Southwestern Taiwan Research Articles

Seismic imaging of the Formosa Ridge cold seep site offshore of southwestern Taiwan

Multi-scale reflection seismic data, from deep-penetration to high-resolution, have been analyzed and integrated with near-surface geophysical and geochemical data to investigate the structures and gas hydrate system of the Formosa Ridge offshore of southwestern Taiwan. In 2007, dense and large chemosynthetic communities were discovered on top of the Formosa Ridge at water depth of 1125 m by the ROV Hyper-Dolphin. A continuous and strong BSR has been observed on seismic profiles from 300 to 500 ms two-way-travel-time below the seafloor of this ridge. Sedimentary strata of the Formosa Ridge are generally flat lying which suggests that this ridge was formed by submarine erosion processes of down-slope canyon development. In addition, some sediment waves and mass wasting features are present on the ridge. Beneath the cold seep site, a vertical blanking zone, or seismic chimney, is clearly observed on seismic profiles, and it is interpreted to be a fluid conduit. A thick low velocity zone beneath BSR suggests the presence of a gas reservoir there. This “gas reservoir” is shallower than the surrounding canyon floors along the ridge; therefore as warm methane-rich fluids inside the ridge migrate upward, sulfate carried by cold sea water can flow into the fluid system from both flanks of the ridge. This process may drive a fluid circulation system and the active cold seep site which emits both hydrogen sulfide and methane to feed the chemosynthetic communities.

Waist-to-height ratio is a useful index for nonalcoholic fatty liver disease in children and adolescents: a secondary data analysis

BackgroundNonalcoholic fatty liver disease (NAFLD) is a global problem and pediatric obesity has risen dramatically. Early NAFLD might progress to nonalcoholic steatohepatitis (NASH) or liver cirrhosis and significantly increase liver disease-related mortality. We looked for NAFLD predictors in children and adolescents.MethodsThis community-based, cross-sectional study ran from December 2012 to September 2013 in southwestern Taiwan. Children <10 and >19 years old, with detected hepatic diseases, or who drank alcohol were excluded. The diagnosis of NAFLD was based on ultrasound: age, sex, anthropometric measurements, and laboratory data were evaluated for associated risks by using logistic regression analysis. Receiver operating characteristic (ROC) curves were used to determine cutoff values.ResultsWe enrolled one thousand, two hundred and ten children (594 males; 616 females; mean age: 15.5 ± 2.8 years). Age, anthropometric measurements, and laboratory data were significantly higher in children with NAFLD. The association between NAFLD and the waist-to-height ratio (WHtR) was significant (adjusted odds ratio: 2.6; 95% confidence interval: 1.909-3.549; P < 0.001). It indicated highly suspicion of NAFLD (sensitivity: 70.1%; specificity 76.9%) when the WHtR for children and adolescents is above the cutoff value of 0.469.ConclusionsThe WHtR might be a powerful index of the severity of pediatric NAFLD.

Biomarker assessments of sources and environmental implications of organic matter in sediments from potential cold seep areas of the northeastern South China Sea

Multi-biomarker indexes were analyzed for two piston cores from potential cold seep areas of the South China Sea off southwestern Taiwan. Total organic carbon (TOC) normalized terrestrial (n-alkanes) and marine (brassicasterol, dinosterol, alkenones and iso-GDGTs) biomarker contents and ratios (TMBR, 1/P mar-aq, BIT) were used to evaluate the contributions of terrestrial and marine organic matter (TOM and MOM respectively) to the sedimentary organic matter, indicating that MOM dominated the organic sources in Core MD052911 and the sedimentary organic matter in Core ORI-860-22 was mainly derived from terrestrial inputs, and different morphologies were the likely reason for TOM percentage differences. BIT results suggested that river-transported terrestrial soil organic matter was not a major source of TOM of sedimentary organic matter around these settings. Diagnostic biomarkers for methane-oxidizing archaea (MOA) were only detected in one sample at 172 cm depth of Core ORI-860-22, with abnormally high iso-GDGTs content and Methane Index (MI) value (0.94). These results indicated high anaerobic oxidation of methane (AOM) activities at or around 172 cm in Core ORI-860-22. However in Core MD052911, MOA biomarkers were not detected and MI values were lower (0.19–0.38), indicated insignificant contributions of iso-GDGTs from methanotrophic archaea and the absence of significant AOM activities. Biomarker results thus indicated that the discontinuous upward methane seepage and insufficient methane flux could not induce high AOM activities in our sampling sites. In addition, the different patterns of TEX86 and Uk′ 37 temperature in two cores suggested that AOM activities affected TEX86 temperature estimates with lower values in Core ORI-860-22, but not significantly on TEX86 temperature estimates in Core MD052911.

Two new records of the coral symbiont crab genus Quadrella Dana, 1851, from Taiwan, with notes on the taxonomy of Q. boopsis Alcock, 1898 (Crustacea: Brachyura: Trapeziidae)

Two symbiotic trapeziid crabs of the genus Qudrella Dana, 1851, were collected from southwestern Taiwan. Both are new records for the island. Quadrella coronata Dana, 1852, is usually associated with the soft coral Chironephthya spp., while Q. boopsis Alcock, 1898, was found with the scleractinian coral Tubastraea micrantha. The taxonomy of Q. boopsis is treated and the variation in the dorsal surface of the carapace, armature of the anterolateral margin and colour pattern discussed.

Urinary melamine excretion and increased markers of renal tubular injury in patients with calcium urolithiasis: A cross-sectional study

Environmental low-dose melamine exposure has been associated with urolithiasis risk in adults, but it is unclear if this exposure can cause early renal damage. This cross-sectional study investigated the association of this exposure and early renal damage in patients with calcium urolithiasis. We recruited patients diagnosed with upper urinary tract calcium urolithiasis from three hospitals in southwestern Taiwan between November 2010 and January 2015. All patients completed a structured questionnaire and provided one-spot urine samples for the measurement of melamine level and markers of early renal injury, including N-acetyl b-d-glucosaminidase (NAG), β2-microglobulin (β2-MG), and microalbumin. We used urinary melamine levels as an indicator of environmental melamine exposure. A total of 309 patients (mean age of 54.7 ± 12.8 years) were studied. Median urinary melamine level (μg/mmol Cr) was 1.26 (interquartile range 0.48–3.29). A significant and positive correlation was found between urinary melamine concentration and urinary NAG levels (Spearman correlation coefficient, r = 0.157, p = 0.006, n = 309). With urinary melamine levels categorized into quartiles, multivariate regression results showed the same relationship, particularly in those with first stone episode. In this group, patients with the highest quartile of urinary melamine concentration had a 3.95-fold risk (95% confidence interval = 1.43–10.94) of high NAG levels (dichotomized by median), compared to the lowest quartile after adjustment. No association was found between urinary melamine concentration and urinary microalbumin levels. In conclusion, urinary melamine is significantly associated with urinary marker of early renal tubular injury, NAG, in urolithiasis patients, especially ones with first stone episode.

Seasonal fluctuations of ichthyoplankton assemblage in the northeastern South China Sea influenced by the Kuroshio intrusion

AbstractThe distribution and assemblage of ichthyoplankton related to local hydrographic features, especially intrusion of the Kuroshio Current (KC) and Guangdong Coastal Current (GCC) in the northeastern South China Sea (NESCS) were investigated in this study. A total of 193 species of ichthyoplankton belonging to 141 genera and 66 families were recognized in summer 2015 and late‐winter 2016. The ichthyoplankton assemblage was identified with distinct seasonal differences, and the differences were responded well with the oceanography conditions. In summer, the assemblages were identified into offshore and inshore groups, as controlled by the South China Sea Warm Current (SCSWC) in off‐shelf, upwelling, and the diluted water from the Pearl River in inshore. In winter, three groups were divided, representing the southwestern inshore, intrusion of the KC in the eastern offshore, and the GCC in the northern inshore area, respectively. Furthermore, Sigmops gracilis and Vinciguerria sp.3 were probably brought into the NESCS by intrusion of the KC from the eastern Luzon Strait. In addition, high ichthyoplankton abundance was found in high chlorophyll a located in upwelling areas in the northern coastal area in summer and in the southwestern Taiwan Bank in winter, respectively. The nutrition outcropped by the upwelling together, and those brought from the Pearl River probably supported high food availability of the ichthyoplankton in the northern coast of the NESCS.

Effects of Geomechanical Mechanisms on Gas Production Behavior: A Simulation Study of a Class-3 Hydrate Deposit of Four-Way-Closure Ridge Offshore Southwestern Taiwan

The purpose of this study is to investigate the effects of the geomechanical mechanisms on the gas production of a depressurized Class-3 hydrate deposit, Four-Way-Closure Ridge. From this case study, we found that there is a lower gas production rate and a longer production plateau when geomechanics are considered in the fluid flow modeling. The Young’s modulus and Poisson’s ratio are sensitive parameters to the reservoir deformation and the seafloor subsidence. We suggest that the geomechanical issue should be well considered in a hydrate deposit development project.

Activation of gas bubble emissions indicated by the upward decreasing Lead-210 activity at a submarine mud volcano (TY1) offshore southwestern Taiwan

A submarine mud volcano (MV) known as TY1 is one of the largest conical structures found offshore southwestern Taiwan. Active gas bubble emissions at the flat crest of the mud volcano disperse sediment particles into the water column. Changes in the mud volcanism of TY1 were revealed by radiograph and grain size analysis of the sediment cores. 210Pb geochronology was applied to the near-seafloor sediments to reveal the detailed mud volcanism from the deposition rate. In a 58-cm long sediment core taken from the northern margin of the crest, known as TY1-N.170, the size and frequency of the mud clasts decrease upward. The clasts are smaller than 8mm above a sediment depth of 34cm below the sea floor (cmbsf). Sediments between 0 and 19 cmbsf are massive, and particles larger than 2mm are absent. An enrichment of coarse, silt-sized particles in the massive sediment unit and the restricted distribution of the unit suggest that the massive unit was generated by re-deposition of sediment particles that were dispersed into the water column by gas bubble emission. These characteristics suggest that during the last mud volcanism of TY1, there was a decrease in mud eruption energy, and gas bubble emission became the main activity. In core TY1-S.440, taken from the southern slope, a massive sediment unit enriched with coarse, silt-sized particles, is intercalated between mud breccia structures. This suggests repeated mud breccia flows caused by TY1. The excess 210Pb activity present in the massive sediment unit of TY1-N.170 suggests activation of gas bubble emission. In the massive unit, a decrease in excess 210Pb activity appears upward toward the seafloor. The highest value is 3.1dpm/g at 19.8cmbsf (26.4g/cm2 in cumulative mass); values lower than 1.0dpm/g are distributed 2.8–6.8 cmbsf (3.6–8.8g/cm2). The upwardly decreasing trend is opposite that of the reference core from which a reasonable areal sedimentation rate was obtained using a constant-flux constant-sedimentation model. The anomalous depth profile at the massive unit indicates an increasing rate of sediment deposition, which originated from the activation of gas bubble emission.

Multiscale analysis and reduction measures of urban carbon dioxide budget based on building energy consumption

As urban areas continue to develop and expand, carbon dioxide (CO2) emissions from their energy use are growing exponentially. This has made carbon reduction a global concern. Previous studies have provided a limited understanding of carbon budgets because they have used top-down data on a single spatial or temporal scale. In this study, urban spatial and statistical data for metropolitan Tainan in southwestern Taiwan are used to explore inside and outside of the CO2 system of the city and estimate the amount of CO2 emissions from road traffic, the use of electricity and gas in buildings, and the amount of CO2 absorbed by green spaces and water bodies within the system. Innovative annual and monthly carbon budget maps composed of 200×200-m grids are developed for the city through a geographic information system (GIS). An analysis of the highly detailed maps yields the following findings: First, CO2 emissions are concentrated in over-urbanized areas, where the population density is higher than 5000 people/km2. Buildings account for the majority of carbon dioxide emissions (54%) and produced 11% more carbon dioxide in summer than in winter (owing to air-conditioning usage). Second, road traffic is the main source of CO2 emissions for under-urbanized areas (87%), and emissions from this source exhibit insignificant seasonal variation. On the basis of these findings, the carbon budgets of four different over-urbanized areas are formulated and presented on 50×50-m grids. The results suggest that green spaces in these areas absorb limited amounts of carbon dioxide. Therefore, this study assesses the annual and monthly carbon-reduction potential of rooftops equipped with solar panels occupying 30% of their area. The annual carbon-reduction potential for the four areas was 4.5–31.1kgCO2m−2yr−1, and the solar energy replacement rate is higher in winter than in summer. In summary, this study presents carbon budgets in high-resolution grids, quantifies the carbon-reduction potential of rooftops with solar panels, and proposes a reduction strategy for reducing CO2 emissions from urban activities to improve the sustainability of urban areas and their environs and inform urban planning and climate change adaptation.

Production, consumption, and migration of methane in accretionary prism of southwestern Taiwan

AbstractTo systematically quantify the production, consumption, and migration of methane, 210 sediment cores were collected from offshore southwestern Taiwan and analyzed for their gas and aqueous geochemistry. These data, combined with published results, were used to calculate the diffusive methane fluxes across different geochemical transitions and to develop scenarios of mass balance and constrain deep microbial and thermogenic methane production rates within the accretionary prism. The results showed that methane diffusive fluxes ranged from 2.71 × 10−3 to 2.78 × 10−1 and from –1.88 × 10−1 to 3.97 mmol m−2 d−1 at the sulfate‐methane‐transition‐zone (SMTZ) and sediment‐seawater interfaces, respectively. High methane fluxes tend to be associated with structural features, suggesting a strong structural control on the methane transport. A significant portion of ascending methane (&gt;50%) is consumed by anaerobic oxidation of methane at the SMTZ at most sites, indicating effective biological filtration. Gas compositions and isotopes revealed a transition from the predominance of microbial methane in the passive margin to thermogenic methane at the upper slope of the active margin and onshore mud volcanoes. Methane production and consumption at shallow depths were nearly offset with a small fraction of residual methane discharged into seawater. The flux imbalance arose primarily due to the larger production of methane through deep microbial and thermogenic processes at a magnitude of 1512–43,096 Tg Myr−1 and could be likely accounted for by the sequestration of methane into hydrate forms, and clay absorption.

Revealing Pesticide Residues Under High Pesticide Stress in Taiwan's Agricultural Environment Probed by Fresh Honey Bee (Hymenoptera: Apidae) Pollen.

Significant pesticide residues are among the most serious problems for sustainable agriculture. In the beekeeping environment, pesticides not only impact a honey bee's survival, but they also contaminate bee products. Taiwan's agricultural environment has suffered from pesticide stress that was higher than that found in Europe and America. This study deciphered problems of pesticide residues in fresh honey bee pollen samples collected from 14 monitoring apiaries in Taiwan, which reflected significant contaminations within the honey bee population. In total, 155 pollen samples were screened for 232 pesticides, and 56 pesticides were detected. Among the residues, fluvalinate and chlorpyrifos showed the highest concentrations, followed by carbendazim, carbaryl, chlorfenapyr, imidacloprid, ethion, and flufenoxuron. The average frequency of pesticide residues detected in pollen samples was ca. 74.8%. The amounts and types of pesticides were higher in winter and in southwestern Taiwan. Moreover, five of these pollen samples were contaminated with 11-15 pesticides, with average levels between 1,560 and 6,390 μg/kg. Compared with the literature, this study emphasized that pollen gathered by honey bee was highly contaminated with more pesticides in Taiwan than in the America, France, and Spain. The ubiquity of pesticides in the pollen samples was likely due to the field applications of common pesticides. Recently, the Taiwanese government began to improve the pesticide policy. According to the resurvey data in 2016, there were reductions in several pesticide contamination parameters in pollen samples from west to southwest Taiwan. A long-term investigation of pollen pesticide residues should be conducted to inspect pesticides usage in Taiwan's agriculture.

Biogeochemical cycles at the sulfate-methane transition zone (SMTZ) and geochemical characteristics of the pore fluids offshore southwestern Taiwan

In this study, we used pore water dissolved inorganic carbon (DIC), SO42−, Ca2+ and Mg2+ gradients at the sulfate-methane transition zone (SMTZ) to estimate biogeochemical fluxes for cored sediments collected offshore SW Taiwan. Net DIC flux changes (ΔDIC-Prod) were applied to determine the proportion of sulfate consumption by organic matter oxidation (heterotrophic sulfate reduction) and anaerobic oxidation of methane (AOM), and to determine reliable CH4 fluxes at the SMTZ. Our results show that SO42− profiles are mainly controlled by AOM rather than heterotrophic sulfate reduction. Refinement of CH4 flux estimates enhance our understanding of methane abundance from deep carbon reservoirs to the SMTZ. Concentrations of chloride (Cl−), bromide (Br−) and iodide (I−) dissolved in pore water were used to identify potential sources that control fluid compositions and the behavior of dissolved ions. Constant Cl− concentrations throughout ∼30m sediment suggest no influence of gas hydrates for the compositions within the core. Bromide (Br−) and Iodine (I−) concentrations increase with sediment depth. The I−/Br− ratio appears to reflect organic matter degradation. SO42− concentrations decrease with sediment depth at a constant rate, and sediment depth profiles of Br− and I− concentrations suggests diffusion as the main transport mechanism. Therefore diffusive flux calculations are reasonable. Coring sites with high CH4 fluxes are more common in the accretionary wedge, amongst thrust faults and fractures, than in the passive continental margin offshore southwestern Taiwan. AOM reactions are a major sink for CH4 passing upward through the SMTZ and prevent high methane fluxes in the water column and to the atmosphere.

Westward advance of the deformation front and evolution of submarine canyons offshore of southwestern Taiwan

This study analyzes both 2D and 3D seismic images around the Palm Ridge area offshore of southwestern Taiwan to understand how the deformation front shifted westward and how tectonic activities interact with submarine canyon paths in the transition area between the active and passive margins. Palm Ridge is a submarine ridge that developed on the passive China continental margin by down-dip erosion of several tributaries of Penghu Canyon; it extends eastward across the deformation front into the submarine Taiwan accretionary wedge. The presence of proto-thrusts that are located west of the frontal thrust implies that the compressional stress field has advanced westward due to the convergence of the Philippine Sea Plate and Eurasian Plate. Since the deformation front is defined as the location of the most frontal contractional structure, no significant contractional structure should appear west of it. We thus suggest moving the location of the previously mapped deformation front farther west to where the westernmost proto-thrust lies. High-resolution seismic and bathymetric data reveal that the directions of the paleo-submarine canyons run transverse to the present slope dip, while the present submarine canyons head down slope in the study area. We propose that this might be the result of the westward migration of the deformation front that changed the paleo-bathymetry and thus the canyon path directions. The interactions of down-slope processes and active tectonics control the canyon paths in our study area.

Multilocalization data assimilation for predicting heavy precipitation associated with a multiscale weather system

AbstractHigh‐resolution numerical simulations are regularly used for severe weather forecasts. To improve model initial conditions, a single short localization is commonly applied in the ensemble Kalman filter when assimilating observations. This approach prevents large‐scale corrections from appearing in a high‐resolution analysis. To improve heavy rainfall forecasts associated with a multiscale weather system, analyses must be accurate across a range of spatial scales, a task that is difficult to accomplish using a single localization. This study is the first to apply a dual‐localization (DL) method to improve high‐resolution analyses used to forecast a real‐case heavy rainfall event associated with a Meiyu front on 16 June 2008 in Taiwan. A Meiyu front is a multiscale weather system characterized by storm‐scale convection, a mesoscale front, and large‐scale southwesterly monsoonal flow. The use of the DL method to produce the analyses was able to correct both the synoptic‐scale moisture flux transported by southwesterly monsoonal flow and the mesoscale low‐level convergence offshore of southwestern Taiwan. As a result, the forecasted amount, pattern, and temporal evolution of the heavy rainfall event were improved.

Comparative Study on Hatching Rate, Survival Rate, and Feminization of Onychostoma barbatulum (Pellegrin, 1908) at Different Temperatures and Examining Sex Change by Gonad and Karyotype Analyses.

Mei-Chen Tseng, Dian-Hao Yang, and Tsair-Bor Yen (2017) Onychostoma barbatulum has become an aquaculture species with high economic value in Taiwan. It was observed that females can grow faster to a larger size than males on aquaculture farms. Therefore, development of feminized fry can increase farm profits in the future. The purpose of this study was to establish the optimal incubation, feed, and feminization temperatures to produce a high feminization ratio and better survival rates for O. barbatulum fry. The performance mode of sex-determination by temperature was also explored in the study. Adults were collected from Nanzixian Stream in southwestern Taiwan and artificially propagated in tanks. Fertilized eggs were placed in environments of different temperatures to determine the hatching rate (n = 3000) and the survival rate (n = 3000) of fry. After 6 months, the sex ratio was established from gonad tableting (n = 360). A karyotype analysis (n = 86) was also conducted to verify the existence of gender-reversed individuals. The results showed that hatching rates at 17.5, 19.5, 21.5, 23.5, and 25.5°C were 70.7%, 67.3%, 73.3%, 33.7%, and 34.7%, respectively. Survival ratios from low to high temperatures were 34.7%, 47.7%, 33.7%, 12.3%, and 23.3%, respectively. These results indicated that both the hatching rates and survival ratios of fry performed poorly at temperatures higher than 21.5°C. The performance mode of sex-determination by temperature of O. barbatulum revealed that female ratios significantly decreased at the two extremes of the temperature range, while the female ratio was highest at an intermediate temperature. The best feminized ratio (83.4%) was observed at 21.5°C among all tested temperatures (p < 0.05). Meanwhile according to a karyotype analysis, sex-reversed individuals were found in each group, indicating that temperature is a critical phenotypic sex-determining factor. Therefore, rearing O. barbatulum fry at a proper water temperature can effectively increase the female sex ratio and maintain high hatchability and survival ratios. These results can potentially be applied to produce a high proportion of female fry on aquaculture farms.

Assessment of susceptibility to rainfall-induced landslides using improved self-organizing linear output map, support vector machine, and logistic regression

Quantitative landslide susceptibility assessment is necessary for mitigating casualties, property damage, and economic loss. Identification of landslides and preparation of landslide susceptibility maps are crucial steps in landslide susceptibility assessment. Therefore, an optimal landslide susceptibility model is presented that is capable of producing accurate landslide susceptibility maps and assessing landslide susceptibility. To construct the optimal landslide susceptibility model, the effectiveness of the improved self-organizing linear output map (ISOLO), support vector machines (SVM) with four kernel functions (LN-SVM, PL-SVM, RBF-SVM, and SIG-SVM) and logistic regression (LR) was compared. Twelve landslide causative factors (namely, slope, slope aspect, elevation, curvature, profile curvature, plan curvature, slope length, topographic wetness index, distance to river, distance to road, distance to fault and annual maximum 24- and 48-h rainfalls) were used in this landslide susceptibility analysis. These models were applied to the Kaoping River basin in Southwestern Taiwan to assess its performance. Landslide inventory maps from 2008 to 2011 were collected. Data from the first three-year period were used for training and the remaining data was used for testing. The performance of the models was compared using accuracy and the area under the receiver operating characteristic curve as criteria. The results show that the RBF-SVM model outperformed the logistic regression in the study area. Using the RBF-SVM model, the landslide susceptibility under the annual 48-h maximum rainfall of various return periods were analyzed to assist local administrations and decision makers in disaster planning.

Diapiric activities and intraslope basin development offshore of SW Taiwan: A case study of the Lower Fangliao Basin gas hydrate prospect

The architecture and distribution of mud diapirs are shaped by tectonic activity, sediment filling and unbalanced loading characteristics. Mud diapir development also controls spatial variations of intraslope basins in slope areas and can spur upward fluid migration with diapiric intrusion. The offshore area of southwestern Taiwan is an incipient collision zone in which thick sequences of deep marine sediments filled a rapidly subsided foredeep basin during the Pliocene. Large volumes of deposited sediment serve as source materials of diapiric ridges that extend NNE-SSW, and some mud diapirs even extend to on land SW Taiwan with subsurface signatures of gas. This study examines relationships between mud diapir and intraslope basin development in convergent tectonics through seismic and bathymetry data analyses. Four types of mud diapirs are identified: (1) buried symmetrical diapirs; (2) symmetrical diapirs extruded above the seafloor; (3) asymmetric and irregular diapirs; and (4) small individual diapirs manifested as mud intrusions found in local areas. A 3-stage model is proposed as a tool for describing the development and distribution of these types of diapirs. We further examine the relationship between mud diapirs and intraslope basin development patterns by analyzing 2D and 3D seismic images to reveal structural and sedimentary processes occurring in the Lower Fangliao Basin. This basin is characterized by BSR and amplitude anomalies of seismic profiles and is a prospect of the Taiwanese gas hydrate investigation project. An 8-stage development model with six depositional units is proposed as a means to explain the evolution of diapirs, submarine canyons, and fold and fault activities in the Lower Fangliao Basin, in turn revealing the relationship between mud diapir formation and intraslope basin development offshore of southwestern Taiwan.

Recent movement of the Late Pleistocene Shoushan slump, southwestern Taiwan, based on landform surveys

This study aims to investigate and to analyze the recent complex mass movements of Shoushan in Kaohsiung City, southwestern Taiwan, by the short-term global positioning system (GPS) survey and the comparison of elevation data from different sources. Landform change is derived from difference of 5-m digital elevation models (DEMs), i.e., the DEMs of difference (DoD), which are abstracted from 1:5000 scale contour maps dating to 1978 and 1998. The spatial distribution of elevation change within the study area is visualized and delineated by the threshold value of 2.5 m which is resulted from the error level of contour maps. The GPS survey of benchmarks is deployed to infer the short-term surface movement in the study area, and to argue with the results of DoD analysis. To ensure the reliability of GPS field measurements, a 6-h static surveying procedure is applied to each benchmark with the reference GPS station being positioned in a tectonically stable location close to the study area. Based on the GPS survey results and the DoD analysis, the study identifies the development of several secondary slumps on the main body of the huge slump. The secondary slumps are characterized by relatively slow movements with diverse directions.

Assessment of heavy metals in aquaculture fishes collected from southwest coast of Taiwan and human consumption risk

The present study determined the metal levels in aquaculture fish of tilapia and water and sediments in the southwestern Taiwan and estimated the human health risk assessment for consumption of tilapia. Bioconcentration factor (BCF) and biota-sediment accumulation factor (BSAF) were used to assess the metal accumulation ability of biotas, while metal pollution index (MPI) was assessed to compare the pollution level of total eight metals for the different sampling sites and tissues of tilapia. Metal level in tissues revealed a tissue-specific bioaccumulation pattern. Except for Cu, the highest metal burden was found in kidney, showing the significant differences in metal concentration of kidney with the other tissues of tilapia. Muscle accumulated the low concentrations of Hg (0.19 ± 0.21 μg g−1 dry wt), Cd (0.05 ± 0.02), As (0.06 ± 0.05), Cu (1.61 ± 1.17), Zn (21.5 ± 10.2), and Ni (1.01 ± 1.03). Results allowed putting the mean MPI of tissues in order from the highest to lowest value, kidney (6.92) > GI tract (2.06) > liver (1.25) > gill (0.80) > muscle (0.59). In addition to Hg and Cd, the estimate of BCF was greater that of BSAF for other metals, demonstrating that the bioaccumulation of Hg and Cd for tilapia collected from aquaculture ponds was from the sediments, as well as the bioaccumulation of other metal was from water. Correlation analysis found that Fulton's condition factor (K) of tilapia had the negative relationship with MPI for muscle, liver, and kidney, meaning decreasing K of tilapia was with the increasing estimates of MPI. For the human health risk assessment, tilapia cultured in the southwest coast of Taiwan was found to be low-risk for consumption and do not surface a potential threat to the health of general human consumers. Results in this effort can assist the government in determining seafood safety and its implementation in Taiwan.

Isotopic evidence for the influence of typhoons and submarine canyons on the sourcing and transport behavior of biospheric organic carbon to the deep sea

Export of biospheric organic carbon from land masses to the ocean plays an important role in regulating the global carbon cycle. High-relief islands in the western Pacific are hotspots for such land-to-ocean carbon transport due to frequent floods and active tectonics. Submarine canyon systems serve as a major conduit to convey terrestrial organics into the deep sea, particularly during episodic floods, though the nature of ephemeral sediment transportation through such canyons remains unclear. In this study, we deployed a sediment trap in southwestern Taiwan's Gaoping submarine canyon during summer 2008, during which Typhoon Kalmaegi impacted the study area. We investigated sources of particulate organic carbon and quantified the content of fossil organic carbon (OCf) and biospheric non-fossil carbon (OCnf) during typhoon and non-typhoon periods, based on relations between total organic carbon (TOC), isotopic composition (δ13C, 14C), and nitrogen to carbon ratios (N/C) of newly and previously reported source materials. During typhoons, flooding connected terrestrial rivers to the submarine canyon. Fresh plant debris was not found in the trap except in the hyperpycnal layer, suggesting that only hyperpycnal flow is capable of entraining plant debris, while segregation had occurred during non-hyperpycnal periods. The OCnf components in typhoon flood and trapped samples were likely sourced from aged organics buried in ancient landslides. During non-typhoon periods, the canyon is more connected to the shelf, where waves and tides cause reworking, thus allowing abiotic and biotic processes to generate isotopically uniform and similarly aged OCnf for transport into the canyon. Therefore, extreme events coupled with the submarine canyon system created an efficient method for deep-sea burial of freshly produced organic-rich material. Our results shed light on the ephemeral transport of organics within a submarine canyon system on an active tectonic margin.