11. University of the Philippines - Marine Science Institute (UP - MSI)
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University of the Philippines - Marine Science Institute (UP - MSI) - Philippines - contributions to address the Ocean Decade Challenges
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- Size-dependent predation on juvenile sandfish, Holothuria scabra by seagrass-associated crabsCaasi, Olivier Josh C.; Gosselin, Louis A.; Juinio–Meñez, Marie Antonette (Cambridge University Press, 2023-10-23)High mortality of juvenile Holothuria scabra in seagrass nursery areas has been attributed to predation. In this study, laboratory and field experiments were conducted to determine the effect of the size of two seagrass–associated crabs, Thalamita crenata and Dardanus megistos, on the survival of juvenile sandfish at different sizes (1–10 g). Small juvenile sandfish (1–2 g) offered in field trials were more preferred by small Thalamita and large Dardanus. Non-lethal damage caused by both crabs were also evident, indicating differences in the mode of attack and consumption. The incidence of non-lethal wounds in medium and large juveniles in the laboratory indicate higher incidences of unsuccessful attacks by the crabs. Differences in consumption rate may be related to cheliped morphology and handling techniques, and activity patterns affecting encounter rates. Mortality rates of juvenile sandfish due to T. crenata (CW: 4.30–7.05 cm) ranged from 10–43%, while those by D. megistos (SL: 0.90–2.3 cm) was even higher at 34–53% after 24 h trials. This is the first report that a hermit crab D. megistos is a significant predator of juvenile sandfish. Results provide new insights on crab–soft-bodied prey interactions in tropical seagrass areas. These are also important considerations in stock restoration and ocean-based culture. Given that juveniles (≤10 g) are very vulnerable to predation by these common crab species, growing sandfish to larger sizes is essential prior to release in the field.
- Notes on the induced spawning and larval rearing of the Asian moon scallop, Amusium pleuronectes (Linné), in the laboratoryBelda, C. A.; Del Norte, A. G. C. (Elsevier, 1988-08)Sexual and chemical stimulations were effective in inducing the scallop, Amusium pleuronectes (Linné), to spawn sperm only, whereas thermal stimulation was not at all successful. Chemical stimulation consisted of serotonin injections into the ripe gonads. Fertilizable eggs were obtained by stripping gametes from the ovaries. Cleavage of zygotes (72.4 μm mean diameter) occured 1 h after fertilization. Trochophores (58.9–111.2 μm in length) and straight-hinge veligers or D-veligers (80.0–130.2 μm) were observed in less than 24 h. Five days after fertilization, the umbone stage (101.6–169.1 μm) was reached. Crawling pediveligers (174.0–250.0 μm) appeared after 9 days. Seawater in the culture vessels was changed 24 h after fertilization and every other day thereafter. The larvae were fed on Isochrysis galbana (Tahitian strain) at an initial concentration of 30 cells/gml.
- Diurnal and diel patterns in the photosynthetic performance of the agarophyte Gelidiella acerosaGanzon-Fortes, E. T. (Walter de Gruyter, 1997)Photosynthesis of the red alga Gelidiella acerosa was monitored on diurnal (during the day) and diel (24 h period) bases using the oxygen evolution technique in a closed system. Natural sunlight and artificial light were used to assess uniformity in the diurnal photosynthetic responses. Photosynthesis-irradiance (P-I) curves were also determined diurnally. On a diel basis, maximal photosynthetic rates occurred at day time and minimal rates occurred at night. Diurnally, photosynthesis fluctuated in different patterns depending on PFDs used. Under saturating but not photoinhibiting FFDs, photosynthesis exhibited an early morning minimum (a few hours after sunrise), a midday-noon maximum, sustained until late afternoon, then declined at or after sunset. However, when exposure to high PFDs (above 1200 μιηοΐ photons m"~s") were prolonged, i.e. from morning until afternoon, the photosynthetic performance suffered a depression starting from noon and persisting until afternoon. When PFDs lowered late in the afternoon, recovery of photosynthetic performance commenced resulting in increased photosynthetic rates. The P-I curve data corroborate findings of experiments using saturating but not photoinhibiting PFDs. The morning P-I curve had lower Pm and alpha, and higher Ik and Is values than the identical noon and afternoon P-I curves. This suggested that photosynthetic performance was yet inefficient in the morning but performed efficiently near midday until the afternoon. An endogenous circadian clock was implicated to have influenced the diurnal and diel patterns in the photosynthetic performance of G. acerosa. Photoinhibition was the other factor suspected to have altered the diurnal pattern.
- Genetic structure of giant clam (Tridacna derasa) populations from reefs in the Indo-PacificMacaranas, J. M.; Ablan, C. A.; Pante, M. J. R.; Benzie, J. A. H.; Williams, S. T. (Springer, 1992-06)Large genetic differences were observed among the Great Barrier Reef (GBR), Fiji and Philippine populations of Tridacna derasa (Roding) sampled in 1989 and 1990 (Nei's unbiased genetic distance, D,=0.137 to 0.341). This result contrasted strongly with the low genetic distance (D=0.032) reported previously for the giant clam T. maxima over similar geographical scales. No significant genetic differentiation was observed among most populations from the GBR (mean D=0.007), consistent with the high gene exchange expected in this highly connected reef system. However, significant differentiation resulting from differences in the frequencies of less common alleles between the North-Central GBR and South GBR (Swain region) were observed. Historical isolation of blocks of the Central Indo-West Pacific from the GBR and present-day restrictions to gene exchange between the GBR, Fiji and the Philippines as a result of oceanographic current patterns, were thought to be responsible for the high degree of genetic differentiation of T. derasa populations. The relevance of these findings to clam mariculture and reef restocking are briefly discussed.
- Five new sesquiterpenes from the red alga Laurencia flexilisde Nys, Rocky; Wright, Anthony D.; König, Gabriele M.; Sticher, Otto; Alino, Perry M. (American Chemical Society (ACS), 1993-06)The red alga Laurencia flexilis, collected from Philippine waters, yielded five new sesquiterpenoid metabolites, 3,4-epoxypalisadin A [1], 5B-acetoxypalisadin A [2], 12-bromopalisadin B [3], palisading C [4], and 5B-hydroxypalisadin B [5]. The known metabolites 6-10 were also isolated The unambiguous assignments of H- and C-nmr spectral data for compounds 7 and 8 are reported for the first time.
- The farmed Eucheuma species (Gigartinales, Rhodophyta) in Danajon Reef, Philippines: Carrageenan propertiesAzanza-Corrales, R.; Sa-a, P. (Springer, 1990-09)Six cultured ‘strains’ of Eucheuma denticulatum and E. alvarezii, from which stocks can be selected for the development of a Eucheuma ‘seedling bank’, were tested for their carrageenan quality from June to November 1988. Percent yield of all the varieties taken together was apparently higher in June, becoming lower in November (regression, r −0.785, probability, p ⩽ 0.001). Stepwise regression analysis was done to determine the existence of any relationship between any of the following parameters: gel strength, viscosity, sulfate content, month of sampling, and yield, whether taken individually or in combination. Results show variations of the yield with the month of sampling. ANOVA was performed to test whether there are differences in sulfate levels, gel strength, and viscosity between the Eucheuma alvarezii morphotypes. There was no significant difference between the green and the brown types.
- Impacts of aquaculture nutrient sources: ammonium uptake of commercially important eucheumatoids depends on phosphate levelsNarvarte, Bienson Ceasar V.; Hinaloc, Lourie Ann R.; Gonzaga, Shienna Mae C.; Roleda, Michael Y. (Springer, 2023-09-14)In an integrated multitrophic aquaculture (IMTA) system, seaweeds serve as extractive species that utilize excess nutrients, thereby reducing the risk of eutrophication and promoting sustainable aquaculture. However, the use of excessive fish feeds and the resultant faecal waste as nutrient streams can contribute to variations in nitrogen and phosphorus levels (e.g., primarily NH4+ and PO4−3) in the surrounding area and this may impact the physiology of the integrated seaweeds, particularly on how these species take up inorganic nutrients. In this study, the effect of different PO4−3 levels on NH4+ uptake of the three commercially important eucheumatoids Kappaphycus alvarezii, Kappaphycus striatus and Eucheuma denticulatum was examined under laboratory conditions. Seaweed thalli (n = 4) were incubated in seawater media containing 30 µM NH4+, and 0, 0.5, 1.0, 1.5, 3.0 or 5.0 µM PO4−3 for 1 h under a saturating light level of 116 ± 7.13 µmol photons m−2 s−1 inside a temperature-controlled laboratory. Species-specific responses to PO4−3 levels were observed. For K. alvarezii, maximum NH4+ uptake (17.8 ± 1.6 µmol gDW−1 h−1) was observed at 0.5 µM PO4−3 and the uptake rate declined at higher PO4−3 levels. For K. striatus, NH4+ uptake increased with increasing PO4−3 levels, with maximum N uptake (6.35 ± 0.9 µmol gDW−1 h−1) observed at 5.0 µM PO4−3. For E. denticulatum, maximum NH4+ uptake (14.6 ± 1.4 µmol gDW−1 h−1) was observed at 1.0 µM PO4−3. Our results suggest that among the three eucheumatoid species, the NH4+ uptake of K. striatus persists even at high levels of PO4−3. However, our results also showed that K. striatus had the lowest range of NH4+ uptake rates. These results should be taken into consideration when incorporating eucheumatoids in the IMTA system, where PO4−3levels significantly vary in space and time.
- Using deep-belief networks to understand propensity for livelihood change in a rural coastal community to further conservationLabao, Alfonso B.; Naval, Prospero C. Jr; Yap, David Leonides T.; Yap, Helen T. (Wiley Blackwell, Inc., 2020-08)Overharvesting of terrestrial and marine resources may be alleviated by encouraging an alternative configuration of livelihoods, particularly in rural communities in developing countries. Typical occupations in such areas include fishing and farming, and rural households often switch livelihood activities to suit climate and economic conditions. We used a machine-learning tool, deep-belief networks (DBN), and data from surveys of a rural Philippine coastal community to examine household desire to change livelihood. This desire is affected by a variety of factors, such as income, family needs, and feelings of work satisfaction, that are interrelated in complex ways. In farming households, livelihood changes often occur to diversify resources, increase income, and lessen economic risk. The DBN, given its multilayer perceptron structure, has a capacity to model nonlinear relationships among factors while providing an acceptable degree of accuracy. Relative to a set of 34 features (e.g., education, boat ownership, and work satisfaction), we examined the binary response variables desire to change work or not to change work. The best network had a test set accuracy of 97.5%. Among the features, 7 significantly affected desire to shift work: ethnicity, work satisfaction, number of persons in a household in ill health, number of fighting cocks owned, fishing engagement, buy-and-sell revenue, and educational level. A cross-correlation matrix of these 7 features indicated households less inclined to change work were those engaged in fishing and retail buying and selling. For fishing, provision of economic and other incentives should be considered to encourage changing from this occupation to allow recovery of fishery resources.
- Effect of starvation on development and survivorship of naupliar Calanus pacificus (Brodsky)Lopez, M. D. G. (Elsevier, 1996-10)In the marine planktonic copepod, Calanus pacificus (Brodsky), survivorship and development rate during the remaining naupliar stages were reduced when initial feeding was delayed for ~ 10 h after molting into naupliar stage III (NIII). In otherwise well-fed stages NIII-NVI, development and survivorship were reduced after starvation periods > 6 h and > 14 h, respectively. Molting rate and survivorship were lower in response to transient starvation than in response to constantly low food supplies. Stage NV was the least sensitive to transient starvation, while stages NIII and NVI were the most susceptible. Molting rates were reduced even after abundant food was subsequently provided. Thus, ambient food concentration at the time a population is sampled may not be an adequate index of future cohort success. Estimates of fine-scale to micro-scale particle distributions in situ suggest that NIII, the first feeding stage, is the instar most likely to experience short starvation periods if hatching occurs well below phytoplankton-rich strata.
- Feeding and diel vertical migration cycles of Metridia gerlachei (Giesbrecht) in coastal waters of the Antarctic PeninsulaLopez, M. D. G.; Huntley, M. E. (Springer, 1995-01)Diel vertical migration and feeding cycles of adult female Metridia gerlachei in the upper 290 m of a 335-m water column were measured during a total of 65 h in two periods of early summer (Dec 20–21 and Dec 25–26, 1991). Samples collected in eight depth strata by 35 MOCNESS tows (333-μm mesh) were analyzed for abundance and mean individual gut pigment content. Most of the copepod population was concentrated in a 50-m depth interval at all times. Feeding began simultaneously with nocturnal ascent from a depth of 200–250 m at ≈ 18:00 h (local time), when the relative change in ambient light intensity was greatest. Ingestion rate increased exponentially (ki = 0.988 h−1) at double the gut evacuation rate (ke = 0.488 h−1) as the population moved upward at 22.3–26.5 m h−1 through increasing concentrations of particulate chlorophyll-a. Although the bulk of the population did not move to depths shallower than 50 m, and began its downward migration at a rate of 20.8–31.7 mh−1 in complete darkness, individual females continued to make brief excursions into chlorophyll-rich surface waters (4–8 μg l−1) during the first few hours of population descent. Ingestion rate diminished abruptly by one order of magnitude (ki = 0.068 h−1) at dawn (≈ 03∶30 h). Within four more hours, the population had reached its daytime depth and gut pigment content remained constant at a minimum value until the next migration cycle. No feeding appeared to take place at depth during the day. Ingestion by M. gerlachei females removed < 4% of daily primary production, with only ≈ 20% of this amount being removed from surface waters by active vertical transport.