Southern Taiwan Strait Research Articles

First Record of Partial Albinism in the Chinese Fanray, Platyrhina Sinensis (Elasmobranchii: Myliobatiformes: Platyrhinidae)

A female albino fanray specimen was collected by trawl from the southern Taiwan Strait on April 11, 2022. This unique individual was identified as the Chinese fanray, Platyrhina sinensis (Bloch & Schneider, 1801), based on morphological identification and DNA barcoding. It was classified as partial albinism (leucism) due to the absence of pigmentation in the skin and normal pigmentation in the irises. This specimen represents the first reported case of albinism within the family Platyrhinidae, providing valuable insights for physiological and ecological research on albino fish.

Semidiurnal Internal Tide Interference in the Northern South China Sea

Multiwave interference plays a crucial role in shaping the spatial variations of internal tides. Based on a combination of in situ mooring and altimeter data, interference of semidiurnal internal tides was investigated in the northern South China Sea. Mooring observations indicate the observed kinetic-to-potential energy ratio and group speed are both relatively lower than the theoretical values of mode-1 semidiurnal internal tides, indicating the presence of partly-standing waves. This is consistent with the altimeter result that the mooring was located at the antinode within the interference pattern formed by the superposition of the westward and southward semidiurnal internal tides from the Luzon Strait and the continental slope of the southern Taiwan Strait. However, the kinetic-to-potential energy ratio and group velocity were notably changed when an anticyclonic eddy passed by the mooring. By employing the ray-tracing method, we identified that mesoscale processes may induce a phase difference in the semidiurnal internal tides between the Luzon Strait and the continental slope of the southern Taiwan Strait. This alteration further leads to changes in the positions of nodes and antinodes within the interference pattern of the semidiurnal internal tides.

Latitudinal pronounced variations in tintinnid (Ciliophora) community at surface waters from the South China Sea to the Yellow Sea: Oceanic-to-neritic species shift, biotic-abiotic interaction and future prediction

The oceanic-to-neritic species shift of microzooplanktonic tintinnids and their interaction with relevant abiotic variables are two crucial processes in the marine ecosystem. However, these processes remain poorly documented in China's marginal seas. In the summer of 2022, we investigated the community structure of pelagic tintinnids in surface waters from the South China Sea (SCS) to the Yellow Sea (YS), passing through the East China Sea (ECS). A number of 58 species from 23 genera were identified, with 36 and 22 species belonging to oceanic and neritic genera, respectively. The abundance proportion of oceanic and neritic genera exhibited a decreasing and increasing trend, respectively, from the SCS to YS. Furthermore, four distinctive tintinnid community groups were classified based on cluster analysis using tintinnid species and abundance data, and the position of southern Taiwan Strait was identified as the “Shift Point” for oceanic-to-neritic species dominance. The top two tintinnid species in each group showed distinct variations in body size. Additionally, multivariate biotic-abiotic statistical analyses revealed that temperature determined tintinnid species richness, while temperature, salinity, Si(OH)4, and Chl a determined tintinnid abundance. Our study provides a substantial foundation for recognizing the oceanic-to-neritic species shift of tintinnids in the China's marginal seas, and highlights the role of biotic-abiotic factors in driving biogeochemical fluxes and the potential response of microzooplankton to future climate change.

Direct Evidence of Standing Internal Tide West of the Luzon Strait Observed by a Large-Scale Observation Array

Abstract Using a large-scale observation array of 27 simultaneous pressure-recording inverted echo sounders (PIESs), the standing wave features of the mode-1 M2 internal tide west of the Luzon Strait (LS) were identified. These features exhibited nonmonotonic spatial phase shifts and half-wavelength amplitude modulation, resulting in spatially varying amplitudes under PIES observations, which have not been previously observed in field observations west of the LS. Satellite altimeter measurements also identified standing-wave patterns consistent with the PIES observations. These patterns emanated from interference between the northwestward and southeastward beams from the LS and the slope of the southern Taiwan Strait, respectively. Near the LS, the two beams superimposed into partial standing waves, whereas the superimposed waves tended to become perfect standing waves near the slope of the southern Taiwan Strait. The nodes and antinodes of the wave shifted under the influence of an anticyclonic eddy. The eddy-induced background current modified the phase speed of the internal tides, and the superimposed standing-wave nodes and antinodes deflected clockwise. The node shifted during three anticyclonic eddy events, and two stations on two sides of the wave node showed opposite variations in amplitude. Significance Statement The internal tidal constituent (M2) propagating in opposite directions can result in standing waves, which have been frequently observed in global oceans but were absent west of the Luzon Strait (LS). Our observations (based on a large-scale array west of the LS) discovered a standing M2 internal tide, which stems from interference between the northwestward beams emanating from the LS and southeastward beams from the slope of the southern Taiwan Strait. Anticyclonic eddies play important roles in adjusting the amplitude of internal tides by deflecting the standing-wave nodes and antinodes clockwise. The study facilitates the understanding of the energy distribution and mixing processes west of the LS and provides a fresh perspective on the dynamic relationship between mesoscale perturbations and internal tides.

Population structure and reproductive dynamics of the ridged swimming crab Charybdis natator in the southern Taiwan Strait of China: significant changes within 25 years

The ridged swimming crab Charybdis natator (Portunidae) is a commercially important crustacean species in China. The purpose of this study is to compare its population structure and reproductive pattern within the same fishing area (the southern Taiwan Strait) from two datasets over 25 years; one from 1994−1996 (the early years of the C. natator fishery) and the other from 2019. The overall sex ratio (male:female) changed from a male bias (1:0.76, p < 0.01) in 1994−1996 to a female bias (1:1.38, p < 0.01) in 2019. Male body sizes (carapace width, CW) were significantly larger than those of females in both datasets (p < 0.05). The average CW and body weight (BW) of males and females in 2019 were significantly smaller (p < 0.01) and lighter (p < 0.01) than those in 1994−1996. The maximum body size and the proportion of large-sized individuals (CW > 10 cm) decreased dramatically over 25 years. One spawning peak season was identified from each dataset, i.e., March−August 1994−1996 and February−April 2019, revealing a 1-month shift. The minimum body sizes for female maturation (carrying eggs) were 6.9 cm CW in 1994−1996 and 6.1 cm CW in 2019, an 11.6% reduction over 25 years. For the first time, the CW at 50% female maturation, the relationship between female absolute fecundity and CW, and egg diameters were obtained from the 2019 dataset, which can be applied in the future comparisons. Recent studies have revealed a consistent spawning peak in February–April for several commercially important crabs in the southern Taiwan Strait. These findings should be considered in crab fishery management. Furthermore, both fishery- and environment-associated factors influencing crustacean population structure and reproductive dynamics merit further investigation.

Habitat changes and catch rate variability for greater amberjack in the Taiwan Strait: The effects of El Niño–southern oscillation events

El Niño–Southern Oscillation (ENSO) is a crucial oceanographic phenomenon that leads to interannual fluctuations in the climate and ecosystem productivity of tropical and subtropical areas. These fluctuations affect the suitability of habitats for many commercial fish species. However, detailed information on the effects of this major phenomenon and the resulting environmental changes on the habitat and catch rates of the economically and ecologically crucial species of the greater amberjack (Seriola dumerili) in the Taiwan Strait (TS) is lacking. In this study, we employed a weighted habitat suitability index (HSI) modeling method and used remotely sensed marine environmental data as well as data from recorders in Taiwanese fishing vessels (in 2014–2019) to understand the effects of ENSO events on the habitat suitability and catch rates for greater amberjack in the TS. Analysis of variance revealed that environmental factors substantially influenced greater amberjack habitats and catch rates during ENSO events across seasons. The catch rates were high in spring and summer in the southern and northern TS and in autumn and winter in the southern TS. The catch rates were higher in spring, summer, and autumn (>9.0 kg/h) in El Niño years, and in winter, the catch rates were higher in normal years (>12.0 kg/h) and lower in La Niña years. The predicted HSI for the southern and northern TS revealed that greater amberjack populations were predominantly distributed at 20–24°N and 24–28°N, respectively. Opposite habitat suitability was synchronously found in spring and summer during ENSO events, with higher HSI values recorded in spring in El Niño and normal years and higher HSI values recorded in summer in La Niña years. In winter, the HSI values of the southern and northern TS were higher in El Niño and normal years and substantially lower in La Niña years. Habitat suitability was extremely low in autumn. These findings imply that ENSO events play a key role in regulating environmental conditions and affect the catch rates and habitat suitability for the greater amberjack in the TS.

Reproductive Biology of the Pacific Spadenose Shark Scoliodon Macrorhynchos, a Heavily Exploited Species in the Southern Taiwan Strait

AbstractThe reproductive biology of the heavily exploited Pacific Spadenose Shark Scoliodon macrorhynchos was studied by examining 246 males and 197 females, including 64 gestational individuals, caught by semi‐industrial fisheries using demersal trawling in the southern Taiwan Strait. Total length (LT) at 50% maturity (L50) was estimated at 464 mm LT for males and 429 mm LT for females. The annual reproductive cycle was determined based on the percentage of pregnant mature females and the concurrent vitellogenesis with embryonic development. Mating occurred from August to December, as evidenced by the presence of females with fresh mating injuries on their body surface and spermatozoa in the cloaca and uteri. The monthly change of embryo size indicated that parturition occurred between June and August after 5–6 months of gestation, with an LT of 190–218 mm at birth. The litter size, which ranged from 1 to 20 pups with a mean ± SD of 9.4 ± 3.9 pups (n = 64), was positively correlated with the maternal LT. Altogether, these findings provide valuable information that is needed for the adequate management and conservation of Pacific Spadenose Sharks in the southern Taiwan Strait and adjacent waters.

Modelling the structure and functioning of an upwelling ecosystem in the Southern Taiwan Strait, China

A first mass balance food web model was developed to parameterize and characterize the structure and functioning of the upwelling ecosystem in the Southern Taiwan Strait ( STWS ). The model representing the ecosystem state and trophic flows in 2001 includes 50 functional groups from primary producer to marine mammal and 6 fishing fleets. The basic outputs and trophic flows in the ecosystem are analyzed using ecological indicators. Results indicate that phytoplankton, zooplankton, benthos and shrimps are structuring groups while dolphins, top predatory fishes, seabirds, lizard fish, hairtail and mantis shrimps are the keystone groups within the ecosystem. Based on the maturity indicators, STWS is at a mature state. An analysis of control mechanisms indicates that the top-down effect was the primary ecosystem control mechanism, although bottom-up effect was also in play. In addition, fishing impacts were analyzed throughout the food web. Such modelling of the structure and functioning of ecosystem provides basic information for stakeholders and policy-makers to implement ecosystem-based management. • The first mass balance model in Southern Taiwan Strait (STWS) is developed. • The structure and functioning of STWS are characterized. • The top-down effect is the main mechanism of ecosystem control in STWS. • The bottom-up effect can be enhanced in the STWS due to the upwelling effect.

Exploring Seasonal and Annual Nitrogen Transfer and Ecological Response in River‐Coast Continuums Based on Spatially Explicit Models

AbstractPerturbed nutrient balances in watersheds may eventually impact the marine ecosystem, but this river‐coast coupling is poorly understood. Monthly dissolved inorganic nitrogen (DIN) fluxes from seven major rivers in China were calculated by a global river nutrient model (IMAGE‐GNM), and then used in a regional ocean model system (ROMS) to explore changes in surface chlorophyll a (Chla) in the plume area (salinity <33) of the Taiwan Strait (TWS) in 2001–2010. Model results showed that river N input increased surface Chla by a factor of 2.1–2.7, revealing a clear eutrophic response. Without river N input, there was only one Chla peak in fall driven by current upwelling N. In contrast, sufficient river N supply and optimum temperature (above 20°C) likely caused another Chla peak (spring bloom) in the northern TWS (NTWS). The difference in the timing of spring blooms (Chla maxima) between the southern TWS (STWS) and the NTWS (April and May, respectively) may be explained by faster growth of phytoplankton at higher temperatures. Diagnostic analysis suggested that DIN was the main factor controlling interannual variation of Chla in the STWS, but only in the wet season in the NTWS. In the NTWS, reduced Chla in winter was mainly due to mixing by the strong northeast monsoon and lower temperatures. This study implies that the STWS is more sensitive to further increases in riverine N export and highlights the importance of fluvial N inputs in phytoplankton dynamics and the unique phenological features in the TWS.

Population, Reproductive and Fishery Dynamics of Spotted Box Crab (Calappa philargius), a New Claw-Only Fishery Species, in the Southern Taiwan Strait, China

The spotted box crab Calappa philargius (Calappidae) is an increasingly consumed species in China, mainly sourced from a claw-only fishery. Being a not well-characterized species in the literature, this study is warranted to inform sustainable management approaches. Here we report on the first in-depth overview on biology and fishery dynamics of C. philargius in the southern Taiwan Strait of China. Whole body crabs (N = 1,009) were collected monthly from January to December 2019 from trawlers, operating in the southern Taiwan Strait; sample collection was absent from May to July because of the national fishing moratorium regulation. Sex ratio, growth pattern, size at maturity and fecundity were estimated. The overall male: female ratio was 1: 1.47, significantly differing from the 1: 1 (p < 0.01); monthly sex ratio variations were also significant (p < 0.01), suggesting possible seasonal sexual segregation. We found the carapace widths (CW) of males were significantly larger than those of females (p < 0.01). Based on the occurrence and percentages of berried females, we identified twin spawning events in January–April and August–October with the overall peak occurring in February. Size at 50% female maturity was 11.47 cm CW. Female absolute fecundity was significantly related to CW via a power function relationship (N = 14, p < 0.01). The estimated average claw yield was 36.28 ± 3.07% of the whole body weight (N = 95), irrespective of sex and size (p > 0.5). Capture and trade data of C. philargius using trawl and trap fishing gears were documented to characterize claw-only fishery dynamics for future research and sustainable use.

Submarine topography-related spatial variability of the southern Taiwan Strait sands (East Asia)

The Taiwan Strait serves as a link between the East China Sea and South China Sea in East Asia. Complex ocean dynamics, huge sediment inputs and distinct tectonic, climatic and bedrock lithological settings of the two sides of the strait make it ideal for sediment source-to-sink studying. While mud sediments in the strait have been well investigated, sand composition and provenance remain understudied. Here, we present framework petrography and heavy mineral data of sands from the southern Taiwan Strait and the adjacent representative rivers to characterize sand provenance and depositional mechanisms. As expected, the SE China river sands are dominated by quartz and feldspar, whereas sands from the westward-flowing mountainous rivers in Taiwan are rich in lithic fragments and heavy minerals of metamorphic origin. The southern Taiwan Strait sands show significant spatial variations in composition and texture of the framework grains and heavy minerals. Framework grain-based provenance modeling results show that sands in the southwest margin of Taiwan Strait (water depth of 30–60 m) are mainly supplied by SE China rivers. Taiwan mountainous rivers made prominent contributions to the central-western Taiwan Strait (40–60 m) and the south of Taiwan Shoal (below 50 m), both of which are far away from the Taiwan island (ca. 100–300 km away). Furthermore, sands from the Taiwan Shoal (20–30 m) show extremely high compositional maturity and are mainly composed of coarse, rounded quartz. These sands, previously proposed as relict sediments, have been intensely altered by modern high-energy hydrodynamic conditions and can also be interpreted as palimpsest sediments. These results demonstrate that modern river-derived sands are eventually deposited in relatively deep-water regions in the strait, rather than the shallow regions (Taiwan Shoal). We propose that the sand composition and distribution are closely related to the submarine topography of the Taiwan Strait. Combining previous mud belt investigations, we suggest that sands and muds tend to have different fates in shallow continental shelves with complex climate, ocean current and seafloor landform conditions. This study also highlights the importance of both modern and relict sands in the strait and our findings are important to better understanding of shelf sedimentary systems with huge river-sediment-input and high wave/tidal-current-energy.

A bioeconomic approach towards improved fishery management of Monomia haanii in the southern Taiwan Strait, China

Red swimming crab, Monomia haanii, is one of China’s most valuable crab export products, but the fishery is managed with very limited scientific information. There is currently no analytical stock assessment for this little studied, but highly sought-after species. Here, a new equilibrium-based bioeconomic model was developed and applied to the M. haanii fishery in the southern Taiwan Strait, China to assess the performance of the current management approach in terms of revenue, yield, and egg production. Because the species is short-lived and grows rapidly, simulations were conducted to evaluate whether temporal allocation of fishing effort can improve performance along these dimensions by optimizing the tradeoffs between growth and mortality. Overall, we found that M. haanii is both highly productive and heavily exploited. Rapid harvest of sublegal individuals and females in the first half of the fishing season (August-December) after the national summer fishing moratorium, results in reduced yield, revenue, and egg production relative to management approaches that either spread fishing mortality throughout the year enabling more somatic growth, or target larger crabs. These outcomes were robust over a variety of model sensitivity scenarios, including changes in the timing of settlement, growth rate, and fishery selectivity. Evaluating such tradeoffs will be essential for sustainable management of Chinese swimming crabs in the face of heavy fishing pressure and environmental change.

Distribution and Transformation of Mercury in Subtropical Wild-Caught Seafood from the Southern Taiwan Strait.

Wild-caught seafood contains significant amounts of mercury. Investigating the mercury accumulation levels in wild-caught seafood and analyzing its migration and transformation are of great value for assessing the health risks of mercury intake and for the tracking of mercury sources. We determined the concentrations and stable mercury isotopic compositions (δ202Hg, Δ199Hg, Δ200Hg, and Δ201Hg) of 104 muscle samples collected from 38 species of seafood typically harvested from the Taiwan Shallow Fishing Ground (TSFG), Southern Taiwan Strait. Overall, the concentrations of total mercury (THg) and methylmercury (MeHg) ranged from 11 to 479 ng/g (dry weight, dw) and 10 to 363 ng/g (dw), respectively, and were below the threshold value established by the USEPA and the Chinese government. Demersal and near-benthic species accumulated more mercury than pelagic or mesopelagic species. The characteristics of mercury isotopes in wild-caught marine species differed in terms of vertical and horizontal distribution. Considering the known peripheral land sources of mercury (Δ199Hg ≈ 0), the mercury in seafood from the TSFG (Δ199Hg > 0) did not originate from anthropogenic emissions. The ratio of Δ199Hg and Δ201Hg (1.18 ± 0.03) suggested that the photoreduction of Hg (II) and the photo-degradation of MeHg equally contributed to mass-independent fractionation. Based on the values of Δ199Hg/δ202Hg (1.18 ± 0.03), about 67% of the mercury in seawater had undergone microbial demethylation prior to methylation and entering the seafood. Additionally, the vertical distribution of Δ200Hg in seafood from different water depths implies that mercury input was in part caused by atmospheric deposition. Our results provide detailed information on the sources of mercury and its transfer in the food web in offshore fishing grounds.

Genome-Scale Phylogenetic and Population Genetic Studies Provide Insight Into Introgression and Adaptive Evolution of Takifugu Species in East Asia.

As a typical marine adaptive radiation species, most Takifugu species are widely distributed in East Asian offshore, which have diversified morphological characteristics and different ecological habits. The phylogenetic relationship and population structure of the Takifugu species was complicated because of incomplete lineage sorting, widespread hybridization and introgression. Therefore, to systematically clarify the phylogenetic relationships of Takifugu genus, explore the introgression and natural hybridization between different Takifugu species, and detect the selective signatures in the adaptive evolution of diversified traits, whole-genome resequencing was used in 122 Takifugu samples from 10 species. Phylogenetic analysis showed solid sister-group relationships between Takifugu bimaculatus and Takifugu flavidus, Takifugu oblongus, and Takifugu niphobles, Takifugu rubripes, and Takifugu obscurus, Takifugu xanthoptreus, and Takifugu ocellatus. Further admixture analysis indicated the divergence of T. obscurus population and the bidirectional gene flow between T. bimaculatus and T. flavidus. Using species-specific homozygous genetic variance sites, we detected the asymmetric introgression between T. bimaculatus and T. flavidus at China East sea and southern Taiwan Strait. By genome-scale genetic diversity scanning, we detected two copies of syt1, zar1 and tgfbr1 related to the semilunar reproduction rhythm in T. niphobles, involved in memory formation, embryo maturation and female reproduction. Furthermore, we also found lots of T. niphobles specific mutations in CDS region of circadian rhythm related genes and endocrine hormone genes. For Takifugu species, our research provides reliable genetic resources and results for the phylogeny, introgression, hybridization and adaptive evolution, and could be used as a guide for the formulation of the protection and proliferation release policies.

Assessing Summertime Primary Production Required in Changed Marine Environments in Upwelling Ecosystems Around the Taiwan Bank

The Taiwan Bank (TB) is located in the southern Taiwan Strait, where the marine environments are affected by South China Sea Warm Current and Kuroshio Branch Current in summer. The bottom water flows upward along the edge of the continental shelf, forming an upwelling region that is an essential high-productivity fishing ground. Using trophic dynamic theory, fishery resources can be converted into primary production required (PPR) by primary production, which indicates the environmental tolerance of marine ecosystems. This study calculated the PPR of benthic and pelagic species, sea surface temperature (SST), upwelling size, and net primary production (NPP) to analyze fishery resource structure and the spatial distribution of PPR in upwelling, non-upwelling, and thermal front (frontal) areas of the TB in summer. Pelagic species, predominated by those in the Scombridae, Carangidae families and Trachurus japonicus, accounted for 77% of PPR (67% of the total catch). The benthic species were dominated by Mene maculata and members of the Loliginidae family. The upwelling intensity was the strongest in June and weakest in August. Generalized additive models revealed that the benthic species PPR in frontal habitats had the highest deviance explained (28.5%). Moreover, frontal habitats were influenced by NPP, which was also the main factor affecting the PPR of benthic species in all three habitats. Pelagic species were affected by high NPP, as well as low SST and negative values of the multivariate El Niño–Southern Oscillation (ENSO) index in upwelling habitats (16.9%) and non-upwelling habitats (11.5%). The composition of pelagic species varied by habitat; this variation can be ascribed to impacts from the ENSO. No significant differences were noted in benthic species composition. Overall, pelagic species resources are susceptible to climate change, whereas benthic species are mostly insensitive to climatic factors and are more affected by NPP.

Southward spreading of the Changjiang Diluted Water in the La Ni\xf1a spring of 2008

The La Niña of 2007/2008 was particularly strong, so was the southward flow of the cold, nutrient-rich Changjiang (Yangtze River) Diluted Water (CDW) when the winter monsoon started to blow in the fall. Here we use shipboard data in 2008 in two transects, one in the southwestern East China Sea and one in the southern Taiwan Strait, to show that as late as April in 2008 the CDW was still clearly identifiable when the winter monsoon had weakened. Waters as cold as 16 °C with a salinity lower than 30 still occupied the southwestern East China Sea. Waters of 17 °C and S < 32 could also be found off the coast of China in the central Taiwan Strait. The concentration of NO3 + NO2 was higher than 18 μmol L−1 at both places, which was as much as 40 times higher than the northward moving South China Sea (SCS) water to the east. As a result, the Changjiang River plume may be a significant source of nutrients, particularly N, to the oligotrophic, N-poor SCS, especially in the La Niña years. Indeed, colder and more turbid CDW was more intense and went farther south in 2008 compared with the normal springs of 2006, 2007 and 2009.

Reproductive dynamics of a swimming crab (Monomia haanii) in the world’s crab basket

Red swimming crab Monomia haanii is an important export fishery in southern China. M. haanii is mainly sold as lump crabmeat, generating an annual trade of tens of millions of US dollars over the last decade. For such a commercially important crab species, little attention has been paid to the sustainable use of the stocks and there remains much to learn about its biology and ecology. Monthly fishery-dependent samplings were conducted from August 2018 to April 2019 from bottom trawler catches obtained in the southern Taiwan Strait waters to characterize the biological attributes of M. haanii (N = 3222 individuals). Growth parameters, fecundity, sex ratios and maturity ogives were estimated, and spawning dynamics were characterized. The overall male: female ratio was 1: 1.07; however, significant variations monthly were detected (p < 0.01). Consistent with other portunids, sexual dimorphism with males typically reaching a larger average size was confirmed (carapace width, CW) (p < 0.01). Mature females (carrying eggs on abdominal pleopods) were found in all months sampled, with one clear peak spawning season in February―April and a possible second peak around August. Size at 50 % female maturity was 6.3 cm CW. Female absolute fecundity (Fa) was significantly related to CW via a power function relationship (N = 72, p < 0.01). The estimated average meat yield was 18.46 % (N = 93), irrespective of sex and size (0.1>p > 0.05). These results provide the first in-depth characterization of M. haanii and may pave a way towards the first M. haanii stock assessment.

Observation of continental shelf wave propagating along the eastern Taiwan Strait during Typhoon Meranti 2016

This study is the first to depict typhoon-induced continental shelf wave (CSW) propagation in the eastern Taiwan Strait (TWS) during the passage of Typhoon Meranti in 2016 using tidal gauge data and along-track satellite altimeter data. The strong amplitude response of sea level oscillations (within the range of 0.30–0.54 m) as a free, barotropic CSW after Meranti, which impacted the TWS, was clearly detected in time and frequency (in bands of 64–81 h) using wavelet and cross-wavelet analyses. The measured group and phase speeds were consistent with the dispersion curves for CSW with the first-mode derived from the cross-shelf sections of the eastern TWS, with the mean speeds reaching 3 and 5.6±0.7 m/s, respectively. Coincidentally, the typhoon-induced sea level anomaly (SLA) was also captured by the satellite altimeter before this CSW entered into the TWS. Using the theoretical cross-shore CSW modes to fit the SLA data, the results indicated that the first three wave modes can interpret this CSW event appeared in the southern TWS very well, with the first mode being the dominant one.

Giant sand waves on the Taiwan Banks, southern Taiwan Strait: Distribution, morphometric relationships, and hydrologic influence factors in a tide-dominated environment

Giant sand waves (heights >10 m) are widely developed on the Taiwan Banks, the distribution pattern, morphotypes and morphometric relationships of which have not yet been fully clarified. Based on multi-beam bathymetric swath data covering 780 line km of survey track, giant sand waves with heights up to 22.5 m and wavelengths up to 2115 m have been recorded. The relationship between height (H) and wavelength (L) of the complete data set follows the regression trend of Hmean = 0.0625 L0.8152 (r = 0.94), which is in good general agreement with a previously determined average global trend of Hmean = 0.0677 L0.8098. This global trend did not include any data from the China seas. The giant sand waves have been grouped into four morphotypes, namely double-crested, symmetric, symmetric-asymmetric and asymmetric forms. The individual bedform morphotypes and their spatial distribution were investigated in relation to water depth, textural characteristics of the sediment, and the hydrodynamic conditions recorded by several 25-hour repeated ship-based current observations. The relationship between mean water depth (D) and mean sand wave height (H) and mean wavelength (L) on the Taiwan Banks are Hmean = 0.29D (r = 0.35) and Lmean = 36D (r = 0.42), respectively. With increasing water depth, the shape of the sand wave becomes gentler. It is found that the coarser sediment (median grain size of 0.51–0.54 mm) and stronger flow in the present study may contribute to the larger H/D and L/D ratios at the given water depths than other sand wave fields. And flows of varying from equal to unequal northerly and southerly components correspond with sand waves from symmetrical to asymmetrical forms. A decrease in velocity and a veering in direction of flows have been observed over the giant sand waves, indicating the interaction between large bedforms and the near-bed water layer in the study area.

Climate Change Characteristics and Adaptation in the offshore East China Sea from 1979 to 2017

Wang, K.; Feng, X.; Zhang, H.; Li, Z.; Fan, G., and Yu, Z., 2020. Climate change characteristics and adaptation in the offshore East China Sea from 1979 to 2017. In: Zheng, C.W.; Wang, Q.; Zhan, C., and Yang, S.B. (eds.), Air-Sea Interaction and Coastal Environments of the Maritime and Polar Silk Roads. Journal of Coastal Research, Special Issue No. 99, pp. 54-59. Coconut Creek (Florida), ISSN 0749-0208.The climate change characteristics and adaptation abilities of the offshore East China Sea area are very important issues against the backdrop of the Maritime and Polar Silk Roads strategy. Based on meteorological observation data and reanalysis data, the spatial distribution and temporal variation characteristics of sea surface temperature (SST), sea surface salinity (SSS) and winds in the offshore East China Sea area were analyzed. From 1979 to 2017, the offshore average SST increased by 0.18°C/10 a as a whole. The average SSS showed an interdecadal cycle from 1980 to 2017 with a peak in 2005 (34.54 g/kg) and a trough in 1995 (34.26 g/kg). The lowest offshore SSS was 34.0 g/kg in the southern Korean Peninsula and the southern Taiwan Strait, while the highest offshore SSS was 34.8 g/kg in the low-latitude Pacific offshore area. The climatic characteristics annual accumulated gale days, annual local maximum wind speed, absolute maximum wind speed and average wind speed from 1971 to 2017 were analyzed, which showed that the influence of gales on Zhejiang was more serious than their influence on the other provinces in East China. In addition, decision-making strategies for climate change adaptation are discussed to provide a scientific reference for controlling the risks of climate change to the East China coastal zone and the Maritime Silk Road strategy.