Acta Oceanologica Sinica最新文献

Generally, a teleostean group (e.g., family or genus) owns one type or a set of similar mitochondrial gene arrangement. It is interesting, however, that four different types of gene arrangement have been found in the mitochondrial genome (mitogenome) of Cynoglossidae species. So far, the possible mechanisms of mitogenomic gene rearrangement and its potential implications have aroused widespread attention and caused lots of controversy. Here, a total of 21 Cynoglossidae mitogenomes and a newly sequenced mitogenome of Cynoglossus puncticpes (Pleuronectiformes: Cynoglossidae) were compared. The length ranges from 16 417 bp to 18 369 bp, which is mainly caused by the length heteroplasmy of control region (CR). Further analysis reveals that the difference of tandem repeats acts as a determining factor resulting in the length heterogeneity. Like most gene rearrangements of Cynoglossinae mitogenomes, tRNA-Gln gene encoded by the L-strand has translocated to the H-strand (Q inversion), accompanied by the translocation of CR in C. puncticpes mitogenome. The typical IQM order (tRNA-Ile-Gln-Met) changed to QIM order. Tandem duplication/random loss and mitochondrial recombination were accepted as the most possible models to account for the rearrangements in C. puncticpes mitogenome. Phylogenetic trees showed a strong correlation between the gap spacer in the rearranged QIM area and phylogeny, which provides a fresh idea for phylogenetic studies in future.

Marine spatial planning (MSP) is designed to divide the sea area into different types of functional zones, to implement corresponding development activities. However, the long-term impacts of anthropogenic activities associated with MSP practice on the marine microbial biosphere are still unclear. Yalu River Estuary, a coastal region in northeast of China, has been divided into fishery & agricultural (F&A) zone, shipping & port (S&P) zone and marine protected area (MPA) zone by a local MSP guideline that has been run for decades. To examine the effects of long-term executed MSP, benthic bacterial communities from different MSP zones were obtained and compared in this study. The results revealed significant differences in the bacterial community structure and predict functions among different zones. Bacterial genera enriched in different zones were identified, including SBR1031 in MPA, Woeseia and Sva0996 in S&P, and Halioglobus in F&A. In addition, correlations between some bacterial genera and sediment pollutants were uncovered. Furthermore, bacteria related to sulphide production were more abundant in the F&A zone, which was according to the accumulation of sulphides in this area. Moreover, bacteria associated with chemoheterotrophy and fermentation were more predominant in the S&P zone, consistent with high levels of organic matter and petroleum caused by shipping. Our findings indicated benthic bacterial communities could bring to light the anthropogenic activity footprints by different activities induced by long-term MSP practice.

Planktonic foraminifer Globigerinoides ruber (white) and Trilobatus sacculifer are the most frequently used mixed-layer dwelling species for reconstructing past oceanic environments. Specifically, the Mg/Ca ratios of these two foraminiferal species have been used for reconstructing tropical/subtropical changes in sea surface temperature (SST). However, these two species have different morphotypes, of which the spatial and temporal differences in Mg/Ca ratios and their influencing factors are still unclear. Our objective is to investigate the potential differences between the Mg/Ca ratios of these different morphotypes of G. ruber (white) and T. sacculifer in the western Philippine Sea (WPS) and determine their implications for the reconstruction of SST and upper-ocean structure. Mg/Ca measurements are made on two basic morphotypes of G. ruber (white) [sensu stricto (s.s.) and sensu lato (s.l.)] and T. sacculifer [with (w) and without (w/o) a sac-like final chamber] on samples of Site MD06-3047B from the WPS. Our results reveal that Mg/Ca ratios of different G. ruber morphotypes show consistent differences; and those of T. sacculifer morphotypes show staged variations since MIS 3. It is suggested to select a single morphotype for reconstructing SST changes using the Mg/Ca ratios of G. ruber and T. sacculifer in the WPS. Furthermore, the Mg/Ca ratios between G. ruber s.s. and G. ruber s.l. [Δ(Mg/Ca)_{G.ruber s.s.−s.l.}] downcore MD06-3047B covaries with indexes of summer monsoon. Combining with the core-top results, showing regional variation of differences in the Δ(Mg/Ca)_{G.ruber s.s.−s.l.} over the western tropical Pacific, we propose that Δ(Mg/Ca)_{G.ruber s.s.−s.l.} may tend to reflect summer mixed layer depth.

In this study, Ulva prolifera protein was used for preparing angiotensin-I converting enzyme (ACE)-inhibitory peptide via virtual gastrointestinal digestion and in silico screening. Some parameters of the obtained peptide, such as inhibition kinetics, docking mechanism, stability, transport pathway, were explored by Lineweaver-Burk plots, molecular docking, in vitro stimulate gastrointestinal (GI) digestion and Caco-2 cells monolayer model, respectively. Then, a novel anti-ACE peptide LDF (IC₅₀, (1.66 ± 0.34) µmol/L) was screened and synthesized by chemical synthesis. It was a no-competitive inhibitor and its anti-ACE inhibitory effect mainly attributable to four Conventional Hydrogen Bonds and Zn701 interactions. It could keep activity during simulated GI digestion in vitro and was transported by peptide transporter PepT1 and passive-mediated mode. Besides, it could activate Endothelial nitric oxide synthase (eNOS) activity to promote the production of NO and reduce Endothelin-1 (ET-1) secretion induced by Angiotensin II (Ang II) in Human Umbilical Vein Endothelial Cells (HUVECs). Meanwhile, it could promote mice splenocytes proliferation in a concentration-dependent manner. Our study indicated that this peptide was a potential ingredient functioning on vasodilation and enhancing immunity.

The chemical diversity of scleractinian corals is closely related to their physiological, ecological, and evolutionary status, and can be influenced by both genetic background and environmental variables. To investigate intraspecific variation in the metabolites of these corals, the metabolomes of four species (Pocillopora meandrina, Seriatopora hystrix, Acropora formosa, and Fungia fungites) from the South China Sea were analyzed using untargeted mass spectrometry-based metabolomics. The results showed that a variety of metabolites, including amino acids, peptides, lipids, and other small molecules, were differentially distributed among the four species, leading to their significant separation in principal component analysis and hierarchical clustering plots. The higher content of storage lipids in branching corals (P. meandrina, S. hystrix, and A. formosa) compared to the solitary coral (F. fungites) may be due to the high densities of zooxanthellae in their tissues. The high content of aromatic amino acids in P. meandrina may help the coral protect against ultraviolet damage and promote growth in shallow seawater, while nitrogen-rich compounds may enable S. hystrix to survive in various challenging environments. The metabolites enriched in F. fungites, including amino acids, dipeptides, phospholipids, and other small molecules, may be related to the composition of the coral’s mucus and its life-history, such as its ability to move freely and live solitarily. Studying the chemical diversity of scleractinian corals not only provides insight into their environmental adaptation, but also holds potential for the chemotaxonomy of corals and the discovery of novel bioactive natural products.

The influence of Typhoon Kalmaegi on internal waves near the Dongsha Islands in the northeastern South China Sea was investigated using mooring observation data. We observed, for the first time, that the phenomenon of regular variation characteristics of the 14-d spring-neap cycle of diurnal internal tides (ITs) can be regulated by typhoons. The diurnal ITs lost the regular variation characteristics of the 14-d spring-neap cycle during the typhoon period owing to the weakening of diurnal coherent ITs, represented by O₁ and K₁, and the strengthening of diurnal incoherent ITs. Results of quantitative analysis showed that during the pre-typhoon period, time-averaged modal kinetic energy (sum of Modes 1–5) of near-inertial internal waves (NIWs) and diurnal and semidiurnal ITs were 0.62 kJ/m², 5.66 kJ/m², and 1.48 kJ/m², respectively. However, during the typhoon period, the modal kinetic energy of NIWs increased 5.11 times, mainly due to the increase in high-mode kinetic energy. At the same time, the modal kinetic energy of diurnal and semidiurnal ITs was reduced by 68.9% and 20%, respectively, mainly due to the decrease in low-mode kinetic energy. The significantly reduced diurnal ITs during the typhoon period could be due to: (1) strong nonlinear interaction between diurnal ITs and NIWs, and (2) a higher proportion of high-mode diurnal ITs during the typhoon period, leading to more energy dissipation.

The current velocity observation of LADCP (Lowered Acoustic Doppler Current Profiler) has the advantages of a large vertical range of observation and high operability compared with traditional current measurement methods, and is being widely used in the field of ocean observation. Shear and inverse methods are now commonly used by the international marine community to process LADCP data and calculate ocean current profiles. The two methods have their advantages and shortcomings. The shear method calculates the value of current shear more accurately, while the accuracy in an absolute value of the current is lower. The inverse method calculates the absolute value of the current velocity more accurately, but the current shear is less accurate. Based on the shear method, this paper proposes a layering shear method to calculate the current velocity profile by “layering averaging”, and proposes corresponding current calculation methods according to the different types of problems in several field observation data from the western Pacific, forming an independent LADCP data processing system. The comparison results have shown that the layering shear method can achieve the same effect as the inverse method in the calculation of the absolute value of current velocity, while retaining the advantages of the shear method in the calculation of a value of the current shear.

Abstract

The Bohai Sea (BS) is the unique semi-closed inland sea of China, characterized by degraded water quality due to significant terrestrial pollution input. In order to improve its water quality, a dedicated action named “Uphill Battles for Integrated Bohai Sea Management” (UBIBSM, 2018–2020) was implemented by the Chinese government. To evaluate the action effectiveness toward water quality improvement, variability of the satellite-observed water transparency (Secchi disk depth, Z_SD) was explored, with special emphasis on the nearshore waters (within 20 km from the coastline) prone to terrestrial influence. (1) Compared to the status before the action began (2011–2017), majority (87.3%) of the nearshore waters turned clear during the action implementation period (2018–2020), characterized by the elevated Z_SD by 11.6% ± 12.1%. (2) Nevertheless, the improvement was not spatially uniform, with higher Z_SD improvement in provinces of Hebei, Liaoning, and Shandong (13.2% ± 16.5%, 13.2% ± 11.6%, 10.8% ± 10.2%, respectively) followed by Tianjin (6.2% ± 4.7%). (3) Bayesian trend analysis found the abrupt Z_SD improvement in April 2018, which coincided with the initiation of UBIBSM, implying the water quality response to pollution control. More importantly, the independent statistics of land-based pollutant discharge also indicated that the significant reduction of terrestrial pollutant input during the UBIBSM action was the main driver of observed Z_SD improvement. (4) Compared with previous pollution control actions in the BS, UBIBSM was found to be the most successful one during the past 20 years, in terms of transparency improvement over nearshore waters. The presented results proved the UBIBSM-achieved remarkable water quality improvement, taking the advantage of long-term consistent and objective data record from satellite ocean color observation.

Composite analyses were performed in this study to reveal the difference in spring precipitation over southern China during multiyear La Niña events during 1901 to 2015. It was found that there is significantly below-normal precipitation during the first boreal spring, but above-normal precipitation during the second year. The difference in spring precipitation over southern China is correlative to the variation in western North Pacific anomalous cyclone (WNPC), which can in turn be attributed to the different sea surface temperature anomaly (SSTA) over the Tropical Pacific. The remote forcing of negative SSTA in the equatorial central and eastern Pacific and the local air-sea interaction in the western North Pacific are the usual causes of WNPC formation and maintenance. SSTA in the first spring is stronger than those in the second spring. As a result, the intensity of WNPC in the first year is stronger, which is more likely to reduce the moisture in southern China by changing the moisture transport, leading to prolonged precipitation deficits over southern China. However, the tropical SSTA signals in the second year are too weak to induce the formation and maintenance of WNPC and the below-normal precipitation over southern China. Thus, the variation in tropical SSTA signals between two consecutive springs during multiyear La Niña events leads to obvious differences in the spatial pattern of precipitation anomaly in southern China by causing the different WNPC response.

The southeastern Indian Ocean is characterized by the warm barrier layer (BL) underlying the cool mixed layer water in austral winter. This phenomenon lasts almost half a year and thus provides a unique positive effect on the upper mixed layer heat content through the entrainment processes at the base of the mixed layer, which has not been well evaluated due to the lack of proper method and dataset. Among various traditional threshold methods, here it is shown that the 5 m fixed depth difference can produce a reliable and accurate estimate of the entrainment heat flux (EHF) in this BL region. The comparison between the daily and monthly EHF warming indicates that the account for high-frequency EHF variability almost doubles the warming effect in the BL period, which can compensate for or even surpass the surface heat loss. This increased warming is a result of stronger relative rate of the mixed layer deepening and larger temperature differences between the mixed layer and its immediate below in the daily-resolving data. The interannual EHF shows a moderately increasing trend and similar variabilities to the Southern Annular Mode (SAM), likely because the mixed layer deepening under the positive SAM trend is accompanied by enhanced turbulent entrainment and thus increases the BL warming.