Gulf Of Finland Research Articles

Распределение уловов ипромысел шпрота ввосточной части Финского залива в 2019 году

The Baltic sprat Sprattus sprattus balticus is an important fishing species and takes the second place in abundance of the commercial catches after the Baltic herring in the eastern part of the Gulf of Finland. Before investigations of the sprat were rarely carried out in Leningradskaya region. Sprat is fished with the pelagic trawls as by-catch of the Baltic herring’s fishing clusters. The supply of the sprat forms in the western part of the Finnish Gulf and the Baltic Sea. This species goes to the eastern part of the gulf due to the forage migration. Materials for the research were the data obtained from the trawl fishery during the periods from January to May and from October to December 2017-2019 in Russian economic zone of the eastern part of the gulf close to the islands Bolshoy and Malyy Tyuters, Moshchnyy and Gogland. The analysis of the sprat distribution in 2019 was carried out based on the generalization of the results of trawl fishing. The review of the season fishing features in considered region is given. The amount of the catch of the species varied in the different fishing areas, changing significantly by months. The biggest catches reached 15-25 tons during 5 to 8 trawling hours were observed in November as well as in the former years. Largest number of the sprat was fished in the western border areas of the gulf which are adjacent to the Estonia and Finland waters.

Itämeren aleneva suolapitoisuus muokkaa Suomen rannikon lajien levinneisyyttä

The physical and chemical properties of water are vital for aquatic organisms. Should changes in these conditions occur, responses would follow both in the distributions of species and ecosystem functioning. Water salinity is particularly critical because it induces osmotic stress and requires specific physiological adaptations from the living organisms. Current climate change models suggest increasing precipitation in the Baltic Sea catchment area and decreasing seawater salinity along the Finnish seacoast. In order to envisage potential consequences of decreasing salinity in the coastal ecosystems, we apply alternative Baltic Sea salinity scenarios based on climate change and species inventory data with GIS modelling to estimate possible changes in the distributions of four aquatic species within the next 50 years. The results suggest that marine species are to lose much of their current distribution areas: blue mussel may constrain its distribution into the Archipelago- and Bothnian Sea areas only, while eelgrass will likely disappear completely. In contrast, the studied freshwater species, brackish water sponge and the common water mosses, will strongly expand their distributions along the Finnish seacoast. Their currently isolated populations in the Gulf of Finland and the Gulf of Bothnia will expand their populations as far as the Archipelago Sea, which will thereby become a biogeographically interesting contact zone. As many of the studied organisms are keystone species, their changing distributions will induce cascade effects at the ecosystem level.

The winter stratification phenomenon and its consequences in the Gulf of Finland, Baltic Sea

Abstract. Stratification plays an essential role in the marine ecosystem, with a shallow mixed layer being one of the preconditions for enhanced primary production in the ocean. In the Baltic Sea, the general understanding is that the upper mixed layer (UML) is well below the euphotic zone in winter. In this study, we demonstrate that wintertime shallow stratification is common in the Gulf of Finland and it forms at a depth comparable to the euphotic zone in January–February. The onset of restratification is likely associated with the annual cycle of westerly winds, which ease off in late January–early February. Stratification is first invoked along the northern coast by the westward advection of riverine water forced by easterly winds and is expanded to the south when the prevailing wind direction changes from an easterly to a westerly direction. Haline stratification emerges approximately 1 month later in the southern part of the gulf. Winter restratification can occur in the entire gulf and also in the absence of ice; thus, it is a regular seasonal feature in the area. Interannual variations in the wintertime UML correspond with variations in the North Atlantic Oscillation. Chlorophyll a concentrations in winter can be comparable to mid-summer; the limiting factor for phytoplankton bloom in winter is likely insufficient solar radiation.

Underwater Acoustic Environment of Coastal Sea With Heavy Shipping Traffic: NE Baltic Sea During Wintertime

Shipping is the most pervasive source of anthropogenic underwater continuous noise and local intermittent noise. This study focused on the separation of anthropogenic intermittent noise from dynamic background noise in the Gulf of Finland using an adaptive threshold level (ATL) technique. The intermittent noise was validated with Automatic Identification System (AIS) data and the background noise with selected environmental factors. Separated components were characterized and compared with a sound exposure level (SEL) in three 1/3 octave bands. Intermittent noise can be separated with ATL in the Baltic Sea, and vessel traffic identified as the primary source. Background noise varies spatially and is partially explained by environmental factors. Intermittent noise has strong persisting influence on the acoustic environment near shipping lanes, elevating the SEL in each of the 1/3 octave bands: by 20–30 dB in the 63 Hz band, by 13–22 dB in the 125 Hz band and by 5–8 dB in the 2000 Hz band. We conclude that strong intermittent noise is characteristic to the underwater acoustic environment in the study area with heavy shipping traffic. By combining ATL with data from AIS, intermittent noise peaks in underwater hydrophone recordings can be associated with passages of individual vessels.

Effects on the Liver Transcriptome in Baltic Salmon: Contributions of Contamination with Organohalogen Compounds and Origin of Salmon.

Hatchery-reared Atlantic salmon (Salmo salar) has been released to support the wild salmon stocks in the Baltic Sea for decades. During their feeding migration, salmon are exposed to organohalogen compounds (OHCs). Here, we investigated the OHC levels and transcriptome profiles in the liver of wild and hatchery-reared salmon collected from the Baltic main basin (BMB), the Bothnian Sea (BS), and the Gulf of Finland (GoF) and examined whether salmon origin and OHC levels contributed to the hepatic transcriptome profiles. There were no differences in the OHC concentrations between wild and reared fish but larger differences between areas. Several transcript levels were associated with non-dioxin-like polychlorinated biphenyls, polybrominated diphenylethers, chlordanes, and dichlorodiphenyltrichloroethane in a concentration-dependent manner. Between wild and reared salmon, lipid metabolism and related signaling pathways were enriched within the BMB and BS, while amino acid metabolism was altered within the GoF. When comparing the different areas, lipid metabolism, environmental stress and cell growth, and death-related pathways were enriched. Class coinertia analysis showed that the covariation in the OHC levels and the transcriptome were significantly similar. These results suggest that the hepatic transcriptomes in wild and hatchery-reared salmon are more affected by the OHC levels rather than the origin of salmon.

Observations of surface drift and effects induced by wind and surface waves in the Baltic Sea for the period 2011–2018

This study examines one of the longest collection of in-situ surface drifters, deployed at different seasons for the period of 2011–2018 in the Gulf of Finland, Baltic Sea. Overall 38 drifters deployed in batches of three were designed to capture the surface drift in the uppermost 2 m layer of the sea. The properties of drifter trajectories and the effects of wind and waves on the surface drift are analysed both qualitatively and quantitatively. The overall transport is asymmetric and the prevailing direction is out of the gulf against predominant winds. The most frequent drifter speed was 0.05–0.15 m/s (49% of occurrences) and wave height less than 0.5 m (46% of occurrences). Larger drifter speeds generally occurred during periods of stronger winds and higher waves. Wave heights >0.5 m and surface drift >0.15 m/s accounted for 21% of occurrences. In some occasions relatively high drifter speeds (>0.15 m/s) occurred under low wind and in almost calm sea (wave height of <0.5 m). These occasions accounted for 7% and 14% of occurrences, respectively. Rapid motions of drifters were apparently governed by other processes (e.g., eddies, fronts, upwellings, downwellings) during such episodes. For 68% of occurrences the surface current speed is 1.5% of the wind speed with an error of less than ±0.1 m/s. These results demonstrate that whilst wind and surface waves largely govern the surface drift on >2/3 of the occasions, underlying circulation may often dominate the motions in the uppermost layer in the study area.

Taxonomic reassignment of Pseudohaptolina birgeri comb. nov. (Haptophyta)

ABSTRACT The haptophyte genus Pseudohaptolina (formerly Chrysochromulina clade B1-3) currently harbours two species: Pseudohaptolina arctica and Pseudohaptolina sorokinii. In addition, Chrysochromulina birgeri is expected to belong to this genus due to its morphological similarity to P. sorokinii, but it has not yet been genetically characterised. A strain belonging to Pseudohaptolina was brought into culture from Arctic waters, characterised by 18S and 28S rRNA gene sequencing as well as optical and transmission electron microscopy, and deposited in the Roscoff Culture Collection with the code RCC5270. Molecular and morphological data from RCC5270 were compared with those from previously described Pseudohaptolina and Pseudohaptolina-like species. Strain RCC5270 showed strong phylogenetic affinity to P. sorokinii, but observations using transmission electron microscopy (TEM) showed that RCC5270 possesses three types of organic body scales, rather than two as originally described for P. sorokinii. We found that the occurrence of three scale types is likely to have been overlooked in the original descriptions of both P. sorokinii and C. birgeri. We also found that environmental metabarcodes identical to the sequence of RCC5270 were abundant at the location from which C. birgeri was initially described (Gulf of Finland). We conclude that P. sorokinii and C. birgeri are conspecific and P. sorokinii is therefore synonymous with C. birgeri. Based on its phylogenetic placement and nomenclatural priority, we propose the new combination Pseudohaptolina birgeri and emend the description of this species.

Peculiarity of long-term climate dynamics and its impact on the distribution and fishing of herring fish species in the Baltic Sea

The features of the interannual dynamics of the surface water temperature in the Central part of the Baltic Sea and in the Gulf of Finland over the past 70 years were analyzed. The total effect of the linear trend and the long-period component on the dispersion of the initial water temperature values in the Central part of the Baltic Sea was 48.4 %, and in the Gulf of Finland was 67.0 %. These two components in 1949–2018 determined the duration of two climatic phases: moderate (1949–1987) with a heat content close to normal and warm (1988–2018). The average rate of temperature increase in the last 31-year period (1988–2018) in the Central part of the Baltic Sea was 0.42 °C per 10 years, while in the Gulf of Finland it was 1.5 times higher. The beginning of the modern period of warming of water masses coincided with the weakening of the meridional type of atmospheric circulation in the North Atlantic and the strengthening of air transport from its water area in the Eastern direction. The increase of water temperature may be one of the reasons for the redistribution of commercial concentrations of herring and sprat in the Baltic Sea, thereby the change in their annual catch in certain ICES sub-divisions of the Central part of the Baltic Sea and the Gulf of Finland was observed.

A preliminary computational surface oil spill trajectory model for ice-covered waters and its validation with two oil spill events: A field experiment in the Barents Sea and an accidental spill in the Gulf of Finland

Trajectory estimation of an oil spill in ice-covered waters is essential for response planning and risk assessment. This paper presents the preliminary development of a new computational model for the estimation of spreading and surface transport of oil in the presence of ice. A new approach for the estimation of spreading in 0.8–0.95 ice concentration range is proposed. Additionally, for the first time the pumping of floating in‑leads oil onto or under ice floes with closing leads is modelled. The model is able to estimate the mobilization of under-ice oil and its potential subsequent surfacing and works as a stand-alone model with any rectangular-grid ice-ocean model. The model was used to simulate trajectories of two real-life spill events, a field experiment in the Barents Sea where oil and ice were observed to move together and an accidental spill in the Gulf of Finland. Model results were generally consistent with observations.

Temperature-related timing of the spring bloom and match between phytoplankton and zooplankton

ABSTRACT Global warming is causing changes in the food web structure and seasonal plankton dynamics. The Baltic Sea is one of the fastest-warming sea areas and warming consequently affects the timing and magnitude of phytoplankton blooms. Based on available Chlorophyll a data from nine years between 1979 and 2018, from the entrance to the Gulf of Finland, we studied the timing of the phytoplankton spring bloom in relation to spring seawater temperature. We found the peak of the bloom to occur earlier in years with higher spring seawater temperature. In warmer years, there was also a shorter time lag between phytoplankton and zooplankton biomass peaks. In addition, it seems as the spring bloom total biomass has decreased with time, with more extensive summer blooms during later years, in line with the general trend observed in the Baltic Sea. The spring bloom has traditionally been considered the most important part of the season, but we argue that the whole growth season should be investigated since summer blooms appear to increase with warming.

Polycyclic aromatic hydrocarbon sorption and bacterial community composition of biodegradable and conventional plastics incubated in coastal sediments

Resistant to degradation, plastic litter poses a long-term threat to marine ecosystems. Biodegradable materials have been developed to replace conventional plastics, but little is known of their impacts and degradation in marine environments. A 14-week laboratory experiment was conducted to investigate the sorption of polycyclic aromatic hydrocarbons (PAHs) to conventional (polystyrene PS and polyamide PA) and bio-based, biodegradable plastic films (cellulose acetate CA and poly-L-lactic acid PLLA), and to examine the composition of bacterial communities colonizing these materials. Mesoplastics (1 cm2) of these materials were incubated in sediment and seawater collected from two sites in the Gulf of Finland, on the coast of the highly urbanized area of Helsinki, Finland. PS sorbed more PAHs than did the other plastic types at both sites, and the concentration of PAHs was consistently and considerably smaller in plastics than in the sediment. In general, the plastic bacterial biofilms resembled those in the surrounding media (water and/or sediment). However, in the sediment incubations, the community composition on CA diverged from that of the other three plastic types and was enriched with Bacteroidia and potentially cellulolytic Spirochaetia at both sites. The results indicate that certain biodegradable plastics, such as CA, may harbour potential bioplastic-degrading communities and that PAH sorption capacity varies between polymer types. Since biodegradable plastics are presented as replacements for conventional plastics in applications with risk of ending up in the marine environment, the results highlight the need to carefully examine the environmental behaviour of each biodegradable plastic type before they are extensively introduced to the market.

Expansion Dynamics of Micruropus possolskii Sowinsky, 1915 (Amphipoda, Crustacea) in Lake Ladoga

Amphipods play the leading role among alien species in Lake Ladoga. In particular, the Baikal species Micruropus possolskii Sowinsky, 1915 is becoming increasingly important here. The purpose of this paper is to present updated data on the appearance of M. possolskii in Lake Ladoga and on the temporal and spatial dynamics of its development and expansion in this water body. The species was initially recorded in the Shchuchiy Bay of Lake Ladoga in 2003. Its spread to the south to the Petrokrepost Bay (where it was recorded in 2017) is shown. The further expansion of the species in Lake Ladoga and its significant quantitative development in the colonized biotopes and possible expansion to Lake Onega and the Neva Bay of the Gulf of Finland are expected.

Meteotsunami occurrence in the Gulf of Finland over the past century

Abstract. We analyse changes in meteotsunami occurrence over the past century (1922–2014) in the Gulf of Finland, Baltic Sea. A major challenge for studying these short-lived and local events is the limited temporal and spatial resolution of digital sea level and meteorological data. To overcome this challenge, we examine archived paper recordings from two tide gauges, Hanko for 1922–1989 and Hamina for 1928–1989, from the summer months of May–October. We visually inspect the recordings to detect rapid sea level variations, which are then digitised and compared to air pressure observations from nearby stations. The data set is complemented with events detected from digital sea level data 1990–2014 by an automated algorithm. In total, we identify 121 potential meteotsunami events. Over 70 % of the events could be confirmed to have a rapid change in air pressure occurring shortly before or simultaneously with the sea level oscillations. The occurrence of meteotsunamis is strongly connected with lightning over the region: the number of cloud-to-ground (CG) flashes over the Gulf of Finland were on average over 10 times higher during the days when a meteotsunami was recorded compared to days with no meteotsunamis in May–October. On a monthly level, statistically significant differences between meteotsunami months and other months were found in the number of CG flashes, convective available potential energy (CAPE), and temperature. Meteotsunami occurrence over the past century shows a statistically significant increasing trend in Hamina, but not in Hanko.

Palaeorunoff from Lake Ladoga to the Baltic Sea during the Holocene

The article presents the results of the palaeohydrological analysis of the river system reorganization in the North-West of Russia, the Karelian Isthmus. This study aimed at the hydrological calculation of the runoff through the Heinjoki water connection of Lake Ladoga, the Gulf of Finland and PalaeoVuoksa during different periods of the Holocene. The methods of the equation of water balance, hydraulic-morphometric dependencies and the method of geographical analogy were used in this research. The main result of the carried work is the refinement of the existing regional flow model. In particular, the role of the Heinjoki Strait and the Neva River channel in different stages of the Holocene is considered. The authors came to the conclusion that Lake Ladoga always had a runoff to the Baltic Sea. It is shown that most probably in the period of 10,200-3,500 years ago the runoff was carried out through the Heinjoki waterway. The study underlines that the isostatic factor played a significant role in the forming of the water flow. The change in the runoff direction from the Heinjoki waterway to the Neva River is mainly related to the isostatic uplift of the Karelian Isthmus and the northern part of Lake Ladoga. Quantitative parameters of the Heinjoki palaeoflow (flow rate, annual runoff, runoff layer, runoff coefficient) seem to be roughly equivalent to the modern parameters of the flow of the Neva River. The article is dedicated to our colleague, a talented geographer and teacher, PhD Oleg Borisovich Averichkin (1979-2010) who first performed the calculations of the paleorunoff of Lake Ladoga

STUDY OF STEELS CORROSION RESISTANCE TO SEAWATER IMPACT

Background The use of carbon steels in seawater does not provide a sufficient degree of pipelines and equipment protection from corrosion, the use of alloy steels is complicated by their tendency to localized corrosion processes. Aims and Objectives To investigate the effect of seawater impact on the corrosion resistance of 10Х17Н13М2Т, 12Х18Н12М3ТЛ, 20Л and 20Х13 steels, allowed for valves manufacture. Results 1. 10Х17Н3М2Т and 12Х18Н12М3ТЛ steels have high corrosion resistance in seawater models of both the Gulf of Finland and the Gulf of Nakhodka. The rate of general corrosion does not exceed 0.004 mm per year, there is no pitting corrosion. 2. 20 Л steel has low corrosion resistance in seawater models. The rate of general corrosion of this steel in static is 0.28 mm per year in the model of seawater in the Gulf of Finland and 0.17 mm per year in the model of the Nakhodka Bay; in dynamics - 0.51 mm per year for the Gulf of Finland and 0.26 mm per year for the Gulf of Nakhodka. Local corrosion rate in seawater models was 0.69-0.79 mm per year. 3. The rate of general corrosion of 20X13 steel in seawater models is 0.01-0.05 mm per year; however, this steel is much susceptible to pitting corrosion. The local corrosion rate in the seawater model of the Gulf of Nakhodka was 11.7 mm per year.

Characteristics and Structure of the Cumulonimbus Cloud with Waterspout over the Gulf of Finland

The characteristics of the сumulonimbus cloud with waterspout that has passed over the Gulf of Finland are analyzed. The characteristics were obtained from polarimetric Doppler weather radar, radiometer, and lightning detector data. The waterspout was formed close to the cyclone center. The analysis of instability indices revealed high atmospheric instability. The sinking of the rotational motion in the cloud before the waterspout generation is shown. The radar characteristics of the cloud at the moment of waterspout observation are considered in detail. It is concluded that good identifiers for the waterspout detection are the “Zdr column” and the zone in the lower part of the cloud with differently directed values of Doppler velocity and with the high values of velocity spectrum width.

The impact of publication on freshwater pearl mussel conservation: To conceal or to reveal the location of threatened habitats?

Abstract The freshwater pearl mussel, Margaritifera margaritifera, is a threatened species. One of the threats faced by this species is direct extermination by poachers, and therefore some researchers conceal information on the locations of pearl mussel habitats. For example, some researchers do not publish the names of the rivers where pearl mussels occur, whereas other researchers do. Concealing the names of rivers containing pearl mussels makes them unknown not only to potential offenders but also to administrators, nature conservation practitioners, and ordinary citizens. As a result, no protection measures are undertaken, which is all the more regrettable as damage to pearl mussel habitats can occur accidentally. Concealing details of the location of pearl mussel habitats in publications has an adverse impact on the work of specialists, as they do not have access to enough information to study and analyse the biology and distribution of these molluscs. One river with pearl mussels in the Gulf of Finland was initially described anonymously (as ‘River B’). Unfortunately, the river was subject to severe human impact, and the largest aggregation of pearl mussels was almost exterminated in the process of constructing a new electric supply line. Concealing information on pearl mussel habitats in the Russian section of the Baltic Sea basin was also shown to have been a poor decision. Although the threat from potential poachers was insignificant because of the low commercial value of pearl mussels, the authorities remained uninformed about the existence of valuable habitats. The question of whether the locations of pearl mussel habitats should be concealed or revealed in scientific publications does not have an unambiguous answer and should be considered on a case‐to‐case basis; however, the cases for which disclosure is reasonable seem to be more numerous.

Temporal Variability of the Wind Wave Parameters in the Baltic Sea in 1979–2018 Based on the Numerical Modeling Results

Purpose. The aim of the paper is to identify possible trends in the wave climate dynamics in the Baltic Sea, and to analyze statistical significance of the coefficients of these trends based on the results of their numerical modeling for 1979–2018. Methods and Results. The simulations for 1979–2018 (40 years) were carried out on an irregular grid using the MIKE 21 SW spectral wave model. The wind forcing was preset according to the ERA-Interim reanalysis data. The model was calibrated and validated against the data of wave buoys located in the northern and southern parts of the Baltic Sea. Based on the calibrated model, the wind wave parameters were calculated for the whole Baltic Sea area from 1979 to 2018 with the interval 1 hour. These parameters became the initial data for estimating temporal variability of the wind wave heights in the Baltic Sea for 40 years. The simulation results obtained on the irregular grid were interpolated to the regular one. It permitted to construct the maps of distribution of the maximum and average (for the 40-year period) significant wave heights in the Baltic Sea. The time trends for the average annual significant wave height values were revealed, and statistical significance of the coefficients of these trends was estimated. Conclusions. The average annual values of the significant wave heights over almost the whole Baltic Sea area for 1979–2018 (40 years) tend to decrease with the rate not exceeding 2–3 cm (2–3 %) per 10 years. The highest rate reduction is observed in the southeastern part of the Baltic Sea, the lowest – in the Gulf of Bothnia and the Gulf of Finland. Interannual variability of the average annual significant wave heights and the changes along the trend during the entire 40-years period are of the same order.

Vremennáya izmenchivost' parametrov vetrovykh voln v Baltiyskom more za period 1979-2018 godov po rezul'tatam chislennogo modelirovaniya

Purpose . The aim of the paper is to identify possible trends in the wave climate dynamics in the Baltic Sea, and to analyze statistical significance of the coefficients of these trends based on the results of their numerical modeling for 1979–2018. Methods and Results . The simulations for 1979–2018 (40 years) were carried out on an irregular grid using the MIKE 21 SW spectral wave model. The wind effect was preset according to the ERA-Interim reanalysis data. The model was calibrated and validated against the wave buoys’ data in the northern and southern parts of the Baltic Sea. Based on the calibrated model, the wind wave parame-ters were calculated for the whole Baltic Sea area from 1979 to 2018 with the interval 1 hour. These parameters became the initial data for estimating temporal variability of the wind wave heights in the Baltic Sea for 40 years. The simulation results obtained on the irregular grid were interpolated to the regular one. It permitted to construct the maps of distribution of the maximum and average (for the 40-year period) significant wave heights in the Baltic Sea. The time trends for the average annual significant wave height values were revealed, and statistical significance of the coefficients of these trends was estimated. Conclusions. The average annual values of the significant wave heights over almost the whole Baltic Sea area for 1979–2018 (40 years) tend to decrease with the rate not exceeding 2–3 cm (∼2–3%) per 10 years. The highest rate reduction is observed in the southeastern part of the Baltic Sea, the lowest – in the Gulf of Bothnia and the Gulf of Finland. Interannual variability of the average annual signifi-cant wave heights and the changes of its trend in course of the 40-year period are of the same order.

Detection of the cloud liquid water path horizontal inhomogeneity in a coastline area by means of ground-based microwave observations: feasibility study

Abstract. Improvement of cloud modelling for global and regional climate and weather studies requires comprehensive information on many cloud parameters. This information is delivered by remote observations of clouds from ground-based and space-borne platforms using different methods and processing algorithms. Cloud liquid water path (LWP) is one of the main obtained quantities. Previously, measurements of LWP by the SEVIRI (Spinning Enhanced Visible and InfraRed Imager) and AVHRR (Advanced Very High Resolution Radiometer) satellite instruments provided evidence for the systematic differences between LWP values over land and water areas in northern Europe. An attempt is made to detect such differences by means of ground-based microwave observations performed near the coastline of the Gulf of Finland in the vicinity of St Petersburg, Russia. The microwave radiometer (RPG-HATPRO, Radiometer Physics GmbH – Humidity And Temperature PROfiler), located 2.5 km from the coastline, is functioning in the angular scanning mode and is probing the air portions over land (at an elevation angle of 90∘) and over water (at seven elevation angles in the range 4.8–30∘). The influence of the land–sea LWP difference on the brightness temperature values in the 31.4 GHz spectral channel has been demonstrated, and the following features have been detected: (1) an interfering systematic signal is present in the 31.4 GHz channel, which can be attributed to the humidity horizontal gradient, (2) clouds over the opposite shore of the Gulf of Finland mask the LWP gradient effect. Preliminary results of the retrieval of LWP over water by the statistical regression method applied to the microwave measurements by HATPRO in the 31.4 and 22.24 GHz channels are presented. The monthly averaged results are compared to the corresponding values derived from the satellite observations by the SEVIRI instrument and from the reanalysis data.