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National Committee on Marine Sciences (NCMS)

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AGROVOC Keyword: search.filters.agrovoc.water columnAuthor: search.filters.author.Yñiguez, Aletta T.

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    Characterizing the vertical phytoplankton distribution in the Philippine Sea off the northeastern coast of Luzon
    Cordero-Bailey, Kristina; Bollozos, Iris Salud F.; Palermo, Joseph Dominic H.; Silvano, Kathleen M.; Escobar, Ma. Teresa L.; Jacinto, Gil S.; San Diego-McGlone, Maria Lourdes; David, Laura T.; Yñiguez, Aletta T. (Elsevier BV, 2021-06)
    The vertical distribution of phytoplankton in the open ocean shows an increase in biomass at a depth referred to as the Subsurface Chlorophyll Maximum (SCM) that contributes significantly to the primary production of the water column. Hence, it is important to understand the dynamics that lead its formation and maintenance. This study examines the SCM in the Philippine Sea off the northeast coast of Luzon, utilizing bio-optical and empirical phytoplankton data from two oceanographic cruises conducted northeast of the island of Luzon in May/June 2011 and April/May 2012. Chlorophyll (Chl) profiles were converted to smoothed chlorophyll functions by using a b-spline basis. In 2011, the mean SCM depth was 97.24 m ± 22.33 m with mean SCM concentration of 0.43 μg/L ± 0.09 μg/L while in 2012, mean SCM was deeper at 115.45 m ± 24.25 m and mean SCM concentration of 0.31 ± 0.09 μg/L. Functional principal component analysis showed that the first principal component (PC) explained variability in the SCM depth, the second PC showed variability in the magnitude of the SCM concentration while the third PC accounted for the presence of multiple peaks. K-means clustering using the principal components resulted in three clusters which represented the offshore stations with the deepest SCM, stations within an observed cyclonic eddy with intermediate SCM and stations with coastal and shelf waters showing shallow SCM. Correlation analyses between Chl and physico-chemical and bio-optical parameters showed that Chl was positively correlated to beam attenuation, a bio-optical property that has been used as an alternative proxy for phytoplankton. This suggests that the observed SCMs represent actual increase in phytoplankton biomass. When the influence of the Kuroshio recirculation gyre was dominant in 2011, cooler temperature in surface waters was seen to significantly increase surface Chl. In 2012, highly saline waters from the tropical North Equatorial Current (NEC) waters appeared to lower the Chl distribution, particularly at the SCM. Phytoplankton abundance was recorded to be higher at the SCM than the surface in both years. In 2011, different species of diatoms dominated all clusters, except at the SCM of the coastal and shelf cluster wherein the dinoflagellate Gyrodinium grossestriatum was dominant. Most dominant species from 2011 were conspicuously absent in 2012 and there was a shift to the diatoms Fragilariopsis (surface), Thalassiosira and Rhizosolenia spp. in all clusters. These provide new insights on the phytoplankton community in relation to the changes in the oceanic circulation from subtropical North Pacific water in 2011 to tropical NEC water in 2012.
    This work is Marine Science Institute contribution number 482. We would like to acknowledge Dr. Cesar Villanoy and Dr. Olivia Cabrera and the anonymous reviewers who provided invaluable inputs for the development and improvement of the paper.
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    Nearshore to offshore trends in plankton assemblage and stable isotopes in reefs of the West Philippine Sea
    Yñiguez, Aletta T.; Apego, Gianina Cassandra May; Mendoza, Norman; Gomez, Norchel Corcia; Jacinto, Gil S. (Frontiers Media SA, 2022-01-25)
    Coral reefs are typified by their benthic components, and reef diversity and productivity are traditionally ascribed to the symbiotic association between corals and zooxanthellae, and other macroalgal forms. Less understood is the role of plankton and adjacent pelagic areas in contributing to reef productivity. Half of the reef benthos are filter or particle feeders, while a significant proportion of reef fishes are planktivorous. These organisms can serve as bridges between adjacent oceanic areas to the reef proper, and the pelagic and benthic realm. Here, we investigate the plankton trophic dynamics in two reef systems in the West Philippine Sea. Physico-chemical data, phytoplankton and mesozooplankton samples were collected from stations spanning offshore to reef areas per site. These were subjected to microscopic and stable isotope analysis to determine variability in plankton distribution, phytoplankton and zooplankton interactions, and gain insights into the trophic dynamics and productivity of reefs. Results showed distinct variations in plankton biomass and assemblage from offshore to reef areas, as well as between the reef systems. Phytoplankton distributions pointed toward filtering out of cells across the fore reef and reef flat areas, while mesozooplankton distributions could be mediated more by other factors. Isotopic signatures of δ13C and δ15N indicated the influence of different nutrient sources for phytoplankton and that mesozooplankton relied only partly on phytoplankton for food in most areas of the reefs. The mesozooplankton likely also obtain food from other sources such as the microbial and detrital pathways. More in-depth spatio-temporal studies on these bentho-pelagic interactions are recommended, which can provide more robust estimates of the trophic dynamics of these reefs that are situated in important fishing grounds and key biodiversity areas.
    We thank Cesar Villanoy and the Physical Oceanography laboratory for organizing the research cruise, the Philippine Navy and the BRP Gregorio Velasquez (AGR 702) for the help in sample collection during the research expedition conducted in the Kalayaan Group of Islands in 2017. We also thank the Department of Science and Technology – Philippine Nuclear Research Institute for the collaboration in conducting the stable isotope analyses, John Kristoffer Q. Andres for identifying the zooplankton samples, and John Michael N. Aguilar for analyzing the samples for chemical parameters.