West Central Philippines Research Articles

Ati of Nagpana, Barotac Viejo, West Central Philippines: Ethnic Identity, Issues, and Challenges

ABSTRACT In compliance with the mandates of the Philippine Constitution, the government has established a number of protected areas for indigenous people. Among them are the Ati of Nagpana, Barotac Viejo, Iloilo, one of the largest Ati communities in Panay. Key informant interviewing and a focus group discussion were conducted to describe the sociodemographic characteristics of the community and the social behavior of the Ati as shaped by the social group and worldviews. In addition to the description of the social characteristics of the Ati, the article also discusses the structures and functions of their social organizations along with issues and challenges these Ati are facing as an indigenous group. We also describe their ethnic identity in relation to the larger society. The Ati of Nagpana have a strong sense of ethnic identity, their view of being Ati, rather than being Filipino, is deeply rooted in their knowledge of their origin, as well as the behavior of people in the mainstream toward them. The interplay of the different social institutions has shaped Atis' social identity and involvement. Land ownership and ethnic discrimination are among the major issues and challenges that confront the Ati of Nagpana.

Reassessment of the Mollusc Gleaning Fishery in Malalison Island, Antique Province, West Central Philippines

Gleaning activity in Malalison Island in Culasi, Antique, Philippines, was revisited and monitored monthly from May 2018 to April 2020 to compare with results from a previous investigation in 2003. Overall, slight differences were noted in the daily catch, effort, and catch rates between 2003 and 2020, whereas substantial differences were observed in the monthly and annual catches. A total of 26 species of molluscs were recorded, which was slightly lower than the previous number (= 30), dominated by the gastropods, Nerita albicilla Linnaeus, 1758, Nerita polita Linnaeus, 1758, Canarium urceus (Linnaeus, 1758), Conomurex luhuanus (Linnaeus, 1758), and Angaria delphinus (Linnaeus, 1758) which represented 79 % of the catch. The mean daily catch was 1.15 kg.gleaner-1 with catch rates ranging from 0.8 to 1.6 kg.day-1.gleaner-1, was slightly lower than the estimates in 2003 (0.9 to 2.5 kg.day-1). The observed mean monthly catch (29.6 kg) was considerably higher than the 2003 estimate (6.1 kg), which subsequently resulted in a higher estimated annual catch (1,867–2,178 kg), value (USD2,352–2,783), and gleaner income (USD392–464) in 2020 compared to estimates in 2003. Despite the changes in the catch, effort, and value estimated for the gleaning fishery in the island since 2003, locals continue to supplement their household incomes through gleaning. Nonetheless, additional investigations into the reproductive and population biology of the different species may be needed to understand further the dynamics of this fishery and its impacts on the species' ecologies.

Multiple strain analysis of Streptomyces species\xa0from Philippine marine sediments reveals intraspecies heterogeneity in antibiotic activities

The marine ecosystem has become the hotspot for finding antibiotic-producing actinomycetes across the globe. Although marine-derived actinomycetes display strain-level genomic and chemodiversity, it is unclear whether functional traits, i.e., antibiotic activity, vary in near-identical Streptomyces species. Here, we report culture-dependent isolation, antibiotic activity, phylogeny, biodiversity, abundance, and distribution of Streptomyces isolated from marine sediments across the west-central Philippines. Out of 2212 marine sediment-derived actinomycete strains isolated from 11 geographical sites, 92 strains exhibited antibacterial activities against multidrug-resistant Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. The 16S rRNA and rpoB gene sequence analyses confirmed that antibiotic-producing strains belong to the genus Streptomyces, highlighting Streptomyces parvulus as the most dominant species and three possible new species. Antibiotic-producing Streptomyces strains were highly diverse in Southern Antique, and species diversity increase with marine sediment depth. Multiple strains with near-identical 16S rRNA and rpoB gene sequences displayed varying strength of antibiotic activities. The genotyping of PKS and NRPS genes revealed that closely related antibiotic-producing strains have similar BGC domains supported by their close phylogenetic proximity. These findings collectively suggest Streptomyces' intraspecies adaptive characteristics in distinct ecological niches that resulted in outcompeting other bacteria through differential antibiotic production.

Fracture attribute and topology characteristics of a geothermal reservoir: Southern Negros, Philippines

The characterization of fracture networks using attribute and topological analyses has not been widely applied to the understanding and prediction of the secondary porosity, permeability and fluid flow characteristics of geothermal resources. We acquired fracture length, aperture, intensity and topological data from remotely sensed images and surface exposures of the Cuernos de Negros region and compared these data with well cores and thin sections from the underlying active geothermal reservoir: the Southern Negros Geothermal Field, west central Philippines. We show that the fracture attributes of the analogue and reservoir are best described by a power law distribution of fracture length and aperture intensity across six to eight orders of magnitude. This characterization of outcrop and borehole fractures validates the use of surface exposures as analogues for the Southern Negros Geothermal Field reservoir rocks at depth. An observed change in the scaling exponent in the 100–500 m length scale suggests that regional to sub-regional fracture systems scale differently from those at the meso- and macroscale, which may be a strata-bound effect or a sampling issue. Topological analyses show a dominance of Y-nodes and doubly connected branches, that indicates a high degree of fracture connectivity, which is important for effective fluid flow. Supplementary Material: Slopes, coefficient of determination and Aikake information criterion values of the cumulative frequency v. length and aperture plots of all fracture transects are available at https://doi.org/10.6084/m9.figshare.c.4960559 Thematic collection: This article is part of the The Geology of Fractured Reservoirs collection available at: https://www.lyellcollection.org/cc/the-geology-of-fractured-reservoirs

A Ranked Inventory of Commercially-important Mollusks of Panay, West Central Philippines as a Guide to Prioritize Research

A Ranked Inventory of Commercially-important Mollusks of Panay, West Central Philippines as a Guide to Prioritize Research

Cathaysian slivers in the Philippine island arc: geochronologic and geochemical evidence from sedimentary formations of the west Central Philippines

ABSTRACTThe use of geodynamic information contained in sedimentary rocks has only recently been extended into the tectonic reconstruction studies of the Philippine archipelago vis-à-vis the rest of the Southeast Asian region. We present here a comparative assessment of clastic units from the western Central Philippines, particularly from the islands of Mindoro, Panay and Palawan, and propose their likely association with sources of Cathaysian origin. Geochronological data from sedimentary formations in the study areas register U–Pb dating peaks at 185–140 Ma, 140–120 Ma and 112–90 Ma. These are similar to those observed of detrital zircons from rocks of Cathaysian origin in Taiwan and Southern China that chronicle the Yanshanian magmatic events. These same formations also record an older intercept at 1.9–1.85 Ga that likely corresponds to a regional continental orogenic episode recorded in the late Paleoproterozoic Cathaysian block. Major (e.g. Al2O3/TiO2) and trace-element (e.g. Y/Ni vs Cr/V) signatures of these sedimentary formations reflect stronger influences from granitic sources than mafic–ultramafic inputs that should otherwise be expected, considering their current oceanic island arc settings. Their La/Th and Th–Co–Zr/10 ratios also reveal continental island arc and active or passive continental margin depositional settings typical of rocks from the Palawan Microcontinental Block. New geochronological and geochemical data from the clastic rocks of northwest Mindoro, in addition to those already published for the other regions of the Palawan Microcontinental Block, provide further evidence for the amalgamation of fragments of Cathaysian origin within the Philippine island arc system.

Sociocultural Factors Influencing Adaptation Capacity of Indigenous People in Barotac Viejo, West Central Philippines

The adverse effects of climate change are now being experienced by the people without any apparent solution despite joint efforts of the world’s climate experts. Developing countries are reportedly to be hit the hardest. This means lives and livelihoods of billions of people are at stake. Indigenous people are vulnerable of this imminent danger. Determining the adaptation capacity and strategies of these indigenous people can help reduce the extent of damages that may likely occur. A study is conducted in Sitio Nagpana, Barotac Viejo, West Central Philippines to determine the level of adaptation capacity of the indigenous community and the socio-cultural factors that influence it. One hundred thirty-six households are surveyed using a self-made questionnaire as the primary tool to collect the information needed. The result show average adaptation capacity of the community. Socio-demographic factors like religion and gender show significant relationship with adaptation capacity. The rest does not show significance at all.

HABITAT HEALTH OF ILOILO RIVER - INSIGHTS FROM A STUDY ON BENTHIC COMMUNITY STRUCTURE

In west central Philippines, the monitoring of aquatic systems traditionally focused on dissolved oxygen values and biological oxygen demand, e.g. monitoring by the Environmental Monitoring Bureau around Panay Island. However, single or two factors are considered to be insufficient to assess habitat health precisely. In this paper, we investigated a benthic community and xamined their implications to habitat health of the Iloilo River. According to a prior benthic survey, warning signs pertaining to biotic, abiotic and community factors have been detected. The disturbed onditions in Iloilo River can be attributed to 3 factors; 1) its inherent topography, where bends serve as sinks for materials; 2) the lack of vigorous water exchange that promotes deposition and hinders complete flushing; and 3) the manner of utilization of the river by the local people. We thus concluded that: 1) monitoring for water parameters only is not enough to get a clear picture of habitat health; and 2) proposed that biotic components should be included for monitoring aquatic system.

Geology of northwestern Mindoro and its offshore islands: Implications for terrane accretion in west Central Philippines

In over four decades, terrane studies of Mindoro Island have evolved from one terrane- to three terrane-models. Recent mapping of northwestern Mindoro and the islands of Lubang and Ambil roughly agrees with a 1990 suggestion that the island is composed of two terranes: the Central Range and the San Jose Platform. However, in contrast to this older model, our study, which takes into consideration the petrochemical and paleontological characteristics of the units, subdivides Northwest Mindoro into the Amnay Ophiolite and the Halcon Metamorphic terranes. Southwest-verging thrust faults parallel to the currently active Manila Trench demarcate the younger Amnay Ophiolite from the latter. Components of the older Mangyan Ophiolitic Complex, formerly thought to represent a terrane distinct from the metamorphic body, are now suggested to occur as disrupted bodies enclosed within the schists of the Halcon Metamorphics. The timing of incorporation of these megaclast materials and the regional metamorphism that occurred is constrained by the deposition of the sedimentary sequences of the Late Eocene Lasala Formation. Petrochemical studies of these younger sedimentary units reveal their continent-derived character. Therefore, accretion of the Cretaceous Mangyan Ophiolitic Complex marks the collision between the Cretaceous oceanic lithosphere and mainland Asia that is considered to be the protolith of the Halcon Metamorphics. A subsequent collision occurred which led to the amalgamation of the Amnay Ophiolite suite to the metamorphosed terrane.

Socio-cultural context of fishers’ participation in coastal resources management in Anini-y, Antique in west central Philippines

The vicious cycle of poverty, overfishing and resource degradation in coastal communities in the Philippines calls for action that will address the problem of declining fish catch and degraded fish habitats. The literature has shown that an efficient and effective coastal management program can be instrumental in approaching this problem. In order to secure food and livelihood of fishers, the Southeast Asian Fisheries Development Center/Aquaculture Department collaborated with the local government of Anini-y, Antique to develop a sustainable utilization of natural marine resources through sea ranching of abalone within the Nogas Island marine protected area. Establishing a marine protected area is a means of conserving natural stocks while sea ranching is considered an effective strategy that can increase fishery resources. The two management schemes are considered as effective coastal resources management strategies. The success of a sea-ranching project is dependent not only on biophysical but also on socioeconomic factors as determinants of community participation and cooperation. A social assessment was conducted to determine the fishers’ socio-cultural characteristics, their perceptions of their coastal resources and knowledge on how to effectively manage these coastal resources. The fishers’ awareness on fishing regulations and the extent of their participation in community's coastal resources management activities were also determined. Data were collected from a household survey using a semi-structured questionnaire, focus group discussions and in-depth interviews with key informants. The fishers generally scored low in almost all aspects of their socioeconomic wellbeing. Most fishers perceived that their coastal resources were in a bad condition which they attributed to illegal and commercial fishing, increasing number of fishers and the poor enforcement of fishery regulations. However, the weighted mean scores of their knowledge on coastal resources management, awareness to fishery regulations and participation in community coastal resource management activities were average. This implied that fishers when trained and developed can become potential partners for effective coastal resources management programs.

Some Aspects of the Population Biology of the Sunset Elongate Clam Gari elongata (Lamarck 1818) (Mollusca, Pelecypoda: Psammobiidae) from the Banate Bay Area, West Central Philippines

Some Aspects of the Population Biology of the Sunset Elongate Clam Gari elongata (Lamarck 1818) (Mollusca, Pelecypoda: Psammobiidae) from the Banate Bay Area, West Central Philippines

Geochemistry of lavas from Negros Arc, west central Philippines: Insights into the contribution from the subducting slab

The Negros Arc in west central Philippines is comprised of six Pliocene to Quaternary stratovolcanoes that have erupted calc‐alkaline to slightly shoshonitic basalts to dacites. Petrographic, major and trace element, and Sr, Nd, and Pb isotope data suggest that crustal level differentiation processes have likely generated the range in composition of lavas. Several silicic lavas from the southern volcanoes have high Sr and moderate Sr/Y similar to melts presumed to be derived from subducted basaltic crust (adakites). However, these silicic lavas have low La/Yb unlike typical adakites, and have other incompatible trace element ratios (e.g., Nb/Ta, Ba/La, Pb/Ce) which are opposite to those expected of adakites. Modeling results also indicate that partial melting of the subducting Southeast Sulu Sea crust cannot satisfactorily reproduce the adakite‐like characteristics or account for the other incompatible trace element ratios. Fractionation of amphibole (± apatite) together with variable fractionation and accumulation of plagioclase have likely imparted the adakite‐like features. Trace element and isotopic variations indicate a three‐component mixing, whereby variable proportions of melted sediment and aqueous fluids derived from basaltic crust were added to the subarc MORB‐source type mantle to form the source of Negros Arc lavas. Southern Negros lavas reflect the strongest fluid contribution whereas northern Negros lavas best exhibit the sediment melt contribution.

Petrochemical Investigation of the Antique Ophiolite (Philippines): Implications on Volcanogenic Massive Sulfide and Podiform Chromitite Deposits

Abstract: The Antique ophiolite, located in Panay island (west‐central Philippines), corresponds to several tectonic slices within the suture zone between the Philippine Mobile Belt (PMB) and the North Palawan Block (NPB). It includes dismembered fragments of a basaltic sequence, dominantly pillow‐lavas with minor sheet flows, rare exposures of sheeted dikes, isotropic gabbros, subordinate layered mafic and ultramafic rock sequences and serpentinites. Most of the ophiolite units commonly occur as clasts and blocks within the serpentinites, which intrude the whole ophiolitic body, as well as, the basal conglomerate of the overlying Middle Miocene sedimentary formation.The volcanic rock sequence is characterized by chemical compositions ranging from transitional (T)‐MORB, normal (N)‐MORB and to chemistry intermediate between those of MORB and island arc basalt (IAB). The residual upper mantle sequence is harzburgitic and generally more depleted than the upper mantle underlying modern mid‐oceanic ridges. Calculations using whole‐rock and mineral compositions show that they can represent the residue of a fertile mantle source, which have undergone degrees of partial melting ranging from 9‐22.5 %. Some of the mantle samples display chondrite‐nor‐malized REE and extended multi‐element patterns suggesting enrichments in LREE, Rb, Sr and Zr, which are comparable to those found in fore‐arc peridotites from the Izu‐Bonin‐Mariana (IBM) arc system. The Antique ultramafic rocks also record relatively oxidizing mantle conditions (Δlog fO2 (FMQ)=0.9‐3.5). As a whole, the ophiolite probably represents an agglomeration of oceanic ridge and fore‐arc crust fragments, which were juxtaposed during the Miocene collision of the PMB and the NPB. The intrusion of the serpentinites might be either coeval or subsequent to the accretion of the oceanic crust onto the fore‐arc.Volcanogenic massive sulfide (VMS) deposits occur either in or near the contact between the pillow basalts and the overlying sediments or interbedded with the sediments. The morphology of the deposits, type of metals, ore texture and the nature of the host rocks suggest that the formation of the VMS bodies was similar to the accumulation of metals around and in the subsurface of hydrothermal vents observed in modern mid‐oceanic ridge and back‐arc basin rift settings. The podiform chromitites occur as pods and subordinate layers within totally serpentinized dunite in the residual upper mantle sequence. No large coherent chromitite deposit was found since the host dunitic rocks often occur as blocks within the serpentinites. It is difficult to evaluate the original geodynamic setting of the mineralized bodies since the chemistry of the host rocks were considerably modified by alteration during their tectonic emplacement. A preliminary conclusion for Antique is that the VMS is apparently associated with a primitive tholeiitic intermediate MORB‐IAB volcanic suite, the chemistry of which is close to the calculated composition of the liquid that coexisted with the podiform chromitites.

Small-scale fisheries of coral reefs and the need for community-based resource management in Malalison Island, Philippines

Fish landings in Malalison Island in the west central Philippines were monitored from February 1991 to January 1992 to determine the types of fishing gear employed, the predominant species caught, the catch per unit effort (CPUE), and the yield from the coral reefs. Fishing was monitored only during the spring tide periods, after a preliminary sampling showed no significant differences among four lunar phases. A total of 494 fishing operations was recorded. CPUE (kg per fisher h −1) by gear was 1.1 for spear guns, 1.4 for spear guns with compressor, 0.4 for set gill nets, 2.4 for drive-in gill nets, 1.2 for drift gill nets, and 0.7 for hook-and-lines. The CPUEs of Malalison gears are similar to those of other coral reef fisheries. Dominant species caught were fusiliers and surgeonfishes by gill net. surgeonfishes by spear gun, and snappers and groupers by hook-and-line. The fish yield from the Malalison coral reefs was estimated to be 5.8 t km −2 year −1, which is low, and similar to overexploited. reefs in the Philippines and elsewhere. Live coral cover averages 35% in Malalison. Reef degradation, high fishing effort, low yields, and the poverty of the fishing community suggest ‘Malthusian over-fishing’. Community based management and resource enhancement are being initiated by the SEAF-DEC Aquaculture Department to protect and sustain the fishery and improve the economy in Malalison Island.

Pb-isotopic compositions of volcanic rocks in the West and East Philippine island arcs: presence of the Dupal isotopic anomaly

The Philippine islands are situated between two oppositely dipping zones of seismicity. With the exception of a few areas, such as in the west central Philippines where the North Palawan continental terrane (NPCT) has collided with the archipelago, these seismic zones are well defined to depths of 200 km. Active volcanic chains overlay segments in each of these zones, suggesting that subduction is presently taking place both east and west of the islands. Lavas we have studied are thus divided between what has been termed the West Philippine arc and the East Philippine arc. West Philippine arc volcanic rocks which were extruded before the Philippine archipelago collided with the NPCT, or which are younger than the collision but crop out hundreds of kilometers from the collision zone, and all but one of the rocks from the East Philippine arc fall in the MORB field on 207Pb/ 204Pb versus 206Pb/ 204Pb covariation diagrams. This is surprising considering the frequency with which arc materials have 207Pb/ 204Pb ratios higher than those of MORB, the highBa/REE and Sr/REE ratios in the lavas and the possibility of sediment subduction given the small accretionary prisms. All of these rocks have high 208Pb/ 204Pb ratios with respect to Pacific and Atlantic Ocean MORB, but are similar to Indian Ocean MORB and IOB. Thus the Philippines consist of island arcs with the peculiar Dupal isotopic anomaly documented between 0° and 60°S in the southern hemisphere and particularly in the Indian Ocean region. This demonstrates that the Dupal isotopic anomaly is not restricted to the southern hemisphere, or to MORB and OIB. Post-collision rocks cropping out near the NPCT, in the West Philippine arc, have elevated 208Pb/ 204Pb and 207Pb/ 204Pb ratios that could be attributed to assimilation of the newly introduced continental crust (NPCT) by mantle-derived magmas or to the addition of a sedimentary component to mantle-derived magmas.