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Adriana Gonzalez-Silvera   Dr.  University Educator/Researcher 
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Adriana Gonzalez-Silvera published an article in September 2018.
Top co-authors
Robert Frouin

128 shared publications

Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, CA 92093, USA

Eduardo Santamaría-Del-Ángel

17 shared publications

Facultad de Ciencias Marinas, Universidad Autónoma de Baja California, Carretera Tijuana-Ensenada Km 103, 22800 Ensenada, BC, México

Charles C. Trees

1 shared publications

Jing Tan

1 shared publications

Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, CA 92093, USA

Stella Patricia Betancur-Turizo

1 shared publications

Facultad de Ciencias Marinas, Universidad Autónoma de Baja California, Carretera Tijuana-Ensenada Km 103, 22800 Ensenada, BC, México

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(2004 - 2018)
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Article 0 Reads 0 Citations Evaluation of Semi-Analytical Algorithms to Retrieve Particulate and Dissolved Absorption Coefficients in Gulf of Califo... Stella Patricia Betancur-Turizo, Adriana González-Silvera, E... Published: 10 September 2018
Remote Sensing, doi: 10.3390/rs10091443
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Two semi-analytical algorithms, Generalized Inherent Optical Property (GIOP) and Garver-Siegel-Maritorena (GSM), were evaluated in terms of how well they reproduced the absorption coefficient of phytoplankton (aph(λ)) and dissolved and detrital organic matter (adg(λ)) at three wavelengths (λ of 412, 443, and 488 nm) in a zone with optically complex waters, the Upper Gulf of California (UGC) and the Northern Gulf of California (NGC). In the UGC, detritus determines most of the total light absorption, whereas, in the NGC, chromophoric dissolved organic material (CDOM) and phytoplankton dominate. Upon comparing the results of each model with a database assembled from four cruises done from spring to summer (March through September) between 2011 and 2013, it was found that GIOP is a better estimator for aph(λ) than GSM, independently of the region. However, both algorithms underestimate in situ values in the NGC, whereas they overestimate them in the UGC. Errors are associated with the following: (a) the constant a*ph(λ) value used by GSM and GIOP (0.055 m2 mgChla−1) is higher than the most frequent value observed in this study’s data (0.03 m2 mgChla−1), and (b) satellite-derived chlorophyll a concentration (Chla) is biased high compared with in situ Chla. GIOP gave also better results for the adg(λ) estimation than GSM, especially in the NGC. The spectral slope Sdg was identified as an important parameter for estimating adg(λ), and this study’s results indicated that the use of a fixed input value in models was not adequate. The evaluation confirms the lack of generality of algorithms like GIOP and GSM, whose reflectance model is too simplified to capture expected variability. Finally, a greater monitoring effort is suggested in the study area regarding the collection of in situ reflectance data, which would allow explaining the effects that detritus and CDOM may have on the semi-analytical reflectance inversions, as well as isolating the possible influence of the atmosphere on the satellite-derived water reflectance and Chla.
Article 3 Reads 1 Citation Identification of Phytoplankton Blooms under the Index of Inherent Optical Properties (IOP Index) in Optically Complex W... Jesús Aguilar-Maldonado, Eduardo Santamaria-Del-Angel, Adria... Published: 30 January 2018
Water, doi: 10.3390/w10020129
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Phytoplankton blooms are sporadic events in time and are isolated in space. This complex phenomenon is produced by a variety of both natural and anthropogenic causes. Early detection of this phenomenon, as well as the classification of a water body under conditions of bloom or non-bloom, remains an unresolved problem. This research proposes the use of Inherent Optical Properties (IOPs) in optically complex waters to detect the bloom or non-bloom state of the phytoplankton community. An IOP index is calculated from the absorption coefficients of the colored dissolved organic matter (CDOM), the phytoplankton (phy) and the detritus (d), using the wavelength (λ) 443 nm. The effectiveness of this index is tested in five bloom events in different places and with different characteristics from Mexican seas: 1. Dzilam (Caribbean Sea, Atlantic Ocean), a diatom bloom (Rhizosolenia hebetata); 2. Holbox (Caribbean Sea, Atlantic Ocean), a mixed bloom of dinoflagellates (Scrippsiella sp.) and diatoms (Chaetoceros sp.); 3. Campeche Bay in the Gulf of Mexico (Atlantic Ocean), a bloom of dinoflagellates (Karenia brevis); 4. Upper Gulf of California (UGC) (Pacific Ocean), a diatom bloom (Coscinodiscus and Pseudo-nitzschia) and 5. Todos Santos Bay, Ensenada (Pacific Ocean), a dinoflagellate bloom (Lingulodinium polyedrum). The diversity of sites show that the IOP index is a suitable method to determine the phytoplankton bloom conditions.
Article 0 Reads 2 Citations Fitting vertical chlorophyll profiles in the California Current using two Gaussian curves Mauricio Muñoz-Anderson, Roberto Millán-Núñez, Rafael Hernán... Published: 25 May 2015
Limnology and Oceanography: Methods, doi: 10.1002/lom3.10034
DOI See at publisher website
Article 2 Reads 1 Citation Bio-Optical Characteristics of the Northern Gulf of California during June 2008 Martha Bastidas-Salamanca, Adriana Gonzalez-Silvera, Roberto... Published: 01 January 2014
International Journal of Oceanography, doi: 10.1155/2014/384618
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Bio-optical variables in the Northern Gulf of California were analyzed using in situ and satellite data obtained during a cruise in June 2008. The study area was divided into three bio-optical regions: Upper Gulf (UG), Northern Gulf (NG), and Great Isles (GI). Each region was characterized according to phytoplankton pigment concentration, phytoplankton and nonpigmented material spectral absorption coefficients, and spectral reflectance. Observed patterns were an indication of the shift in bio-optical conditions from north to south going from turbid and eutrophic waters to mesotrophic ones. Although there was a good agreement between satellite and in situ Chla (RMSE ±33%), an overestimation of in situ Chla was observed. This was partly explained by the presence of nonalgal particles, as well as the influence of desert and continental aerosols, which is generally overcorrected in the standard processing. The UG and NG could be considered as Case 2 waters, but they did exhibit different bio-optical characteristics. This implies that both biological and optical properties should be invoked to better understand water reflectance variability in the study region and its implications for the remote sensing of Chla and biogeochemical processes.1. IntroductionObserving the optical properties of the marine environment is crucial for the evaluation of satellite ocean color products and the development of spectral deconvolution techniques. Coastal zones are of particular interest, since they are influenced by mineral sediments, brought by rivers or stirred up from the bottom, as well as by colored dissolved organic matter of terrestrial origin (CDOM). In these zones, however, the algorithms (of the blue-to-green ratio type), developed for open ocean waters, generally fail, with the result of strongly overestimated chlorophyll-a concentration (Chla) [1].The Gulf of California is a subtropical semienclosed sea characterized by a cyclonic circulation in summer and an anticyclonic circulation in winter and by a seasonally reversible upwelling system with moderate upwelling along the west coast during summer and intense upwelling along the east coast during winter [2, 3]. In the northern part of the Gulf, that is, from the Colorado River Delta to 28°N (Figure 1(a)), these characteristics and also the bathymetry result in an eddy in the center of the basin and a coastal current on the mainland shelf. Direct observations show that the central eddy is ~150 m deep, cyclonic from June to September, and anticyclonic from November to April [4, 5]. Satellite observations have confirmed the cyclonic pattern during summer, but at the same time they have revealed a more complex circulation pattern with numerous plumes and eddies (some anticyclonic), traveling from coast to coast, enhancing the exchange of suspended material [6].Figure 1: (a) Location of the oceanographic stations where measurements and sample collection were taken during cruise. Symbols marked with a red circle are stations where radiometric (SIMBADA) measurements were taken. (b) Bio-optical regions defined according to the first optical depth. The area colored with light gray is the Upper Gulf region (UG), medium gray background is the Great Island region (GI), and the dark gray background indicates the Northern Gulf region (NG).The Northern Gulf is mostly less than 200 m deep and tidal mixing is very important [7], especially around the sills of the midriff archipelago region (Great Isles, GI) and in the shallow Upper Gulf (UG, north of 34°). The GI region and the sills are an area of continuous upward pumping of nutrients by tidal mixing [8, 9], while in the UG region tidal mixing has the same effect. These complex circulation patterns support very high primary production rates [8] and a high-diversity, high abundance fish fauna of commercial and ecological importance [10–12].In the UG region tidal mixing is also responsible for the resuspension of inorganic material generating a zone of high turbidity [11], which can eventually be observed in true-color imagery of the area. For this reason these waters were classified as Case 2 while those to the south were classified as Case 1 waters [13]. However, the complex circulation patterns mentioned above may lead to a high spatial variability of such properties. In addition, the area studied by Pegau et al. [13] was located mostly to the south of the GI region and few stations covered the northern area.In this context, the hypothesis is that there should be at least two distinct bio-optical regimes in the Northern Gulf of California that respond to the strong oceanographic heterogeneity of this zone. Based on the measurement of some surface bio-optical variables carried out in June 2008, the present study aims to (i) identify different bio-optical regions; (ii) evaluate the differences in spectral reflectance and spectral particulate absorption among identified bio-optical regions; (iii) evaluate the role of different phytoplankton communities among regions; and (iv) quantify the influence of these differences on the remote sensing of Chla.2. Methodology2.1. Sampling ProcedureDuring June 2 to 17, 2008, 48 stations were made in the Northern Gulf of California, from 28° to 32°N and 112 to 115°W (Figure 1(a)). Water transparency was measured using Secchi disk from which we calculated the attenuation coefficient (Kd) and the first optical depth (1OD) [14]. Surface water samples (~0.40 m depth) were taken using Niskin bottles to measure phytoplankton pigments concentration and light absorption coefficient by particulate material.In some stations, sampled between 10 a.m. and 3 p.m. and with clear sky conditions, marine reflectance () was measured using a SIMBADA radiometer, an improved version of the SIMBAD radiometer [15] that measures in spectral bands centered at wavelengths of 350, 380, 412, 443, 490, 510, 560, 620, 670, 750, and 870 nm [16]. The instrument was calibrated in the laboratory using an integrating sphere and in the field using a Spectralon plaque. Procedures described in Bécu [16] were applied to process the data into marine reflectance.For pigment analysis, one to two liters (depending on station location) of seawater was filtered through 25 mm diameter Whatman GF/F filters with positive pressure. Filters were wrapped in aluminum foil and stored in liquid nitrogen until laboratory analysis. One or two liters of seawater was also filtered through Whatman GF/F filters for measurement of particulate light absorption. Filters were placed in Histoprep tissue caps and stored in liquid nitrogen until laboratory analysis.2.2. Pigment ConcentrationPigments were extracted in 100% acetone for 24 h with trans-beta-apo-carotene as internal standard in a freezer at −20°C, with a previous three-minute sonication. Pigment extract was filtered with 0.2 μm acrodisc filters and injected into a Varian HPLC system with a degasser and Adsorbosphere C8 column ( mm, 3.5 μm particle size). A two-solvent gradient, methanol and ammonium acetate (70 : 30 v : v), was used following the methodology described by Barlow et al. [17]. The HPLC pigment standards were purchased from Sigma-Aldrich and DHI. They were quantified with a spectrophotometer using published extinction coefficients [18] and used to identify pigment peaks and calibrate pigment concentrations based on the peak areas.Pigment information was used to calculate phytoplankton size fractions (micro, nano, and picoplankton) according to Uitz et al. [19].2.3. Particulate Absorption CoefficientIn the laboratory, filters were saturated with filtered seawater, which had been irradiated with UV lamps (25 W) and the optical density (OD) was measured on a Perkin-Elmer Lambda 10 spectrophotometer with integrating sphere, following the procedure in Mitchell et al. [20]. OD was measured from 400 to 750 nm with a resolution of 1 nm before and after rinsing the filters with hot methanol [20] for 15 min twice. Absorption coefficients for a particles and not pigmented particles, that is, and , were determined using the equation: where is the filter clearance area, is the filtered volume, and 0.4068 and 0.368 are the coefficients to correct the increase in path length caused by multiple scattering in the glass-fiber filter, which were previously determined for this spectrophotometer.Phytoplankton absorption was determined by the difference between absorption by total particulate matter, , and absorption by nonpigmented material, . The specific absorption coefficient by phytoplankton , with units m2 (mg Chla)−1, was obtained by dividing (m−1) by Chla (mg m−3) measured by HPLC. To compare curve shapes, normalized absorption (A, dimensionless) was plotted, which was calculated by normalizing the spectrum to the absorption maxima in the blue (around 440 nm).2.4. Satellite ImagesSea-viewing Wide Field-of-View Sensor (SeaWiFS) and Moderate resolution Imaging Spectroradiometer (MODIS/Aqua) images were processed at 1 km spatial resolution for the entire study period using SeaDAS V5.5 to obtain Chl. For comparison between the in situ data and satellite products and to minimize georeference errors, median values were computed for all products in a 3-by-3 pixel window centered on the locations of the oceanographic stations. Furthermore, the coefficient of variation (CV) was computed for the Chla within each 3-by-3 window, and the retrieved value was excluded if CV > 0.2. This process was carried out to avoid strong variation from nonhomogeneous regions within each window. For the temporal threshold coincidence between the satellite and in situ measurements, a ±3 hour window around the satellite overpass was considered, which follows the NASA criterion [21].The calculation of Chl from SeaWiFS data is based on OC4V4 algorithm while from MODIS data it is based on OC3 algorithm [22], and Chl was evaluated against in situ Chla. In the comparisons, SeaWiFS and in situ Chla (), MODIS and in situ Chla (), and the a
Article 0 Reads 3 Citations Dynamic Regionalization of the Gulf of Mexico based on normalized radiances (nLw) derived from MODIS-Aqua Mariana Callejas-Jiménez, Eduardo Santamaria-Del-Angel, Adri... Published: 01 April 2012
Continental Shelf Research, doi: 10.1016/j.csr.2012.01.014
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Article 0 Reads 3 Citations The response of shrimp fisheries to climate variability off Baja California, Mexico Adriana Gonzalez-Silvera, R. Cajal-Medrano, M. S. Galindo-Be... Published: 22 December 2010
ICES Journal of Marine Science, doi: 10.1093/icesjms/fsq186
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