Mainara Gouveia

@mg.phys.uni-sofia.bg

Meteorology and Geophysics Department
Faculty of Physics, Sofia University "St. Kliment Ohridski"

Mainara Gouveia


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https://researchid.co/mainarabg

RESEARCH, TEACHING, or OTHER INTERESTS

Geophysics, Oceanography, Environmental Science, Global and Planetary Change
7

Scopus Publications

Scopus Publications

  • Persistent Lagrangian transport patterns in the Black Sea identified from climatological Lagrangian Coherent Structures
    Mainara Biazati Gouveia, Elisaveta Peneva, Irina Gancheva, Emil V. Stanev
    Scientific Reports, 2025
    The quasi-steady Lagrangian transport patterns in the Black Sea are quantified and identified from climatological Lagrangian Coherent Structures. Wind velocity and Earth observation data have been incorporated to illustrate the potential applications of these results. The persistent squeezelines show that the high aggregation of passive tracers in the coastal region is a consequence of the complex coastal configuration of the Black Sea. The continental shelf is characterized by high stirring and mixing activities. The persistent and recurrent pathway patterns on the northwestern shelf are responsible for attracting nearby water parcels and passive tracers and conducting them towards the southern platform and offshore. Along the Rim Current, fifteen regions were identified as chevrons, indicating that they are jet-like structures. The jet-like structures and the northwestern shelf play an essential role in facilitating cross-shelf transport of material to neighboring coastal regions and offshore areas. Four transport barriers were identified by the climatological Lagrangian Coherent Structures as being both efficient and critical to the Lagrangian transport, and to the protection of coastal regions. One of these barriers is also identified as the Lagrangian Front. The Rim Current accounts for 44% of the Black Sea basin's climatological attraction strength. The Rim Current and the basin-wide climatological attraction strength show seasonal variations, with the highest values observed in winter. The distribution of persistent and recurrent mesoscale activity is also analyzed. The prevailing tendency among eddies identified is an anticyclonic orientation, typified by elevated levels of stirring and mixing. It is evident that an increase in wind speed over the basin results in a corresponding rise in the climatological attraction force exerted by anticyclonic eddies. This, in turn, leads to an enhancement in the process of stirring, mixing, and aggregation of nearby water parcels and passive tracers. However, it has been demonstrated that the presence of eddies is reduced in proportion to the velocity of the wind, particularly in the case of cyclonic eddies. The study offers valuable insights into the complex transport dynamics of the Black Sea ecosystem, with potential implications for environmental management and conservation efforts.
  • Western boundary currents drive sun-coral (Tubastraea spp.) coastal invasion from oil platforms
    Stella Correia Cesar Coelho, Douglas Francisco Marcolino Gherardi, Mainara Biazati Gouveia, Marcelo Visentini Kitahara
    Scientific Reports, 2022
    Most marine species have a planktonic larval phase that benefit from the surface oceanic flow to enhance their dispersion potential. For invasive species, the interaction of environmentally resistant larvae with different flow regimes and artificial substrates can lead to complex larval dispersion patterns and boost geographic expansion. In the Southwest Atlantic, the invasive corals Tubastraea spp. (sun-coral) have been recorded biofouling on oil platforms since the late 1980s. These platforms are considered important vectors for the established populations throughout the Brazilian coast. However, we still do not know how the position of these structures relative to regional flow contribute to the natural dispersion potential of these invaders on a regional scale. Herein, we used an eddy-resolving ocean model (ROMS) and an Individual Based Model (IBM-Ichthyop) to simulate the natural dispersion patterns of sun-coral larvae from all oil platforms on Brazilian oil-producing basins, for the austral summer and winter along 6 years (2010–2015) in 90-day simulations. We found that mortality rates by advection were significantly higher during the winter (p = 0.001) and when sources of larvae were compared throughout this season (p = 1.9 × 10–17). The influence of two western boundary currents and persistent eddy activity contribute to the dispersal of larvae to distances up to 7000 km. The effectiveness of each oil-producing basin as vectors for the entire Brazilian coastline, measured as the percentage of larval supply, highlights the importance of the northern Ceará (59.89%) and Potiguar (87.47%) basins and the more central Camamu (44.11%) and Sergipe-Alagoas (39.20%) basins. The poleward shift of the Southern branch of the South Equatorial Current during the winter causes larvae released from the Sergipe-Alagoas and Camamu basins to enter the North Brazil Current, expanding their dispersion towards the north. The Brazil Current disperses larvae southwards, but strong mesoscale activity prevents their dispersion to the coast, especially for those released from the oil platforms on Campos and Santos basins. Within this complex hydrodynamic setting, a few source areas, like those in the Sergipe-Alagoas and Camamu basins, can potentially contribute to the spread of larvae along nearly all the Brazilian coast. Therefore, oil platforms act as possible chronic sources of sun-coral propagules to the coast, emphasizing the urgency for a more detailed set of actions to control and monitor these invasive exotic species.
  • Oil spill detection based on texture analysis: how does feature importance matter in classification?
    Rodrigo N. Vasconcelos, Carlos A. D. Lentini, André T. Cunha Lima, Luís F. F. Mendonça, Garcia V. Miranda, Elaine C. B. Cambuí, Diego Pereira Costa, Soltan Galano Duverger, Mainara B. Gouveia, José M. Lopes, Milton J. Porsani
    International Journal of Remote Sensing, 2022
    Oil spill mapping and detection represent a relevant issue from an environmental point of view, given the effects on marine ecosystems. This study presents a new feature space assessment protocol for oil spill mapping using the Google Earth Engine (GEE). First, we selected five free Sentinel-1A sensor images from the GEE catalogue. Next, we processed the features evaluated from Gray Level Co-occurrence Matrix (GLCM) spectral and texture data. A recursive protocol that comprises a sequential classification of the evaluated image was also applied, wherein each iteration, the feature with less importance, was removed based on the Gini index. We used the Random Forest algorithm for image classification. Each image was trained on 10,000 points and evaluated for accuracy, with an equal number of points collected independently. Our results showed that the Sum Average (Savg), Convolution Smooth (Smooth), Cluster Shade Shade, and Gray level Correlation (Corr) features were essential to identify oil spills and increase the accuracy values. The best classification results based on the features removal experiment and global accuracy were Angola (0.9960), Trinidad and Tobago (0.9829), Italy (0.9506), Kuwait (0.9547), and Dubai (0.9344). Furthermore, it revealed that the protocol created was essential for better understanding the parameter space to detect oil spills with SAR images.
  • Persistent meanders and eddies lead to quasi-steady Lagrangian transport patterns in a weak western boundary current
    M. B. Gouveia, R. Duran, J. A. Lorenzzetti, A. T. Assireu, R. Toste, L. P. de F. Assad, D. F. M. Gherardi
    Scientific Reports, 2021
    The Brazil Current (BC) is a weak western boundary current flowing along the Southwestern Atlantic Ocean. It is frequently described as a flow with intense mesoscale activity and relatively low volume transport between 5.0 and 10.0 Sv. We use a 13-year eddy-resolving primitive-equation simulation to show that the presence of persistent meanders and eddies leads to characteristic quasi-steady Lagrangian transport patterns, aptly extracted through climatological Lagrangian Coherent Structures (cLCS). The cLCS position the surface expression of the BC core along the 2000-m isobath, in excellent visual agreement with high resolution satellite sea-surface temperature and the model Eulerian mean velocity. The cLCS deformation pattern also responds to zonally persistent cross-shelf SSH transition from positive (high) values near coastline to low (negative) values between 200- and 2000-m and back to positive (high) offshore from the 2000-m isobath. Zonally-paired cyclonic and anticyclonic structures are embedded in this transition, also causing the cLCS to deform into chevrons. An efficient transport barrier is identified close to the 200-m isobath confirmed by limited inshore movement of drogued drifters and accurately indicated by an along slope maxima of climatological strength of attraction. We also show that the persistent cyclonic and anticyclonic structures may induce localized cross-shelf transport. Regions of low climatological strength of attraction coincide with large shelves and with stagnant synthetic trajectories. We also show that cLCS accurately depict trajectories initiated at the location of Chevron’s spill (November 2011) as compared to synthetic and satellite-tracked trajectories, and the outline of the oil from that accident. There is also an agreement between the large-scale oil slicks reaching the Brazilian beaches (from August 2019 to February 2020) and the strength of climatological attraction at the coast. Our work also clarifies the influence of persistent mesoscale structures on the regional circulation. The identification and quantitative description of climatological Lagrangian coherent structures is expected to improve the effectiveness of future emergency response to oil spills, contingency planning, rescue operations, larval and fish connectivity assessment, drifter launch strategies, waste pollutant and marine debris dispersion and destination.
  • Publisher Correction: Persistent meanders and eddies lead to quasi‑steady Lagrangian transport patterns in a weak western boundary current (Scientific Reports, (2021), 11, 1, (497), 10.1038/s41598-020-79386-9)
    M. B. Gouveia, R. Duran, J. A. Lorenzzetti, A. T. Assireu, R. Toste, L. P. de F. Assad, D. F. M. Gherardi
    Scientific Reports, 2021
    An amendment to this paper has been published and can be accessed via a link at the top of the paper.
  • Sar oil spill detection system through random forest classifiers
    Marcos Reinan Assis Conceição, Luis Felipe Ferreira de Mendonça, Carlos Alessandre Domingos Lentini, André Telles da Cunha Lima, José Marques Lopes, Rodrigo Nogueira de Vasconcelos, Mainara Biazati Gouveia, Milton José Porsani
    Remote Sensing, 2021
    A set of open-source routines capable of identifying possible oil-like spills based on two random forest classifiers were developed and tested with a Sentinel-1 SAR image dataset. The first random forest model is an ocean SAR image classifier where the labeling inputs were oil spills, biological films, rain cells, low wind regions, clean sea surface, ships, and terrain. The second one was a SAR image oil detector named “Radar Image Oil Spill Seeker (RIOSS)”, which classified oil-like targets. An optimized feature space to serve as input to such classification models, both in terms of variance and computational efficiency, was developed. It involved an extensive search from 42 image attribute definitions based on their correlations and classifier-based importance estimative. This number included statistics, shape, fractal geometry, texture, and gradient-based attributes. Mixed adaptive thresholding was performed to calculate some of the features studied, returning consistent dark spot segmentation results. The selected attributes were also related to the imaged phenomena’s physical aspects. This process helped us apply the attributes to a random forest, increasing our algorithm’s accuracy up to 90% and its ability to generate even more reliable results.
  • Do the Brazilian sardine commercial landings respond to local ocean circulation?
    Mainara B. Gouveia, Douglas F. M. Gherardi, Carlos A. D. Lentini, Daniela F. Dias, Paula C. Campos
    Plos One, 2017
    It has been reported that sea surface temperature (SST) anomalies, flow intensity and mesoscale ocean processes, all affect sardine production, both in eastern and western boundary current systems. Here we tested the hypothesis whether extreme high and low commercial landings of the Brazilian sardine fisheries in the South Brazil Bight (SBB) are sensitive to different oceanic conditions. An ocean model (ROMS) and an individual based model (Ichthyop) were used to assess the relationship between oceanic conditions during the spawning season and commercial landings of the Brazilian sardine one year later. Model output was compared with remote sensing and analysis data showing good consistency. Simulations indicate that mortality of eggs and larvae by low temperature prior to maximum and minimum landings are significantly higher than mortality caused by offshore advection. However, when periods of maximum and minimum sardine landings are compared with respect to these causes of mortality no significant differences were detected. Results indicate that mortality caused by prevailing oceanic conditions at early life stages alone can not be invoked to explain the observed extreme commercial landings of the Brazilian sardine. Likely influencing factors include starvation and predation interacting with the strategy of spawning "at the right place and at the right time".