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National Committee on Marine Sciences (NCMS)

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AGROVOC Keyword: search.filters.agrovoc.algal bloomsGeographic name: search.filters.geographicname.Samar

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    Connections and clustering of Paralytic Shellfish Toxin events among coastal embayments in an archipelago partly mediated by advection
    Punongbayan, Andalus T.; Wang, Ysabel D.; Villanoy, Cesar L.; Yñiguez, Aletta T. (Elsevier, 2022-01)
    The potential for advection to influence harmful algal bloom (HAB) spread in adjacent embayments and islands has not been investigated in the Philippines as previous studies have focused on HAB dynamics within specific embayments. Advection of HABs may be relevant in the Samar-Leyte region where adjacent sites are subject to recurrent blooms of Pyrodinium bahamense. We used different analyses to extract the potential role of advection in blooms in the region. First, we used Bayesian and information theoretic approaches applied to historical data on shellfish bans to quantify spatial dependencies in HAB occurrences between sites. Then, to determine whether such dependencies are related to circulation patterns in the region, we analyzed connectivity using a hydrodynamic model coupled with a conservative tracer-based HAB model. The Bayesian network showed that in 7 out of 11 sites, the probability of a shellfish ban depended on the state of an adjacent site. Site pairs with direct dependence relations also shared relatively high similarity in HAB occurrences over time. In the modelled network, bans tend to occur sequentially, spreading from a few sites with relatively high probabilities for ban events. A subset of sites (sources) were found to be informative of future HAB event probabilities in other sites (destinations) over time lags that are generally longer the farther the destination. Modelled surface advection showed high connectivity strengths between sources and destinations associated with circulation features, e.g., an anticyclonic current in Leyte, wind-driven coastal current in western Samar, and tidally-driven flow in the shallow embayments in southwest Samar. High connectivities were correlated with direct dependence relations in the Bayesian network. Connectivity explained up to about 1/3 of the variance in statistical dependencies between ban signals. Our results show that Paralytic Shellfish Toxin events within this region can be due to advection of blooms originating from nearby areas rather than localized cyst dynamics within an embayment. Particular sites were also identified as potential indicator sites within spatial clusters for monitoring since they are typically where blooms originate and spread from.
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    3 bays in Samar placed on red tide alert
    Gabieta, Joey (Philippine Daily Inquirer, Inc., 2023-10-08)
    The Bureau of Fisheries and Aquatic Resources (BFAR) has warned the public not to consume shellfish products taken from three bays on Samar Island where the red tide toxin was detected. “To safeguard human lives, we are issuing this warning as a precautionary advice to the public to refrain from gathering, selling, and eating all types of shellfish and Acetes sp. locally known as ‘alamang’ or ‘hipon’ from these bays,” said BFAR in its local shellfish bulletin on Friday. According to BFAR, affected by the red tide toxin were the Irong-Irong Bay in Catbalogan City, Samar province