National Committee on Marine Sciences (NCMS)

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Molecular-assisted taxonomic study on the Sargassum C.Agardh (Fucales, Phaeophyceae) in Northwestern Luzon, Philippines
Santiañez, Wilfred John E.; Lastimoso, John Michael L.; Hoshino, Masakazu; Villafuerte, Brix Nester Q.; Kogame, Kazuhiro; Trono, Gavino C. (Museum National d'Histoire Naturelle, 2023-10-18)
The diversity of the brown algal genus Sargassum C.Agardh in the Philippines is the highest in the tropical western Pacific Ocean. However, most studies on Philippine Sargassum are based on morphoanatomies and the assumption that the genus is very diverse in the country has never been tested based on molecular information. Considering that many Sargassum species are highly polymorphic and the recent advance on Sargassum systematics facilitated by molecular phylogenetic studies, we believe that the species of Sargassum from the Philippines should now be reassessed with the tools of molecular taxonomy. We present here the results of our molecular-assisted taxonomic studies on the Sargassum of the northern Philippines, particularly along the coasts of four coastal provinces in northwestern Luzon (i.e., Ilocos Norte, Ilocos Sur, La Union, and Pangasinan). We recognized three distinct species lineages, namely, Sargassum aquifolium (Turner) C.Agardh, Sargassum ilicifolium (Turner) C.Agardh, and Sargassum polycystum C.Agardh based on our molecular analyses of 74 specimens from our study areas. Our morphological observations on the range of characters of these species also suggest that several common Sargassum taxa in the Philippines have been misidentified. Particularly, specimens previously attributed to S. kushimotense Yendo should be referred as S. aquifolium while the widely distributed and highly plastic S. ilicifolium is often confused and identified in the Philippines under several names including S. crassifolium J.Agardh, S. cristaefolium C.Agardh, and S. turbinarioides Grunow. Taken together, our results suggest that Sargassum biodiversity in the Philippines may have been inflated by misidentifications, and, that species diversity is actually much lower than initially thought.
Nitrate and phosphate uptake of morphologically distinct calcified macroalgae
Narvarte, Bienson Ceasar V.; Hinaloc, Lourie Ann R.; Gonzaga, Shienna Mae C.; Crisostomo, Bea A.; Genovia, Tom Gerald T.; Roleda, Michael Y. (Informa UK Limited, 2023-05-02)
Calcified macroalgae are essential components of marine ecosystem, yet much of their physiology remains to be understood. Here, the nutrient (NO₃^– and PO₄^–3) uptake physiologies of two branched macroalgae, Actinotrichia fragilis (Nemaliophycidae) and Amphiroa fragilissima (Corallinophycidae), and the non-geniculate rhodolith Sporolithon sp. (Corallinophycidae) were examined. Sporolithon sp. had the lowest uptake rate through time and the three calcified macroalgae had a surge in NO₃^– and PO₄^–3 uptake that occurred between 3 and 20 min, with a maximum uptake at 3 min, after which the nutrient uptake rates declined. The NO₃^– uptake of the three calcified macroalgae followed Michaelis-Menten kinetics. For NO₃^– uptake, Sporolithon sp. had the lowest K_m (2.72 ± 0.97 µM), V_max (0.08 ± 0.01 µmol gDW^–1 h^–1), V_max/K_m (0.05 ± 0.03 µmol gDW^–1 h^–1 µM⁻¹) and α (0.01 ± 0.00 µmol gDW^–1 h^–1 µM⁻¹), while A. fragilis had the highest K_m (12.35 ± 0.71 µM) and V_max (6.41 ± 0.23 µmol gDW^–1 h^–1), and A. fragilissima had the highest V_max/K_m (1.52 ± 0.26 µmol gDW^–1 h–1 µM⁻¹) and α (0.37 ± 0.01 µmol gDW^–1 h^–1 µM⁻¹). Moreover, the PO₄^–3 uptake rate of the three species was faster at higher PO₄^–3 levels. These differences in species-specific nutrient uptake traits are likely caused by differences in morphology. These traits are important for survival and proliferation of this group of marine organisms, particularly in a nutrient-variable environment.
Taxonomy and toxin production of Gambierdiscus carpenteri (Dinophyceae) in a tropical marine ecosystem: The first record from the Philippines
Vacarizas, Joshua; Benico, Garry; Austero, Nero; Azanza, Rhodora (Elsevier, 2018-12)
Morphological and phylogenetic analysis showed that the Gambierdiscus isolate from Bolinao, Philippines belongs to the species of G. carpenteri. It was morphologically more similar to the Merimbula strain than the subtropical Florida Keys strain. Growth and toxin production were also investigated at varying levels of temperature, salinity, and irradiance. Gambierdiscus are known to grow favorably in a low light environment. However, this study showed high growth rates of G. carpenteri even at high irradiance levels. Generally, cells produced more toxins at lower treatment levels. Highest cellular toxin content recorded was 7.48 ± 0.49 pg Pbtx eq/cell at culture conditions of 25 °C, 100 μmol photons m−2 s−1, and salinity of 26. Growth rate and toxin production data suggest that cells produced more toxins during the slowest growth at certain range of treatments. This information gives insight into how changes in environmental conditions may affect toxin production and growth of G. carpenteri.