13.0 SD km day−1. Whale sharks tagged in Panaon Island and Mindanao remained close to shore but still spent significant time off the shelf (>200 m). Sharks tagged at TRNP spent most of their time offshore in the Sulu Sea. Three of twelve whale sharks tagged in the Bohol Sea moved through to the Sulu Sea, whilst two others moved east through the Surigao Strait to the eastern coast of Leyte. One individual tagged at TRNP moved to northern Palawan, and subsequently to the eastern coast of Mindanao in the Pacific Ocean. Based on inferred relationships with temperature histograms, whale sharks performed most deep dives (>200 m) during the night, in contrast to results from whale sharks elsewhere. While all sharks stayed in national waters, our results highlight the high mobility of juvenile whale sharks and demonstrate their connectivity across the Sulu and Bohol Seas, highlighting the importance of the area for this endangered species.

Geochemical Behavior of Rare Earth Elements in Weathered Granitic Rocks in Northern Palawan, Philippines

AbstractWeathered crust of granitic rocks of two geochemically similar plutons that differ in age of magmatism were investigated in the Philippines. These are the Cretaceous Daroctan Granite and the Middle Miocene Kapoas Granitoid located in Palawan Island, a part of the Palawan Continental Block derived from the continental margin of southeastern Eurasia. Both plutons are composed of biotite granodiorite and biotite granite and are geochemically characterized as ilmenite series, high‐K calc‐alkaline, intermediate I‐ and S‐types, and peraluminous.Light rare earth element (LREE) content of the weathered granitic crusts in the Kapoas Granitoid is higher than that in the Daroctan Granite, and LREE are enriched in the Daroctan Granite compared to the parent granitic rocks. In both plutons, the residual REE‐bearing minerals are mostly monazite. Allanite is only present in the Kapoas Granitoid while the Daroctan Granite contains xenotime. The Kapoas Granitoid pluton shows potential for placer‐type LREE deposit as observed in the elevated LREE content of the stream and beach sediments containing La, Ce, Nd and Sm up to >10,000 ppm. Sequential leaching extraction of REE using eight reagents which selectively dissolved REE with different mode of occurrence (i.e. water soluble, ion‐exchangeable salts, Pb‐displaceable, acid soluble, Mn‐oxide occluded, organically‐bound, amorphous Fe‐oxide occluded, and crystalline Fe‐oxide occluded forms), show that the Daroctan Granite has a potential for ion‐adsorption type REE resource with proportion of extracted REE ranging from 53 to 74 % among ΣREE. Formation of secondary REE‐bearing minerals, such as cerianite formed on the surface of clay minerals, results in enrichment of REE.

Imprints of Late Mesozoic tectono-magmatic events on Palawan Continental Block in northern Palawan, Philippines

A recent investigation in Palawan Island led to the recognition of the Daroctan Granite, a pluton that intruded the Mesozoic mélange in the northernmost part. The occurrence and age of the magmatism is presented in this study as well as the maximum age of deposition for some Late Mesozoic lithostratigraphic units. Geochronological studies on zircon and monazite was carried out to unravel the Late Mesozoic tectonic evolution of this area. Monazite U-Th-total Pb dating was used to determine the age of the Daroctan Granite, which yielded a Late Cretaceous age similar to some of the Mesozoic granites surrounding the South China Sea. Zircon U-Pb and monazite U-Th-total Pb dating were also used to determine the maximum age of deposition of the sedimentary units belonging to the Guinlo Formation and Tumarbong Semi-schist. The results show a Jurassic to Early Cretaceous age range with a Late Cretaceous maximum age of deposition for the meta-sedimentary units. This sliver of the Palawan Continental Block, which is composed of accreted units, might have been located at the margin of the continent-ocean collision during the Mesozoic wherein detrital minerals with mostly Late Cretaceous ages were deposited. It was later intruded by the Daroctan Granite and eventually broke off from the southeastern Eurasian margin. These findings provide additional constraints on the tectonic evolution of the Palawan Continental Block.

The ecology of Altrichthys azurelineatus and A. curatus, two damselfishes that lack a pelagic larval phase

Out of more than 380 species of damselfish, only three lack a pelagic larval phase, Acanthochromis polyacanthus, that ranges from the Philippines to the Great Barrier Reef, and two species in the genus Altrichthys, A. azurelineatus and A. curatus, that are restricted to the Calamian Archipelago (Palawan province) in the Philippines. Therefore in a very restricted geographic area, northern Palawan, Philippines, all three species co-occur. The goal of this study was to fill a knowledge gap about the ecology of Altrichthys, where very little is currently known. Using census and behavioral approaches at 14 sites on six islands, we were able to identify adult densities, nest densities, nesting habitat preference, and brood behavior and abundance. We found that densities were very high (more than 17 individuals/100 m2 for one species) and A. azurelineatus may be displacing A. curatus at deeper depths where habitat seems of higher quality. Only one out of 14 surveyed sites contained only one species, Altrichthys curatus. Different habitat use and feeding behavior suggest that niche partitioning may play an important role in the life history of these sympatric species.

Adaptive and integrated culture production systems for the tropical sea cucumber Holothuria scabra

Unregulated harvesting and trade have resulted in the depletion of the sea cucumber resources worldwide. Culture-based production and resource management systems are being developed to restore depleted populations and increase the supply of premium-grade sized Holothuria scabra. An adaptive and integrated socio-ecological framework to optimize production potentials and enhance sustainability through production clusters is proposed. The viability of this was tested in northern Palawan and south central Mindanao in partnership with commercial marine fish culture companies and small-scale fishers. The culture production system adopted in each site depended on existing facilities, climate and access to suitable nursery and grow-out areas. Adoption of different ocean nursery and grow-out systems, coupled with spatio-temporal planning reduced environmental constraints and increased juvenile production. Community trials validated that ocean-based systems can be readily adopted by small-scale fishers. The availability of a range of cost-effective production methods for post-metamorphic juveniles provided opportunity for participation of diverse stakeholders including small-scale fishers. Understanding of the biophysical and economic considerations for different production systems, and the relative capacity of stakeholders to manage threats, reduces their vulnerability to economic loses. Multi-sectoral involvement and multiplication of sandfish production clusters confer resilience for production systems and enable economies of scale while facilitating responsible management of genetic stocks.

Damage Assessment and Recovery Monitoring of the Mangrove Forests in Calauit Island Affected by Typhoon Yolanda (Haiyan)

Calauit island is one of the islands in the Calamian Group of Islands in northern Palawan. The island is truly blessed with bountiful mangrove resources which provide the Tagbanuas enormous economic and ecological importance. Not known to many, Calauit island became the exit point of typhoon Yolanda causing tremendous damage to mangrove area. The study assessed the extent of damage and the recovery potential of Calauit mangrove forests from the devastation of Typhoon Yolanda. Ten sampling quadrats were established in areas where trees were observed to be 100% defoliated. Individual trees (≥ 1cm diameter) inside each quadrat were measured and evaluated based on the assessment matrix developed in this study. Results of our assessment revealed serious damage of mangroves in Calauit island. About 60% of the mangrove forests was severely affected by Typhoon Yolanda. Eight months after the typhoon, 21% of the trees have fully-recovered crown (all branches were able to develop leaves), 70% are still defoliated and 22% were already dead. Four of the 10 quadrats showed high potential for recovery as evidenced by a lot of seedlings (≥ 25 seedlings) to serve as new regenerations. Conversely, there are four quadrats without any seedling recorded. Three monitoring plots were established for continuous monitoring of the recovery of the mangrove ecosystems. A course of actions was recommended to facilitate the recovery of mangroves in Caluit island, and to bring back the economic benefits from the forest.

THREATS AND OPPORTUNITIES IN SELECTED BARANGAYS AT THE MUNICIPALITY OF CORON, PALAWAN PROVINCE, PHILIPPINES

The Municipality of Coron in northern Palawan is one of the five municipalities where the Malampaya Natural Gas Project (MNGP) pipeline passes through from El Nido, Palawan to Batangas City. Seven barangays in the municipality were chosen by Malampaya Foundation Inc. (MFI) as the focus of its social development (SD) projects in the immediate future. These are barangays I and VI in the “poblacion” and the far-flung barangays of Marcilla, Bulalacao, Banuang Daan, Cabugao, and Malawig. As commissioned by MFI, the Palawan State University‟s Center for Strategic Policy and Governance undertook an integrated threats analysis to identify critical needs and propose a package of high impact projects. It uses a rapid rural appraisal (RRA) approach and relies on primary data gathered through field reconnaissance, household interviews, key informant interviews, and focus group discussions. Fieldwork was on 21-28 February 2013 while the validation of results with stakeholders was held on 27 May 2013. The top problems and threats in all seven barangays pertain to limited employment opportunities, inadequate educational infrastructure, poor access to potable water, and food insecurity. Other identified problems include inflation, unemployment, natural disasters (including climate change impacts), juvenile delinquency, and garbage and waste management. While tourism has improved the municipality‟s economy in recent years, it also contributed threats and problems that may adversely affect the environment and lives of the residents. Investments in public services must therefore be provided to upgrade delivery of the needed basic services and facilitate movement of people and products to the town center. The barangays have bio-physical, economic and livelihood, and institutional/governance capital that can be tapped to support these investments. The bigger challenge is how to influence the local government sector and he political leaders to have a stronger commitment and participation in providing solutions.

Mobility of early islanders in the Philippines during the Terminal Pleistocene/Early Holocene boundary: pXRF-analysis of obsidian artefacts

The Philippine archipelago spans over two distinct biogeographic zones, Sundaland and Wallacea. We report in this paper on finds from Ilin Island just off the coast of SW-Mindoro, and El Nido in Northern Palawan. While the island of Palawan is linked to Sundaland, Mindoro and Ilin Island belong to Wallacea, east of Huxley's Line. Ongoing archaeological investigations at Bubog 1 Rockshelter on Ilin Island and Ille Cave & Rockshelter in northern Palawan, delivered obsidian artefacts, found in Terminal Pleistocene and Early Holocene layers. PXRF analysis of the obsidian samples from Mindoro and Palawan shows that they were coming from the same, yet unknown source. They clearly indicate that the two distinct paleogeographical regions were linked to each other, suggesting human interaction and maritime networks as early as ca. 12ka BP. The results of this study contribute substantially to our understanding of the mobility of early islanders during the Terminal Pleistocene and the processes of human island adaptation and enhance our current knowledge of subsistence strategies across the region.

Observations of the temporal variability in aerosol properties and their relationships to meteorology in the summer monsoonal South China Sea/East Sea: the scale-dependent role of monsoonal flows, the Madden–Julian Oscillation, tropical cyclones, squall lines and cold pools

Abstract. In a joint NRL/Manila Observatory mission, as part of the Seven SouthEast Asian Studies program (7-SEAS), a 2-week, late September 2011 research cruise in the northern Palawan archipelago was undertaken to observe the nature of southwest monsoonal aerosol particles in the South China Sea/East Sea (SCS/ES) and Sulu Sea region. Previous analyses suggested this region as a receptor for biomass burning from Borneo and Sumatra for boundary layer air entering the monsoonal trough. Anthropogenic pollution and biofuel emissions are also ubiquitous, as is heavy shipping traffic. Here, we provide an overview of the regional environment during the cruise, a time series of key aerosol and meteorological parameters, and their interrelationships. Overall, this cruise provides a narrative of the processes that control regional aerosol loadings and their possible feedbacks with clouds and precipitation. While 2011 was a moderate El Niño–Southern Oscillation (ENSO) La Niña year, higher burning activity and lower precipitation was more typical of neutral conditions. The large-scale aerosol environment was modulated by the Madden–Julian Oscillation (MJO) and its associated tropical cyclone (TC) activity in a manner consistent with the conceptual analysis performed by Reid et al. (2012). Advancement of the MJO from phase 3 to 6 with accompanying cyclogenesis during the cruise period strengthened flow patterns in the SCS/ES that modulated aerosol life cycle. TC inflow arms of significant convection sometimes span from Sumatra to Luzon, resulting in very low particle concentrations (minimum condensation nuclei CN < 150 cm−3, non-sea-salt PM2.5 < 1 μg m−3). However, elevated carbon monoxide levels were occasionally observed suggesting passage of polluted air masses whose aerosol particles had been rained out. Conversely, two drier periods occurred with higher aerosol particle concentrations originating from Borneo and Southern Sumatra (CN > 3000 cm−3 and non-sea-salt PM2.5 10–25 μg m−3). These cases corresponded with two different mechanisms of convection suppression: lower free-tropospheric dry-air intrusion from the Indian Ocean, and large-scale TC-induced subsidence. Veering vertical wind shear also resulted in aerosol transport into this region being mainly in the marine boundary layer (MBL), although lower free troposphere transport was possible on the western sides of Sumatra and Borneo. At the hourly time scale, particle concentrations were observed to be modulated by integer factors through convection and associated cold pools. Geostationary satellite observations suggest that convection often takes the form of squall lines, which are bowed up to 500 km across the monsoonal flow and 50 km wide. These squall lines, initiated by cold pools from large thunderstorms and likely sustained by a veering vertical wind shear and aforementioned mid-troposphere dry layers, propagated over 1500 km across the entirety of the SCS/ES, effectively cutting large swaths of MBL aerosol particles out of the region. Our conclusion is that while large-scale flow patterns are very important in modulating convection, and hence in allowing long-range transport of smoke and pollution, more short-lived phenomena can modulate cloud condensation nuclei (CCN) concentrations in the region, resulting in pockets of clean and polluted MBL air. This will no doubt complicate large scale comparisons of aerosol–cloud interaction.

The Cretaceous and Cenozoic tectonic evolution of Southeast Asia

Abstract. Tectonic reconstructions of Southeast Asia have given rise to numerous controversies that include the accretionary history of Sundaland and the enigmatic tectonic origin of the proto-South China Sea. We assimilate a diversity of geological and geophysical observations into a new regional plate model, coupled to a global model, to address these debates. Our approach takes into account terrane suturing and accretion histories, the location of subducted slabs imaged in mantle tomography in order to constrain the evolution of regional subduction zones, as well as plausible absolute and relative plate velocities and tectonic driving mechanisms. We propose a scenario of rifting from northern Gondwana in the latest Jurassic, driven by northward slab pull from north-dipping subduction of Tethyan crust beneath Eurasia, to detach East Java, Mangkalihat, southeast Borneo and West Sulawesi blocks that collided with a Tethyan intra-oceanic subduction zone in the mid-Cretaceous and subsequently accreted to the Sunda margin (i.e., southwest Borneo core) in the Late Cretaceous. In accounting for the evolution of plate boundaries, we propose that the Philippine Sea plate originated on the periphery of Tethyan crust forming this northward conveyor. We implement a revised model for the Tethyan intra-oceanic subduction zones to reconcile convergence rates, changes in volcanism and the obduction of ophiolites. In our model the northward margin of Greater India collides with the Kohistan–Ladakh intra-oceanic arc at ∼53 Ma, followed by continent–continent collision closing the Shyok and Indus–Tsangpo suture zones between ∼42 and 34 Ma. We also account for the back-arc opening of the proto-South China Sea from ∼65 Ma, consistent with extension along east Asia and the formation of supra-subduction zone ophiolites presently found on the island of Mindoro. The related rifting likely detached the Semitau continental fragment from South China, which accreted to northern Borneo in the mid-Eocene, to account for the Sarawak Orogeny. Rifting then re-initiated along southeast China by 37 Ma to open the South China Sea, resulting in the complete consumption of proto-South China Sea by ∼17 Ma when the collision of the Dangerous Grounds and northern Palawan blocks with northern Borneo choked the subduction zone to result in the Sabah Orogeny and the obduction of ophiolites in Palawan and Mindoro. We conclude that the counterclockwise rotation of Borneo was accommodated by oroclinal bending consistent with paleomagnetic constraints, the curved lithospheric lineaments observed in gravity anomalies of the Java Sea and the curvature of the Cretaceous Natuna paleo-subduction zone. We complete our model by constructing a time-dependent network of topological plate boundaries and gridded paleo-ages of oceanic basins, allowing us to compare our plate model evolution to seismic tomography. In particular, slabs observed at depths shallower than ∼1000 km beneath northern Borneo and the South China Sea are likely to be remnants of the proto-South China Sea basin.

Aquatic Coleoptera of the Lake Manguao Catchment, Palawan, the Philippines

Results of an inventory of the aquatic and paraaquatic beetle fauna (Insecta: Coleoptera) of small streams in a lake catchment of northern Palawan are presented. Thirty-two sample sites and the sampling methods used are described herein. A total of 56 species taxa were recorded, with the majority of the collected material determined to species level. References and information on ecology, distribution and collection sites are given for each identified taxon. Some taxa are recorded for the first time in the Philippines, and endemic and undescribed taxa are discussed. Additional environmental data of the sampled aquatic and the surrounding terrestrial habitats are provided and discussed in comparison with data of previous surveys in the area.