Search

Eukaryotic picophytoplankton (EPP) play vital roles in primary productivity and biogeochemical cycling in the marine environment. In this study, we explored the diversity of EPP communities in two different embayments and the shifts in their community structuring during monsoonal reversal in the northwestern Philippines. Water samples were collected weekly from late northeast (NE) monsoon to intermonsoon (IM) or summer periods (February--April 2019) in Bolinao, Pangasinan, and once in January in Masinloc, Zambales. EPP community profiling was done through targeted sequencing of the V4 region of the 18S rRNA gene. Grouping of samples based on physicochemical parameters was consistent with that of community beta diversity, suggesting strong clustering between late NE and IM periods. This exhibits shortterm community shifts of EPPs possibly associated with the monsoonal transition. Specifically, overall EPP alpha diversity increased towards summer coupled with increased temperature and lower nutrient concentrations. NE monsoon samples from Bolinao and Masinloc were dominated by Chlorophyta and Stramenopiles, while Prymnesiophyta, Rhizaria, and Picozoa dominated the IM period samples in Bolinao. Specifically, the prasinophytes (Chlorophyta) Ostreococcus and Nannochloris distinguished the late NE communities of Masinloc and Bolinao, respectively. Phylogenetic analysis of dominant photosynthetic EPP further revealed the presence of Clades B5 and A1 of Micromonas, as well as Clades B and E of Ostreococcus. Tree topology of Ostreococcus diversity suggests the presence of a clade distinct from other established clades, possibly indicating novel diversity in the West Philippine Sea. This is the first report of these major picophytoplankton in Philippine waters, suggesting their significance and potential "hidden" diversity, which warrants further studies. [ABSTRACT FROM AUTHOR]

Epiphytic microalgae can significantly affect the host seaweed either by complementing, or competing for, resources. Here, epiphytic diatom and dinoflagellate species assemblages on the macroalgae Acanthophora spicifera, Hypnea pannosa and Gracilaria salicornia collected during the north-east (February), inter- (April) and south-west (June) monsoons in 2015 along the coast of Lucero, Pangasinan, North-western Philippines were examined and characterized. Results showed that diatom–dinoflagellate assemblages strongly clustered by season rather than by geographic location. Within season, a minor clustering by macroalgal forms, rather than host species identity, was also observed, which could be associated with the differences in the complexity and texture of the upright and prostrate seaweeds. Examination of the 'thallisphere' using confocal laser scanning microscopy further revealed the close proximity of some of the 'resident' epiphytic species to the cortical cells of the host, causing deformities and implying more complex interactions. Our results suggest that epiphytic community assemblages were influenced by both the environmental conditions associated with seasonal variation and the microhabitats in the surface of the different algal forms. [ABSTRACT FROM AUTHOR]

Marine plastics have been shown to affect all organisms across the trophic levels including the microbial communities, influencing their community assembly, composition, metabolic processes, and ecosystem functions. Thus, studying plastic-microbe interactions in the marine environment is important in understanding its implications alongside the growing issue of plastic pollution. The Philippines, despite being suggested as the third-largest contributor to marine plastic debris, currently does not have any existing national research programs on basic plastics research, resulting in our limited understanding of the extent and implications in the country. This paper then reviews the current status and knowledge of the plastic-microbe association focusing on how plastic surfaces serve as a new environment for marine microbes, how this system could become dispersal mechanisms of unwanted microorganisms, and how microbes possibly contribute to the biodegradation of plastics in the marine environment. These also translate to possible research opportunities for Filipino scientists to work on the topic. [ABSTRACT FROM AUTHOR]

Pellicle or temporary cysts ofPyrodinium bahamensevar.compressum(Böhm) Steidinger, Tester & F.J.R. Taylor and their role in bloom dynamics have not yet been adequately characterized and understood. We investigated the role of temperature- and nutrient-mediated stress as factors that could induce pellicle formation in batch cultures. Cellular features and their implications for temporary cyst viability were examined using confocal laser scanning microscopy (CLSM). Our data suggest that temperature change is one of the key factors influencing pellicle formation, preserving viability at low temperature (i.e. 13°C). Hypnocysts (resting cysts) were not observed. During pellicle formation, motile cells generally undergo ecdysis, extrusion of cytoplasmic materials and bacteria, compaction of the nucleus and non-motility. The outermost covering of the temporary cysts shows red autofluorescence and it contains lower concentrations of chlorophyll (chl)aand no detectable chlc.The nuclear region is surrounded by transitional red bodies and other unidentified cellular structures. Temporary cysts can immediately revert back to the motile state upon exposure to optimum conditions. This is accompanied by the expansion of the nuclear region, regeneration of the chloroplasts and enlargement of the cell. Developmental changes during reversal of temporary cysts to motile forms were also observed to cause breaks in the cell covering that could serve as sites for bacterial entry. Though observedin vitro, such behaviour may also be occurring in nature especially as a response to drastic short-lived environmental changes. This is the first detailed report on the characteristics of temporary cysts ofP. bahamensevar. compressum. [ABSTRACT FROM AUTHOR]