Convergence zones of coastal waters as hotspots for floating microplastic accumulation.

This study examines microplastic (MP, 1-5 mm) densities in convergence zones in a coastal sea, the Seto Inland Sea, comparing them to those of non-convergence zones and other areas. Notably, Seto convergence zones exhibit MP densities 40 to 300 times higher than non-convergence zones, with an extraordinary density of 3.7 ± 6.3 pieces m-3, similar to densities found in Tokyo Bay as known a MP hotspot. The predominant polymer found was expanded polystyrene, varying seasonally and peaking in summer. Juvenile fish associated with driftweed in these convergence zones face a risk of long-term MP exposure, potentially up to four months. This large number of MPs found in coastal convergence zones is similar to accumulation zones formed in the gyres of open oceans, with strong implications for detrimental effects on coastal marine life. However, these MPs are autochthonous, and may be manageable through local marine plastic waste management.

Seagrass contributes substantially to the sedimentary lignin pool in an estuarine seagrass meadow.

Shallow coastal ecosystems are reservoirs of carbon derived from allochthonous organic matter and autochthonous organic matter produced by microalgae and macrophytes. Carbon stored in vegetated coastal ecosystems has attracted broad attention as an important component of carbon sinks. Characterizing the source of carbon in sediments is essential for quantifying the carbon-sequestration function of shallow coastal ecosystems. In this study, we investigated the origins of organic matter using organic biomarkers (lignin phenols, fatty acids, cutin acids, diacids, and ω-hydroxy acids) in surface sediments in a seagrass-dominated lagoon (Furen Lagoon, Japan). Biomarkers derived from allochthonous vascular plants, such as long-chain fatty acids, showed higher concentrations near river mouths. Furthermore, biomarker signals indicated that sedimentary organic carbon originated in large part from degraded allochthonous vascular plants including roots. A Bayesian mixing model using the ratios of syringyl phenols to vanillyl phenols and cinnamyl phenols to vanillyl phenols indicated that up to about 65% of lignin in the sediments was derived from seagrass. This result indicates a substantial contribution of seagrass to the sedimentary lignin pool in an estuarine seagrass meadow. However, the percent contribution of seagrass to the lignin pool varied, with higher values near a tidal inlet and relatively low values near river mouths. Vertical profiles of organic biomarkers varied with the differences in degradability of organic compounds. Specifically, long-chain fatty acids decreased with increasing depth more than the other compounds, suggesting that they degraded more easily. Conversely, we observed a tendency for lignin phenols to be selectively preserved in the vertical sediment profiles. Our results show that sediment organic biomarkers can provide diverse information such as the composition and origins of organic carbon, the contribution of seagrass derived lignin, and the varying degrees of decomposition. This approach should bring new insights to the estimation of carbon in future blue carbon studies.

Tolerance of Tetraselmis tetrathele to High Ammonium Nitrogen and Its Effect on Growth Rate, Carotenoid, and Fatty Acids Productivity.

Microalgae can use either ammonium or nitrate for its growth and vitality. However, at a certain level of concentration, ammonium nitrogen exhibits toxicity which consequently can inhibit microalgae productivity. Therefore, this study is aimed to investigate the tolerance of Tetraselmis tetrathele to high ammonium nitrogen concentrations and its effects on growth rate, photosynthetic efficiency (F v /F m ), pigment contents (chlorophyll a, lutein, neoxanthin, and ß-carotene), and fatty acids production. Experiments were performed at different ammonium nitrogen concentrations (0.31-0.87 gL-1) for 6 days under a light source with an intensity of 300 µmol photons m-2 s-1 and nitrate-nitrogen source as the experimental control. The findings indicated no apparent enhancement of photosynthetic efficiency (F v/F m) at high levels of ammonium nitrogen ( NH 4 + -N) for T. tetrathele within 24 h. However, after 24 h, the photosynthetic efficiency of T. tetrathele increased significantly (p < 0.05) in high concentration of NH 4 + -N. Chlorophyll a content in T. tetrathele grown in all of the different NH 4 + -N levels increased significantly compared to nitrate-nitrogen (NO3-N) treatment (p < 0.05); which supported that this microalgal could grow even in high level of NH 4 + -N concentrations. The findings also indicated that T. tetrathele is highly resistant to high ammonium nitrogen which suggests T. tetrathele to be used in the aquaculture industry for bioremediation purpose to remove ammonium nitrogen, thus reducing the production cost while improving the water quality.

Comprehensive GCMS and LC-MS/MS Metabolite Profiling of Chlorella vulgaris.

The commercial cultivation of microalgae began in the 1960s and Chlorella was one of the first target organisms. The species has long been considered a potential source of renewable energy, an alternative for phytoremediation, and more recently, as a growth and immune stimulant. However, Chlorella vulgaris, which is one of the most studied microalga, has never been comprehensively profiled chemically. In the present study, comprehensive profiling of the Chlorella vulgaris metabolome grown under normal culture conditions was carried out, employing tandem LC-MS/MS to profile the ethanolic extract and GC-MS for fatty acid analysis. The fatty acid profile of C. vulgaris was shown to be rich in omega-6, -7, -9, and -13 fatty acids, with omega-6 being the highest, representing more than sixty percent (>60%) of the total fatty acids. This is a clear indication that this species of Chlorella could serve as a good source of nutrition when incorporated in diets. The profile also showed that the main fatty acid composition was that of C16-C18 (>92%), suggesting that it might be a potential candidate for biodiesel production. LC-MS/MS analysis revealed carotenoid constituents comprising violaxanthin, neoxanthin, lutein, ß-carotene, vulgaxanthin I, astaxanthin, and antheraxanthin, along with other pigments such as the chlorophylls. In addition to these, amino acids, vitamins, and simple sugars were also profiled, and through mass spectrometry-based molecular networking, 48 phospholipids were putatively identified.

Dataset of characteristic remanent magnetization and magnetic properties of early Pliocene sediments from IODP Site U1467 (Maldives platform).

This data article describes data of magnetic stratigraphy and anisotropy of isothermal remanent magnetization (AIRM) from "Magnetic properties of early Pliocene sediments from IODP Site U1467 (Maldives platform) reveal changes in the monsoon system" [1]. Acquisition of isothermal magnetization on pilot samples and anisotropy of isothermal remanent magnetization are reported as raw data; magnetostratigraphic data are reported as characteristic magnetization (ChRM).

Methyl Ether-Derivatized Sterols and Coprostanol Produced via Thermochemolysis Using Tetramethylammonium Hydroxide (TMAH).

Sterols are widely distributed in nature from lipids in organisms to sediments. As a conventional method, extraction and derivatization with TMS have been applied for sterol analysis, requiring a long preparation time for gas chromatography-mass spectrometry analysis. In this study, for sterol analysis, thermochemolysis using tetramethylammonium hydroxide (TMAH) was applied. This method performs hydrolysis and methylation simultaneously; thus, free and ether-bonding sterols can be analyzed as sterol methyl ethers in a relatively short time period. A sediment sample from a tideland (the Yatsu tideland, Japan) was analyzed using the TMAH method, and we detected more than 10 sterols, which include cholest-5-en-3ß-ol (cholesterol), 24-ethylcholest-5-en-3ß-ol (sitosterol), 24-methylcholesta-5,22E-3ß-ol (brassicasterol), 24-ethylcholesta-5,24(28)Z-dien-3ß-ol (isofucosterol), 4α,23,24-trimethyl-5α(H)-cholest-22E-en-3ß- ol (dinosterol), and 5ß(H)-cholestan-3ß-ol (coprostanol). The detection of the various sterols can be attributed to multiple natural and artificial sources around the Yatsu tideland. In this paper, the mass spectra of these sterols are provided together with an interpretation of their fragmentation patterns. Additionally, the fecal pollution in the Yatsu tideland is discussed in the context of the detection of coprostanol.

The abrupt onset of the modern South Asian Monsoon winds.

The South Asian Monson (SAM) is one of the most intense climatic elements yet its initiation and variations are not well established. Dating the deposits of SAM wind-driven currents in IODP cores from the Maldives yields an age of 12. 9 Ma indicating an abrupt SAM onset, over a short period of 300 kyrs. This coincided with the Indian Ocean Oxygen Minimum Zone expansion as revealed by geochemical tracers and the onset of upwelling reflected by the sediment's content of particulate organic matter. A weaker 'proto-monsoon' existed between 12.9 and 25 Ma, as mirrored by the sedimentary signature of dust influx. Abrupt SAM initiation favors a strong influence of climate in addition to the tectonic control, and we propose that the post Miocene Climate Optimum cooling, together with increased continentalization and establishment of the bipolar ocean circulation, i.e. the beginning of the modern world, shifted the monsoon over a threshold towards the modern system.