Time filter

Source Type

Lui H.-K.,National Sun Yat - sen University | Lui H.-K.,Taiwan Ocean Research Institute | Chen C.-T.A.,National Sun Yat - sen University
Limnology and Oceanography: Methods | Year: 2017

Seawater pH is frequently measured at 25°C (pH25), and can be converted thermodynamically to pH at the in situ temperature (T), (pHinsitu) using an additional carbonate chemistry parameter, which is the total alkalinity (TA), dissolved inorganic carbon (DIC), or the partial pressure of CO2 (pCO2) of seawater. Although rates of temporal change of pHinsitu (βpHinsitu) and pH25 (βpH25) are both extensively used in studies of ocean acidification, the difference between βpHinsitu and βpH25 has not yet been quantified. This study deducts from 816 sets of data of the surface oceans over wide ranges of T (1-31°C) from six time series to reveal that the difference between calculated pHinsitu and pH25 is a1 (T-25°C), where a1 is a nearly constant of 20.0151 pH unit °C-1. We illustrate that βpHinsitu equals (βpH25+a1βT), where βT is the rate of temporal change of T. We further show that uneven distributions of sampling points significantly widen the difference between βpHinsitu and βpH25, making the degree of ocean acidification unclear. Distributions of a1 values are modeled for the surfaces of the global oceans at various pCO2 levels, and they closely match the observations from the studied time series. Without the use of an additional carbonate chemistry parameter, the pHinsitu and pH25, as well as βpHinsitu and βpH25 can now be converted into each other using only T, facilitating the study of the changing carbonate chemistry of seawater under the influences of increasing atmospheric CO2 concentration. © 2017 Association for the Sciences of Limnology and Oceanography.

Young S.-S.,National Hsinchu University of Education | Ni M.-H.,Hsinchu Municipal Hsinchu Elementary School | Liu M.-Y.,Taiwan Ocean Research Institute
Zoological Studies | Year: 2012

There is some controversy regarding the traditional taxonomy of the Simocephalus sensu stricto species group. We conducted molecular and morphometric analyses to differentiate the 3 species from this group found in Taiwan: S. vetulus (O.F. Müller, 1776), S. vetuloides Sars, 1898, and S. mixtus Sars, 1903. The landmark method was employed, followed by a transfer into 24 characteristic values for a principal component analysis (PCA), the results of which indicated morphometric overlap among these species. The dorsal angle, brood size, and body length were smallest in S. vetulus, medium in S. vetuloides, and largest in S. mixtus. In the Simocephalus sensu stricto group from Taiwan, the dorsal angle and body length were significantly correlated with brood size in a quadratic manner. In the molecular analysis, 98 specimens of Simocephalus were used, and the 641-bp mitochondrial DNA cytochrome oxidase subunit 1 sequence was employed as a marker to analyze the genetics of S. vetulus, S. vetuloides, S. mixtus, S. serrulatus (Koch, 1841), and S. heilongjiangensis Shi and Shi, 1994. Simocephalus vetulus, S. vetuloides, and S. mixtus shared several haplotypes, and the interspecific genetic distance was merely 0.00671-0.00785, which is within the range of intraspecific differences. We concluded that S. vetulus, S. vetuloides, and S. mixtus in Taiwan belong to the same species and should be treated as S. cf. vetulus. The number of species of Simocephalus in Taiwan is thus reduced to 3: S. cf. vetulus, S. serrulatus, and S. heilongjiangensis.

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).

Hsu S.-K.,National Central University | Yeh Y.-C.,Taiwan Ocean Research Institute | Sibuet J.-C.,National Central University | Doo W.-B.,National Central University | Tsai C.-H.,National Central University
Earth and Planetary Science Letters | Year: 2013

In April 1771, a subduction earthquake generated a great tsunami that struck the south Ryukyu islands and killed ~12,000 people, whereas its mechanism is still enigmatic (Nakata and Kawana, 1995; Nakamura, 2006; Matsumoto et al., 2009). In this paper, we show its probable source on a mega-splay fault system existing along the southern Ryukyu forearc. Analyses of deep multi-channel seismic reflection profiles indicate that the mega-splay fault system is rising from the summit of a ~1. km high ridge situated at a ~5° landward dipping plate interface. An outer ridge marks the seafloor outcrop of the splay fault system and separates the landward inner wedge and the oceanward outer wedge. The inner wedge is uplifting and exhibits widespread normal faulting while the outer wedge shows folded structures. The mega-splay fault system is parallel to the Ryukyu Trench east of 125.5°E and is estimated to be ~450. km long. The origin of this south Ryukyu mega-splay fault system is ascribed to a resistant subduction of the elevated transverse ridges associated with the subducting portion of the trench-parallel Luzon-Okinawa Fracture Zone. In contrast, no similar splay fault is found west of 125.5°E where the oblique subduction has produced large shear zones along the south Ryukyu forearc. We infer that a thrust earthquake linked to the mega-splay fault system is responsible for the south Ryukyu tsunami. However, another possible scenario of generating a large tsunami affecting the south Ryukyu islands is that the subducted ridge in the western end of the mega-splay fault system nucleated a large earthquake and simultaneously triggered the ~100. km long E-W trending strike-slip fault west of 125.5°E and induced a southward-dipping tsunami-genic subsidence. In any case, after a quiescence of ~241. yr, a large earthquake and tsunami is anticipated in the south Ryukyu forearc in the near future. © 2012 Elsevier B.V.

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.

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.

Chou W.-C.,National Taiwan Ocean University | Gong G.-C.,National Taiwan Ocean University | Gong G.-C.,Taiwan Ocean Research Institute | Cai W.-J.,University of Delaware | Tseng C.-M.,National Taiwan University
Biogeosciences | Year: 2013

Model studies suggested that human-induced increase in nutrient load may have stimulated primary production and thus enhanced the CO2 uptake capacity in the coastal ocean. In this study, we investigated the seasonal variations of the surface water's partial pressure of CO2 (pCO 2 sw) in the highly human-impacted Changjiang-East China Sea system between 2008 and 2011. The seasonality of pCO2 sw has large spatial variations, with the largest extreme of 170 ± 75 μatm on the inner shelf near the Changjiang Estuary (from 271 ± 55 μatm in summer to 441 ± 51 μatm in autumn) and the weakest extreme of 53 ± 20 μatm on the outer shelf (from 328 ± 9 μatm in winter to 381 ± 18 μatm in summer). During the summer period, stronger stratification and biological production driven by the eutrophic Changjiang plume results in a very low dissolved inorganic carbon (DIC) in surface waters and a very high DIC in bottom waters of the inner shelf, with the latter returning high DIC to the surface water during the mixed period. Interestingly, a comparison with historical data shows that the average pCO2 sw on the inner shelf near the Changjiang Estuary has decreased notably during summer, but has increased during autumn and winter from the 1990s to the 2000s. We suggest that this decadal change is associated with recently increased eutrophication. This would increase both the photosynthetic removal of DIC in surface waters and the respiratory release of DIC in bottom waters during summertime, thereby returning more DIC to the surface during the subsequent mixing seasons and/or episodic extreme weather events (e.g., typhoons). Our finding demonstrates that increasing anthropogenic nutrient delivery from a large river may enhance the sequestration capacity of CO 2 in summer but may reduce it in autumn and winter. Consequently, the coastal ocean may not necessarily take up more atmospheric CO2 in response to increasing eutrophication, and the net effect largely depends on the relative timescale of air-sea gas exchange and offshore transport of the shelf water. Finally, the case we report for the Changjiang system may have general ramifications for other eutrophic coastal oceans. © Author(s) 2013.

Lee I.H.,National Sun Yat - sen University | Wang Y.-H.,National Sun Yat - sen University | Yang Y.,Taiwan Ocean Research Institute | Wang D.-P.,State University of New York at Stony Brook
Journal of Geophysical Research: Oceans | Year: 2012

The northeast South China Sea is perhaps the largest internal tide energy source in the world. The temporal variability of internal tides was investigated on the basis of 8-month moored acoustic Doppler current profiler observations on the continental slope at the Dongsha Plateau. The daily amplitude and phase of diurnal and semidiurnal internal tides were determined from complex demodulation, and the dominant spatial and temporal patterns were extracted with empirical orthogonal function (EOF) analysis. The EOF modal structures showed good agreement with the normal mode solution, although vertical phase propagations were apparent. The first semidiurnal EOF mode corresponded to the first normal mode, and the first two diurnal EOF modes corresponded to the second and third normal modes, respectively. The modal structure and energy flux also were consistent with previous observations near the shelf break from the Asian Seas International Acoustic Experiment. On the other hand, the amplitudes of diurnal and semidiurnal EOF modes both indicated large irregular fortnightly variations that were not phase locked (incoherent) with astronomical forcing. The study highlighted the importance of incoherent internal tidal motion, which accounted for about three fourths of the observed tidal energy. Copyright 2012 by the American Geophysical Union.

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.

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.

Loading Taiwan Ocean Research Institute collaborators
Loading Taiwan Ocean Research Institute collaborators