Surface nutrient regime and bottom hypoxia in Manila Bay during the southwest monsoon

We e amined the surface nutrient regime and hypo ia in Manila Bay, Philippines, during the southwest monsoon along a transect from off Limay, Bataan Peninsula, to Metro Ma nila. The water column showed stratification, with warm, less saline water in the top 10 meters overlying cold, saline bottom water. Hypo ia was present in the bottom waters along the entire transect, and ano ic conditions were observed off Manila. Ammonium concentrations ranged from 6.7 to 40.2 µM, e ceeding those of nitrate and nitrite, both of which were nearly depleted at almost all stations e cept off-Manila, with levels below 0.1 µM. Phosphate varied from 0.1 to 1.9 µM, resulting in a stoichiometrically nitrogen-rich condition at the surface, with N:P ratios ranging from 17.1 to 149.7 and an average of 37.4. This is in contrast to the phosphate-rich con ditions reported during the northeast monsoon period. A plume with high nutrient concentrations and high chlorophyll a was observed off Manila, indicating freshwater inflow from sewage and the Pasig River. Diatoms, including the Skeletonema costatum comple and Chaetoceros spp., were abundant, and these eutrophic conditions likely favored the occurrence of green Noctiluca, while it was not observed during our study.departmental bulletin pape

The primary productivity in the South China Sea, Area III: Western Philippines

In this paper the relative concentrations and vertical distributions of primary production were investigated off Western Philippines of the South China Sea during tradewinds from April 15 to May 11, 1998. Primary productivity measurements were conducted using conventional "light-and-dark bottle" oxygen method. The net primary production estimates at ten (10) different stations established between 19° 59.2'N, 119° 58.7'E and 11° 13.5'N, 118° 03.1'E ranged from 0.10 ~ 1.53 g C m-2 d1. The result suggests that the present net production estimates in the area is remarkably higher than the estimates from other parts of the South China Sea (viz., northern coastal waters off Taiwan and southwestern parts of the SCS which included marine waters of Thailand, Indonesia and Malaysia). The highest primary production occurred at the upper 60-m well-mixed layer of station 1 in the northwestern most part of the area. Results have shown that some other hydrographic and chemical parameters (viz., temperature, salinity, light and fluorescence) greatly complicate and may not coherent with the analyses of relative distribution and abundance of primary production in the area

Spatio-Temporal Distribution and Abundance of Phytoplankton in Manila Bay

Understanding the dynamics and production of phytoplankton may contribute to the elucidation of the status of fishery resources and may be the key for better fisheries management since phytoplankton is at the base of the food chain. The changes and succession of phytoplankton community structure in Manila Bay was studied by conducting hydrobiological survey every other month from January 2012 to November 2015. It was determined from this study that diatoms dominated the phytoplankton composition all throughout the survey period and the total phytoplankton density was generally highest during southwest monsoons. Dinoflagellates and cyanobacteria, on the other hand, were relatively most dense during tradewinds. Although causative species for harmful algal blooms and fish kills were present, only the bloom of red Noctiluca scintillans was observed in January 2014 albeit no harmful implication to consumers was reported. Phytoplankton typically converged in the coasts of the bay, particularly at the eastern portion, but it is noteworthy to say that the sporadic pattern seen maybe attributed to the presence of their predators. The dramatic drop in the phytoplankton densities seem to coincide with the spawning of Sardinella fimbriata and Sardinella gibbosa

Abundance and distribution of zooplankton in the South China Sea, Area III: Western Philippines

A survey on the zooplankton in the waters of western Philippines was carried out from April 18 to May 9, 1998. The estimate of zooplankton biomass ranged from 0.92 mg/m3 to 20.85 mg/m3 with a mean of 5.70 mg/m3. Maximum and minimum densities of zooplankton recorded were 4683/m3 in station 16 and 446/m3 in station 5, respectively. The zooplankton communities were comprised of 37 different categories of animal groups. Copepods were the most dominant group in zooplankton communities at all stations but their abundance varied from 5% to 43% of the total zooplankton

Spatio-Temporal Distribution of Ichthyoplankton in Manila Bay in Relation to Oceanographic Conditions

Manila Bay faces serious problems today such as pollution, coastal area reclamation and infrastructure, overfishing, and other activities that worsen the present condition of the bay. It is considered as one of the major fishing grounds in the Philippines. Fish eggs and larvae collection was carried out to determine their distribution, abundance, and composition in the bay. Eight established sampling stations were placed throughout the bay with an average distance of 5-6 nautical miles apart and sampled every other month on a monsoonal basis. Bongo net (360 microns mesh size, 1.5 meters in length, and a diameter of 50-centimeter mouth opening) with attached calibrated flowmeter was used in collecting fish larvae. Physical (salinity, temperature,), chemical (nitrite, nitrate, phosphate, silicate, dissolved oxygen), and biological (phytoplankton, zooplankton) parameters were also carefully studied to be able to explain such uncommon event within the bay. In spite of the current status and worsening condition of water quality of the bay, high abundances of fish eggs and larvae were consistently observed during the northeast monsoon surveys (March) from 2012 to 2015. A total of 3,008 individuals were identified belonging to 34 fish families. The highest fish egg density was observed during March 2013 with 1,550 ind./100m3, followed by March 2012 and 2015 with 1,484 ind./100m3 and 1,182 ind./100m3, respectively. An abundance of fish larvae was observed during March 2015 with 414 ind./100m3, followed by March 2012 (329 ind./100m3), and March 2014 (311 ind./100m3). The lowest density observed was in September 2012 with a density of 132 ind/100m3 fish eggs and 46 ind/100m3 fish larvae. The results were consistent that most fish eggs aggregate in the middle part of the bay especially in Stations 4 and 2 from 2012-2015. For fish larvae, they were consistently found in the eastern part of the bay (stations 6, 8, and 7) throughout the duration of the study, it was also the areas where high concentrations of phytoplankton, zooplankton, and nutrients were observed. A high abundance of fish eggs and fish larvae was observed during northeast monsoon than southwest monsoon. In addition, fish larvae family was dominated by small pelagic fish such as sardines, slipmouths, and mullets. The most dominant fish families found were Clupeidae, followed Leiognathidae, and Nemipteridae. Sillaginidae and Mugilidae were also included in the top five abundant families that occur during every sampling period were

Profile of Salinity, Temperature, Heavy Metal (Pb, Cd, Hg) and Sediment Hydrogen Sulfide Concentration of Manila Bay, Philippines from 2012 to 2015

The physical parameters of seawater are important determinants of water quality. Heavy metals are components that are naturally present in a considerable amount in the ocean but are observed to be rising above the allowable level due to pollution outputs of industrialization. Heavy metal contamination is among the environmental pollution problems that the world faces. Additionally, hydrogen sulfide (H2S) is also a toxic compound that accumulates in the ocean floor posing threat to the marine organisms when present in high concentrations. The objective of this study is to document the distribution of temperature and salinity in the water column, heavy metals (Pb, Cd, Hg) and sediment H2S in Manila Bay from 2012 to 2015. Stratification in the bay was generally a factor of salinity and less of temperature. Stratification due to salinity was consistently observed in September with the halocline occurring around 10 m to 15 m. Most of the time, the bay had evenly distributed temperatures, but the slightly higher temperatures were usually recorded near the coast. Inverse trends were observed for the salinity and temperature of the bay. Pb, Cd, and Hg concentrations in the bay occasionally exceeded the permissible limits especially the lead concentration in January 2013 (ave: 809.81 µg/L), March 2013 (ave: 1102.88 µg/L) and November 2015 (1507.50 µg/L). Cd and Hg concentrations were generally below the permissible limit and the reported limit of analysis. H2S concentration ranged from < 4 mg/kg to 9.99 mg/kg for all the survey months. Distribution was higher in the northwestern part and southeastern areas of the bay

Spatio-Temporal Variability of Hypoxia and Eutrophication in Manila Bay During the Northeast and Southwest Monsoons from 2012 to 2015

Manila Bay is a major source of livelihood for the fishermen living around the area. The occurrence of hypoxia, a state where dissolved oxygen (DO) is not enough to support marine life, poses a serious threat to the bay and consequently to its fisheries sector. This study documents the variation of hypoxia throughout the bay for a sampling period of four years, from January 2012 to November 2015, with a monthly interval each survey. A total of 24 field surveys on 16 designated sampling stations, at varying depths, were conducted. Results show that hypoxia was present all year round but was more severe during the wet season (July, September, November) compared to the dry season. The averages of bay-wide DO concentration ranged from 3.42 to 7.63mg/l during the 4-year survey. Low DO concentrations were associated with high concentrations of nutrients, particularly nitrate. Nitrate spiked to a 44.6 µM concentration while bay-wide DO concentration dropped to as low as 0.01 mg/l in the wet season. An occurrence of hypoxia along the coasts, transitioning from western, northern and eastern areas, was observed as a common trend for all surveys. However, DO concentrations in areas near the coast, in depths around 5m to 15m, and in the deeper areas near the mouth of the bay, from around 10m to 35m depths were noted to be lower. In conclusion, hypoxia has been occurring year-round in Manila Bay with varying intensity but more prominent during the wet season

Spatio-Temporal Variability of Zooplankton Distribution and Abundance in Manila Bay from 2013-2015

The study characterized the spatiotemporal variations in composition, abundance, and diversity of zooplankton community in Manila Bay. Zooplankton samples were collected every two months within three years from 2013 to 2015. The zooplankton composition of Manila Bay includes 29, 52, and 50 taxa in 2013, 2014, and 2015, respectively belonging to the following major groups: Copepoda, Decapoda, Cladocera, Chordata, Annelida, Mollusca, Chaetognatha, Ciliophora, Foraminifera, Echinodermata, and Chromista. Copepod nauplii consistently dominated the zooplankton community in the bay from 2013 to 2015 followed by Tintinnids, Oithona spp., Euterpina acutifrons, and Paracalanus spp. The highest concentration of zooplankton was specifically observed in the south western side near the mouth of the bay (Station 4) in July 2015. In 2014, the highest recorded zooplankton density was in the month of November in the eastern side (Station 10). In general, relatively high diversities of zooplankton community were recorded in many months in 2015 as compared to 2013 and 2014 although the highest recorded diversity occurred in March 2014. Redundancy Analysis revealed salinity, temperature, dissolved oxygen, chlorophyll a, PO4, SiO, and NO3 to have a strong correlation with the zooplankton abundances and distribution

Vulnerability of tropical shellfishes against PSP contamination during bloom of Pyrodinium bahamense var. compressum

Accumulation of paralytic shellfish poisoning (PSP) toxins in representative shellfish samples of epifaunal, partially exposed benthic and infaunal nature in association with the toxic dinoflagellate, Pyrodinium bahamense var. compressum was investigated. Shellfish and seawater samples were collected during the last quarter of 2007 and in 2008 in Sorsogon Bay, Philippines. All tissue samples were then analyzed for PSP toxins while cell density of P. bahamense var. compressum was determined in water samples. Results showed that epifaunal, partially-exposed benthic, and infaunal shellfish have remarkable differences in terms of PSP toxin accumulation. Epifaunal shellfish can accumulate PSP toxin of more than a thousand times compared to infaunal shellfish with the latter negative for PSP toxin during P. bahamense var. compressum bloom.Proceedings of the Horiba International Conference "New Direction of Ocean Research in the Western Pacific" : Past, Present and Future of UNESCO/IOC/WESTPAC Activity for 50 years and the JSPS Project "Coastal Marine Science"Section I: Research Articles/Harmful microalga

Vulnerability of tropical shellfishes against PSP contamination during bloom of Pyrodinium bahamense var. compressum

Accumulation of paralytic shellfish poisoning (PSP) toxins in representative shellfish samples of epifaunal, partially exposed benthic and infaunal nature in association with the toxic dinoflagellate, Pyrodinium bahamense var. compressum was investigated. Shellfish and seawater samples were collected during the last quarter of 2007 and in 2008 in Sorsogon Bay, Philippines. All tissue samples were then analyzed for PSP toxins while cell density of P. bahamense var. compressum was determined in water samples. Results showed that epifaunal, partially-exposed benthic, and infaunal shellfish have remarkable differences in terms of PSP toxin accumulation. Epifaunal shellfish can accumulate PSP toxin of more than a thousand times compared to infaunal shellfish with the latter negative for PSP toxin during P. bahamense var. compressum bloom.Proceedings of the Horiba International Conference "New Direction of Ocean Research in the Western Pacific" : Past, Present and Future of UNESCO/IOC/WESTPAC Activity for 50 years and the JSPS Project "Coastal Marine Science"Section I: Research Articles/Harmful microalga