Resumo em Inglês:

Abstract Understanding the dynamics of microbial plankton communities, their metabolic processes and taxonomic composition in oligotrophic ocean basins has been one of the central tasks of contemporary marine microbial ecology and one of the main challenges in a changing global ocean. However, despite its ecological importance, the South Atlantic Subtropical Gyre (SASG) remains poorly understood in relation to marine microbes, which comprise the major drivers of biogeochemical cycles and the largest carbon sink to the deep ocean. This review presents the state of the art of microbial ecology in the SASG, including the adjacent oligotrophic region, the Southwest Atlantic Ocean (SWAO). We have also addressed the theoretical and methodological trends in this field since 1970s, focusing on the main milestones that led to the more-detailed current knowledge of the role of oligotrophic gyres in the global carbon cycle. Finally, we discussed the general patterns of microbial community composition in the SASG, focusing on their potential responses to environmental factors. In spite of increasing efforts to investigate this region, SASG is among the least known oceanic provinces, which has hampered the debate over whether the oligotrophic ocean acts as a sink or source of CO2 into the atmosphere.

Resumo em Inglês:

Abstract Modern coastal environments are considered highly selective and dynamic, not only due to the natural variability of physical and chemical parameters, but also because of anthropogenic contamination. Our study aims to identify environmental and/or anthropogenic factors influencing benthic foraminiferal abundances over a period of one year in the Tramandaí-Armazém Lagoon, southern Brazil. Assemblages were composed exclusively of agglutinated species assigned to the genera Trochammina, Trochamminita, Ammotium, Haplophragmoides and Miliammina. Total abundances varied throughout the year, reaching the highest values during the wetter months of March and July, when living and dead assemblages became dominated by Ammotium salsum. This pattern is likely related to salinity fluctuations due to changes in freshwater input that, consequently, affected the amount of organic matter (e.g., phytodetritus) brought into the lagoon by surrounding drainages. To assess the impact of anthropogenic pollution, we evaluated total relative abundances of deformed tests in the Tramandaí-Armazém Lagoon. Relative abundances of deformed tests were the highest during the months of January and March, when contaminant (e.g., sewage) discharge was probably increased due to the seasonal population growth in the region.

Resumo em Inglês:

Abstract The Cananéia-Iguape lagoon-estuarine system, where the Ilha Comprida barrier (IC) is located, is one of the most dynamic coastal areas on the southeastern Brazilian coast. IC island is a 63 km-long barrier and it is limited by the Icapara inlet to the north, and the Cananéia inlet to the south. This system has been affected by intense changes in its morphology since the opening of the Valo Grande artificial channel in 1852 A.D., connecting the nearby Ribeira de Iguape river to the Mar Pequeno lagoon. In this context of anthropogenic disturbance on the coastal systems, the objective of this study is to understand the active mechanisms, both natural and anthropogenic, controlling the morphological changes of the northeastern portion of the IC, from monthly as well as centenary timescales. We analyzed successional addition and erosion of beach ridges using a multi-temporal dataset obtained by Optically Stimulated Luminescence, aerial photos (1962 and 2000), satellite images (1980-2016) and GNSS surveys (2015-2017). The results were compared to climatic (rainfall and waves) data. Northeastward migration rates of the IC ranged from 15.5 m/y, on the GNSS surveys, to 154 m/y, calculated based on OSL rates. Changes on rates on the northeastward inlet migration barrier are related to anthropogenic interference, mainly the Valo Grande opening and climate changes. Sediment accumulation occurred mainly during the summer on the baymouth spits. This depositional scheme is consistent with the highest values of Ribeira de Iguape river flow and the low synergy of waves coming from the South. By contrast, the retrogradation of the coastline occurs in the winter, when the wave power is stronger than in the summer. This seasonal configuration is controlled both by the bidirectional longshore drift and by the fluvial discharge.

Resumo em Inglês:

Abstract The objective of this study was to evaluate variations in the composition and abundance of the phytoplankton community after an exceptional harmful bloom of Akashiwo sanguinea that occurred in Todos os Santos Bay (BTS) in early March, 2007. Samples were collected every ten days, between April, 2007 and March, 2008, from the estuarine gradient of the Paraguaçu River to BTS. The physical and chemical variables were measured in situ using a multiparameter sensor. Water samples were collected for analysis of the dissolved inorganic nutrient concentrations and for the study of composition and abundance of the microphytoplankton. Overall, 135 taxa were identified, with a higher richness of diatoms. The total cell density ranged from 2.92 × 103 to 1.16 × 107 (5.47 × 105 ± 1.69 × 106) cells L−1, with higher values in the freshwater zone than in the marine area. Five species showed peaks of abundance throughout the study, forming small blooms. Four of these blooms occurred in the rainy season, formed by the species Guinardia striata (April, 2007), Scrippsiella cf. acuminata (August, 2007), Euglena gracilis (August, 2007), and Skeletonema cf. costatum (September, 2007), while a new bloom of the species Akashiwo sanguinea occurred during the dry season (December, 2007). The environment was typically oligotrophic, with low spatiotemporal variation in the concentrations of dissolved nutrients. Even so, we observed short-term variations in the structure and composition of the phytoplankton community, demonstrated by rapid bloom events, followed by an increase in the total abundance of microphytoplankton, especially during the rainy season. The blooms did not cause any notable changes in the water column and did not present any harmful effects on the system.

Resumo em Inglês:

Abstract A performance evaluation of ocean color chlorophyll-a algorithms was conducted based on the in situ fluorescence chlorophyll concentration (Fchl) measured by a sensor on the buoy SiMCosta-SC01 in coastal waters of South Brazil. The operational algorithms are used in MODIS and VIIRS sensors to derive satellite chlorophyll concentration (Csat). Fchl values were successfully corrected for nonphotochemical quenching (NPQ) by an interpolation of sunrise and sunset daily measurements. A laboratory-derived calibration coefficient was applied to convert the unquenching Fchl values into chlorophyll concentration (Cflu). Overall, linear regression analysis between Cflu and Csat for both sensors showed good results, with the coefficient of determination (R2) varying between 0.88 and 0.96, slopes between 0.92 and 1.02 and intercepts between -0.17 and 0.13. The MODIS algorithm (R2 = 0.96, slope = 1.02, RMSE = 0.16 mg m-3, BIAS = 0.16 mg m-3, for N = 222 and time interval ±1 h) presented slightly better performance than VIIRS (R2 = 0.92, slope = 0.96, RMSE = 0.25 mg m-3, BIAS = -0.25 mg m-3, for N = 284 and time interval ±1 h). These results represent the most comprehensive satellite data analysis for this region, suggesting that the approach may be applicable to other SiMCosta buoys.

Resumo em Inglês:

Abstract Scomberomorus brasiliensis is the most important fish species of the small-scale fishery off the southwestern Atlantic north of the La Plata estuary. For management purposes, this study evaluated their reproductive biology, size, age and growth along the Paraná coast. Monthly samples (March 2018-June 2020) from the fishery comprised 933 specimens (413 males, 520 females), 210-779 mm fork length, corresponding to a size smaller than in the northern areas. It presented negative allometry (b = 2.69159, length-weight relationship). Specimens in all stages of maturity occurred during the study period, indicating spawning in the area from October to June, peaking from January to March. The gonad-length relationship was suitable to confirm this assessment. Individual fecundity varied between 34,484 and 390,786 oocytes. Maturity occurred at L50 = 446.46 mm, t50 = 1.4 years, and L100 = 588.79 mm, and t100 = 2.3 years. The growth parameters were L∞ = 771.68 mm, k = 0.65 year-1 and t0 = -0.102 years, with cohorts aged from 0.5 to 6.5 years. Scomberomorus brasiliensis along the Paraná coast constitutes a self-sustaining group, not directly related to that from northeastern Brazil. This small-scale fishery is not currently negatively affecting stock level; it is essential to monitor these attributes to detect future changes or impacts.

Resumo em Inglês:

Abstract New records of the introduced solitary ascidians, Ciona robusta and Rhodosoma turcicum, have been added to the southwestern Atlantic Ocean, from Cabo Frio to Ilha Grande Bay, Brazil, in surveys conducted since 2009. Both species occurred on natural and artificial substrates, in predator-protected habitats, and regions close to harbors or other maritime activities. The distribution of Ciona robusta was related to water temperature, influenced by upwelling intensity and temperatures below 25ºC, while R. turcicum was not sensitive to the range of recorded water temperatures. The occurrence of both species on sites close to maritime terminals suggests vessels as potential vectors.

Resumo em Inglês:

Abstract The Bacanga River Estuary is socioeconomically important due to artisanal fishing and aquaculture. It is blocked by a dam and is under human pressure along its drainage basin, intensifying the eutrophication process. This study reports on the occurrence of phytoplankton blooms and trophic state (TSI and TRIX) at six sampling sites during the annual cycle. The estuary was divided into downstream and upstream regions. Higher salinity, turbidity, depth, and lower dissolved oxygen levels were found downstream; whereas, high levels of chlorophyll a and nutrient concentrations were observed in both regions. There were blooms of Leptocylindrus danicus (1.45 × 106 cells L-1) and Skeletonema costatum (1.89 × 106 cells L-1) downstream; whereas phytoflagellate proliferation, such as those of Chlamydomonas sp. (13.17 × 106 cells L-1), Euglena gracilis (7.84 × 106 cells L-1), and Euglena proxima (1.03 × 106 cells L-1) were recorded upstream, with Chlamydomonas sp. as the discriminant species of this zone. Both trophic indices (TSI; TRIX) indicated elevated trophic conditions for the estuary, classifying it as hypereutrophic. Nevertheless, TSI only showed a significant relationship with some specific phytoplankton blooms. Thus, TSI seems to be the trophic index with a better response in the assessment of estuarine ecological functioning.

Resumo em Inglês:

ABSTRACT Extreme climate events cause major disturbances to the fauna of sandy beaches. For abiotic-controlled species, storm waves play a significant role in controlling populations. Considering the projected increase in the frequency of extreme climate events and the consequential influence on benthic macrofauna, there is a need to adjust the time-scale of observations. In this context, we conducted weekly monitoring of the ghost crab Ocypode quadrata on an urbanized sandy beach in southeast Brazil to evaluate the effect of storm waves on population dynamics. The effect of storm wave events was not as strong as expected, but two of the 8 registered storm events provoked an increase in density of O. quadrata. Although not significant, after events 4-5, the population suffered a decrease in density and burrows were concentrated in the upper supralittoral, probably because of contiguous effect of habitat reduction by trampling and the storm waves. It is probable that the combination of storm wave events in conjunction with urbanization could have prevented the population recovery by reducing the overall recruitment or even causing mortality or migration towards safer areas. Multi-factor approaches are needed to better understand the dynamics of O. quadrata in urbanized beaches, however, our study showed that weekly monitoring allowed us to record subtle variations in population dynamics that would go unregistered with other approaches but might reveal long-term changes.

Resumo em Inglês:

ABSTRACT We investigate the distribution of the wave power around the Alcatrazes island, a protected marine reserve in southeastern Brazil, located at 20 nautical miles from the coast of São Sebastião/SP. A 14-year wave time series (2005-2018) extracted from the global WaveWatch III model, was used to obtain the offshore wave climate. Based on the wave climate, a wave propagation model (Delft3D) was applied in order to obtain nearshore information. The most frequent waves are from the east, southeast and south, with heights between 1.0 and 2.0 m and periods of 7 to 10 s. Due to dominant wave direction incidence, the wave power is higher at the more exposed eastern side of the island, with its lee side becoming shadowed from the main wave trains. Magnitudes vary seasonally, with winter and autumn presenting more energetic southerly waves and consequent higher wave power along the rocky island. The wave power distribution is a consequence of the incident wave characteristics and the geomorphology of the island. Our findings are the first assessment of the local wave climate and wave power distribution along the rocky shores of Alcatrazes island, providing important background information for understanding different aspects of its functioning and management.

Resumo em Inglês:

Abstract Five demosponges belonging to the order Axinellida: Axinella corrugata, Dragmacidon alvarezae, Dragmacidon reticulatum, Ptilocaulis walpersi, Myrmekioderma rea and one sponge belonging to the order Scopalinida: Scopalina ruetzleri were analyzed to assess their fatty acid composition in the phospholipid fraction. Additionally, the seasonal and intraspecific variation in fatty acids composition was assessed in M. rea and D. alvarezae. Fatty acid identification was conducted using an HRGC-MS with an ECL value of methyl ester derivatives, and analyzing their mass spectra. To confirm double bound location, N-acylpyrrolidide derivatives were used studying their mass spectra. In total, 83 fatty acids were identified with chain lengths ranging from C14 to C32. Interestingly, brominated fatty acids were identified, previously suggested for sponges. Polybranched fatty acids such as 4,8,12-trimethyltridecanoic acid (4,8,12-TMTD) and 3,7,11,15-tetramethylhexadecanoic (phytanic acid) were found, without a clear distribution pattern. A predominance of iso-acids (i-15:0 and i-17:0) on anteiso acids were observed. Some seasonal variations in fatty acid (FA) compositions for M. rea and D. alvarezae were observed. The hierarchical Clusters Analysis (HCA) showed that the FA composition was species-specific but not informative at the family or order level.

Resumo em Inglês:

Abstract Artificial reefs (ARs) have been deployed on the inner shelf of Paraná, Southeast Brazil, as protection against destructive trawling activities, and to offer habitat for local fauna for recovery of biodiversity. The purpose of this study was to develop a preliminary characterization of the ichthyoplankton community associated with both artificial and natural reefs in the Currais Archipelago, and perform a comparison of fish larvae composition between ARs and nearby unconsolidated substrate. Two sampling methods were used, light traps and a plankton net. A total of 12 families and 14 species were identified, expanding the total species list in the area by eight species and three families. Differences among assemblages on ARs and unconsolidated substrate indicate that ARs seem to be effective attractors to fish larvae. Particular attention is drawn in regard to the "attractor effect" for exotic species that do not naturally reside in the area, such as Omobranchus punctatus. The large abundance of fish eggs on ARs suggests that these artificial structures can improve local production. These results are the first step needed to better define guidelines for sustainable use and management of ARs and Currais Archipelago, a Marine National Park.

Resumo em Inglês:

ABSTRACT During recent decades, different formulas have been developed to estimate longshore sediment transport rates through calibration using a wide variety of datasets, applicable for a range of particular wave and beach conditions. The equations that have shown the best capability to predict Bulk Longshore Sediment Transport Rate (BLSTR) are the formulas derived by CERC and by Kamphuis. In the present study, the five process parameters as used in the Kamphuis formula are accepted. The CERC formula includes only two of the five process parameters used in Kamphuis’ formula. A renewed optimization to derive the power of the five Kamphuis’ process parameters using an extensive dataset by Bayram was performed by Mil-Homens. In addition to this valuable effort, our contribution introduces two innovations. Firstly, the power coefficients of the five Kamphuis process parameters are optimized using a broad range of meta-heuristic algorithms. Secondly, the optimization is not based on the Bayram dataset as carefully collected and reviewed from published manuscripts but on a methodologically more homogeneous Iranian dataset acquired for port design and port management purposes. Independently from the results by Mil-Homens derived from the Bayram dataset, our study confirms these findings based on a totally different dataset. Specifically, the weaker impact of wave period and the stronger impact of the median grain diameter are in accordance with each other. The latter finding provides a stronger support for the mutual cancellation of the impact of slope and grain diameter in BLSTR, lending explanatory support to the CERC formula once beach slope and grain size are not known.

Resumo em Inglês:

Abstract The datum for sounding reduction is a permanently fixed surface, to which the depths displayed on the nautical charts and the tide tables heights refer. The International Hydrographic Organization recommends adopting the lowest astronomical tide as a chart datum, although its calculation can be complex because it varies both spatially and temporally. The ever increasing accuracy of 3D positioning with Global Navigation Satellite Systems requires that the chart datum is referenced to the ellipsoid WGS84. The aims of this paper are to calculate the lowest astronomical tide and to develop an empirical model to determine the distance between the lowest astronomical tide and the WGS84 ellipsoid, for a region of the Southwest Atlantic Ocean between latitudes 36°S and 54°S and longitude 54°W, on a 5km x 5km grid. Harmonic constants from the Centre for Topographic studies of the Oceans and Hydrosphere are used to calculate the lowest astronomical tide. To refer it to the WGS84 ellipsoid, results from mean sea level models and along-track sea level heights provided by Archiving, Validation and Interpretation of Satellite Oceanographic data are utilized. The final product has been designed for open waters and will be useful both for the development of relevant marine activities in the area, as well as to increase the efficiency of hydrographic surveys while contributing to more precise navigation in critical areas.

Resumo em Inglês:

ABSTRACT The objective of this study is to compare the physical characteristics of circulation, salinity structure and transport in the Itajaí-Açu and Itajaí-Mirim estuaries. Due to its importance, the Itajaí-Açu estuary has been studied in the last decade. However, its main tributary, the Itajaí-Mirim has never been assessed, especially as an opportunity to comparatively investigate the flow behavior of salt wedge estuaries with different widths and depths. Field data were acquired during two campaigns that covered the complete semi-diurnal tidal regimes during spring and neap tides. Water level, total transport volume, current and salinity were recorded hourly and synoptically at cross-sections in each estuary. The campaigns were conducted during a prolonged period of low river discharge. The tidal range during the spring and neap tide campaigns were of approximately 1.2 and 0.4 m, respectively. At the Itajaí-Açu and Itajaí-Mirim cross-sections, the peak ebb and flood currents were -0.8 and -0.6 m s-1 and 0.8 and 0.4 m s-1, respectively, during the spring tide campaign, and classified as well mixed and highly stratified estuaries, respectively. During the neap tide campaign, both estuaries were classified as salt wedge. The dominant mechanism was the salt transport by advection due to fluvial advection in both estuaries and campaigns. The landwards salt transport, which resulted from dispersive processes, was only important during neap tide for the Itajaí-Açu estuary.

Resumo em Inglês:

Abstract The Itapessoca estuary is part of the Itamaracá-Itapessoca Estuarine System, a ria-type estuary located on the northeast Brazilian shore, in the state of Pernambuco. Here we present an assessment of the estuarine circulation, suspended sediment dynamics, and its main transport mechanisms. We carried out a field survey where water level, currents, salinity, temperature, and suspended sediment concentration (SSC) were recorded at 10-minute intervals during two complete semi-diurnal tidal cycles under spring tide conditions. The field survey was conducted in September (2012), which is a transitional period between wet and dry seasons. The water level displayed symmetrical ebb-flood phases; however, currents were ebb-dominated. The freshwater contribution was negligible, and the mean salinity was ~35 g/kg, which is slightly lower than the adjacent shelf values (36.5 g/kg). The SSC transport was driven by the ebb-dominated tidal currents, with the highest values of ~30 mg/l occurring during the peak current during the ebb. The source of the suspended sediment was the erosion from the bottom, and the concentration was much lower than other similar estuaries (e.g., Caravelas). This observation suggests this system is a ‘sediment starved system’ in the sense that it presents a low concentration of suspended sediment.

Resumo em Inglês:

Abstract The present study aims to investigate the variability of catches by trawling fleet vessels licensed to operate under the ‘diverse fish’ license in relation to the depth gradient and the hydrological cycle of the Amazon River. For this purpose, vessels operating in this category were accompanied by on-board observers on the inner Amazon shelf, during January, April and July 2013 and in April, May, August and September 2014. A total of 115,505 kg of fish was harvested, distributed among 22 species. The flood period was the most representative, with a total of 43,122 kg, followed by the ebb period (28,749 kg), the rainy period (23,171 kg) and the dry period (20,424 kg). Kingfish (Macrodon ancylodon) was the most abundant fish in all seasons (79.7%). Significant differences were observed in fish composition in relation to the depth gradient and hydrodynamics of the Amazon River, with higher richness and diversity (Margalef index) during flood periods and at greater depths throughout the study period. We also observed a significant interaction between river flow and depth category, with more diversified fish fauna attributed to ebbs and floods in shallow and deep waters at the mouth of the Amazon River. Considering that the license for ‘diverse fish’ was established as an alternative to fishing for marine shrimp in closed season, the need for effective monitoring of this fishing system is reiterated for an efficient assessment of the impacts in the fish community structure.

Resumo em Inglês:

Abstract The detection of cytochrome P450 1A in S. rivulatus liver and gills was used as a biomarker for the exposure to polyaromatic hydrocarbons (PAHs) as organic pollutants along the Bay of Alexandria, Egypt. PAHs were determined in both sediment and S. rivulatus tissues in Abu Qir Bay, Alexandria as a test area and the Matrouh coast as a control area. High levels of PAHs in Abu Qir Bay area and ratios of specific PAH compounds indicate the petrogenic origin of hydrocarbons. Both antioxidant activity and oxidative stress markers increased significantly. The protein expression of P450 1A in the liver and gill of S. rivulatus was markedly induced. Moreover, the toxicity in fish organs was supported by histopathological observations. These data suggest correlation between bioaccumulated PAH and P450 1A induction and provide strong evidence of the importance of P450 1A as a biomarker of the exposure of S. rivulatus to xenobiotics.

Resumo em Inglês:

Abstract Important global oceanic processes, such as the meridional overturning circulation, are governed by the temperature and salinity of the ocean. As such, it is essential that these properties be correctly represented in high-quality global climate models. This study aims to evaluate thermohaline properties both historically and under two simulations of the Brazilian Earth System Model BESM-OA2.5 in the South Atlantic Ocean (Representation Concentration Pathway (RCP) 4.5 and 8.5). Since error assessment in the global climate model (GCM) is fundamental to infer climate change projections, comparisons were made for thermohaline properties among four GCMs (HadGEM2-ES, MIROC-ESM-CHEM, MIROC5, and BESM-OA2.5) against data from ocean monitoring programs and from ORAS5-ECMWF. The results show common surface spatial pattern errors in all models, commonly related to mesoscale processes. Specific to BESM-OA2.5 over the Southern Ocean, we observed an increase in the temperature bias during autumn and summer, probably due to subsurface temperature overestimation linked to North Antarctic Deep Water (NADW) formation. With respect to salinity, the underestimations in the Subtropical/Subantarctic Zones and in the north of the South Atlantic subtropical gyre were linked to simulation errors in the Malvinas current. All models presented overestimated annual historical temperature rates, with BESM-OA2.5 being the closest to ORAS5. In the subsurface, the BESM-OA2.5 did not easily simulate the South Atlantic Central Water (SACW) formation, though in deep water, the model was able to better simulate the Antarctic Intermediate Water and NADW patterns. Statistically, the multi-model means performed better, while the BESM-OA2.5 performed worst among the models in both methodologies applied. In terms of projected scenarios, the models demonstrated sensitivity to variations in greenhouse gas emissions between the RCPs, with higher magnitude warming predicted in the equatorial zone, except for BESM-OA2.5.

Resumo em Inglês:

Abstract The richness and biomass distribution of mangrove macroalgae were evaluated along the main salinity gradient of the Paranaguá Bay subtropical estuarine complex in southern Brazil. We used a spatially hierarchical design to investigate the spatial scales that contributed most to the variation in richness and biomass within the association. A total of eighteen taxa of macroalgae and cyanobacteria were identified with nonlinear patterns of distribution. While richness correlated with the salinity gradient, algal biomass did not follow the predicted pattern. Conversely, most of the mangrove macroalgae distribution patterns were more related to small-scale processes than to salinity variation. These results indicated that even though coastal regions are exposed to large-scale environmental processes, the somewhat disregarded small-scale processes should be also considered to unravel patterns in biological distributions.

Resumo em Inglês:

Abstract Algal polysaccharides exhibit a wide range of biological activities and potential applications. Many of these bioactivities correlate positively with the presence of sulfate groups on the polysaccharides. The most common method used for sulfate quantification in algal samples is the turbidimetric method using the barium chloride-gelatin reagent. However, the original procedure is difficult to adapt for routine analysis since it is laborious and time-consuming. An optimized method was established using 96-well microplates, with the advantage of reducing waste and discrimination between organic and inorganic sulfates. This proposed method produced the same accuracy as the original.

Resumo em Inglês:

Abstract At age 101, Walter Munk passed away in 2019. His groundbreaking discoveries will still guide and amaze oceanography students for years to come. Here, we perceive patterns in rotating tank with Munk's circulation theory aided by a Lagrangian particles tracking algorithm and numerical modeling. From information captured by video, we track the trajectories of drifters, and then objectively mapped the streamfunction to obtain the mean circulation pattern. We were able to reproduce the wind-forced anticyclonic and asymmetric gyre, including the western boundary intensification and its retroflection. The latter phenomenon was predicted by the non-linear version of Munk's model and observed in real subtropical gyres as small recirculation regions. We have configured two numerical model simulations mimicking the physical experiment, with linear and non-linear terms. The comparison between the numerical and physical experiments confirmed the effect of non-linear distortion of the gyre. Geophysical fluid dynamics is often hard to visualize, and counter-intuitive in a rotating system. We present this set of experiments as a tool for oceanography teaching. Besides studying general ocean circulation theories and observations through practical examples, this experiment provides an opportunity to develop basic image processing and geophysical modelling skills.