Summer blooms of potentially harmful cyanobacteria are common in the Baltic Sea. Under clear sky conditions, the cyanobacterial blooms are easily detectable from space. We propose a new regional algorithm for cyanobacteria biomass estimation from satellite data in the eastern part of the Gulf of Finland, developed on the basis of field measurements in July–August 2012–2014. The multi-regression equation defines the cyanobacteria biomass as a function of the particle backscattering coefficient and chlorophyll concentration. The use of this equation provides the best performance in comparison to the linear one, which is reflected in both R2 and RMSE values (0.61 and 272 mg m−3 respectively). Unlike other algorithms, which determine only the cyanobacteria bloom area in the Baltic Sea, our algorithm allows the determination of both a bloom area and its intensity. Considering the algorithm errors, the bloom detection threshold has been shifted from the 200 mg m−3 determined by biologists to 300 mg m−3. Based on data from the MODIS-Aqua satellite ocean color scanner, the spatial and temporal variability of cyanobacterial blooms in this region from 2003 to 2022 was analyzed. Significant interannual variability of cyanobacteria biomass was revealed in the central part of the studied region, with minimum values in 2014 and maximum in 2004. The record bloom during the studied period occurred in July 2004 (the average cyanobacteria biomass was 780 mg m−3). The weakest blooms were observed in 2009, 2010, and 2014, when both in July and August, the bloom areas did not exceed 30% of the study region.

The data on the calculation of bio-optical parameters in the Barents Sea are presented, for which regional algorithms have been developed. These algorithms were derived on the basis of field measurements made in the region under consideration. The seasonal and interannual variability of bio-optical characteristics was studied and coccolithophore blooms in the Barents Sea were evaluated.

Our work’s primary goal is to reveal the problematic issues related to estimates of the colored organic matter absorption coefficient in the northern seas from data of the Ocean and Land Color Instrument (OLCI) installed on the Sentinel-3 satellites, e.g., a comparison of the OLCI standard error assessment ADG443_NN_err relating to the measurement and the retrieval of the geophysical products and the uncertainties in the northern seas’ real situation. The natural conditions are incredibly unfavorable there, mainly due to frequent cloudiness and low sun heights. We conducted a comprehensive multi-sensor study of the uncertainties using various approaches. We directly compared the data from satellites (OLCI Sentinel-3 and four other ocean color sensors) and field measurements in five sea expeditions (2016–2019) using the different processing algorithms. Our analysis has shown that the final product’s real uncertainties are significantly (≥100%) higher than the calculated errors of the ADG443_NN_err (~10%). The main reason is the unsatisfactory atmospheric correction. We present the analysis of the various influential factors (satellite sensors, processing algorithms, and other parameters) and formulate future work goals.

The goal of this work is to study the influence of coccolithophore blooms on the underwater light field and albedo of the water column. A coccolithophore is a single-celled alga with spherical cells surrounded by disk-shaped calcite plates (coccolites), which produce strong light scattering. Because of that, we can observe coccolithophore blooms on satellite ocean color images. We calculated the angular underwater radiance distributions and their integral parameters by the exact numerical method with the input parameters, corresponding to real conditions observed in the Barents Sea and Black Sea. Using the results of the exact calculations, we estimated, for various situations, the accuracy of the approximating formulas applied to the assessment of the water radiance reflectance and the diffuse attenuation coefficients and we make recommendations for their application. As a finding of practical importance, we can note the estimate of the accuracy of the widely used Gordon’s formula for the diffuse attenuation coefficient; this formula results in large errors under strong coccolithophore blooms. We also mention the interesting and important results concerning the features of the asymptotic regime under such conditions.

The article is dedicated to the 70th birthday of Vladimir Aleksandrovich Artemiev, senior researcher at the Ocean Optics Laboratory of the IO RAS. This is a unique electronics specialist who directly performs scientific research and provides this opportunity to others. V.A. Artemyev has been developing and improving optical equipment for marine expeditionary research for over 40 years; Among the devices he developed are an underwater irradiance meter (Alfamer device), three types of submersible transparent meters (PUM, PUM-A, PUM-200). Member of more than 60 sea expeditions from the Arctic to the Antarctic and about two dozen coastal marine. Conducted measurements of the underwater brightness of solar radiation at depths of up to 300 m in the Philippine Sea, diving on the Pysis underwater manned vehicle (PA), and in the Black Sea on the Argus PA. Vladimir Aleksandrovich is an irreplaceable expeditionary employee both in terms of his business and human qualities: contact, benevolent, always ready to help, creating a friendly atmosphere in the team. Coauthor of over 80 scientific publications and one invention patent. Has state awards.

Data on the light absorption by seawater and its components are needed in many theoretical and practical aspects of marine science and engineering. However, up to now, there is a lack of such data for the northeastern part of the Black Sea. This article presents the data on light absorption measured by a portable integrated cavity absorption meter (ICAM) spectrophotometer in the Gelendzhik region of the Black Sea during field studies in June 2017 and 2018, together with other bio-optical and oceanographic data from in situ measurements and satellite observations. In 2018, the elevated values of the colored dissolved organic matter (CDOM) absorption in the surface layer were observed concurrently with high values of salinity, contradicting the idea of river runoff being the main CDOM source. The vertical profiles of salinity differed in 2017 and 2018, especially in shallow waters; in the upper layer, the salinity increased from 17.1 psu in 2017 to 17.8 psu in 2018, while the values of CDOM absorption increased from 0.10 to 0.16 m−1. The analysis of available hydrometeorological data pointed to intensive vertical mixing due to the strong wind forcing as a main factor in increasing values of both salinity and the CDOM absorption in the surface layer in 2018.

X Anniversary All-Russian Conference with international participation “Current Problems in Optics of Natural Waters” (ONW’2019) was held in St. Petersburg from October 9 to 11; 57 reports were presented on the main aspects of modern ocean optics, including fundamental problems of radiation transfer theory, field studies, remote sensing, especially satellite ocean color sensors, and lidars, new methods, and equipment.

Представлены обобщённые результаты исследований биооптических характеристик поверхностного слоя вод Баренцева, Карского морей и моря Лаптевых, полученные по судовым и спутниковым данным, и интерпретация наблюдаемых явлений. Выполнен совместный анализ данных измерений о пространственном распределении биооптических характеристик, полученных в 2018 г. с помощью судового проточного комплекса, и спутниковых наблюдений за период 2003-2017 гг., который позволил выявить роль основных процессов, определяющих это распределение, его сезонные и межгодовые изменения. Показано, что пространственные распределения интенсивности флуоресценции окрашенного растворенного органического вещества и хлорофилла хорошо соответствуют гидрофизическим характеристикам в области влияния речного стока; пространственные распределения показателя ослабления хорошо с ними согласуются. Полученные данные позволили определить положение арктических и атлантических вод и кокколитофоридных цветений в Баренцевом море, выделить границы распространения опресненного слоя в морях Карском и Лаптевых. Представлены статистические оценки связи между биооптическими характеристиками Баренцева и Карского морей по спутниковым данным.

Practical questions of quickly determining the sea water absorption factor using an integrating sphere are considered: measurement technique and data processing, as well as reference solution calibration. Numerical experiments using the Monte-Carlo method are performed to evaluate the influence of the device features (absence of spherical symmetry and the presence of a reflection specular component from the quartz shell) on the determination of the absorption factor considering scattering properties of the medium. Examples of how the results of the proposed technique can be used are given under the conditions of sea expeditions.

ГЛАВА ЦЕЛИ И ЗАДАЧИ ИССЛЕДОВАНИЙЦель выполненных исследований -получение для северо-восточной части Черного моря комплекса данных оптических и сопутствующих измерений в сочетании с данными спутниковых наблюдений для усовершенствования спутниковых методов оценки биооптических характеристик вод поверхностного слоя.

The goal of the study is to examine spatial and temporal variability of total suspended matter (TSM) concentration in the surface layer of the South-eastern Baltic (SEB) based on satellite and in situ data. The TSM concentration was estimated from in situ measurements and MODIS-Aqua satellite data for 2003-2016. The maximum of TSM concentration is located alongside the coast of the Sambia Peninsula (2.5 mg/l). MODIS-derived TSM concentrations demonstrate a precise boundary between higher concentrations of particles in the coastal zone (1-2.5 mg/l) and lower values offshore (less than 1 mg/l) for the whole region during a year. There are three seasonal peaks in TSM values - April, June and August, that is associated with algae blooming. The coastal stations also show October maximum which appears to be owing to storms, forcing the coastal abrasion. Interannual variations of TSM concentration during the observation period are not significant in the offshore area, while considerable interannual variations are typical for the coastal zone. It is obvious that satellite-derived TSM data has benefits due to larger amount of data, but it shows lower annual mean TSM concentrations than in situ data.

The south-eastern Baltic Sea is a particular sensitive marine area which includes coastal waters, shallow land-locked lagoons, and freshwater inflow areas. Thus, it requires monitoring and control of core environmental indicators such as suspended matter concentration. Spatial distribution and temporal variability of the total suspended matter concentration in the sea surface layer was analysed using in situ data and moderate resolution imaging spectroradiometer (MODIS) satellite imagery for 2003-2016. Manifestations of the major contributors of terrigenous particles and organic matter penetrating the study area were revealed.

Россия, 115432, Москва, 2-й Кожуховский пр-д, 12, строение 1 Реферат.В работе представлен краткий обзор современных возможностей дистанционного зондирования океанов и морей из космоса для мониторинга климатически значимых биооптических (биогеохимических и биологических/экосистемных) параметров океана.В данной статье обсуждаются основные климатические биооптические переменные -«цвет океана» и «фитопланктон», которые внесены в перечень из 54 основных климатических переменных, необходимых для систематических наблюдений с целью оценки климатических изменений на Земле, в рамках программы Глобальной системы наблюдений за климатом (GCOS).Предлагается дополнительный список климатически значимых биооптических параметров океана, который уточняет и расширяет список этих параметров, поскольку «цвет океана» и «фитопланктон» достаточно неопределенные параметры по сравнению с другими гидрофизическими пара-

Представлены результаты валидации параметров кокколитофоридных цветений, рассчитанных по данным спутниковых наблюдений и натурных измерений спектрального коэффициента яркости моря R в экспедициях ИО РАН в Баренцевом море в 2016 и 2017 гг. Основные рассматриваемые параметры - концентрация клеток кокколитофорид N, рассчитанная по региональному алгоритму ИО РАН, и концентрация взвешенного неорганического углерода PIC, стандартный продукт НАСА. Оба параметра рассчитываются через показатель рассеяния назад взвешенными частицами b. Выполненная валидация включала, во-первых, оценку ошибок атмосферной коррекции путем сопоставления значений R, рассчитанных по спутниковым данным и данным судового спектрорадиометра. Во-вторых, - валидацию «дистанционных» значений показателя b и концентрации N, используя данные прямых определений концентраций клеток кокколитофорид и отделившихся кокколитов на отобранных пробах морской воды. В-третьих, сопоставление рассчитанных значений N и PIC. Результаты работы показывают, что при благоприятных погодных условиях по спутниковым данным можно получать приемлемые оценки концентрации N; для улучшения точности необходимо учитывать особенности изменчивости характеристик фитопланктона. Получено уравнение регрессии для связи между среднемесячными значениями N и PIC для июля-августа с коэффициентом детерминации 0.82 и относительной ошибкой 18 % для расчета PIC через N.

The article considers the problems and opportunities associated with the use of visible radiation in the study of seas and oceans. Sea water is a light-scattering environment, and in most important cases scattering prevails over absorption. Therefore, for theoretical evaluations of spreading sunlight and radiation of artificial sources in an underwater environment, one should use solutions of integro-differential equation of radiation transfer, which has required the development of various special methods. A measurement of the light field parameters in an underwater environment also presents considerable difficulties caused primarily by weather conditions, which are cloud cover and surface waves. The theory of underwater vision has its own specific characteristics, especially when observation of underwater objects takes place through a turbulent sea surface. An interesting example relating to this problem is given in the review. Another example illustrates modem possibilities of underwater vision at the greatest ocean depths. Light as an instrument to study and monitor the marine environment has important advantages and even distinct preferences in comparison with other methods. One of them is the ability of light to penetrate the sea surface with small losses (unlike microwave radiation and sound), which allows applying remote light probing of the ocean subsurface layer (from boats, aircrafts and satellites). With the appearance of lidar using laser pulses for probing and with the development of satellite observations, remote optical methods are becoming more and more widespread.

Based on satellite and in situ data, we quantitatively estimated the penetration of PAR (photosynthetically available solar radiation in the visible spectral range of 400–700 nm) into waters of the central Barents Sea in the summer seasons of 2014–2016. The effects of cloudiness and coccolithophore blooms on the incidence and penetration of PAR was examined. These blooms occur in the Barents Sea almost every year. We estimated the impact of visible solar radiation on the SST against a background of incoming warmer waters of the Norwegian Current and established that the PAR impact is the most pronounced under clear sky conditions in July and August.