Marine Service Research Articles

Baltic sea ice thickness estimation based on X-band SAR data and background information

Abstract In this study an operational sea ice thickness (SIT) estimation algorithm, based on HH-polarized X-band synthetic aperture radar (SAR) data, background information from the most recent, typically from the previous day, available daily Baltic Sea ice chart and the operational Finnish Meteorological Institute (FMI) thermodynamic ice model, was developed and evaluated. The algorithm was designed to complement the C-band SAR SIT algorithm developed earlier at FMI and applied daily as part of the operational Copernicus Marine Service (CMS). The X-band SIT algorithm was developed by utilizing the sea ice thickness measurements made onboard the Finnish and Swedish ice breakers during two winters seasons: 2021–2022 and 2022–2023. The former season measurements were used for defining the algorithm parameters and the later season for evaluation of the algorithm performance. According to the evaluation metrics the X-band algorithm performance is slightly better than that of the operational CMS C-band SAR SIT algorithm, indicating its suitability for operational use in CMS.

Assessing the representation of Arctic sea ice and the marginal ice zone in ocean–sea ice reanalyses

Abstract. The recent development of data-assimilating reanalyses of the global ocean and sea ice enables a better understanding of the polar region dynamics and provides gridded descriptions of sea ice variables without temporal and spatial gaps. Here, we study the spatiotemporal variability of the Arctic sea ice area and thickness using the Global ocean Reanalysis Ensemble Product (GREP) produced and disseminated by the Copernicus Marine Service (CMS). GREP is compared and validated against the state-of-the-art regional reanalyses PIOMAS and TOPAZ, as well as observational datasets of sea ice concentration and thickness for the period 1993–2020. Our analysis presents pan-Arctic metrics but also emphasizes the different responses of ice classes, the marginal ice zone (MIZ), and pack ice to climate changes. This aspect is of primary importance since the MIZ accounts for an increasing percentage of the summer sea ice as a consequence of the Arctic warming and sea ice extent retreat, among other processes. Our results show that GREP provides reliable estimates of present-day and recent-past Arctic sea ice states and that the seasonal to interannual variability and linear trends in the MIZ area are properly reproduced, with the ensemble spread often being as broad as the uncertainty of the observational dataset. The analysis is complemented by an assessment of the average MIZ latitude and its northward migration in recent years, a further indicator of the Arctic sea ice decline. There is substantial agreement between GREP and reference datasets in the summer. Overall, GREP is an adequate tool for gaining an improved understanding of the Arctic sea ice, also in light of the expected warming and the Arctic transition to ice-free summers.

Autonomous data sampling for high-resolution spatiotemporal fish biomass estimates

Many key ecological dynamics such as biomass distributions are only detectable on a fine spatiotemporal scale. Autonomous data collection with Unmanned Surface Vehicles (USV) creates new possibilities for cost efficient and high-resolution aquatic data sampling. However, the spatial coverage and sampling resolution remain uncertain due to the novelty of the technology. Further, there is no established method for analysing such fine-scale autocorrelated data without aggregation, potentially compromising data resolution. We here used a USV with an echosounder, a conductivity-temperature sensor and a flourometer to collect data from April–July 2019–2023 in a 60x80km area in the central Baltic Sea. The USV covered a total distance of 8000 nmi, over 42–81 days per year, with an average speed of 0.5 m/s. We combined the hydroacoustic data with publicly available oceanographic data from Copernicus Marine Service Information (CMSI) to describe seasonal distribution dynamics of a small pelagic fish community. Key oceanographic variables collected by the USV were correlated with CMSI estimates at daily/monthly resolution, respectively, to test for suitability to scale (Temperature 0.99/0.97; Salinity −0.77/−0.26; Chlorophyll-a 0.12/0.28). We investigated two approaches of Species Distribution Models (SDMs): generalized additive models (GAM) versus spatiotemporal generalized linear mixed effect models (GLMM). The GLMMs explained the observed data better than the GAMs (R2 0.31 and 0.20, respectively). The addition of environmental variables increased the explanatory capability of GAM and GLMM by 25 % and ~ 3 %, respectively. Due to the high data resolution, we found significant amounts of positive autocorrelation (R: 0.05–0.30) across more than 50 lags of observation. However, we found that diel patterns in fish detection strongly affected the abundance estimates due to diel vertically migrating species hiding in the ‘acoustic dead zone’ near the seabed. Such dynamics could only be estimated and corrected for in predictions on the high-resolution data, complicating the trade-off between autocorrelation and high-resolution for SDMs even further. We compared estimates and effect sizes/directions in identical SDMs on 2x2km/month aggregated (i.e non-autocorrelated) observations and non-aggregated (i.e. autocorrelated) observations, and found relatively little difference in spatiotemporal estimates (r = 0.80). For the first time, we predicted the distribution of a small pelagic fish community at a high spatial resolution, in an area essential to breeding top predators, opening up for new applications in ecological studies locally and globally.

Surface Modification of Composite Coating for Marine Application: A Short Review

Corrosion is one of the phenomena that affects the deterioration of materials in offshore applications. Marine corrosion is particularly aggressive, due to the high salt content and low electrical resistivity of seawater. Corrosion cannot be stopped completely, but the reaction can be slowed down. Applying coating is an effective and widely used method to protect metal surfaces from corrosion. Coatings act as a barrier between the metal and its environment, preventing or slowing down the corrosive processes. Pursuant to ISO 12944, the most commonly used generics for coating systems in marine service are alkyd, acrylic, ethyl silicate, epoxy, vinyl ester, polyurethane, polyaspartic, and polysiloxane. The latest innovations in marine coatings still use a layer-by-layer coating method (e.g. primer coats, intermediate coats, and top coats) depending on thickness. Marine structures exposed to the atmospheric zones are usually coated with one or two coats of epoxy. A slightly more costly system of one coat of zinc-rich primer, one coat of epoxy, and one coat of aliphatic polyurethane may provide better performance. Coating systems for the atmospheric zones are frequently used in the intertidal and splash zones. Immersion zones of marine structures are commonly coated with one or two coats of 100% solid epoxy or three coats of solvent-borne epoxy. A single polymer as a generic coating have limitations. Adding fillers is a common method to improve the properties of polymers to become a composite. In marine coatings, fillers are still limited to glass flakes and powder. Poor dispersion and agglomeration might reduce the effectiveness of fillers in the matrix, which decreases the adhesion properties. The fillers must be surface modification before the application. This review provides a comprehensive and critical review of the current research status of composite coatings that serve as candidates to be used in marine coating.

Oceanographic preconditions for planning seawater heat pumps in the Baltic Sea – an example from the Tallinn Bay, Gulf of Finland

Abstract. The use of low-temperature seawater heat for renewable energy installations is demonstrated with an example from the Tallinn Bay, Baltic Sea, based on Copernicus Marine Service reanalysis data. Tallinn and its surrounding seaside counties are home to about half a million people and produce about half of Estonia's gross domestic product (GDP). The Tallinn Bay with an area of 223 km2 extends to the north and has an open connection to the Gulf of Finland. Depths more than 50 m that cover the halocline already appear at a distance of 3–4 km from the coast. Surface layers get too cold during winter to be used in heat pumps for district heating; therefore, a feasible option is to pump slightly warmer seawater from the deeper halocline layers. The lowest monthly mean halocline temperature – down to 2.6 °C at 50 m depth and 3.3 °C at 70 m – is found in March and April based on reanalysis data from 1993–2019. The seawater seasonally cools below 3 °C on average on 1 January at 20 m depth and on 12 February at 50 m depth. At the 70 m depth, the average start of T<3 °C was calculated on 28 February, although only 14 winters out of 26 had such water present; in 12 winters the condition T>3 °C was always fulfilled. The median number of cold days is 11, with a maximum of 128 d in the winter 1993/1994 when stratification became rather weak due to the prolonged absence of Major Baltic Inflows of saltier and warmer North Sea waters. During the recent warmer period of 2009–2019, the start of the cold seawater period was delayed on average by 5–10 d. Tallinn has, among other Baltic Sea cities and industrial sites, a favorable location for seawater heat extraction because of the short distance to the unfreezing sub-halocline layers. Still, episodically there are colder-water events with T<3 °C, when seawater heat extraction has to be complemented by other sources of heating energy.

Using artificial intelligence algorithms in the investigation of mixed layer depth seasonal changes in the Barents Sea

The study aims at discovering features of seasonal changes in the mixed layer depth (MLD) of the Barents Sea in 1993–2020.Charts of the distribution of the MLD in the Barents Sea in 1993–2020 provided by the Copernicus Marine Service were used as the material of the study.Methods of the study: cluster analysis, machine learning, neuronal networks, the nearest neighbor method (kNN).Results. Classification of the data sets of the MLD distribution according to their seasonal features was carried out based on the modelling using AI algorithms and machine learning. It was concluded that winter is specified by two classes (increased/decreased values of the layer thickness). The third class includes spring and autumn when distributions of the MLD are close to one another, and the fourth class comprises summer (June-September) when the MLD grows very slowly.Practical relevance. The results will contribute to a better understanding of the hydrophysical processes of the Barents Sea and can further be used as series of independent variables to study the Barents Sea ecosystem and to estimate a stock and a catch forecast of commercial aquatic organisms.

Oceanographic conditions of spring migration of European anchovy as a factor of formation of its spawning stock in the Sea of Azov

The aim of the work is to determine the influence of sea water circulation and temperature on the formation of the spawning stock of anchovy in the Sea of Azov.Materials and methods: Fishery and biological data on the spawning stock of the Azov anchovy were collected in surveys and bioresources monitoring carried out by the Azov-Black Sea branch of the VNIRO («AzNIIRKH») in 2000–2021. Satellite sea level data were used in the analysis of sea water circulation. These data, as well as satellite information on sea surface temperature for March-June 2000–2021 for the north-eastern part of the Black Sea and the southern part of the Azov Sea were taken from the website of the Copernicus Marine Service information system. Graphical and statistical methods of analyzing multi-year changes in the data were used in the work. The novelty of the performed work lies in the study of oceanographic conditions of spring migration of anchovy to the Sea of Azov as factors determining the size of its spawning stock in this sea.Result: intensive growth of the spawning stock of anchovy in the Sea of Azov was observed in 2008, 2010 and 2011. This was facilitated by: predominance of north-western geostrophic currents in the north-eastern part of the Black Sea in April 2008–2011, weakening of the Azov currents in the Kerch Strait in April 2007–2010 and predominance of the Black Sea currents in May 2004–2012, Decrease in the meridional gradient of water temperature in the Kerch Strait in April 2007–2010.Practical significance: the possibility of using oceanographic information for April-May to predict the size of the spawning and commercial stock of anchovy in the Sea of Azov.

Coastal water quality dynamics of the Red Sea, southeast coast of Egypt using GeoAI and ChatGPT

The Red Sea coastal environment of Halayeb and Shalateen area is renowned for its abundant marine flora and fauna. It also holds significant economic and cultural importance for local communities. However, this region is currently confronted with various challenges, including climate change and habitat destruction. To effectively address and mitigate these issues, advanced technologies that offer a holistic understanding of the area's environmental conditions are required. This paper applies the integration of Geospatial Artificial Intelligence (GeoAI) and ChatGPT to study the Red Sea Coastal water quality dynamics of Halayeb and Shalateen Area. Landsat imagery and Copernicus Marine Service were used to retrieve area boundaries and monitor the physicochemical characteristics of the coastal water respectively. ChatGPT was utilized to generate Python code that facilitates the creation of optimal distribution maps for each physical and chemical property criterion. The Python codes were incorporated into the Python program within the ArcGIS 10.7.1 and executed to generate the desired maps representing the dynamics of physical and chemical properties. It was found an observed fluctuation in chemical properties next to the coastline around the mouth of two main wadies; Wadi Hudain, and Wadi Da'eb. The degree of stability increased away from the coast toward the deep water. That proved the effect of the runoff on the seawater, as the runoff plays an essential role in the water state, especially in such semi-closed water bodies like the Red Sea where the flashfloods are the main source that can enrich water with sediment and nutrients. The state of seawater in terms of physical properties was not characterized by a specific pattern. The distribution of physical parameters in the Red Sea is influenced by factors such as regional climate variations, monsoonal winds, and local topography. This paper serves as a stepping stone for future research endeavors, exploring the full potential of this integrated approach. It can be concluded that the fusion of GeoAI and ChatGPT technologies has the potential to revolutionize our approach to studying and managing the coastal environment.

Flexural behavior of coral aggregate concrete beams reinforced with BFRP bars under seawater corrosion environments

The combined utilization of fiber-reinforced polymer (FRP) composites with coral aggregate concrete (CAC) in remote island areas contributes to the reduced construction cost and construction period, offering a promising application. However, the evolution pattern and deterioration mechanism of flexural behavior for FRP bars reinforced CAC beams in marine service environments remains unclear. Thus, this paper investigates the flexural behavior of basalt-FRP (BFRP) bars reinforced CAC beams under seawater immersion and dry-wet cycle conditions using laboratory-accelerated aging methods. The research considers the effects of exposure temperature and corrosion age on their failure modes, flexural stiffness, ultimate loading capacity, and deformation deflection. The experimental results revealed that with the increase in corrosion age and exposure temperature, the amount of vertical cracks of CAC beams decreased and their crack depth also exhibited a slight reduction, but their crack width and spacing at failure significantly increased. After being attacked by seawater environments, the load-deflection curves of CAC beams experienced an enhanced slope of the ascending section (i.e., flexural stiffness), but this strengthened flexural stiffness did not result in an enhancement in the ultimate load capacity. Instead, with prolonged corrosion and higher temperatures, the ultimate load of CAC beams displayed significant degradation, accompanied by reduced mid-span deflection. After 12 months of seawater exposure to wet-dry cycle conditions at 60 °C, the ultimate load and mid-span deflection of CAC beams degraded by approximately 25.0 % and 56.6 %, respectively. The study also predicted the flexural bearing capacity of CAC beams utilizing existing specifications for FRP-reinforced normal aggregate concrete (NAC). It was concluded that the formulae for flexural loading capacity for FRP-reinforced NAC beams were still suitable for CAC beams.

FAIR ADCP data with OSADCP: a workflow to process ocean current data from vessel-mounted ADCPs

This paper presents the open-source Python software OSADCP developed for the processing of vessel-mounted Acoustic Doppler Current Profiler (VMADCP) data. At this stage, the toolbox is designed for processing VMADCP measurements from open-ocean applications of Teledyne RDI Ocean Surveyor ADCPs and the data acquisition software VMDAS. Based on the VMDAS ENX binary output format, the software contains implementations for cleaning and vector-averaging of single-ping velocity data, verification of the position data, and applying misalignment and amplitude corrections. The procedures of OSADCP are described in detail to encourage the scientific community to use it for their own purposes. The toolbox is an integral part of a workflow implemented on the German marine research vessels in the framework of the Underway Research Data project of the German Marine Research Alliance (DAM). It aims to ensure standardized data acquisition measures, reliable data transfer from the ADCP to shore both near-real-time and in delayed-mode, processing and quality control, and dissemination of the curated data product in the data repository PANGAEA. From PANGAEA, data sets are forwarded to the European marine data hubs Copernicus Marine Service and EMODnet. The workflow that forms the framework for OSADCP is described here as an example of scientific data management that follows the FAIR data guidelines.

A climatological overview of surface currents in the Arabian Gulf with special reference to the Exclusive Economic Zone of Qatar

AbstractThis study derives the climatology of surface currents in the Arabian Gulf using the current velocities obtained from the Copernicus Marine Service (CMEMS) for the period 1993–2019. It reveals distinct temporal and spatial variability in the surface current speeds induced by the variability in surface winds, bathymetry and the changes in the lateral gradients in density. The mean speed of the Iranian Coastal Current (ICC) during summer reaches up to 0.33 m·s−1 along the coast of Iran, while the mean speed of Arabian Coastal Current (ACC) reaches up to 0.26 m·s−1 along the coast of Saudi Arabia. We found the occurrence of 2 major and 1 minor cyclonic eddies in the annual, seasonal and monthly climatology, while these eddies are more prevalent during summer. The major cyclonic eddy in the central Gulf develops in May and persists till November with varying patterns, and decays in December. The climatological mean current speeds are higher during summer compared to winter, due to the seasonal changes in thickness of the surface layer by the stratification/destratification processes. The highest mean current speeds along the coast of Qatar are found in June and the lowest in winter months. The highest annual, monthly and seasonal mean current speeds are observed along the north and northeast coast of Qatar, while the lowest are observed along the west coast and southeast coast of Qatar. Interannual variability in surface current speeds is evident, with notable links with the El Niño–Southern Oscillations (ENSO) and Indian Ocean Dipole (IOD). The annual mean current speeds show positive trends, of the order of 0.06–0.14 cm·s−1·year−1 in the offshore regions and 0.05–0.24 cm·s−1·year−1 in the nearshore regions, wherein the highest positive trend is observed off Ras Laffan and the lowest off Dukhan.

Penentuan Kelayakan Pemberian Bantuan BBM pada Nelayan menggunakan Metode Vikor

Fishermen is a term for people whose daily work is catching fish or other biota that live on the bottom or surface of the water. Fishermen can also discuss and share experiences in overcoming problems in the fisheries and marine sector to meet the needs of fishermen. The government of the Fisheries and Marine Service is required to support the need for subsidized fuel for fishermen. The increase in fuel oil (BBM) has an impact on the operational costs of fishermen, because BBM is one of the main components in the daily activities of fishermen, with the high price of BBM, fishermen will face an increase in operational costs that they must spend to carry out fishing activities. This can reduce the income earned by fishermen, because higher costs will affect the profits that fishermen get from the sale of fish. So the Fisheries and Marine Service of Langkat Regency Provides Assistance for Fishermen in Langkat Regency, from the many assistance that have been distributed in this thesis I took a sample of the Fishermen of Secanggang Village. Based on the research conducted, the results obtained were that the first alternative that was a priority to receive subsidized fuel assistance for fishermen in Langkat Regency with a Q value = 0 and was entitled to be recommended. And the next priority was the second alternative with a Q value = 0.492.

Understanding environmental drivers and trends in chlorophyll-a and related factors across equatorial Indian Ocean regions: implications for marine ecosystem dynamics and vulnerability

ABSTRACT We estimated the concentration of Chlorophyll-a (Chl-a) along with physical and biological factors including sea surface temperature (SST), wind speed and concentration of nitrate and phosphate in the Western, Central and Eastern Equatorial Indian Oceans (WEIO, CEIO and EEIO) using data from the Copernicus Marine Service and ERA-5 for the years 1994 to 2019. Our results show that along with the concentration of Chl-a, nitrate and phosphate have decreased, and sea surface temperature has increased in the EEIO. Due to coastal upwelling off the coast of Somalia and offshore Ekman transport throughout the summer, the southwest monsoon caused a significant increase in concentrations of Chl-a, nitrate, phosphate and wind speed in WEIO during June-July-August-September (JJAS) and October-November-December (OND). SST decreased at this time and deeper water interacted with surface water, increasing biological production. In EEIO, the upwelling zone is primarily maintained by wind-induced divergence throughout the year, whereas stratification in winter prevented surface Chl-a increase. High wind speed and low SST led to increased productivity in WEIO. Comparison of EEIO with WEIO and CEIO demonstrates low levels of Chl-a, phosphate and nitrate. The trends signify that these oceanic zones are highly vulnerable to developing into ecological deserts in the near future.

Reconstruction of Baltic Gridded Sea Levels from Tide Gauge and Altimetry Observations Using Spatiotemporal Statistics from Reanalysis

A method for reconstructing weekly Baltic gridded sea levels was developed and tested. This method uses input data from tide gauge and altimetry observations. The reconstruction is based on sea level empirical orthogonal function (EOF) modes, calculated as spatiotemporal statistics from daily model reanalysis results available from the Copernicus Marine Service for the 1993–2021 period. In the semi-enclosed, tideless Baltic Sea, the four leading EOF modes cover 99% of the sea level variance. Several experiments with different combinations of input data were carried out. This method was validated against coastal tide gauges and altimetry data. The best reconstruction was obtained when both the tide gauges and altimetry data were used as inputs. An assessment of the centered root-mean-square difference (cRMSD) of the reconstruction versus the tide gauges revealed a value of 0.05 m, and a result of 0.10 m was revealed versus altimetry. The average coefficient of determination (R2) was determined to be 0.93 for the tide gauges and 0.82 for the altimetry data. In the cases where only one type of input data was used, the reconstruction worsened with respect to other data sources. The reconstruction method demonstrated its usefulness for the reconstruction of coastal sea levels in unsampled locations and the calculation of changes in sea volume.

Projections of the Adriatic wave conditions under climate changes

Assessing the impact of climate change on wave conditions, including average and extreme waves, is vital for numerous marine-related activities, industries, coastal vulnerability, and marine habitats. Previous research, primarily on a large scale, has investigated this topic, but its relevance for marginal basins like the Adriatic Sea is limited due to the low resolution of the wave models used and atmospheric forcing. To contribute to filling in the gap, here we implemented a high-resolution model (about 2 km) for the period 1992–2050. The future wave climate is simulated for the RCP8.5 emission scenario. This model, developed within the AdriaClim project, comprises, among others, a high-resolution atmospheric downscaling, a circulation Limited Area Model and a spectral wave model. A comparison of our simulation's results with Copernicus Marine Service wave reanalysis on the historical baseline, confirms its accuracy in reproducing both average wave parameters and 95th percentile values, as well as the seasonal cycle, showing the AdriaClim model's suitability as a source to predict future wave climates in the Adriatic Sea. The projected changes suggest a slight increase in average significant wave height and mean wave period, and a more significant decrease at the 95th percentile, with a relevant variability by location and season, partially aligning with previous studies. This study highlights the potential effect of local climate change in coastal areas and the importance of developing long-term simulation with a downscaled modeling system for regional areas.

Conformity of the Work Plan with the Budget Implementation Document at the Marine and Fisheries Service of Central Lombok Regency

The writing of this article is aimed at finding out the suitability of the work plan with the Budget Implementation Document at the Marine and Fisheries Service of Central Lombok Regency by using descriptive qualitative. The results and discussion can be seen from the Details of the DPA Expenditure Activities of the Central Lombok Marine and Fisheries Service has reflected the conformity with the performance of the service which can be seen in the Central Lombok Regent Regulation No. 83 of 2016 concerning the Position, Organizational Structure, Main Tasks and Functions of the Central Lombok Regency Marine and Fisheries Service. As for activities and expenditures that are samples are Expenditure on Fishing Management activities in Rivers, Lakes, Reservoirs, Swamps, and Other Reservoirs that can be Pursued in 1 (one) Regency/City Region with official travel expenses, Small Fishermen Empowerment Activities in the Regency/City Region with competition prize spending, and Small Fish Cultivation Empowerment Activities with fish health and environmental management training expenses.

Experimental Study on Durability and Bond Properties of GFRP Resin Bolts.

Glass fiber-reinforced polymer (GFRP) anchor bolts are a new type of high-performance nonmetallic anchor with significantly higher tensile strength, a lighter weight, better corrosion resistance, and a lower cost than steel bars. Therefore, exploring the durability and bonding performance of GFRP anchor systems is of great importance for the structural design of protective engineering, especially in coastal environments. However, insufficient research has been conducted on the durability of GFRP resin bolts in seawater conditions, with no universal standard on the pullout testing of GFRP bolts. To study the durability and bonding performance of GFRP resin bolts, durability experiments were conducted in this work using artificial seawater, and the pullout tests were conducted using a large-scale concrete platform with different compressive strengths (21.2, 40.8, and 61.3 MPa). The results of the durability experiments indicated that the strength variations of the GFRP rods and epoxy resin materials in artificial seawater environments were less than 5%. Subsequently, indoor pullout tests using steel tubes filled with epoxy resin were conducted, and the test results indicated a critical anchor length value. Pullout tests of the GFRP resin bolts embedded in large-scale concrete blocks were also conducted with different strengths. According to the test results, all GFRP resin bolts embedded in the three concrete blocks with different compressive strengths exhibited rod fracture failure. The failure mode was not controlled via the compressive strength of the concrete blocks due to the high bonding strength between the resin and the rod, as well as between the resin and the concrete. Therefore, this GFRP resin anchor system could fully utilize the tensile strength of GFRP rods. This research offers significant practical value in verifying the safety and reliability of GFRP resin bolts in corrosive marine service environments, and it contributes to the application and development of GFRP materials in the engineering field, serving as a valuable reference for the structural design and further study of GFRP bolts.

Modeling hydrogen diffusion in precipitation hardened nickel-based alloy 718 by microstructural modeling

Abstract Environmentally assisted cracking can significantly affect the performance of high strength alloys and limit material selection to minimize the risk of subcritical crack growth in service. UNS N07718 is widely used in marine service applications and under a variety of conditions, such as: alternate immersion, different levels of cathodic protection, and freely corroding galvanic couples, because of its demonstrated corrosion and fracture resistance in these environments. In this work we developed a representative model of the material microstructure including the metal grains, the material texture, and the precipitates along the grain boundaries and within the grains. The microstructural model was subjected to the boundary conditions identified at the notch root of a fracture mechanics sample and the results are used as input for a simulation of hydrogen diffusion from the surface of the notch, assuming the material has been introduced to a hydrogen producing environment. The diffusion of hydrogen was modeled by Fick’s law and included both hydrostatic stress and mobile dislocation velocity as driving forces. The influence of immobile dislocations was also modeled to account for the irreversible trapping. The results show that hydrostatic stress and immobile dislocation trapping can significantly alter the highest concentration of hydrogen and its location within the microstructure towards the fracture process zone. Mobile dislocation velocity has a small influence in determining the hydrogen distribution near the fracture process zone.

Policy and governance of maritime resources in the Riau Islands Province

ABSTRACT This research refers to the policies carried out and the existing management in Riau Islands Province. The implementation process in managing the maritime sector must refer to Law Number 23 of 2014 which regulates Regional Government. The purpose of this research also explains what steps must be taken in resolving problems in managing natural resources that occur. This research method uses qualitative methods with qualitative analysis, the data analysis process is used purposively, namely by consideration. The results showed that the policy carried out by the Riau Islands Provincial Government through the Marine and Fisheries Service, was found to have no definite authority regarding the process of managing maritime resources in Riau Islands Province, besides there was an overlap of authority, especially for its state civil servants, who had training related to capacity building and how to manage marine resources. The conclusion in this research is to respond to the applicable law, namely Number 23 of 2014, which clearly gives heavy authority to the water area. Thus, the management that occurs is less than optimal.

Preserving the Lake Toba ecosystem: Strategic planning to mitigate red devil fish invasion

Lake Toba is known as a tourism destination and also has aquaculture that is utilized for freshwater fish. However, several types of endemic fish and consumable fish cultivated in Lake Toba are facing the threat of extinction, and their populations are decreasing due to the presence of Red Devil Fish. The research aims to explain how the local government’s strategic planning efforts mitigate the invasion of Red Devil Fish and preserve the ecosystem in Lake Toba. This research uses qualitative research with descriptive methods. This research prioritizes secondary data collection that can support research. Data analysis techniques include data reduction, data display, and conclusion. The results showed that the Indonesian government must overcome the problem of red devil fish invasion into the Indonesian aquatic ecosystem. The presence of Red Devil fish in Lake Toba has reduced the number and diversity of fish, including the extinction of several native fish species. The impact of this invasion damages the ecosystem and causes economic losses such as control costs and decreased fish production for public consumption. The local government’s strategic planning in protecting the Lake Toba ecosystem from Red Devil fish invasion is carried out by controlling spatial planning, conducting talks, and collaborating with various related parties. The North Sumatra Provincial Marine and Fisheries Service and the Fish Family Association have implemented strategies to minimize Lake Toba’s Red Devil fish population. Increasing community involvement in managing the Lake Toba ecosystem and reducing the Red Devil fish population is crucial.