Accuracy Assessment of Satellite Derived Bathymetry Model for Depth Extraction in Sorong Shallow Water Area

Marine research has continuously improved the methods in obtaining the related bathymetric data; not only relying on the conventional methods for i.e. echosounder-based methods, but also by incorporating satellite technology for i.e. passive remote sensing technology, in this case, satellite derived bathymetry (SDB). Regarding the SDB method, as we know, variation of sea bed cover can influence the relation between the spectral reflection of shallow water area and the depth of the sea. In this situation, normalization of the sea bed variation is needed. Previous studies have mentioned that the band ratio can help to normalize the variation of sea bed cover. This research is intended to compare the accuracy of satellite derived bathymetry by using single band and band ratio. Four bands of Sentinel 2A (blue, green, red, and NIR bands) are used along with a single beam echosounder (SBES) measurement data published in 2015 used as training and testing data for the SDB model. Furthermore, the influence of sun glint correction to the results was evaluated and the accuracy of the model was estimated. In total there are four single bands and six combinations of band ratio that are used for this research. The results show that green band outperformed band ratio in term of RMSE value. However, visually, only band ratio of blue/green band that provided a much more representative depth spatial distribution especially for shallow water area below 3 m. In this case, band ratio is effective in normalizing the variation of sea bed cover. Furthermore, the use of sun glint correction in the process is also increase accuracies of the SDB model. The highest accuracy was obtained when using green band after sun glint correction with RMSE value 2.999 m while when using band ratio of the blue band to the green band (blue/green), the accuracy was 3.624 m. In conclusion, SDB model to extend methods in obtaining bathymetry data is promising as more images become available free of charge and in various resolutions.

Acoustic Presence of Dolphins through Whistles Detection in Mediterranean Shallow Waters

The evaluation of acoustic temporal rhythms in wide-ranging cetaceans can reveal patterns in animal spatial presence and the occurrence of periodical phenomena. Here, we aimed at assessing the temporal patterns of dolphin’s acoustic presence in a shallow-water area in the Sicily Strait (Mediterranean Sea). Whistles were collected continuously for 14 months from an acoustic monitoring station installed aboard of an elastic seamark. Over a total of 6955 h of recording, 14,048 signals were identified using both automatic and visual methods. Three parameters were analyzed: hourly presence (HP), used as a proxy of the presence of dolphins in the area; detection rate (DR), indicating the acoustic activity rate of dolphins measured per hour in the entire dataset; and detection rate in presence of dolphins (DRD), indicating the acoustic activity rate of dolphins considering only the hours when whistles were recorded. The highest values of both HP and DR were reached during the night, and the Autumn and Winter months, suggesting an increase in the dolphin’s occurrence and a possible moving away and towards the monitoring station potentially following prey. DRD, instead, showed an almost uniform distribution throughout the day implying that when the animals are close to the monitoring station, the acoustic activity does not show any pattern. However, possible changes in the communication exchange along the seasons were suggested. This study complements other work on this subject, improving the knowledge of dolphins’ acoustic activity in the area.

Design and implementation of underwater search for salvage robot power system

Most of the underwater salvage operations work in shallow waters. The underwater environment is complex and varied. There are many risks and unpredictable conditions such as turbulence, eddies, wind, waves and deep water pressure. The motion and control cause serious interference, and the flexibility of automatic stabilization and multi-dimensional motion under external disturbances is increasingly becoming a key element in the design process of underwater robots. In this paper, the structure, driving and control design of an underwater dynamic search and underwater robot based on 6-DOF driving is proposed, and its dynamics and control system are analyzed. Different from the traditional underwater robot technology, the method proposed in this paper is more suitable for shallow water area and multi DOF driving control technology. The driving structure and electronic device of the robot are introduced. Several experiments were carried out in the controlled environment. The experimental results demonstrate the correctness and effectiveness of the design and analysis.

Characteristics of Short-Period Internal Waves in the Avacha Bay Based on the In Situ and Satellite Observations in August-September, 2018

Purpose. The paper is aimed at evaluating the characteristics of short-period internal waves in different regions of the Avacha Bay in the Рacific Ocean concerning their hydrological and morphometric conditions. Methods and Results. The characteristics of internal waves are assessed through synthesizing the results of the in situ studies in the Avacha Bay in August-September, 2018, the high-resolution remote sensing data and the results of tidal modeling. The data of the in situ and satellite observations of internal waves were also directly compared. The results show that in the shallow part of the Avacha Bay, the waves, whose heights are from 10 to 15 m were observed. They constitute 10 % of the total number of cases. In the deep-water part of the bay, the internal waves are also often observed, but their maximum height does not exceed 10 m. The satellite images show 72 manifestations of short-period internal waves. Some of them spread to the coast with a tidal frequency from the generation source located around the 500 m isobath where the bottom abruptly slows down. Conclusions. The results of the investigation revealed a pronounced relationship between the wave trains recorded in the shallow-water area and the semidiurnal tidal dynamics. Analysis of the hydrological situation and the satellite images permitted to assume that the internal waves could be generated as a result of not only a barotropic tide collapse, but also due to the inertial oscillations of the frontal zone formed by the Kamchatka current meanders in the presence of a shallow sharpened pycnocline. Having been analyzed, the synchronous satellite and in situ observations made it possible to find out that the internal waves of the 5–8 m height were distinctly manifested on the sea surface in case the pycnocline depth was 10–20 m.

Aromatic hydrocarbons in components of geological environment of the Norwegian and Russian parts of coastal zone of the Barents Sea

<p>Information about hydrocarbons (HCs) distribution in components of geological environment (including aromatic (Ar) compounds) allows to estimate relative amounts of both natural and anthropogenic components and reveal sources of contamination. HCs are widely spread in lithosphere and create stable geochemical background. Variations in their composition attest to the specificity of initial organic matter, conditions of its accumulation and transformation.<br>The studied samples of soils and surface bottom sediments were collected during the research expedition in July, 2019 (supported by RFBR №18-54-20001 and NFR №280724). On the Norwegian coast of the Barents Sea the area of study included: salt marshes of Tana and Varanger fjords, littoral zone of rocky shores around Kiberg. In the Russian part of the Barents Sea samples were taken from the shallow water area of the Eastern coast of the Kola Bay. All samples were taken along the sublittoral – littoral – supralittoral transects appropriate for a detailed study of the organic matter (OM) spatial distribution. Study of the group composition of ArHCs in the extractable part of soil and sedimentary OM were performed using spectrofluorimetry.<br> The method is based on the ability of ArHCs to fluoresce under the influence of ultraviolet emitting in narrow spectral ranges determined by their molecular structure. This allows us to characterize the nature of ArHCs and determine possible sources of their input.<br>The spectrum characteristics of samples from intertidal zone of the Tana fjord salt marshes reflect the input of fresh unoxidized petroleum products such as diesel fuels and engine oils. The significant increase of ArHCs fluorescence intensity in surface sediments may testify to recent pollution accidents.<br>The spectrum traditionally associated with the estuarine-delta and lacustrine and swampy facies and characteristic for the post-sedimentation and early diagenetic stage of OM transformation was detected in samples from the salt marshes of Varanger fjord. <br>ArHCs of mixed origin (natural and anthropogenic) are identified in samples from the littoral zone of rocky shores of Kiberg. The spectral data of littoral sediments are typical for the polluted areas with high input of petroleum products. The specific maxima in the long wavelength region of spectrum that is characteristic for the high molecular weight aromatic compounds from the land plants is also detected in these samples. <br>Spectral characteristics of ArHCs of bottom sediments and soils collected from the shallow water area of the Russian part of the Barents Sea point to the presence of both low molecular weight benzene HCs (high volatile components of flammable liquids) and high molecular weight compounds (oil fuel, gas oil). The detailed study of these anthropogenic HC components seems to be very important given the fact of their detection in all littoral samples.<br>The further detailed study of the molecular markers and biomarkers (n-alkanes, isoprenoids, cyclanes, terpanes, PAHs) will increase our knowledge about HC sources, efficiency of their microbial and chemical degradation, allow to estimate human impacts on the environment of the region and draw up the regional “geochemical passport”.</p>

Modelling of Transformation Features for Nitrogen and Phosphorous Compounds in the conditions of the Novosibirsk Reservoir

The article presents a model description of spatially inhomogeneous features for the ecosystem of the Novosibirsk reservoir, the largest in Western Siberia, based on the reproduction of biogeochemical cycles of limiting elements. We have formulated the model tool set for studying quantitative and qualitative changes in the state variables of water bio/geo/cenosis. To obtain an adequate picture of environmental processes occurring in various parts of the reservoir modeling of the transformation features of nitrogen and phosphorus compounds in the waters of the Novosibirsk reservoir was performed in the box approximation. Phytoplankton biomass in a relatively shallow water area significantly exceeds concentrations in the deep-water and near-dam parts of the reservoir. A detailed dynamic picture of the variability of the content of pollutants, as well as oxygen, normalized by maximum permissible values, in the water areas of the reservoir is reproduced.The estimates obtained during the simulation generally correspond to the observed data. This study can serve as a basis for developing a model approach to monitoring and management of ecosystem processes in the Novosibirsk reservoir.