Science and earth science

Oceanologia

Content

Oceanologia | 2025 | Vol. 67 | No 1

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Abstract

Heterotrophic nanoflagellates (HNF) are key players in marine microbial food webs, but their distribution remains poorly understood. We investigated abundance patterns of eleven HNF lineages in the Baltic Proper from May to September 2021 using Catalysed Reporter Deposition-Fluorescence In Situ Hybridisation (CARD-FISH). HNF were most abundant in surface waters, where they reached above 12,000 cells ml−1 in May. Median cell size varied between 3.3–4.1 μm. CRY-1 cryptophytes, Marine Stramenopiles from MAST-2 lineage, and Kathablepharidacea dominated the HNF community in surface and suboxic/sulphidic waters below the halocline. Our results make an important contribution to the understanding of HNF ecology in the Baltic Sea.
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Authors and Affiliations

Kasia Piwosz
1
Anetta Ameryk
1
Klaudia Wdówka
1
Marlena Mordec
Uroosa Uroosa
1 2
Anastasiya Chuvakova
1
Sohrab Khan
1
Jared Vincent Lacaran
1

  1. Department of Fisheries Oceanography and Marine Ecology, National Marine Fisheries Research Institute, Kołłątaja 1, 81–332 Gdynia, Poland
  2. Institute of Oceanology of Polish Academy of Sciences, Sopot, Poland
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Abstract

Oceanic mesoscale eddies and their physical and dynamical characteristics are studied using a high-resolution numerical model in the Bay of Bengal (BoB), a semi-enclosed bay based in the northeast Indian Ocean (IO). The formation, duration, and kinetic energy of these eddies are primarily influenced by the intensity of surface currents, upper-ocean stratification, and regional bathymetry. The Indian Ocean Dipole (IOD) is a dominant mode of interannual variability in the IO, which influences ocean currents in the BoB apart from the well-known dipole observed in sea surface temperature between eastern and western IO. The high-resolution numerical experiments with positive and negative phases of IOD atmospheric forcing reveal the influence of anomalous circulation prevailing in the negative IOD (nIOD) and positive IOD (pIOD) on mesoscale eddies and their kinetic energy in the BoB. A notable disparity in the eddies’ characteristics was observed in both nIOD and pIOD and compared to normal years. In pIOD or nIOD, the number of eddies enhanced but their average lifespan reduced in the BoB. The increase in eddies was higher (38%) in nIOD than pIOD (11.2%) when compared to normal (non-IOD) years. The contribution of eddies to the total eddy kinetic energy (EKE) of the BoB increased from about 10% in normal years to about 25% in either of the IOD phases. The largest influence of IOD is seen at the thermocline depth. Within the BoB, the Andaman Sea region experienced the largest variations in eddies during IOD years.
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Authors and Affiliations

Navin Chandra
1 2
Vimlesh Pant
1

  1. Centre for Atmospheric Sciences, Indian Institute of Technology Delhi, New Delhi, India
  2. National Centre for Medium Range Weather Forecasting, Ministry of Earth Sciences, Noida, India
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Abstract

The main drivers of coastal processes, such as wave activity, variations in the water level, ice cover, and wind drift, may act differently in different segments of marginal seas with complex shapes. We analyse how the relative role of these drivers on the evolution of sedimentary shores changes along the southern and eastern Baltic Sea. While changes in the average water level have a strong impact along the southern shores of the Baltic Sea, rapid increases in the water level extremes affect most of the eastern subbasins of the Gulf of Finland and Gulf of Riga. The presence of a two-peak structure of predominant winds creates a fragile balance of alongshore sediment transport on the northeastern part of the Baltic proper and the Gulf of Riga. This balance could be changed by a rotation of predominant wave directions by a few degrees. Severe waves usually occur on the southern shores of the sea during water levels that are close to the long-term mean, while synchronisation of strong waves and high-water level is common on the eastern shore. The presence of sea ice is uncommon and insignificantly damps coastal processes in the southern part of the sea but the frequent presence of ice cover and freezing temperatures during the windy season stabilise the beaches of the north-eastern shores. Climate driven changes in ice cover duration may lead to erosion of many beaches in this part of the sea. The core message is that the impact of a single manifestation of climate change may vary greatly in different parts of the Baltic Sea and the reaction of coastal processes to this impact is substantially site-specific.
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Authors and Affiliations

Maris Eelsalu
1
Tarmo Soomere
1 2
Kevin Parnell
3
Maija Viška
4

  1. Department of Cybernetics, School of Science, Tallinn University of Technology, Ehitajate tee 5, 12618 Tallinn, Estonia
  2. Estonian Academy of Sciences, Kohtu 6, 10130 Tallinn, Estonia
  3. Department of Cybernetics, School of Science, Tallinn University of Technology, Ehitajate tee 5, 12618 Tallinn, Estonia2 Estonian
  4. Latvian Institute of Aquatic Ecology, Riga, Latvia
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Abstract

Researching the dynamic environment of the Baltic Sea requires an interdisciplinary approach, with numerical models and computer simulations becoming essential tools. The 3D CEMBS-PolSEA ecosystem model, developed at the Institute of Oceanology of the Polish Academy of Sciences, aims to determine the basic hydrodynamic parameters of the southern Baltic Sea. The CSI-POM service (Digital Information System on the Environment of Polish Marine Areas) consists of new tools for studying the structures, dynamics, and variability of physical processes in the southern Baltic. The service includes tools for determining the thermocline, halocline, and pycnocline, conducting spatio-temporal analysis of water column structure, automatic detection of vortices, testing water mass inertia under forecasted wind forces, and automatic detection of upwelling currents. The novelty of this work lies in the development of tools for studying the dynamics of the structure and variability of physical processes in the southern Baltic Sea. These innovative techniques support scientists, the maritime community, and regulatory bodies by providing detailed insights into local phenomena such as vortex formation, water mixing. The tools are implemented on the project server and the Tryton+ supercomputer, enabling high temporal and spatial resolution results. The CSI-POM system’s operational mode ensures access to the latest model results, with real-time and forecasted data. This enhances understanding and forecasting capabilities, informing about the current state of the environment and potential threats in the open sea.
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Authors and Affiliations

Lidia Dzierzbicka-Głowacka
1
Dawid Dybowski
1
Maciej Janecki
1
Artur Nowicki
1

  1. Institute of Oceanology, Polish Academy of Sciences, Powstańców Warszawy 55, 81–712 Sopot, Poland
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Abstract

This study presents the development and validation of a high-resolution 3D hydrodynamic model, CEMBS-PolSea, designed to resolve submesoscale features in Polish Marine Areas. The model, derived from the Community Earth System Model (CESM), employs a horizontal resolution of 575 m and 66 vertical layers. It incorporates advanced parameterizations for horizontal and vertical mixing processes, and integrates meteorological and river inflow data. A novel satellite data assimilation module was implemented to enhance model accuracy. The model was calibrated and validated using in situ measurements from the International Council for the Exploration of the Sea (ICES) database and satellite observations over the period 2019–2023. Results demonstrate strong agreement between model outputs and observational data, particularly for surface temperature (Pearson’s r = 0.95) and salinity (r = 0.89). The model successfully captures temporal and spatial variations in temperature and salinity profiles, with some discrepancies noted in deeper layers. The integration of satellite data assimilation significantly improved model performance, particularly in surface temperature predictions. This high-resolution model represents a significant advancement in simulating complex coastal dynamics and submesoscale features in the Polish Marine Areas, offering a valuable tool for marine ecosystem management and climate change impact studies in the region.
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Authors and Affiliations

Dawid Dybowski
1
Maciej Janecki
1
Artur Nowicki
1
Jaromir Jakacki
1
Lidia Dzierzbicka-Głowacka
1

  1. Institute of Oceanology, Polish Academy of Sciences, Powstańców Warszawy 55, 81–712 Sopot, Poland
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Abstract

Statistical properties of the air-sea flux of CO2 are estimated based on mean wind speed statistics. This is achieved by applying the same eight wind speed-dependent transfer velocity parameterizations of CO2 as used by Woolf et al. (2019) together with mean wind speed statistics from one location in the North Sea and one in the North Atlantic. These results demonstrate solely the contribution of the statistical uncertainties in terms of large standard deviations of the wind speed-dependent gas transfer velocity of the CO2 flux at both locations.
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Authors and Affiliations

Dag Myrhaug
1

  1. Department of Marine Technology, Norwegian University of Science and Technology (NTNU), Otto Nielsens vei 10,NO–7491 Trondheim, Norway
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Abstract

Research on the parasitology of the shorthorn sculpin (Myoxocephalus scorpius) from the Baltic Sea is presently limited. As a predatory fish, the species primarily acquire nematode parasites through the ingestion of infected prey. The main objectives of the current study were to (1) evaluate the presence of nematodes in the livers of shorthorn sculpin from the southern Baltic Sea and (2) investigate the dietary composition of this species. Accordingly, 32 fish from the north-western Polish waters of the Baltic Sea (ICES rectangle 39G6) were caught in November 2020 and subjected to standard ichthyological analyses. Moreover, liver samples were dissected from each fish and frozen for further parasitological investigation. The presence of the parasites was detected in 5 of the 32 analyzed livers, with a prevalence of 15.6%, intensity of infection from 2 to 99 parasites per fish and abundance of 3.9. Co-occurrence of Contracaecum sp. and Hysterothylacium sp. nematodes was observed in all infected fish. Stomach content analysis revealed that Crangon crangon, Bylgides sarsi and Gammarus spp. were the most abundant components of the shorthorn sculpin’s diet.
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Authors and Affiliations

Katarzyna Nadolna-Ałtyn
1
Joanna Pawlak
1
Marcin Kuciński
2

  1. National Marine Fisheries Research Institute, Kołłątaja 1, 81–332, Gdynia, Poland
  2. University of Gdańsk, Marszałka Piłsudskiego 46 Av., 81–378 Gdynia, Poland
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Abstract

Sundarbans Estuarine System is a highly productive estuary and is considered the most important spawning and nursery ground for various commercial fish and shellfish species. Estuarine organisms are frequently exposed to a wide variety of pollutants due to their vicinity to human habitation. Marine organisms residing in this area are also exposed to extensive fluctuations of environmental factors which vary with season. In the present study, effects of seasonal variation on oxidative stress biomarkers such as superoxide dismutase, catalase, glutathione-S-transferase, and lipid peroxidation in the hepatopancreas of mud crab Scylla serrata and shrimp Penaeus monodon, were studied during monsoon, winter, spring and summer seasons. The integrated biomarker response (IBR) was assessed with the biomarker scores for all four seasons in both species. Our results suggested seasonal discrepancies as the governing factor behind biomarkers’ variability. The breeding period of the animals also seems to play a significant role in their oxidative stress physiology. The IBR results indicated that moderately high temperatures and low salinity in the monsoon season are the most stressful for crabs. This stress might also be ascribed to the breeding period of these crabs which exacerbates the stress level during this season. However, in the case of shrimps, the highest IBR value was observed in the winter season due to impaired ROS elimination at low temperatures. This study also offers baseline values in various seasons that would be beneficial to be considered in environmental monitoring programs to avoid the misinterpretation of environmental factors, which change seasonally.
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Authors and Affiliations

Sritama Baag
1
Sumit Mandal
2

  1. Marine Ecology Laboratory, Department of Life Sciences, Presidency University, 86/1, College Street, Kolkata – 700073, India
  2. Marine Ecology Laboratory, Department of Life Sciences, Presidency University, 86/1, College Street, Kolkata – 700073, India.
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Abstract

This study addresses the pressing issue of black carbon (BC) pollution in urban areas, focusing on two locations in the Philippines: Quezon City’s East Avenue (QCG, roadside urban environment) and Manila’s North Port. We found that organic aerosol particles (OA) made a greater contribution (80%) to total submicron particulate matter compared to inorganic aerosol (IA) (20%). The mean hourly average equivalent black carbon (eBC) mass concentration at the QCG site (35.97 ± 16.20 ��g/m3) was noticeably higher compared to the Port (10.27 ± 5.99 ��g/m3), consistent with trends in other Asian cities. Source apportionment analysis identified eBC related to transport emissions (eBCTR) as the predominant contributor to eBC, accounting for 86% at the Port and 80% at QCG. Diurnal patterns showed the highest eBCTR mass concentrations (47.69 ± 9.34 ��g/m3) during morning rush hours, which can be linked to light-duty vehicles. Late-night (10 pm–12 am) high concentrations (30.63 ± 8.45 ��g/m3) can be associated with heavy diesel trucks at the QCG site. Whereas at the Port site, hourly average higher eBCTR concentration (12.24 ± 3.65 ��g/m3) during morning hours (6 am–8 am) can be attributed to the traffic of heavy-duty trucks, trollers, diesel-powered cranes and ships. Compared to the QCG site, a lower eBC concentration at the Port site was favoured by the more open environment and higher wind speed, facilitating better pollutant dispersion. The mean hourly average concentrations of PM2.5 and PM10, measured using an Aerodynamic Particle Sizer, consistently exceeded the air quality standards set by the World Health Organization and the Philippine Clean Air Act at both sites. This study highlights the persisting BC pollution in developing regions and calls for scientifically based strategies to mitigate the air quality crisis.
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Authors and Affiliations

Touqeer Gill
1
Simonas Kecorius
1 2
Kamilė Kandrotaitė
1
Vadimas Dudoitis
1
Leizel Madueño
3
Alfred Wiedensohler
3
Laurent Poulain
3
Edgar A. Vallar
4
Maria Cecilia D. Galvez
4
Steigvilė Byčenkienė
1
Kristina Plauškaitė
1

  1. Center for Physical Sciences and Technology (FTMC), Saulėtekio av. 3, LT-10257 Vilnius, Lithuania
  2. Institute of Epidemiology, Helmholtz Zentrum München, Ingolstädter Landstr. 1, 85764 Neuherberg, Germany
  3. Leibniz-Institute for Tropospheric Research, Permoserstrasse 15, 04318 Leipzig, Germany
  4. ARCHERS, CENSER, De La Salle University, 2401 Taft Ave., Malate, Philippines
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Abstract

Phytoplankton pigments were used to study the community structure and phytoplankton size class in Goa’s estuaries. The study revealed that fucoxanthin and chlorophyll a were the most dominant pigments. The correlation of diagnostic pigments (DP) and chl a correlated positively in both estuaries (Mandovi: R2 = 0.703, P < 0.01; Zuari: R2 = 0.892, P < 0.01), suggesting that DP can serve as a proxy to measure phytoplankton biomass. Results showed that with DP and biomass proportion, phytoplankton size class (picoplankton, nanoplankton and microplankton) can be derived. Picoplankton biomass was highest during pre-monsoon season, while microplankton biomass was high during monsoon season. The high abundance of microplankton may support planktivorous fishery productivity.
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Authors and Affiliations

Reshmitha Ramakrishnan
1 2
Keisham Sarjit Singh
1
Temjensangba Imchen
1

  1. CSIR – National Institute of Oceanography, Dona Paula–403004, Goa, India
  2. Department of Marine Science, Bharathidasan University, Tiruchirappalli–620024, Tamil Nadu, India
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Abstract

The northern Arabian Sea, a vital ecosystem that sustains a significant population through its fisheries is increasingly threatened by climate change, overharvest, and coastal pollution. To evaluate the combined effects of these pressures on fishery health, microplankton, fish bycatch, and coastal environment data were examined between 2019 and 2023 from key hotspots. Using the time-cumulated indicator (TCI) and efficiency cumulated indicator (ECI) approaches, we aimed to determine broader spectrum of energy flow in the ecosystem. The findings revealed a delicate equilibrium in the ecosystem. Although average temperatures remained stable, variations in rainfall patterns suggested potential changes in salinity and dissolved oxygen levels, signaling subtle climate change influences. Biological indicators highlighted dynamic shifts: species diversity fluctuated, suggesting community restructuring, while increased evenness implied potential ecological stabilization. The production and biomass (P/B) ratio was higher in 2019, reflecting faster biomass production compared to the slower rate observed in 2023. This instability may be attributed to environmental changes, altered species composition, and a steady increase in fishing pressure. Notably, consistent fish catches amidst relatively stable species diversity suggest complex population dynamics. In terms of energy flow and transformation, a significant rise in TCI, suggests accelerated energy transfer, likely driven by a decline in predator population. Additionally, the instability in Residence Time (RT) underscores intricate food web interactions. Our findings highlight the delicate equilibrium of the northern Arabian Sea, as revealed by the overall data and assessment. Understanding these intricate dynamics is crucial for developing effective conservation strategies and promoting sustainable fishing practices.
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Authors and Affiliations

Imtiaz Kashani
1
Sher Khan Panhwar
1
Kishwar Kumar Kachhi
1

  1. Centre of Excellence in Marine Biology, University of Karachi, 75270, Sindh, Pakistan

Instructions for authors

INTRODUCTION

Criteria for manuscripts

The Editorial Board of Oceanologia takes under consideration for publication original articles with the understanding that neither the manuscript nor any part of its essential substance, tables or figures have been published previously in print form or electronically and are not under consideration by any other publication or electronic medium. Copies of any closely related manuscripts should be submitted to the Editor along with the manuscript that is to be considered by Oceanologia. Each submission packet should include the statement signed by the first author that the work has not been published previously or submitted elsewhere for review and a copyright transfer.

The journal Oceanologia publishes original papers on fundamental aspects of marine research with the emphasis on northern European seas. Papers dealing with processes in the marine environment are preferred to purely descriptive ones; they should contribute to the understanding of the functioning of marine ecosystems, including their abiotic aspects. Please note that purely descriptive articles/ papers do not meet the aims of Oceanologia. All scripts received will be reviewed by the editors and at least two independent experts. The scripts should be written in good, scientific English: American or British. Every effort will be made to expedite publication.

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For papers exceeding 20 pages, an excess-page charge per printed page will be made: 50 EUR net for pages 21 et seq. The author(s) will be informed whether or not his/her/their paper has been accepted for printing and will be billed for the excess-page charge (if any).

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