Peter B. Zamora

Levels and distribution of organophosphorus flame retardants and plasticizers in fishes from Manila Bay, the Philippines.

Organophosphorus compounds (OPCs) and stable isotope ratios (δ(13)C and δ(15)N) were determined in 58 fishes belonging to 20 species collected from Manila Bay, the Philippines. OPCs were detected in most of the samples and found up to μg/g lw (lipid weight) level, suggesting their ubiquitous presence in the coastal marine environment of the Philippines. Higher levels (>1000 ng/g lw) of total OPCs were determined in yellowstriped goatfish, silver sillago, tripletail wrasse and bumpnose trevally indicates either their active uptake from ambient water or lower metabolic capacity of these species. Levels of triphenyl phosphate (TPhP) in demersal species showed a positive correlation with δ(15)N, indicating that TPhP was adsorbed onto the particle, settled down to the bottom sediment and accumulated through the benthic food web rather than the pelagic. Estimated dietary intake of OPCs in Manila Bay fishes were four to five orders of magnitude lower than the proposed reference dose (RfD).

Horizontal dinoflagellate cyst distribution, sediment characteristics and benthic flux in Manila Bay, Philippines

The lateral variation of sediment properties and associated cyst content of sediment in Manila Bay were determined and their possible role/s in the occurrences of Pyrodinium bahamense Plate var. compressum (Bohm) Steidinger, Tester et Taylor toxic blooms were assessed. Manila Bays surface sediment was determined to be silt dominated. Clay generally increased towards the coast, probably as a result of flocculation and rapid deposition upon entry of sediments from the rivers. High sand content characterized the southeastern part of the bay attributed to the greater sand inputs and relatively strong currents in this area. Bulk densities were lower in the eastern side of the bay from dilution by high organic load from sewage and urban areas. Benthic flux calculations, particularly NH3, suggest more than 50% nutrient contribution comes from sediments.

Devastation of aquifers from tsunami‐like storm surge by Supertyphoon Haiyan

The northwest Pacific Ocean is a hot spot for sea level rise and increasing frequency of stronger storms. It is where Supertyphoon Haiyan formed, the strongest storm to hit land, which provided a window into the hydrologic impacts of an extreme storm. Through detailed documentation of flood levels, groundwater table elevations and salinity, electrical resistivity, and modeling, we found that Haiyans storm surge reached 7 m above sea level along Samar Island, Philippines, which led to contamination of crucial aquifers by infiltrating seawater. A contaminated surficial aquifer will take years to recover. Groundwater in an underlying deeper aquifer saw widespread contamination immediately after the storm, but here salinity has decreased significantly after 8 months. However, this deeper aquifer remains vulnerable to seawater slowly percolating through the surficial aquifer. As warmer seas generate more powerful storms, the vulnerability of aquifers to persistent contamination from intense storm surges is a growing concern for coastal communities.

Nutrient inputs from submarine groundwater discharge on the Santiago reef flat, Bolinao, Northwestern Philippines.

Submarine groundwater discharge (SGD) on the reef flat of Bolinao, Pangasinan (Philippines) was mapped using electrical resistivity, 222Rn, and nutrient concentration measurements. Nitrate levels as high as 126 μM, or 1-2 orders of magnitude higher than ambient concentrations, were measured in some areas of the reef flat. Nutrient fluxes were higher during the wet season (May-October) than the dry season (November-April). Dissolved inorganic nitrogen (DIN=NO3+NO2+NH4) and soluble reactive phosphorus (SRP) fluxes during the wet season were 4.4 and 0.2 mmoles m(-2) d(-1), respectively. With the increase population size and anthropogenic activities in Bolinao, an enhancement of SGD-derived nitrogen levels is likely. This could lead to eutrophic conditions in the otherwise oligotrophic waters surrounding the Santiago reef flat.

Geological hazards of SW Natib Volcano, site of the Bataan Nuclear Power Plant, the Philippines

Abstract The SW sector of Mount Natib, a potentially active volcano in the Bataan volcanic arc in western Luzon, is the site of a mothballed nuclear power plant that members of the national legislature have proposed to activate. Detailed geological fieldwork was conducted to assess the capability of the volcano and to identify any volcanic hazards it might pose to the nuclear plant. The nearest eruptive centre is 5.5 km away from the plant. SW Natib Volcano is underlain by lava flows, lahar deposits and at least six pyroclastic density current (PDC) deposits, three directly underlying the nuclear reactor facility. A fault trending N30°E is aligned with the Lubao Fault, a capable fault NE of the volcanic edifice. Radon emissions at the traces of these faults are high and comparable to those at known active faults. An associated thrust fault at the nuclear site cuts through lahars up to the ground surface. The results presented here can be used for general hazard preparedness of local communities, and may assist the government to decide whether or not to recommission the nuclear power plant.

Seawater-groundwater mixing in and fluxes from coastal sediment overlying discrete fresh seepage zones: A modeling study

Submarine fresh groundwater discharging from discrete zones such as conduits overlain by thick sediment remains poorly documented and understood despite common anecdotal accounts of it. We analyzed this phenomenon by a suite of variable-density, variably-saturated groundwater flow simulations guided by field studies. The field observations included point flux and salinity measurements using seepage meters spread across the intertidal and the subtidal zones. The discretely measured seepage fluxes in the subtidal region were as high and the salinity was as fresh as those from the intertidal zone. Both fluxes and salinities varied with tides. Two-dimensional simulations of the idealized beach-ocean vertical section with discrete freshwater springs at the base showed the development of seawater recirculation cells along the edge of freshwater discharge plumes emanating from the outlets, causing mixing. Brackish water discharges at the sediment-water interface above where the plume mixes with the recirculating seawater. Sensitivity analyses showed that stronger terrestrial fresh groundwater flow increases the freshwater plume size but does not affect the mixing zone width. Tidal oscillations and a dynamic fresh groundwater flow widened the mixing zones and increased porewater flux across the sediment-water interface. Sediment thickness had a minor effect on the width of both the freshwater plume and its surrounding mixing zone. The subtidal freshwater plume and mixing zone likely represent a unique but potentially ubiquitous setting which hosts dramatic ecological and chemical gradients. Their local biogeochemical niche and coastal scale ecosystem impacts will need to be considered in investigations of coastlines.