Marine macroalgal sulfated fucose-containing polysaccharides, like fucoidan, have drawn significant attention due to their biotechnological potentials, such as anti-cancer, antioxidant, and anti-cholinesterase activities. The fucoidan derived from brown macroalgae Sargassum angustifolium species (FSA) was investigated for its cytotoxic effects and alterations in cell proliferation, and cell cycle-related gene expression in the present study occurred on NB4 cell line. The results showed that FSA would induce p53, p21, pro-apoptotic genes and increase expression of the p15 gene as a cell arrest marker. Also, FSA inhibited the anti-apoptotic effect of the Bcl-2 gene and decreased dnmt-1 gene expression. FSA significantly exhibited potent 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity (p<0.05) with an IC₅₀ value of 0.157 mg/mL and showed moderate anti-acetylcholinesterase activity with an IC₅₀ value of 1.20 μg/mL. These results indicated the potential of FSA for the development of therapeutic or preventive agents of cancer and Alzheimer’s disease mainly through cytotoxic effect and AChE (acetylcholinesterase) inhibition as well as additional antioxidant capacities.

Assessments of phytoplankton diversity in Sabah waters, North Borneo, have primarily relied on morphology-based identification, which has inherent biases and can be time-consuming. Next-Generation Sequencing (NGS) technology has been shown to be capable of overcoming several limitations of morphology-based methods. Samples were collected from the Sepanggar Bay over the course of the year 2018 in different monsoon seasons. Morphology-based identification and NGS sequencing of the V8–V9 region of the 18S LSU rDNA were used to investigate the diversity of the phytoplankton community. Microscopy and NGS showed complementary results with more diatom taxa detected by microscopy whereas NGS detected smaller and rarer taxa. The harmful algal genera in the study site comprised of Skeletonema, Margalefidinium, Pyrodinium, Takayama, and Alexandrium as detected by NGS. This study showed that that an integrative approach of both morphological and molecular techniques could provide more comprehensive information about the phytoplankton community as the approach captured quantitative variability as well as the diversity of phytoplankton species.

We report for the first time the presence of local populations of the starfish Odontaster penicillatus in the regions of Atacama and Antofagasta, Chile. This finding indicates an extension of the distribution limit of 500 km with respect to the last observation made in 2007 in Isla Grande de Atacama. A total of 121 specimens of O. penicillatus were recorded at depths of between 8 m and 24 m. They were associated with rocky substrate and with different species of barnacles, sponges and bryozoans. The presence of O. penicillatus expands the knowledge of the benthic biodiversity of the region, and the development of studies on its ecological importance will be promoted.

In this paper, the intra-seasonal variability of the abyssal currents in the China Ocean Mineral Resources Association (COMRA) polymetallic nodule contact area, located in the western part of the Clarion and Clipperton Fraction Zone in the tropical East Pacific, is investigated using direct observations from subsurface mooring instruments as well as sea-surface height data and reanalysis products. Mooring observations were conducted from September 13, 2017 to August 15, 2018 in the COMRA contact area (10°N, 154°W). The results were as follows: (1) At depths below 200 m, the kinetic energy of intra-seasonal variability (20−100 d) accounts for more than 40% of the overall low-frequency variability, while the ratio reaches more than 50% below 2 000 m. (2) At depths below 200 m, currents show a synchronous oscillation with a characteristic time scale of 30 d, lasting from October to the following January; the energy of the 30-d oscillation increases with depth until the layer of approximately 4 616 m, and the maximum velocity is approximately 10 cm/s. (3) The 30-d oscillation of deep currents is correlated with the tropical instability waves in the upper ocean.

Resource exploitation in the Clarion-Clipperton Zone (CCZ) is of major research interest worldwide, but its influence on the environment is poorly understood, especially due to the lack of baseline values for metals in the surrounding sediment. This work aimed to establish the baseline values of 17 metals (Ba, Ca, K, Mg, Mn, Na, Ag, As, B, Cd, Co, Cr, Cu, Hg, Ni, Pb, and Zn) using normalization, the cumulative frequency curve method considering a total of 172 samples taken from 8 multitube cores and 1 box sediment core collected in the western CCZ during the COMRA-45 cruise campaign from August to September 2017. The baseline values of the evaluated metals were as follows: 1 932 mg/kg for Ba, 29 512 mg/kg for Ca, 18 150 mg/kg for K, 17 120 mg/kg for Mg, 6 747 mg/kg for Mn, 28 546 mg/kg for Na, 0.571 mg/kg for Ag, 5.00 mg/kg for As, 94.4 mg/kg for B, 0.626 mg/kg for Cd, 104 mg/kg for Co, 76.1 mg/kg for Cr, 370 mg/kg for Cu, 0.028 mg/kg for Hg, 190 mg/kg for Ni, 27.5 mg/kg for Pb and 156 mg/kg for Zn. Our findings would fill the baseline value gap in the study area and further improve accuracy of environmental impact assessments on the impact of resource exploitation.

Based upon cruise observations broadly covering the tropical North Pacific during July−November 2017, together with data obtained from the World Ocean Circulation Experiment Hydrographic Program, this study examined the distribution of dissolved inorganic nitrogen (DIN, nitrate (${{\rm {NO}}_3^-} $)+nitrite (${{\rm {NO}}_2^-} $)), dissolved inorganic phosphorus (DIP) and related N* (nitrogen-anomaly, N*=N−16P+2.9, where N and P are the concentrations of DIN (>1.0 μmol/L) and DIP (>0.1 μmol/L)), used as an index of N₂ fixation, in the upper 1 000 m of the water column. Nutrient concentrations displayed distinct spatial variability in the upper ocean but became relatively constant at a depth of 1 000 m: they were high at low latitudes and in the eastern region, with an obvious nutricline at ~150 m (DIN, ~32.0 μmol/L; DIP, ~2.4 μmol/L) and then generally increased with depth; they decreased markedly (DIN, ~1.2 μmol/L; DIP, ~0.1 μmol/L; at ~150 m) at high latitudes and in the western region, where a nutricline was not apparent. The N* index showed significant meridional and zonal variation, with the most negative values located at low latitudes and in the eastern region (~10°N, ~150°−170°E), while becoming positive towards the northwest (the north of ~18°N, ~160°E westward). A N* concentration larger than 2.0 μmol/L which often used as an indicator of N₂ fixation, was observed between 155°E and 165°E; N* values were 2.0 μmol/L to 6.0 μmol/L at ~15°−28°N, i.e., much higher than those in the southern sector (0−2.0 μmol/L at ~5°−10°N). Zonally, N* decreased gradually from west (−2.0 μmol/L to 4.0 μmol/L, ~145°−165°E) to east (−2.0 μmol/L to −8.0 μmol/L, ~155°W) along ~10°N, which was consistent with the distribution of Trichodesmium abundance and N₂ fixation rates. Furthermore, since such region was also supplied with aeolian deposition, high N* was probably not only induced by N₂ fixation but also influenced by iron and/or nitrogen deposition.

The flux of settling particles in the ocean has been widely explored since 1980s due to its important role in biogenic elements cycling, especially in the transport of particulate organic carbon (POC) in the deep sea. However, research in the seamount area of the oligotrophic subtropical Northwest Pacific Ocean is lacking. In this work, two sediment traps were deployed at the foot and another two at the hillside of Niulang Guyot from August 2017 to July 2018. The magnitude and composition of particle fluxes were measured. The main factors influencing the spatial variations of the fluxes were evaluated. Our results indicated a low particulate flux from Niulang Guyot area in the Northwest Pacific Ocean, reflecting low primary productivity of the oligotrophic ocean. The total mass flux (TMF) decreased from 2.57 g/(m²·a) to 0.56 g/(m²·a) with increasing depth from 600 m to 4 850 m. A clear seasonal pattern of TMF was observed, with higher flux in summer than that in winter. The peak flux of 26.52 mg/(m²·d) occurred in August at 600 m, while the lowest value of 0.07 mg/(m²·d) was shown in February at 4 850 m. The settling particles at the deep layers had similar biochemical composition, with calcium carbonate (CaCO₃) accounting for up to 90%, followed by organic matter and opal, characteristics of Carbonate Ocean. The POC flux decreased more rapidly in the twilight layer because of faster decomposition, remineralization, and higher temperature. A small fraction of POC was transported into the deep ocean by biological pump. Particle fluxes were mainly controlled by the calcareous ballasts besides the primary productivity of the surface water. The advection may be another important factor affecting the flux in the seamount area. The combination of settled matters rich in foraminiferal tests with topography and currents may be the reason for regulating the local abundance of benthos on seamounts. Our results will fill in the knowledge gap of sedimentation flux, improve the understanding of ecosystem in Niulang Guyot area, and eventually provide data support for the optimization of regional ecological modeling.

The Clarion-Clipperton Zone (CCZ) hosts one of the largest known oceanic nodule fields worldwide and is regulated by the International Seabed Authority. A baseline assessment of diversity and distribution patterns is essential for reliable predictions of disturbed ecosystem response scenarios for sustained commercial activities in the future. In the present study, the spatial patterns and diversity of phytoplankton communities were analyzed along with upper ocean biogeochemistry, in the licensed China Ocean Mineral Resources R&D Association (COMRA) contract area and the surrounding western CCZ between August 21 and October 8, 2017. Results indicated this was a typical low-nutrient low-chlorophyll a (Chl a) environment, characterized by low levels of phytoplankton abundance and diversity. In total 112 species belonging to 4 phyla were recorded (>10 μm), with species counts including 82 diatoms, 27 dinoflagellates, 1 cyanobacteria and 2 chrysophyte. Dominant taxa in successive order of descending abundance and occurrence included Nizschia marina, Cyclotella stylorum, Dactyliosolen mediterraneus, Rhizosolenia setigera, Pseudo-nitzschia delicatissima, Thalassiothrix frauenfeldii, Synedra sp., Chaetoceros simplex and Pseudo-nitzschia circumpora. The depth-averaged abundance and Chl a concentrations were (265±233) cells/L and (0.27±0.30) μg/L, respectively. Diatoms accounted for 90.94% of the community with (241±223) cells/L, while dinoflagellates accounted for 5.67% and (15±13) cells/L. The distribution pattern exhibited the same trend as abundance, Chl a and species richness, showing subsurface maximum levels at around 100 m, with stations near 10°N having higher levels than in the north. Cluster analysis was performed in two assemblages, relating to geographic locations to the south and north of 12°N. The subsurface maximum of abundance, Chl a, species richness, dissolved oxygen and nitrite were generally corresponding to the presence of high salinity North Pacific Central Water at depths of 50−120 m. Higher availability of nitrate, phosphate and silicic acid in the subsurface may account for the shift in phytoplankton distribution, as shown by redundancy correspondence and spearman correlation analysis. Diel variation in an anchor station demonstrated prominent species succession without significant differences in oceanographic variables, among which diatoms succession resulted from the light limitation, while dinoflagellate diel variation mainly related to lateral transport of water masses. The observed patchiness in spatial phytoplankton distributional patterns was attributed to upper ocean environmental gradients in the CCZ. The baseline generated in this study could be analyzed using current conservation strategy programs associated with deep-sea mining.

Hypoxia is increasingly reported off the Changjiang River Estuary with the confluence of multiple high volume nutrient sources. The Regional Ocean Modeling System coupled with a biological model was used to analyze the effect of different nutrient sources on the development of hypoxia off the Changjiang River Estuary. By comparing to observed data, our model suitably captured the regional dynamics of chlorophyll a, dissolved oxygen, and nutrient concentration. A series of sensitivity experiments were conducted to investigate the hypoxia response to the various nutrient sources, such as loading from the Changjiang River, Kuroshio and Taiwan Warm Current. Our model results indicated that nutrients from different sources significantly influenced the hypoxia off the Changjiang River Estuary, and it was mostly affected by nutrients sourced from the Kuroshio. The nutrients input from the Changjiang River had larger impacts on the hypoxia in the north of 30°N than that in the south of 30°N. The nutrients sourced from the Taiwan Strait had a least influence on the hypoxia off the Changjiang River Estuary.

The English Channel (the Channel) represents a major sink and transport pathway of anthropogenic radioactive ¹²⁹I. Despite this important role, data concerning the distribution of ¹²⁹I in seawater of the Channel are scarce, and most of existing data are restricted to the eastern part of the Channel. The advection and dispersion of ¹²⁹I from the French coast toward the central and further the English coast, especially in the Channel west of Cap de La Hague, are not fully investigated. We present results of iodine isotopes (¹²⁷I and ¹²⁹I) analyses of surface water samples collected along the central English Channel in October, 2010. The data show high ¹²⁹I concentrations between Dover Strait and La Hague, followed by a dramatic drop towards the Celtic Sea and reveal the dispersal of ¹²⁹I towards central and northern part of the Channel. Our observation also implies that the entire British coast is contaminated by ¹²⁹I. ¹²⁹I levels in the westernmost English Channel, close to the English coast, may reflect combined influences from La Hague and Sellafield. Evolution of ¹²⁹I between 2005 and 2010 suggests a strong link to temporal marine discharges from La Hague plant. The discharges from the nuclear reprocessing facility have continued since 2010 and thus an ecological evaluation of ¹²⁹I radioactive hazards in the environment of the Channel may be needed.