UNESCO Intergovernmental Oceanographic Commission (IOC) - Philippines
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- Population genetic structure of the milkfish, Chanos chanos , based on PCR-RFLP analysis of the mitochondrial control region.Ravago-Gotanco, Rachel G.; Juinio-Meñez, Ma. Antonette (Springer, 2003-06-24)The milkfish, Chanos chanos (Forsskål, 1775) is a pelagic, monotypic gonorhynchiform widely distributed in the tropical Indo-Pacific. This study evaluates temporal variability of milkfish samples from the Philippine archipelago, and spatial variability at two geographic scales based on restriction fragment length polymorphism (RFLP) analysis of a portion of the mitochondrial control region. High levels of genetic diversity characterize the milkfish control region (mean h=0.908, π=1.59%), with 74 haplotypes detected among the 367 fish analyzed. For temporal analysis of Philippine samples, milkfish were collected over 2 years from three sites (inter-annual variation), and sampled twice within a year during different seasons at four sites (intra-annual variation). No significant temporal variability was detected between or within years. Significant spatial differentiation among the Philippine samples was observed (F ST=0.006, P<0.05), with two northeastern samples, Claveria and Dingalan, found to be genetically distinct. However, an hierarchical analysis of molecular variance (AMOVA), where samples were grouped into four geographic regions, revealed very low levels of genetic partitioning, with less than 1% of the total variation attributed to between-region differences, and lack of genetic structure. Nonetheless, the existence of putative northeastern Philippine populations is not discounted. Strong genetic structure across broad geographical scales was revealed by AMOVA, with 11% of the molecular variance based on haplotype frequencies allocated between three distinct groups: Indian Ocean, west Pacific (Philippines) and north central Pacific (Hawaii) The broad-scale genetic structure points to limited gene flow among disjunct Indo-Pacific populations.
- Survivorship of coral juveniles in a fish farm environmentVillanueva, Ronald D.; Yap, Helen T.; Montaño, Marco Nemesio E. (Elsevier BV, 2005-01)Intensive fish farming is an emerging coastal activity that can potentially enhance sedimentation and promote eutrophication in fringing coral reefs. Here, we investigate the effect of fish farm effluent on the juvenile survivorship of the reef-building coral Seriatopora caliendrum. One-month old juvenile corals (on terracotta tiles) were deployed in fish farm and reference (reef) sites in Bolinao, the Philippines at a depth of 2 m. After forty days, no survivor was recovered in the fish farm, while survivorship was low (11%) in the reference site, with the survivors’ growth rate at 3.3 polyps mo−1 or 1.3 mm2 mo−1. The fish farm deployed tiles were covered with muddy sediment and were colonized by barnacles, whereas those in the reference site were overgrown by a short stand of filamentous macroalgae. Environmental monitoring revealed higher nutrient levels (ammonia and phosphate), sedimentation rate, and organic matter flux, as well as diminished water transparency and dissolved oxygen levels in the fish farm compared to the reference site. Hence, intensive fish farming offers a suite of physical, chemical and biological modifications of the coastal marine environment which have a detrimental effect on the survivorship of coral juveniles.
- Experimental evaluation of the effects of siltation-derived changes in sediment conditions on the Philippine seagrass Cymodocea rotundataHalun, Zayda; Terrados, Jorge; Borum, Jens; Kamp-Nielsen, Lars; Duarte, Carlos M.; Fortes, Miguel D. (Elsevier BV, 2002-11)This study investigated if siltation-associated changes in the sediments are detrimental to seagrasses. We chose Cymodocea rotundata as the test species because it is considered one of the Southeast Asian seagrass species most sensitive to siltation. The approach included the (1) evaluation of the effects of silted sediments on plant growth, evaluation of the effects of in situ sulfide additions to the sediment on (2) the production of shoots, rhizomes and roots, and on the elongation rate of the horizontal rhizomes of plants located at the edge of a meadow, and on (3) leaf growth, mass allocation patterns and shoot density in a well-developed seagrass meadow. The results showed that under high light availability, major changes in sediment conditions associated with siltation did not negatively affect the plants but enhanced their growth likely by increasing the availability of nutrients. Pore water sulfide concentrations of 1 mM reduced by more than half the production of shoots, rhizome and roots, and the elongation rates of horizontal rhizomes of C. rotundata plants at the edge of the meadow, but had no effects on leaf growth and shoot density in a well-developed C. rotundata meadow.
- Attempts to model the bloom dynamics of Pyrodinium, a tropical toxic dinoflagellateVillanoy, Cesar L.; Azanza, Rhodora V.; Altemerano, Aubrey; Casil, Ana Liza (Elsevier BV, 2006-03)For the first time, several models have been used to aid in the understanding of the bloom dynamics of Pyrodinium bahamense var. compressum, the major causal organism of toxic algal blooms in Manila Bay and several areas in the tropical world. The complex life cycle of Pyrodinium includes the formation of cysts that settle at the sediments, which can serve as the inoculum for the next bloom. The seasonal variation of temperature and salinity reflects the combined effects of convection and water column stability, which can control vertical movement of plankton and other parameters essential to its growth. The significance of wind forcing appears to be related to the potential to resuspend cysts. In the absence of wind, tidal currents in the inner part of the bay may be too weak to induce resuspension. The addition of wind results in a significant increase in bottom current velocity. Off Cavite at the southeast, bottom velocity is enhanced by orbital motion due to waves, one of the reasons why sediments off this area are dominated by sandy material. The strong vertical mixing of the water column at depths of less than 10 m may influence nutrient and consequently, plankton populations. The wave field during the southwest monsoon indicates that its contribution to the bottom velocity dominates in this area of the bay. Bloom simulations using combined bio-physical parameters show that direction of advection is almost always along wind direction. The dispersal distances increases if the Pyrodinium cells are found higher in the water column. For cells originating from southeastern (Cavite) sources, the direction of transport is slightly towards the north. In either case, the formation of cysts after a bloom is adjacent to the northern area (Pampanga) for blooms originating from the western side (Bataan) and along the eastern side (Parañaque–Manila) for blooms originating from the southeastern side (Cavite). Comparison with a few records of bloom occurrences in Manila Bay shows some consistent features. Reports of these blooms also showed that they occurred almost always during spring tides. There appears to be two main systems for bloom formation: one fed by cyst beds in the west (Bataan) which is advected along the west–northwest coast (Bataan–Bulacan) while the other one is fed by the southeast (Cavite) cyst beds that dominates in the east-southeast (Parañaque–Cavite) area.
- Impacts of milkfish (Chanos chanos) aquaculture on carbon and nutrient fluxes in the Bolinao area, PhilippinesHolmer, Marianne; Marbá, Núria; Terrados, Jorge; Duarte, Carlos M.; Fortes, Mike D. (Elsevier BV, 2002-07)Sediment oxygen consumption, TCO2 production and nutrient fluxes across the sediment–water interface were measured in sediments within and along a transect from four fish pens with production of milkfish (Chanos chanos) in the Bolinao area, The Philippines. The four fish pens were each representing a specific period in the production cycling. There was a positive linear relationship between the rates of sedimentation inside the fish pens and the sediment oxygen consumption indicating that the benthic processes were controlled by the input of organic matter from fish production. The nutrient fluxes were generally higher inside the fish pens, and nitrate was taken up (1.7–5.8 mmol m−2 d−1) whereas ammonium (1–22 mmol m−2 d−1) and phosphate (0.2–4.7 mmol m−2 d−1) were released from the sediments. The sediments were enriched in organic matter with up to a factor 4 compared to outside. A mass balance for one crop of milkfish was constructed based on production data and on measured fluxes of nutrients in the fish pens to assess the loss of carbon and nutrients to the environment. There was a loss to the surroundings of carbon and nitrogen of 51–68% of the total input, whereas phosphorus was buried in the sediments inside the fish pens which acted as net sinks of phosphorus. The results obtained suggest that fish pen culture as practiced in the Bolinao area, leads to even greater impacts on benthic carbon and nutrient cycling than those found in suspended cage cultures.
- Locomotor activity and growth response of glass eel Anguilla marmorata exposed to different salinity levelsAquino, Goldyn Anne G.; Cabaitan, Patrick C.; Secor, David H. (Springer, 2021-02-16)Temperate eels are well known for partial migration where contingents may remain settled in marine habitats or move between seawater and brackish and freshwater habitats during their sub-adult life. This behaviour is less described in tropical Anguillid eels, particularly as it relates to salinity preference, habitat selection, and growth. In this study, glass eels Anguilla marmorata were collected from an estuary near the Cagayan River, northern Philippines, and observed for their behaviour and growth response in freshwater, brackish water, and seawater. A. marmorata glass eels spent most of their time in freshwater and brackish water and the least amount of time in seawater throughout the 30-min trial. Some individuals showed switching behaviour between salinity choices, but freshwater was the final selection. Growth-in-length was moderately and significantly lower for seawater-reared glass eels than those reared in freshwater and brackish water. Glass eels reared in freshwater had the highest survival, followed by those reared in brackish water and seawater. Habitat choice, growth, and survival trials all indicated that A. marmorata glass eels found in the Cagayan River have a major preference for freshwater and brackish water over seawater. These findings raise concerns with regard to the increased fishing pressure of eels, water pollution, and quarrying which is concentrated in freshwater habitats.
- Shifts in coral clonality along a gradient of disturbance: insights on reproduction and dispersal of Pocillopora acutaTorres, Andrew F.; Forsman, Zac H.; Ravago-Gotanco, Rachel (Springer, 2020-10-14)Pocillopora acuta, formerly synonymized with P. damicornis, is an ecologically important reef-building coral that exhibits mixed reproductive modes, geographic variation in clonality, and conflicting reports of population genetic structure. Using 16 polymorphic microsatellite loci, this study examined clonality, genetic differentiation, and connectivity of genetically identified P. acuta (n = 428) in the Bolinao–Anda Reef Complex (BARC), Philippines, characterized by varying levels of wave exposure. Estimates of clonal richness indicate that the populations are largely derived from asexual reproduction, more likely via dispersal of ameiotic larvae. Clonal richness, population density, and mean colony size vary with wave exposure, suggesting the potential influence of local-scale disturbance on clonality, reproductive mode, and population structure. Populations in low-energy environments were characterized by greater colony density, larger colonies, and a greater proportion of clones compared to high-energy environments. Despite evidence for realized clonal dispersal of P. acuta extending up to 22 km, significant genetic differentiation among BARC populations reveals restricted gene flow at small spatial scales. Moreover, genetic differentiation is more pronounced when considering the spatial distribution of clones (FST including clones = 0.059; FST excluding clones = 0.028), suggesting that (1) asexually produced propagules are likely retained locally and across-site settlement is not as common; and (2) sexually derived propagules may have broader scales of dispersal. This study reexamines the population genetics of this often-problematic coral and underlines the importance of contextualizing site and species biology in designing or enhancing management towards the maintenance of functional genetic diversity and pathways of connectivity among populations.This study was supported by the Philippine Department of Science and Technology (DOST)—Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development, the Department of Environment and Natural Resources—Biodiversity Management Bureau, and the University of the Philippines Marine Science Institute. The authors thank Darryl Valino, Mikhael Tañedo, Romer Albino, David Siquioco, Lovely Heyres, and Emmeline Jamodiong for assisting with field collections. Relative wave exposure data were produced by Cesar Villanoy and Erlinda Salamante with the support of DOST. This is MSI contribution number 475, HIMB publication number 1829, and SOEST number 11155.
- Fisheries Administrative Order No. 144-2: Series of 1992. Suspension of the effectivity of Fisheries Administrative Order No. 144-1. s. 1992.(Department of Agriculture, 1992-06-29)
- Detachment of Porites cylindrica nubbins by herbivorous fishesQuimpo, Timothy J. R.; Cabaitan, Patrick C.; Hoey, Andrew S. (Wiley, 2020-03)A form of active restoration for coral assemblages involves culturing coral nubbins at nursery sites before transplantation to recipient reefs. Incidental grazing and/or directed predation by local fish assemblages are major sources of dislodgement and mortality for coral nubbins in nurseries. However, the rate of coral nubbin detachment, how this varies across fish taxa, and whether nubbin size affects rates of detachment warrant further investigation. We used field and aquaria experiments to examine the effect of incidental grazing and predation on the detachment of Porites cylindrica nubbins of different sizes (0.5, 1, 2, 3, 4, and 5 cm height). Short-term (6 hours) exposure of nubbins to local fish assemblages at Lucero Reef, northwestern Philippines, caused higher detachment (1.93% ± 0.53 SE) compared to caged controls (0.16% ± 0.16 SE), with no detectable effect of nubbin size. To identify the impact of individual fish species, nubbins were exposed to one of four locally abundant herbivorous and corallivorous fish species in aquaria for 8 hours. Nubbin detachment was greater when exposed to Chlorurus spilurus (1.20–36.2%) and Siganus fuscescens (0.00–15.0%) than Chaetodon lunulatus (0.00–4.00%) and Chaetodon kleinii (0.00–1.20%), with the smallest nubbins (0.5 cm) being the most vulnerable. Our results suggest that incidental grazing by herbivorous fishes, especially parrotfishes, may potentially be an important source of detachment and likely mortality of nubbins. Optimizing coral nursery protocols should consider potential trade-offs between excluding grazing fishes and the accumulation of algal material on caging structures to minimize nubbin mortality and improve coral restoration success.