Science Diliman 

About: Science Diliman is an academic journal. The journal publishes majorly in the area(s): Bay & Population. It has an ISSN identifier of 0115-7809. Over the lifetime, 286 publications have been published receiving 829 citations.

Participatory Monitoring and Feedback System: An Important Entry Towards Sustainable Aquaculture in Bolinao, Northern Philippines

Abstract: The aquaculture industry in Caquiputan Channel contributed P2.3M to municipal revenues in 1998. However, the uncontrolled construction of fish pens and fish cages have contributed to the deterioration of the water quality in the Caquiputan Channel. Despite monitoring of parameters (e.g. DO, salinity, and temperature), low production was implicated because of limited dissolved oxygen supply. A participatory monitoring of fish pens and fish cages was facilitated to pave the way for sustainable aquaculture. A system for monitoring and disseminating information on water quality, production and zonation of pens and cages, has been pursued to assess the situation and identify mechanisms to regulate aquaculture activities. The feedback system adopted has raised and facilitated environmental awareness, issue identification, and implementation, of solutions to some major issues. Furthermore, the results have resulted in policy reforms, as embodied in the provisions on aquaculture in the Municipal Fisheries Ordinance.

Effect of Dopant Ions on the Electrical Conductivity and Microstructure of Polyaniline (Emeraldine Salt)

Abstract: Samples of polyaniline (emeraldine salt) were prepared with different protonic acid dopants, namely, hydrochloric acid (HCl), nitric acid (HNO3), perchloric acid (HClO4), sulfuric acid (H2SO4), and hydroiodic acid (HI). Using the two-point probe method, it was found that the samples had ohmic behaviors in which high linear coefficients were found in the range 0.9686–0.9997. On the other hand, the electrical conductivities were measured using the Van der Pauw method. The undoped sample had a conductivity of 5x10–4 S/cm. The highest conductivity of 109.04 S/cm was observed for the HClO4-doped sample, while the lowest value (0.02 S/cm) was obtained for the HI-doped sample. These conductivities were compared with the computed energy gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) where it was found that they are inversely proportional to each other. Scanning electron microscopy revealed significant differences among the samples in terms of shapes and morphologies.

Focal Benthic Mollusks (Mollusca: Bivalvia and Gastropoda) of Selected Sites in Tubbataha Reef National Marine Park, Palawan, Philippines

Abstract: The study was conducted at Tubbataha Reef National Marine Park from May 6-11, 2005. Seven preestablished stations with survey sites at 5 and 10 m depth and one intertidal area were assessed using 150 m permanent belt transects. Focal benthic mollusks found one meter to the left and right of transects were identified and counted. A total of 19 species belonging to eight families were recorded, of which 15 species are univalves. In the intertidal area a total of 12 species were noted, 13 species at the shallow (5 m) and five species at deeper (10 m) areas. Species belonging to the family Tridacnidae and Trochidae were the most abundant. Among the subtidal stations, the highest number of individuals was noted at a shallow reef flat (station VI). In terms of density, the intertidal area had the highest (213,310 ind. km-2) followed by the shallow (72,870 ind. km-2) and the deep with 5,720 ind. km-2. The densities of Tridacna crocea (133,330 ind. km-2) and Hippopus hippopus (3,330 ind. km-2) at the intertidal area were found to be higher than in most other survey sites in Palawan but previous density records at the park indicate a stiff decline. On the contrary, the first record on the density of T. squamosa (950 ind. km-2) at the park is much lower compared to that from other parts of Palawan. Large and commercially valuable gastropods like, Trochus niloticus, Tectus maculatus and T. pyramis that are rarely encountered at the intertidal areas were abundant at the TRNMP. Other important species like Tridacna gigas, Charonia tritonis and Cassis cornuta were not encountered at the study sites. To fully assess the abundance of focal mollusks, permanent transects should be established in the same seven sites but in shallow reef flat of about 2 m deep, in the lagoon and in the intertidal of North and South Islets where species composition, density and growth could be monitored on an annual basis which could be used to evaluate the management effectiveness at the TRNMP.

Relative Sea Level Changes and Worsening Floods in the Western Pampanga Delta: Causes and Some Possible Mitigation Measures

Abstract: Despite declining rainfall, flooding continues to worsen around the northern end of Manila Bay. In Pampanga, flooding is enhanced by siltation of streams by sediments from the 1991 Mt. Pinatubo eruption, but the entire region has always been flood-prone, and Bulacan and Metro Manila, far from Pinatubo, also suffer worsening floods. Urbanization and deforestation are blamed, but have less impact than local sea level rise. Global warming causes the ocean surface to rise only 2 mm/yr; localized subsidence of the region from both natural and anthropogenic causes is an order of magnitude faster. Movements associated with faulting and the Pinatubo and Taal volcanoes probably are less important than the compaction of deltaic sediments under their own accumulating weights. All natural causes of subsidence are dwarfed by the contribution from excessive groundwater withdrawal, which greatly facilitates natural sediment dewatering and compaction. Several centimeters per year of documented subsidence at well sites have been corroborated by recent resurveys of elevation benchmarks established in the 1950s. In the short-term, flooding can be ameliorated by restoring original channel widths and by modifying current aquaculture practices. In the longer term, reforestation should also help by increasing infiltration and decreasing erosion and siltation. Flooding will inexorably continue in the coming century, however, both from natural compaction of delta sediments and from global sea level rise. Subsidence will continue to accelerate if the use of groundwater by the growing population is not regulated and reduced.

Contributions to the Understanding of the Bloom Dynamics of Pyrodinium bahamense var. compressum : A Toxic Red Tide Causative Organism

Abstract: Pyrodinium bahamense var. compressum has been the primary organism responsible for the toxic red tide episodes which have been recurring in Manila Bay, Philippines since 1988. The life history of the species has been elucidated through encystment-excystment studies in vitro , from which its obligatory dormancy has been demonstrated. Cyst-mapping studies have shown that this life stage of the organism occurs relatively higher in the Bataan and Cavite areas where the greater number of red tide occurrences have also been reported. A cyst-based model has been developed as an initial step in understanding the role of physical processes in the development, occurrence/recurrence, and ultimately, advancement of Pyrodinium red tides in Manila Bay. To help mitigate or prevent the negative impacts of toxic red tides, particularly in Manila Bay, regular closure of shellfish harvest in areas affected by Pyrodinium bloom should be considered, based on long term monitoring and research data sets.