Journal of Sea Research最新文献

A novel method to accurately estimate phytoplankton abundance is proposed for an autonomous microscopic imaging system (AMIS) herein. To this end, a fast fluorescence detection module is developed and added to an imaging in-flow cytometer to record the fluorescence and side-scattered signals of individual phytoplankton particles, including of those that cannot be photographed by the AMIS. Image information and the coupling relationship between the fluorescence and side-scattered signals are used to accurately detect and estimate the phytoplankton counts in water samples. The performance of the proposed estimation method is evaluated on water samples containing Alexandrium tamarense, Chattonella marina, and Scrippsiella trochoidea. The abundance estimation accuracies for these species are found to be better than 95%, 97%, and 93%, respectively, when compared to results obtained using counting chambers. The performance of the method is further evaluated by mixing the collected data of the three phytoplankton species and classifying them based on fluorescence and side-scattered signals only, assuming that these species are included in the image data but not photographed individually. The overall estimation accuracy based on this complex matrix of the three species is found to be 95.3%. These results demonstrate the suitability and practicality of the proposed method for accurately evaluating phytoplankton abundance in water. The algorithm used in this study can be a reference for other imaging in-flow cytometers.

As an important part of the world economy today, the marine economy is of great significance for promoting economic growth and sustainable development. To better promote the development of marine economy, the Augmented Dickey-Fuller (ADF) unit root test was first used to test the stationarity of marine economy related variables to ensure the reliability of the model. Then, the Vector Error Correction Model (VECM) is used to analyze the long-term stable relationship and short-term dynamic adjustment relationship between the marine industrial structure rationalization and the marine economic growth. These results reveal the mechanism of the influence of the rationalization of marine industrial structure on the growth of marine economy. It is found that among the eastern coastal provinces and cities, the rationalization level of marine industrial structure in Shanghai is up to 0.163 points, which is higher than other cities. The main reasons are the low specialization index of marine labor force, the comprehensive utilization amount of industrial waste in 10,000 yuan of gross marine product, the low environmental protection index, and the large gap between the benefits of each index. In addition, the study also found that the Granger causality test values of the delayed combination of variables Gross Ocean Product (GOP), ts, GOP, and ts were 5.531, 14.672, and 15.069, respectively. Finally, it is found that the upgrading of marine industrial structure and the output of marine economy will correct the deviation of industry rationalization below the equilibrium value in the short term at a rate of 0.1675. According to the above results, the study puts forward the following suggestions. First, it needs to strengthen the planning and layout of the marine industry, rationally guide the allocation of resources and industrial development. Second, it needs to increase support for scientific and technological innovation, and promote technological progress and industrial upgrading. The third is to strengthen the government's policy support and supervision to provide a stable policy environment and market environment for industrial development. The innovation lies in the systematic study of the relationship between the rationalization of marine industrial structure and the growth of marine economy.

Brazilian corals are unique ecosystems with high endemism and low functional redundancy. Hence, mapping its geomorphology is an important step to inferring analyzes on benthic habitats. We observe several difficulties during this mapping of coastal areas by remote sensing and a lack of fine-scale depth data for reef areas in Brazil. The present study aims to present the bathymetry extracted by satellite imagery in murky waters using a mosaic of Sentinel-2 images in Google Earth Engine (GEE) calibrated with field samples. We used the satellite extracted DBM to map the bottom geomorphology through BTM (Benthic Terrain Modeler). We then present the first detailed geomorphological map for the largest marine coastal protected area in Brazil- MPA Costa dos Corais. The geomorphological raster was differentiated into seven classes: Flat Plains, Depressions, Gentle Slopes, Slopes, Terrestrial Reef Flat, Reef Flat, and Crest. Altogether, we estimate >275 km² of area representing reef structures (coral reef or beachrocks), or about 48% of the total MPA area. Mapping coral reefs can contribute to conservation, particularly in selecting areas for in situ monitoring activities and in prioritizing the application of remedial actions in the event of environmental disasters or threats to coral health, such as oil spills and bleaching episodes. Our findings encourage the applicability of these methodologies in other reef areas and collaborate for the management and monitoring of marine protected areas. In addition, all mapping is available online for any user.

Aquaculture and industrial activities have been recognized for their detrimental impact on coastal environment, particularly through large-scale mangrove conversion. This study employs interdisciplinary spatial, geochemical, and metagenomic approaches to examine the environmental legacy of past aquaculture and industrial activities in mangrove rehabilitation areas. The land use change of mangrove, aquaculture, and industrial area was investigated from 1990 to 2020. Mangrove coverage increased in the study area from 49.12 ha in year 1990 to 95.93 ha in 2020. This growth can be attributed to increasing environmental awareness related to issues such as tidal flooding, seawater intrusion, and coastal abrasion. However, despite increasing mangrove coverage, we still identified fecal bacteria communities in both sites, dominated by Campylobacteria, Gammaproteobacteria, and Deltaproteobacteria. Additionally, our functional prediction analysis revealed the presence of genes associated with pathogenicity, multidrug/antibiotic resistance, and xenobiotic degradation. We observed high nitrate concentration associated with aquaculture waste that was persistent in porewater even after the activity ended years ago. Low to moderate heavy metal concentration was found in the study sites, likely due to the role of mangroves as a biofilter. We conclude that mangrove restoration contributes to the lower environmental impact of anthropogenic activities on our sites. Therefore, it should be included in future coastal management plans to improve coastal water quality and ecosystem function in environmentally threatened areas.

Foraminifera assemblages are powerful bioindicators of environmental change and were analyzed in a sediment core collected from the Marquesas Keys, located in the southwestern region of the Florida Keys. The composition and abundance of foraminifera tests within the top 85 cm of the sediment core, dated with ¹⁴C and ²¹⁰Pb, revealed changes in foraminifera assemblages in 1990 CE, 1939 CE, and 1872 CE. Based on the ecological preferences of the dominant species, changes in salinity and submerged aquatic vegetation (SAV) cover may have influenced foraminifera species composition. These changes were likely caused by variation in precipitation patterns in the eastern Gulf of Mexico region associated with shifts in the major ocean-atmosphere teleconnections such as the El Niño Southern Oscillation (ENSO), Atlantic Multidecadal Oscillation (AMO), North Atlantic Oscillation (NAO) along with tropical storms and hurricanes. Prolonged periods of the negative phases of these climate phenomena coincided with shifts in foraminifera assemblages. Despite a generally negative impact of the ocean-atmosphere teleconnections on the South Florida region, a well-developed epiphytic assemblage was recorded in the studied core. The assemblage was recorded in the uppermost part of the core and dated to the period between 1990 and 2010 CE. This implies that a dense SAV community was present within the Marquesas Keys Mooney Harbor since at least the early 1990.

Marine communities are changing at an accelerated rate because of anthropogenic stressors such as global warming and overfishing. Community compositional change over time (temporal β diversity) is mainly driven by the replacement of species. The consequence of this change on community functioning is still unclear. In this study, we assessed the magnitude and direction of both taxonomic and functional compositional change in a demersal community subject to fishing and incipient sea warming over a recent 12-year period. We also evaluated the relative roles of turnover and nestedness components on both dimensions of temporal β diversity and identified which species are driving compositional change. Compositional data was collected during five surveys that took place between 2006 and 2018. We used linear mixed models to test for temporal change in species richness and taxonomic and functional dissimilarity and its components. While species richness remained constant, taxonomic and functional dissimilarity increased through time, with turnover contributing most to total dissimilarity in both cases. Taxonomic turnover of around 15% of species per decade produced a functional replacement of 13% per decade. The main functional change is probably due to the spatial expansion of three species of crustaceans which are bringing functional novelty to certain areas of the gulf. We found that local extinctions and colonization were balanced, which suggests that species richness is being regulated at the local scale within the gulf. We also found a balance in functional nestedness, which leads us to infer that this variable is also being regulated at the community level.

Hydrodynamic conditions in the Bohai Sea (BS) play an important role in regulating variabilities in the regional climate and marine ecosystem. In the current study, wintertime current variations in the BS were investigated using continuous in situ observations at two sites in the western BS (S1) and southeastern BS (S2) from November/December 2020 to March 2021. The results indicated that residual currents and their variations were both stronger at S1 than at S2. Residual currents had notable vertical variations, with nearly opposite directions in the upper and lower layers. Upper layer residual currents were mostly southeastward at both sites, while lower layer residual currents were basically west-northwestward at S2 following the topography in the deep trough in the South BS but were north-northwestward at S1 up the slope to the coast. Upper layer residual currents were strongly subsurface-intensified and experienced significant intraseasonal variations. Subsurface currents in the upper layer shifted from being weak in December 2020 to strong in January–February 2021, especially in the western BS. Surface currents were directly driven by surface winds following the Ekman layer dynamics in shallow waters. Weak/strong subsurface currents occurred during/after sustained strong sea surface winds, implying that they experienced more complex dynamics than surface currents. This study provides new understanding to the wintertime circulation pattern in the BS. It is helpful for fully understanding the characteristics and underlying dynamics of the BS circulation variations in winter and their impacts on biogeochemical processes.

Variations due to climate change like rising sea levels, recurring storm surges and changing wave conditions coupled with unsustainable development along the coast are exacerbating coastal populations' vulnerability to coastal dangers globally. The ecosystem based solution to achieve sustainable development is increasingly advocated in the last two decades to leverage nature's robust adaptive capacity to change and protect people against its negative consequences. Mangroves protect and maintain a rich marine biodiversity in the tropics and subtropics and are crucial carbon sinks. The present study thus analyses mangroves' role as ecosystem-based technique to reduce disaster risk and adapt to climate change using Mauritius, a small island state, as case study, particularly the coastal protective and climate change adaptive capacities of the two local species Rhizophora mucronata Lam. and Bruguiera gymnorrhiza (L.) Lam. The PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines were used to retrieve resources from Google Scholar, Web of Science and ScienceDirect for the 2002 to 2022 period. A total of 41,789 records were identified and through a robust screening and filtering process only 50 studies were deemed relevant to the present study. In this context, key attributes of mangrove forests were found to be in reducing coastal flood risk, sheltering coastal regions during storms and stabilizing the coast. This study lays the foundation to consider Rhizophora and Brugueira as robust nature based solutions for Mauritius which will be of key importance to decision makers, researchers and the public at large to consider restoring degraded mangrove sites and promote ecosystem-based approaches to reduce disaster risk, adapt to climate change, enhance marine spatial planning and better coastal zone management.

Carbohydrates, which form a large pool of carbon in plant litter, are a major driver of litter dynamics and benthic food webs in Spartina-invaded mangrove ecosystems. However, there are large gaps in knowledge regarding the effects of exotic leaf litter carbohydrates on benthic carbon assimilation. In this study, the dynamics of carbohydrates, including cellulose, lignin and monosaccharides (glucose, mannose, galactose, xylose and arabinose), during the leaf litter decomposition of the exotic Spartina alterniflora (SA) and the native mangrove plant Kandelia obovata (KO) were analyzed and compared. Meanwhile, the differences in the δ¹³C values of cellulose and lignin were used to analyze the utilization of leaf litter carbohydrates by polychaetes after Spartina invasion. Our results showed that the decomposition rate of exotic SA leaf litter was lower than that of KO leaf litter. The contents of cellulose, glucose and galactose in SA leaf litter were higher than those in KO leaf litter (P < 0.05). The decomposition rates of cellulose and monosaccharides (arabinose, xylose, mannose and galactose) in KO leaf litter were faster than those in SA leaf litter (P < 0.05). However, there was no significant difference in the decomposition rates of lignin in the leaf litter between exotic SA leaf litter and native KO leaf litter (P > 0.05). In the native KO plot, the carbohydrates of KO leaf litter contributed to >55% (cellulose, 26.91–28.02%; lignin, 28.05–28.64%) of the organic carbon sources of polychaetes. However, in the exotic SA plot, the carbohydrates of exotic SA leaf litter contributed to >65% (cellulose, 36.83–38.30%; lignin, 28.47–30.52%) of the organic carbon sources of polychaetes. The obtained results suggested that Spartina invasion increased the assimilation of cellulose by polychaetes. The high content and low decomposition rate of cellulose in the carbohydrates of exotic SA leaf litter might be important mechanisms for the carbon assimilation changes in the benthos of Spartina-invaded mangrove ecosystems. Given that Spartina has colonized in the Zhangjiang Estuary Mangrove Reserve, this study provides a theoretical basis for the recovery of benthos after ecological restoration. Furthermore, the mechanisms of carbohydrate assimilation by different benthos of different ecosystems should be comprehensively considered in the future.

Phytoplankton form the base of food chain and play a key role in maintaining the global climate system. However, very limited knowledge is available about the phytoplankton ecology of Bangladesh coast which is a representation of sub-tropical coastal ecosystem. Thus, this study aimed to understand the spatial and temporal variability of phytoplankton community in-relation to environmental variables in the South East coast of Bangladesh. Monthly data on essential oceanographic variables (i.e. temperature, salinity, dissolved oxygen, turbidity, silicate, nitrate and phosphate) and phytoplankton species abundance were collected from January 2022 to December 2022. We found a strong spatial and temporal variability in essential oceanographic variables and phytoplankton community compositions in Naf – Saint Martin Peninsula of Bangladesh. Estuarine ecosystem is characterized by high nutrients and low salinity while offshore ecosystem was found with comparatively low nutrients and high salinity. About 154 phytoplankton species were identified from the study area through year round sampling events. In the estuarine ecosystem Skeletonema marino, Coscinodiscus centralis, Coscinodiscus argus and Coscinodiscus traducens were found as the major contributing species at the estuarine ecosystem while Chaetoceros radican, Tripos trichoceros, Cylindrotheca Closterium, Chaetoceros convulutus, Tripos muelleri, and Cyclotella striata were found as the major contributing species at the offshore ecosystem. Our study found that 6 explanatory variables (i.e. temperature, salinity, turbidity, silicate, nitrate and phosphate) jointly explained about 78% variability in phytoplankton community dynamics. Nitrate concentration explained maximum variability (19%) followed by phosphate (17%), salinity (15%), silicate (12%), turbidity (10%) and surface temperature (5%). This study will play a key role in understanding the spatial and temporal variability of phytoplankton dynamics in the sub-tropical coastal ecosystem.