Coast Of Taiwan Research Articles

Isotopic niche differentiation in benthic consumers from shallow-water hydrothermal vents and nearby non-vent rocky reefs in northeastern Taiwan

Shallow-water hydrothermal vents (SVs) off Kueishan (KS) Islet are located along the northeastern coast of Taiwan. Although the trophic relationships of the sublittoral (15–30 m) and upper bathyal (200–300 m) vents in this region have been investigated, a comparison of SVs and adjacent non-vent ecosystems has not been undertaken. We compared the trophic structure and isotopic niche width of consumers in benthic communities around SVs off KS Islet with nearby non-vent rocky reefs (NV) to address this gap. The trophic structures for both SV and NV habitats were categorized into four trophic levels based on δ13C and δ15N signatures. SV sites ranged from −27.7 to −14.3‰ (δ13C) and from −7.3 to 12.2‰ (δ15N), whereas NV sites ranged from −20.2 to −13.1‰ (δ13C) and from 2.2 to 11.9‰ (δ15N). We found a notable difference in δ13C and δ15N values for primary producers and sediment organic matter between the two habitats indicating that available nutrient sources were different and more diversified in SV than those in NV. Based on the types of consumer feeding guilds, no difference in niche width of filter feeders between SV and NV was detected by ellipses analysis. Besides, a narrower niche width for scavengers in SV and differentiated niche positions for carnivores in both habitats were found. We conclude that plankton-derived production (i.e., dead zooplankton killed by sulfurous plumes) plays a significant role in providing food to benthic communities. These include not only scavengers, such as vent crabs, but also carnivores in SVs off KS Islet where extreme values of pH (1.52), temperature (116 °C), and H2S (172 mmol/mol) are known to occur.

Taiwan Rainbands Formed in the Outer Region of Tropical Cyclones

AbstractThis study used Doppler radar data, surface observations, and National Centers for Environmental Prediction reanalysis data to explore the statistical characteristics of Taiwan rainbands (TRs) that formed in the outer region of tropical cyclones (TCs). A comprehensive examination of the available radar measurements from 2002 to 2017 identified a total of 103 TRs from 44 TC events and showed that approximately 47% of all TCs influencing Taiwan could develop TRs. The spatial distribution of TR formation exhibited a substantial offshore extent, with the highest frequency observed ~25–100 km offshore. The TRs tended to be initiated when the northwestward-moving typhoons passed over the oceanic area northeast of Luzon Island (16°–20°N, 122°–127°E), the Philippines. This track characteristic brought stronger easterly onshore flow to the eastern coast of Taiwan and favored the development of a pronounced coastal pressure ridge. In particular, the offshore convergence caused by upstream deceleration of the onshore flow due to orographic blocking was found to be a primary contributor to the initiation of the TRs. The strength of the observed coastal pressure ridge and its high correlation with the intensity of environmental onshore flow associated with outer circulations of TCs were consistent with the theoretical prediction of pressure distributions generated as incident flow interacted dynamically with the Taiwan topography. Results from the study suggest that the typhoon location relative to the Taiwan landmass is a critical factor determining TR initiation.

Chemical speciation of iron in the euphotic zone along the Kuroshio Current

The distributions of dissolved iron (DFe) and organic iron-binding ligands (LFe) in the Kuroshio Current and its neighboring waters were elucidated from four cross-sectional surveys from the eastern coast of Taiwan to Sagami Bay. The Kuroshio surface water was characterized by a high salinity, low concentration of DFe, high concentration of LFe, and low fluorescence of humic-like substances, in comparison to the neighboring waters. The neighboring waters of the Kuroshio can be categorized into two types: the East China Sea water and coastal water. The East China Sea water was found near the Okinawa Trough, and characterized by a steep vertical gradient of DFe concentration, almost as low as that in the Kuroshio within the surface mixed layer, but reached ~0.5 nM below the mixed layer. Coastal water was observed on the southern coast of Japan, and its DFe concentration was high throughout the upper 200 m. The concentration of LFe in the Kuroshio water was significantly higher at 10-m depth than in the deeper layers. This suggests that humic-like substances, which are a major component of LFe in estuarine and deep waters, play a relatively minor role in the Kuroshio surface waters. Mixing with coastal waters can increase the concentration of bioavailable inorganic ferric ions in the Kuroshio surface water in two ways, by increasing the DFe concentration and decreasing the LFe concentration.

Rotary Spectral Analysis for Directional Time Series: Seasonal Variation of Wind Speed on a Subtropical Island near the Western Pacific Ocean

Directional or vector time-dependent observations, such as the flow at a river branch, streamflow, lake flow, ocean currents, or wind data, are commonly observed in the environment. Traditionally, a rose diagram can be used to summarize the possible main orientation using all the data in the time domain. However, it cannot indicate the significant variation in the specific frequency bands that may show dominant periodic fluctuations. Assessment of directional time series often requires the identification of significant components in the specific frequency bands for not only the magnitude but also the orientation. The rotary pattern, main orientation, and magnitude of directional time series in the frequency domain for five sets of seasonal wind velocity observed at the northern, southern, eastern, and western coast of the subtropical island Taiwan and Taiwan Strait have been demonstrated. It shows that the representative pattern is clockwise, counterclockwise, or near rectilinear, and semidiurnal and diurnal components are significant in the frequency domain for most stations. The most important research innovation suggests that the use of rotary spectral analysis in the frequency domain to effectively assess the orientation and magnitude of directional time series, such as hydrological, coastal, or environmental observations, has become feasible.

Seasonal variation of diversity, weathering, and inventory of microplastics in coast and harbor sediments

Spatiotemporal variations in the abundance of microplastics (MPs) in surface sediments along the southwestern coast of Taiwan (including harbor and coastal regions) were investigated and the diversity, degree of weathering, and inventory of MPs in the sediments further quantified. The spatiotemporal variations of MP characteristics were used to assess possible transport routes of MPs. Results indicated that the average MP abundance in the partially-enclosed harbor region was 79.3 MPs in 1 kg dry sediment (item/kg dw), which was 3–5 times higher than that in the coastal region. Average MP abundance during the dry season (36.5 ± 52.2 item/kg dw) was relatively higher than that during the wet season (22.3 ± 23.2 item/kg dw). The dominant MPs were small (0.1–1.0 mm, 90%), colored (62.3%), and consisted mainly of fibers (54.1%) and fragments (40.5%). Analysis by μFTIR revealed the presence of ten types of polymers in the MPs, with the most abundant being polypropylene (35.1%), rayon (33.2%), and polystyrene (10.0%). Values of the microplastic diversity integrated index (MPDII) indicated that MP diversity was greater in the harbor region (MPDII = 0.62) than in the coastal region (MPDII = 0.51–0.54), and greater during the wet season (MPDII = 0.60) than during the dry season (MPDII = 0.50). As indicated by values of the MP carbonyl index (CI), the MPs exhibited a high degree of oxidation (CI >0.31) that appeared unrelated to spatiotemporal variations. In the dry season, MP inventory was 12.2 tons and the wet season inventory was 8.1 tons. The hydrodynamic forces may be an influenced force for the spatiotemporal distribution patterns of the MPs in surface sediments. MPs could accumulate in the surface sediments during the dry season and resuspend in the wet season with the higher rainfall and then migrate towards the deep sea following the water flow.

Risk Assessment of Coastal Flooding under Different Inundation Situations in Southwest of Taiwan (Tainan City)

The Pacific island countries are particularly vulnerable to the effects of global warming including more frequent and intense natural disasters. Seawater inundation, one of the most serious disasters, could damage human property and life. Regional sea level rise, highest astronomic tide, vertical land motions, and extreme sea level could result in episodic, recurrent, or permanent coastal inundation. Therefore, assessing potential flooding areas is a critical task for coastal management plans. In this study, a simulation of the static flooding situation in the southwest coast of Taiwan (Tainan city) at the end of this century was conducted by using a combination of the Taiwan Digital Elevation Model (DEM), regional sea level changes reconstructed by tide gauge and altimetry data, vertical land deformation derived from leveling and GPS data, and ocean tide models. In addition, the extreme sea level situation, which typically results from high water on a spring tide and a storm surge, was also evaluated by the joint probability method using tide gauge records. To analyze the possible static flood risk and avoid overestimation of inundation areas, a region-based image segmentation method was employed in the estimated future topographic data to generate the flood risk map. In addition, an extreme sea level situation, which typically results from high water on a spring tide and a storm surge, was also evaluated by the joint probability method using tide gauge records. Results showed that the range of inundation depth around the Tainan area is 0–8 m with a mean value of 4 m. In addition, most of the inundation areas are agricultural land use (60% of total inundation area of Tainan), and two important international wetlands, 88.5% of Zengwun Estuary Wetlands and 99.5% of Sihcao Wetlands (the important Black-faced Spoonbills Refuge) will disappear under the combined situation. The risk assessment of flooding areas is potentially useful for coastal ocean and land management to develop appropriate adaptation policies for preventing disasters resulting from global climate change.

Seawater exchange rates for harbors based on the use of MIKE21 coupled with transport and particle tracking models

The water self-purification capacities of coastal areas can be affected by the extension of adjacent harbors. Studies of the seawater exchange capacities of harbors are viewed as an important index and means of protecting coastal water environments. In this paper, the MIKE21 hydrodynamic model (HD) is established and coupled with the transport model (TR) and particle tracking model (PT). Taking the Budai Harbor of Chiayi County along the southwestern coast of Taiwan as an example, five scenarios of upstream river inflow and corresponding pollutant distributions are explored. The tidal exchange rates (TER) of the five scenarios are quantitatively calculated. The results show the following: (1) Water exchange and self-purification capacities of the coastal area are stronger than those of other areas of the wetland region. (2) The self-purification capacities of the wetland are improved close to estuary due to upstream inflows. (3) With an increase in upstream flows, the wetland TER increases from 0.85 to 0.95, showing that inflows improve the water exchange capacity of the wetland. These have results applications for quantifying the influence of engineering construction in coastal areas close to harbors, for revealing the rates of seawater exchange that govern areas within and outside of harbors.

Tide–surge and wave interaction around the Taiwan coast: insight from Typhoon Nepartak in 2016

This study mainly aims to hindcast historical Typhoon Nepartak (2016) and to analyze tide–surge and wave interactions. To achieve this goal, a coupled tide–surge–wave model was built around the coast of Taiwan, and it was applied to simulate storm surges and waves during historical typhoon event. To demonstrate its capability, the coupled model was validated with observed water levels, wind speeds, atmospheric pressures, wave heights, and wave periods at different stations. Quantitatively, the model results reasonably reproduced the observed data. Furthermore, the model was utilized to explore the tide, surge, and wave interaction using historical Typhoon Nepartak (2016). The model results revealed that onshore wind enhanced the surge height, while offshore wind decreased the surge height. The atmospheric pressure consistently displayed a positive contribution to surge height. The wind-induced surge height contributing to the total surge height was 136.83% at Taichung Harbor, because the offshore wind mainly dominated the surge height compared to the effect of atmospheric pressure. The atmospheric pressure-induced surge heights contributing to the total surge height were 100.59%, 96.26%, and 99.74% at Kaohsiung Harbor, Hualien Harbor, and Taitung Fugang, respectively, as a result of the atmospheric pressure dominating the surge height. However, the contribution of the wave setup to the total surge height was minor. The path of typhoons at different time frames significantly affected the spatial distributions of surge height and wave height around the coast of Taiwan. The contributions of water level and current to wave height reached a maximum value of approximately 0.3 m at Suao, while the contributions at Penghu, Qigu, and Eluanbi were all less than 0.2 m. This signified that the influence of the water level and current on wave height was not negligible.

Structural control on the 2018 and 2019 Hualien earthquakes in Taiwan

The 2018 Mw 6.4 Hualien earthquake and the 2019 Mw 6.1 Hualien earthquake occurred beneath the eastern coast of Taiwan, at depths of <~20 km. The two earthquakes caused a total of 18 fatalities and widespread damage to infrastructures, especially in the Hualien City. To better understand the generating mechanism of the damaging earthquakes, we conducted seismic tomography to determine high-resolution 3-D models of P and S wave velocity (VP, VS) and Poisson's ratio (σ) in the source zone. We used 334,645 P- and 238,581 S-wave arrival times of 20,825 local earthquakes (1.5 ≤ ML ≤ 6.9) recorded at 47 seismic stations in Taiwan. Our results show that the hypocenters of the two Hualien mainshocks are located at a sharp vertical boundary where seismic velocity and Poisson's ratio change drastically in the horizontal direction, which corresponds to the location of the Longitudinal Valley Fault and its branches. Furthermore, the hypocenters are located right above a high-σ anomaly that is connected to the estimated upper boundary of the subducting Philippine Sea slab, which may reflect ascending fluids dehydrated from the slab. These results suggest that the 2018 and 2019 Hualien earthquakes were triggered by ascending fluids from the slab dehydration, invading into active faults that may be the northern extension of the Longitudinal Valley Fault.

A platform for Kuroshio Energy Harvesters

In response to the increasing renewable energy demand, harvesting the energy from Kuroshio become an important task in Taiwan. In this study, the ANSYS-FLUENT and ANSYS-AQWA were used to design a Spar platform for carrying multiple current energy harvesters. The platform follows the design code of ABS rules (ABS, 2014). The designed spar model was established in OrcaFlex, and so as the mooring line system, including the anchor chain and duct chain was built. The simulated results show the spar is stable under normal and storm wave conditions. The pre-designed nozzle-diffuser-duct (NDD) can capture 15 kW of current energy, however, as a megawatt power plant, 60 ducts are needed to be deployed. The proposed SPAR platform could be used as a carrier to overcome the difficulties of deploying 60 NDDs to seabed and it may also reduce the construction costs. The simulated results show the spar and associated NDDs are stable under normal and storm wave conditions. This study suggests the platform may be expected to carry more than 60 NDDs and the megawatt Kuroshio energy harvester is feasible to be deployed at the east coast of Taiwan in the future.

Effects of a mobile phone application for graduate nurses to improve central venous catheter care: A randomized controlled trial.

To develop and test a mobile phone application (app) for graduate nurses on the use and care of central venous catheters. A randomized controlled trial was conducted at a teaching hospital in the central east coast of Taiwan. Recruitment occurred from 1 August 2019 -31 October 2019. All graduates (N=90) attending a 2-week induction program attended a lecture and completed a 10-item questionnaire on central venous catheter assessment and care at the end of Week 1 (Time 1). Volunteers were then randomly allocated to receive a link to the learning app on their mobile phone (n=39 Group A) or control condition (N=40 Group B). One week later, all graduates completed the knowledge assessment (Time 2) and a simulated clinical assessment with a mannequin. Skills were assessed using an 11-item, direct observation of procedural skills form. Only data from consenting participants were analysed. Compared with controls, nurses receiving the intervention reported significantly better knowledge (t=-7.98, p<.001, CI=20.9~34.8) and skill scores (t=2.83, p=.006, CI=1.14~6.61). More frequent use of the mobile phone app was associated with higher knowledge (r=0.39, p=.02, CI=0.11~0.99) and skills (r=0.42, p=.008, CI=0.17~1.03). Mobile app instruction for graduate nurses on central venous catheter care increased specific knowledge and skills compared with conventional methods of instruction. Implementation of mobile phone application technology can be considered a feasible means to proactively provide training and education. Mobile phone apps could be developed for a range of clinical procedures and various settings. Future studies with a larger sample and a longitudinal follow-up are warranted to confirm results.

The Spatial-Temporal Distribution of GOCI-Derived Suspended Sediment in Taiwan Coastal Water Induced by Typhoon Soudelor

This paper discusses the use of a Geostationary Ocean Color Imager (GOCI) to monitor the spatial–temporal distribution of suspended sediment (SS) along the coastal waters of northern Taiwan which was affected by Typhoon Soudelor from 8 to 10 August 2015. High temporal resolution satellite images derived from GOCI were processed to generate four-day average images of SS for pre- and post-typhoon periods. By using these four-day average images, characteristics of SS along the north of Taiwan coastal water can be tracked. The results show that SS concentration increased in the four-day average image immediately after the typhoon (11–14 August), and then decreased in the four-day average image 9 to 12 days after the typhoon (19–22 August). The mouths of the Dajia River and Tamsui River were hotspots of SS, ranging from 9 to 15 g/m3 during the two post-typhoon periods. Moreover, the maximum suspended sediment (SSmax) and its corresponding time (tmax) can be computed using GOCI hourly images for the post-typhoon period from 08:30 on 11 August to 08:30 on 22 August. The results show that SSmax occurred in the west coastal water within 4 days post-typhoon, and SSmax occurred in the east coastal water 9 to 12 days post-typhoon. Furthermore, an exponential decay model was used to compute the time when 90% of typhoon-induced SS was dissipated after Typhoon Soudelor (t90). It was found that t90 in the mouths of the Tamsui River and Heping River was the longest among all coastal waters of our study area, with a range of 360–480 h. River discharge and ocean currents with suspended sediment concentration are discussed.

On the separation of upper and low‐level centres of tropical storm Kong‐Rey (2013) near Taiwan in association with asymmetric latent heating

AbstractTropical Storm (TS) Kong‐Rey (2013) moved northward off the eastern coast of Taiwan in late August. Satellite and radar observations indicated an asymmetric convective structure to the south and southwest of the typhoon centre. The maximum rainfall produced was also far from its centre and unlike the usual pattern in climatology, causing flooding, inundation, and casualties in southwestern Taiwan. Moreover, as a detached centre in the middle and upper levels moved over land, a highly tilted vertical structure was revealed and its cause is the focus of the present study. Even though vertical wind shear was present and might cause asymmetry in convective pattern at an early stage, the detachment of the centre aloft during the period of interest (28–29 August) is found to link to Taiwan's steep topography through model experiments and potential vorticity tendency diagnosis. With the uplifting of strong low‐level westerly flow by the topography, the intense convection in the control experiment is concentrated at the windward slopes (in southwestern Taiwan) and the wave‐number‐1 motion vector from the diabatic heating produces southwestward movement of the centre aloft, and thus leads to the detachment. On the other hand, in the sensitivity test without Taiwan terrain, the rainfall region shifts eastward toward the low‐level TC centre, and the detachment does not occur. Overall, with a weak vertical coupling of TS Kong‐Rey (2013), the impacts of topography can explain both the observed separation of its centres and the unusual rainfall pattern in Taiwan.

Sand Grain Size and Organic Matter Concentration in the Intertidal Zones on the Southwest Coast of Taiwan

From April 2013 to April 2014, the average pH and water temperature of the Taisi oyster cultivation area (TS, Yunlin County, Taiwan) were 8.05 (7.35 - 8.45) and 24.7˚C (13.7˚C - 32.8˚C) (N = 8226) The average organic matter (OM) concentration at sites TS-A and TS-B were 6.9% ± 1.3% and 6.9% ± 1.2%, and the weight of drift sand was 40.3 ± 19.1 g/d/m2 and 28.5 ± 34.3 g/d/m2 (N = 27). Considerable sand drifting typically occurs during the southwest monsoon season in summer. The average OM concentration at five dunes from Zhuoshui estuary to Zengwun estuary was 23.9 ± 4.5 g/kg. The percentage of sand grain weight of 0.15 - 0.25 mm and 0.25 - 0.60 mm was 82.5% ± 14.2% and 10.5% ± 12.0%. In the spring and autumn of 2015, the average OM concentration at the eight intertidal zones from Hanbao to Cigu was 49.8 ± 34.1 g/kg (N = 177), and the OM concentrations at Huwei estuary and Hanbao and Fangyuan intertidal zones were relatively high. The OM concentration (95.3 ± 75.7 g/kg) of the low tide zone of Huwei estuary was the highest among all tidal zones. The OM concentration during spring (59.4 ± 41.7 g/kg, N = 95) was higher than that in autumn (39.1 ± 17.8 g/kg, N = 84). For sand grain size ranges 0.15 - 0.25 and 0.063 - 0.15 mm, the weight ratio of intertidal sediment was 39.4% ± 26.9% and 27.6% ± 20.1%, respectively. The broad and flat intertidal zone was marked by fine sand and long intertidal zone; the weight ratio of SGSs < 0.25 mm exceeded 65%, and the OM concentration was between 20 and 30 g/kg. Coastal habitat diversity creates differences in biological communities, especially among crabs and benthic organisms. A greater understanding of coastal environments can aid in the management of coastal wetlands.

Anthropogenic 129I in the South China Sea and coastal waters around Taiwan

In this article, we present a study of seawater 129I/127I time-series data from several coastal sites in Taiwan, including Yehliu Geopark (north–northeast coast), Kaohsiung (southwest coast), and Zhuwei Fishing Village (northwest coast). The objective of this study was to document how 129I/127I responds to known seasonal variations in the surface ocean currents that carry 129I to each of these sites. The responses were shown to be quite distinct. The Zhuwei site, across Mainland China, had elevated spring and summer 129I/127I values, with abrupt peaks that reflected transient cross-strait currents that carry seawater with elevated 129I to the northwest coast of Taiwan. The Yehliu site, which receives all of its seawater from the Kuroshio Current, had relatively low and uniform 129I/127I values year-round. The Kaohsiung site showed a summertime minimum that likely stems from upwelling upstream induced by oceanic eddies associated with the Kuroshio intrusion. To our knowledge, these are the first continuous coastal 129I/127I time-series data published for Asian waters and the first to show large, abrupt, and regional 129I/127I changes in the surface seawater. We also documented 129I/127I values from multiple surface ocean sites in the South China Sea (SCS), including a vertical profile from the South East Asia Time-Series Station that extends to a depth of 3,700 m. The 129I from both coastal Taiwan and surface waters of the SCS is &amp;gt;98% anthropogenic, primarily released to the environment as a byproduct of nuclear fuel reprocessing.

Marine Debris in Green Sea Turtles along the Northern Coast of Taiwan

Sea turtles ingesting marine debris is a major problem worldwide. This is the first study ever done on the marine debris ingested by sea turtles in Taiwan, 191 dead green sea turtles from 2012 to 2019, mainly in northern coasts. We identified seven debris types and 15 colors. Plastic rope, soft and hard plastics, foam plastic and unidentified material were the most common ingested debris. White, transparent and mixture were either the common or the most common ingested color. Juveniles consumed more type of debris than the other age classes. Debris was found remain in the digestive tract for several weeks or longer prior to be found or excretion.

Solar hydrogen production from seawater splitting using mixed-valence titanium phosphite photocatalyst

A unique magnesium salt of titanium phosphite (MgTiP) was synthesized by the hydrothermal method and applied for the photocatalytic hydrogen evolution using seawater. The spent MgTiP was analyzed by XPS after photocatalytic reaction indicating that Ti3+ in MgTiP structure was oxidized to Ti4+ by photo-induced holes in a pure water environment, i.e., photo-corrosion. A sacrificial agent, 2 mM FeCl2 in the photocatalytic system, could enhance hydrogen evolution and prevent photo-corrosion of MgTiP. Thus this research conducted the reaction of photocatalytic hydrogen evolution using seawater. Two seawater sources were taken from the estuary of the Tamsui River and the east coast of Taiwan. The ions in seawater could act as a sacrificial agent. The result showed that the ions of seawater could enhance photocatalytic hydrogen evolution and also prevent MgTiP from photo-corrosion. The unique 12-membered ring (12 R) channels structure of MgTiP with tunable hexa-hydrated magnesium ions showed excellent photo-stability. The concentration of proton (pH) and chloride ions as hole scavenger were favorable factors. Its H2 production rate could reach up to 629.3 µmol·gcat−1·h−1 under simulated sunlight. Furthermore, the hydrogen evolution from photocatalytic seawater splitting showed better stability than pure water in a long-term test.

Evaluation of seasonal variation of major chemical parameters in the estuaries of southwestern Taiwan

Increased concentrations of heavy metals have been observed in the southwestern coast of Taiwan due to increasing human activities and economic growth; however, comprehensive studies investigating seasonal variations of major chemical parameters such as nutrient salts, trace metals, and physical parameters and their associations in the estuaries of the southwestern coast of Taiwan are scarce. The objective of this study was to investigate the seasonal variation of major chemical parameters and their associations in the coastal waters and estuaries of the southwestern coast of Taiwan. The sampling sites included the Pachang River, Erren River, Gaoping River, Donggang River, and Shiniu River. In addition, one coastal site at Yunlin was considered as a reference. The concentrations of nutrient salts and heavy metals show seasonal variations. According to DO level, Donggang river was considered to be slightly polluted, although the level of DO at Donggang river was significantly less than the other sampling sites. According to suspended solids, Pachang and Gaoping seemed to be slightly polluted. The concentrations of the tested heavy metals (Cd, Cr, Cu, Zn, Pb, and Hg) did not exceed the criteria of water pollution. Based on the results of cluster analysis, the tested marine parameters (DO, saturation percentage of DO, orthophosphate, and citrate) at Donggang River were significantly different from the other sampling sites.

Stratospheric Incursion as a Source of Enhancement of the Isotopic Ratios of Atmospheric N2O at Western Pacific

AbstractWe present analyses of nitrogen and oxygen isotopic ratios and site‐preference (SP) values of atmospheric nitrous oxide samples obtained from Taiwan in west Pacific. Air samples were collected during September 2013 to January 2016 from Taipei and during November 2011 to December 2014 from Keelung, located in the northeastern coast of Taiwan. The average values of δ15N, δ18O, and SP are 6.4 ± 0.3 ‰, 44.0 ± 0.4 ‰, and 17.1 ± 1.0 ‰, respectively, at Taipei and 6.4 ± 0.2 ‰, 44.6 ± 0.4 ‰, and 17.9 ± 1.3 ‰, for δ15N, δ18O, and SP respectively, at Keelung, comparable to the average values (6.6 ± 0.2, 44.2 ± 0.2, and 18.1 ± 0.5 ‰, scaled to year 2014) from Hateruma, an open ocean station in western Pacific. Strong temporal variations in the delta values, however, are seen. During a subtropical jet‐strengthening period in October to mid‐December 2014, the δ15N, δ18O and SP values increased at the rate of 0.006 ± 0.002 ‰/day, 0.010 ± 0.002 ‰/day and 0.008 ± 0.002 ‰/day, respectively at Taipei and 0.013 ± 0.005 ‰/day, 0.011 ± 0.005 ‰/day and 0.011 ± 0.027 ‰/day at Keelung. This suggests intrusion of air to the lower troposphere from the stratosphere where δ15N, δ18O and SP values are higher. This is consistent with earlier observations of oxygen isotope anomaly in atmospheric CO2 and elevated 35S in sulfate aerosols, indicating frequent stratospheric intrusions in this region. The observed δ15N and δ18O values, along with the oxygen isotope anomaly in CO2 and multiple sulfur isotopes in sulfate, can be used to constrain local emissions from the surface, improving our knowledge of anthropogenic contribution to the global budget of N2O.

Implication of single year seasonal sampling to genetic diversity fluctuation that coordinates with oceanographic dynamics in torpedo scads near Taiwan

Many fisheries management and conservation plans are based on the genetic structure of organisms in pelagic ecosystems; however, these structures tend to vary over time, particularly in cyclic ocean currents. We performed genetic analyses on the populations of the pelagic fish, Megalaspis cordyla (Osteichthyes: Carangidae) in the area surrounding Taiwan during 2000–2001. Genotyping was performed on M. cordyla collected seasonally around Taiwan as well as specimens collected from Singapore (Malacca strait) and Indonesia (Banda Sea). Gonadosomatic indices (GSI) revealed that M. cordyla does not spawn near Taiwan. Data related to the mitochondrial control region revealed that the samples from Singapore and Indonesia represented two distinct genetic cohorts. Genotyping revealed that during the summer (June–August 2000), the Indonesian variant was dominant in eastern Taiwan (presumably following the Kuroshio Current) and in the Penghu region (following the Kuroshio Branch Current). During the same period, the Singapore genotype was dominant along the western coast of Taiwan (presumably following the South China Sea Current); however, the number dropped during the winter (December–February 2001) under the effects of the China Coast Current. Divergence time estimates indicate that the two genetic cohorts split during the last glacial maximum. Despite the fact that these results are based on sampling from a single year, they demonstrate the importance of seasonal sampling in unravelling the genetic diversity in pelagic ecosystems.