Now showing 1 - 10 of 32
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    The importance of thermal history: Costs and benefits of heat exposure in a tropical, rocky shore oyster
    (2016-03-01)
    Giomi, Folco
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    Mandaglio, Concetta
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    Han, Guo Dong
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    Dong, Yun Wei
    Although thermal performance is widely recognised to be pivotal in determining species' distributions, assessment of this performance is often based on laboratory-acclimated individuals, neglecting their proximate thermal history. The thermal history of a species sums the evolutionary history and, importantly, the thermal events recently experienced by individuals, including short-term acclimation to environmental variations. Thermal history is perhaps of greatest importance for species inhabiting thermally challenging environments and therefore assumed to be living close to their thermal limits, such as in the tropics. To test the importance of thermal history, the responses of the tropical oyster Isognomon nucleus to short-term differences in thermal environments were investigated. Critical and lethal temperatures and oxygen consumption were improved in oysters that previously experienced elevated air temperatures, and were associated with an enhanced heat shock response, indicating that recent thermal history affects physiological performance as well as inducing short-term acclimation to acute conditions. These responses were, however, associated with tradeoffs in feeding activity, with oysters that experienced elevated temperatures showing reduced energy gain. Recent thermal history, therefore, seems to rapidly invoke physiological mechanisms that enhance survivalofshort-term thermal challenge but also longer term climatic changes and consequently needs to be incorporated into assessments of species' thermal performances.
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    Genetic differentiation and host usage of coral and fire coral-associated barnacles (Cirripedia: Pyrgomatinae and Wanellininae) across the Indian and Pacific Oceans
    (2023-12-01)
    Yu, Meng Chen
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    Tsao, Yao Feng
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    Chan, Benny K.K.
    Using two molecular markers (COI and 12S) collected from seven genera and 20 species of coral associated and fire coral-associated barnacles, we examined whether genetic differentiation occurs between the Indian (total 261 sequences) and Pacific populations (195 sequences). Molecular phylogenetic analysis revealed pyrgomatinid barnacles formed two major sister-clades: the Cantellius clade and the major clade. Most of the species in the Cantellius clade did not show Indo-Pacific genetic divergence, except Cantellius sextus, which formed sister Indian and Pacific Ocean clades. Within the major clade, Darwiniella angularis, Galkinius maculosus, Nobia grandis, and Hiroa stubbingsi were composed of well-supported clades corresponding to the Indian and Pacific Oceans. The fire coral-associated barnacles Wanella milleporae have molecular clades corresponding to the populations in the Red Sea, Phuket waters, and Pacific Ocean. Species delimitation analyses and haplotype network supported the divergence of sequences in some coral barnacle species and fire coral barnacle between Indian and Pacific populations. Indo-Pacific genetic differentiation in some species appears to have resulted from Pleistocene glaciations. Life-history traits, length of larval development period, and host specificity appear can further affect the differentiation of coral barnacles across the Indian and Pacific Oceans.
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    High tolerance of Chaetomorpha sp. to salinity and water temperature enables survival and growth in stagnant waters of central Thailand
    (2015-03-01)
    Tsutsui, Isao
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    Miyoshi, Tatsuo
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    Songphatkaew, Jaruwan
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    Meeanan, Chonlada
    The effects of salinity and water temperature on growth and survival of Chaetomorpha sp., one of the green tidal filamentous algae, were investigated. Field surveys revealed that this alga was abundant throughout the year in stagnant coastal waters of central Thailand. Chaetomorpha sp. was found in salinities of 3.4–90.0 and water temperatures of 20.1–40.9 °C. Chaetomorpha sp. biomass fluctuated between 9.2 and 162 kg dry weight in a saline swamp, without significant differences among seasons. The highest mean specific growth rate of approximately, 60 % day<sup>−1</sup> was observed in laboratory experimental trials at salinities of 20–30 at 30 °C. Salinity and water temperature significantly affected growth of this alga independently and interactively. Based on these results, Chaetomorpha sp. can easily grow, survive and monopolize in stagnant waters where the salinity and temperature greatly fluctuate because of their euryhaline and eurythermal nature as well as their high growth rate.
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    The ocean's surface acidification with increasing atmospheric carbon dioxide and the threats for coral reef calcification
    (2017-04-01)
    Ohde, Shigeru
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    Ouchi, Aaron K.
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    In some tropical, shallow water, coastal areas located around the world, coral cover has been decreasing. This decline in coral reefs is possibly considered to be due to global environmental changes, such as increasing atmospheric carbon dioxide (CO<inf>2</inf>) produced by anthropogenic sources. The extra atmospheric CO<inf>2</inf> is leading to increased seawater surface temperature (SST) as well as surface ocean acidification. This study investigates the relationship between the coral calcification rate and four different controlling factors, seawater pH, aragonite saturation state (O<inf>arag</inf>), temperature, and light intensity. Seawater temperature, pH, and O<inf>arag</inf> are all being directly affected by the increase in atmospheric carbon dioxide occurring. In this study, coral reef observations were performed in Jicchaku, Okinawa, Japan. A medium sized tide-pool (250 X 225 cm<sup>2</sup>, average water depth = 22.6 cm) was utilized for experimental observation periods. Two different types of trials were also run. Normal pH (~8.2) trials were run with no alteration to the seawater. Low pH trials were run after adding ~20 mL of 12M HCl to lower the pH in the tide-pool to a pH of ~7.8. During each trial run, a seawater sample was taken once at the beginning and end of the trial run and once during the trial run. In the laboratory, the samples collected from the field were utilized to determine pH and salinity. Total alkalinity (TA) was determined using the Gran plot method that uses a titration pH curve to determine TA. Seawater O<inf>arag</inf> was calculated using a computer program called CO2SYS. The calcification rate was calculated using the change in TA over the change in time. Data from a daytime normal pH trial at the tide-pool showed TA decreased in relation to time for this trial indicating that calcification was occurring at that time. Data from a nighttime showed TA increased in relation to time for the trial indicating that calcium carbonate dissolution was occurring during nighttime. We also observed that there is a positive relationship between light intensity and the calcification rate suggesting 'light-enhanced' calcification. It could be observed that there is little correlation between the temperature and calcification rate. This suggests that temperature had no effect on changes in the calcification rate for the tide-pool experiments. On the other hand, seawater pH and O<inf>arag</inf> were observed to have a strong influence on the calcification rate. From the field experiments we suggest that coral reef calcification is closely coupled to seawater CO<inf>2</inf> pH and O<inf>arag</inf>, and reduced coral calcification is predicted in the near future when atmospheric CO<inf>2</inf> further increases.
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    Timing metabolic depression: Predicting thermal stress in extreme intertidal environments
    (2020-10-01)
    Hui, Tin Yan
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    Dong, Yun Wei
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    Han, Guo Dong
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    Lau, Sarah L.Y.
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    Cheng, Martin C.F.
    Anticipatory changes in organismal responses, triggered by reliable environmental cues for future conditions, are key to species’ persistence in temporally variable environments. Such responses were tested by measuring the physiological performance of a tropical high-shore oyster in tandem with the temporal predictability of environmental temperature. Heart rate of the oyster increased with environmental temperatures until body temperature reached ∼377C, when a substantial depression occurred (∼60%) before recovery between ∼427 and 477C, after which cardiac function collapsed. The sequential increase, depression, and recovery in cardiac performance aligned with temporal patterns in rock surface temperatures, where the risk of reaching temperatures close to the oysters’ lethal limit accelerates if the rock heats up beyond ∼377C, coinciding closely with the body temperature at which the oysters initiate metabolic depression. The increase in body temperature over a critical threshold serves as an early-warning cue to initiate anticipatory shifts in physiology and energy conservation before severe thermal stress occurs on the shore. Cross-correlating the onset of physiological mechanisms and temporal structures in environmental temperatures, therefore, reveals the potential role of reliable real-time environmental cues for future conditions in driving the evolution of anticipatory responses.
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    Small-scale fishery income impact from artificial reefs in Lang Suan District, Chumphon Province, Thailand
    (2019-06-15)
    Kantavichai, Rapeepan
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    ; ;
    Thongsamui, Ariya
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    Pornratanachotsakul, Maytapon
    To evaluate the economic impact of artificial reefs on small-scale fishing community, we investigated fishers’ income and perception after 3 years of artificial reef deployment in Lang Suan District, Chumphon Province, Thailand. Ninety-two small-scale fishing households were randomly selected for survey. Half of households relied on squid fishing as a major source of income. Squid fishing contributed three-quarter of the total fishery income in this artisanal fishing community. Percentage of households having decrease in fishery income after artificial reef deployment households was 24%. While percentages of households experiencing no change and increase in fishery income were equal at 38%. Ordered logistic regression model identified that fisher characteristics such as family size, sub-district, squid fishery as the major income, fishing time, and fishers’ rest were significant factors affecting changes in fishery income. Differences in fishery income after AR program were estimated by propensity score matching method and showed that annual community fishery income has increased by 6%. Also, most of the respondents showed satisfaction toward artificial reef program in enhancement of marine resources and environment.
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    Living in a growing host: growth pattern and dwelling formation of the scallop Pedum spondyloideum in massive Porites spp. corals
    (2020-07-01)
    Chan, Benny K.K.
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    Tan, James C.H.
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    Pedum spondyloideum is a byssally attached scallop in the Indo-Pacific that lives in deep fan-shaped dwellings within live scleractinian and hydrozoan corals, with the ventral edges of the scallops’ valves protruding slightly from the dwellings. Juvenile scallops have rounded, oval shells and live in shallow depressions. Complete scallop dwellings are formed by the growth of the host and allometric growth of the scallop, and by chemical and physical interactions between the scallop and its host. Scallops were extracted intact from their dwellings within massive corals in the genus Porites in Thailand (7°36′32″ N, 98°21′55″ E; in May 2019) and Malaysia (2°45′17″ N, 104°13′30″ E; in November 2019) to examine the relationship between shell height (SH) and shell width (SW). The slope of the regression of SH on SW within the first 2 years of settlement was 0.79–0.9, indicating that SW increased slightly faster than SH during this period. As the scallop grew further, the slope of the SH on SW was 1.29–1.54, indicating that SH increased faster than SW. A histological study on scallop pallial tissue, including the tentacles, and SEM observations of the dwelling walls suggested that the scallop has secretions that damage coral tissue and widen the dwelling during growth. Thus, the distinctive fan-shaped dwellings of the adult scallops are caused by a combination of allometric scallop growth and erosion of the host tissue and dwelling walls.
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    Effects of different nitrogen, phosphorus, and iron concentrations and salinity on lipid production in newly isolated strain of the tropical green microalga, Scenedesmus dimorphus KMITL
    (2013-06-01) ; ;
    Choochote, Sakchai
    The fatty acid composition, the effect of different concentrations of nitrogen (16.5-344 mg L<sup>-1</sup>), phosphorus (9-45 mg L<sup>-1</sup>), iron (9-45 mg L<sup>-1</sup>) and salinity levels (0-20 psu) on lipid production in the green microalga Scenedesmus dimorphus KMITL, a new strain isolated from a tropical country, Thailand, were studied. The alga was isolated from a freshwater fish pond, and cultured in Chlorella medium by varying one parameter at a time. The main fatty acid composition of this strain was C16-C18 (97.52 %) fatty acids. A high lipid content was observed in conditions of 16.5 mg L<sup>-1</sup>-N, or 22 mg L<sup>-1</sup>-P, or 45 mg L<sup>-1</sup>-Fe, or 5 psu salinity, which accumulated lipids to 20.3 ± 0.4, 19.4 ± 0.2, 24.7 ± 0.5, and 14.3 ± 0.2 % of algal biomass, respectively. Increasing lipid content and lipid productivity was noted when the alga was cultured under high iron concentration and high salinity, as well as under reduced phosphorus conditions, whereas nitrogen limitation only resulted in an increased lipid content. © 2012 Springer Science+Business Media Dordrecht.
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    Biodiversity and host specificity of sponge-associated barnacles (Cirripedia: Thoracica) in Thailand
    (2020-11-01)
    Yu, Meng Chen
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    Chan, Benny K.K.
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    Kolbasov, Gregory A.
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    We examined the diversity and host use of sponge-associated barnacles of Thailand (Andaman Sea and the Gulf of Thailand) using a combined morphological and molecular approach. Eight barnacle species (including two new species) were collected from 12 host sponges. Host-specific barnacle species includes Acasta lappa sp. nov., which exclusively inhabits the sponge Mycale sp. Acasta milkae sp. nov. was only collected from the sponge Callyspongia cf. diffusa (Ridley, 1884). Multatria filigranus (Broch, 1916) were found in the encrusting soft sponges Monanchora unguiculata (Dendy, 1922) and Clathria sp. Pyrgospongia stellula (Rosell, 1975) inhabits the sponges Spheciospongia vagabunda (Ridley, 1884). Generalist barnacle species includes Euacsta ctenodentia (Rosell, 1972), E. porata (Nilsson-Cantell, 1921), E. zuiho (Hiro, 1936), and Acasta cyathus Darwin, 1854, which inhabit a wide range of sponges with various textures.
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    Co-culture with Chaetomorpha sp. enhanced growth performance and reduced feed conversion ratio of the giant tiger prawn, Penaeus monodon
    (2015-09-08)
    Tsutsui, Isao
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    Songphatkaew, Jaruwan
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    Meeanan, Chonlada
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    Sukchai, Halethichanok
    The increase in global demand for fishery products has led to a fivefold increase in aquaculture production since 1990. Commercial feed is the highest production cost in intensive aquaculture, and residual commercial feed leads to eutrophication; hence it is important to find a low-cost alternative that has less environmental impact. We investigate the use of the filamentous green algae, Chaetomorpha sp., as a raw feed for giant tiger prawns. The giant tiger prawn, Penaeus monodon was grown in monoculture, and in co-culture with Chaetomorpha sp. to investigate the potential benefits of co-culturing. Five 20-day-old giant tiger prawn juveniles were released in 70-L monoculture and co-culture tanks, and the specific growth rate (SGR) and feed conversion ratio (FCR) were measured after 10 weeks. The final mean body weight of co-cultured prawns was approximately 50 % heavier than that of monocultured prawns. The SGR in co-culture tanks was 4.79 ± 0.08 % day<sup>−1</sup>, which was higher than that in monoculture tanks (4.14 ± 0.27 % day<sup>−1</sup>). The FCR was 38.9 % lower in co-culture than in monoculture tanks. The protein content of Chaetomorpha sp. obtained from proximate analysis was almost the same or a little lower than other filamentous green seaweeds; however, the Chaetomorpha sp. has higher fiber and gross energy. These results show that Chaetomorpha sp. has potential for reducing feed costs in prawn intensive aquaculture through co-culturing.