Papers by adan mejia-trejo
Brazilian Journal of Animal and Environmental Research, 2022
Atualmente não existe um projeto de música que pode ser implementado de maneira geral no ambiente... more Atualmente não existe um projeto de música que pode ser implementado de maneira geral no ambiente intermareal. No presente estudio se propõem modificações a um método tradicional e se desmistificam as diferenças em suas estimativas. A través de um registro fotográfico, o método permite censor com rapidez e mais detalhes da composição da comunidade macrobentónica considerando a heterogeneidade do sustrato. Esto es relevante, principalmente porque se trabaja na franja inferior e se dispone de poco tiempo. A comparação dos métodos de mestre levou a cabo em uma praia rocosa do intermareal, na Ilha de Guadalupe, no Pacífico Nororiental Mexicano. A modificação do método tradicional permitiu censor e registrar valores de riqueza de espécies, abundância e diversidade de Shannon. De acuerdo a la prueba de Wilcoxon,
Numerical Experiments of Wind Circulation off Baja California Coast
Environmental Science and Engineering, 2013
ABSTRACT In order to study the effect of orography on winds off Baja California, the momentum pri... more ABSTRACT In order to study the effect of orography on winds off Baja California, the momentum primitive equations describing an atmospheric flow over that region are solved numerically on a boundary-fitted grid. Numerical experiments are conducted for several flow conditions. Results show a remarkable agreement to available obser-vations. Von Kármán vortex street shown in satellite images are also reproduced.
Aquaculture Potential of Mexican Coasts
Journal of Coastal Research, 2011
... OE Delgado-González † , JA Jiménez ‡ , I. Espejel § , JL Ferman-Almada †† , A. Martínez-Díaz-... more ... OE Delgado-González † , JA Jiménez ‡ , I. Espejel § , JL Ferman-Almada †† , A. Martínez-Díaz-de-León † , A. Mejía-Trejo † , and G. Seingier †† ... The Pacific coast of Mexico has a length of 7,800 km; approximately 70% of these shores are sandy, and 30% are rocky. ...
Water Resources Management and Modeling, 2012
Microplastic Pollution Found Across Trophic Levels in a Kelp Forest in Baja California
Air-Sea CO 2 fluxes and NEP changes in a Baja California Coastal Lagoon during the anomalous North Pacific warm condition in 2014
AGU Fall Meeting Abstracts, Dec 18, 2015
Seismic Noise Levels in Northern Baja California, Mexico
Bulletin of the Seismological Society of America, Feb 5, 2019
Influence of the advection of water masses in the Ballenas Channel on the CO2 system in Bahía de los Angeles (Mexico)
Regional Studies in Marine Science
The surface waters of the Ballenas Channel (BC) are characterized by thermohaline and biogeochemi... more The surface waters of the Ballenas Channel (BC) are characterized by thermohaline and biogeochemical conditions that depend on the water masses present. Since these surface waters are transported into Bahía de los Ángeles (BLA), it is relevant to assess their timing, intensity and biogeochemical implications on a seasonal scale. For this purpose, the seasonal and spatial variability of temperature, salinity, dissolved inorganic carbon (DIC) and total alkalinity (TA), were quantified over 19 discrete monthly monitoring campaigns that covered 12 stations in BLA from June 2017 to October 2019. In addition, vertical CTD profiles of thermohaline, apparent oxygen utilization (AOU), and nitrate were obtained for the purposes of identifying the water masses present and determining how they change by season. It was found that the dynamics of DIC, AOU, nitrate, and temperature in BLA respond to the presence of Subtropical Subsurface Water (SSW), evident by the enrichment of the bay with high DIC and nitrate concentrations during winter, but during summer occurs the opposite, with the presence of the Gulf of California Water (GCW). In addition, zonation analysis within BLA indicated three regions consistently found along the year, attributed to different physical and biogeochemical processes. Finally, we also interpreted the data in the context of the interannual variability due to ENSO events by using a relationship between observed temperature-DIC data. A 20-year calculated DIC (DIC calc) time series for an area near BLA indicated that during summer periods under the influence of La Niña events, the DIC cal in front to BLA could be 10-12 µmol kg −1 higher than El Niño events. These high DIC values, likely promoted by an increased volume of SSW in the BC, is accompanied by a higher nutrients concentration, suggesting that the interannual variability must interact with biological processes within BLA and other adjacent embayment's in this region.
Atmósfera, 2020
The influence of easterly and northeasterly dry and warm Santa Ana winds (SAw) on the surface cir... more The influence of easterly and northeasterly dry and warm Santa Ana winds (SAw) on the surface circulation of Todos Santos Bay, Mexico, is studied from surface currents and wind data measured during the most extreme periods of activity (autumn-winter season). Sea surface currents were measured using a system of coastally-based HF radar stations between 2009 and 2015. Winter-mean surface circulation showed a cyclonic tendency. Atmospheric variables allowed the grouping of ~122 SAw events, 23% of which caused a noticeable change in the background circulation. Event-mean current patterns showed dissimilar responses to the acting winds, with some SAw events driving weak offshore currents, another that developed an eddy-pair circulation inside the bay, and one rather intense (winds of 8-10 ms -1 ) that developed a clockwise circulation overturning the cyclonic long-term winter-mean. In general, changes in the circulation were related to an offshore transport of surface waters into the open ocean.
Agrociencia, 2017
espanolLa fisiologia de la vid (Vitis vinifera) esta regulada por las condiciones climaticas de m... more espanolLa fisiologia de la vid (Vitis vinifera) esta regulada por las condiciones climaticas de mesoescala y gran escala. El valle de Guadalupe es una cuenca vitivinicola que produce la mayoria del vino de Mexico y presenta variaciones climaticas en mesoescala que podrian influenciar la maduracion de las uvas. El objetivo de este estudio fue evaluar el efecto de las diferencias climaticas en dos zonas vitivinicolas del Valle de Guadalupe, sobre la maduracion de la uva variedad Nebbiolo. Debido a la distancia con respecto a la costa, se esperaban encontrar diferencias climaticas en el valle y en la maduracion de las uvas en las zonas de estudio. Durante cuatro temporadas, se evaluo concentracion de solidos solubles, acidez titulable y pH de uvas de la zona centro del Valle de Guadalupe y de la zona mas cercana al mar, San Antonio de la Minas (SAM), Baja California, Mexico. Ademas, se evaluo la temperatura, humedad relativa, irradiancia, precipitacion pluvial, y velocidad y direccion ...
An exploration of the population characteristics and behaviours of the white shark in Guadalupe Island, Mexico (2014–2019): Observational data from cage diving vessels
Aquatic Conservation: Marine and Freshwater Ecosystems, 2021
In the eastern North Pacific, the Guadalupe Island Biosphere Reserve (GIBR) is one of the most re... more In the eastern North Pacific, the Guadalupe Island Biosphere Reserve (GIBR) is one of the most renowned white shark (Carcharodon carcharias) aggregation sites studied to date, and an important tourism activity has been developed in the reserve. This study used tourist‐based cage diving activities to biologically monitor white sharks from 2014 to 2019 within the GIBR. The data indicated a gradual increase in the overall abundance of white sharks with an age‐structure shift, as young of the year and juvenile sharks were more prevalent during the latter part of the study period (2016–2019). The arrival of young of the year and juvenile white sharks coincided with regional changes in oceanographic conditions off California and Baja California. The arrival of adult female white sharks coincided with the seasonal peak in elephant seal abundance. Records of high‐risk white shark behaviours, a shift to sharks of younger ages, and the high prevalence of small individuals during cage diving a...
Impacts of the 2014-2015 warm-water anomalies on nutrients, chlorophyll-a and hydrographic conditions in the coastal zone of northern Baja California
We report the seasonal variability of temperature, nutrients, and total and size‐fractionated chl... more We report the seasonal variability of temperature, nutrients, and total and size‐fractionated chlorophyll‐a (Chl‐a) in nearshore waters off northern Baja California (nBC), under conditions of the marine heatwave and El Niño that occurred in the northeastern Pacific during 2014–2015. Compared with the mean annual cycle (2008–2015), our study period was characterized by warmer waters, nitrate‐impoverished, and with very low Chl‐a concentration, which was closely associated with strong stratification and reduced upwelling conditions off nBC. Temperature anomalies were >2.0°C by the end of 2014 when the marine heatwave prevailed, decreased during the spring‐early summer upwelling season of 2015, and returned to >2.5°C by the end of 2015 when El Niño appeared along the coast of nBC. As in 2008–2012 and closely coupled with upwelling, a seasonal cycle of total Chl‐a was recorded under these abnormally warm conditions. However, relative to the mean annual cycle, total Chl‐a and nitrate concentrations were significantly reduced (19%–55% and 40%–81%, respectively), with negative anomalies throughout the study period. Moreover, the seasonal evolution of the size‐fractionated Chl‐a concentration showed that smaller cells (<5 μm) systematically contributed with the largest fraction (>60%) of the total Chl‐a. Our findings indicate that the sequential occurrence of the marine heatwave in 2014 and El Niño in 2015 had a significant and sustained impact limiting the nitrate supply and reducing the total Chl‐a in nearshore waters off nBC. In conclusion, our data reveal that a shift toward an oligotrophic state occurred in coastal waters off nBC during the warm period of 2014–2015.
Estuarine, Coastal and Shelf Science, 2018
In this work we present the exchange flows between a semi-enclosed Bay and the adjacent ocean as ... more In this work we present the exchange flows between a semi-enclosed Bay and the adjacent ocean as measured by a real-time coastal observing system in Baja California, Mexico. Several sources of information as numerical modeling, currents profile data, high frequency radar observations and drifters tracking, all together show an interesting three-dimensional structure to the exchange flows. The northern entrance (relatively shallow, ~40 m at its deepest portion) showed an estuarine-like exchange pattern, with a net outflow at the shallow parts and inflow at the deepest, suggesting that the frictional effect is more important than the earth's rotation, as typically observed in relatively small bodies of water like estuaries and coastal lagoons. On the other hand, the southern entrance (with a ~400 m deep canyon) is more complex, with recurrent anticyclonic exchange pattern with inflows at the western limit and outflows at the east. We suggest that the vertical structure of this circulation may be sustained by the deep canyon which lowers the thermocline, but further investigation is needed.
Ciencias Marinas, 2017
A succession of interannual warm events occurred in the Pacific during the 2013–2016 period, when... more A succession of interannual warm events occurred in the Pacific during the 2013–2016 period, when positive thermal anomalies were detected. A broad region with abnormally warm waters in the northeastern Pacific Ocean was observed in 2013, which by 2015 had reached waters off Baja California (Mexico). In addition to the ongoing warming effect, early evidence of an El Niño event was detected in 2015. This paper analyzes hydrographic data measured at Todos Santos Bay and environs, as well as satellite-derived sea-level data, to characterize changes in the hydrographic conditions during the 2013–2016 period. The highest positive temperature anomalies (~5 ºC) were observed in September 2015, with a steep decline to neutral conditions in spring 2016. Records for the bay showed slight variations in hydrographic conditions during spring, highlighting the importance of local over remote forcings during this time of year. In autumn, by contrast, interannual signals prevailed over local proces...
Estuaries and Coasts, 2016
The present study examines the temporal variability of air-water CO 2 fluxes (FCO 2 ) and seawate... more The present study examines the temporal variability of air-water CO 2 fluxes (FCO 2 ) and seawater carbonate chemistry in a Baja California coastal lagoon during an exceptionally warm anomaly that was developed in Northeast Pacific coasts during 2014. This oceanographic condition led to a summer-like season (weak upwelling condition) during the study period, which reached a maximum surface temperature anomaly of 2 °C in September 2014. San Quintín Bay acts as a source of CO 2 to the atmosphere in 2014 (3.3 ± 4.8 mmol C m -2 day -1 ) with the higher positive fluxes mainly observed in summer months (9.0 ± 5.3 mmol C m -2 day -1 ). Net ecosystem production (NEP) switched seasonally between net heterotrophy and net autotrophy during the study period, with an annual average of 2.2 ± 7.1 mmol C m -2 day -1 , which indicates that San Quintín Bay was a net autotrophic system during the atypical warm oceanographic condition in 2014. This pattern of seasonal variations in the carbon balance at San Quintín Bay appears to be linked to the life cycle of benthic communities, which play an important role in the whole-ecosystem metabolism. Under the limited input from external sources coupled with an increase in seawater temperatures, the recycled benthic carbon and nutrient fluxes play a major role to sustain water-column processes within the bay. Since the upwelling condition may influence the magnitude of the air-water CO 2 fluxes, our results clearly indicated that San Quintín Bay is a net source of carbon to the atmosphere regardless of the adjacent oceanic conditions. Our study sheds light on the carbon dynamics and its metabolic implications in a shallow coastal ecosystem under a regional warm anomaly and contributes potentially relevant information in view of the likely future scenario of global climate change. Keywords Air-water CO 2 fluxes . Coastal upwelling . Ecosystem metabolism . Anomalous North Pacific warm condition . Baja California Communicated by Alberto Vieira Borges
Journal of Coastal Research, 2016
Concurrent measurements of subtidal beach morphology and profiles of nearshore currents have been... more Concurrent measurements of subtidal beach morphology and profiles of nearshore currents have been collected over a year period on a gently sloping mesotidal beach in the northwestern coast of the Baja California peninsula in Mexico. Data collected in August 2014 and February 2015 during similar tide, wave and wind conditions are compared at different alongshore locations on the beach in order to determine differences on the vertical structure of the nearshore currents in relation to significant morphologic variations. The beach presents a clear seasonal variability, showing the formation of an inner sandbar during the winter as a result of the erosion of a large portion of the subaerial beach. The morphological differences on the inner subtidal beach shows a subsequent effect on the vertical structure of the nearshore currents. Locations with pronounced sandbars have generally associated crossshore and longshore components of the current of larger magnitude. Generally, the surface and bottom cross-shore currents are the most energetic while the middle layer presents milder magnitudes. With the presence of an inner bar, the shoreward directed upper and bottom layers become wider (deeper) reducing the width of the middle less energetic layer, and after the breaking zone the water column becomes vertically quasi-homogeneous. This study contributes to the understanding of the feedbacks between the hydrodynamic forcing and the beach morphology.
On the sources of PBDEs in coastal marine sediments off Baja California, Mexico
Science of The Total Environment, 2016
Polybrominated diphenyl ethers (PBDEs) are widely distributed compounds in all types of matrices.... more Polybrominated diphenyl ethers (PBDEs) are widely distributed compounds in all types of matrices. In the northern portion of the Southern California Bight (SCB), there were reports of some of the largest PBDE concentrations in marine mammals and mussels. Because of this, we decided to analyze the status of PBDEs in the southern part of the SCB. An analysis of 91 samples of marine surface sediment was carried out. All of the 91 samples contained measurable amounts of PBDEs, which is a manifestation of the widespread distribution of these chemical substances. However, the levels detected are between one and two orders of magnitude smaller than those reported in southern California. Currents appear to control the distribution of PBDEs along the coast and the sedimentation sites with largest concentrations are favored by local bathymetry. Maximum concentrations were located in the middle and deeper platforms ranging from 0.02 to 5.90 (with a median 0.71) ng·g(-1) d.w. Deca-BDE mixture is largely predominant in the sediments followed by the penta-BDE mixture. The mass balance for the latitudinal strata shows the largest concentrations in the north where the largest population centers are present and with a very clear southward gradient. The mass balance calculation values showed about 36kg of PBDEs for the north, 22kg for the center, and 10kg for the south strata. In terms of depth, the PBDEs are mainly located on the middle and deep platforms rather than near point discharges, which is different than that reported by other authors.
Predicting Barrier Beach Breaching due to Extreme Water Levels at San Quntín, Baja California, Mexico
Journal of Coastal Research, 2014
ABSTRACT Vidal-Juárez, T.; Ruiz de Alegría-Arzaburu, A.; Mejía-Trejo, A.; García-Nava, H., and En... more ABSTRACT Vidal-Juárez, T.; Ruiz de Alegría-Arzaburu, A.; Mejía-Trejo, A.; García-Nava, H., and Enriquez, C., 2014. Predicting barrier beach breaching due to extreme water levels at San Quintín, Baja California, México. This study comprises a first approach to numerically determine the hydrodynamic conditions leading to barrier breaching at San Quintín, located in the northwestern coast of the Baja California peninsula in Mexico. The barrier is backed by a large coastal lagoon, fronted by a field of submerged volcanoes located several kilometers off the coast and is exposed to large incoming wave energy dominated by the Pacific swell. The narrowest barrier beach sections are vulnerable to flooding due to overwash events that take place during concurrent high spring tides, energetic storm waves and a range of storm surge levels. Here, the conditions to barrier overwash and breaching occurrence are identified, and the extent of the floods is numerically quantified. For that purpose, the Delft3D hydrodynamic model is applied coupling waves and flows to simulate a series of scenarios, which comprise storm waves of different magnitudes and periods approaching from typical directions, and coupled to spring tides and several storm surge levels. As a consequence of the presence of submerged volcanoes off the coast, the incoming wave energy is mostly concentrated at two specific locations along the barrier beach, which correspond to the lowest and narrowest barrier locations. Due the large distance between both sites, longshore variations are not expected to be as strong as the cross-shore. Numerical results suggest that the barrier is susceptible to flooding during spring tides combined with extreme waves of significant wave heights larger than 3.5 m and a peak period of 7.5 s, and storm surge levels exceeding 0.9 m, which may lead to breaching.
Estuarine, Coastal and Shelf Science, 2011
The role of coastal lagoons and estuaries as sources or sinks of inorganic carbon in upwelling ar... more The role of coastal lagoons and estuaries as sources or sinks of inorganic carbon in upwelling areas has not been fully understood. During the months of MayeJuly, 2005, we studied the dissolved inorganic carbon system in a coastal lagoon of northwestern Mexico during the strongest period of upwelling events. Along the bay, different scenarios were observed for the distributions of pH, dissolved inorganic carbon (DIC) and apparent oxygen utilization (AOU) as a result of different combinations of upwelling intensity and tidal amplitude. DIC concentrations in the outer part of the bay were controlled by mixing processes. At the inner part of the bay DIC was as low as 1800 mmol kg À1 , most likely due to high water residence times and seagrass CO 2 uptake. It is estimated that 85% of San Quintín Bay, at the oceanic end, acted as a source of CO 2 to the atmosphere due to the inflow of CO 2 -rich upwelled waters from the neighboring ocean with high positive fluxes higher than 30 mmol C m À2 d À1 . In contrast, there was a net uptake of CO 2 and HCO 3 À by the seagrass bed Zostera marina in the inner part of the bay, so the pCO 2 in this zone was below the equilibrium value and slightly negative CO 2 fluxes of À6 mmol C m À2 d À1 . Our positive NEP and DDIC values indicate that Bahía San Quintín was a net autotrophic system during the upwelling season during 2005.
Ciencias Marinas, 2010
An index was created for the spatial classification of oyster cultivation areas in terms of their... more An index was created for the spatial classification of oyster cultivation areas in terms of their potential productivity in Falsa Bay, San Quintín (Baja California, Mexico). The index included two main variables crucial for oyster development: food availability and depth. Food availability was based on the final distribution of particulate organic material; it is a passive variable that is transported by tidal currents. A balance was obtained between the volume incorporated into the bay by tidal inflow and its consumption by the organisms distributed in the cultivated areas, which are characterized by the percentage of cultivated areas within the bay. The distribution area of depth was obtained from a five-interval classification scale that allowed the identification of the highest and least exposure of the cultivation area to the proposed food availability. Both criteria were combined into one value in order to divide the bay region into zones in relative terms and determine which ...
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Papers by adan mejia-trejo