Oceanologia No. 59 (3) / 17

Contents

In Memoriam

Original research article

Short communications

Original research article


Light absorption by phytoplankton in the southern Baltic and Pomeranian lakes: mathematical expressions for remote sensing applications
Oceanologia 2017, 59(3), 195-212
https://doi.org/10.1016/j.oceano.2017.03.010

Justyna Meler1,*, Mirosława Ostrowska1, Dariusz Ficek2, Agnieszka Zdun1
1Institute of Oceanology of the Polish Academy of Sciences, Sopot, Poland;
e-mail: jmeler@iopan.pl
*corresponding author
2Institute of Physics, Pomeranian University, Słupsk, Poland

keywords: Baltic Sea; Pomeranian lakes; Parameterization of phytoplankton absorption

Received 12 September 2016, Accepted 27 March 2017, Available online 19 April 2017

Abstract

The absorption properties of phytoplankton in surface waters of the Baltic Sea and coastal lakes are examined in the context of their relationships with the concentration of the main photosynthetic pigment, chlorophyll a. The analysis covers 425 sets of spectra of light absorption coefficients aph(λ) and chlorophyll a concentrations Chla measured in 2006–2009 in various waters of the Baltic Sea (open and coastal waters, the Gulf of Gdańsk and the Pomeranian Bay, river mouths and the Szczecin Lagoon), as well as in three lakes in Pomerania, Poland (Obłęskie, Łebsko and Chotkowskie). In these waters the specific (i.e. normalized with respect to Chla) light absorption coefficient of phytoplankton aph*(λ) varies over wide ranges, which differ according to wavelength. For example, aph*(440) takes values from 0.014 to 0.124 mg−1 m2, but aph*(675) from 0.008 to 0.067 mg−1 m2, whereby Chla ranges from 0.8 to 120 mg m−3. From this analysis a mathematical description has been produced of the specific light absorption coefficient of phytoplankton aph*(λ), based on which the dynamics of its variability in these waters and the absorption spectra in the 400–700 nm interval can be reconstructed with a low level of uncertainty (arithmetic statistical error: 4.09–10.21%, systematic error: 29.63–51.37%).
The relationships derived here are applicable in local remote sensing algorithms used for monitoring the Baltic Sea and coastal lakes and can substantially improve the accuracy of the remotely determined optical and biogeochemical characteristics of these waters.
full, complete article - PDF (2675 K)

Characterization of the northern Red Sea's oceanic features with remote sensing data and outputs from a global circulation model
Oceanologia 2017, 59(3), 213-237
https://doi.org/10.1016/j.oceano.2017.01.002

Ahmed Eladawy1,*, Kazuo Nadaoka2, Abdelazim Negm2,3, c, Sommer Abdel-Fattah1,4, d, Mahmoud Hanafy5, Mohamed Shaltout6,7
1Department of Environmental Engineering, Egypt-Japan University of Science and Technology, Alexandria, Egypt;
e-mail: ahmed.eladawy@ejust.edu.eg
*corresponding author
2Department of Transdisciplinary Science and Engineering, School of Environment and Society, Tokyo Institute of Technology, Japan
3Department of Water and Water Structures Eng., Faculty of Engineering, Zagazig University, Egypt
4McMaster University, Hamilton, Canada
5Marine Science Department, Suez Canal University, Faculty of Science, Egypt
6Oceanography Department, Alexandria University, Faculty of Science, Egypt
7Marine Science Department, Gothenburg University, Sweden

keywords: Northern Red Sea; Remote sensing; SST fronts; Atmospheric parameters; Chlorophyll-a; HYCOM

Received 23 June 2016, Accepted 11 January 2017, Available online 1 February 2017

Abstract

Sea surface temperature (SST) and surface wind (SW) are considered the most important components in air–sea interactions. This study examines the relationships between SST, SW and various oceanic variables in the northern Red Sea (NRS) during the period of 2000–2014. The current study is the first attempt to identify the SST fronts and their relationship with the dominant circulation patterns. SST fronts are mapped using the Cayula and Cornillon algorithms. The analysis is performed with available remote sensing and reanalyzed data together with 1/12° HYbrid Coordinate Ocean Model (HYCOM) outputs. Seasonal-trend decomposition procedure based on loess (STL) is applied for trend analysis, and Principal Component Analysis (PCA) is run for the atmospheric parameters. The SST, SW speed and Chlorophyll-a (Chl-a) changes show insignificant trends during the period of 2000–2014. Meridional SST fronts are more significant during the month of January, and fronts that are perpendicular to the sea's axis occur from February to May. Distinct monthly and spatial variations are present in all the examined parameters, although these variations are less pronounced for the wind direction. The SST is mainly controlled by the air temperature and sea level pressure. Significant correlations exist between the SST and the studied parameters (alongshore wind stress rather than the cross-shore wind stress, surface circulation, MLD, and Chl-a). Surface winds generally flow southeastward parallel to the Red Sea's axis explaining that alongshore wind stress is highly correlated with the studied parameters.
full, complete article - PDF (10348 K)

Calibration of backward-in-time model using drifting buoys in the East China Sea
Oceanologia 2017, 59(3), 238-247
https://doi.org/10.1016/j.oceano.2017.01.003

Fangjie Yu1,2, Jiaojiao Li1, Yang Zhao3,4,*, Qiuxiang Li1, Ge Chen1,2
1College of Information Science and Engineering, Ocean University of China, Qingdao, PR China
2Laboratory for Regional Oceanography and Numerical Modeling, Qingdao National Laboratory for Marine Science and Technology, Qingdao, PR China
3College of Liberal Arts, Journalism and Communication, Ocean University of China, Qingdao, PR China;
e-mail: zhaoyang@ouc.edu.cnm
*corresponding author
4Research Institute of Marine Development of China, Shandong Qingdao, PR China

keywords: Wind drag coefficient; Random walk; Drifter buoys; Oil spill reverse; Oil spill model

Received 28 October 2016, Accepted 18 January 2017, Available online 9 February 2017

Abstract

In the process of oil exploitation and transportation, large amounts of crude oil are often spilled, resulting in serious pollution of the marine environment. Forecasting oil spill reverse trajectories to determine the exact oil spill sources is crucial for taking proactive and effective emergency measures. In this study, the backward-in-time model (BTM) is proposed for identifying sources of oil spills in the East China Sea. The wind, current and random walk are three major factors in the simulation of oil spill sources. The wind drag coefficient varies along with the uncertainty of the wind field, and the random walk is sensitive to various traits of different regions, these factors are taken as constants in most of the state-of-the-art studies. In this paper, a self-adaptive modification mechanism for drift factors is proposed, which depends on a data set derived from the drifter buoys deployed over the East China Sea shelf. It can be well adapted to the regional characteristics of different sea areas. The correlation factor between predicted positions and actual locations of the drifters is used to estimate optimal coefficients of the BTM. A comparison between the BTM and the traditional method is also made in this study. The results presented in this paper indicate that our method can be used to predict the actual specific spillage locations.
full, complete article - PDF (3615 K)

Summer distribution patterns of Trichodesmium spp. in the Changjiang (Yangtze River) Estuary and adjacent East China Sea shelf
Oceanologia 2017, 59(3), 248-261
https://doi.org/10.1016/j.oceano.2017.02.001

Zhibing Jiang1,2,*, Jianfang Chen2,3, Feng Zhou3, Hongchang Zhai2, Dongsheng Zhang2, Xiaojun Yan1,*
1Key Laboratory of Applied Marine Biotechnology, Ministry of Education, Marine College of Ningbo University, Ningbo, China;
e-mail: jzb1217@126.com, yanxiaojun@nbu.edu.cn
*corresponding author
2Key Laboratory of Marine Ecosystem and Biogeochemistry, Second Institute of Oceanography, State Oceanic Administration, Hangzhou, China
3State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, State Oceanic Administration, Hangzhou, China

keywords: Trichodesmium; Changjiang Estuary; East China Sea; Changjiang Diluted Water; Taiwan Warm Current; Kuroshio

Received 26 September 2016, Accepted 24 February 2017, Available online 17 March 2017

Abstract

To examine the distribution of Trichodesmium relative to physicochemical factors during summer in the Changjiang (Yangtze River) Estuary and adjacent East China Sea shelf, three cruises were conducted separately in June 2009, July 2011, and August 2009. Trichodesmium species found were T. thiebautii, T. erythraeum, and T. hildebrandtii. The population was dominated by T. thiebautii, which accounted for >85% of the samples found. Most of them were free trichomes. Colonial forms were rarely observed (approximately 10% of our samples), occurring only in offshore waters. The depth integrated abundances of Trichodesmium were 308 × 103, 1709 × 103, and 3448 × 103 trichomes m−2 in June, July, and August, respectively. Trichodesmium was distributed abundantly in the southern or southeastern part of our study area, where nutrients were low and light penetration, temperature, and salinity were high, which were influenced by the Taiwan Warm Current (TWC) and Kuroshio. Trichodesmium was found in low abundance in inshore, eutrophic, low-salinity waters, which were mainly controlled by the Changjiang Diluted Water (CDW) and coastal current. These results suggest that spatiotemporal changes in the summer Trichodesmium distribution correlate highly with the variations in physicochemical properties that are primarily controlled by the TWC, Kuroshio, and CDW. The summer N2 fixation rate of Trichodesmium was estimated at 12.3 μmol N m−2 d−1 in our study area, contributing >50% of biological N2 fixation.
full, complete article - PDF (2340 K)

Spatial and temporal distribution of heavy metals in coastal core sediments from the Red Sea, Saudi Arabia
Oceanologia 2017, 59(3), 262-270
https://doi.org/10.1016/j.oceano.2017.03.003

Bandar A. Al-Mur1,2, Andrew N. Quicksall2,*, Ahmed M.A. Al-Ansari1
1Department of Environmental Sciences, King Abdul-Aziz University, Jeddah, Saudi Arabia
2Civil and Environmental Engineering, Southern Methodist University, Dallas, USA;
e-mail: aquicksall@smu.edu
*corresponding author

keywords: Jeddah; Red Sea; Heavy metal; Pollution; Sediment core

Received 8 November 2016, Accepted 4 March 2017, Available online 22 March 2017

Abstract

Jeddah is the most industrialized city on the west coast of Saudi Arabia and is under increasing influence of human activities. Heavy metals data were obtained from four near-coast Red Sea sediment cores in close proximity to Jeddah. Chromium, manganese, iron, copper, zinc, and lead were analyzed from depth-resolved sections of each core via heavy acid digestion and inductively coupled plasma-mass spectrometry (ICP-MS). The average concentrations of all four sites were 245.96 mg kg−1, 478.45 mg kg−1, 8506.13 mg kg−1, 251.82 mg kg−1, 623.09 mg kg−1, and 362.75 mg kg−1, respectively. The depth-resolved results showed that highest concentrations of Mn, Cu, and Pb were found in the top 15 cm of the core profile distributions compared to other depth sub-samples. Heavy metal concentrations in core sediments are increased near central Jeddah and have become higher in recent years. The results of enrichment factor calculations indicate little anthropogenic supply of Mn and Cr while Pb, Zn, and Cu show strong anthropogenic input. The Pollution Load Index was higher in the two sites closer to central Jeddah where power and desalination plants and wastewater release are known. This indicates that the area has suffered from heavy metal pollution compared to other non-industrialized sites in the Red Sea. Heavy metal contaminations due to anthropogenic activity should be taken into account to protect the Red Sea during future growth. The results of this work should be considered as a baseline for heavy metals monitoring in the sediments of the Red Sea coast near Jeddah, Saudi Arabia.
full, complete article - PDF (979 K)

Chromophoric dissolved organic matter (CDOM) variability over the continental shelf of the northern Bay of Bengal
Oceanologia 2017, 59(3), 271-282
https://doi.org/10.1016/j.oceano.2017.03.002

Sourav Das1,*, Isha Das1, Sandip Giri1, Abhra Chanda1, Sourav Maity2, Aneesh A. Lotliker2, T. Srinivasa Kumar1, Anirban Akhand3, Sugata Hazra1
1School of Oceanographic Studies, Jadavpur University, Kolkata, India;
e-mail: sourav.biooptics@gmail.com
*corresponding author
2Indian National Centre for Ocean Information Services, Kukatpally, Hyderabad, India
3Coastal and Estuarine Environment Research Group, Port and Airport Research Institute, Nagase, Yokosuka, Japan

keywords: aCDOM(440); Spatio-temporal variability; Sea surface salinity; Northern Bay of Bengal

Received 19 September 2016, Accepted 6 March 2017, Available online 22 March 2017

Abstract

The present paper dealt with the annual dynamics of the absorption coefficient of chromophoric dissolved organic matter at 440 nm {aCDOM(440)} during February 2015 to January 2016 in the continental shelf of northern Bay of Bengal (nBoB) for the first time. Sea surface salinity (SSS), chlorophyll-a (Chl-a), total suspended matter (TSM) were also analyzed. It was hypothesized that CDOM should exhibit significant spatial and temporal variability in this region. aCDOM(440) and spectral slope ranged between 0.1002 m−1–0.6631 m−1 and 0.0071 nm−1–0.0229 nm−1 respectively during the entire study period. Higher values of aCDOM(440) were observed in the near shore stations and gradually decreased towards the offshore. Significant seasonal variability of aCDOM(440) was observed between the monsoon and non-monsoon seasons (p < 0.05). Thus the framed hypothesis was successfully accepted by means of the present study. The CDOM was mainly found to be of allochthonous character in this region. aCDOM(440) portrayed a significant negative linear relationship with SSS (R2 = 0.80; p < 0.05) implying conservative mixing of marine and terrestrial end members. However, examining the spatial variability of the relationship, it was observed that this relationship was significant only in the nearshore stations. While examining the seasonal variability of this relationship, it was found to be most significant during the monsoon (R2 = 0.81; p < 0.05). Thus it was inferred that whenever the SSS gradient was higher, the relationship between aCDOM(440) and SSS was found to be most significant.
full, complete article - PDF (2494 K)

Spatio-temporal pattern of phytoplankton and pigment composition in surface waters of south-eastern Black Sea
Oceanologia 2017, 59(3), 283-299
https://doi.org/10.1016/j.oceano.2017.03.004

Ertugrul Agirbas*, Lutfiye Koca, Ulgen Aytan
Recep Tayyip Erdogan University, Faculty of Fisheries, Rize, Turkey;
e-mail: eagirbas@gmail.com
*corresponding author

keywords: Chlorophyll-a; Pigment; Phytoplankton; HPLC; Black Sea

Received 13 May 2016, Accepted 25 December 2016, Available online 6 January 2017

Abstract

Phytoplankton community, diatom to dinoflagellate ratio and pigment composition in surface waters with nutrient data from April 2013 to March 2014 were monitored in the south-eastern (SE) Black Sea using high performance liquid chromatography (HPLC) and microscopic analyses. Microscopic examination revealed a total of 71 species that consist of dinoflagellate (58%), diatoms (25%) and other groups (17%). Microscopy and HPLC-based pigment analyses revealed almost similar results which suggest that the phytoplankton community is mainly composed of diatoms, dinoflagellates and coccolithophores. Fucoxanthin (mean 0.35 ± 019 μg L−1), peridinin (mean 0.18 ± 0.14 μg L−1) and 19-hexanoyloxyfucoxanthin (mean 0.24 ± 0.15 μg L−1) are prominent pigments which showed significant correlation with Diatom-C (r2 = 0.63–0.71, p < 0.05), Dinoflagellate-C (r2 = 0.49–0.80, p < 0.05) and Coccolithophore-C (r2 = 0.72–0.82, p < 0.05), respectively. Mean carbon biomass of diatoms (36.50 ± 9.72 μg L−1) was higher than that of dinoflagellates (33.32 ± 9.05 μg L−1). Significant differences were also observed in nutrient ratio (N:P and Si:N) (One-way ANOVA, p < 0.05). Results illustrate that HPLC-based pigment approach can be used for taxonomic characterisation of phytoplankton groups in the SE Black Sea. Moreover, relatively high dinoflagellate species dominancy and significant correlations between Phyto-C and marker pigments indicate that phytoplankton community composition is shifting towards much smaller groups in SE coasts of the Black Sea.
full, complete article - PDF (5042 K)

Distribution and role of the genus Oithona (Copepoda: Cyclopoida) in the South China Sea
Oceanologia 2017, 59(3), 300-310
https://doi.org/10.1016/j.oceano.2017.03.009

Lianggen Wang1,2,3,4, Feiyan Du1,2,3,4,*, Xuehui Wang1,2,3,4, Yafang Li1,2,3,4, Jiajia Ning1,2,3,4
1South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, China;
e-mail: feiyanegg@163.com
*corresponding author
2Guangdong Provincial Key Laboratory of Fishery Ecology and Environment, Guangzhou, China
3Scientific Observing and Experimental Station of South China Sea Fishery Resources and Environments, Ministry of Agriculture, Guangzhou, China
4Key Laboratory of South China Sea Fishery Resources Development and Utilization, Ministry of Agriculture, Guangzhou, China

keywords: Oithona; Sea currents; Temperature; Larval fishes; Fish spawns

Received 22 July 2016, Accepted 23 November 2016, Available online 14 December 2016

Abstract

The relationships between the small cyclopoid copepod Oithona and hydrological factors, phytoplankton and ichthyoplankton were evaluated using the data obtained in the central South China Sea (SCS) in summer 2014. The genus abundance ranged from 6.00 ind. m−3 to 93.75 ind. m−3 with high abundance band occurring in the branch of SCS Monsoon Jet. The lower temperature and higher salinity in the surface water of the band than other zones indicated that deep water intrusion was a positive factor for aggregation of the genus. The community structure of the genus was dominated by Oithona plumifera and Oithona similis made up 97% of the genus abundance associated with Oithona tenuis. The result of db-RDA analysis showed that the community structure of the genus was affected by temperature, Chl a, larval fishes and fish spawns, and temperature was the most important limiting factor. The result of GAMs analysis showed that abundance of O. tenuis, and copepodites were affected by Chl a, larval fishes and fish spawns; abundance of O. similis was affected by Chl a and fish spawns; and abundance of O. plumifera was affected by Chl a and larval fishes. Therefore, we suggest that the branch of SCS Monsoon Jet and deep water intrusion favor aggregation of plankton in the central SCS in summer. We confirm that the temperature is the limiting factor to the reproduction of the genus Oithona in tropic seas and the genus Oithona is a food-web linker between primary production and larval fishes in the central SCS.
full, complete article - PDF (1520 K)

An improved Otsu method for oil spill detection from SAR images
Oceanologia 2017, 59(3), 311-317
https://doi.org/10.1016/j.oceano.2017.03.005

Fangjie Yu1,2, Wuzi Sun1, Jiaojiao Li1, Yang Zhao3,*, Yanmin Zhang1,*, Ge Chen1,3
1College of Information Science and Engineering, Qingdao Collaborative Innovation Center of Marine Science and Technology, Ocean University of China, Qingdao, PR China
2Laboratory for Regional Oceanography and Numerical Modeling, Qingdao National Laboratory for Marine Science and Technology, Qingdao, PR China
3College of Liberal Arts, Journalism and Communication, Ocean University of China, Qingdao, PR China;
e-mail: zhaoyang@ouc.edu.cn
*corresponding author

keywords: Remote sensing images; Adaptive threshold segmentation; Edge extraction; Region growing

Received 29 December 2016, Accepted 16 March 2017, Available online 1 April 2017

Abstract

In recent years, oil spill accidents have become increasingly frequent due to the development of marine transportation and massive oil exploitation. At present, satellite remote sensing is the principal method used to monitor oil spills. Extracting the locations and extent of oil spill spots accurately in remote sensing images reaps significant benefits in terms of risk assessment and clean-up work. Nowadays the method of edge detection combined with threshold segmentation (EDCTS) to extract oil information is becoming increasingly popular. However, the current method has some limitations in terms of accurately extracting oil spills in synthetic aperture radar (SAR) images, where heterogeneous background noise exists. In this study, we propose an adaptive mechanism based on Otsu method, which applies region growing combined with both edge detection and threshold segmentation (RGEDOM) to extract oil spills. Remote sensing images from the Bohai Sea on June 11, 2011 and the Gulf of Dalian on July 17, 2010 are utilized to validate the accuracy of our algorithm and the reliability of extraction results. In addition, results according to EDCTS are used as a comparator to further explore validity. The comparison with results according to EDCTS using the same dataset demonstrates that the proposed self-adapting algorithm is more robust and boasts high-accuracy. The accuracy computing by the adaptive algorithm is significantly improved compared with EDCTS and threshold method.
full, complete article - PDF (1689 K)

Can multiple fish farms be integrated within a semi-enclosed bay without causing acute ecosystem degradation?
Oceanologia 2017, 59(3), 318-330
https://doi.org/10.1016/j.oceano.2017.03.006

Kristian Puhr1,*, Kristina Pikelj2,*, Željka Fiket3,*
1Department of Biology, Faculty of Science, University of Zagreb, Zagreb, Croatia;
e-mail: kristian.puhr@gmail.com
*corresponding author
2Department of Geology, Faculty of Science, University of Zagreb, Zagreb, Croatia;
e-mail: kpikelj@geol.pmf.hr
3Division for Marine and Environmental Research, Ruđer Bošković Institute, Zagreb, Croatia;
e-mail: zeljka.fiket@irb.hr

keywords: Aquaculture; Nutrient enrichment; Seabed topography; Wind induced hydrodynamics; Sediment

Received 10 October 2016, Accepted 17 March 2017, Available online 5 April 2017

Abstract

The current study explores the possibility that multiple fish farms (FFs) containing sea bass (Dicentrarchus labrax) and sea bream (Sparus aurata) can be successfully integrated within a semi-enclosed bay in the Croatian Adriatic. The research focuses on determining principal environmental factors (EFs) that control the integration and attempts to estimate their individual and synergic ability to influence deposition and removal of organic matter (OM) and trace elements (TE) from the system. The complexity of the designated tasks demanded a comprehensive number of various datasets and samples to be used in the analysis. The ADCP data revealed strong wind induced currents forming within the research domain resulting in high system flushing efficiency (3.5–6 days). The sediment samples from all stations contained relatively inert minerals which contributed to overall low OM and TE concentrations and very limited variability found across the entire bathymetric range. The thermal advection effect recorded at two stations was attributed to specific seabed topography and the hydrodynamic response formed during Maestral wind episodes. The results indicate that a successful integration of four FFs has taken place within the research site (semi enclosed bay), and that the key EFs responsible for its success are strong wind induced hydrodynamics, favorable seabed topography and sediment mineral composition. The synergy of the principal EFs that formed within the system was found to have an attenuating effect regarding FFs chemical influence (OM and TE) and an amplifying one regarding spatial footprint which extended to ≈2000 m distance.
full, complete article - PDF (2593 K)

Application of neural networks and support vector machine for significant wave height prediction
Oceanologia 2017, 59(3), 331-349
https://doi.org/10.1016/j.oceano.2017.03.007

Jadran Berbić1,*, Eva Ocvirk2, Dalibor Carević2, Goran Lončar2
1Croatian Hydrological and Meteorological Service, Zagreb, Croatia;
e-mail: jberbic@hotmail.com
*corresponding author
2The Faculty of Civil Engineering, University of Zagreb, Zagreb, Croatia

keywords: Significant wave height; Wave prediction; Machine learning; ANN; SVM

Received 14 July 2016, Accepted 18 March 2017, Available online 19 April 2017

Abstract

For the purposes of planning and operation of maritime activities, information about wave height dynamics is of great importance. In the paper, real-time prediction of significant wave heights for the following 0.5–5.5 h is provided, using information from 3 or more time points. In the first stage, predictions are made by varying the quantity of significant wave heights from previous time points and various ways of using data are discussed. Afterwards, in the best model, according to the criteria of practicality and accuracy, the influence of wind is taken into account. Predictions are made using two machine learning methods – artificial neural networks (ANN) and support vector machine (SVM). The models were built using the built-in functions of software Weka, developed by Waikato University, New Zealand.
full, complete article - PDF (10313 K)

Modelling nearshore hydrodynamics and circulation under the impact of high waves at the coast of Varkiza in Saronic-Athens Gulf
Oceanologia 2017, 59(3), 350-364
https://doi.org/10.1016/j.oceano.2017.04.001

Kostas A. Belibassakis*, Flora E. Karathanasi
School of Naval Architecture & Marine Engineering, National Technical University of Athens, Athens, Greece;
e-mail: kbel@fluid.mech.ntua.gr
*corresponding author

keywords: High waves; Wave/current modelling; Sediment transport; Varkiza coast

Received 18 January 2017, Accepted 2 April 2017, Available online 19 April 2017

Abstract

A plethora of physical parameters, such as hydro-, litho- and morpho-dynamic characteristics, are essential for understanding the response of coastal systems to intense sea states in terms of sediment transport and shoreline evolution. Nowadays, numerical models are extensively applied to meet the above needs and support coastal planning and management. In the present work, a 2DH dynamic modelling system is used for simulating the hydrodynamic and meteorological/oceanographic characteristics of the Saronic Gulf, in order to examine circulation patterns and predict sediment transport phenomena under high wave conditions at the coast of Varkiza, a sandy beach in the southern Attica, Greece. Time series of wind and wave data were used as input at the open boundaries of the model domain while the model was calibrated and validated through (linear and directional) statistical measures with respect to in situ wave measurements, since there was lack of hydrodynamic data at the site of interest. The simulation period of the model was between January 3 and February 19, 2013, with consecutive high waves in-between. The good agreement of the numerical results from the wave and hydrodynamic model with in situ measurements confirmed the suitability of the model for the support of sediment transport rates at Varkiza coastal segment. Model results reveal that there is a counter-clockwise water circulation during high waves that contribute to the erosion of the examined beach, which is also confirmed by independent field measurements.
full, complete article - PDF (5044 K)

The relationship between Suspended Particulate Matter and Turbidity at a mooring station in a coastal environment: consequences for satellite-derived products
Oceanologia 2017, 59(3), 365-378
https://doi.org/10.1016/j.oceano.2017.04.003

Madihah Jafar-Sidik1,2,*, Francis Gohin3,*, David Bowers2,*, John Howarth4,*, Tom Hull5,*
1Borneo Marine Research Institute, Universiti Malaysia Sabah, Kota Kinabalu, Malaysia;
e-mail: madihahjsm@gmail.com
*corresponding author
2School of Ocean Sciences, Bangor University, Anglesey, United Kingdom;
e-mail: d.g.bowers@bangor.ac.uk
3Ifremer, Dyneco/Pelagos, Centre Ifremer de Brest, Plouzane, France;
e-mail: Francis.Gohin@ifremer.fr
*corresponding author
4National Oceanography Centre, Joseph Proudman Building, Liverpool, United Kingdom;
e-mail: mjh@noc.ac.uk
5Centre for Environment, Fisheries and Aquaculture Science (Cefas), Lowestoft, United Kingdom;
e-mail: tom.hull@cefas.co.uk

keywords: Turbidity; Suspended matter; MODIS; Irish Sea

Received 3 February 2017, Accepted 7 April 2017, Available online 26 April 2017

Abstract

From a data set of observations of Suspended Particulate Matter (SPM) concentration, Turbidity in Formazin Turbidity Unit (FTU) and fluorescence-derived chlorophyll-a at a mooring station in Liverpool Bay, in the Irish Sea, we investigate the seasonal variation of the SPM:Turbidity ratio. This ratio changes from a value of around 1 in winter (minimum in January–February) to 2 in summer (maximum in May–June). This seasonal change can be understood in terms of the cycle of turbulence and of the phytoplankton population that affects the nature, shape and size of the particles responsible for the Turbidity. The data suggest a direct effect of phytoplankton on the SPM:Turbidity ratio during the spring bloom occurring in April and May and a delayed effect, likely due to aggregation of particles, in July and August. Based on the hypothesis that only SPM concentration varies, but not the mass-specific backscattering coefficient of particles bbp*, semi-analytical algorithms aiming at retrieving SPM from satellite radiance ignore the seasonal variability of bbp* which is likely to be inversely correlated to the SPM:Turbidity ratio. A simple sinusoidal modulation of the relationship between Turbidity and SPM with time helps to correct this effect at the location of the mooring. Without applying a seasonal modulation to bbp*, there is an underestimation of SPM in summer by the Ifremer semi-analytical algorithm (Gohin et al., 2015) we tested. SPM derived from this algorithm, as expected from any semi-analytical algorithm, appears to be more related to in situ Turbidity than to in situ SPM throughout the year.
full, complete article - PDF (2715 K)

Diurnal and seasonal DOC and POC variability in the land-locked sea
Oceanologia 2017, 59(3), 379-388
https://doi.org/10.1016/j.oceano.2017.03.008

Beata Szymczycha*, Aleksandra Winogradow, Karol Kuliński, Katarzyna Koziorowska, Janusz Pempkowiak
Institute of Oceanology, Polish Academy of Sciences, Sopot, Poland;
e-mail: beat.sz@iopan.gda.pl
*corresponding author

keywords: Baltic Sea; Nutrients; Chlorophyll a (Chl a); pH; δ13C; Organic matter

Received 13 February 2017, Accepted 25 March 2017, Available online 19 April 2017

Abstract

Organic matter is a minor yet important component of the marine environment. The aim of this study was to investigate the diurnal and seasonal changes in dissolved and particulate organic carbon (DOC and POC, respectively). Thus, DOC and POC as well as chlorophyll a (Chl a), δ13C, NO3−, NO2−, NH4+, PO43−, salinity, pH, and temperature were regularly measured in samples collected for 24 h (2-h resolution) in the Gdańsk Deep (54°44.730′N, 19°08.531′E) at three water depths (1, 10, and 40 m) during sampling campaigns in 2011 (May), 2014 (May), and 2015 (January, March, May, July, September, November). Seasonal variations in DOC and POC followed the seasonality of Chl a (proportional trend) and nutrients (reverse trend) concentrations. Diurnal oscillations were detected in six out of the eight measurement series. The strongest diurnal variability in both POC and DOC occurred in May 2011 and March 2015, when phytoplankton activity was highest (high Chl a). The surprisingly low δ13C values (range: −28‰ to −24‰) measured over the course of the study revealed the gaps in our knowledge of the isotopic characteristics of terrestrial- vs. marine-derived particulate organic matter.
full, complete article - PDF (1206 K)

Short communications


Estimation of diatom and dinoflagellate cell volumes from surface waters of the Northern Indian Ocean
Oceanologia 2017, 59(3), 389-395
https://doi.org/10.1016/j.oceano.2017.03.001

Rajath R. Chitari, Arga Chandrashekar Anil*
CSIR – National Institute of Oceanography, Dona Paula, Goa, India;
e-mail: acanil@nio.org
*corresponding author

keywords: Diatoms; Dinoflagellates; Cell volume; Dona Paula Bay; Bay of Bengal

Received 14 July 2016, Accepted 1 March 2017, Available online 16 March 2017

Abstract

Phytoplankton samples collected from the Northern Indian Ocean (Bay of Bengal, northern Arabian Sea, and Dona Paula Bay Goa, west coast of India), were utilized to quantify changes in cell size, cell volume and carbon per cell of diatoms and dinoflagellates. The dataset from the Bay of Bengal also provides inter- and intra-annual variations (April 2008 to March 2010). The variations in cell size and volume were large in regions influenced by the riverine influx or terrigenous inputs. An interregional comparison of commonly available forms (8 species) points out that cell volumes are highest in the North Atlantic and lowest in the Mediterranean. The information provided will be useful in estimation of carbon biomass and biogeochemical studies.
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