National Committee on Marine Sciences (NCMS)
Permanent URI for this communityhttps://repository.unesco.gov.ph/handle/123456789/6
Browse
6 results
Search Results
- Insights into the environmental conditions contributing to variability in the larval recruitment of the tropical sardine Sardinella lemuruPata, Patrick R.; Yñiguez, Aletta T.; Deauna, Josephine Dianne L.; De Guzman, Asuncion B.; Jimenez, Cesaria R.; Rosario, Roselle T. Borja-Del; Villanoy, Cesar L. (Elsevier, 2021-07)The small pelagic fishery in the southern Philippines is one of the largest contributors to fisheries production in the country, and is dominated by the Bali sardine Sardinella lemuru. This species is a year-round spawner that has its peak spawning period during the northeast monsoon (NEM) months of November to February. However, there is still limited information on the conditions that affect this species’ survival during its early life history stages. Here, we attempt to discern the importance of temperature, prey density and advection on sardine larvae. The larvae were represented as passive particles that were released in known spawning grounds to simulate dispersal. The conditions the larvae experienced, namely, temperature and estimated prey density based on satellite chlorophyll-a values were recorded at each time step until the estimated recruitment age of 60 days. The temporal and spatial averaged conditions of recruited sardines showed that sardines spawned during the NEM months experienced higher chlorophyll-a, lower (more optimal) sea surface temperature, albeit higher advective loss, than sardines spawned during other months. Comparisons between years showed that during higher reported catch years, sardine larvae experienced lower temperatures and higher retention nearshore. Our results emphasize that sardine stock management efforts need to recognize the contribution of the temporally variable sardine environment to patterns in sardine recruitment and consequently in catches.The authors would like to thank Dr. Wilfredo Campos, Luke Felix, Dr. Rio Naguit, Denmark Recamara, and the Research for Sardines Volunteer Program (RSVP) volunteers for sharing sardine fisheries data; Arjay Cayetano for helping start the model used; and Iris Salud Bollozos for useful insights on larval ecology. This study was fully funded by the Department of Science and Technology–Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development (DOSTPCAARRD) under the program, “Development of robust tools for managing sardine fisheries in the Philippines: Zamboanga Upwelling Bohol Sea System Program.” The authors declare no conflict of interest.
- Connections and clustering of Paralytic Shellfish Toxin events among coastal embayments in an archipelago partly mediated by advectionPunongbayan, Andalus T.; Wang, Ysabel D.; Villanoy, Cesar L.; Yñiguez, Aletta T. (Elsevier, 2022-01)The potential for advection to influence harmful algal bloom (HAB) spread in adjacent embayments and islands has not been investigated in the Philippines as previous studies have focused on HAB dynamics within specific embayments. Advection of HABs may be relevant in the Samar-Leyte region where adjacent sites are subject to recurrent blooms of Pyrodinium bahamense. We used different analyses to extract the potential role of advection in blooms in the region. First, we used Bayesian and information theoretic approaches applied to historical data on shellfish bans to quantify spatial dependencies in HAB occurrences between sites. Then, to determine whether such dependencies are related to circulation patterns in the region, we analyzed connectivity using a hydrodynamic model coupled with a conservative tracer-based HAB model. The Bayesian network showed that in 7 out of 11 sites, the probability of a shellfish ban depended on the state of an adjacent site. Site pairs with direct dependence relations also shared relatively high similarity in HAB occurrences over time. In the modelled network, bans tend to occur sequentially, spreading from a few sites with relatively high probabilities for ban events. A subset of sites (sources) were found to be informative of future HAB event probabilities in other sites (destinations) over time lags that are generally longer the farther the destination. Modelled surface advection showed high connectivity strengths between sources and destinations associated with circulation features, e.g., an anticyclonic current in Leyte, wind-driven coastal current in western Samar, and tidally-driven flow in the shallow embayments in southwest Samar. High connectivities were correlated with direct dependence relations in the Bayesian network. Connectivity explained up to about 1/3 of the variance in statistical dependencies between ban signals. Our results show that Paralytic Shellfish Toxin events within this region can be due to advection of blooms originating from nearby areas rather than localized cyst dynamics within an embayment. Particular sites were also identified as potential indicator sites within spatial clusters for monitoring since they are typically where blooms originate and spread from.
- Structure of potential upwelling areas in the PhilippinesUdarbe-Walker, Maria Jayvee B.; Villanoy, Cesar L. (Elsevier BV, 2001-06)The three-dimensional structure of two potential mesoscale upwelling areas that are located in the external waters of the Philippine archipelago (i.e. northwest of Luzon and east of Mindanao) were constructed by analysis of historical data. A unique characteristic of both upwelling sites is that they can be identified by their anomalously cold subsurface temperatures rather than sea surface temperature distributions. As such, they cannot be observed in sea surface temperature fields derived by satellite imagery. The data used in the analysis were obtained from the National Oceanographic Data Center hydrographic database. Objective analysis was performed to produce monthly temperature fields at several standard depths within the upper 500 m of the region 0–30°N and 100–140°E with a horizontal grid resolution of 0.5°. The extent and timing of these upwelling areas are described. A review of existing hypothesis on the mechanisms for their evolution and seasonal modulation are presented. The change in heat content during the upwelling season is greater than 300 W m−2 in both areas. Based on the excursion of isotherms, vertical velocities of 83 cm day−1 and 26 cm day−1 were obtained for upwelling northwest of Luzon and east of Mindanao, respectively.
- Juvenile scleractinian assemblage and its association with adults and benthos at shallow and upper mesophotic depths in fringing and atoll reefs in the PhilippinesAlbelda, Ritzelle L.; Cabaitan, Patrick C.; Sinniger, Frederic P.; Dumalagan, Edwin Jr; Quimpo, Timothy Joseph R.; Olavides, Ronald Dionnie D.; Munar, Jeffrey C.; Villanoy, Cesar L.; Siringan, Fernando (Elsevier B.V, 2020-10-15)The juvenile stage is a critical part of a scleractinian’s life history as it is when they are highly vulnerable to various post-settlement mortality processes, which influence the structure of adult scleractinian assemblages. Although numerous studies have been done to understand dynamics of juvenile assemblages at shallow water reefs (SWRs), similar studies on deeper and less explored reefs, such as mesophotic coral ecosystems (MCEs) remain limited. Using diver-based photo-quadrat method, we aimed to examine how juvenile scleractinian assemblages vary from SWRs (shallow: 3 to 10 m and middle: 10 to 20 m) to upper MCEs (deep: 30 to 40 m) in the fringing and atoll reefs in the Apo Reef Natural Park, Philippines. We also aimed to understand the potential association of juvenile scleractinian densities with adult scleractinian densities and benthic cover. A total of 12 families were recorded for both juveniles and adults with Poritidae being the most abundant, followed by Pocilloporidae and Acroporidae (and Merulinidae for juveniles only). Juvenile densities (ranging from 14 to 36 individuals/m2) varied among depth zone and reef type interactions and had a bimodal distribution, with the middle zone having the lowest density compared to the shallow and deep zones. Juvenile densities were correlated to benthic cover, particularly to high algal cover in the middle zone and availability of bare hard substrate in the shallow zone. Adult densities were also correlated with juvenile densities, but not commonly in the middle zone, emphasizing that it is only one of the many variables that contribute to juvenile assemblages. This study is the first to document juvenile scleractinian assemblages, how they vary from SWRs to MCEs in the Philippines and the Coral Triangle, and demonstrates the importance of benthos and adult brood stock in shaping juvenile scleractinian assemblages across depth zones.
- Emerging pharmaceutical contaminants in key aquatic environments of the PhilippinesMariano, Shyrill Mae F.; Angeles, Luisa F.; Aga, Diana S.; Villanoy, Cesar L.; Jaraula, Caroline Marie B. (Frontiers Media SA, 2023-09-13)Pharmaceuticals in natural waters are considered emerging pollutants due to their low concentrations and the negative effects they pose to the environment. Common sources of such pollutants include untreated wastewater from hospitals, residential, industrial, and agricultural sources. Many wastewater treatment methods only remove a subset of all pharmaceuticals from the wastewater; remaining pharmaceuticals are discharged into natural waters, and ultimately drain into coastal areas. Regions without proper wastewater treatment are especially susceptible to such contamination. This study deals with the distribution, sources, and seasonal variability of pharmaceuticals in key aquatic systems in the Philippines. Two watershed continuums (Davao Gulf, Davao City; Macajalar Bay, Cagayan de Oro City); two tourist areas (Boracay Island, Aklan; Mabini, Batangas); and one pristine atoll (Tubbataha Reefs, Palawan)—all with varied prevailing human population pressures—were studied. Samples of hospital wastewater as well as groundwater, surface and bottom water samples from rivers and coastal seas collected during dry and wet seasons were analyzed using solid-phase extraction and liquid chromatography-tandem mass spectrometry. Thirty-four target pharmaceutical residues and antibiotics were extracted and quantified. Acetaminophen was detected at concentrations of up to 289.17 ppb in freshwater samples, and at concentrations of up to 253.39 ppb in seawater samples. Ubiquitous to all the sites was caffeine, reaching 1848.57 ppb. Sulfamethazine, a commonly used veterinary antibiotic, was detected at 764.91 ppb in a river site in Cagayan de Oro. Untreated hospital wastewater contained metformin, iopamidol, sulfamethoxazole, acetylsulfamethoxazole, ciprofloxacin, and azithromycin, but these pharmaceuticals were not detected in other river and coastal waters. Samples collected during the dry season exhibited higher concentrations than those from the wet season, which appears to be related to increase in transient populations from tourism activities as well as dilution. The presence of pharmaceutical residues and antibiotics in these areas and the potential impact on the environment indicate the need for stricter wastewater management measures, particularly in communities located near water bodies. As the results of this study show, such measures might be most beneficial and effective if imposed during dry season and in areas open to tourism.We thank the crew and researchers aboard M/Y Panata expedition PA0421 to Tubbataha in October 2019 and cruise to Boracay December 2019. Our gratitude to Mary Antoinette Limen, Mishel Valery Rañada, Gio Ferson Bautista, and Ernest Guiller Pineda for helping us in the field, and to Lahiruni Halwatura for assisting in the creation of a standard calibration curve for saltwater.
- Status of giant clam resources of the PhilippinesJuinio, Marie Antoinette R.; Meñez, Lambert Anthony B.; Villanoy, Cesar L.; Gomez, Edgardo D. (Oxford University Press (OUP), 1989-11-01)Field surveys were conducted to determine distribution and abundance of giant dam resources in the Philippines. All seven known species of giant clams were recorded with Tridacna crocea, T. maxima and T. squamosa occurring the most frequently. The larger species T. derasa, T. gigas, Hippopus hippopus and H. porcellanus were relatively rare. The reduction of giant dam stocks in the Philippines is due to the uncontrolled exploitation of this resource which is primarily gathered for shellcraft and as supplementary diet in coastal villages.