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

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

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 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