Oceanologia No. 63 (1) / 21


Original research article


Original research article

Long term variation of sardine Sardina pilchardus spawning along the Atlantic coast of northwest Africa (21–26°N): characterization and spatiotemporal variability in spawning habitat
Oceanologia 2021, 63(1), 1-11

Hinde Abdelouahab1,*, Amina Berraho1,*, Tarik Baibai1,*, Jamila Larissi1,*, Said Charib1,*, Aziz Agouzouk1,*, Ahmed Makaoui1,*, Omar Ettahiri1,*, Ahmed Errhif2,*,
1Institut National de Recherche Halieutique, Casablanca, Morocco;
e-mail: hind.abdelouahab@gmail.com , aminaberraho@gmail.com , baibaitarik@gmail.com , larissijamila@gmail.com , saidcharib@gmail.com , oceanosaad@gmail.com , oceanomakaoui@gmail.com , omarettahiriomar@gmail.com
2University Hassan II of Casablanca, Faculty of Sciences, Ain Chock, Casablanca, Morocco;
e-mail: aerrhif@gmail.com
*corresponding author

keywords: Sardine, Spawning habitat, Environment, Time series, Sea surface temperature

Received 3 February 2020, Revised 20 August 2020, Accepted 25 August 2020, Available online 3 September 2020.


Small pelagic fish such as sardine show strong recruitment variability often associated with environmental changes influencing the spawning process and ultimately, affecting population dynamics. Sardine (Sardina pilchardus, Walbaum 1792) is one of the most exploited pelagic species along the northwest African coast. The main spawning occurs during the cold season (autumn–winter). A time-series autumn–winter surveys extending from 1994 to 2015 sampled sardine eggs, along the southern area of the Moroccan Atlantic coast (26°N–21°N) were analyzed. The present work focuses on examining the inter-annual variability of the spawning habitat by analyzing the spatial-temporal variability of sardine egg distribution and density extracted from the data collected over the period 1994–2015. Generalized additive models (GAM) were used to detect the relationships between the sardine distribution, expressed as egg density and the presence or absence data and relevant hydrobiological environmental variables, such as salinity, temperature and zooplankton biomass. The generalized additive models showed significant relationships between the environment variables (SST, SSS and Zooplankton biomass) and sardine density, but not with sardine presence. Given that the study area is characterized by high mesoscale features and significant upwelling activities, the variability of upwelling processes could explain the changes of spawning ground position and thermal window.
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Assessment of a sheltered euhaline area of the southeastern Bay of Biscay to sustain bivalve production in terms of phytoplankton community composition
Oceanologia 2021, 63(1), 12-26

Jone Bilbao1,2,*, Oihane Muñiz3, José Germán Rodríguez3, Marta Revilla3, Aitor Laza-Martínez1,2, Sergio Seoane1,2
1Department of Plant Biology and Ecology, Faculty of Science and Technology, University of the Basque Country, UPV/EHU, Leioa, Spain;
e-mail: jone.bilbao@ehu.eus
2 Research Centre for Experimental Marine Biology and Biotechnology (Plentzia Marine Station, PiE – UPV/EHU), University of the Basque Country, Plentzia, Spain
3AZTI, Marine Research Division, Pasaia, Spain
*corresponding author

keywords: Phytoplankton community composition, Biomass, Physico-chemical variables, Aquaculture, Mussels, Bay of Biscay

Received 28 April 2020, Revised 26 August 2020, Accepted 27 August 2020, Available online 6 September 2020.


This study describes the phytoplankton community in sheltered euhaline waters of the Basque coast (southeastern Bay of Biscay). Phytoplankton composition, cell size, abundance, biomass and the presence of potentially toxic taxa, together with chlorophyll a, nutrients and hydrographic and optical conditions were measured, from August 2016 to August 2017, in the Mutriku port, with the main aim of assessing the suitability of the phytoplankton community as a food resource for bivalves. The water column in Mutriku showed the typical environmental conditions of Basque marine waters, with no significant nutrient enrichment caused by anthropogenic pressures. Haptophytes represented the greatest contribution to cell abundance (31–47%), and diatoms were the dominant group in terms of biomass (52–79%), which could favour mussel growth due to their high fatty acid content. In addition, the size structure of the phytoplankton community was suitable for mussel ingestion, since the predominant cell size was 2–20 µm. Regarding toxic phytoplankton, the genera that pose a risk for human health and those that affect negatively mussel physiology and survival were considered. Altogether, ten toxic phytoplankton taxa were identified, contributing in less than 5% to the total cell abundance of Mutriku. However, median chlorophyll a concentration was low (0.5 µg L−1), reflecting the oligotrophic conditions of the area. Therefore, even if the composition of the phytoplankton community could be favourable for bivalve aquaculture, biomass values are low compared to other zones of bivalve production.
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Assessment of wave energy in the Persian Gulf: An evaluation of the impacts of climate change
Oceanologia 2021, 63(1), 27-39

Hamid Goharnejad1,2,*, Ehsan Nikaein1,*, Will Perrie2,*
1Department of Civil Engineering, Environmental Sciences Research Center, IslamShahr Branch, Islamic Azad University, IslamShahr, Iran;
e-mail: hgn1982@gmail.com, nikaein_e@yahoo.com
2Fisheries and Oceans Canada, Bedford Institute of Oceanography, Dartmouth, Nova Scotia, Canada;
e-mail: william.perrie@dfo-mpo.gc.ca
*corresponding author

keywords: Wave energy potential, RCP8.5, RCP4.5, Persian gulf, Mike SW

Received 31 January 2020, Revised 7 September 2020, Accepted 9 September 2020, Available online 28 September 2020.


We are motivated to study the exploitation of marine energy as a renewable resource because of society's ever-increasing energy demands, and a concomitant need to reduce greenhouse gas emissions. Additionally, climate-related variations in wave energy should be investigated in order to ensure the stability of its long-term availability. Here, we investigate the potential for wave energy in the Persian Gulf along the southern coasts of Iran. To do so, we have applied the Mike SW numerical model and ECMWF wind field data for a 30-year study, from 1988 to 2017. For this purpose, wave energy was evaluated at six points in the western, northern, southern, and eastern parts of the Persian Gulf. To assess the impacts of climate change, we also consider the wave regime from 2070 to 2099 (for 30 years) following IPCC RCP4.5 and RCP8.5 climate change scenarios. Our findings suggest that in the present climate, seasonal variations in the mean wave parameters (i.e. wave energy, wave period, and significant wave height) correspond to the lowest wave energy in the summers, and highest in the winters. In the future climate change scenarios, energy level variations generally have similar patterns, with slight modulations in some local areas.
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Satellite estimates of the long-term trend in phytoplankton size classes in the coastal waters of north-western Bay of Bengal
Oceanologia 2021, 63(1), 40-50

Joereen Miranda1,*, Aneesh Anandrao Lotliker2, Sanjiba Kumar Baliarsingh2, Amit Kumar Jena1, Alakes Samanta2, Kali Charan Sahu1, Tummala Srinivasa Kumar2
1Department of Marine Sciences, Berhampur University, Bhanjabihar-760007, India;
e-mail: joereen@gmail.com
2Indian National Centre for Ocean Information Services, Ministry of Earth Sciences, Govt. of India, Hyderabad-500090, India
*corresponding author

keywords: MODISA, Algorithm, Coastal, Monsoon, Phytoplankton Size Classes

Received 25 May 2020, Revised 10 September 2020, Accepted 11 September 2020, Available online 25 September 2020.


The study presents long-term variability in satellite retrieved phytoplankton size classes (PSC) at two coastal sites, off Gopalpur and Visakhapatnam, in the north-western Bay of Bengal. The abundance-based models by Brewin et al. (2010) (B10) and Sahay et al. (2017) (S17), for retrieval of PSC (micro, nano, and picophytoplankton), from satellite data, were validated. Both the models performed well in the retrieval of nano and microphytoplankton. However, B10 performed poorly in retrieving picophytoplankton. The statistical analysis indicated better performance of the S17 model and hence was applied to Moderate Resolution Imaging Spectroradiometer onboard Aqua satellite (MODISA) data to understand the temporal (at monthly climatology) and spatial variability (from nearshore to offshore). The spatial distribution indicated nearshore dominance of micro and offshore dominance of picophytoplankton. In nearshore waters off Gopalpur, microphytoplankton dominated throughout the year except for months of south-west monsoon (June and July) where the dominance of picophytoplankton was observed. All PSC exhibited similar distribution at an annual scale with a primary peak during pre-monsoon (March and April) and a secondary peak during post-monsoon (September–November). However, microphytoplankton concentration during post-monsoon was higher off Gopalpur in comparison to Visakhapatnam. The higher microphytoplankton concentration during pre-monsoon was attributed to recurrent phytoplankton blooms. Whereas, post-monsoon increment could be attributed to enhanced phytoplankton growth by availing nutrients sourced from monsoonal precipitation induced terrigenous influx. The outcome of the present study recommends the use of the S17 model for satellite retrieval of PSC from the north-western Bay of Bengal.
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Historical occurrences of marine microalgal blooms in Indian peninsula: Probable causes and implications
Oceanologia 2021, 63(1), 51-70

Oyeshina Gideon Oyeku1,2,3, Subir Kumar Mandal1,2,*
1CSIR-Central Salt & Marine Chemicals Research Institute, Gujarat, India;
e-mail: skmandal@csmcri.res.in
2Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
3Bowen University, Iwo, Osun State, Nigeria
*corresponding author

keywords: Arabian Sea, Bay of Bengal, Harmful algal blooms, Indian peninsula, Microalgal blooms, Surface Seawater Temperature

Received 31 March 2020, Revised 27 August 2020, Accepted 31 August 2020, Available online 11 September 2020.


The Indian marine environment supports employment for over 200 million people, including revenue of nearly $7 billion per annum. However, ecological goods and services of the shallow coast and the marine environment of the Indian peninsula are being affected by recurrent blooms of microalgae. One hundred and six published literature, starting from the first report in 1908 to 2017, were reviewed to investigate the historical occurrences of marine microalgal blooms (MMBs) around the Indian peninsula. 154 MMBs comprising 24 genera and 7 classes were reported during the study period. Noctiluca (dinophyceae) and Trichodesmium (cyanophyceae) bloom contributed 34.4% and 31.8% of total blooms. PCA revealed that high sea surface temperature (SST) and salinity were significant driving forces for Trichodesmium blooms formation, while high nutrients (NO3-N, PO4-P, and SiO4-Si) and low salinity triggered prymnesiophyceae, raphidophyceae, bacillariophyceae and most of the dinophyceae blooms. Noctiluca blooms were linked with both eutrophication and the abundance of prey organisms. HABs were generally dinophyceae dominated and were associated with mass mortality of aquatic fauna, human intoxication, paralytic, and ciguatera shellfish poisoning and even death. Increasing SST and anthropogenic influences around the Indian peninsula could increase the occurrences of MMBs (including HABs) and the number of causative taxa. Proper safety measures such as routine monitoring of phycotoxin levels in the environment and local seafood are required to be put in place in other to protect the health of the public.
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Comparison of methods for nocturnal sampling of predatory zooplankters in shallow waters
Oceanologia 2021, 63(1), 71-79

Tomasz B. Linkowski1,*, Ryszard Kornijów1, Maciej Karpowicz2
1Department of Fisheries Oceanography and Marine Ecology, National Marine Fisheries Research Institute, Gdynia, Poland;
e-mail: t.linkowski@mir.gdynia.pl
2Department of Hydrobiology, Faculty of Biology, University of Białystok, Białystok, Poland
*corresponding author

keywords: Sampling methods, Shallow waters, Vistula Lagoon, Column sampler, Light traps, Leptodora, Neomysis, Cercopagis

Received 9 April 2020, Revised 14 October 2020, Accepted 15 October 2020, Available online 23 October 2020.


The aim of the study was to assess the suitability of a plankton net (diameter of 60 cm, mesh size of 500 µm) and a column sampler (length of 200 cm, diameter of 5 cm) for estimating the density of zooplankton predatory species (Neomysis integer, Leptodora kindtii, Cercopagis pengoi). Nocturnal sampling was performed once a month (May–November 2018) in the Vistula Lagoon (southern Baltic) in the range depth of 1.3–3.6 m. Statistical analysis indicated no significant differences between the N. integer and C. pengoi density estimated by the two sampling gears. In the case of L. kindtii, the mean density obtained by the column sampler was higher when analyzing all samples together and/or deep-water samples only (p < 0.02). However, no such differences were found at shallow stations i.e. up to ca. 2 m in depth. It was assumed that the more suitable sampling equipment for estimating zooplankton abundance in a shallow, well-mixed transitional (brackish) basin is the column sampler. This type of gear, so far used mainly for sampling of micro and mesozooplankton, allows the simultaneous nocturnal collection of the entire zooplankton size spectrum, including representatives of large predatory species. The suitability of light traps for qualitative studies of zooplankton species responding positively to light under the high turbidity of the Vistula Lagoon was also investigated. The traps proved to be most useful for N. integer (100% frequency), and much less for L. kindtii (46.2%) and C. pengoi (27.3%).
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Do seasonal dynamics influence traits and composition of macrobenthic assemblages of Sundarbans Estuarine System, India?
Oceanologia 2021, 63(1), 80-98

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

keywords: Macroinvertebrates, Biological Traits Analysis, RLQ, Succession, Sundarbans

Received 6 May 2020, Revised 18 October 2020, Accepted 19 October 2020, Available online 5 November 2020.


The present study investigates the influence of seasonal dynamics on macrobenthic assemblages in four seasons of 2017–2018 from the central sector of Indian Sundarbans which is under the constant threat of climate change. Besides taxonomic analysis, a trait-based approach has also been applied to assess the change in their ecosystem functioning. The maximum species density (11675 ± 11883.31 ind. m−2) was observed during the spring season which declines considerably in the monsoon season (5875 ± 6224.08 ind. m−2). A total of 95 macrobenthic taxa were recorded from Sundarbans and they were dominated by families like Capitellidae, Donacidae, Magelonidae, Nereididae, Paraonidae and Spionidae. Overall, polychaetes have shown higher taxonomic and functional variation than other groups. Opportunistic polychaete species have shown a prominent compositional shift during post-monsoon seasons. Both the univariate and multivariate analyses have shown a significant relation between macrobenthic composition and environmental parameters. SIMPER has depicted that environmental parameters made the station 4 unique for several types of molluscs like Acteocina estriata, Stenothyra deltae and Meretrix meretrix during spring. Trait percentages also showed a seasonal succession pattern and among the trait categories, burrowers and deposit feeders dominated the estuary. A gradual increase in suspension feeders in spring has been noticed. RLQ approach with fourth-corner analysis was used to unravel the relationship between traits and environmental parameters. Hence, the present study provided a comprehensive idea about the species composition along with their trait categories from such a dynamic habitat. That could be the first stepping stone for a long term monitoring of macrobenthic assemblages from this largest delta on earth.
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Spatiotemporal pattern of degradation in arid mangrove forests of the Northern Persian Gulf
Oceanologia 2021, 63(1), 99-114

Hana Etemadi1, Joseph M. Smoak2,*, Esmaeil Abbasi1
1Environmental Science, Persian Gulf Research Institute, Persian Gulf University, Bushehr, Iran
2School of Geosciences, University of South Florida, Florida, USA;
e-mail: smoak@usf.edu
*corresponding author

keywords: Sea-level rise, Climate change, Arid mangrove, Wetland expansion, Persian, Gulf mangroves

Received 1 May 2020, Revised 19 October 2020, Accepted 22 October 2020, Available online 4 November 2020.


Climate change is a major threat to mangrove ecosystems worldwide but particularly those in arid regions that exist near the limit of tolerance to extremes in temperature, precipitation, and salinity. Here we examine Persian Gulf arid mangrove ecosystems from the Nayband and Mond Protected Area in the south-west region of Iran to determine the ability of tidal mangrove forests to respond to rapid urban and industrial development, sea-level rise (SLR), and temperature and precipitation changes. Sea level has been rising by approximately 4 mm yr−1 in this region and might be intensified by subsidence on the order of 1–2 mm yr−1 due to natural phenomena as well as anthropogenic activities associated with fluid extraction. We use remote sensing along with statistical analysis to effectively monitor mangrove area changes over 60 years and infer responses to past environmental trends. Our spatiotemporal analysis demonstrates expansion in some areas and reduction in others. NDVI (Normalized Difference Vegetation Index) results indicate that Nayband mangroves are healthy and expanded between the years of 1990 and 2002 which could be in response to rising temperatures and above-average precipitation. However, NDVI changes after 2002 demonstrate the mangrove health and area have decreased which could be in response to industrial and urban development that occurred immediately after 1997. The natural stresses in this extreme system are been exacerbated by climate change and anthropogenic pressures as such it is essential to develop ways to reduce vulnerability through strategic management planning.
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Impact of human-altered hydrographical setting on the Copepod community structure in an extensive tropical estuary along the southwest coast of India
Oceanologia 2021, 63(1), 115-132

Arunpandi Nagarathinam1, Jyothibabu Retnamma1,*, Jagadeesan Loganathan1,2, Parthasarathi Singaram1, Anjusha Arayillath1, Albin Konnakkamannil Josea1,
1CSIR – National Institute of Oceanography, Regional Centre, Kochi, India;
e-mail: rjyothibabu@nio.org
2CSIR – National Institute of Oceanography, Regional Centre, Visakhapatnam, India
*corresponding author

keywords: Mesozooplankton, Copepods, Barrage, Multivariate analysis, Kochi backwaters

Received 31 August 2020, Revised 21 October 2020, Accepted 23 October 2020, Available online 5 November 2020.


This study presents how human-altered hydrographical settings (flow restrictions) impacts the natural distribution and community structure of copepods in the Kochi Backwaters (KBW), the largest monsoonal estuary along the southwest coast of India. This study is primarily based on an extensive seasonal sampling in the KBW and their comparison with a historical data set. Thannermukkom Barrage (TB) was built in the southern section of the KBW in the 1970s to prevent saline water intrusion to the upstream during the non-monsoon periods. Thirteen locations (1–4 in the downstream, 5–9 in the midstream, and 10–13 in the upstream) were sampled in this study over the entire stretch of the KBW during the Pre-Southwest Monsoon (PRM), Southwest Monsoon (SWM), and Post-Southwest Monsoon (PSWM). The overall effect of TB in the KBW is a seaward push of mesohaline conditions during all seasons with varying intensities. In response to the seaward push of mesohaline conditions, copepods Acartiella keralensis, Acartia plumosa, Acartia sp., Pseudodiaptomus annandalei, Pseudodiaptomus serricaudatus, Euterpina acutifrons and Oithona brevicornis showed a corresponding spatial shift for their highest abundance and diversity from midstream during PRM to the downstream during the SWM/PSWM. Multivariate and IndVal analysis demarcated many indicator species of copepods of different hydrographical settings in the KBW. A comparison with the historical data set showed that there is an apparent long-term change in hydrography, copepod composition and community structure in the upstream of the KBW due to TB.
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Statistical analysis of Mediterranean coastal storms
Oceanologia 2021, 63(1), 133-148

Nikolas T. Martzikos1,*, Panayotis E. Prinos2,*, Constantine D. Memos1,*, Vasiliki K. Tsoukala1,*
1Laboratory of Harbour Works, School of Civil Engineering, National Technical University of Athens 5, Zografou, Greece;
e-mail: nmartzikos@central.ntua.gr, nmarz83@hotmail.com,
cmemos@mail.ntua.gr, v.tsoukala@hydro.civil.ntua.gr,
2Hydraulics Laboratory, Department of Civil Engineering, Aristotle University of Thessaloniki, Thessaloniki, Greece;
e-mail: prinosp@civil.auth.gr
*corresponding author

keywords: Mediterranean Sea, Coastal storms, Extreme events, Coastal engineering

Received 25 March 2020, Revised 3 November 2020, Accepted 6 November 2020, Available online 18 November 2020.


Coastal storms as extreme hydrometeorological events have severe impacts on the coasts and consequently affect the coastal communities, attracting considerable research interest nowadays. Attempting to understand the risk of these extreme events, a coastal storm analysis is accomplished by studying the parameters which define a coastal storm and their properties, such as the wave height, the wave period, the duration, the calm period, and the storm energy. The frequency of occurrence of coastal storms, the thresholds of storm parameters and the way they are interrelating with each other draw a rough outline of wave climate during coastal storm events for a specific location. This information is valuable afterwards for the design of coastal structures and the coastal zone management. In this work, buoy datasets from 30 locations in the Mediterranean Sea are analysed for describing coastal storm activity. A sample of 4008 coastal storms is identified. Each location faces around 10–14 coastal storms per year, with most of them to occur in winter months and their characteristics to be site-dependent. Their average duration is lower than 30 hours, and 25% of them are consecutive events which hit the same location in less than a day. Furthermore, the wave period and the main direction present no remarkable fluctuations during a coastal storm. With this analysis, a deeper understanding of coastal storm severity is pursued, gaining knowledge about their past activity, in order to be prepared in the future and to protect the coastal areas.
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Species-level associations of phytoplankton with environmental variability in the Neva Estuary (Baltic Sea)
Oceanologia 2021, 63(1), 149-162

Mikhail Golubkov*, Vera Nikulina, Sergey Golubkov
Zoological Institute of Russian Academy of Sciences, St. Petersburg, Russian Federation;
e-mail: golubkov_ms@mail.ru
*corresponding author

keywords: Gulf of Finland, Species composition, Eutrophication, Harmful algae, Long-term observations, Climate change

Received 26 May 2020, Revised 9 November 2020, Accepted 13 November 2020, Available online 27 November 2020.


Changes in phytoplankton communities due to anthropogenic nutrient load and climate change often lead to eutrophication and harmful algal blooms that can affect biogeochemical cycling. However, little is known about the specific responses of various species to environmental variables. 17-year long data on the midsummer phytoplankton biomass in the Neva Estuary were analyzed to show the changes in the composition of phytoplankton in relation to water depth, transparence, salinity, temperature, concentrations of total phosphorus and chlorophyll a, and plankton primary production. One hundred seventy-four species and forms from eight taxonomic classes were found in phytoplankton. Fifteen species were potentially harmful. The most diverse and abundant groups were cyanobacteria, green algae and diatoms. Canonical Correspondence Analysis showed that the biomass of various species from each phytoplankton group correlated differently with environmental factors. However, within each group, there were some predominant trends in the correlative response to changes in environmental variables. The biomass of cyanobacteria was high in the middle and lower reaches of the estuary and, in general, positively correlated with water salinity. The biomass of most species of green algae and diatoms correlated negatively with it. These algae showed a positive trend in biomass in the upper and middle reaches of the estuary during the last decades that may be explained by changes in weather conditions. Taking into account that climate models predict future increases in precipitation and temperature in the northern Baltic, the future expansion of freshwater phytoplankton species in estuaries of the northern Baltic Sea is very likely.
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Corrigendum to “Some probabilistic properties of surf parameter” [Oceanologia 62 (2020) 395–401]
Oceanologia 2021, 63(1), v

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

Refers to:
Dag Myrhaug
Some probabilistic properties of surf parameter
Oceanologia, Volume 62, Issue 3, July–September 2020, Pages 395-401

Received 15 September 2020, Accepted 17 September 2020, Available online 16 October 2020.
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