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Chou W.-C.,National Taiwan Ocean University | Gong G.-C.,National Taiwan Ocean University | Gong G.-C.,Taiwan Ocean Research Institute | Hung C.-C.,National University of Kaohsiung | Wu Y.-H.,National Taiwan Ocean University
Biogeosciences | Year: 2013

To assess the impact of rising atmospheric CO2 and eutrophication on the carbonate chemistry of the East China Sea shelf waters, saturation states (Ω) for two important biologically relevant carbonate minerals-calcite (Ωc) and aragonite (Ωa)-were calculated throughout the water column from dissolved inorganic carbon (DIC) and total alkalinity (TA) data collected in spring and summer of 2009. Results show that the highest Ωc (∼9.0) and Ωa (∼5.8) values were found in surface water of the Changjiang plume area in summer, whereas the lowest values (Ωc Combining double low line ∼2.7 and Ωa Combining double low line ∼1.7) were concurrently observed in the bottom water of the same area. This divergent behavior of saturation states in surface and bottom waters was driven by intensive biological production and strong stratification of the water column. The high rate of phytoplankton production, stimulated by the enormous nutrient discharge from the Changjiang, acts to decrease the ratio of DIC to TA, and thereby increases Ω values. In contrast, remineralization of organic matter in the bottom water acts to increase the DIC to TA ratio, and thus decreases Ω values. The projected result shows that continued increases of atmospheric CO2 under the IS92a emission scenario will decrease Ω values by 40-50% by the end of this century, but both the surface and bottom waters will remain supersaturated with respect to calcite and aragonite. Nevertheless, superimposed on such Ω decrease is the increasing eutrophication, which would mitigate or enhance the Ω decline caused by anthropogenic CO2 uptake in surface and bottom waters, respectively. Our simulation reveals that, under the combined impact of eutrophication and augmentation of atmospheric CO2, the bottom water of the Changjiang plume area will become undersaturated with respect to aragonite (Ωa Combining double low line ∼0.8) by the end of this century, which would threaten the health of the benthic ecosystem. © 2013 Author(s).

Shih H.-T.,National Chung Hsing University | Ng P.K.L.,National University of Singapore | Liu M.-Y.,Taiwan Ocean Research Institute
Raffles Bulletin of Zoology | Year: 2013

Fiddler crabs (genus Uca) with broad-fronts (BF) belong to a group of small-sized species with complex behaviors and have been suggested to be more "advanced" compared to the narrow-fronted species groups. Three Indo-West Pacific subgenera, Austruca Bott, 1973, Cranuca Beinlich & von Hagen, 2006, and Pa raleptuca Bott, 1973, are reappraised using two mitochondrial (16S rRNA and cytochrome oxidase I) and one nuclear (28S rRNA) markers. The phylogenetic analyses show that the three clades agree relatively well with the three subgenera as currently defined. Our study confirms that the Indo-West Pacific BF species that had been placed with the American Celuca sensu Crane, 1975, are genetically unsupported, and should be classified in Austruca, together with U. sindensis (Alcock, 1900) (currently in Paraleptuca). Austruca now contains 11 species. Cranuca, a subgenus established with only U. inversa (Hoffmann, 1874), is supported by its monophyly and its significant distance from other subgenera. In addition, Paraleptuca (= Amphiuca Crane, 1975) is restricted for U. chlorophthalmus (H. Milne Edwards, 1837), U. crassipes (White, 1847) and U. splendida (Stimpson, 1858). The two American BF subgenera, Minuca Bott, 1954 and Leptuca Bott, 1973, form a mixed clade and further studies will be needed to clarify their validities. © National University of Singapore.

Chiou J.-S.,National Center for Research on Earthquake Engineering | Chiang C.-H.,National Center for Research on Earthquake Engineering | Yang H.-H.,Taiwan Ocean Research Institute | Hsu S.-Y.,National Center for Research on Earthquake Engineering
Soil Dynamics and Earthquake Engineering | Year: 2011

This study proposes a procedure for developing seismic fragility curves for a pile-supported wharf. A typical pile-supported wharf, as commonly used in the ports of Taiwan, is chosen for demonstration. For a structural model of the wharf, the deck is modeled by shell elements and the Winkler model is used for the pile-soil system, in which the piles and soils are represented by beam elements and springs, respectively. A pushover analysis with lateral loads distributed according to the fundamental modal shape of the wharf structure is conducted to deduce the capacity curve of the wharf. The procedure for developing fragility curves can be explicitly performed using the spreadsheet platform in Microsoft EXCEL. First, quantitative criteria for damage states are established from the sequence of development of plastic zones. Then a nonlinear static procedure called the Spectrum Capacity Method (CSM) is used to efficiently construct a response matrix of the wharf to 24 earthquake events with differing levels of peak ground acceleration (PGA). Based on the damage criteria and the response matrix, the fragility curves of the wharf can be thus constructed through simple statistical analysis. Shifted lognormal cumulative distribution functions are also employed to better approximate the fragility curves for practical applications. © 2011 Elsevier Ltd.

Tsai A.Y.,National Taiwan Ocean University | Gong G.-C.,National Taiwan Ocean University | Gong G.-C.,Taiwan Ocean Research Institute | Hung J.,National Taiwan Ocean University
Biogeosciences | Year: 2013

Since viral lysis and nanoflagellate grazing differ in their impact on the aquatic food web, it is important to assess the relative importance of both bacterial mortality factors. In this study, an adapted version of the modified dilution method was applied to simultaneously estimate the impact of both virus and nanoflagellate grazing on the mortality of heterotrophic bacteria. A series of experiments was conducted monthly from April to December 2011 and April to October 2012. The growth rates of bacteria we measured ranged from 0.078 h -1 (April 2011) to 0.42 h-1 (September 2011), indicating that temperature can be important in controlling the seasonal variations of bacterial growth. Furthermore, it appeared that seasonal changes in nanoflagellate grazing and viral lysis could account for 34% to 68% and 13% to 138% of the daily removal of bacterial production, respectively.We suggest that nanoflagellate grazing might play a key role in controlling bacterial biomass and might exceed the impact of viral lysis during the summer period (July to August) because of the higher abundance of nanoflagellates at that time. Viral lysis, on the other hand, was identified as the main cause of bacterial mortality between September and December. Based on these findings in this study, the seasonal variations in bacterial abundance we observed can be explained by a scenario in which both growth rates and loss rates (grazing+viral lysis) influence the dynamics of the bacteria community. © Author(s) 2013.

Tsai Y.,National Taiwan University | Chern C.-S.,National Taiwan University | Jan S.,Taiwan Ocean Research Institute | Wang J.,National Taiwan University
Journal of Marine Research | Year: 2013

The ocean response to the passage of Typhoon Morakot (2009) near the continental shelf of the East China Sea off northeastern Taiwan was evaluated using a numerical ocean model to clarify how the permanent upwelling feature in this region was changed during this storm event. Several studies have identified the presence of the Kuroshio subsurface water in this Cold Dome region, which results from the interactions among the monsoon, the Kuroshio and the shelf topography. This study shows how tropical cyclone Morakot's passage quickly disturbed the circulation around Taiwan and induced a short-period intrusion of the Kuroshio water onto the continental shelf. The intrusion began during the second half of the forced period and lasted for approximately two days. The upwelling and northward flow were greatly enhanced during this period, allowing the subsurface water from the upstream Kuroshio to be transported onto the shelf and to reach the Cold Dome. The intrusion-induced cold anomaly along the north coast of Taiwan was much more significant than what can be achieved by local vertical mixing. The cold anomaly later formed an eddy, which gradually propagated with the Kuroshio to the northeast. © 2013 Yaling Tsai, Ching-Sheng Chern, Sen Jan and Joe Wang.

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