Fernando P. Siringan

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).

Sources of nitrate and ammonium contamination in groundwater under developing Asian megacities

The status of nitrate (NO(3)(-)), nitrite (NO(2)(-)) and ammonium (NH(4)(+)) contamination in the water systems, and the mechanisms controlling their sources, pathways, and distributions were investigated for the Southeast Asian cities of Metro Manila, Bangkok, and Jakarta. GIS-based monitoring and dual isotope approach (nitrate delta(15)N and delta(18)O) suggested that human waste via severe sewer leakage was the major source of nutrient contaminants in Metro Manila and Jakarta urban areas. Furthermore, the characteristics of the nutrient contamination differed depending on the agricultural land use pattern in the suburban areas: high nitrate contamination was observed in Jakarta (dry fields), and relatively lower nutrients consisting mainly of ammonium were detected in Bangkok (paddy fields). The exponential increase in NO(3)(-)-delta(15)N along with the NO(3)(-) reduction and clear delta(18)O/delta(15)N slopes of NO(3)(-) ( approximately 0.5) indicated the occurrence of denitrification. An anoxic subsurface system associated with the natural geological setting (e.g., the old tidal plain at Bangkok) and artificial pavement coverage served to buffer NO(3)(-) contamination via active denitrification and reduced nitrification. Our results showed that NO(3)(-) and NH(4)(+) contamination of the aquifers in Metro Manila, Bangkok, and Jakarta was not excessive, suggesting low risk of drinking groundwater to human health, at present. However, the increased nitrogen load and increased per capita gross domestic product (GDP) in these developing cities may increase this contamination in the very near future. Continuous monitoring and management of the groundwater system is needed to minimize groundwater pollution in these areas, and this information should be shared among adjacent countries with similar geographic and cultural settings.

Holocene Evolution of the East Texas Coast and Inner Continental Shelf: Along-Strike Variability in Coastal Retreat Rates

ABSTRACT The low gradient east Texas coast and inner-continental shelf, from Sabine Lake at the Texas-Louisiana border to the western end of Galveston Island, experienced extreme along-strike variations in rates of Holocene coastal retreat. Around 7.7 ka a barrier shoreline was located approximately 55 km offshore. Toward the western end of Galveston Island, the shoreline retreated 55 km, occupying a position on the lagoon side of the Island by about 5.3 ka. Toward the Texas-Louisiana border, the shoreline retreated more gradually, occupying a position seaward of Sabine Bank by 5.3 ka. Between 4.7 ka and 2.8 ka the shoreline at Sabine Bank retreated 30 km, while Galveston Island prograded seaward. Bolivar Peninsula began to accrete around 1.5 ka. Heald and Sabine banks, located on the inner continental shelf above terraced fluvial deposits of the Trinity-Sabine incised valley, are the only preserved remnants of these former shoreline positions. Fluctuating rates of sea-level rise were not the forcing mechanism behind episodes of rapid shoreline retreat because these events were localized. Rather, along-strike variations in the rate of transgression were caused by the variable inner-shelf gradients, which increase towards the west, and the orientation of the Sabine incised valley and associated terraced fluvial deposits, which trend northeast-southwest (parallel to shore). As shorelines retreated over fluvial deposits, these served as local sand sources that enabled barrier islands to persist Figure 1. Map of the east Texas inner shelf showing locations of Sabine, Heald, and Shepard banks. Paleotopographic map of the Pleistocene surface (thin contours; Siringan 1993) delineates the Trinity-Sabine incised valley, which formed during the last lowstand of sea level (Thomas and Anderson 1994). Bathymetric contours are shown as thick lines with bold numbers. Dots are core locations. End_Page 405------------------------ offshore, out of equilibrium with sea level. Once these sand sources became depleted, and/or sea level reached some critical threshold, barrier shorelines became stranded offshore as banks, and new shorelines formed landward. The geologic setting of coastal areas, specifically antecedent topography, plays a primary role in controlling coastal evolution. To accurately forecast long-term (centennial to millennial) coastal evolution, it is essential that impacts associated with variations in the underlying geology of coastal areas be incorporated into coastal forecasting models.

Determination of preservative and antimicrobial compounds in fish from Manila Bay, Philippines using ultra high performance liquid chromatography tandem mass spectrometry, and assessment of human dietary exposure

Ultra high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) determination of four paraben preservatives (methyl, ethyl, propyl and butyl) and two antimicrobial agents (triclosan and triclocarban) belonging to personal care products (PCPs) in 20 species of fish from Manila Bay (Philippines) was performed. Detection of PCPs with greater frequency indicates the ubiquitous contamination of Manila Bay. Concentrations of total paraben were one order of magnitude higher than the antimicrobials in almost all fish, except in Stolephorus indicus and Leiognathus equulus. A positive correlation was observed between parabens concentration and fish length (r = 0.31-0.49; p<0.05 to <0.001) and fish weight (r = 0.28-0.49; p<0.05 to <0.001), but not for the antimicrobials. The estimated dietary exposure values of the four parabens in the Philippines through fish is four orders of magnitude lower than the acceptable daily intake (ADI) of 10mg/kg/day, but the values of antimicrobials are just half of the ADI of TCS. To our knowledge, this is the first report of PCPs contamination in fish from Philippines.

Late Quaternary sedimentation and high-resolution sequence stratigraphy of the east Texas shelf

Abstract An ongoing study utilizes outcrop-scale seismic data and lithofacies data from cores and platform borings collected from the east Texas continental shelf to test assumptions and models that relate sedimentary facies patterns and sequence stratigraphy. The current data base consists of nearly 15 000 km of high-resolution seismic data and lithological data from hundreds of sediment cores and platform borings. The Texas shelf is ideally suited for this work because sediment supply during the Pleistocene was high enough to keep pace with the relatively rapid rise and fall in sea level, thus producing sequences that can be imaged on high-resolution seismic records. Furthermore, sediment supply, shelf gradient, and the degree of diapirism and faulting vary across the shelf, so the relative roles of these agents in controlling the overall packaging of facies into systems tracts can be evaluated. Strong contrasts exist between low-sediment-supply (Trinity/Sabine) and high-sediment-supply (Brazos and Colorado) fluvial systems and their associated systems tracts. The predominant difference is that sediment delivered to the shelf by the Trinity/Sabine fluvial system was, for the most part, deposited within the incised fluvial valleys. Only during lowstands did the Trinity/Sabine system deliver sediment directly to shelf-margin deltas and slope minibasins. Reincision, associated with fifth-order eustatic fluctuations, flushes the valley of sediments deposited during the previous transgression and highstand, thus large quantities of sediment are delivered from this valley system during lowstands. Transgressive shelf sand bodies occur adjacent to the Trinity and Sabine incised valleys and are scattered widely across the shelf. Backstepping parasequences, the product of the episodic nature of glacial eustatic sea-level rise, characterize the incised valley fill. The highstand systems tract is thin to absent in interfluve areas. The Brazos and Colorado rivers have much larger sediment supplies than the Trinity and Sabine rivers. They have filled their incised valleys with fluvial deposits and abandoned them to occupy several more shallow valleys. The result of this fluvial avulsion has been the sequestering of a significant part of the sediments delivered by these rivers to fluvial valleys on the shelf. Both the Colorado and Brazos rivers constructed large shelf-margin deltas during the lowstand, but these deltas differ in terms of their overall morphology and sediment facies. The ancient Colorado delta is sandy and it directly sourced two slope fans during the maximum lowstand. The Brazos shelf-margin delta consists mainly of mud and there is little evidence of significant bypass during the lowstand. During initial transgression, the Brazos/Colorado shelf-margin deltas backstepped onto the outer shelf. Rapid transgression and associated erosion removed the delta-plain beds. Continued transgression led to decapitation of sandy fluvial and deltaic facies, reworking the sands into widespread shelf sand bodies, and further backstepping of the deltas. During the previous highstand, the Brazos and Colorado rivers constructed fluvial-dominated deltas on the shelf. The shelf-margin deltas of the area show a complex pattern of progradation and aggradation that varies from one delta to the next. This complexity is due predominantly to the different response of systems with different sediment supplies to fifth-order eustatic fluctuations. Before we understood these autocyclic effects, attempts at relating seismic stratigraphic changes to the oxygen isotope curve, our proxy for sea-level change, were unsuccessful.

Contamination and bioaccumulation of benzotriazole ultraviolet stabilizers in fish from Manila Bay, the Philippines using an ultra-fast liquid chromatography–tandem mass spectrometry

Benzotriazole ultraviolet stabilizers (BUVSs) used in plastic products, building materials and personal hygiene products were analyzed in fishes collected from Manila Bay, the Philippines. BUVSs were detected at ng g⁻¹ level in all the fish samples, indicating their ubiquitous contamination in coastal waters. Among the targeted eight BUVSs, UV-328 was predominantly found with a mean concentration of 34.2 ng g⁻¹ lipid weight, implying large scale production and use of this compound in the Philippines. High concentrations of ∑BUVSs were found in bumpnose trevally (Carangoides hedlandensis), bluetail mullet (adult) (Valamugil buchanani), common ponyfish (Leiognathus equulus) and coral grouper (adult) (Epinephelus corallicola) indicating their active uptake and/or lower metabolic capacity to eliminate BUVSs. Among BUVSs, UV-P showed significant positive relationship (p<0.05) between concentration and fish length (r=0.29) and fish weight (r=0.31). Levels of UV-P in demersal species had positive correlation with δ¹⁵N, indicating that possibile sink of UV-P is bottom sediment in the bay, and ultimately accumulate through benthic food web rather than pelagic food web. To our knowledge, this is the first study on BUVSs distribution in fish from developing countries.

Modern Shoreface and Inner-Shelf Storm Deposits Off the East Texas Coast, Gulf of Mexico

ABSTRACT The modern shoreface and inner-shelf sediments off the east Texas coast on the Gulf of Mexico were examined using sediment cores and high-resolution seismic data. Low sediment input and low effective accommodation space resulted in the overall thinness of the modern marine sediment cover in the region. Erosion on the inner shelf during historic ( 100 yr) times produced patches of sand in a predominantly mud-dominated environment. Storm beds are scarce on the inner shelf. The shoreface succession off Galveston Island is characterized by offshore-directed crosscutting storm channels of varying sizes. The existence of these channels and the relatively high frequency of storms and hurricanes that have affected the region during historical imes are inconsistent with the paucity of storm deposits on the inner shelf. The offshore-directed channelized flows may have been prevented from going beyond the shoreface by strong along-shelf storm currents that impinged on the shoreface. In contrast to the storm record on the east Texas shelf, the central Texas shelf shows a greater frequency of and more laterally persistent storm sand beds due to greater effective accommodation space and higher sediment supply there.

Effects of environmental regulations on heavy metal pollution decline in core sediments from Manila Bay

We investigated the high-resolution heavy metal pollution history of Manila Bay using heavy metal concentrations and Pb isotope ratios together with (210)Pb dating to find out the effects of environmental regulations after the 1990 s. Our results suggested that the rate of decline in heavy metal pollution increased dramatically from the end of the 1990 s due to stricter environmental regulations, Administrative Order No. 42, being enforced by the Philippines government. The presented data and methodology should form the basis for future monitoring, leading to pollution control, and to the generation of preventive measures at the pollution source for the maintenance of environmental quality in the coastal metropolitan city of Manila. Although this is the first report of a reduction in pollution in Asian developing country, our results suggest that we can expect to find similar signs of pollution decline in other parts of the world as well.

Groundwater Discharge as an Important Land-Sea Pathway into Manila Bay, Philippines

Abstract A multidisciplinary approach was taken to assess the potential importance of groundwater seepage to nutrient inputs into Manila Bay, Philippines. Three lines of seepage meters were installed in transects along the coast at Mariveles, Bataan Province, during the period 8–10 January 2005. The overall average seepage flux was 5.1 ± 5.4 cm d−1 (n = 73) with a range of 0–26 cm d−1 and a calculated integrated shoreline flux of 12.4 m3 m−1 d−1. Additional methodologies employed included automatic seepage meters, resistivity measurements, sampling for nutrient analyses in both seepage meters and ambient seawater, and use of natural radon as a groundwater tracer. Seepage meter and tracer results provided consistent results of estimates of submarine groundwater discharge into Manila Bay. Many lines of evidence suggest that seepage fluxes are not steady state but are modulated by the tides. Resistivity profiles show that the saline-freshwater interface moves on a tidal timescale, consistent with the observed drop in salinity of the seepage waters as low tide approaches. Our results show that dissolved inorganic nitrogen (DIN) fluxes via submarine groundwater discharge are comparable in magnitude to DIN fluxes from each of the two major rivers that drain into Manila Bay.

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.