Oceanologia No. 64 (4) / 22

Contents

Original research article

Short communication

Original research article


Coastal cliff erosion as a source of toxic, essential and nonessential metals in the marine environment
Oceanologia 2022, 64(4), 553-566
https://doi.org/10.1016/j.oceano.2022.04.001

Magdalena Bełdowska1, Jacek Bełdowski2, Urszula Kwasigroch1, Marta Szubska2, Agnieszka Jędruch2,*
1Institute of Oceanography, University of Gdańsk, Gdynia, Poland
2Institute of Oceanology, Polish Academy of Sciences, Sopot, Poland;
e-mail: ajedruch@iopan.pl
*corresponding author

keywords: Metals, Coastal erosion, Cliffs, Sediments, Baltic Sea

Received 27 December 2021, Revised 21 March 2022, Accepted 15 April 2022, Available online 4 May 2022, Version of Record 29 September 2022.

Abstract

Due to the rising environmental awareness, emissions and releases of pollutants, including metals, have been considerably reduced in the last decades. Therefore, the remobilization of natural and anthropogenic contaminants is gaining importance in their biogeochemical cycle. In the marine coastal zone, this process occurs during the erosion of a shore, especially the most vulnerable cliffs. The research was conducted in the Gulf of Gdańsk (southern Baltic Sea) from 2016 to 2017. The sediment cores were collected from four cliffs; additionally, marine surface sediments were also taken. The concentrations of essential (Cr, Mn, Fr, Cu, Zn) and nonessential (Rb, Sr, Y, Zr, Ba) metals were analyzed using the XRF technique. The levels of the analyzed metals were relatively low, typical of nonpolluted areas. However, considering the mass of eroded sediments, the annual load of metals introduced into the sea in this way is significant. In the case of Cu, Zn, and Y the load can amount to a few kilograms, for Cr and Rb – over ten kilograms, for Mn, Sr, and Zr – several tens of kilograms, for toxic Ba – over 100 kg, and in the case of Fe – 4.8 tonnes. During strong winds and storms, when the upper part of a cliff is eroded, especially the load of Zn and Cr entering the sea may increase. The content of Cr, Zr, and Ba in the cliffs was higher compared to marine sediments from the deep accumulation bottom, which indicates that coastal erosion may be an important source of these metals.
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Are fatty acids in fish the evidence of trophic links? A case study from the southern Baltic Vistula Lagoon
Oceanologia 2022, 64(4), 567-582
https://doi.org/10.1016/j.oceano.2022.04.002

Agnieszka Góra*, Joanna Szlinder-Richert, Ryszard Kornijów
National Marine Fisheries Research Institute, Gdynia, Poland;
e-mail: agora@mir.gdynia.pl
*corresponding author

keywords: Trophic marker, Feeding ecology, Ontogenetic shift, PUFA biosynthesis

Received 19 January 2022, Revised 15 April 2022, Accepted 15 April 2022, Available online 4 May 2022, Version of Record 29 September 2022.

Abstract

Most knowledge on the feeding ecology of fish has been based on the analyses of food remains from the alimentary tracks. This traditional method, however, only provides information about recently consumed food, and is burdened with a risk of incorrect assessment of the role of individual diet components due to the different rates of digestion. A method free from such limitations is the analysis of fatty acids. The objective of our study was to recognise the potential of fatty acid signatures in providing information on the diet and feeding habits of six fish species from the shallow brackish Vistula Lagoon, southern Baltic Sea (Anguilla anguilla, Abramis brama, Rutilus rutilus, Pelecus cultratus, Perca fluviatilis, Sander lucioperca). Multivariate statistical analyses of fatty acid signatures permitted relevant grouping of the fish according to species and their diet, as well as evidenced substantial ontogenetic changes in perch, roach, and bream. They might be caused by dietary changes but can also result from internal regulatory processes. The obtained results confirmed that fatty acids provide useful, time-integrated dietary information, contributing to expanding knowledge regarding the feeding ecology of fish in shallow coastal water ecosystems. They also pointed to the necessity of assessment of the invertebrates and fish's ability to perform endogenous synthesis of polyunsaturated fatty acids, particularly in research on benthic communities. To our best knowledge, this is the first attempt to investigate the feeding habits of fish and food-web relationships in the coastal waters of the Baltic Sea using fatty acids.
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Dynamics of absorption properties of CDOM and its composition in Likas estuary, North Borneo, Malaysia
Oceanologia 2022, 64(4), 583-594
https://doi.org/10.1016/j.oceano.2022.04.005

Saiyidah Munirah Mohd-Shazali1, Jafar-Sidik Madihah1,*, Nurzaliah Ali1, Chen Cheng-Ann1, Robert J.W. Brewin2, Md. Suffian Idris3, P. Purba Noir4
1Borneo Marine Research Institute, University of Malaysia of Sabah, Sabah, Malaysia;
e-mail: madihah@ums.edu.my
*corresponding author
2Centre for Geography and Environmental Science, College of Life and Environmental Sciences, University of Exeter, Penryn, Cornwall, United Kingdom
3Faculty of Science and Marine Environment, University of Malaysia Terengganu, Terengganu, Malaysia
4Marine Research Laboratory (MEAL), Faculty of Fishery and Marine Science, Padjadjaran University, Jatinangor, Indonesia

keywords: Coloured dissolved organic matter (CDOM), The absorption coefficient of CDOM (aCDOM), Molecular weight and degradation of CDOM, High molecular weight (HMW) CDOM, Low molecular weight (LMW) CDOM

Received 18 May 2021, Revised 9 April 2022, Accepted 15 April 2022, Available online 17 May 2022, Version of Record 29 September 2022.

Abstract

Chromophoric Dissolved Organic Matter (CDOM) is a vital water constituent in aquatic ecosystems that contributes to water colour, affects light penetration, and impacts primary production. This study aims to determine the spatial and monsoonal variability of CDOM absorption properties in the Likas estuary, characterise the source of CDOM, and investigate the correlations between CDOM absorption properties and salinity. Likas estuary is a small estuary located in Kota Kinabalu city on the west coast of Sabah, facing the South China Sea. A mangrove ecosystem surrounds it with manufactured structures such as residential areas and public facilities. Surface water samples were collected at 19 stations: upstream of rivers to the river mouth and coastal area during spring tides every month, from June 2018 to July 2019, for 14-months. The distribution of aCDOM(440) in the study area is predictable as a signature in a coastal area with a decreasing gradient from the upstream towards coastal water (0.29 ± 0.19 m−1 to 1.05 ± 0.39 m−1). There are increasing spatial patterns of spectral slopes S275-295 and SR. However, S350-400 and S300-600 declined spatial gradients from the upstream to coastal water. Thus, S300-600 indicates a linear relationship between aCDOM(440), which unconventional results in coastal water. We suspect this is due to a small coverage of the study site with a distance of 0.5 m intervals of each station. This could be why the S300-600 had constant values throughout the study area (with no statistical difference between stations). In addition, S300-600 was merely varied in the stations located at the river mouth and coastal water. Based on the spectral slope ratio (SR), most of the stations located in the Darau, Inanam, and Bangka-Bangka rivers had SR values less than 1. Hence, CDOM in these stations is a terrestrial-dominated source. Therefore, from our observations during the study period, monsoonal variation could alter the source of CDOM in the study area.
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Inconsistent response of biophysical characteristics in the western Bay of Bengal associated with positive Indian Ocean dipole
Oceanologia 2022, 64(4), 595-614
https://doi.org/10.1016/j.oceano.2022.04.003

Vivek Seelanki1, Tanuja Nigam1,2, Vimlesh Pant1,*
1Centre for Atmospheric Sciences, Indian Institute of Technology Delhi, New Delhi, India;
e-mail: vimlesh@cas.iitd.ac.in
2National Institute of Oceanography, Goa, India

keywords: Chlorophyll-a, Ekman transport, Bay of Bengal, Primary productivity, Indian Ocean Dipole, Biophysical model

Received 30 August 2021, Revised 15 April 2022, Accepted 20 April 2022, Available online 4 May 2022, Version of Record 29 September 2022.

Abstract

The Bay of Bengal (BoB) is known to have high primary productivity at its western margin during the Indian summer monsoon season (June–September). This higher coastal productivity is mainly caused due to the near-surface nutrient availability maintained by the local coastal upwelling process. The surface winds in the Indian Ocean significantly vary during El-Niño/La-Niña and Indian Ocean dipole (IOD). The current study examines the sea surface temperature (SST) and Chlorophyll-a (Chl-a) anomalies in the western BoB for the period of 18 years (2000 to 2017), using a coupled regional ocean biophysical model. All considered positive IOD (pIOD) years show discrete behavior of biophysical features in the western BoB. The co-occurrence years of pIOD and El-Niño modes are associated with contrast biophysical anomalies. In the analyzed pIOD events, the years 2006 and 2012 show an enhancement in the Chl-a anomalies whereas, the other two years (2015 and 2017) experience Chl-a decrement. The western BoB was anomalously warmer during the 2015 and 2017 pIOD years compared to the other two pIOD years (2006, 2012). This inconsistent response of biophysical features associated with pIOD years is investigated in terms of local surface flux (momentum, heat, and freshwater) changes over the western BoB. The combined impact of local surface flux changes during the individual years remains the major contributing factor affecting the upper-ocean stratification. Ultimately, the stratification changes are responsible for the observed inconsistent response of biophysical features by significantly altering the upper-ocean mixing, upwelling, and nutrient availability in the western BoB.
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Impact of environmental factors on phytoplankton composition and their marker pigments in the northern Adriatic Sea
Oceanologia 2022, 64(4), 615-630
https://doi.org/10.1016/j.oceano.2022.05.002

Elif Eker-Develi1,*, Jean-François Berthon2, Gary Free3
1Mersin University, Faculty of Education, Mersin, Turkey;
e-mail: elif.eker@mersin.edu.tr
*corresponding author
2Joint Research Centre of the European Commission, Ispra, VA, Italy
3CNR, Institute for Electromagnetic Sensing of the Environment, IREA, Rome, Italy

keywords: Phytoplankton composition, Carbon biomass, HPLC-CHEMTAX, Adriatic Sea, Chlorophyll a

Received 2 February 2022, Revised 26 April 2022, Accepted 19 May 2022, Available online 29 May 2022, Version of Record 29 September 2022.

Abstract

Phytoplankton composition, abundance and carbon biomass were investigated at monthly intervals during 2006–2007 at a coastal site, “Acqua Alta” an oceanographic tower, in the northern Adriatic Sea. Results were compared with chlorophyll a concentrations of phytoplankton classes attributed by HPLC-CHEMTAX analysis. Changes in the taxonomic structure were associated with environmental parameters. The total carbon biomass of phytoplankton was positively correlated with the temperature and negatively correlated with silicate concentrations. Nutrient concentrations were higher in the winter–spring period than in the summer-autumn period. The highest carbon biomass and abundance of phytoplankton were observed during summer–autumn months. Diatoms were the group that had the highest contribution to the total carbon biomass during the sampling period. Small flagellates, which were the major contributors to the total cell counts were dominant during the summer period. There was a significant correlation between carbon biomass and CHEMTAX-derived Chl a values of diatoms and dinoflagellates. However, the total carbon biomass of phytoplankton was not correlated with Chl a, which seemed to be related to seasonal changes in the ratios of C:Chl a of all taxonomic classes. This ratio was higher during the summer-autumn period (73 ± 33) than during the winter–spring period (17 ± 20).
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Distribution and characterization of organic matter within the sea surface microlayer in the Gulf of Gdańsk
Oceanologia 2022, 64(4), 631-650
https://doi.org/10.1016/j.oceano.2022.05.003

Abra Penezić1,*, Violetta Drozdowska2,*, Tihana Novak1, Blaženka Gašparović1
1Division for Marine and Environmental Research, Rudjer Boskovic Institute, 10000, Zagreb, Croatia;
e-mail: abra@irb.hr
2Physical Oceanography Department, Institute of Oceanology, Polish Academy of Sciences, Sopot, Poland;
e-mail: drozd@iopan.pl
*corresponding author

keywords: Sea surface microlayer, Chromophoric dissolved organic matter (CDOM), Fluorescent organic matter (FDOM), Surface-active organic substances (SAS), Marine lipids, POC

Received 23 December 2021, Revised 25 May 2022, Accepted 26 May 2022, Available online 8 June 2022, Version of Record 29 September 2022.

Abstract

We present the characterisation and distribution of organic matter (OM) within the sea surface microlayer (SML) and underlying water (ULW) collected in October 2015 at nine stations in the Baltic Sea, Gulf of Gdańsk, encompassing the Vistula River plume. The salinity of >7 throughout the transect indicated Vistula plume was possibly displaced westward by the preceding northerly and easterly winds between 5.7 and 10.7 ms–1 during the sampling campaign. Spectral analysis pointed to the highest contribution of aromatic and high molecular weight molecules (lowest spectral slope (SR) ratios and highest absorption coefficient at 254 nm (aCDOM(254)) at the first two stations near the river mouth, demonstrating a very limited influence of the river plume. Concentrations of surface-active organic substances (SAS) ranged from 0.28 to 0.60 mg L−1 in eq. Triton-X-100 in SML, and from 0.22 to 0.47 mg L−1 in eq. Triton-X-100 in the ULW, while POC concentrations ranged from 0.27 to 0.84 mg L−1 in SML and from 0.20 to 0.37 mg L−1 in ULW. Enrichment of SAS and POC detected at the highest wind speeds indicates rapid SML recovery by OM transported from the ULW. Low lipids to POC contribution, on average 5% and 7% in SML and ULW respectively, points to eutrophic conditions. Statistically significant negative correlation between SR and the Lipid:PIG ratio in SML and ULW suggests the production of lower molecular weight OM by phytoplankton living under favourable environmental conditions. Accumulation of lipid reserves triacylglycerols (TG) in the SML indicates more stressful plankton growth conditions compared to ULW.
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Contaminant transport in the surf zone
Oceanologia 2022, 64(4), 651-664
https://doi.org/10.1016/j.oceano.2022.06.001

David A. Chin*
Department of Chemical, Environmental, and Materials Engineering, University of Miami, Coral Gables, FL, USA;
e-mail: dchin@miami.edu
* corresponding author

keywords: Dispersion, Surf zone, Turbulent diffusion, Waves

Received 7 April 2022, Revised 6 June 2022, Accepted 9 June 2022, Available online 21 June 2022, Version of Record 29 September 2022.

Abstract

Dispersion of dissolved contaminants introduced at various locations within and just outside the surf zone are investigated. It is shown that the Longuet-Higgins model of surf-zone hydrodynamics adequately describes the distribution of longshore currents measured at the laboratory scale. Relations are derived between the longitudinal and transverse dispersion coefficients and the influencing parameters. The maximum longitudinal dispersion coefficients are associated with tracer releases near the breaker line, and longitudinal dispersion coefficients generally increase with travel time for distances up to at least 10 surf-zone widths. In contrast, transverse dispersion coefficients remain relatively constant for increasing travel time. The longitudinal and transverse dispersion coefficients can be significantly influenced by assumed values of local turbulent diffusion and cross-shore shear dispersion.
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Habitat suitability models of five keynote Bulgarian Black Sea fish species relative to specific abiotic and biotic factors
Oceanologia 2022, 64(4), 665-674
https://doi.org/10.1016/j.oceano.2022.06.002

Ivelina Zlateva*, Violin Raykov, Violeta Slabakova, Elitsa Stefanova, Kremena Stefanova
Institute of Oceanology “Fridtjof Nansen”, Bulgarian Academy of Sciences, Varna, Bulgaria;
e-mail: ibikarska@yahoo.com
*corresponding author

keywords: Habitat suitability, Spatial distribution, MaxEnt, Biotic interactions, Abiotic variables, Black Sea

Received 17 December 2021, Revised 2 June 2022, Accepted 9 June 2022, Available online 22 June 2022, Version of Record 29 September 2022.

Abstract

Over the past few years, predicting species spatial distributions has been recognized as a powerful tool for studying biological invasions in conservation biology and planning, ecology, and evolutionary biology. Species spatial distribution models (SDMs) are used extensively for assessing the effects of changes in habitat suitability, the impacts of climate change, and the realignment of the existing conservation priorities. SDMs relate known patterns of species occurrences to a specific set of environmental conditions. Accordingly, we have used MaxEnt SDM tool in order to provide habitat suitability models of 5 keynote fish species: European sprat (Sprattus sprattus L.), red mullet (Mullus barbatus, L.), horse mackerel (Trachurus mediterraneus, L.), bluefish (Pomatomus saltatrix, L.) and whiting (Merlangius merlangus, L.), inhabiting the Bulgarian region of the Black Sea. Presence-only (PO) data collected by pelagic surveys performed between 2017 and 2019 was further utilized to link known species occurrence localities with selected abiotic factors, such as surface sea temperature and salinity, dissolved oxygen, and speed of currents. Biotic interactions were also considered for fitting the patterns of habitat suitability models. The SDMs, obtained from the present research study, prove to have satisfactory predictive accuracy to be further implemented for conservation measures and planning, stock management policy-making, or ecological forecasting.
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Physical control on the inter-annual variability of summer dissolved nutrient concentration and phytoplankton biomass in the Indian sector of the Southern Ocean
Oceanologia 2022, 64(4), 675-693
https://doi.org/10.1016/j.oceano.2022.06.003

Jenson Vilayil George*, Ravidas Krishna Naik, Narayanapillai Anilkumar, Prabhakaran Sabu, Shramik Maruti Patil, Rajani Kanta Mishra
National Centre for Polar and Ocean Research, Goa, India;
e-mail: jenson@ncpor.res.in *corresponding author

keywords: Indian sector of the Southern Ocean, Chlorophyll-a, Nutrients, Winter mixing, Sea ice, Fronts

Received 1 October 2021, Revised 10 June 2022, Accepted 16 June 2022, Available online 1 July 2022, Version of Record 29 September 2022.

Abstract

To understand the role of physical processes and their interannual variability on the dissolved nutrient concentration and phytoplankton biomass distribution, field data collected in the Indian sector of the Southern Ocean (ISSO) during the austral summer of 2009–2011 are used. In the subtropical zone, macronutrients were limited (N:P < 1, N:Si < 1, Si:P ≈ 1) and the phytoplankton biomass variability was mainly governed by the mesoscale eddy activity associated with the Agulhas Return Current. High nutrient low chlorophyll condition prevailed in the sub-Antarctic zone and further south. A South-North gradient of the upper layer dissolved SiO2 was higher than that of NO3. The sub-Antarctic zone was characterized by the highest N:Si ratio (>4) and it was associated with the enhanced draw down of silicate due to the winter/spring diatom blooms in the region. The chlorophyll-a (CHL) concentration in the Polar Frontal Zone was low (0.2 mg m–3) in 2009 and 2010 but it was high (0.5 mg m–3) in 2011. This increase in CHL in 2011 was due to the supply of dissolved iron from the strong winds and subsequent mixing during the winter of 2010. Further, the increased CHL values in the Antarctic zone (0.5 mg m–3) in 2011 compared to 2009 and 2010 could be due to the increased sea ice melting associated with positive Southern Annular Mode. The increased phytoplankton biomass in the summer of 2011 coincides with an increase in nitrate utilization (N:P≈13) compared to 2009 and 2010. Observations showed that ISSO frontal zones are characterized by inter-annual variability in terms of nutrient utilization and phytoplankton biomass production.
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Effects of different conditions on particle dynamics and properties in West-Estonian coastal areas
Oceanologia 2022, 64(4), 694-716
https://doi.org/10.1016/j.oceano.2022.06.006

Mirjam Uusõue1,*, Martin Ligi1,*, Tiit Kutser2,*, François Bourrin3,*, Kristi Uudeberg1,*, Kersti Kangro1,*, Birgot Paavel2,*
1Tartu Observatory, University of Tartu, Tartumaa, Estonia;
e-mail: mirjam.uusoue@ut.ee, martin.ligi@ut.ee, kristi.uudeberg@gmail.com, kersti.kangro@ut.ee
2Estonian Marine Institute, University of Tartu, Tallinn, Estonia;
e-mail: tiit.kutser@ut.ee, birgot.paavel@ut.ee
3CEFREM, UMR 5110 CNRS, UPVD, Perpignan Cedex, France;
e-mail: francois.bourrin@univ-perp.fr
*corresponding author

keywords: Suspended particulate matter, Inherent optical properties, Backscattering ratio, Particle size distribution, Aggregation

Received 24 April 2021, Revised 20 June 2022, Accepted 27 June 2022, Available online 13 July 2022, Version of Record 29 September 2022.

Abstract

Satellite sensors are used to monitor water on a large scale. One of the key variables defining the water-leaving signal is suspended particulate matter (SPM) and thus it is important to understand its properties to improve remote sensing algorithms. However, only a few studies investigating the variability of SPM properties (concentration, nature and size) under different seasonal, weather and geographical conditions have been carried out in the Baltic Sea. We focused on relatively shallow areas (maximum depth of 10 m) where there is strong sediment transport by rivers and resuspension of the particles by wave action and advection by currents. Eleven field campaigns were conducted using a set of instruments measuring inherent optical properties, auxiliary data, and, in Pärnu Bay, also particle size distributions. The results showed that the SPM concentrations, particulate absorption, mass-specific particulate scattering, and backscattering varied temporally and spatially from 5.5–19.6 g m−3, 0–5.62 m−1, 0.08–1.45 m2 g−1, and 0.0009–0.25 m2 g−1, respectively. The spectral backscattering ratio, which in general is considered to be constant in bio-optical remote sensing algorithms, was actually wavelength-dependent and varied between 0.005 and 0.09 depending on the origin of the particles (organic or mineral matter), particle size distribution, weather conditions, and location. In situ particle size measurements in coastal waters of Pärnu Bay also showed that resuspended fine clay particles agglomerated into flocs of >30 µm in the brackish waters of the Baltic Sea having random shapes and different sizes.
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Noctiluca blooms intensify when northwesterly winds complement northeasterlies in the northern Arabian Sea: Possible implications
Oceanologia 2022, 64(4), 717-734
https://doi.org/10.1016/j.oceano.2022.06.004

Nittala S. Sarma1,*, Sanjiba Kumar Baliarsingh2, Sudarsana Rao Pandi3, Aneesh Anandrao Lotliker2, Alakes Samanta2
1Marine Chemistry Laboratory, Andhra University, Visakhapatnam, India;
e-mail: sarmanittala@gmail.com
2Indian National Centre for Ocean Information Services, Ministry of Earth Sciences, Govt. of India, Hyderabad, India
3National Centre for Polar and Ocean Research, Ministry of Earth Sciences, Govt. of India, Vasco-da-Gama, Goa, India
*corresponding author

keywords: Noctiluca scintillans, Harmful Algal Bloom, Phytoplankton, Iron fertilization, HYSPLIT back trajectories, Bloom model

Received 5 October 2021, Revised 18 June 2022, Accepted 27 June 2022, Available online 10 July 2022, Version of Record 29 September 2022.

Abstract

Wind systems are known as nutrient sources playing significant roles in the oceanic realm and global climate oscillations. This study explores, for the first time, the effect of winds on the winter blooms of the mixotrophic dinoflagellate, the green variant of Noctiluca scintillans (NSG) in the northern Arabian Sea. When the NSG abundance was lower (i.e., <∼10000 cells l−1), it was coupled to silicic acid (H4SiO4), on which diatoms (phytoplankton) in turn depended. At higher abundance (i.e., NSG>∼10000 cells l−1), H4SiO4 and H4SiO4:DIN (dissolved inorganic nitrogen) ratio fell. The NSG was then intensely green and chlorophyll-a richer, attributed to a change in the mode of NSG's nutrition from heterotrophy to autotrophy-dominance. The back-trajectory model revealed that the winds were mostly northeasterly (NE) initially (during February) and were north-westerly (NW) towards the end of winter (March). Separately for the NE and NW winds, the NSG abundance was 10655±18628 and 28896±46225 cells l−1, respectively. The H4SiO4:DIN ratio correspondingly reached <0.2 and ≥0.4. The NSG was modelled with high significance (p<0.001, N=33) versus the NE and NW wind speeds. Thus, while the NE winds deepened the mixed layer and caused nutrient enrichment and phytoplankton production, the NW winds facilitated the recovery of the H4SiO4:DIN ratio and economical use of H4SiO4 for phytoplankton production. It is hypothesized that this process is helped by iron input from NW desert winds during the latter part of winter when the NSG blooms intensify.
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Dynamics of trace metals in sediments of a seasonally hypoxic coastal zone in the southeastern Arabian Sea
Oceanologia 2022, 64(4), 735-748
https://doi.org/10.1016/j.oceano.2022.06.007

Dayana Mathew1, Thundiyil Raju Gireeshkumar1,*, Kareekunnan Shameem2, Camey Monica Furtado1, Kanneth Satheesan Arya1, Pallikkoottathil Balakrishnan Udayakrishnan3, Kizhakkepat Kalathil Balachandran1
1CSIR – National Institute of Oceanography, Regional Centre, Kochi, India;
e-mail: gkumar@nio.org
2Inter University Centre for Development of Marine Biotechnology, School of Marine Sciences, Cochin University of Science and Technology, Kochi, India
3CSIR – National Institute of Oceanography, Regional Centre, Mumbai, India
*corresponding author

keywords: Geochemistry, Trace metals, Upwelling, Hypoxia, Organic matter, Bioavailability

Received 10 February 2021, Revised 17 June 2022, Accepted 27 June 2022, Available online 14 July 2022, Version of Record 29 September 2022.

Abstract

This study examined the effect of water column hypoxia on the distribution and geochemical fractionation of trace metals in the seasonally hypoxic coastal environment in the southeastern Arabian Sea. Water and surface sediments were collected fortnightly from the Alappuzha mud bank between April and August 2016, which covered the pre-upwelling and upwelling seasons. The water column was warm and well-oxygenated during April–May. During June–August, the incidence of cold and hypoxic water indicated strong coastal upwelling prevailed in the entire study domain. The Fe and Mn content in sediments gradually decreased, because of the reductive dissolution and subsequent release of metals under hypoxia. The concentration of metals such as Ni, Zn and V decreased substantially under oxygen deficiency, whereas Cr showed marked enrichment in sediments. Although the geochemical forms of trace metals displayed the dominance of residual fractions (inert), the reactive non-residual metal forms (exchangeable, Fe/Mn-(oxy)hydroxide, and organic matter/sulphide bound) showed considerable variability under hypoxia. The shift from Fe/Mn-(oxy)hydroxide bound to organic matter and sulphide bound was evident during hypoxia. Cr exhibited a strong affinity towards organic matter and sulphide, and Pb and Zn showed relatively high association towards the Fe/Mn-(oxy)hydroxide phase. Even with such a phase shift induced by the hypoxic conditions, the concentrations of these metals remained within the normal background levels, indicating the pristine nature of the mud bank environment.
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Seasonal assessment of the trophic status in the coastal waters adjoining Tuticorin harbor in relation to water quality and plankton community in the Gulf of Mannar, India
Oceanologia 2022, 64(4), 749-768
https://doi.org/10.1016/j.oceano.2022.07.002

Rengasamy Subramaniyan Sathishkumar1,2,*, Arumugam Sundaramanickam1,*, Ajit Kumar Mohanty2, Gouri Sahu2, Thangavelu Ramesh1, Kumar Balachandar3, Ajith Nithin1, Parthasarathy Surya1 , Krishnan Silambarasan3
1Centre of Advanced Study in Marine Biology, Annamalai University, Parangipettai, Tamil Nadu, India;
e-mail: rssathishphd@gmail.com, fish_lar@yahoo.com
2Radiological and Environment Safety Division, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu, India;
3Fishery Survey of India, Beach Road, Visakhapatnam, Andhra Pradesh, India;
*corresponding author

keywords: Algal bloom, Eutrophication, Plankton diversity, Southeast coast of India, Trichodesmium, TRIX

Received 21 June 2021, Revised 8 June 2022, Accepted 21 July 2022, Available online 5 August 2022, Version of Record 29 September 2022.

Abstract

Seasonal variations in hydrography, trophic status, and plankton community structure were studied along the Tuticorin coastal waters (TCWs) in the Gulf of Mannar (GoM). Samples were collected in 2015 and 2016 to analyze physico-chemical (temperature, pH, salinity, suspended particulate matter (SPM), dissolved oxygen (DO), nutrients, etc.) and biological parameters (chlorophyll-a, phytoplankton, and zooplankton). The trophic index (TRIX) and eutrophication index (EI) were calculated to describe the eutrophication status of TCWs. Temperature, pH, salinity, DO, and SPM showed seasonality due to the impact of the northeast monsoon. A massive bloom of Trichodesmium erythraeum was observed, with a visible impact on water quality and the plankton community. The cluster and principal component analysis indicated the bloom event as a distinct phenomenon. ANOVA results showed significant seasonal variations rather than spatial variations. According to the trophic indices, the area had a low trophic level in 2015 and a high trophic level in 2016. The Tuticorin inshore waters had the highest TRIX and EI values during the dominance of cyanobacteria bloom in the post-monsoon 2016. The trophic indices had a positive relationship with phytoplankton abundance but showed an inverse relation with zooplankton abundance. The overall range of the TRIX index (3.18–5.96) indicated that the environment was oligotrophic to eutrophic, and EI values (0.72–21.61) indicated that the state of coastal waters was moderate to poor. This study states that periodic monsoonal flow and frequent algal bloom events have a significant impact on the GoM coastal waters.
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Plastic contamination of sandy beaches along the southern Baltic – a one season field survey results
Oceanologia 2022, 64(4), 769-780
https://doi.org/10.1016/j.oceano.2022.07.004

Mikołaj Mazurkiewicz*, Paula Sancho Martinez, Weronika Konwent, Kajetan Deja, Lech Kotwicki, Jan Marcin Węsławski
Institute of Oceanology Polish Academy of Sciences, Sopot, Poland;
e-mail: mikolaj@iopan.gda.pl
*corresponding author

keywords: Microplastic, Marine litter, Sources, Coastal zone, Baltic Sea

Received 3 February 2022, Revised 1 July 2022, Accepted 23 July 2022, Available online 5 August 2022, Version of Record 29 September 2022.

Abstract

The subject of this study was microplastics (>32 µm), large micro-/macroplastics (>2 mm) and plastic litter (visible by naked eye) contamination on sandy beaches and in coastal waters along the Polish coast of the Baltic Sea. Microplastics were studied with particular attention, with simultaneous observations in the water and across the beach. Other data was intended to serve as a background and as possible sources of microplastics. Most of the microplastics found were fibers <1 mm long, with blue fibers dominating, followed by transparent, red and green ones, both in sand and water samples. The concentration of microplastics on the beach sand ranged from 118 to 1382 pieces kg−1, while in coastal waters from 0.61 to 2.76 pieces dm−3. As for large micro-/macroplastics and plastic litter, there was no dominant litter along the coast. The amount of large micro-/macroplastics ranged from 2 to 124 pieces m−2 (or from 0.13 to 44.30 g m−2). Regarding plastic litter, on average between 0.03 and 6.15 litter debris m−2 were found (or from 0.007 to 4.600 g m−2). The study confirms that plastic pollution of the Polish coastal zone is a significant problem comparable with both the rest of the Baltic Sea and other seas and oceans. Similar color-based composition of microplastics among all studied sites suggests that they may have a common source, while the contamination of large micro-/macroplastics and plastic litter (both amount of particles and their composition) along the Polish coast is highly site-specific and may be influenced by various local factors.
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Short communication


Factors responsible for the sudden outburst of Noctiluca scintillans in the Chennai coastal waters, southeast coast of India – a case study
Oceanologia 2022, 64(4), 781-788
https://doi.org/10.1016/j.oceano.2022.06.005

Pravakar Mishra, Mehmuna Begum*, Anitha Gera, B. Charan Kumar, Garlapati Deviram, Uma Kanta Pradhan, Athan Vashi, Debasmita Bandyopadhyay, Subrat Naik, Uma Sankar Panda, M.V. Ramana Murthy
National Centre for Coastal Research (NCCR), Ministry of Earth Sciences, NIOT Campus, Pallikaranai, Chennai, India;
e-mail: mehmuna@gmail.com
*corresponding author

keywords: Noctiluca scintillans, Diatoms, Bloom, Bioluminescence, Chennai coast, India

Received 27 September 2021, Revised 17 May 2022, Accepted 26 June 2022, Available online 13 July 2022, Version of Record 29 September 2022.

Abstract

The paper discusses the factors associated with the sudden outbreak of the nocturnal heterotrophic bioluminescent dinoflagellate Noctiluca scintillans along the Chennai coast. The bloom occurred along a stretch of 16 km following a spell of heavy rain in August 2019. The density of N. scintillans varied from 1000 to 19000 cells/L, with a distinguished distribution pattern. High N. scintillans abundance was recorded at Panaiyurkuppam and Kovalam, with 19000 cells/L and 18000 cells/L, recorded respectively. Adequate nutrients brought by substantial rainfall and a high abundance of the diatom Thalassiosira sp. triggered the N. scintillans bloom. The low wind speed (5 m/sec), lowering of atmospheric temperature (from 24.00 to 31.00°C, 27.5 ± 1.17°C), high rainfall (6 mm within one day), and low sea surface temperature (SST) (from 25.20 to 31.00°C, 29.37± 1.17°C) are probable environmental cues. Local hydrodynamics and the diverging currents governed the presence and dispersion of the bloom in the region.
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Sea spray volume flux estimation using joint statistics of wind and waves
Oceanologia 2022, 64(4), 789-793
https://doi.org/10.1016/j.oceano.2022.07.005

Dag Myrhaug*, Bernt J. Leira, Gowtham Radhakrishnan, Håvard Holm
Department of Marine Technology, Norwegian University of Science and Technology (NTNU), Trondheim, Norway;
e-mail: dag.myrhaug@ntnu.no
*corresponding author

keywords: Sea spray volume flux, Joint wind and wave conditions, Wind waves, Stochastic method

Received 8 February 2022, Revised 8 July 2022, Accepted 23 July 2022, Available online 6 August 2022, Version of Record 29 September 2022.

Abstract

This article provides estimates of the sea spray volume flux using joint statistics of wind and waves. This is achieved by combining the sea spray volume flux parameterization proposed by Xu et al. (2021) with the joint statistics of wind and waves provided by Bitner-Gregersen (2015). Both the sea spray volume flux formula and the joint statistics of wind and waves represent conditions for wind waves from the North-West Shelf of Western Australia. The expected value and the variance of the sea spray volume flux for a range of realistic wind and wave conditions are presented, as well as an illustrative example. Comparison is also made with data from Xu et al. (2021) showing a reasonable agreement for the relevant subset of the data.
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