Oceanologia最新文献

Due to the rising environmental awareness, emissions and releases of pollutants, including metals, have been considerably reduced in the last decades. Therefore, the remobilization of natural and anthropogenic contaminants is gaining importance in their biogeochemical cycle. In the marine coastal zone, this process occurs during the erosion of a shore, especially the most vulnerable cliffs. The research was conducted in the Gulf of Gdańsk (southern Baltic Sea) from 2016 to 2017. The sediment cores were collected from four cliffs; additionally, marine surface sediments were also taken. The concentrations of essential (Cr, Mn, Fr, Cu, Zn) and nonessential (Rb, Sr, Y, Zr, Ba) metals were analyzed using the XRF technique. The levels of the analyzed metals were relatively low, typical of nonpolluted areas. However, considering the mass of eroded sediments, the annual load of metals introduced into the sea in this way is significant. In the case of Cu, Zn, and Y the load can amount to a few kilograms, for Cr and Rb – over ten kilograms, for Mn, Sr, and Zr – several tens of kilograms, for toxic Ba – over 100 kg, and in the case of Fe – 4.8 tonnes. During strong winds and storms, when the upper part of a cliff is eroded, especially the load of Zn and Cr entering the sea may increase. The content of Cr, Zr, and Ba in the cliffs was higher compared to marine sediments from the deep accumulation bottom, which indicates that coastal erosion may be an important source of these metals.

Satellite sensors are used to monitor water on a large scale. One of the key variables defining the water-leaving signal is suspended particulate matter (SPM) and thus it is important to understand its properties to improve remote sensing algorithms. However, only a few studies investigating the variability of SPM properties (concentration, nature and size) under different seasonal, weather and geographical conditions have been carried out in the Baltic Sea. We focused on relatively shallow areas (maximum depth of 10 m) where there is strong sediment transport by rivers and resuspension of the particles by wave action and advection by currents. Eleven field campaigns were conducted using a set of instruments measuring inherent optical properties, auxiliary data, and, in Pärnu Bay, also particle size distributions. The results showed that the SPM concentrations, particulate absorption, mass-specific particulate scattering, and backscattering varied temporally and spatially from 5.5–19.6 g m⁻³, 0–5.62 m⁻¹, 0.08–1.45 m² g⁻¹, and 0.0009–0.25 m² g⁻¹, respectively. The spectral backscattering ratio, which in general is considered to be constant in bio-optical remote sensing algorithms, was actually wavelength-dependent and varied between 0.005 and 0.09 depending on the origin of the particles (organic or mineral matter), particle size distribution, weather conditions, and location. In situ particle size measurements in coastal waters of Pärnu Bay also showed that resuspended fine clay particles agglomerated into flocs of >30 µm in the brackish waters of the Baltic Sea having random shapes and different sizes.

The Bay of Bengal (BoB) is known to have high primary productivity at its western margin during the Indian summer monsoon season (June–September). This higher coastal productivity is mainly caused due to the near-surface nutrient availability maintained by the local coastal upwelling process. The surface winds in the Indian Ocean significantly vary during El-Niño/La-Niña and Indian Ocean dipole (IOD). The current study examines the sea surface temperature (SST) and Chlorophyll-a (Chl-a) anomalies in the western BoB for the period of 18 years (2000 to 2017), using a coupled regional ocean biophysical model. All considered positive IOD (pIOD) years show discrete behavior of biophysical features in the western BoB. The co-occurrence years of pIOD and El-Niño modes are associated with contrast biophysical anomalies. In the analyzed pIOD events, the years 2006 and 2012 show an enhancement in the Chl-a anomalies whereas, the other two years (2015 and 2017) experience Chl-a decrement. The western BoB was anomalously warmer during the 2015 and 2017 pIOD years compared to the other two pIOD years (2006, 2012). This inconsistent response of biophysical features associated with pIOD years is investigated in terms of local surface flux (momentum, heat, and freshwater) changes over the western BoB. The combined impact of local surface flux changes during the individual years remains the major contributing factor affecting the upper-ocean stratification. Ultimately, the stratification changes are responsible for the observed inconsistent response of biophysical features by significantly altering the upper-ocean mixing, upwelling, and nutrient availability in the western BoB.

Atlantic cod (Gadus morhua) is an important commercial fish species on the world market. The aim of our studies was to explore the presence, intensity of infection and distribution of the zoonotic nematodes of the different genera of Anisakidae in the muscle tissue of G. morhua from the Norwegian Sea. Cod from fishing areas FAO IIa1 (n = 50) and FAO IIa2 (n = 56) were sampled in March 2017. The unskinned flesh of each fish was examined using a white-light transilluminator. Collected parasites were identified to the genus level, and a subsample was identified using molecular methods. We found a higher prevalence of infection with Anisakis than with Pseudoterranova in the musculature of cod from both fishing areas. In FAO IIa1, a lower prevalence of infection with Pseudoterranova was recorded (14%) than in FAO IIa2 (∼39%). However, the intensity of infection was higher (53) in FAO IIa2 than in FAO IIa1 (8 parasites per fish). The opposite was found with Anisakis (prevalence 88% in FAO IIa1 and ∼55% in FAO IIa2, intensity up to 30 and up to 25 parasites per fish respectively). Most Anisakis larvae were present in the belly flaps (predominantly the left side), while Pseudoterranova spp. were dispersed with descending frequency in belly flaps, dorsal fillet and caudal fillet. Molecular identification revealed the presence of A. simplex (s.s.), P. decipiens (s.s.) and P. krabbei in both areas, and a hybrid of P. decipiens and P. krabbei in FAO IIa2.

The Svalbard Archipelago has experienced some of the most severe temperature increases in the Arctic in the last three decades. This temperature rise has accelerated sea-ice melting along the coast of the archipelago, thus bringing changes to the local environment. In view of the importance of the near-future distribution of land-fast sea ice along the Svalbard coast, the available observation data on the ice extent between 1973 and 2018 are used herein to create a random forest (RF) model for predicting the daily ice extent and its spatial distribution according to the cumulative number of freezing and thawing degree days and the duration of the ice season. Two RF models are constructed by using either regression or classification algorithms. The regression model makes it possible to estimate the extent of land-fast ice with a root mean square error (RMSE) of 800 km², while the classification model creates a cluster of submodels in order to forecast the spatial distribution of land-fast ice with less than 10% error. The models also enable the reconstruction of the past ice extent, and the prediction of the near-future extent, from standard meteorological data, and can even analyze the real-time spatial variability of land-fast ice. On average, the minimum two-monthly extent of land-fast sea ice along the Svalbard coast was about 12,000 km² between 1973 and 2000. In 2005–2019, however, the ice extent declined to about 6,000 km². A further increase in mean winter air temperatures by two degrees, which is forecast in 10 to 20 years, will result in a minimum two-monthly land-fast ice extent of about 1,500 km², thus indicating a trend of declining land-fast ice extent in this area.

Coastline retreat poses a threat to nearshore environment and the assessment of erosion phenomena is required to plan the coastal engineering works. The hydro-morphodynamic response of a beach to natural and artificial forcing factors differ considerably, as the nearshore processes are especially complex and depended on a multitude of parameters, including prevailing wave and hydrodynamic conditions, beach topography, sediment characteristics and the presence of coastal protection works. The present study serves the purpose of numerically evaluating nearshore morphological processes and ultimately assessing the capacity of coastal defence structures to control beach erosion. For this reason, a new sediment transport model including unsteady effects and swash zone morphodynamics, was coupled to the highly nonlinear Boussinesq wave model FUNWAVE-TVD, providing integrated predictions of bed level evolution, across various timescales of interest. The compound model was validated thoroughly against laboratory data and other numerical investigations. Overall, a good agreement between experimental and numerical results was achieved for a number of test cases, investigating the effects of different types of shore protection structures. The proposed integrated model can be a valuable tool for engineers and scientists desiring to obtain accurate bed level predictions, over complex mildly and steeply sloping sea bottoms composed of non-cohesive sediment particles.

The dilution method is typically applied to estimate the growth and mortality rates of phytoplankton, but it is also used to study bacterioplankton. The method comprises creating a gradient of dilutions to reduce the encounter rates between bacterivores and bacteria, thus allowing for estimations of bacterial growth and grazing pressure exerted on the bacteria. However, the manipulations involved in the method can lead to biased results. In this study, 12 dilution experiments performed in the coastal zone of the Baltic Sea were accompanied by additional measurements capable of detecting possible artefacts. Only six measurements performed during spring and summer (March–August) produced results that were free of artefacts and were statistically significant. During fall and winter (October–February) measurements were unsuccessful because of food limitation of bacterial growth during experimental incubation. Twice (in September and October) bacterial growth and grazing mortality rates were underestimated because grazing pressure was not successfully removed. The study demonstrated that 24-hour and five-day oxygen consumption measurements incorporated into dilution experiments permitted estimating the fraction of biodegradable organic matter used during incubation, and, thus, detecting the food limitation of bacterial growth.

The role of reeds in the functioning of ecosystems and their significance for zoobenthos in the coastal lagoons is poorly understood. We hypothesise that next to the spatial zonal differentiation of abiotic factors in the apparently homogeneous habitat of reeds, benthic macroinvertebrate fauna is also unevenly distributed, and differs in taxonomic and functional diversity, as well as density and biomass across the reed stand. The research was carried out in the Vistula Lagoon (southern Baltic) along three designated sectors arranged parallel to the shoreline and differing in distance from the shore and depth. Mean density of reed stems in the analysed stand was within the range of values reported from different American and European wetlands. Regardless of the location within the reeds and the season, the fauna was dominated by detritivorous Tubificinae and larvae of Chironomidae. The highest diversity, density, and biomass of fauna were found in the middle littoral zone, and the lowest in the outer zone adjacent to the open water. The presented data support our hypothesis predicting the existence of a spatial variation pattern in the composition and distribution of macroinvertebrates in response to the changing zonal habitat conditions within the reed stand.

This study aimed to investigate the capability of the one-dimensional (1D) mode of the Simulating WAves till SHore (SWASH), as a non-hydrostatic wave-flow model with six vertical layers, to reproduce the cross-shore wave evolution. For this purpose, the given model was initially calibrated for wave energy and the outputs were then verified with the field data measured at the Southern Caspian Sea. The calibration coefficients obtained for wave breaking are significantly less than the ones which have been mostly reported in previous studies for the two-dimensional (2D) mode of the SWASH. Although the reproduced wave height parameters are generally in good accordance with the field observations, the period parameters and the number of waves are overestimated and underestimated by the model, respectively. Moreover, the inaccuracies at the shallow stations are worse than at the transitional depths. The overestimation in both the reproduced energy of infragravity waves (IG) and their wavelength along with the underestimation in the wind-wave energy content are also among the factors responsible for the model deficiencies. The findings have revealed that the overestimation of the reproduced IG waves is the main reason for the underestimation of the breaking dissipation rate for irregular wave trains in the 1D mode. Therefore, more intensive breaking dissipation via selecting lower coefficient values is necessary to exhaust a certain energy content from longer waves in the 1D mode. This approach ultimately induces an over-dissipation of short wind-waves.

Three thousand forty-one profiles of temperature, salinity, density, dissolved oxygen, nitrogen and chlorophyll-a were used to study their seasonal variation on a tropical coral reef system, located in the central part, of the reef corridor of the southwestern Gulf of Mexico. The results revealed three seasons according to their hydrographic variations; the northerly wind season from September to April; the dry season from May to June; and the rainy season from July to August. The results of the density ratio during the dry season were ∼1.25 on average, while during the rainy season it had an average value of ∼0.62. Thus, the pycnocline was more influenced by the halocline during the rainy season and by the thermocline during the dry season. There was also an evident variation in chlorophyll-a concentration over the water column, which was not evident in the surface layer. During the summer (rainy season), dissolved oxygen was related to chlorophyll-a concentration; while, during the winter (northern wind season), these values were related to the vertical mixing of the water column due to wind stress. There was evidence of cooler ocean water intrusion into the Veracruz Reef System during the spring-summer season below ∼10 m. Finally, a second halocline, pycnocline, and nitrocline were found near ∼30 m depth during the rainy season.