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National Committee on Marine Sciences (NCMS)

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    Sexual reproduction in the soft coral Lobophytum schoedei in Bolinao‐Anda Reef Complex, Pangasinan, northwestern Philippines
    Baran, Christine C.; Baria‐Rodriguez, Maria Vanessa (Wiley, 2021-04-02)
    The characterization of early life-history strategies of soft corals is important in understanding population maintenance, replenishment, and recovery in disturbed coral reefs. This study examined the sexual reproduction of the soft coral Lobophytum schoedei in the Bolinao-Anda Reef Complex (BARC), a degraded reef in northwestern Philippines. Reproductive strategies such as sexuality, sex ratio, fecundity, and reproductive timing were examined. Random colonies of L. schoedei were sampled a few weeks before the predicted time of spawning to assess fecundity (n = 73 colonies), and sexuality and sex ratio (n = 221 colonies). Monthly sampling of tagged colonies of L. schoedei (n = 20) was done over 13 months to determine the reproductive timing through polyp dissection. Peak of annual spawning was inferred based on the presence of large gametes and their absence in the next sampling period. Results showed that L. schoedei is a gonochoric broadcast spawner with 1:1.1 sex ratio. Although oogenesis and spermatogenesis exhibited overlapping cycles, both gametes matured and spawned in April, coinciding with increasing sea surface temperature. Prior to spawning, oocytes and spermaries ranged 300–633 µm and 150–337 µm in diameter, respectively. Mean female fecundity was 6.7 ± 3.9 oocytes per polyp and male fecundity was 39.2 ± 22.5 (±SD) spermaries per polyp. Some of these results, including the low number of oocytes produced by female polyps, may be caused by sexual reproduction in a degraded reef environment. Understanding these reproductive traits may be useful for predicting the resiliency of populations of L. schoedei in response to ongoing and future environmental change.
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    Contrasting reproductive strategies between stress-tolerant and competitive coral taxa
    Bonilla, K. G.; Guest, J. R.; Baria-Rodriguez, M. V. (Springer, 2023-04-19)
    Reproductive traits such as fecundity (i.e., the number of gametes produced) and the size and age of coral colonies at reproductive onset can vary in predictable ways among life history strategies. However, most studies on the onset of reproductive maturity in corals only report the presence or absence of oocytes with little known about variation in fecundity across size and age classes. This study aimed to determine the colony size and fecundity at the onset of reproductive maturity across size classes of two scleractinian corals with contrasting life history strategies, Acropora millepora (competitive) and Favites colemani (stress-tolerant). Colonies at a site in northwestern Philippines were sampled to determine the smallest colony size class with mature oocytes and to estimate fecundity across size classes. Histological slides were also prepared to verify the presence of mature gametes. Colonies were able to produce mature oocytes when they had attained colony diameters of 4.7 cm for A. millepora and 1.5 cm for F. colemani. A. millepora had lower fecundity, but larger oocytes compared to F. colemani. Although small colonies can contribute to the larval pool, the proportion of mature colonies increased for larger size classes, suggesting that larger colonies make a disproportionately greater contribution to population reproductive output. These findings contribute to our understanding of coral population dynamics, particularly in parameterizing population and demographic models for different coral life histories.
    We are grateful to Christine Baran, Jue Alef Lalas, Jerry Arboleda, Gabriel de Guzman, the students and research assistants of Community and Ecology and Interactions of Marine Bionts and Benthic Ecosystems Laboratories for their valuable assistance during field and laboratory works, Darryl Valino for the site map, and Liam Lachs for the assistance on the statistical analyses. This research was supported by the University of the Philippines Marine Science Institute’s In-house project, Department of Science and Technology – ASTHRDP Thesis Grant, and University of the Philippines – Office of the Vice President for Academic Affairs’ Balik Ph.D. project (OVPAA-BPhD-2018-02).
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    Metabolic responses of the scleractinian coral Porites cylindrica Dana to water motion. I. Oxygen flux studies
    Rex, Augustus; Montebon, F.; Yap, Helen T. (Elsevier, 1995-03)
    Nubbins of Porites cylindrica Dana collected from a shallow reef flat in the northwestern Philippines were studied for water motion effects. Specimens were maintained in field and laboratory high (HWM) and low (LWM) water motion setups. The average maintenance times were 93 and 77 days for the field and laboratory study, respectively, which were carried out in tandem. After each maintenance period, oxygen fluxes of the corals were measured with increasing stirring rates in a laboratory flow-through respirometry system under a constant light intensity. Photosynthesis-irradiance (P-I) curves were also determined for the laboratory maintained nubbins as well as for a set of control nubbins which were kept in the collection site for 71 days. In both HWM and LWM corals, maximum rates of net photosynthesis (NP) and respiration (R) were achieved upon increasing stirring rates or turbulence to a certain level, indicating that the boundary layer limiting oxygen diffusion had been reduced to a minimum. The LWM corals attained maximum photosynthetic rates at lower rates of water motion, suggesting greater photosynthetic efficiency at lower levels of turbulence than their HWM counterparts. Profiles of NP and R with increasing stirring rates were consistently depressed for the LWM corals. Significant differences between the HWM and LWM treatments were detected in the NP profiles of the field maintained corals and in the R profiles of the laboratory maintained nubbins. The small yet significant difference in the NP profiles of the field HWM and LWM corals was attributed to the subsaturating irradiance used in the laboratory measurements because P-I curves of the laboratory maintained corals showed a large and significant difference between water motion treatments (HWM > LWM) at higher irradiances. While exhibiting lower photosynthetic rates, LWM corals had proportionally lower respiration rates resulting in P:R values very close to those of the HWM corals. Results suggest that Porites cylindrica is able to maintain its metabolic efficiency despite changes in the water motion regime.