Retrieval of the land-sea contrast of cloud liquid water path by applying a physical inversion algorithm to combined zenith and off-zenith ground-based microwave measurements

Combined zenith and off-zenith ground-based observations by modern microwave radiometers provide an opportunity to study horizontal inhomogeneities of the humidity field in the troposphere and of the cloud liquid water path (LWP) spatial distribution. However, practical applications are difficult and require thorough analysis of the information content of measurements, assessment of errors of data processing algorithm and the development of the quality control procedures. In this study we analyse the application of our LWP retrieval algorithm based on the inversion of the radiative transfer equation to the problem of detection of the LWP horizontal inhomogeneities by means of ground-based microwave observations in the vicinity of a coastline of a water object of medium size. The study is based on data acquired by the microwave radiometer RPG-HATPRO which is located in the suburbs of St.Petersburg, Russia, at 2.5 km distance from the coastline of the Neva Bay (the Gulf of Finland) and is operating in angular scanning mode in the vertical plane. The retrieval setup is organised in such a way that zenith and off-zenith measurements provide equal sensitivity to atmospheric parameters. The optimal elevation angles for off-zenith observations are selected. The possibility to detect LWP horizontal inhomogeneity, namely the LWP land-sea contrast, for different measurement geometries (elevation angles) and values of cloud base height is analysed. It is shown that ground-based microwave observations in the vicinity of a coastline can be a valuable tool for validation of the space-borne measurements of the LWP land-sea contrast if three principal requirements are met: (a) the multi-parameter physical inversion method is used for retrieving LWP; (b) rigorous bias correction and quality control procedures are applied to the retrieval results; (c) the information on the cloud base height is available. As a result of processing the microwave measurements at the observational site of St.Petersburg State University, the monthly-averaged values of the LWP land-sea difference have been obtained for summer months within the period 2013–2021. For 24 out of 25 months of high quality observations, the LWP land-sea monthly difference is positive (larger values over land and smaller values over water) and can reach 0.06–0.07 kg m−2. The estimations of the LWP land-sea contrast obtained from the ground-based microwave measurements at the observational site of St.Petersburg University are in very good agreement with the values of the LWP land-sea contrast obtained from the multi-year space-borne measurements by the SEVIRI instrument (Spinning Enhanced Visible and InfraRed Imager) in the region of the Neva Bay (the Gulf of Finland) in June and July. For August, the so-called “August anomaly” detected by space-borne observations is not confirmed by the ground-based measurements.

New data on the flora of Centrophyceae (Bacillariophyta) in the Neva Bay of the Gulf of Finland (Russia)

This scanning electron microscopy study of phytoplankton from the Neva Bay and analysis of valve images from S.I. Genkal’s iconotheka have provided new data on centric diatoms of the Neva Bay. Representatives of the genera Aulacoseira scalaris and Stephanodiscus lacustris, new to the flora of the Bay, have been identified. The systematic position and distribution of 14 species and varieties of Centrophyceae from the genera Aulacoseira, Conticribra, Cyclostephanos, Ellerbeckia, Handmannia, Pantocsekiella, Stephanodiscus, Thalassiosira have been refined and specified. The species composition of the class Centrophyceae of the Neva Bay has been expanded. Now it includes 42 species and varieties from 17 genera.

The very first experience of biological analysis of water in Saint-Petersburg

The biological method of water quality analysis, for the first time, was applied in Russia during the examination of Neva Bay of the Gulf of Finland in the Baltic Sea by Wislouch S.M. Neva River was a source of drinking water in St. Petersburg and, at the same time, a discharge for all city drains. As a result, it became hazardous to health, being a source of various diseases, especially cholera. From August 1911 to September 1912 pollution studies of the Bay were made to solve the question - where to send the treated waste water of the future sewage system of St. Petersburg. In total, 37 trips were made during this time, 510 samples were taken, including 375 plankton samples and 35 benthic samples. Wysłouch S. M. gave an overview of objects collected at 265 stations located in the area of Neva Bay - from estuary of Bolshaya Neva to Kronstadt, along the southern coast of the Bay and partially along the Northern coast. He brought a list of algae, including 97 species: Algae Cyanophyceae (writing all taxa retained on original source) – 17 species, Flagellata – 19 species, Peridineae – 1, One – 30, Conjugatae – 2, Diatomaceae – 28 species, Fungi (1), Bacteria (17), Protozoa (28), Rotatoria (17). Taking into account the algae and other organisms saprobity indices, areas with different degrees of contamination were identified. All the data was put on map of the Gulf. The most heavily polluted area was the Sea channel, and the area between the Lisij Nos and Kronstadt was the cleanest.

The European river lamprey Lampetra fluviatilis (L., 1758) (Petromyzontidae) as a component of the Neva Bay bottom coenoses

The presence of larvae of the European river lamprey Lampetra fluviatilis was reported for the first time from in macrobenthic communities of the Neva Bay of the Gulf of Finland (St. Petersburg, Russia). It has been shown that ammocoetes inhabit several areas, at depths to 12 meters. Apart from ammocoetes, the communities with lamprey larvae contain abundant oligochaetes, bivalves, and less commonly chironomid larvae. At some sites, the number of larvae was up to 80 specimens/m2, while their biomass was over 90% of the total of the community. The abundance of macrozoobenthos in these sites is generally low (average abundance 190 specimens/m2, biomass – 70 g/m2), which is usual in autumn. Intestines of the ammocoetes constantly contained large quantities of diatoms representing common phytoplankton of the Gulf of Finland.

Structure and functioning of phytoplankton in the Neva estuary in 2011–2016

Long-term observations (since 1982), which had been carried out in the Neva River estuary, have shown that in 2011–2016 the general nature of distribution, species composition and abundance of phytoplankton differed from those that were recorded earlier. The greatest changes are noted in the central part close by northern coast of the Neva Bay. With observed eutrophication in the Neva Bay (st. 12) and in the eastern part of the Gulf of Finland (st. 19), different groups of algae dominated in the summer phytoplankton (late July – early August). The main mechanism regulating the species composition of phytoplankton were hydrological conditions observed in different parts of the estuary. Also Shallow water, wind activity, oxygen deficiency and temperature stratification, nutrient supply were favorable conditions for development of chlorococcal green, cryptophyte, euglenic and other algae groups. With a high Shannon index (3.8–4.0) in the Neva Bay, the largest share to the total biomass was given by chlorococcal algae. In the resort area of the Gulf of Finland at the end of July – early August, direct temperature stratification was usually established, with enough nutrients creating conditions for the development of stagnophilic planktonic algae with a predominance of cyanobacteria in the epilimion. Here, more often, were periods of surface “blooms”. For the most eutrophied areas of the Neva Bay and the inner estuary the average structural, functional, and relative indicators of plankton were compared with average values for the entire water area. The main characteristics of phytoplankton: biomass, primary production, chlorophyll concentration and total phosphorus content in the northern zone of the Neva Bay, were 2–3 times higher than the average values on the Gulf. The species composition of algae corresponded to a sufficiently high trophic state. In the resort area of inner estuary of the Gulf of Finland (st. 19), the observed mean values also slightly exceeded the average values for the estuary, but the relative indicators differed little from those calculated for the rest of the water area. The structural and functional characteristics of phytoplankton indicated that during eutrophication in different parts of the estuary, in Summer, conditions wer favorable to promote the development of different groups plankton algae.

Experimental studies of benthos resistance to mechanical burying under the dredging material

The goal of the fulfilled research is the study of the influence of the sedimentary suspension from the dredging material on the benthic hydrobionts. In laboratory aquariums six series of experiments were carried out with triple replication on the ability of different benthic organisms to dig out the soil strata due to their periodic burying by marine sand. These experiments were oriented on biota of Eastern Gulf of Finland and the Neva Bay, where a number of deposit sites for dredging material are located presently. Representatives of three main groups of hydrobionts of these areas were selected for experiments – Chironomidae, Gastropoda and Oligochaeta. The ability of different hydrobiont species to overcome the stress effect of the burying under the dredged material was estimated quantitatively. The results show, that the resistance of the studied species to mechanical burying is decreasing in accordance to the scheme: Chironomus plumosus > Melanoides tuberculata > Tubifex tubifex, and depends from the thickness of the layer of dredged material.

Results of investigations of the Neva Bay technosphere at RSHU

The article summarizes the results of the long-term complex observations of formation and development of the technosphere in the coastal zone of the Neva Bay and its impact on coastal hydro-biological communities by RSHU scientists. Natural and administrative borders of the Neva Bay are described and discussed. Evolution of the Neva Bay from «natural geosystem» to the «natural-and technical system» is monitored and analyzed. Peculiarities of coastal biological communities are presented. Anthropogenic stress-factors connected with hydrotechnical construction and dredging with high level of negative influence on coastal ecosystems are revealed. The program of original complex research of the functioning of the coastal «natural-and technical system» is proposed. Areas of hydrotechnical and dredging projects and parallel environmental monitoring in the Neva Bay are mapped. Artificially reclaimed coastal territories are recognized as core elements (knots) of the coastal technosphere of the Neva Bay. Anthropogenic macro-objects constructed on these areas, such as ports, business centers, elements of logistic structure, and recreational areas are observed from the «sustainable development» point of view. The effects of technosphere on abiotic and biotic components of coastal ecosystems are shown. To study the spatial and temporal variability of the state of the Neva Bay and its coastal zone under the influence of sedimentation processes and man-made impacts, high- and medium-resolution satellite data have been used. Some results from satellite observations are compared and discussed. Based on the research results, a map of the integral ecological vulnerability of the Neva Bay in relation to hydrotechnical works and dredging has been constructed. Information about the established levels of environmental vulnerability of various sections of the Neva Bay water area can be used for the benefit of marine spatial planning. Methods and technologies of compensatory measurements are compared and discussed in order to find optimal actions. Organizing of nature protection areas is recommended as a complex method for the support of the coastal zone sustainable development

Long-term monitoring of the dredged material deposit sites in the Eastern Gulf of Finland

The goal of the paper is summarizing the results of the 20-years monitoring of the deposit sites of the dredged material in the Eastern Gulf of Finland (EGoF) and in the Neva Bay. The biotic and abiotic components of deposit sites ecosystems were observed there in 1999-2019, with using standard monitoring methods, in order to reveal effects of dumping on hydrobiologic communities and to determine their environmental status. The Biota Condition Index for 6 deposit sites was calculated and compared to areas which are not stressed by dumping. It is shown that the biological communities (especially – benthic) in the deposit sites areas are enormous not-sustainable and start their succession from the zero point every time after repeating stressing effect of dumping.