Browsing by Author "SITI AISHAH ABDULLAH"

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    EFFECTS OF FEEDING PRESSURE AND LOW-LIGHT STRESS ON THE PERFORMANCE OF ANTIHERBIVORE DEFENSES IN THE TWO RED ALGAE Gracilaria edulis AND Gracilaria salicomia FROM THE MALAY PENINSULAR
    (Journal of Sustainability Science and Management, 2009) SHUKRI ARSAD; CORVIN EIDENS; MARK. LENZ; SITI AISHAH ABDULLAH
    The objective of this study was to test for the inducibility of an anti-feeding defense in two red macroalgal from the coast of the Malay Peninsular as a response to grazing pressure. Whether the defense capacity in these seaweeds is generally impaired by low-light stress was also investigated. Aquaria with blackened walls connected to a :flow-through water system were used as Experimental Units (EUs). Different light regimes were established using layers of black gauze material and clear perspex lids, mounted on top ofthe EU. The gauze allowed the stepwise reduction of ambient light. Six different light levels with eight replicates each were realised. The growth rates of algal exposed to different light levels were calculated using a linear regression analysis. Using outdoor mesocosm facilities, three fully-factorial experiments were realised during which low-light stress on different algae-grazer combinations was induced: 1) the red algae Gracilaria edulis with the sea hare Aplysia sp., 2) G. edulis with the abalone Haliotis diversicolor, and 3) Gracilaria salicornia with H diversicolor. For each combination, 48 aquaria were used, while in a control group of another 48 tanks, algae were kept in the absence ofherbivores. Following lowlight and feeding-stress induction, herbivore consumption on algal material was assessed in feeding assays with living thalli fragments. Negative effects of light reduction on algal growth rates was observed in both experiments with G. edulis and in one trial with G. salicornia, while general effects of low-light stress on seaweed palatability were absent in our study. By contrast, for some herbivore-algal combinations, significant differences in consumption were detected on previouslygrazed and ungrazed algal material, that indicates the presence of an inducible defense. G. edulis and G. salicornia produced defenses when exposed to grazing by the gastropod Aplysia sp. and H diversicolor, respectively. In contrast, G. edulis showed no response to H diversicolor. Our findings show that inducible defenses generally exist in the two investigated Gracilaria species, but vary with the identity ofherbivores. Surprisingly, algal palatability was not affected throughout all lowlight regimes, contrasting the widespread notion that defensive traits in seaweeds are dependent on metabolic energy. Thus, it appears that low-light stress effects play only a minor role on the performance of antiherbivore defenses in these two red algae.
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    ExPERIMENTAL AND FIELD STUDY ON ACCUMULATION OF HEAVY METALS IN SEAGRASSES (Halodule pinifolia and Halophila minor) IN SETIU WETLAND, TERENGGANU
    (Journal of Sustainability Science and Management, 2008) SYARIFAH NOORMAISARAH TUAN BESAR; NOOR AZHAR MOHAMED SHAZILI; SITI AISHAH ABDULLAH
    The aims of this study were: (i) to determine the content of copper and cadmium into seagrass Halodule pinifolia and Halophila minor from the Setiu Wetland and Setiu River estuary, Terengganu and (ii) to study the bioaccumulation response of the seagrass towards the metals. The contents of the two metals in leaves and root-rhizomes of the seagrasses collected from the feld study samples were determined. in laboratory experiments, the two seagrass were exposed to sediments spiked with four different concentrations of copper (56.44 µg/g, 112.87 µg/g, 225.74 µg/g and 451.49 µg/g) or cadmium (36.00 µg/g, 72.00 µg/g, 144.00 µg/g and 288.00 µg/g). The exposure period was for 8 weeks during which plants were sampled weekly and the metal concentrations in leaves and root-rhizomes determined. The content of heavy metals was measured by aaS. Pearson Correlation were used to determine the relationship between the accumulation of heavy metals in root-rhizomes and leaves. in the exposure experiments, Cu and Cd were bioaccumulated, with tissue concentration generally increased with duration of exposure and increase in sediment metal concentrations. Metal concentrations in root-rhizomes were higher than in leaves for both species. in Halodule pinifolia, the mean copper in root-rhizomes and leaves were 120.86 ± 6.79 µg/g and 96.99 ± 8.58 µg/g respectively while the mean cadmium concentration in root-rhizomes was 38.40 ± 4.71 µg/g and in leaves was 36.08 ± 3.21 µg/g. In Halophila minor, the mean copper concentration in root-rhizomes and leaves were 49.53 ± 7.67 µg/g and 35.40 ± 6.52 µg/g respectively. The mean cadmium concentration in rootrhizomes was 30.34 ± 3.15 µg/g and in leaves was 29.71 ± 2.64 µg/g. Generally, the metals in rootrhizomes showed strong correlation with the metals in leaves. Halodule pinifolia and Halophila minor exposed to high concentrations of copper were dead in week 4 and 5 respectively, while exposure to high concentrations of cadmium resulted in death of plants in week 4. oxygen produced by both seagrass species also began showed negative values in week 4. For the feld study, the highest concentrations of Cd and Cu in Halodule pinifolia and Halophila minor were found for the month of October 2004 and month of November respectively.