Journal of Sea Research最新文献

Pinna nobilis Linnaeus, 1758 is a Mediterranean endemic bivalve critically endangered due to a severe epidemic caused mainly by the parasite Haplosporidium pinnae. Presently, live populations in Spanish waters are restricted to the Ebro Delta (Catalonia) and the Mar Menor (Murcia). The coastal lagoon of the Mar Menor has faced several eutrophication crises since 2016, which pose a threat to the survival of P. nobilis. Since 2016, >95% of the specimens of this species have died due to recurrent episodes of eutrophication in the lagoon. An analysis of the mortality within the relict population of P. nobilis in the Mar Menor lagoon after the last population survey in 2019 has been carried out, together with a characterisation of some microscale factors that describe its current habitat in the lagoon. For this purpose, three sampling localities were selected along the east coast of the lagoon, where a study of both live and dead individuals was conducted. Additionally, a characterisation of the macrophyte beds and the sediment conditions surrounding these individuals was carried out, comparing the sediment near the recently dead and live individuals. All studied localities exhibit similar mixed macrophyte beds of Cymodocea nodosa (Ucria) Asch., 1870 and Caulerpa prolifera (Forsskål) J.V. Lamouroux, 1809. At the location where significantly less C. nodosa cover was observed, the mortality of P. nobilis individuals was higher, and the sediment near the dead individuals was also more disturbed (with a more negative Eh and higher percentage of organic matter). These results contribute to a better understanding of the dynamics of microscale factors following P. nobilis mortality events, facilitating the identification of potential survival areas.

Under the effect of global climate change, the enhanced wave condition leads to lateral erosion at the mangrove vegetation edge, threatening the survival of mangrove habitat and the safety of coastal defense. By means of investigations on soil physicochemical properties and wave flume experiments, we quantify the lateral erosion rates of mangrove soils under waves and bridge the edge stability and vegetation with soil properties. It is found that different mangrove species and stand ages significantly alter the physiochemical properties of soils, and consequently affect the erosion resistance. Lateral erosion rate is positively correlated with organic matter content and negatively correlated with saturated density, which serve as two main factors that affect soil resistance to wave forcing. Experimental datasets suggest that the soil lateral erosion rate of Kandelia obovata reaches several times larger than that of Sonneratia apetala among different stand ages, indicating that the erosion resistance has significant differences between mangrove species. Among different Sonneratia apetala sites, the erosion resistance is enhanced with increasing mangrove stand age. This study sheds light on the feedbacks between geo-morphodynamics and intertidal vegetation, which provides a promising experimental approach to evaluate the ecological functions of mangrove forests with respect of resistance to external disturbance. Insights gained from this study is useful in guiding the nature-based solutions for coastal defense through proper spatial-temporal configuration of suitable saplings with higher potential in resilience.

Global Sea Surface Temperature (SST) trends have garnered significant attention in several ocean-related domains, including global warming, marine biodiversity, and environmental protection. This involves having an accurate and efficient forecast of future SST to ensure early detection and response in time to these events. Deep learning algorithms have become popular in SST prediction recently, although directly obtaining optimal prediction results from historical observation data is not simple. In this paper, we propose STA-SST, a new deep learning approach for forecasting SST, by combining the temporal dependencies of SST using the Bidirectional Long Short-Term Memory (BiLSTM) model, spatial features extracted from the convolution layer, and relevant information from the attention mechanism. To assess how well the Attention-BiLSTM with convolution layer predicts SST, we conducted a case study in the Moroccan Sea, concentrating on five different areas. The proposed model was compared against alternative forecasting models, including LSTM, XGBoost, Support Vector Regression (SVR), and Random Forest (RF). The experimental results show that STA-STT produces noticeably the best prediction results and is a solid choice for field implementation.

The sound speed profile (SSP) is an important factor affecting the acoustic propagation characteristics of the ocean, making the accurate acquisition of SSP a crucial step in the interdisciplinary research of oceanography and underwater acoustics. Limited by the cost of in-situ measurement and the performance of the instrument itself, direct measurement of SSP inevitably leads to insufficient depth or even missing information. In this paper, we propose using partial underwater prior information (UWPI) only including underwater sound speed to obtain preliminary reconstruction results of global SSP for the first time. The empirical orthogonal function (EOF) reconstruction algorithm is optimized by employing assimilated SSP as the background SSP to further reduce reconstruction errors. The maximum global average reconstruction error and root mean square error (RMSE) after optimization decrease by >51% and 71%, respectively, which indicates that the performance of the optimized algorithm combined with partial UWPI is further improved. Finally, the performance of the optimized algorithm is discussed from the perspective of acoustic propagation. This research provides a reliable technical approach for SSP reconstruction under incomplete depth conditions, which can be applied in underwater sound field prediction and acoustic detection in the future.

In order to further analyze the impact of the marine environment factors in the Northwest Pacific Ocean on the distribution of chub mackerel Scomber japonicus resources, a spatio-temporal weighted regression model was constructed based on the marine environmental and fishery data of China's light purse seine production in the high seas of the Northwest Pacific Ocean. Six environmental factors, including sea surface temperature (SST), chlorophyll a concentration (Chl-a), eddy kinetic energy (EKE), SST gradient intensity (GSST), longitudinal SST gradient (xGSST) and latitudinal SST gradient (yGSST) in spring, summer and autumn were used to analyze the impact of the temporal and spatial environmental factors on chub mackerel. The results show that the statistically significant variables (p < 0.05) were different in seasonal models. The SST, Chl-a, yGSST and EKE were statistically significant in the spring model, SST, yGSST and GSST in the summer model, and EKE, yGSST and GSST in the autumn model. The adjusted coefficients of determination (R²_adj.) of the spring, summer and autumn models were 0.488, 0.378 and 0.475, respectively. The results suggest that the coefficients of various environmental factors changed not only with time, but also with geographical location. Through this study, we can provide methodological reference for the study of resource change and fishery formation mechanism of chub mackerel fishery in the Northwest Pacific Ocean.

Dissolved oxygen (DO) is one of the core parameters in ocean investigation among various disciplines. The Winkler method, a classical approach, is extensively employed for DO determination. This method uses the reaction of Mn²⁺ to I₃^‐− as a proxy to quantitatively convert DO to iodine, followed by titration with sodium thiosulfate solution. However, this method is time-consuming and laborious due to the shaking and/or re-shaking of the DO bottle after adding the pickling reagents and waiting for the precipitate to settle. In this study, we implemented a stirring operation using a glass-coated magnetic stir bar at 1000 rpm for 1 min to replace the traditional static settling. The precision of DO measurements obtained via manual titration (coefficient of variation, CV < 0.2%) was comparable to that of the traditional method. Conversely, a polytetrafluoroethylene (PTFE) coated magnetic stir bar was unsuitable due to the release of pre-adsorbed oxygen. Comparative experiments conducted during an Indian Ocean cruise demonstrated that the DO measurements obtained using the improved method were in good agreement with those obtained using the traditional method. The coefficient of determination (R²) from the linear regression of the two methods was 0.999, and the ratio of the results averaged 1.00 ± 0.02. Our study also revealed that the combined effect of Mg²⁺, Ca²⁺, OH⁻, and HCO₃⁻ increases the settling time after the addition of pickling reagents. Overall, this modification represents a useful and labor-saving advancement in the determination of a classic oceanographic parameter, with potential for widespread adoption by scientists and technicians.

Besides the much-needed reduction of CO₂ emissions, exploring and implementing carbon removal strategies is essential to reduce the impact of man-made climate change effects. The sequestration of CO₂ by coastal vegetated ecosystems (CVEs) presents a natural and nature-based solution. One of these CVEs is kelp forests, which are amongst the most productive and diverse marine ecosystems. Although their CO₂ sequestration potential is still being discussed, kelp forests have been increasingly mentioned within the blue carbon framework in recent years. As kelp forests worldwide are in decline, it is not sufficient to conserve these habitats, but expanding the existing and even establishing new sites is essential. As a baseline study for potential kelp forest expansion around the island of Heligoland and even afforestation measures in the German Bight, we investigated the light requirements of the brown alga Laminaria hyperborea and the in situ light climate. Our results point to a compensation irradiance of 30 μmol m⁻² s⁻¹ and a local depth limit of 12.8 m for L. hyperborea under summer conditions. Consequently, we calculated the total area with suitable light conditions for kelp growth around Heligoland to be about 24.1 km². Combining the kelps minimum light requirement, underwater light attenuation, and bathymetric maps, provides an understanding of habitat requirements based on the physiological needs of L. hyperborea and helps to identify suitable afforestation sites within the German Bight.

From March to June 2020, governments across the world imposed lockdowns in an attempt to reduce the transmission of COVID-19 during the early phase of the pandemic. This period of time in which human activity slowed worldwide has been coined the “Anthropause”. The goal of this study was to determine if sunscreen pollution abated during the Anthropause and to identify the severity of the pollution when tourism/recreation recovered at two coastal units of the U.S. National Park System: Kaloko-Honokōhau National Historical Park in Hawaiʻi, U.S.A. and Cape Lookout National Seashore in North Carolina, U.S.A. Active ingredients of sunscreen products were measured in water and sand samples at both locations, including oxybenzone, octinoxate, octocrylene, octisalate, homosalate, and relevant breakdown products of some of these ingredients. A risk assessment was conducted on Anthropause and post-Anthropause contaminant levels for both locations to determine if there was a threat reduction during the Anthropause, and whether tourism recovery in the post-Anthropause period served as a threat to coastal wildlife. Both national park units exhibited an almost absolute reduction in the levels of sunscreen contamination during the Anthropause period, a striking commonality considering the geographic expanse separating the parks. Once travel restrictions were lifted, a large influx of tourists ensued at both locations, resulting in a relatively sudden and dangerous increase in the levels of sunscreen chemical pollution. This study supports the argument that unmanaged tourism is a source of coastal sunscreen pollution that poses a threat to the localized continuity of species populations and biodiversity, especially to coral reefs and fisheries.

The hexactinellid sponge Asconema setubalense Kent, 1870 is a deep-sea species characterized by its expansive cup-shaped morphology, which contributes significantly to the three-dimensional complexity of the marine ecosystems. This sponge forms grounds that offer protection to pelagic organisms and juvenile stages. Despite its ecological relevance, there is a lack of information on the ecology, behavior and population structure of this species. The research aimed to conduct a multitemporal analysis of this sponge in the Aviles Canyon System over a ten-year period, focusing on spatial distribution and abundance. Changes in fishing pressure were estimated using the presence of fishing gears as a proxy. Additionally, the study sought to provide a detailed morphometric description through 3D photogrammetric reconstructions based on the latest data. The multi-temporal analysis revealed a subtle increase in sponge density, particularly at depths ranging from 320 to 390 m, exhibiting an irregular spatial distribution in 2022, with maximal values of 0.08 individuals/m². Despite a small decrease on the loss of fishing gears in the overlapping area between samplings in 2012 and 2022, there was not a clear indication of a decline in fishing pressure over the years. Notably, more sightings of fishing gears were found in transect IC222TV_16 (0.07 gears/m²) than in IC222_TV02 (0.04 gears/m²) in 2022, suggesting potential spatial preferences for fishing activities. Visual analysis of temporal populations revealed an increase of 7% in specimen perturbations over ten years, with the population in IC222_TV16 being healthier (9% of the individuals presenting severe deformations) than in IC222_TV02 (40%). High-density fishing gear locations coincided with areas inhabited by sponges displaying the highest perturbation levels in both transects. Morphometric analysis using data from 2022 indicated a prevalence of individuals with heights concentrated between 0.18 and 0.38 m, osculum and flounce diameters reaching 0.4 and 0.56 m and osculum and flounce surfaces of 0.02–0.04 and 0.06–0.19 m² respectively. Over 80% of measured specimens exhibited a high degree of asymmetry. Strong correlations were observed between heights and osculum and flounce surfaces, but external factors may be included for explaining wall deformities. These findings contribute valuable insights into the characterization of A. setubalense, serving as a foundation for future research in the area. Moreover, this work highlights the promising potential of photogrammetry as an efficient tool for monitoring of vulnerable marine ecosystems (VME) and marine protected areas.

Dispersal, a critical factor in the viability of marine organisms, is strongly influenced by the physical dynamics of the ocean. Fronts, as a common phenomenon in ocean dynamics, can theoretically impact the dispersal of organisms and ultimately cause spatial homogeneity or heterogeneity of marine communities. However, there is relatively limited understanding concerning whether frontal formation hinders the connectivity between communities and thus results in differences in community structure. To verify whether the formation of fronts caused differences between communities, 60 eDNA samples and their environmental parameters were collected from 32 sites in the Yangtze River estuary and its adjacent area, and four groups, the Yangtze River front-inner group (YRI), the Yangtze River front-outer group (YRO), the Zhejiang costa front-inner group (ZCI), and the Zhejiang coast front-outer group (ZCO), were compared to examine the differences in fish communities between the sides of the front. The results showed that there was a significant difference between YRI and YRO, suggesting that the front affected the community structure. There was no significant difference in fish communities between ZCI and ZCO, indicating that fronts could only hinder dispersal at high intensities. The difference between YRI and YRO possibly resulted from dramatic changes in temperature, salinity, and turbidity related to the front. Fronts also separated water masses with different environmental characteristics and thereby attracted fish to their optimal habitats. Overall, fronts appear to be ecologically significant for fish dispersal and community differentiation.