Marine environmental research最新文献

This study analyzed the relationship between the oxygen minimum zone (OMZ) and various types of carbon, such as POC, DOC, and DIC, in the Y3 seamount area in the Western Pacific. The results indicated that the OMZ was located at 200-1000 m and a threshold of 100 μmol/kg was established for this area of the Western Pacific. The DOC and POC changed drastically out of OMZ while they were relatively stable within the OMZ due to the low oxygen. The rates of decrease in DOC and POC within the OMZ were significantly lower than those above the OMZ, indicating that the organic matter (OM) degradation rate within the OMZ was much lower than that above the OMZ. DIC maintained a continuously increasing trend with depth, but the DIC growth rate above, within, and below the OMZ decreased gradually. The controlling factors for the various types of carbon were different. POC was closely related to the decomposition of OM. The presence of recalcitrant organic carbon in DOC weakened the relationship between DOC and OM decomposition, and DIC components were complex and related to biological activity, temperature, and carbonate manifestation. This study explored the distribution of various types of carbon in the Western Pacific, providing support for studying the marine carbon cycle under a low-oxygen background.

The Bohai Sea (BS) is a semi-enclosed inland sea and China's most polluted coastal sea. With the rapid economic development of the circum-Bohai Sea region, large amounts of pollutants have been discharged into the BS, posing a significant threat to human health and the ecosystem. Great efforts have been made on investigating the levels of various pollutants in the BS; however, the priority pollutants which are required for the implementation of suitable environmental management and remediation measures in this system remain unclear. By using the risk quotient method, this study evaluated the ecological risks of various pollutants (including antibiotics, heavy metals, total petroleum hydrocarbons (TPHs), endocrine disruptors, pesticides, and persistent organic pollutants) in BS water and sediments over the past twelve years to identify the priority pollutants in this system. The results showed that 8 and 10 pollutants were at risk in BS water and sediments, respectively. Overall, 13 pollutants (arsenic (As), copper (Cu), mercury (Hg), nickel (Ni), chromium (Cr), lead (Pb), zinc (Zn), cadmium (Cd), TPHs, bisphenol A (BPA), erythromycin, polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs)) in the BS were identified to have potential risks and should be included in the list of priority pollutants. The monitoring of the changes in the contents of these pollutants in BS water and sediments needs to be strengthened in the future.

The ongoing decline in seawater pH, driven by the absorption of excess atmospheric CO₂, represents a major environmental issue. This reduction in pH can interact with metal pollution, resulting in complex effects on marine phytoplankton. In this study, we examined the combined impacts of seawater acidification and copper (Cu) exposure on the marine diatom Phaeodactylum tricornutum. Our data indicate that elevated pCO₂ had a minor effect on the growth and photochemistry and overall performance of P. tricornutum. However, seawater acidification significantly influenced cell size, surface roughness, and adhesion. Higher pCO₂ levels led to increased Cu accumulation in P. tricornutum under low ambient Cu concentrations, while significantly reducing Cu accumulation. The smaller cell size and reduced negative charge on the cell surface may explain the decreased Cu accumulation and toxicity. In response to metal stress, P. tricornutum upregulated Cu efflux to mitigate the increased Cu stress in acidified seawater. The expression of the metal transporter gene CTR1 and the reductase gene FRE1 were significantly downregulated, while ATPase5-1B was upregulated in cells exposed to elevated Cu concentrations at 1200 μatm pCO₂. Our study provides useful insights into the interactions between metals and diatoms in an increasingly acidified ocean.

Recovering seagrass ecosystems through restoration has become impellent to re-establish their functionality and services. Although the use of seedlings may represent an appropriate solution, little information is provided on the seedling-based restoration effectiveness with influence of biotic and abiotic interactions. Survival, morphological development and leaf total phenol content of transplanted Posidonia oceanica seedlings were evaluated under different origin, thermal regimes and herbivore pressure through a five-months field experiment in two MPAs, located on the west (cold) and east (warm) Sardinia coast to explore the effectiveness of seedling-based restoration. Seedlings originated from the two coasts responded differently to thermal regime site and herbivory pressure, as the warm-adapted ones survived less but developed more (and vice-versa) and resisted to the herbivory pressure increasing their phenol content, thus showing compensating responses. This study provided information on the P. oceanica seedling-based restoration by investigating abiotic and biotic interactions with the transplanted plants. It promotes the collection of beach-cast fruits from different coasts and their transplantation, regardless their origin, with no need of protecting seedlings from predators.

Extreme events influence ecosystem dynamics, but their effects on coastal marine habitats are often poorly perceived compared to their terrestrial counterparts. The detailed study of changes in benthic communities related to these phenomena is becoming urgent, due to the increasing intensity and frequency of hurricanes recorded in recent decades. Slow-growing benthic sessile organisms are particularly vulnerable to mechanical impacts, especially the large long-lived species with branched morphology that structure Mediterranean coralligenous assemblages. The present study evaluates the effects of the severe storm occurred in October 2018, and classified as one of most violent that ever struck north-western Mediterranean coasts, on two gorgonian species, the scleralcyonacean Corallium rubrum (with a solid carbonate axial skeleton) and the malacalcyonacean Paramuricea clavata (with a flexible proteinaceous axis). Comparing the cover and density of the two species before and after the severe storm, C. rubrum showed a decrease of more than 50% in one surveyed site. In contrast, P. clavata population did not show a decrease, and exhibited the highest density and cover in the same site, thanks to the high hydrodynamic condition which are favourable for this species. In this study, cover evaluation proved to be more time-efficient than counting colonies, and reduced the risk of errors. The present example highlighted the importance of continuous monitoring, including the assessment of the biological and ecological traits of the species, to provide a complete picture of their populations for conservation planning.

Windstorm patterns associated with beach strandings of the commercially important Tehuelche scallop, Aequipecten tehuelchus, in San José Gulf, Patagonia, were analyzed to understand the windstorms recurrence given their potential impact on the dynamics of the resource. Although the phenomenon of scallop strandings has been recognized for a long time, the lack of environmental records has made it difficult to thoroughly study the meteorological conditions that trigger these events. The availability of reanalysis data has the potential to address this data gap; however, its feasibility must first be validated. To address this, the first step was to characterize and compare hourly wind intensity (m/s) and direction (degrees) data from the fifth-generation global climate reanalysis (ERA5), provided by the European Centre for Medium-Range Weather Forecasts, with in situ wind data for the 2013-2020 period. The study focused on wind conditions during reported Tehuelche scallop strandings along the northern coast of the gulf. Subsequently, a historical search for southerly windstorms with characteristics similar to those responsible for past strandings was conducted using the ERA5 database, covering the period from 1950 to 2023. Overall, ERA5 accurately captured the dates, durations, intensities, and directions of southerly windstorms at high temporal resolution (hourly), though with a slight tendency to underestimate wind intensities of higher winds. The estimated mean annual frequency of ERA5-detected southerly windstorms with intensities higher than 11 m/s was 5.4 storms per year, with durations ranging from 12 to 74 h. These windstorms can occur throughout the year, with an increased frequency and duration during winter. ERA5 proved to be a valuable tool for characterizing windstorms, complementing in situ data and providing insight into past stranding events where no observational data were available.

The oil spill is a significant source of marine pollution, causing severe harm to marine ecosystems. Detecting oil spills accurately using synthetic aperture radar (SAR) images is crucial for protecting the environment. However, oil spill targets in SAR images are small and resemble other objects "look-alike". Traditional semantic segmentation networks for MOSD may lose critical information during downsampling Hence, we propose a shape-aware and adaptive strip self-attention guided progressive network (SAGPNet) for MOSD. Firstly, we adopted the progressive strategy to reduce detailed information loss. Second, we improved the traditional U-Net by redesigning its encoder unit. Specifically, we proposed a shape-aware and multi-scale feature extraction module and an adaptive strip self-attention module (ASSAM). These modifications allow the model to extract shape, multi-scale, and global information during the encoding process, addressing the challenges posed by small targets and "look-alike". Third, we utilize the ASSAM to extract global features from the final encoding layer of the earlier stage of the progressive network to guide the encoding features of the subsequent stage, aiming to recognize the overall shape of the oil spill and ensure that the model preserves crucial contextual information, further mitigate the information loss caused by downsampling. Finally, we designed a joint loss to address pixel imbalance between oil spills and other targets. We use three public oil spill detection datasets to evaluate the performance of SAGPNet. The experimental results show superior performance compared to other state-of-the-art methods, highlighting the effectiveness of SAGPNet in addressing the challenges associated with MOSD.

It is of interest to explore the capabilities of the diffusive gradients in thin-films (DGT) as a substitute for smart biomonitoring of metals in aquaculture waters. DGT deployment and transplantation experiments of scallops Argopecten irradians were carried out in the coastal aquaculture waters. The results showed that DGT-labile metal concentrations were relatively stable in the aquaculture and they were in descending order: Zn > Ni > Cu > Pb ≈ Cd. The scallop A. irradians exhibited different abilities of taking up the studied metals from the ambient aquatic environment. Importantly, it demonstrated that DGT responded quicker than biomonitoring of scallops. Overall, it suggested DGT technique as a rapid monitoring method for metal contamination in aquaculture waters and laid a foundation for the standardization of the DGT technique. Besides, it suggested that high organic matter may have a great influence on DGT-labile concentrations, which should be investigated in more detail.