Oceanologia No. 59 (2) / 17
Original research article
Epibenthic diversity and productivity on a heavily trawled Barents Sea bank (Tromsøflaket): Monika Kędra, Paul E. Renaud, Hector Andrade
Wave-induced bottom shear stress estimation in shallow water exemplified by using deep water wind statistics: Dag Myrhaug
Possible means of overcoming sedimentation by motile sea-picoplankton cells: Oleh Pundyak
On the buoyant sub-surface salinity maxima in the Gulf of Riga: Taavi Liblik, Maris Skudra, Urmas Lips
Morphometric variations in white seabream Diplodus sargus (Linneus, 1758) populations along the Tunisian coast: Myriam Kaouèche, Lilia Bahri-Sfar, Ibtissem Hammami, Oum Kalthoum Ben Hassine
Current observations from a looking down vertical V-ADCP: interaction with winds and tide? The case of Giglio Island (Tyrrhenian Sea, Italy): Laura Cutroneo, Gabriele Ferretti, Davide Scafidi, Gian Domenico Ardizzone, Greta Vagge, Marco Capello
Spatio-temporal variability of the phytoplankton biomass in the Levantine basin between 2002 and 2015 using MODIS products: Roy El Hourany, Ali Fadel, Elissar Gemayel, Marie Abboud-Abi Saab, Ghaleb Faour
Toward downscaling oceanic hydrodynamics – suitability of a high-resolution OGCM for describing regional ocean variability in the South China Sea: Meng Zhang, Hans von Storch
Original research article
Epibenthic diversity and productivity on a heavily trawled Barents Sea bank (Tromsøflaket)
Oceanologia 2017, 59(2), 93-101
Monika Kędra1,*, Paul E. Renaud2, Hector Andrade3
1Institute of Oceanology of the Polish Academy of Sciences, Sopot, Poland;
2Akvaplan-niva; Fram Centre for Climate and the Environment, Tromsø, Norway
3University Centre in Svalbard, Longyearbyen, Norway
Epibenthos; Benthic secondary production; Shallow banks; Trawling impacts
Received 12 August 2016, Accepted 13 December 2016, Available online 24 December 2016
Shallow Arctic banks have been observed to harbour rich communities of epifaunal organisms, but have not been well-studied with respect to composition or function due to sampling challenges. In order to determine how these banks function in the Barents Sea ecosystem, we used a combination of video and trawl/dredge sampling at several locations on a heavily trawled bank, Tromsøflaket – located at the southwestern entrance to the Barents Sea. We describe components of the benthic community, and calculate secondary production of dominant epifaunal organisms. Forty-six epibenthic taxa were identified, and sponges were a significant part of the surveyed benthic communities. There were differences in diversity and production among areas, mainly related to the intensity of trawling activities. Gamma was the most diverse and productive area, with highest species abundance and biomass. Trawled areas had considerably lower species numbers, and significant differences in epifaunal abundance and biomass were found between all trawled and untrawled areas. Trawling seems to have an impact on the sponge communities: mean individual poriferan biomass was higher in untrawled areas, and, although poriferans were observed in areas subjected to more intensive trawling, they were at least five times less frequent than in untrawled areas.
Wave-induced bottom shear stress estimation in shallow water exemplified by using deep water wind statistics
Oceanologia 2017, 59(2), 102-107
Department of Marine Technology, Norwegian University of Science and Technology (NTNU), Trondheim, Norway;
Random waves; Bottom friction; Large bed roughness; Erosion and deposition of mud; Wind statistics
Received 9 June 2016, Accepted 16 September 2016, Available online 4 October 2016
The paper provides a simple and analytical method which can be used to give estimates of the wave-induced bottom shear stress for very rough beds and mud beds in shallow water based on wind statistics in deep water. This is exemplified by using long-term wind statistics from the northern North Sea, and by providing examples representing realistic field conditions. Based on, for example, global wind statistics, the present results can be used to make estimates of the bottom shear stress in shallow water.
Possible means of overcoming sedimentation by motile sea-picoplankton cells
Oceanologia 2017, 59(2), 108-112
Botanical Garden of Ukrainian National Forestry University, Lviv, Ukraine;
2ODE-DYNECO-PELAGOS, Ifremer, Centre de Bretagne, Technople Brest-Iroise, Plouzané, France
Picoplankton; Sedimentation; Gravikinesis; Friction anisotropy; Antipredator behavior
Received 17 May 2016, Accepted 16 September 2016, Available online 5 October 2016
A model for overcoming the gravity by sea-picoplankton cells is proposed here. It is based on different means of escaping from potential predators used by cells of co-existing picoplankton species. These different means cause friction anisotropy of motile cells with strong antipredator behavior (AB). According to equations of stochastic movement used in this model for picoplankton cells with strong AB, collocated with high concentration of cells with weak or absent AB, the sedimentation can be considerably overcome.
On the buoyant sub-surface salinity maxima in the Gulf of Riga
Oceanologia 2017, 59(2),113-128
Taavi Liblik1,*, Maris Skudra1,2, Urmas Lips1
1Marine Systems Institute, Tallinn University of Technology, Tallinn, Estonia;
2 Latvian Institute of Aquatic Ecology, Riga, Latvia
Salinity; Thermocline; Gulf of Riga; Water exchange; Intrusion
Received 1 August 2016, Accepted 7 October 2016, Available online 23 October 2016
Thermohaline structure in the Gulf of Riga (GoR) was investigated by a multi-platform measurement campaign in summer 2015. Stratification of the water column was mainly controlled by the temperature while salinity had only a minor contribution. Buoyant salinity maxima with variable strength were observed in the intermediate layer of the Gulf of Riga. The salinity maxima were likely formed by a simultaneous upwelling–downwelling event at the two opposite sides of the Irbe strait. The inflowing salty water did not reach the deeper (> 35 m) parts of the gulf and, therefore, the near-bottom layer of the gulf remained isolated throughout the summer. Thus, the lateral water exchange regime in the near bottom layer of the Gulf of Riga is more complicated than it was thought previously. We suggest that the occurrence of this type of water exchange resulting in a buoyant inflow and lack of lateral transport into the near-bottom layers might contribute to the rapid seasonal oxygen decline in the Gulf of Riga.
Morphometric variations in white seabream Diplodus sargus (Linneus, 1758) populations along the Tunisian coast
Oceanologia 2017, 59(2), 129-138
Myriam Kaouèche*, Lilia Bahri-Sfar*, Ibtissem Hammami*, Oum Kalthoum Ben Hassine*
Département de Biologie, Unité de Recherche Biologie Intégrative et Ecologie Fonctionnelle et Evolutive des milieux Aquatiques, UR11ES08, Faculté des Sciences de Tunis, Université Tunis El Manar, Tunisia;
Morphometric variation; Diplodus sargus; Siculo-Tunisian Strait; Ecological features
Received 11 August 2015, Accepted 8 August 2016, Available online 21 August 2016
Morphometric characters of the white seabream Diplodus sargus (Linnaeus 1758) were compared among samples collected from six marine and lagoon sites along the Tunisian coast to elucidate the impact of the geographical barrier of the Siculo-Tunisian Strait and/or the lagoon environment in the morphological variation among the Tunisian white seabream population. Two morphometric descriptors (twenty-five Truss elements and six traditional measurements) were used to study the pattern of this morphological variation. Univariate analysis of variance revealed significant differences (P < 0.001) for both traditional and Truss variables. Multivariate analysis using the two morphometric descriptors detected a clear variation in the body shape between D. sargus populations along the Tunisian coast. All these analyses showed the distinctness of the sample from El Biban lagoon compared to the remaining ones. This discrimination was due to the head and the peduncle of the studied fish. Varying degrees of differences were also observed between northern and southern samples, and between the lagoon and the marine samples. The morphological variations of the head explain also the discrimination between the different lagoons samples. Observed morphological heterogeneity seems to be related to the impact of ecological factors.
Current observations from a looking down vertical V-ADCP: interaction with winds and tide? The case of Giglio Island (Tyrrhenian Sea, Italy)
Oceanologia 2017, 59(1), 139-152
Laura Cutroneoa1, Gabriele Ferrettia1, Davide Scafidia1, Gian Domenico Ardizzoneb2, Greta Vaggea1, Marco Capello1,*
1DISTAV, University of Genoa, Genoa, Italy;
2“Sapienza”, University of Rome, Rome, Italy
Currents; Wind interactions; Sea level; Normalised Cross-Correlation Function
Received 22 July 2016, Accepted 23 November 2016, Available online 14 December 2016
In the context of the environmental monitoring of the Concordia wreck removal project, measurements of currents, winds and sea level height were made along the eastern coast of the Giglio Island, Tyrrhenian Sea (Italy), during 2012–2013. The aim of the study was to investigate the effect of atmospheric forcing and periodic sea-level changes on the coastal currents. Normalised Cross-Correlation Function analysis allowed us to correlate these observations. A marked inter-seasonal variability was found in both current and local wind velocity observations but a significant level of correlation between the data was only found during strong wind events. Current and wind directions appeared to be uncorrelated and current measurements showed a predominant NW–SE direction, presumably linked to the shape and orientation of Giglio Island itself. During strong winds from the SSE, current flow was towards the NNW but it suddenly switched from the NNW to the SE at the end of wind events. The results show that, at Giglio Island, currents are principally dominated by the general cyclonic Tyrrhenian circulation, and, secondly, by strong wind events. The sea level had no effects on the current regime.
Spatio-temporal variability of the phytoplankton biomass in the Levantine basin between 2002 and 2015 using MODIS products
Oceanologia 2017, 59(2), 153-165
Roy El Hourany1, Ali Fadel1, Elissar Gemayel2, Marie Abboud-Abi Saab2, Ghaleb Faou1,*
1National Center for Remote Sensing, National Council for Scientific Research (CNRS), Beirut, Lebanon;
2National Center for Marine Sciences, National Council for Scientific Research (CNRS), Batroun, Lebanon
Mediterranean Sea; Levantine basin; Remote sensing; MODIS; Phytoplankton bloom; Chlorophyll-a
Received 13 May 2016, Accepted 25 December 2016, Available online 6 January 2017
The Levantine basin in the Eastern Mediterranean Sea is subject to spatial and seasonal variations in primary production and physical-chemical properties both on a short and long-term basis. In this study, the monthly means of daily MODIS product images were averaged between 2002 and 2015, and used to characterize the phytoplankton blooms in different bioregions of the Levantine basin. The selected products were the sea surface temperature (SST), the chlorophyll-a concentration (Chl-a), the diffuse attenuation coefficient for downwelling irradiance at 490 nm (Kd_490) and the colored dissolved organic matter index (CDOM_index). Our results showed that phytoplankton blooms were spatially and temporally variable. They occurred in late autumn at the Nile Delta, in early spring and late summer at the eastern coastline, and in spring at the northeastern coastline. The northern coastline and the open water had a common bloom occurring in winter. The Nile Delta was found to be the most productive area of the Levantine basin showing high Chl-a. Kd_490 and Chl-a present a parallel co-variation indicating a dominance of Case 1 waters in the Levantine basin. The CDOM_index shows a phase shift with the Chl-a fluctuation. A strong inverse correlation was observed between both Chl-a and CDOM_index with SST, connoting an indirect relation represented by a depression of CDOM in summer by photobleaching, and a suppression of the chlorophyll-a concentration due to water stratification, together with nutrient stress. An overestimation of the Chl-a values had been signaled by the use of the CDOM_index, suggesting a correction plan in a latter study.
Toward downscaling oceanic hydrodynamics – suitability of a high-resolution OGCM for describing regional ocean variability in the South China Sea
Oceanologia 2017, 59(2), 166-176
Meng Zhang*, Hans von Storch
Institute for Coastal Research, Helmholtz Zentrum Geesthacht, Geesthacht, Germany;
Ocean downscaling; STORM; The South China Sea
Received 22 June 2016, Accepted 4 January 2017, Available online 18 January 2017
We suggest to transfer the empirical downscaling methodology, which was developed mostly for atmospheric dynamics and impacts, to regional ocean problems. The major problem for doing so is the availability of decades-long and homogeneous and spatially detailed data sets. We have examined the performance of the STORM multidecadal simulation, which was run on a 0.1° grid and forced with 1950–2010 NCEP re-analyses, in the South China Sea and found the data suitable. For demonstration we build with this STORM-data downscaling model for the regional throughflow.
The STORM data is compared with AVISO satellite observations and the ocean re-analysis dataset C-GLORS. We find the seasonal patterns and the inter-annual variability of sea surface height anomaly in both the C-GLORS data and the STORM simulation consistent with the AVISO-satellite data. Also the strong westward intensification and the seasonal patterns of South China Sea circulation steered by the monsoon have been presented well. As an important indicator of vertical movement, the sea surface temperature distribution maps are also very close, especially for the narrow upwelling region in summer. We conclude that the output of the STORM simulation is realistically capturing both the large-scale as well as the small-scale dynamical features in the South China Sea.
Microorganisms associated with charophytes under different salinity conditions
Oceanologia 2017, 59(2), 177-186
Marija Kataržytė*, Diana Vaičiūtė, Martynas Bučas, Greta Gyraitė, Jolita Petkuvienė
Marine Science and Technology Centre, Klaipeda University, Klaipėda, Lithuania;
Net primary production of charophytes; Abundance of bacteria and fungi; Taxa composition of fungi; Freshwater and brackish water; Curonian Lagoon; Baltic Sea
Received 17 August 2016, Accepted 21 October 2016, Available online 4 November 2016
Microorganisms associated with aquatic macrophytes can in various ways interact with a plant and influence its activity and vice versa. A low-salinity intrusion into freshwater environment can affect plant-microorganism interactions. In this study, effects of different salinity conditions on the abundance and community composition of associated microorganisms with charophytes in the Curonian Lagoon were assessed. From the results, we found that short term salinity changes affected the abundance of bacteria and fungi associated with charophytes, whereas no response was reflected in the taxa composition of fungi, showing that other factors could be of more importance. The increased fungi abundances and different fungi composition in August in comparison to June was probably related to senescence process of aquatic vegetation. 8 fungi taxa were isolated and identified in association with charophytes, while higher diversity was revealed by DGGE technique.
Oceanographic observations in the Nordic Sea and Fram Strait in 2016 under the IO PAN long-term monitoring program AREX
Oceanologia 2017, 59(2), 187-194
Waldemar Walczowski*, Agnieszka Beszczyńska-Möller, Piotr Wieczorek, Małgorzata Merchel, Agata Grynczel
Institute of Oceanology, Polish Academy of Sciences, Sopot, Poland;
Nordic Seas; Physical oceanography; Atlantic water
Received 13 December 2016, Accepted 25 December 2016, Available online 13 January 2017
Since 1987 annual summer cruises to the Nordic Seas and Fram Strait have been conducted by the IO PAN research vessel Oceania under the long-term monitoring program AREX. Here we present a short description of measurements and preliminary results obtained during the open ocean part of the AREX 2016 cruise. Spatial distributions of Atlantic water temperature and salinity in 2016 are similar to their long-term mean fields except for warmer recirculation of Atlantic water in the northern Fram Strait. The longest observation record from the section N along 76°30′N reveals a steady increase of Atlantic water salinity, while temperature trend depends strongly on parametrization used to define the Atlantic water layer. However spatially averaged temperature at different depths indicate an increase of Atlantic water temperature in the whole layer from the surface down to 1000 m.