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Satellite radar data has proven very useful in large−scale oil spill detection due to its large coverage or its ability to image the sea surface independently of light and cloud conditions. However, detection of oil slicks is a... more
Satellite radar data has proven very useful in large−scale oil spill detection due to its large coverage or its ability to image the sea surface independently of light and cloud conditions. However, detection of oil slicks is a complicated operation with some limitations, since several other phenomena also give rise to similar signatures, including low wind areas, current shear zones, internal waves or man−made structures over the sea surface. With the aim of improving the discrimination between real oil slicks and similar radar signatures, it has been developed a system for automatic oil spill detection from ENVISAR ASAR images that considers the possible presence of look−alikes. In a first step, signatures suspicious of being oil spills are automatically identified by applying a fast algorithm based on adaptive threshold. Then, the previous slicks are filtered by using masks arisen from additional data, such us wind or visual observations, for the purpose of removing those signatu...
The Prestige tanker caused an extensive oil spill off the north−west coast of Spain on November 2002, occasioning a big environmental and economic catastrophe in the Galician region. The Spanish project CONTINMAR is aimed to the design of... more
The Prestige tanker caused an extensive oil spill off the north−west coast of Spain on November 2002, occasioning a big environmental and economic catastrophe in the Galician region. The Spanish project CONTINMAR is aimed to the design of a contingency plan in the event of accidental marine pollution on the area, including the development of an oil spill detection, monitoring and forecasting system using remote sensing and artificial intelligence techniques. Radar imagery have proven a very useful tool in order to detect oil spills due to the dampening effect of oil on water, and different classification algorithms have been proposed. A hybrid artificial intelligence approach to the problem of classification of oil spills in marine environments offers potential advantages over alternative systems, because it is able to deal with uncertain, incomplete and even inconsistent data. The final classification system that is proposed in this paper will be a CBR−based neuro−symbolic framewor...
Blue whales are sighted every year around the Azores islands, which apparently provide an important seasonal foraging area. In this paper we aim to characterize habitat preferences and analyze the temporal distribution of blue whales... more
Blue whales are sighted every year around the Azores islands, which apparently provide an important seasonal foraging area. In this paper we aim to characterize habitat preferences and analyze the temporal distribution of blue whales around São Miguel Island. To do so, we applied Generalized Additive Models to an opportunistic cetacean occurrence dataset and remotely sensed environmental data on bathymetry, sea surface temperature, chlorophyll concentration and altimetry. We provide a brief description of the oceanography of the area, emphasizing its high spatio-temporal variability. In order to capture this dynamism, we used environmental data with two different spatial resolutions (low and high) and three different temporal resolutions (daily, weekly and monthly), thus accounting for both long-term oceanographic events such as the spring bloom, and shorter-term features such as eddies or fronts. Our results show that blue whales have a well-defined ecological niche around the Azor...
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The development and validation of remote sensing-based approaches for the retrieval of CDOM concentrations requires a comprehensive understanding of the sources and magnitude of variability in the optical properties of dissolved material... more
The development and validation of remote sensing-based approaches for the retrieval of CDOM concentrations requires a comprehensive understanding of the sources and magnitude of variability in the optical properties of dissolved material within lakes. In this study, spatial and seasonal variability in concentration and composition of CDOM and the origin of its variation was studied in Lake Balaton (Hungary), a large temperate shallow lake in central Europe. In addition, we investigated the effect of photobleaching on the optical properties of CDOM through in-lake incubation experiments. There was marked variability throughout the year in CDOM absorption in Lake Balaton (aCDOM (440) = 0.06–9.01 m−1). The highest values were consistently observed at the mouth of the main inflow (River Zala), which drains humic-rich material from the adjoining Kis-Balaton wetland, but CDOM absorption decreased rapidly towards the east where it was consistently lower and...
Research Interests: Earth Sciences, Environmental Science, Chemistry, Biological Sciences, Environmental Sciences, and 9 moreAtmospheric sciences, Biogeosciences, Photobleaching, Spatial Variability, Lake Balaton, Dissolved Organic Carbon, Colored Dissolved Organic Matter, Chromophoric Dissolved Organic Matter (CDOM), and Temperate Climate
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Research Interests: Geography, Earth Sciences, Hydrobiology, Biological Sciences, Seasonality, and 15 moreEnvironmental Sciences, Environmental Variables, Group Size, Continental shelf, Environmental Conditions, Coastal Zone, Coastal waters, Marine Mammal, Geographic Information System, Common Dolphin, GIS, Environmental Parameter, Shallow Water, Chlorophyll a, and generalised additive model
An innovative optical method for remote monitoring of water pollution was developed and tested in AMPERA ERA-NET Programme, project DEOSOM. The method is based on remote detection of laser-induced fluorescent radiation (LIF LIDAR). In the... more
An innovative optical method for remote monitoring of water pollution was developed and tested in AMPERA ERA-NET Programme, project DEOSOM. The method is based on remote detection of laser-induced fluorescent radiation (LIF LIDAR). In the project, compact and ...
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Evangelos Spyrakos 1 , Luis Gonzalez Vilas 1 , Jesus Torres Palenzuela 1 and Nina Yarovenko 1. University of Vigo, Department of Applied Physics, Vigo, Spain; jesu@uvigo.es. ABSTRACT. ... Journal of Marine Systems, 54: 261276. 18 Morel A... more
Evangelos Spyrakos 1 , Luis Gonzalez Vilas 1 , Jesus Torres Palenzuela 1 and Nina Yarovenko 1. University of Vigo, Department of Applied Physics, Vigo, Spain; jesu@uvigo.es. ABSTRACT. ... Journal of Marine Systems, 54: 261276. 18 Morel A & L Prieur, 1977. ...
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This work presents new prediction models based on recent developments in machine learning methods, such as Random Forest (RF) and AdaBoost, and compares them with more classical approaches, i.e., support vector machines (SVMs) and neural... more
This work presents new prediction models based on recent developments in machine learning methods, such as Random Forest (RF) and AdaBoost, and compares them with more classical approaches, i.e., support vector machines (SVMs) and neural networks (NNs). The models predict Pseudo-nitzschia spp. blooms in the Galician Rias Baixas. This work builds on a previous study by the authors (doi.org/10.1016/j.pocean.2014.03.003) but uses an extended database (from 2002 to 2012) and new algorithms. Our results show that RF and AdaBoost provide better prediction results compared to SVMs and NNs, as they show improved performance metrics and a better balance between sensitivity and specificity. Classical machine learning approaches show higher sensitivities, but at a cost of lower specificity and higher percentages of false alarms (lower precision). These results seem to indicate a greater adaptation of new algorithms (RF and AdaBoost) to unbalanced datasets. Our models could be operationally imp...
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The NW coast of the Iberian Peninsula is dominated by extensive shellfish farming, which places this region as a world leader in mussel production. Harmful algal blooms in the area frequent lead to lengthy harvesting closures threatening... more
The NW coast of the Iberian Peninsula is dominated by extensive shellfish farming, which places this region as a world leader in mussel production. Harmful algal blooms in the area frequent lead to lengthy harvesting closures threatening food security. This study developed a framework for the detection of Pseudo-nitzschia blooms in the Galician rias from satellite data (MERIS full-resolution images) and identified key variables that affect their abundance and toxicity. Two events of toxin-containing Pseudo-nitzschia were detected (up to 2.5 μg L−1 pDA) in the area. This study suggests that even moderate densities of Pseudo-nitzschia in this area might indicate high toxin content. Empirical models for particulate domoic acid (pDA) were developed based on MERIS FR data. The resulting remote-sensing model, including MERIS bands centered around 510, 560, and 620 nm explain 73% of the pDA variance (R2 = 0.73, p < 0.001). The results show that higher salinity values and lower Si(OH)4/N...
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Research Interests:
There is a significant interest in alternative renewable energy sources due to the global increase of energy demands and the daily decrease of fossil fuel resources. Biofuel production from microalgae can be both sustainable and... more
There is a significant interest in alternative renewable energy sources due to the global increase of energy demands and the daily decrease of fossil fuel resources. Biofuel production from microalgae can be both sustainable and economically viable. Particularly in the case of algal growth in wastewater it is considered as possible to achieve the removal or biotranformation of pollutants from these types of waters and algal biomass production. EnerBioAlgae is project funded by the Interreg SUDOE (“Espacio Sudoeste Europeo”) program and led by the University of Vigo, Spain which aims to investigate the biofuel production by microalgae grown in several types of wastewater. Among the objectives of this project is the development of a system based on spectral fluorescence analysis techniques and neural network methods for the continuous monitoring of microalgae status and the different contaminants in the wastewater. In the first place this monitoring system is going to be developed and...
ABSTRACT In typical case 2 waters an accurate remote sensing retrieval of chlorophyll a (chla) is still challenging. There is a widespread understanding that universally applicable water constituent retrieval algorithms are currently not... more
ABSTRACT In typical case 2 waters an accurate remote sensing retrieval of chlorophyll a (chla) is still challenging. There is a widespread understanding that universally applicable water constituent retrieval algorithms are currently not feasible, shifting the research focus to regionally specific implementations of powerful inversion methods. This study takes advantage of regionally specific chlorophyll a (chla) algorithms, which were developed by the authors of this abstract in previous works, and the characteristics of Medium Resolution Imaging Spectrometer (MERIS) in order to study harmful algal events in the optically complex waters of the Galician Rias (NW). Harmful algal events are a frequent phenomenon in this area with direct and indirect impacts to the mussel production that constitute a very important economic activity for the local community. More than 240 106 kg of mussel per year are produced in these highly primary productive upwelling systems. A MERIS archive from nine years (2003-2012) was analysed using regionally specific chla algorithms. The latter were developed based on Multilayer perceptron (MLP) artificial neural networks and fuzzy c-mean clustering techniques (FCM). FCM specifies zones (based on water leaving reflectances) where the retrieval algorithms normally provide more reliable results. Monthly chla anomalies and other statistics were calculated for the nine years MERIS archive. These results were then related to upwelling indices and other associated measurements to determine the driver forces for specific phytoplankton blooms. The distribution and changes of chla are also discussed.
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ABSTRACT The shelf of Galicia, holds one of the most important communities of cetaceans of the whole Spanish coast. Although in the last years have been developed important studies related with diverse aspects of the biology of the... more
ABSTRACT The shelf of Galicia, holds one of the most important communities of cetaceans of the whole Spanish coast. Although in the last years have been developed important studies related with diverse aspects of the biology of the cetaceans of these waters, most of them were based exclusively on information related to strandings, and the studies of populations’ structure, based on sightings, were very scarce. In this work are presented the results of the sightings registered during the realization of the investigation project (CE00/027) «Pelagic fisheries in Scotland (UK) and Galicia (Spain): observer studies to collect fishery data and monitor by-catches of small cetaceans». Between the months of February and August of 2001, three observers carried out a total of 134 days of shipment along the whole coast of Galicia, on board 11 fishing ships, collecting information about sightings of cetaceans, and additionally, oceanographic and fishing activity data. During a total of 903 hours of observation, they registered 182 sightings, of these, 80,5% belongs to the common dolphin, who is the species that presents a bigger distribution area. The other observed species and their sightings´s percentages are the following ones: long finned pilot whale 4,9%, bottlenose dolphin 2,7%, harbour porpoise 2,7%, Risso´s dolphin 2,7%, non identified misticetes 2,7%, striped dolphin 2,2%, non identified odontocetes 1,1% and fin whale 0,5%.
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Since mid-2003, systematic monthly sightings surveys for cetaceans have been carried out in Galicia (north-west Spain) from observation points around the coastline, with the aim of providing baseline data on cetacean distribution and... more
Since mid-2003, systematic monthly sightings surveys for cetaceans have been carried out in Galicia (north-west Spain) from observation points around the coastline, with the aim of providing baseline data on cetacean distribution and habitat use to underpin future conservation measures. Here we summarize results for September 2003 to October 2007. The most frequently recorded species were the bottlenose dolphin (Tursiops truncatus, seen during 10.7% of observation periods), common dolphin (Delphinus delphis, 3.7%), harbour porpoise (Phocoena phocoena, 1.6%), Risso's dolphin (Grampus griseus, 0.4%) and short-finned pilot whale (Globicephala melas, 0.2%). The three most common species showed different distribution patterns along the coast. In terms of habitat preferences, bottlenose dolphins were seen to be associated with more productive areas (areas with higher chlorophyll-a concentrations) where the continental shelf was wider while both common dolphins and harbour porpoises we...
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Resumen Este trabajo muestra resultados de un proyecto de estudio local para la zona de Galicia que comenzó en 2001 y que tiene por título Sistema predictivo de esfuerzo pesquero para la flota artesanal Gallega. Este proyecto ha... more
Resumen Este trabajo muestra resultados de un proyecto de estudio local para la zona de Galicia que comenzó en 2001 y que tiene por título Sistema predictivo de esfuerzo pesquero para la flota artesanal Gallega. Este proyecto ha requerido la colaboración de un total de 17 ...
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Research Interests:
The surface circulation off the western coast of the Iberian Peninsula is strongly influenced by the atmospheric pressure distribution in the North Atlantic. During the winter season, the combination of the onshore Ekman transport and the... more
The surface circulation off the western coast of the Iberian Peninsula is strongly influenced by the atmospheric pressure distribution in the North Atlantic. During the winter season, the combination of the onshore Ekman transport and the geostrophic adjustment of the large-scale oceanic zonal flow causes the appearance of a seasonal poleward along-shore flow named Navidad current. This surface flow was investigated using hydrographic data together with satellite infrared imagery. ERS Synthetic Aperture Radar (SAR) data responds to the roughness of the sea surface, and the radar backscattering strength is dominated by the Bragg backscattering mechanism. In this paper a strip of four ERS-2 SAR frames acquired over the North Atlantic ocean off the Iberian Peninsula coast on 26 November 2002 were used to t ry to demonstrate the capability of radar data to identify the presence of this surface current under certain hydrodynamic conditions.
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Space‐borne synthetic aperture radar has been proven to be a useful tool for ocean oil spill monitoring due to its large coverage, independence of the day–night cycle and all‐weather capability. In this paper, a method for oil spill... more
Space‐borne synthetic aperture radar has been proven to be a useful tool for ocean oil spill monitoring due to its large coverage, independence of the day–night cycle and all‐weather capability. In this paper, a method for oil spill detection based on a visual interpretation was applied to two consecutive Advanced Synthetic Aperture Radar (ASAR) images acquired during the Prestige oil
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The Atlantic coast of Iberian Peninsula offers an excellent opportunity for a study of upwelling filaments and their importance in lateral exchanges of nutrient and biota. Simultaneous acquisition SeaWIFS (Sea Viewing Wide Field Sensor)... more
The Atlantic coast of Iberian Peninsula offers an excellent opportunity for a study of upwelling filaments and their importance in lateral exchanges of nutrient and biota. Simultaneous acquisition SeaWIFS (Sea Viewing Wide Field Sensor) and AVHRR (Advanced Very High Resolution Radiometer) NOAA imagery of the north-west of the Iberian Margin were obtained on August 1998. Satellite-derived chlorophyll-a from SeaWiFS data, which have been provided by the Remote Sensing Group at Plymouth Marine Laboratory and sea surface temperature (SST) from AVHRR data were compared in function to find a correlation between sea surface temperature and chlorophyll-a.
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Title: Detection of Pseudo-Nitzchia SPP Toxic Blooms Using MERIS Images on the Galician Coast. Authors: Torres Palenzuela, JM; Gonzalez Vilas, L.; Mosquera Giménez, A. Publication: Proceedings of the 2004 Envisat & ERS Symposium (ESA... more
Title: Detection of Pseudo-Nitzchia SPP Toxic Blooms Using MERIS Images on the Galician Coast. Authors: Torres Palenzuela, JM; Gonzalez Vilas, L.; Mosquera Giménez, A. Publication: Proceedings of the 2004 Envisat & ERS Symposium (ESA SP-572). ...
Space‐borne synthetic aperture radar has been proven to be a useful tool for ocean oil spill monitoring due to its large coverage, independence of the day–night cycle and all‐weather capability. In this paper, a method for oil spill... more
Space‐borne synthetic aperture radar has been proven to be a useful tool for ocean oil spill monitoring due to its large coverage, independence of the day–night cycle and all‐weather capability. In this paper, a method for oil spill detection based on a visual interpretation was applied to two consecutive Advanced Synthetic Aperture Radar (ASAR) images acquired during the Prestige oil spill off the Spanish coast. The obtained oil spill information was integrated into a Geographical Information System (GIS) database in order to study the spatial distribution and the evolution of the slicks between both days, in addition to carrying out a comparison with field observations. The results show the great capability of monitoring and forecasting marine oil spills caused by large oil tanker accidents by means of the use of radar imagery jointly with other information, such as wind data or in situ observations.
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Research Interests: Algorithms, Remote Sensing, Neural Networks, Neural Network, Image, and 16 moreConcentration, High Frequency, Data, Technique, Estimation, Geomatic Engineering, Clustered Data, Root-Mean Square Error, Water Use, Utilization, Ocean Colour, Coastal Zone, Coastal waters, Northwest, Chlorophyll a, and Fuzzy C-mean
The spatial and seasonal distribution of cetaceans and possible links with environmental conditions were studied at the Galician continental shelf. Data were collected between February–August 2001 and June–September 2003 during... more
The spatial and seasonal distribution of cetaceans and possible links with environmental conditions were studied at the Galician continental shelf. Data were collected between February–August 2001 and June–September 2003 during opportunistic surveys onboard fishing boats. Seven species of cetaceans were identified from 250 sightings of 6,846 individuals. The common dolphin (Delphinus delphis) was by far the most frequently sighted and the most widely distributed species. Spatiotemporal trends in cetacean distribution and abundance, and their relationships with environmental parameters (sea depth, SST and chlorophyll-a) were quantified using generalised additive models (GAMs). Results for all cetaceans were essentially the same as for common dolphins alone. Modelling results indicated that the number of common dolphin sightings per unit effort was higher further south. The number of individual common dolphins seen per sighting of this species (i.e. group size) was however higher in the north and west of the study area, higher later in the year and higher in 2001 than in 2003. In contrast, the number of common dolphin calves seen (per sighting of this species) was higher in the south. Models including environmental variables indicated larger common dolphin group sizes in deeper waters and at higher chlorophyll concentrations (i.e. in more productive areas). There was also a positive relationship between survey effort and group size, which is probably an artefact of the tendency of the survey platforms (fishing boats) to spend most time in areas of high fish abundance. Numbers of common dolphin calves per sighting were found to be higher in shallower waters. The results are consistent with common dolphins foraging mainly in deeper waters of the Galician continental shelf, while more southern inshore waters may represent a nursery area.
Research Interests: Earth Sciences, Hydrobiology, Biological Sciences, Seasonality, Environmental Sciences, and 13 moreEnvironmental Variables, Group Size, Continental shelf, Environmental Conditions, Coastal Zone, Coastal waters, Marine Mammal, Geographic Information System, Common Dolphin, GIS, Environmental Parameter, Shallow Water, and Chlorophyll a
This study takes advantage of a regionally specific algorithm and the characteristics of Medium Resolution Imaging Spectrometer (MERIS) in order to deliver more accurate, detailed chlorophyll a (chla) maps of optically complex coastal... more
This study takes advantage of a regionally specific algorithm and the characteristics of Medium Resolution Imaging Spectrometer (MERIS) in order to deliver more accurate, detailed chlorophyll a (chla) maps of optically complex coastal waters during an upwelling cycle. MERIS full resolution chla concentrations and in situ data were obtained on the Galician (NW Spain) shelf and in three adjacent rias
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Space‐borne synthetic aperture radar has been proven to be a useful tool for ocean oil spill monitoring due to its large coverage, independence of the day–night cycle and all‐weather capability. In this paper, a method for oil spill... more
Space‐borne synthetic aperture radar has been proven to be a useful tool for ocean oil spill monitoring due to its large coverage, independence of the day–night cycle and all‐weather capability. In this paper, a method for oil spill detection based on a visual interpretation was applied to two consecutive Advanced Synthetic Aperture Radar (ASAR) images acquired during the Prestige oil