UPV Digital RepositoryUPV-DRUniversity of the Philippines Visayas
 

Masters Theses

Permanent URI for this collectionhttps://hdl.handle.net/20.500.14583/12

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Start date: 2010SDG: search.filters.sdg.SDG 3 - Good health and well-being

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    Removal of Harmful Algal Bloom (HAB)-forming organisms using ball clay: Factors and effects of clay addition
    Rivera, Peter Paolo L. (Marine Science Institute, College of Science, University of the Philippines Visayas, 2015-05)
    Global concern for Harmful Algal Blooms (HABs) has increased due to their frequency of occurrence and associated negative health and economic effects. Control measures for HABs/red tides have been developed to alleviate their effects in the marine and coastal environments. The use of clays and modified sands/sediments to remove/control HABs is one of the promising and attractive direct control options for areas with persistent HAB problems. However, factors such as pH and ionic strength and mechanisms and kinetics of algal removal through clay addition/spreading are not fully understood. This study examined the effect of different pH levels and varying ionic strength on the removal efficiency (RE) of ball clay on toxic dinoflagellates: Pyrodinium bahamense var. compression, Gymnodinium catenation, and Alexandrium tamarense complex. High REs by ball clay were observed on Pyrodinium and Gymnodinium. On the other hand, only minimal removal was observed with Alexandrium. This implies that ball clay has a varying affinity towards different HAB species. Removal was also found to be highly dependent on bloom stages and varies for a given target species. RE of ball clay for the three test organisms increases as the pH of the solution decreases (83.1% for Pyrodinium, 81.2% for Gymnodinium, 89.4% for Alexandrium at pH 6. Results from this study show that with increasing salinity and/or ionic strength, RE also increases (82.7% for Pyrodinium, 88% for Gymnodinium, and 79.5% for Alexandrium at ionic strength of 1.0). Results show that changing the pH and ionic strength influenced the zeta potential (electrokinetic potential) of both the toxic algal cells and ball clay, hence affecting algal flocculation and leading to the effective removal of the algal cells. Microalgal cells are negatively charged in growth media at pH values (7-9 for most algal species) typical for growth and the charges cause adjacent cells to repel each other and remain suspended in the medium. The negative charges apparently derived from the water and dissociation of functional groups on algal cell walls, and vary among different algal species. The changes in pH influence the degree of surface dissociation, thus affecting the cell surface charge. The zeta potential of ball clay as a function of varying ionic strength and salt concentrations showed that zeta potential decreases (more negative) with increasing ionic strength from 0 to 1 and/or salinity from 0 to 36 ppt (in contrast to algal cells). When the ionic strength of the solution is increased, the charge potential difference between clay particles and algal cells also increases, thereby increasing the affinity between the two particles. Cell death and lysis were evident within the suspended and settled clay matrix from direct microscopic observation. The cells appeared moribund, and stained cytoplasmic material could be seen leaking into the medium. Cell death may have been due to the direct physical contact between the cells and clay particles. Cell lysis occurred over a 1–2-hour period in single-species cultures of HAB organisms. Measurement of fluorescence properties through confocal laser scanning microscopy (CLSM) of microalgae has proven that a rapid and sensitive ecotoxicity method could be developed where the motility and viability of cells flocculated with clay could be examined. The substantial release of the nucleotides and intracellular materials from the algal cells indicates the expulsion of the thecal plates and cell membrane leading to the disintegration of the algal cells upon clay addition. Cellular damage was further confirmed by metabolic imaging through an esterase activity assay. Esterase activity in control and treated cells was studied by fluorescence imaging after staining with fluorescence diacetate (FDA), a technique to probe cell membrane integrity and cell viability. FDA-positive cells decreased through time until 24-hour upon exposure to ball clay. Future studies are needed to investigate the actual mechanism of how clay induces cell lysis or mortality. Cell mortality may be due to natural senescence or programmed cell death (PCD) under stress-promoting conditions and not related to any chemical or physical interaction between the clay and the algal cells. It is also interesting to look at the possible formation of ecdysal and temporary pellicle cysts upon clay treatment. The possible formation of temporary cysts by HAB cells may play a role in bloom regrowth. The encystment and excystment may enable HAB cells to escape entrapment, allowing a bloom to reform.
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    Survival of nursery-reared juvenile milkfish, Chanos-chanos at different transport density, temperature and anaesthetic combinations
    Failaman, Alan N. (University of the Philippines Visayas, 2020-06)
    Experiments were conducted to optimize transport conditions of nursery cultured juvenile milkfish in a closed plastic bag based transport system. In the first experiment combined effects of temperature (25-27°C, 20-22°C and 15-17°C) and anesthetics (2-phenoxyethanol at 200 mgL-1 for initial sedation and 80 mgL-1 for transport sedation) on oxygen consumption and survival ofjuvenile milkfish, Chanos chanos, were evaluated. Another experiment was conducted to optimize transport conditions at fish densities of 200, 400, 600, 800 and 1000 gL-1 for 4, 8, 12,16 and 20 hour duration. The study showed no significant difference on oxygen consumption rates ofmilkfishjuveniles subjected to various water temperature range and anesthetic combinations. Temperature range of 20 to 22°C in combination with anaesthetic (2-phenoxyethanol) application was the best condition for long duration confinement of milkfish juvenile in closed plastic transport bags. The study established the optimum juvenile milkfish transport density and the effective transport duration. With anaesthetic application (2-phenoxyethanol), juvenile milkfish density of 600 gL-1 is effective for 20 hours oftransport duration, 800 gL-1 for 8 hours oftransport duration and 1000 gL-1 effective for 4 hours transport duration. These results provide a practical protocol for the transport of juvenile milkfish from the nursery culture area to the grow-out production area.
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    Characterization of the egg masses of Wedge Sea Hare, Dollabella auricularia (Lightfoot, 1786) from Danao-Carmen Cove, Cebu, Philippines
    Pepito, Ador R. (University of the Philippines Visayas, 2016-06)
    The egg mass locally, known as "lukot” of the wedge sea hare Dolabella auricularia is considered as one of the seafood products in the Visayas region. It is traditionally consumed as raw or an added ingredient to a soup made from fish or shellfish. Although there have been no reported incidence of food poisoning due to the consumption of these egg masses, a preliminary study revealed the potential presence of some toxic substances in the samples. Likewise, no detailed study on the chemical characteristics of these egg masses has been reported. Hence, this study was conducted to determine the toxicity potential and the effect of the post harvest treatment on the chemical quality of the egg mass. Different post harvest treatments were employed in this study includes: acidified, boiled and the combination of the two. Results show low toxicity potentials in all samples both treated and untreated. No significant differences among all treatments on the lowering of the toxicity potentials of the egg mass were observed. This low toxicity potential could be attributed to the effect of seasonal variation in the sample and its habitat. Different post harvest treatments, on the other hand, reveal different effects on the chemical characteristics of the egg masses. Acidified and the combination of acidified and boiled samples show high protein, carbohydrates and ash content. Boiling of samples resulted to an increase in moisture retention and potassium while acidified samples resulted in high calcium and potassium. Raw or fresh samples show high total fat, ash, sodium and zinc content. In terms of amino acid profile, the egg masses have six (6) essential, nine (9) non-essential and eight (8) other amino acid components. These results indicate that the egg masses of the wedge sea hare can be considered as a good potential exotic nutritious food commodity from marine environment. Its safety, however, largely depends on the condition of the environment where these egg masses are harvested.