Oceanologia No. 62 (3) / 20


Original research article

Short communication

Letter to the editor

Letter to the editor - response

Original research article

Inhomogeneity detection in phytoplankton time series using multivariate analyses
Oceanologia 2020, 62(3), 243-254

Oihane Muñiz1,*, José Germán Rodríguez1,*, Marta Revilla1,*, Aitor Laza-Martínez2,3,*, Sergio Seoane2,3,*, Javier Franco1,*
1AZTI, Marine Research Division, Pasaia, Spain;
e-mail: omuniz@azti.es, oihanemp@hotmail.com,
e-mail: grodriguez@azti.es, mrevilla@azti.es, jafranco@azti.es
2Department of Plant Biology and Ecology, Faculty of Science and Technology, University of the Basque Country, UPV/EHU, Leioa Spain,
3Technology and Research Centre for Experimental Marine Biology and Biotechnology (PiE-UPV/EHU), 48620 Plentzia, Spain;
e-mail: aitor.laza@ehu.eus, sergio.seoane@ehu.es
*corresponding author

keywords: Phytoplankton assemblages, Fixative, Variability, Uncertainty, Taxonomist, Long-term series

Received 17 July 2019, Revised 27 January 2020, Accepted 30 January 2020, Available online 12 February 2020.


Phytoplankton communities have long been used as water quality indicators within environmental policies. This has fostered the development of national and international phytoplankton monitoring programs, but these networks are subject to sources of uncertainty due to laboratory issues. Nevertheless, studies regarding the interference associated with these aspects are not well-documented. Hence, a long time series (2003–2015) from the Basque continental shelf (southeastern Bay of Biscay) was analyzed to evaluate the uncertainty given by laboratory strategies when studying phytoplankton variability. Variability in phytoplankton communities was explained not only by environmental conditions but also by changes in fixatives (glutaraldehyde and acidic Lugol's solution) and laboratory staff. Based on Bray-Curtis distances, phytoplankton assemblages were found to be significantly dissimilar according to the effect of changes in the specialist handling the sample and the employed fixative. The pair-wise permutational multivariate analysis of variance (PERMANOVA) showed significant differences between the two fixatives utilized and also between the three taxonomists involved. Thus, laboratory-related effects should be considered in the study of phytoplankton time series.
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Imprints of atmospheric waves on the Black Sea surface in data of ocean color scanners
Oceanologia 2020, 62(3), 255-266

Marina A. Evdoshenko
P.P. Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia;
e-mail: maarsio@bk.ru

keywords: Remote sensing, Ocean Optics, Atmospheric gravity waves, Black Sea

Received 16 August 2019, Revised 25 January 2020, Accepted 28 January 2020, Available online 12 February 2020.


Data from MERIS onboard Envisat and MODIS onboard Terra and Aqua for 15–16 May 2010 were used to study powerful imprints of atmospheric gravity waves (AGWs) on the western part the Black Sea surface. Two cold fronts crossed the sea following the warm front and caused the AGWs which modulated the sea surface. Imprints of AGWs appeared as stripes of alternating brightness, they had crest length more than a hundred kilometers and wavelength of units of kilometers. Wave amplitude of AGWs imprints, evaluated by a 90%-depth of light penetration into the sea at 490 nm z90, the value inverse to the diffuse attenuation coefficient Kd_490, was units of decimeterxs. MODIS 250-m data of remote sensing reflectance, wind components and atmospheric pressure near the sea surface were obtained by processing the top of atmosphere data with the SeaDAS software package. Negative correlations of fluctuations of z90 with fluctuations of wind stress and atmospheric pressure were found on the transects of more than ten kilometers. The impact of wind stress on the origination of AGW imprints was found to be determinant, while the impact of atmospheric pressure was not more than units of percent.
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Investigating the Role of Atmospheric Variables on Sea Level Variations in the Eastern Central Red Sea Using an Artificial Neural Network Approach
Oceanologia 2020, 62(3), 267-290

Khalid M.Zubier1,*, Lina S. Eyouni1,2
1Marine Physics Department, Faculty of Marine Sciences, King Abdulaziz University, Jeddah, Saudi Arabia;
e-mail: kzubier@kau.edu.sa
2Red Sea Research Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
*corresponding author

keywords: Red Sea, Atmospheric Variables, Sea Level Anomaly, Artificial Neural Network (ANN), Non-linear Auto-Regressive Network with eXogenous inputs (NARX)

Received 21 July 2019, Revised 30 November 2019, Accepted 9 February 2020, Available online 24 February 2020.


Atmospheric variables play a major role in sea level variations in the eastern central Red Sea, where the role of tides is limited to 20% or less. Extensive analysis of daily-averaged residual sea level and atmospheric variables (atmospheric pressure, air temperature, wind stress components, and evaporation rate) indicated that sea level variations in the eastern central Red Sea are mainly contributed to by the seasonal and weather-band variations in the utilized atmospheric variables. The Non-linear Auto-Regressive Network with eXogenous inputs (NARX), a type of Artificial Neural Network (ANN), was applied to investigate the role of the atmospheric variables on the sea level variations at the eastern central Red Sea. Forced by time-delayed daily-averaged observations of atmospheric variables and residual sea level, the constructed NARX-based model showed high performance in predicting the one-step-ahead residual sea level. The high performance indicated that the constructed model was able to efficiently recognize the role played by the atmospheric variables on the residual sea level variations. Further investigations, using the constructed NARX-based model, revealed the seasonal variation in the role of the atmospheric variables. The study also revealed that the role played by some of the atmospheric variables, on sea level variations, could be masked by the role of one or more of the other atmospheric variables. The obtained results clearly demonstrated that this neurocomputing (NARX) approach is effective in investigating the individual and combined role of the atmospheric variables on residual sea level variations.
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Rip currents in the non-tidal surf zone with sandbars: numerical analysis versus field measurements
Oceanologia 2020, 62(3), 291-308

Aleksandra Dudkowska1,*, Aleksandra Boruń1, Jakub Malicki2, Jan Schönhofer2, Gabriela Gic-Grusza1
1University of Gdańsk, Institute of Oceanography, Gdynia, Poland;
e-mail: aleksandra.dudkowska@ug.edu.pl
2Institute of Hydro-Engineering, Polish Academy of Sciences, Gdańsk, Poland
*corresponding author

keywords: Rip current, Coastal zone, Coastal flows, Wind-wave conditions

Received 14 August 2019, Revised 3 February 2020, Accepted 7 February 2020, Available online 22 February 2020.


Rip currents, which are local seaward-directed jets with their mean velocity exceeding 0.5 m/s, have been a subject of many studies since the 1940s. They are an important part of the nearshore current system and in specific hydro- and litomorphological conditions can cause changes in the local bathymetry. Thus, a detailed analysis of the characteristics of this phenomenon is crucial both to public safety and hydroengineering. The main purpose of this research is to determine the wave conditions of a multi-bar non-tidal coastal zone environment in which rip currents can occur. In this study, we focus on a multi-bar non-tidal coastal zone environment located in the Southern Baltic Sea, where rip current driving forces are mostly reduced to the wind and wind-induced waves. This is one of very few comprehensive approaches to exploring the possibility of rip currents occurrence in such environmental conditions. During two field expeditions, there were carried out in situ measurements exploiting two GPS drifters. The results indicate the formation of irregular non-longshore flows (related to rip currents) in the studied area. To answer the question under what conditions the formation of rip currents takes place, an extended modelling experiment was performed. Deep-water wave conditions typical of the studied area were chosen due to bouy measurements. The total of 589 combinations of the significant wave height, the mean period and wave direction values were examined as test cases. The coastal flow in the area and tracks of virtual drifters were simulated by XBeach numerical model for all test cases. As a result, 589 nearshore currents fields were generated and two scenarios were indicated: a regular circulation (dominated by the longshore current) which is typical of this area (547 cases), and flows with rip current features (42 cases). This reflects the results of the field measurements carried out. It can be concluded that the wave direction is a dominating factor in the formation of rip currents. Namely the flows of this type may occur in the area of interest when the direction of a deep water wave is almost perpendicular to the shore. Such situations occur rarely. They cover about 7% of the days of the year. Thus, rip currents do not appear to be a significant factor in the reconstruction of the sea bottom in the studied area.
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The demand analysis of oceanic T-S-V 3D reconstruction on wide-swath SSH data features based on ROMS and 4DVAR
Oceanologia 2020, 62(3), 309-325

Chaojie Zhou1,*, Jie Zhang1,2, Jungang Yang2, Lei Cao3
1China University of Petroleum, College of Oceanography and Space Informatics, Qingdao, China;
e-mail: hitzcj@163.com
2First Institute of Oceanography, Ministry of Natural Resources, Qingdao, China
3Beijing Research Institute of Telemetry, Beijing, China
*corresponding author

keywords: 3D Ocean state estimation, Wide-swath altimeter, Accuracy, Spatial-temporal resolution

Received 13 June 2019, Revised 24 February 2020, Accepted 27 February 2020, Available online 13 March 2020.


Future wide-swath altimetry missions will provide high-resolution information about ocean surface elevation, and facilitate the characterization of meso- and sub-mesoscale ocean activities. In this study, the demand analysis of three-dimensional (3D) oceanic state reconstruction on wide-swath SSH data features was evaluated using a data assimilation strategy. Three groups of experiments were performed to determine if the wide-swath altimetry observations would improve the three-dimensional (3D) field estimates of ocean temperature-salinity-velocity (T-S-V), and to evaluate how the spatial and temporal resolution and accuracy of the wide-swath altimetry observations affected the ocean state estimation. The Regional Ocean Modeling System and the four-dimensional variational data assimilation method were used in the experiments, with numerical simulation for the Taiwan region at a resolution of 1/10° as the example. The sensitivity of the 3D ocean state construction to the wide-swath altimetry measurements was also investigated. The results showed that the wide-swath sea surface height (SSH) measurements would have an overall positive impact on the 3D T-S-V field and that the positive effect would increase as the resolution and accuracy of the observations increased, but the net benefits would gradually decrease. Among the three examined features of the wide-swath altimetry observations, the temporal resolution had the most influence on the 3D ocean state analysis.
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Unravelling the spatio-temporal variation of zooplankton community from the river Matla in the Sundarbans Estuarine System, India
Oceanologia 2020, 62(3), 326-346

Tanmoy Nandy, Sumit Mandal*
Marine Ecology Laboratory, Department of Life Sciences, Presidency University, Kolkata, India;
e-mail: sumit.dbs@presiuniv.ac.in
*corresponding author

keywords: Sundarbans, Zooplankton, Copepoda, Bioindicator, Seasonal succession

Received 20 December 2019, Revised 17 March 2020, Accepted 19 March 2020, Available online 7 May 2020.


Zooplankton is an important bioindicator of ecosystem functioning. Knowledge of the seasonal fluctuation in the zooplankton population in estuarine waters of the Indian Sundarbans is rather limited. In the present study, we analysed the community structure of zooplankton assemblages and their spatio-temporal variations based on different multivariate statistics and indicator value analysis. A total of 56 taxa were identified and the density was primarily dominated by planktonic copepods and few meroplankton communities during four sampling seasons. The most abundant species were: Acartia spinicauda, Acartia sp., Bestiolina similis, Euterpina acutifrons, Labidocera acuta, Paracalanus aculeatus, Paracalanus parvus and Paracalanus indicus. Canonical Correspondence Analysis highlighted that temperature, pH, DO, salinity and nutrients were the prevailing environmental parameters associated with significant spatio-temporal changes of zooplankton distribution in this area. The highest abundance of zooplankton was recorded in winter, followed by monsoon, summer and spring. Throughout the study period, different zooplankton indices were observed in good condition. Seasonal occurrence of dominant zooplankton with high IndVal index was markedly observed and it might be used as a potential bioindicator for a particular season and environmental condition in this estuarine complex. The results of this study provide evidence for the presence of warm water species in the estuarine waters of the Indian Sundarbans and can be a clear indication of climate change-mediated elevated temperature in the estuarine system. Our results underscore the high diversity of zooplankton from mangrove dominated estuarine complex and emphasize the need for long-term monitoring in ecologically fragile ecosystems like the Sundarbans Estuarine System.
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Measurements of light transfer through drift ice and landfast ice in the northern Baltic Sea
Oceanologia 2020, 62(3), 347-363

Elina Kari1,4,*, Arttu Jutila2,5, Anna Friedrichs3, Matti Leppäranta2, Susanne Kratzer1
1Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden;
e-mail: elina.kari@helsinki.fi
2Institute for Atmospheric and Earth System Research (INAR), University of Helsinki, Helsinki, Finland
3Institute for Chemistry and Biology for the Marine Environment, Carl von Ossietzky University of Oldenburg, Oldenburg, Germany
4Present: Institute for Atmospheric and Earth System Research (INAR), P.O. Box 64, 00014 University of Helsinki, Finland
5Present: Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Am Handelshafen 12, 27570 Bremerhaven, Germany
*corresponding author

keywords: Light transfer, Sea ice, Diffuse attenuation coefficient, Coloured dissolved organic matter, Scattering

Received 29 November 2019, Revised 1 April 2020, Accepted 2 April 2020, Available online 20 May 2020.


The aim of this study was to investigate the light transfer through sea ice with a focus on bio-optical substances both in fast ice and in the drift ice zones in the northern Baltic Sea. The measurements included snow and ice structure, spectral irradiance and photosynthetically active radiation below the sea ice. We also measured the concentrations of the three main bio-optical substances which are chlorophyll-a, suspended particulate matter, and coloured dissolved organic matter (CDOM). These bio-optical substances were determined for melted ice samples and for the underlying sea water. The present study provides the first spectral light transfer data set for drift ice in the Baltic Sea. We found high CDOM absorption values typical to the Baltic Sea waters also within sea ice. Our results showed that the transmittance through bare ice was lower for the coastal fast ice than for the drift ice sites. Bio-optical substances, in particular CDOM, modified the spectral distribution of light penetrating through the ice cover. Differences in crystal structure and the amount of gas inclusions in the ice caused variation in the light transfer. Snow cover on ice was found to be the dominant factor influencing the light field under ice, confirming previous studies. In conclusion, snow cover dominated the amount of light under the ice, but did not modify its spectral composition. CDOM in the ice absorbs strongly in the short wavelengths. As pure water absorbs most in the long wavelengths, the light transfer through ice was highest in the green (549–585 nm).
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Surface desalinated layer distribution in the Kara Sea determined by shipboard and satellite data
Oceanologia 2020, 62(3), 364-373

Dmitry I. Glukhovets1,2,*, Yury A. Goldin1
1Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia;
e-mail: glukhovets@ocean.ru
2Moscow Institute of Physics and Technology, Dolgoprudny, Moscow region, Russia
*corresponding author

keywords: Surface desalinated layer, Interseasonal dynamics, Satellite data, Kara Sea, Fluorescence, Absorption

Received 30 November 2019, Revised 7 April 2020, Accepted 8 April 2020, Available online 20 May 2020.


This study reports the propagation dynamics of the Kara Sea surface desalinated layer (SDL) during the summer and autumn seasons. We analysed shipboard measurements data collected in 2013–2018 and MODIS ocean colour data that correlated with the shipboard ones. We formulated a comparatively strict criterion to determine the SDL border based on satellite data. For that, we analyzed the shipboard flow-through measuring system data obtained while crossing the surface desalinated layer border. Further, we used a regional algorithm to process the satellite data and estimate the coloured dissolved organic matter absorption coefficient for the Kara Sea. The results demonstrate a significant effect of the wind regime on the interseasonal and interannual variability of the transformation of the SDL boundaries. The positions of the surface desalinated layer boundaries at different times during 2013–2018 are given. The obtained results are important for calculating the heat balance and analyzing the Kara Sea bio-productivity.
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Limitation of lignin derivatives as biomarkers of land derived organic matter in the coastal marine sediments
Oceanologia 2020, 62(3), 374-386

Janusz Pempkowiak
Marine Chemistry Department, Institute of Oceanology, Polish Academy of Sciences, Sopot, Poland;
e-mail: pempa@iopan.gda.pl

keywords: Lignin phenols, Stable carbon isotopes, δ13C, End members, Nonlinear analyses, Gdańsk Bay, Southern Baltic

Received 5 April 2020, Revised 17 April 2020, Accepted 21 April 2020, Available online 20 May 2020.


Lignin oxidation products (vanillyl, syringil and cummaryl phenols), and δ13C were measured in a variety of land and marine samples collected in Inner Puck Bay – dominated by marine vascular plants, small river run-off, and shallow bottom, and in Gdańsk Bay – characterized by large river run-off, small marine vascular plants population, and the average depth exceeding euphotic zone. Both study areas are parts of the Gdańsk Basin, Southern Baltic.

Typical δ13C values (δ13C = -28‰) and both composition and concentrations of lignin phenols were measured in samples originating from land. Small, yet easily measurable amounts of lignin phenols were found in marine vascular plants biomass (Σ8 = 90 µg/100 mg organic matter). The biomass was characterized by exceptionally high δ13C values (-12‰). No lignin phenols and typical δ13C values (-22‰) were measured in marine phytoplankton biomass. δ13C and both composition and content of lignin phenols in organic matter of surface sediments collected in the study area fall in the range marked by the end members.

The proportion of land derived organic matter calculated using lignin phenols, or δ13C in Gdańsk Bay were comparable, while in Puck Bay they differed substantially. It was concluded that a) in areas with substantial bottom coverage with vascular plants the two end members approach, usually employed to establish the contribution of organic matter sources, is insufficient, b) organic matter originating from three sources: riverine, phytoplankton, and vascular plants contribute to sedimentary organic matter in Puck Bay with the respective proportion 30:40:30.

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Characteristics of the grey seal (Halichoerus grypus) diet in the Vistula River mouth (Mewia Łacha Nature Reserve, southern Baltic Sea), based on the osteological and molecular studies of scat samples
Oceanologia 2020, 62(3), 387-394

Sławomir Keszka1, Remigiusz Panicz2,*, Katarzyna Stepanowska1, Marcin Biernaczyk1, Konrad Wrzecionkowski3, Mikołaj Zybał1,4
1Department of Aquatic Bioengineering and Aquaculture, Faculty of Food Science and Fisheries, West Pomeranian University of Technology, Szczecin, Poland
2Department of Meat Sciences, Faculty of Food Science and Fisheries, West Pomeranian University of Technology, Szczecin, Poland;
e-mail: rpanicz@zut.edu.pl
3Wolin National Park, Międzyzdroje, Poland
4Laureate of the Duke/Oak Foundation 2013 Mini-grants in Marine Conservation, Marine Laboratory, Nicholas School of Environment, Duke University, Beaufort, N.C., USA
*corresponding author

keywords: Diet of marine mammals, DNA barcoding, Fish species identification, Lampetra fluviatilis, Grey seal (Halichoreus grypus)

Received 17 December 2019, Revised 14 April 2020, Accepted 17 April 2020, Available online 21 May 2020.


The study analyses for the first time the diet composition of grey seals inhabiting the Polish Baltic Sea coast. Samples of seal scat were collected in the Mewia Łacha Nature Reserve at the mouth of the Vistula River. Using genetic and osteological methods, the remains of organisms included in the grey seals diet were analysed for their taxonomy (families and species). Based on the analysis of 49 scat samples from grey seals, 761 hard parts that could be identified by taxon were isolated. The predominant species in the samples were perch, Perca fluviatilis (almost 78% of samples); pikeperch, Sander lucioperca (67%); lamprey, Lampetra fluviatilis (almost 35% of samples); Baltic cod, Gadus morhua callarias (almost 31% of samples) and sea trout, Salmo trutta trutta (26.5%). Genetic analysis confirmed the presence of Atlantic cod DNA in 69% and sea trout in 63% of samples. The genetic material of the Atlantic herring, Clupea harengus has not been identified in the analysed scat samples. Information on grey seals feeding on river lampreys seems to be valuable in the context of lack of knowledge on the occurrence of lampreys in the Vistula River. The methodology used showed that seals fed on species that were the most abundant in the area which is directly associated with the migration cycle of fish. The results of our study allowed the conclusion that the grey seal is an opportunistic predator and its diet reflects and exploits the variations in its habitat.
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Short communications

Some probabilistic properties of surf parameter
Oceanologia 2020, 62(3), 395-401

Dag Myrhaug
Department of Marine Technology, Norwegian University of Science and Technology (NTNU), Trondheim, Norway;
e-mail: dag.myrhaug@ntnu.no

keywords: Surf parameter, Spectral surf parameter, Phillips spectrum, JONSWAP spectrum, Joint frequency tables, Wave runup, Wave statistics

Received 26 August 2019, Revised 13 February 2020, Accepted 13 February 2020, Available online 28 February 2020.


This article is supplementary to Myrhaug (2018) and presents some probabilistic properties of the surf parameter for individual waves and the spectral surf parameter for sea states by using distributions based on data from the Norwegian continental shelf. The average statistical features given by the mean value and the standard deviation of the two surf parameters are considered. Examples of results for the surf parameter are provided for a Phillips spectrum and a family of JONSWAP spectra for wind sea, and for sea states using a joint frequency table of significant wave height and mean zero-crossing wave period for combined wind sea and swell. The spectral surf parameter results are obtained by using a joint distribution of significant wave height and spectral surf parameter, and the mean statistical properties are given for joint frequency tables of significant wave height and mean zero-crossing wave period from three deep water locations on the Norwegian continental shelf. It is also demonstrated how the results can be applied to calculate the vertical wave runup elevation for breaking waves.
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Low-active high-density Noctiluca scintillans cells in surface seawater
Oceanologia 2020, 62(3), 402-407

Kuninao Tada1,2,*, Toshimasa Asahi1, Saho Kitatsuji1,3, Mika Nomura1,, Hitomi Yamaguchi1, Kazuhiko Ichimi4
1Faculty of Agriculture, Kagawa University, Ikenobe, Japan;
e-mail: tada@ag.kagawa-u.ac.jp
2Seto Inland Sea Regional Research Center, Kagawa University, Saiwai-cho, Takamatsu, Kagawa, Japan
3National Research Institute of Fisheries and Environment of Inland Sea, Japan Fisheries Research and Education Agency, Maruishi, Hatsukaichi, Hiroshima, Japan
4Aji Marine Station, Seto Inland Sea Regional Research Center, Kagawa University, Kamano, Aji, Takamatsu, Kagawa, Japan
*corresponding author

keywords: Noctiluca scintillans, Heterotrophic dinoflagellate, Cell density, Coastal water, ATP, Activity

Received 10 November 2019, Revised 27 February 2020, Accepted 29 February 2020, Available online 13 March 2020.


Noctiluca scintillans is an important member of the mesozooplankton in terms of biomass and production in the Seto Inland Sea, Japan. The densities and adenosine triphosphate (ATP) contents of N. scintillans cells were measured. Vertical profiles of N. scintillans cellular activity in the coastal water were determined and the ATP contents were high at middle layers, with a maximum depth of 10 m. ATP contents were low in the surface and lower layers. These results suggest that active N. scintillans cells in subsurface layers with low density play an important role in the coastal ecosystem, and high-density cells in the surface water are not active.
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Comments on the article “Spatio-temporal variations in sulfur-oxidizing and sulfate-reducing bacterial activities during upwelling, off south-west coast of India”
Oceanologia 2020, 62(3), 408-410

Sudheesh Valliyodan
Centre for Marine Living Resources and Ecology, Ministry of Earth Sciences, Cochin 682508, India;
e-mail: sudhikeloth13@gmail.com

Received 20 December 2019, Accepted 29 December 2019, Available online 28 January 2020.
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Response to “Comments on the article 'Spatio-temporal variations in sulfur-oxidizing and sulfate-reducing bacterial activities during upwelling, off south-west coast of India'”
Oceanologia 2020, 62(3), 411

A. Sam Kamaleson1, Maria-Judith Gonsalves1,*, Swatantar Kumar2, V. K. Jineesh3, P. A. LokaBharathi1
1CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India;
e-mail: mjudith@nio.org
2Pacific Northwest National Laboratory, US Dept. of Energy, USA
3Academy of Climate Change, Education and Research, Agricultural University, Kerala, India
*corresponding author

Received 28 January 2020, Accepted 28 January 2020, Available online 21 February 2020.
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