Exploring late Pleistocene bioturbation on Yermak Plateau to assess sea-ice conditions and primary productivity through the Ethological Ichno Quotient.

Central Arctic, interglacial intervals have traditionally been associated with diverse and intense bioturbation, and abundant foraminifera, interpreted as indicating relatively low sea-ice concentrations and productive surface waters, while glacial intervals, typically barren, support the inverse. In this respect, the Yermak Plateau is anomalous. Biomarker studies suggest that glacial intervals were characterized by comparatively open water, while interglacials are marked by severe sea-ice conditions. Here we study downcore Ethological Ichno Quotient (EIQ) variations in trace fossils and bioturbation to test the hypothesis that different ethological classes vary in accordance with late Pleistocene changes in sea-ice extent, with deposit feeders increasing during reduced sea-ice cover and chemosymbiotic traces increasing during periods of thick perennial sea-ice conditions. Our results generally demonstrate that the abundance of traces like Planolites, Scolicia, and burrows produced by deposit feeders increase during episodes of seasonal sea-ice cover. In contrast, intervals with more severe sea-ice conditions are characterized by chemosymbiotic traces such as Chondrites and Trichichnus/Mycellia, suggesting lower food delivery and poorly ventilated bottom water conditions. The study thus confirms previous reconstructions of sea-ice conditions on the Yermak Plateau during interglacials, demonstrating that bioturbation variation provides insights into bentho-pelagic coupling under variable sea ice regimes in the Arctic Ocean.

Dataset on mesoplastics and microplastics abundances and characteristics from sandy beaches before and after typhoon events in northern Taiwan.

A comprehensive dataset is presented, which describes the abundance, shapes, and colors of meso- and microplastic particles collected from two sandy beaches situated on the north coast of Taiwan. The sampling of beach sand was conducted repetitively at fixed locations over a time period of 20 months, commencing from April 2018 to November 2019, with the aim of monitoring the variations in distribution and composition of plastic particles. A total of three adjacent transects perpendicular to the waterline were sampled, with bulk sand samples collected from 50 × 50 cm quadrats. The samples were subjected to drying, weighing, and sieving to obtain mesoplastic fractions (5-25 mm) and microplastic fractions (1-5 mm). Visual identification was employed to extract mesoplastic particles, while density separation using a saturated NaCl solution was utilized to extract microplastic particles. The particles were counted visually under a stereo microscope, and subsequently classified based on their shape and color. Any unknown particles were subjected to FTIR spectroscopy. Particle count data are presented as particles per unit area (0.25 m2) but can be converted to particles per kg d.w. by employing the weight of dry sand, as provided in the tables. The dataset encompasses a time series and delineates the changes in particle distribution and composition following extreme weather events. It can be utilized for further research by reanalyzing the data from different perspectives or by incorporating other factors.

Disentangling the impact of anthropogenic and natural processes on the environment in a subtropical subalpine lake catchment in northeastern Taiwan over the past 150 years.

Human activities impose significant changes on sedimentation processes and vegetation cover within lake catchments. However, the needed time for an anthropogenically disturbed natural state to be reversed back to its natural state by environmental protection programs is still ambiguous. Here we employ a multi-proxy approach to delineate major environmental disturbances such as logging and forest fires on the catchment in Cueifong Lake, a subtropical subalpine lake in northeastern Taiwan. X-ray Fluorescence (XRF) core scanning, bulk total organic carbon (TOC), bulk total nitrogen (TN), stable carbon isotope (δ13Corg) analysis, and macro-charcoal counting were utilized to reconstruct changes in the catchment environment based on a sediment core from Cueifong Lake. The results show that the element content changed distinctly around 1975 CE, which coincided with the onset of profound deforestation in the lake vicinity recorded in historical documents and aerial photos. After the cessation of the logging event, the detrital input increased, accompanied by decreasing C/N ratios and increasing δ13Corg values. This suggests that increased terrestrial nutrient input promoted algae growth. After the deforestation phase, our results imply a gradual recovery of elemental composition in the catchment environment. By extrapolating the XRF element records, we suggest that it might take >50 years for the sedimentary regime to reach its pre-logging baseline. In contrast to the depositional system, the C/N and δ13Corg shifted significantly - potentially irreversibly - towards an algae-dominant environment instead of recovering to the pre-logging condition. This could be due to both 1) the changes in the different vegetation species used for reforestation and/or 2) anthropogenically introduced fishes in the 1980s. This study proposes the first assessment of the needed recovery time for subtropical Asian subalpine forests after large-scale logging activity and thus provides an apparent reference for policy decisions on natural resource development and environmental protection.

Geochemical signatures of sedimentary and diagenetic processes in the trace fossil Rosselia from the Pliocene in Taiwan.

Trace fossils are structures left in a substrate as the result of the activities of living organisms. The producer of the spindle-shaped trace fossil Rosselia incorporates fine-grained organic rich material into concentric layers surrounding the central shaft. Because Rosselia is common in stressed shallow marine environments where the preservation potential of organic material is generally poor, these trace fossils may act as natural archives, recording changes in the provenance of organic material. Carbon isotope values of organic carbon preserved in laminae of the studied Rosselia typically lie around - 26‰, suggesting a primary terrestrial source. However, increased levels of S and Ca detected from XRF scanning of the laminae indicate that at least some marine material is incorporated. Examination of a diagenetically altered specimen also demonstrates that both elemental composition and δ13C values can be substantially altered diagenesis. Nevertheless, the long stratigraphic range of Rosselia, from the Cambrian to the Present, and its ubiquitous occurrence in stressed shallow-marine settings make it a potentially powerful tool to reconstruct variations in the input of organic material in settings otherwise devoid of fine-grained organic matter.

Potential and pitfalls of XRF-CS analysis of ion-exchange resins in environmental studies.

Detecting clandestine, intermittent release of heavy metal pollution into natural and man-made water ways is challenging. Conventional chemical methods are both labor intensive and expensive. A recent approach combining ion-exchange resins with the capabilities of X-ray fluorescence core scanners (XRF-CS) therefore is of great interest. In short, ion-exchange resin is deployed in the water using small sachets, the resin is then collected, dried, filled into sample holders and scanned using XRF-CS. Ion-exchange resins take up heavy metals in proportion to the concentration in the ambient water, with a correlation coefficient (R2) between concentration and XRF-CS counts better than 0.96 for most elements. However, a number of parameters influence the measurements. Different drying methods introduce differences in the XRF counts because of lattice bound water, resin shrinkage, and disaggregation of the resin particles. Furthermore, the newly developed sample carrier, which was constructed using 3D printed polymers, contains trace amounts of elements that may influence the sample measurements through edge effects and secondary fluorescence. In the tested sample carrier materials, substantial levels of Cr, Fe, Co, and Zn were detected, while Ca, Ti, Ni, Cu, Ga showed variable levels. Ba, Tl and Bi show very low levels, and Pb is only of importance in the PLA carrier. It is therefore necessary to streamline the analysis-process to ensure that the variations in sample treatment and drying and filling methods are minimized. It is also recommended that only spectra from the center of the compartments are used for the evaluation to avoid edge effects caused by secondary fluorescence of metals in the compartment walls. Although the technique of using ion-exchange resin sachets and XRF-CS analysis is only semi-quantitative, it is a cost effective and fast way to monitor large areas for environmental pollution, and the new sample carrier greatly contributes to make the process faster and less error prone.

Insolation-paced sea level and sediment flux during the early Pleistocene in Southeast Asia.

Global marine archives from the early Pleistocene indicate that glacial-interglacial cycles, and their corresponding sea-level cycles, have predominantly a periodicity of ~ 41 kyrs driven by Earth's obliquity. Here, we present a clastic shallow-marine record from the early Pleistocene in Southeast Asia (Cholan Formation, Taiwan). The studied strata comprise stacked cyclic successions deposited in offshore to nearshore environments in the paleo-Taiwan Strait. The stratigraphy was compared to both a δ18O isotope record of benthic foraminifera and orbital parameters driving insolation at the time of deposition. Analyses indicate a strong correlation between depositional cycles and Northern Hemisphere summer insolation, which is precession-dominated with an obliquity component. Our results represent geological evidence of precession-dominated sea-level fluctuations during the early Pleistocene, independent of a global ice-volume proxy. Preservation of this signal is possible due to the high-accommodation creation and high-sedimentation rate in the basin enhancing the completeness of the stratigraphic record.

A tale of shifting relations: East Asian summer and winter monsoon variability during the Holocene.

Understanding the dynamics between the East Asian summer (EASM) and winter monsoon (EAWM) is needed to predict their variability under future global warming scenarios. Here, we investigate the relationship between EASM and EAWM as well as the mechanisms driving their variability during the last 10,000 years by stacking marine and terrestrial (non-speleothem) proxy records from the East Asian realm. This provides a regional and proxy independent signal for both monsoonal systems. The respective signal was subsequently analysed using a linear regression model. We find that the phase relationship between EASM and EAWM is not time-constant and significantly depends on orbital configuration changes. In addition, changes in the Atlantic Meridional Overturning circulation, Arctic sea-ice coverage, El Niño-Southern Oscillation and Sun Spot numbers contributed to millennial scale changes in the EASM and EAWM during the Holocene. We also argue that the bulk signal of monsoonal activity captured by the stacked non-speleothem proxy records supports the previously argued bias of speleothem climatic archives to moisture source changes and/or seasonality.

The 20-million-year old lair of an ambush-predatory worm preserved in northeast Taiwan.

The feeding behavior of the giant ambush-predator "Bobbit worm" (Eunice aphroditois) is spectacular. They hide in their burrows until they explode upwards grabbing unsuspecting prey with a snap of their powerful jaws. The still living prey are then pulled into the sediment for consumption. Although predatory polychaetes have existed since the early Paleozoic, their bodies comprise mainly soft tissue, resulting in a very incomplete fossil record, and virtually nothing is known about their burrows and behavior beneath the seafloor. Here we use morphological, sedimentological, and geochemical data from Miocene strata in northeast Taiwan to erect a new ichnogenus, Pennichnus. This trace fossil consists of an up to 2 m long, 2-3 cm in diameter, L-shaped burrow with distinct feather-like structures around the upper shaft. A comparison of Pennichnus to biological analogs strongly suggests that this new ichnogenus is associated with ambush-predatory worms that lived about 20 million years ago.

Microplastic pollution of the Tamsui River and its tributaries in northern Taiwan: Spatial heterogeneity and correlation with precipitation.

The microplastic pollution and its effects on ecosystem in the marine environment has been well studied over the past decade. In contrast, the impact of microplastic pollution in freshwater environments was understudied, e.g., only a few studies examined the amount and distribution of microplastic in rivers, as well as the contribution of rivers to the microplastic pollution in oceans. In this study we investigated the microplastic pollution in the Tamsui River and its tributaries in northern Taiwan. We collected samples with a manta net from the Tamsui River, the Dahan River, the Keelung River and the Xindian River every two weeks over a time period of three months in 2018. Additionally, we took samples from the Xindian River during a heavy rain event in February 2019. Microplastic particles in the size range of 0.3-5 mm were visually identified. Unknown particles were identified using FTIR spectroscopy. The extracted particles were counted and classified according to their shape and color. We found microplastic of varying amounts in each of the samples, which indicates a wide spread pollution in the Tamsui River and its tributaries. The amount varies between rivers and ranges in average from 2.5 ± 1.8 particles per m3 in the Xindian River to 83.7 ± 70.8 particles per m3 in the Dahan River. Our data shows a positive correlation between precipitation and amount of microplastic particles found in the rivers. Moreover, in each river we could observe a large spatial and temporal variation of the microplastic amount between the left, middle and right sections of the stream. Due to this heterogeneous distribution of particles, we suggest that samples for microplastic analysis should be taken from multiple places across a river, as well as over a certain period to account for the heterogeneous microplastic distribution in the river water.

Rainfall variations in central Indo-Pacific over the past 2,700 y.

Tropical rainfall variability is closely linked to meridional shifts of the Intertropical Convergence Zone (ITCZ) and zonal movements of the Walker circulation. The characteristics and mechanisms of tropical rainfall variations on centennial to decadal scales are, however, still unclear. Here, we reconstruct a replicated stalagmite-based 2,700-y-long, continuous record of rainfall for the deeply convective northern central Indo-Pacific (NCIP) region. Our record reveals decreasing rainfall in the NCIP over the past 2,700 y, similar to other records from the northern tropics. Notable centennial- to decadal-scale dry climate episodes occurred in both the NCIP and the southern central Indo-Pacific (SCIP) during the 20th century [Current Warm Period (CWP)] and the Medieval Warm Period (MWP), resembling enhanced El Niño-like conditions. Further, we developed a 2,000-y-long ITCZ shift index record that supports an overall southward ITCZ shift in the central Indo-Pacific and indicates southward mean ITCZ positions during the early MWP and the CWP. As a result, the drying trend since the 20th century in the northern tropics is similar to that observed during the past warm period, suggesting that a possible anthropogenic forcing of rainfall remains indistinguishable from natural variability.

Rapid assessment of heavy metal pollution using ion-exchange resin sachets and micro-XRF core-scanning.

Conventional pollution monitoring strategies for heavy metals are often costly and unpractical. Innovative sampling and analytical approaches are therefore needed to efficiently monitor large areas. This study presents a novel, simple, fast, and inexpensive method to monitor heavy metal pollution that uses cation-exchange resin sachets and the micro-XRF core-scanning technique (XRF-CS). The resin passive samplers act as concentrators of cationic species and can be readily deployed spatially and temporally to record pollution signals. The large number of analytical tasks are then overcome by the fast and non-destructive XRF-CS to precisely assess elemental concentrations. Quantifying element loading involves direct comparison with a set of identically prepared and scanned resin reference standards containing Ca, Ti, Cr, Mn, Ni, Cu, Zn, Pb. The results show that within the test range (from 0-1000 s mg kg-1), the calibration lines have excellent regressions (R2 ≥ 0.97), even at the shortest exposure time (1 s). A pilot field survey of a suspected polluted area in central Taiwan, where 30 resin sachets had been deployed, identified a pollution hot spot in a rapid and economical manner. Therefore, this approach has the potential to become a valuable tool in environmental monitoring and forensics.

Distribution and quantity of microplastic on sandy beaches along the northern coast of Taiwan.

Plastic pollution is now ubiquitous in the world's oceans, and studies have shown macroplastic and microplastic pollution of beaches in several East Asian countries. However, to our knowledge, no study of microplastic pollution has been conducted in Taiwan yet. Therefore, we collected sand samples from four beaches along the northern coast of Taiwan in 2015 and extracted microplastic particles using a saturated NaCl solution. Microplastic particles were identified using synchrotron-based FTIR spectroscopy. We recovered 4 to 532 particles from eight 0.0125m(3) samples, with a total of 1097 particles weighing 0.771g. A negative trend between the size of the particles and their numbers was documented. We thus established that microplastic pollution was ubiquitous along Taiwan's northern coast. Future research should more comprehensively sample beaches around the entirety of Taiwan's coast, and special emphasis should be placed on identifying different sources and movements of microplastic.