<p>Since 1983, San Pedro Bay in the Philippines had been reported to be the site of episodic <em>Pyrodinium bahamense </em>var. <em>compressum</em> blooms that cause paralytic shellfish poisoning in its nearby coastal communities. This bay is also subjected to numerous typhoons, the strongest of which was super typhoon Haiyan in November 8, 2013.<strong> </strong>Phytoplankton ecology of this bay must have unique characteristics. For the first time, the seasonal dynamics of potentially toxic and harmful phytoplankton in this bay is elucidated. This is also the first record of a bloom of the cyanobacteria, <em>Trichodesmium erythraeum</em> that reached 90,000 cells/L in April 2013. There were 19 other potentially toxic and harmful phytoplankton encountered during the sampling period. This consisted of a haptophyte, <em>Phaeocystis globosa, </em>the diatom <em>Pseudo-nitzschia</em> and 17 dinoflagellates. Seven of these harmful algae had densities high enough to be traced through time.<strong> </strong>Normally, diatoms abound during the dry season. But here, <em>Pseudo-nitzschia </em>increased in abundance during the wet season of 2012 and 2013. The dinoflagellates behaved as expected and exhibited a relative increase in cell density during the rainy season of both years. <em>Phaeocystis globosa</em> also increased during the wet season. High nutrient availability during this season must have influenced the behavior of the phytoplankton despite differences in temperature and light intensity among seasons. Other notable but rare harmful species found only in plankton net tows during the study were <em>Pyrodinium bahamense </em>var. <em>compressum, Alexandrium tamiyavanichii</em>, <em>Cochlodinium</em> <em>polykrikoides, </em>and <em>Noctiluca scintillans. </em> <strong></strong></p>
In recent years, harmful algal blooms (HABs), commonly known as red tide, have started to occur year-round in the warm tropical marine waters of Eastern Visayas, Philippines. These are a threat to public safety and cause enormous loss in industries relying on marine resources. The first step in solving this problem is to establish the distribution and succession of phytoplankton communities and harmful microalgae that exist in the region. For the first time, simultaneous monthly monitoring of the phytoplankton community was conducted in five HAB-affected bays of Leyte and Samar islands. We observed spatial differences on the environmental profiles between the five bays in the two islands and these differences may, in part, influence the distribution and abundance of the phytoplankton community residing within these areas. Diatom associated groups were prevalent in all sampling sites, however, HAB causative species were abundant in the bays in Samar during the sampling period. Five (5) genera and nine (9) species that may cause HAB were identified in all five bays. These are potential vectors for paralytic shellfish poisoning, amnesic shellfish poisoning, diarrhetic shellfish poisoning, and fish kill due to hypoxia. The correlation analysis confirmed that the majority of potential HAB vectors correlated with temperature, dissolved oxygen, rainfall, nitrate, and phosphate. The abundance of Pyrodinium bahamense observed in October to November in Samar coincided with several red tide alerts announced by the region’s fishery agency. This however, was never observed to dominate the phytoplankton community. Instead, the following diatoms dominated the five bays; Skeletonema, Pseudo-nitzschia, Bacteriastrum, Chaetoceros, Rhizosolenia and Thalassionema. This is a pioneering study that shows a simultaneous snapshot on the community structure and environmental profiles in these five bays in Eastern Visayas in 2020–2021. It discusses the effects of mariculture to its phytoplankton community and vice versa. Relationships between different phytoplankton species were further observed. This contributes to the knowledge of phytoplankton ecology in warm waters which is necessary to understand future phytoplankton ecosystems affected by sea temperature rise due to climate change.
Iodine is known as an essential mineral for thyroid hormone production in humans. It is water- soluble and diffuses into the atmosphere, where it is thought to break ozone molecules. Caulerpa racemosa (Phylum Chlorophyta, Class Ulvophyceae, Order Bropsidales) is a common dietary seaweed believed to be a good source of iodine in the Philippines. As of this writing, there is no record of iodine concentration measurements in harvested C. racemosa from Philippine waters. There is an expected decrease in iodine concentrations from harvested C. racemosa through time. But how fast it decreases and how much of it remains in the seaweed if stored for days is also unknown. This study measured iodine concentration in C. racemosa samples from an area in the Philippines and calculated the daily changes in iodine level concentrations of harvested C. racemosa that were stored. Titration analyses were done every 24 h, with factors such as the algal age, temperature, light, among others, kept constant. Storage conditions were adapted from how local vendors store leftover seaweed merchandise. Results revealed a decrease in iodine levels over time (y = –20.438x + 228.99; R² = 0.8937). The initial concentration (at dry weight) of iodine measured was 196 ppm and dropped to 94.8 ppm on the seventh day. Iodine levels of freshly picked and stored C. racemosa were also compared with the recommended daily iodine intake for humans.
Sargassum polycystum is an economically important seaweed endemic to Southeast Asian waters. Genetic diversity studies conducted for this alga have been based on samples from various areas in the Indo-Pacific region. Here, we examined the phylogenetic patterns of S. polycystum in Eastern Samar, Philippines using the nuclear ribosomal DNA (rDNA) region – including ITS1, 5.8S gene, and ITS2. The phylogenetic and haplotype analyses using these loci indicate that the Eastern Samar samples contain 13 haplotypes. Using the ITS2 region sequences alone (to include other Indo-Pacific samples), we found that the number of Eastern Samar haplotypes was reduced to six, with one common haplotype found in Singapore and Indonesia. Our findings indicate that the genetic diversity of Eastern Samar S. polycystum is substantially higher than previously suggested. Consistent with the previous hypothesis, the populations of S. polycystum in Southeast Asian waters indicate a range expansion. The study could extend our understanding of the genetic diversities of S. polycystum in the Philippines and elsewhere.
This study assessed the phytoplankton composition in Irong-Irong Bay, Western Samar, Philippines. Recurring red tide bans were imposed in this bay due to the elevated levels of saxitoxin that cause Paralytic Shellfish Poisoning primarily produced by Pyrodinium bahamense. Despite the presence of mariculture sites, Irong-Irong Bay has very little or nil data on its overall phytoplankton composition. Monthly field samplings were conducted to observe the phytoplankton community structure during an episode of persistent red tide bans from September–December 2017. Physico- chemical parameters (e.g. temperature, salinity, transparency, pH, nutrient concentration) were measured. A total of 64 species of phytoplankton were observed and counted. The lowest mean cell density of phytoplankton was recorded in the month of November (3.1 x 104 cells/L), whereas December (37 x 104 cells/L) had the highest mean cell density but lowest values for species diversity (H’ = 0.942), richness (Dmn = 0.037), and evenness (J = 0.307). Pseudo-nitzschia dominated in the months of September (3.1 x 104 cells/L) and November (0.43 x 104 cells/L), whereas Skeletonema dominated in the months of October (9.9 x 104 cells/L) and December (29 x 104 cells/L). Pyrodinium bahamense was present in all sampling months with a total mean cell density of 0.08 x 104 cells/L but was never the dominant species. The low cell count relative to other Pyrodinium blooms may be accounted for by the presence of Noctiluca scintillans, its potential predator. Noctiluca scintillans was present in all sampling months. It peaked during the month of November with a mean cell density of 0.32 x 104 cells/L. A significant negative correlation was detected between the cell densities of these two dinoflagellates, providing evidence of the potential interactive relationship between these two species.
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