Maria Lourdes San Diego-McGlone

Eutrophic waters, algal bloom and fish kill in fish farming areas in Bolinao, Pangasinan, Philippines

The coastal waters of Bolinao, Pangasinan, Philippines experienced environmental changes over a 10-year period (1995-2005), the most significant effect of which was the major fish kill event in 2002 that coincided with the first reported Philippine bloom of a dinoflagellate Prorocentrum minimum. Days before the bloom, dissolved oxygen was < 2.0 mg/l in the waters that were stratified. These conditions may be linked to the uncontrolled proliferation of fish pens and cages to more than double the allowable limit of 544 units for Bolinao waters. Mariculture activities release organic matter from unconsumed feed and fecal material that accumulate in the water and sediments. In over 10 years, water quality conditions have become eutrophic with ammonia increasing by 56%, nitrite by 35%, nitrate by 90%, and phosphate by 67%. The addition of more fish pens and cages placed additional stress to this poorly flushed, shallow area that affected water quality due to changes in the water residence time.

Stoichiometric Interpretations of C:N:P Ratios in Organic Waste Materials

Stoichiometric proportionalities were derived that can be used to convert reported BOD values of organic wastes to C, N and P estimates. Ratios to approximate the dissolved inorganic fractions of N and P from reported TN and TP values were also obtained. Stoichiometric ratios were determined for various kinds of organic waste load.

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.

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.

Hypoxia in Manila Bay, Philippines during the northeast monsoon

Herein we present results from one of the first extensive bay-wide oceanographic surveys of Manila Bay, wherein 31 stations were sampled during the northeast monsoon (cold and dry season). A band of hypoxic bottom water (dissolved oxygen<2.8 mg/L) spanned the midsection of the bay from east to west. Bottom nitrate concentrations (5.7-16.8 μM; avg. 11.1 μM) and total organic carbon values in sediments (1.7-3.1%; avg. 2.4%) were high in the midsection, which coincided with the band of hypoxic bottom water. Physical processes and site-specific accumulation of organic material likely lead to hypoxic conditions in Manila Bay, even during the northeast monsoon period when the water column is relatively well mixed. The results of this study complement the previously reported widespread hypoxia that occurs during the rainy season. Thus, hypoxia may be pervasive in the bay throughout the year, although it varies in intensity and spatial extent.

Phosphorus as a driver of nitrogen limitation and sustained eutrophic conditions in Bolinao and Anda, Philippines, a mariculture-impacted tropical coastal area.

The dynamics of nitrogen (N) and phosphorus (P) was studied in mariculture areas around Bolinao and Anda, Philippines to examine its possible link to recurring algal blooms, hypoxia and fish kills. They occur despite regulation on number of fish farm structures in Bolinao to improve water quality after 2002, following a massive fish kill in the area. Based on spatiotemporal surveys, coastal waters remained eutrophic a decade after imposing regulation, primarily due to decomposition of uneaten and undigested feeds, and fish excretions. Relative to Redfield ratio (16), these materials are enriched in P, resulting in low N/P ratios (~6.6) of regenerated nutrients. Dissolved inorganic P (DIP) in the water reached 4μM during the dry season, likely exacerbated by increase in fish farm structures in Anda. DIP enrichment created an N-limited condition that is highly susceptible to sporadic algal blooms whenever N is supplied from freshwater during the wet season.

The saga of community learning: Mariculture and the Bolinao experience

The per capita fish consumption in the Philippines has not significantly changed through the years (1987–2003), but the increase in human population has created an ever-increasing demand for food fish. The Philippine Bureau of Fisheries and Aquatic Resources has responded to the food fish shortage by promoting mariculture. We support this policy within a comprehensive planning and management framework that includes siting and density of mariculture facilities. The case of Bolinao-Anda, Pangasinan is presented in this article to highlight the multi-faceted process for a successful mariculture enterprise. We use remote sensing tools to track the responses of stakeholder groups to various local legislation, mariculture-induced disasters, and scientific recommendations. Using hydrodynamic models, we assess these responses and highlight potential adjustments that may alleviate the pressure on and maintain the ecosystem health of the Bolinao-Anda coastal waters.

Comanagement for aquaculture: Suggestions from a comparative study between two major production areas of milkfish in the Philippines

ABSTRACT This study examined if, and how, comanagement is effective in controlling aquaculture industry in the municipalities of Anda and Bolinao in the province of Pangasinan, in the Philippines, the locations of two major production areas of milkfish (Chanos chanos) in the country. Institutional and community analyses conducted in these study sites revealed a unique hierarchy of resource users, as well as unique social and economic problems in aquaculture, distinct from those of capture fishery. It was also indicated that comanagement is seen as a solution for essential practices to be enforced practically and sustainably for the management of this industry. To improve aquaculture governance, it is desired that the comanagement scheme shall include not only the governments and fishers but also business operators who often have large capital and a high degree of power.

Photosynthetic and nutrient uptake physiology of Padina species in high and low nutrient waters in Bolinao, Pangasinan, Philippines

Abstract The genus Padina (Dictyotales: Dictyotaceae) are ubiquitous tropical macroalgae found in a wide range of environmental conditions, but the physiological mechanisms that allow them to thrive in different light and nutrient conditions remain unclear. This study identified Padina species found at two contrasting sites in Bolinao, Pangasinan – turbid, high-nutrient waters at Rungos, and clear, low-nutrient waters at Patar, and compared their physiological responses. The examined parameters were growth rates, photosynthetic responses to varying irradiances (P-E curves), and NO3- and NH4+ uptake kinetics. Different species were found at each site, i.e., Padina antillarum in Rungos and Padina minor in Patar. From the P-E curves, both species appeared to have “shade plant” characteristics with high α values, low compensation irradiances, and low saturation irradiances. Though P. antillarum had higher net productivity (Pmax=69.4 mg O2 gdw-1 h-1) than P. minor (Pmax=40.6 mg O2 gdw-1 h-1), their growth rates did not significantly differ. Their NO3- uptake rates were similar, while the NH4+ uptake rate of P. minor (Vmax=249.60 μmol gdw-1 h-1) was double that of P. antillarum (Vmax=104.50 μmol gdw-1 h-1) during the first 30 min of exposure to NH4+. These results suggest that each Padina species utilizes different strategies to survive in their respective habitats.

Diversity and community structure of marine microbes around the Benham Rise underwater plateau, northeastern Philippines

Microbes are central to the structuring and functioning of marine ecosystems. Given the remarkable diversity of the ocean microbiome, uncovering marine microbial taxa remains a fundamental challenge in microbial ecology. However, there has been little effort, thus far, to describe the diversity of marine microorganisms in the region of high marine biodiversity around the Philippines. Here, we present data on the taxonomic diversity of bacteria and archaea in Benham Rise, Philippines, Western Pacific Ocean, using 16S V4 rRNA gene sequencing. The major bacterial and archaeal phyla identified in the Benham Rise are Proteobacteria, Cyanobacteria, Actinobacteria, Bacteroidetes, Marinimicrobia, Thaumarchaeota and, Euryarchaeota. The upper mesopelagic layer exhibited greater microbial diversity and richness compared to surface waters. Vertical zonation of the microbial community is evident and may be attributed to physical stratification of the water column acting as a dispersal barrier. Canonical Correspondence Analysis (CCA) recapitulated previously known associations of taxa and physicochemical parameters in the environment, such as the association of oligotrophic clades with low nutrient surface water and deep water clades that have the capacity to oxidize ammonia or nitrite at the upper mesopelagic layer. These findings provide foundational information on the diversity of marine microbes in Philippine waters. Further studies are warranted to gain a more comprehensive picture of microbial diversity within the region.