Oceanologia No. 57 (4) / 15

Contents

Original research article

Original research article


Sea-level change and projected future flooding along the Egyptian Mediterranean coast
Oceanologia 2015, 57(4), 293-307
http://dx.doi.org/10.1016/j.oceano.2015.06.004

Mohamed Shaltout1,3,*, Kareem Tonbol2, Anders Omstedt3
1Department of Oceanography, University of Alexandria,
Alexandria, Egypt;
e-mail: shaltot@alexu.edu.eg
*corresponding author
2Meteorology Program, College of Maritime Transport and Technology, Arab Academy for Science, Technology and Maritime Transport,
Alexandria, Egypt
3Department of Marine Sciences, University of Gothenburg,
Gothenburg, Sweden

keywords: Sea level; Egyptian Mediterranean coast; Nile Delta; Climate change

Received 9 March 2015, Accepted 23 June 2015, Available online 17 July 2015

Abstract

Future sea-level changes along the Mediterranean Egyptian coast (southern Levantine sub-basin) are projected using satellite altimetry data and model simulations. Twenty-one years (1993–2013) of satellite altimetry data, represented by dynamic topography (DT), are examined in light of tide-gauge observations. Current DT changes are examined with respect to five atmospheric/oceanic factors. The qualities of three realizations of the Geophysical Fluid Dynamics Laboratory (GFDL) model are examined by comparing these with DT. Finally, the simulations best describing the present DT are used to describe projected sea-level changes in the study area.
The results indicate that DT can be used to study coastal and deep-water sea-level changes in the study area. The southern Levantine sub-basin sea level has recently risen by an average of 3.1 cm decade-1 and exhibits significant annual sea-level variation of −17 cm to 8 cm. The sea-level variation is significantly affected by several factors: sea-level variation west of the Gibraltar Strait, steric sea level, and sea-surface temperature. The GFDL simulations best describing the recent sea level over the study area, i.e., GFDL-CM3 and GFDL-ESM2M, are used to calculate the two-model ensemble mean (GFDL-2ENM), which indicates that Egypt's Mediterranean coast will experience substantial sea-level rise (SLR) this century. The estimated uncertainty over the study area was 4–22 cm by 2100, with the emission assumptions dominating the three sources of uncertainty sources. Comparing the projected SLRs with digital elevation data indicates that Egypt's Mediterranean coast will only be safe from flooding by 2100 if effective adaptation methods are applied.
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Numerical study of wave transmission over double submerged breakwaters using non-hydrostatic wave model
Oceanologia 2015, 57(4), 308-317
http://dx.doi.org/10.1016/j.oceano.2015.07.002

Bingchen Liang1,2,*, Guoxiang Wu1, Fushun Liu1, Hairong Fan1, Huajun Li1
1 College of Engineering, Ocean University of China,
Qingdao, China;
e-mail: bingchenliang@aliyun.com
* corresponding author
2 Shandong Province Key Laboratory of Ocean Engineering, Ocean University of China,
Qingdao, China

keywords: Submerged breakwaters; Wave transmission; SWASH; Numerical simulation; Non-hydrostatic

Received 5 December 2014, Accepted 9 July 2015, Available online 23 July 2015

Abstract

In the present work, a non-hydrostatic wave model SWASH (an acronym of Simulating WAves till SHore) is used to simulate the wave transmission over double trapezoidal submerged breakwaters. The numerical results were compared with the results of the physical model. The comparison indicated the capability of SWASH model to predict the wave transmission over double submerged breakwaters. Influencing factors such as breakwater spacing S/L0, where L0 is the deep-water wavelength, and current were investigated in detail. Moreover, the effects of current on wave transmission were also analyzed. When the relative submerged depth R/H, where R is the submerged depth and H is the wave height, remains at 1.0, the appropriate relative breakwater spacing S/L0 is about 1.11. Current has no obvious effect on the appropriate S/L0, but it will change the shape of wave spectrum. Dissipation of super harmonic wave components is more obvious than that of lower harmonic wave components.
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Tidal currents in the western Svalbard Fjords
Oceanologia 2015, 57(4), 318-327
http://dx.doi.org/10.1016/j.oceano.2015.06.003

Zygmunt Kowalik1,2,*, Aleksey Marchenko2, Dmitry Brazhnikov1, Nataly Marchenko2
1School of Biological Sciences, Flinders University,
University of Alaska Fairbanks,
USA;
*corresponding author at:
Institute of Marine Science, University of Alaska Fairbanks, 118 O’Neill, P.O. Box 757220, Fairbanks, AK 99775-7220, USA. Tel.: +1 907 474 7753; fax: +1 907 474 7204.
2The University Centre in Svalbard,
Norway

keywords: Tides in Svalbard's fjords; Numerical models; Observation and model comparison; Eddy motion and nonlinear effects

Received 4 February 2015, Accepted 19 June 2015, Available online 15 July 2015

Abstract

The paper is focusing on the tides and on the strong tidal current generated in the western fjords of Svalbard. Numerical model is chosen as a tool to study the barotropic tides. Model results are compared against measured sea level and drifters. Numerical modeling and observation of tides point that the tidal amplitude does not change strongly in these fjords but the tidal currents are enhanced in several locations, namely at the entrance to the Dickson Fjord, in the narrow passages in proximity to Svea, and in the central part of Van Keulenfjorden. As the strongest currents have been found at the passages at Akseløya Island we have focused our research on this location. The narrow northern channel (Akselsundet) at Akseløya is the main waterway to Svea coal mines. Tidal currents computed and observed at the northern tip of Akseløya Island can reach amplitude from 2 to 3 m s−1. Observation of the deployed drifters and calculation of the seeded particles in the passage at Akseløya depicted a complicated pattern of eddies. The jet-like currents and eddies are quite different at the ebb and flood tide phases. As the Akseløya Island orientation relative to the shore is different for the flood and ebb waters the flow through Akselsundet is differently constrained by this geometry. The observations show that the oscillating tidal motion causes large excursions of the water particle. The drifters released in the passage during flood ended up trapped in the eddy on the eastern side of the island.
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Response patterns of phytoplankton growth to variations in resuspension in the German Bight revealed by daily MERIS data in 2003 and 2004
Oceanologia 2015, 57(4), 328-341
http://dx.doi.org/10.1016/j.oceano.2015.06.001

Jian Su1,2,*, Tian Tian3, Hajo Krasemann1, Markus Schartau1,4, Kai Wirtz1
1Institute of Coastal Research, Helmholtz-Zentrum Geesthacht,
Geesthacht, Germany;
e-mail: Jian.Su@zmaw.de
*corresponding author
2Institute of Oceanography, Centre for Marine and Climate Research, University of Hamburg,
Hamburg, Germany
3Danish Meteorological Institute,
Copenhagen, Denmark
4GEOMAR Helmholtz Centre for Ocean Research Kiel,
Kiel, Germany

keywords: Resuspension; Chlorophyll a; Phytoplankton production; Coastal sea; MERIS; German Bight

Received 20 June 2014, Accepted 17 June 2015, Available online 14 July 2015

Abstract

Chlorophyll (chl a) concentration in coastal seas exhibits variability on various spatial and temporal scales. Resuspension of particulate matter can somewhat limit algal growth, but can also enhance productivity because of the intrusion of nutrient-rich pore water from sediments or bottom water layers into the whole water column. This study investigates whether characteristic changes in net phytoplankton growth can be directly linked to resuspension events within the German Bight. Satellite-derived chl a were used to derive spatial patterns of net rates of chl a increase/decrease (NR) in 2003 and 2004. Spatial correlations between NR and mean water column irradiance were analysed. High correlations in space and time were found in most areas of the German Bight (R2 > 0.4), suggesting a tight coupling between light availability and algal growth during spring. These correlations were reduced within a distinct zone in the transition between shallow coastal areas and deeper offshore waters. In summer and autumn, a mismatch was found between phytoplankton blooms (chl a > 6 mg m−3) and spring-tidal induced resuspension events as indicated by bottom velocity, suggesting that there is no phytoplankton resuspension during spring tides. It is instead proposed here that frequent and recurrent spring-tidal resuspension events enhance algal growth by supplying remineralized nutrients. This hypothesis is corroborated by a lag correlation analysis between resuspension events and in-situ measured nutrient concentrations. This study outlines seasonally different patterns in phytoplankton productivity in response to variations in resuspension, which can serve as a reference for modelling coastal ecosystem dynamics.
full, complete article - PDF (2742 K)

Context-dependent consequences of Marenzelleria spp. (Spionidae: Polychaeta) invasion for nutrient cycling in the Northern Baltic Sea
Oceanologia 2015, 57(4), 342-348
http://dx.doi.org/10.1016/j.oceano.2015.06.002

Alexey Maximov1,*, Erik Bonsdorff2, Tatjana Eremina3, Laura Kauppi4, Alf Norkko4, Joanna Norkko4
1Zoological Institute Russian Academy of Sciences,
St. Petersburg, Russia;
e-mail: alexeymaximov@mail.ru
*corresponding author
2 Environmental and Marine Biology, Faculty of Science and Engineering, Åbo Akademi University,
Åbo, Finland
3 Russian State Hydrometeorological University,
St. Petersburg, Russia
4 Tvärminne Zoological Station, University of Helsinki,
Hanko, Finland

keywords: Bioturbation; Bioirrigation; Nutrient fluxes; Macrozoobenthos; Non-indigenous species

Received 12 January 2015, Accepted 17 June 2015, Available online 14 July 2015

Abstract

Within the framework of the possibility of using the Mediterranean pen shell Pinna nobilis in restoration and conservation plans of benthic habitats, an in situ experiment was conducted using empty P. nobilis shells. The latter were transplanted in a bare soft-bottomed area and their associated fauna were followed along 120 days and compared at different temporal points and with the assemblages living in the surrounding soft-sediment area. Compared to soft-sediment communities, an evidently increasing succession of species richness, abundance, and diversity descriptors (Shannon-Wiener H′ and Pielou's evenness J′) was observed with the community inhabiting empty Pinna shells. Among the forty-five (45) species found in association with the transplanted empty shells, seventeen (17) were found constantly in the three temporal points; the other twenty-eight (28) species appeared in the samples collected in the second and/or third sampling time. While motile and sessile species associated to Pinna shells showed an increasing pattern of appearance and abundance along the experiment time, those of soft sediment remained almost constant. The comparison between Pinna shells and soft-sediment associated communities showed that the species richness was slightly different between the two different sample types (49 for soft sediment versus 45 for empty Pinna shells); however the total abundance was found more important with empty Pinna shells. The results obtained herein argue in favor of the important engineering effect of P. nobilis in soft benthic habitats and therefore for the necessity of its conservation.
full, complete article - PDF (1357 K)

Ocean acidification and marine microorganisms: responses and consequences
Oceanologia 2015, 57(4), 349-361
http://dx.doi.org/10.1016/j.oceano.2015.07.003

Surajit Das, Neelam Mangwani
Department of Life Science, National Institute of Technology,
Rourkela, India;
e-mail: surajit@nitrkl.ac.in, surajit@myself.com

keywords: Ocean acidification; Climate change; Marine microorganisms; Ecosystem; Mesocosm

Received 24 November 2014, Revised 4 February 2015, Accepted 24 March 2015, Available online 10 April 2015

Abstract

Ocean acidification (OA) is one of the global issues caused by rising atmospheric CO2. The rising pCO2 and resulting pH decrease has altered ocean carbonate chemistry. Microbes are key components of marine environments involved in nutrient cycles and carbon flow in marine ecosystems. However, these marine microbes and the microbial processes are sensitive to ocean pH shift. Thus, OA affects the microbial diversity, primary productivity and trace gases emission in oceans. Apart from that, it can also manipulate the microbial activities such as quorum sensing, extracellular enzyme activity and nitrogen cycling. Short-term laboratory experiments, mesocosm studies and changing marine diversity scenarios have illustrated undesirable effects of OA on marine microorganisms and ecosystems. However, from the microbial perspective, the current understanding on effect of OA is based mainly on limited experimental studies. It is challenging to predict response of marine microbes based on such experiments for this complex process. To study the response of marine microbes towards OA, multiple approaches should be implemented by using functional genomics, new generation microscopy, small-scale interaction among organisms and/or between organic matter and organisms. This review focuses on the response of marine microorganisms to OA and the experimental approaches to investigate the effect of changing ocean carbonate chemistry on microbial mediated processes.
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Seasonal assessment of biological indices, bioaccumulation and bioavailability of heavy metals in mussels Mytilus galloprovincialis from Algerian west coast, applied to environmental monitoring
Oceanologia 2015, 57(4), 362-374
http://dx.doi.org/10.1016/j.oceano.2015.07.004

Omar Rouane-Hacene1,*, Zitouni Boutiba1, Benkhedda Belhaouari1, Marielle E. Guibbolini-Sabatier2, Patrice Francour2, Christine Risso-de Faverney2
1University of Oran 1- Ahmed Ben Bella, Laboratoire Réseau de Surveillance Environnementale (LRSE), Department of Biology, BP 1524 El M’naouer,
31000 Oran, Algeria;
e-mail: dag.myrhaug@ntnu.no
*corresponding author
2University of Nice-Sophia-Antipolis, EA 4228 ECOMERS, UFR Sciences, Parc Valrose, BP 71,
06108 Nice Cedex 2, France

keywords: Environmental monitoring; Biological indices; Bioaccumulation; Heavy metals; Mussels; Mediterranean Sea

Received 21 February 2015, Accepted 6 July 2015, Available online 4 August 2015

Abstract

The aim of the present work is to broaden our knowledge on the variability of trace metals in mussel tissues, focusing on seasonal fluctuations in the three different sampling sites of Algerian west coast (Oran Harbor (S1), Ain Defla (S2) and Hadjaj (S3)). For this purpose, the bioavailability (metal indices) and bioaccumulation (metal concentrations in soft tissues) of heavy metals (Zn, Cu, Pb, and Cd), and the physiological characteristics (e.g. biological indices such as condition index (CI)) of mussels Mytilus galloprovincialis have been assessed and related to seasons and sites. In S1, the highest levels of metal concentrations and indices were obtained in mussels sampled in winter for Zn, Cu and Cd, but in summer for Pb. The biological indices significantly decreased in winter. In S2, the levels of concentrations and indices of all metals varied whatever the seasons, excepting in summer where the values were the lowest. In summer and spring, the biological indices were lower than in autumn and winter. The low growth of organisms in spring and summer might be correlated to the reproductive period and the low trophic level known in S2. S3, considered as a “pristine” area, showed low metal concentrations and indices, and high biological indices, reflecting the favorable physiological conditions for the mussel growth. This approach might be used in the monitoring of the quality of coastal waters and the present work provided a useful data set for Mediterranean monitoring network.
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Characteristics of the spring/summer production in the Mecklenburg Bight (Baltic Sea) as revealed by long-term pCO2 data
Oceanologia 2015, 57(4), 375-385
http://dx.doi.org/10.1016/j.oceano.2015.07.001

B. Schneider1, S. Buecker1, S. Kaitala2, P. Maunula2, N. Wasmund1
1Leibniz Institute for Baltic Sea Research (IOW),
Warnemünde, Germany;
e-mail: bernd.schneider@io-warnemuende.de
*corresponding author
2Finnish Environment Institute (SYKE),
Helsinki, Finland

keywords: Mecklenburg Bight; CO2 partial pressure; Spring bloom; Nitrogen fixation

Received 18 March 2015, Accepted 8 July 2015, Available online 22 July 2015

Abstract

Automated CO2 partial pressure, pCO2, measurements were performed on a cargo ship that commutes between the Gulf of Finland and the Mecklenburg Bight in the southwest of the Baltic Sea. The data from 2004 to 2014 along a sub-transect in the Mecklenburg Bight are used to analyze the timing and intensity of the net community production (NCP). The start of the spring bloom, identified by the first continuous drop of the pCO2 below the atmospheric level, spanned from mid-February to mid-March. Converting the pCO2 decrease during spring to changes in the total CO2 concentration and taking into account air-sea gas exchange, the spring NCP was determined. The NCP increased by about 80% during 2004–2014, the mean amounted to 40 μmol L-1. In two years a distinct second pCO2 minimum in mid-summer succeeded the minimum in spring. This was attributed to production fuelled by nitrogen fixation since the nitrate concentrations were virtually zero and since the atmospheric deposition could not satisfy the NCP nitrogen demand. Furthermore, investigations of the plankton composition revealed a cyanobacteria biomass peak in the year with the highest mid-summer NCP. Based on the calculation of the mid-summer NCP in the two particular years and on the C/N ratio of particulate organic matter, the corresponding nitrogen fixation activity was calculated. These values and the analysis of the relationship between the integrated NCP and temperature indicated that the nitrogen fixation activity in the Mecklenburg Bight was by a factor 3–4 lower than in the central Baltic Sea.
full, complete article - PDF (1179 K)