Papers by Victor Camacho-Ibar
Subtidal circulation in San Quintin Bay, Mexico, a Mediterranean coastal lagoon
nerc.ac.uk. ...
Impacts of mesoscale eddies on the nitrate distribution in the deep-water region of the Gulf of Mexico
Journal of Marine Systems, May 1, 2022
Deep-sea Research Part I-oceanographic Research Papers, Dec 1, 2015
In order to characterize the carbon biomass spatial distribution of autotrophic and heterotrophic... more In order to characterize the carbon biomass spatial distribution of autotrophic and heterotrophic picoplankton populations linked to mesoscale dynamics, an investigation over an extensive open-ocean region of the southern Gulf of Mexico (GM) was conducted. Seawater samples from the mixed layer were collected during wintertime (February-March 2013). Picoplankton populations were counted and sorted using flow cytometry analyses. Carbon biomass was assessed based on in situ cell abundances and conversion factors from the literature. Approximately 46% of the total picoplankton biomass was composed of three autotrophic populations (Prochlorococcus, Synechococcus, and pico-eukaryotes), while 54% consisted of heterotrophic bacteria populations. Prochlorococcus spp. was the most abundant pico-primary producer ( 480%), and accounted for more than 60% of the total pico-autotrophic biomass. The distribution patterns of picoplankton biomass were strongly associated with the mesoscale dynamics that modulated the hydrographic conditions of the surface mixed layer. The main features of the carbon distribution pattern were: (1) the deepening of picoplankton biomass to layers closer to the nitracline base in anticyclonic eddies; (2) the shoaling of picoplankton biomass in cyclonic eddies, constraining the autoprokaryote biomasses to the upper layers, as well as accumulating the pico-eukaryote biomass in the cold core of the eddies; and (3) the increase of heterotrophic bacteria biomass in frontal regions between counter-paired anticyclonic and cyclonic eddies. Factors related to nutrient preferences and light conditions may as well have contributed to the distribution pattern of the microbial populations. The findings reveal the great influence of the mesoscale dynamics on the distribution of picoplankton populations within the mixed layer. Moreover, the significance of microbial components (especially Prochlorococcus) in the southern GM during winter conditions was revealed, indicating that they may play an important role in the pelagic food web, and that they may have a substantial impact on the carbon cycle in oligotrophic regions.
Water Mass Structure and Mixing Fractions in the Deepwater Region of the Gulf of Mexico
Journal of Geophysical Research: Oceans
Evaluation of the saturation state of Aragonite, at Baja California Coast, Mexico
AGU Fall Meeting Abstracts, Dec 1, 2012
Biogeosciences, Dec 15, 2017
Chlorophyll concentration is a key oceanic biogeochemical variable. In the Gulf of Mexico (GOM), ... more Chlorophyll concentration is a key oceanic biogeochemical variable. In the Gulf of Mexico (GOM), its distribution, which is mainly obtained from satellite surface observations and scarce in situ experiments, is still poorly understood. In 2011-2012, eight profiling floats equipped with biogeochemical sensors were deployed for the first time in the GOM and generated an unprecedented dataset that significantly increased the number of chlorophyll vertical distribution measurements in the region. The analysis of these data, once calibrated, permits us to reconsider the spatial and temporal variability of the chlorophyll concentration in the water column. At a seasonal scale, results confirm the surface signal seen by satellites, presenting maximum concentrations in winter and low values in summer. It is shown that the deepening of the mixed layer is the primary factor triggering the chlorophyll surface increase in winter. In the GOM, a possible interpretation is that this surface increase corresponds to a biomass increase. However, the present dataset suggests that the basin-scale climatological surface increase in chlorophyll content results from a vertical redistribution of subsurface chlorophyll and/or photoacclimation processes, rather than a net increase of biomass. One plausible explanation for this is the decoupling between the mixed-layer depth and the deep nutrient reservoir since mixed-layer depth only reaches the nitracline in sporadic events in the observations. Float measurements also provide evidence that the depth and the magnitude of the deep chlorophyll maximum is strongly controlled by the mesoscale variability, with higher chlorophyll biomass generally observed in cyclones rather than anticyclones.
Marine Environmental Research, 1996
The concentrations of 55 congeners of PCBs were determined in < 500 pm particles of 66 superficia... more The concentrations of 55 congeners of PCBs were determined in < 500 pm particles of 66 superficial sediment samples from Liverpool Bay. Total PCBs were significantly (p < 0.001) correlated with the amount offine particles (r2 = 0.81) and with the organic carbon content (9 = 0.80). The mean, maximum and minimum total PCB values were 3938, 37,880 and 82 pg g-', respectively. The highest PCB concentrations were found in muddy deposits, particularly near the River Mersey in the Burbo Bight area, where concentrations were above 13,000 pg g-t. Values lower than 3.50 pg g-' were found in the sandy southern area towards the North Wales coast.
Combined effects of marine heatwaves and reduced light on the physiology and growth of the surfgrass Phyllospadix torreyi from Baja California, Mexico
Aquatic Botany, 2022
Frontiers in Marine Science, May 19, 2022
d'e ´tudes en ge ´ophysique et oce ´anographie spatiales (LEGOS), France
Journal Of Geophysical Research: Oceans, Nov 1, 2019
Picoplankton carbon biomass assessments reveal the importance of the microbial community in the... more Picoplankton carbon biomass assessments reveal the importance of the microbial community in the pelagic ecosystem of the Gulf of Mexico High-Light and Low-Light Prochlorococcus ecotypes are most evident during summertime in the deep-water region of the Gulf of Mexico Loop Current Eddies transport deep Prochlorococcus subgroups to the western region of the Gulf of Mexico
Journal of Marine Systems, Apr 1, 2019
Zooplankton was sampled in the Southern Gulf of Mexico, during autumn 2010, summer 2011 and winte... more Zooplankton was sampled in the Southern Gulf of Mexico, during autumn 2010, summer 2011 and winter 2013. Hydrographic data, dynamic topography and geostrophic velocities showed the presence of alternating cyclonic and anticyclonic gyres in the area, and a quasi-permanent gyre in the Bay of Campeche, with higher surface temperatures and lower salinities during autumn and summer, than in winter. Stronger rainfall was present during summer, which coincided with a strong salps "bloom" that considerably increased biovolumes. A significant difference in biovolumes was found for the three seasons, with highest zooplankton biovolumes during summer, and lowest during autumn. A shoaling of higher fluorescence and higher nutrients (Nitrate + Nitrite) was found in the BOC, in coincidence with higher biovolumes during the three seasons sampled. Multivariate analysis showed that the variables controlling the productivity were mainly fluorescence and nutrients for summer 2011 and winter 2013. Higher biovolumes were present in autumn, summer and winter at the same stations, being higher during summer. Data obtained show that the Bay of Campeche is a high productivity area, all year round, particularly inside the quasi-permanent gyre where high biovolumes were present in autumn, summer and winter, but with considerable seasonal variations in primary and secondary productivity, probably dependent in great measure from river discharge and rainfall.
Estuaries and Coasts, Aug 21, 2015
Shellfish aquaculture is prominent in many coastal and estuarine environments and has both ecolog... more Shellfish aquaculture is prominent in many coastal and estuarine environments and has both ecological and economic impacts. Bahía San Quintín is a reverse estuary in Baja California, Mexico, where Pacific oysters (Crassostrea gigas) are cultivated. While oysters likely feed heavily on phytoplankton especially during upwelling periods, we hypothesized that other forms of organic matter such as seagrass (Zostera marina) and macroalgae (Ulva spp.) must also be used by the oysters, especially in the most inshore portions of the bay. We measured the carbon and hydrogen stable isotope composition of oysters and their potential food resources at upper, mid, and lower bay sites during upwelling and nonupwelling seasons and applied a Bayesian mixing model to evaluate resource use. Hydrogen isotopes provided a large separation between potential food resources. Although we did not find any strong seasonal effects due to upwelling, there was a strong spatial gradient in resource use. Phytoplankton were most important at the lower (oceanic) site (median resource use for two sampling times, 68 and 79 %) and decreased up the estuary as macroalgae became more important (43 and 56 % at the upper site). At all sites for both sampling times, seagrass was an unimportant resource for oysters. The contrast between high phytoplankton use at the lower site and increased macroalgal use at the upper site is likely due to available resource biomass. Results indicate the adaptability of oysters to varying resource availability and the possibility of a higher system carrying capacity than that based on phytoplankton alone given multiple potential food sources. This study also highlights the utility of hydrogen isotopes in estuarine food web research.
Estuarine systems of the Latin American region (regional workshop v) and estuarine systems of the Arctic region : carbon, nitrogen and phosphorus fluxes
Nitrogen sources (NO3− vs N2 fixation) inferred from bulk δ15N values of zooplankton from the deep water region of the Gulf of Mexico
Journal of Plankton Research, 2021
Dinitrogen (N2) fixation is an important source of new N in oceanic oligotrophic waters, but its ... more Dinitrogen (N2) fixation is an important source of new N in oceanic oligotrophic waters, but its contribution has not been quantified in the central and southern Gulf of Mexico (GM), where mesoscale anticyclonic (ACE) and cyclonic eddies (CE) influence NO3− availability for phytoplankton. We investigated the temporal and spatial variation in zooplankton δ15N values as a proxy for baseline nitrogen sources and estimated the contribution of N2 fixation and subsurface nitrate to secondary production. Copepods, euphausiids and two size classes of zooplankton were collected from 0 to 200 m during five cruises. Zooplankton δ15N values were higher during winter due to wind-driven deepening of the mixed layer, reflecting NO3− transport toward the surface. There was a higher estimated contribution of N2 fixation during the highly stratified summer months. Zooplankton δ15N values from ACEs were significantly lower than in CE, associated with a deepening of the 25.5 isopycnal and lower depth-i...
Ecological Modelling, 2020
San Quintín Bay (SQB) is a coastal lagoon fertilized with cold, nutrient rich, marine water, that... more San Quintín Bay (SQB) is a coastal lagoon fertilized with cold, nutrient rich, marine water, that sustains the high productivity within the bay, in particular during upwelling events. The variations in the oceanic exchanges -and in particular changes in upwelling intensity and frequency, also related to climate change-are expected to alter the biogeochemical processes in SQB and in the other coastal systems along the California Current domain with possible impacts on the trophic state. The extent of this influence is tested here developing and applying a 3-D coupled physical-ecological model (SHYFEM-SQBFEEM), contrasted with data. Simulations included a reference scenario (REF) of typical upwelling conditions, observed in spring 2004, and two scenarios of low (LOW) and high (HIGH) upwelling conditions, observed, respectively during spring 2016 and 2005. We calculated the Nbudget for the three scenarios, highlighting the response of primary and secondary producers, including oyster potential production, to the changes in upwelling intensity. The model shows that upwelling intensity has a large influence on N availability and consumption within the bay, and on the response of primary and secondary producers. Differences of the nitrogen stocks of primary and secondary producers under HIGH and LOW upwelling conditions are of around 25 % for phytoplankton, 20 % for oyster and more than 40 % for zooplankton.
Chlorinated Hydrocarbons in Skin and Blubber of Two Blue Whales ( Balaenoptera musculus ) Stranded Along the Baja California Coast
Bulletin of Environmental Contamination and Toxicology, 2004
... XXVI Reunión Internacional para el Estudio de los Mamíferos Marinos. Ensenada, BC México, p 6... more ... XXVI Reunión Internacional para el Estudio de los Mamíferos Marinos. Ensenada, BC México, p 65 Gauthier JM, Metcalfe CD, Sears R (1997) Validation of the blubber biopsy technique for monitoring of organochlorine contaminants in Balaenopterid whales. ...
Estuaries, Oct 1, 2003
is a hypersaline coastal lagoon where the main external forcing of physical and biogeochemical pr... more is a hypersaline coastal lagoon where the main external forcing of physical and biogeochemical processes is oceanic. Non-conservative fluxes of inorganic N (⌬DIN) and P (⌬DIP), and aspects of net ecosystem metabolism were studied in this lagoon during August 1995, August 1996, and February 1996, by following the LOICZ budgetary modeling approach. The whole-system water exchange time during summer (ϳ13 d) was shorter than in winter (ϳ26 d) as northwesterly winds enhancing mixing with the ocean are more intense during the springsummer upwelling season. Whole-bay ⌬DIP values of ؉0.2 to ؉0.3 mmol m Ϫ2 d Ϫ1 in August, and Ͻ؉0.01 mmol m Ϫ2 d Ϫ1 in February indicate that the system is a net source of dissolved inorganic phosphorus (DIP). DIP fluxes from the Bay to the ocean during August are probably balanced by a net import of particulate organic matter between 1,000-1,300 ؋ 10 3 mol C d Ϫ1 , equivalent to a net ecosystem production (NEP) between Ϫ24 and Ϫ31 mmol C m Ϫ2 d Ϫ1. ⌬DIN showed opposite trends in August 1995 and August 1996, with a net import of 13 ؋ 10 3 mol N d Ϫ1 and a net export of 30 ؋ 10 3 mol N d Ϫ1 , respectively. However, N fixation minus denitrification (''apparent denitrification'') estimates of ϳϪ4 mmol N m Ϫ2 d Ϫ1 in both periods indicate that San Quintin Bay is a net sink of nitrogen. Results from a 3-box model indicate that during summer Box C, adjacent to the ocean, contributed 70-80% of the excess DIP produced in the whole-system. This observation and high apparent denitrification values of ϳϪ7 mmol N m Ϫ2 d Ϫ1 at the entrance of the Bay, suggest that the net heterotrophic condition of San Quintin Bay in summer is largely determined by imports of labile phytoplanktonic carbon generated in the adjacent ocean during upwelling. A net flux of organic carbon of 30 ؋ 10 6 mol C yr Ϫ1 was estimated from Box C, adjacent to the ocean, to Box B, locally known as Bahia Falsa, which is the area designated for oyster aquaculture in the lagoon. It is estimated that this net organic carbon supply is almost equivalent to the annual oyster food demand; our estimate is that oyster aquaculture in San Quintin Bay accounts for the vast majority of the net heterotrophy of Bahia Falsa.
Journal of Marine Science and Engineering, Jul 18, 2020
In this study, we report the response of phytoplankton community composition to cold and warm int... more In this study, we report the response of phytoplankton community composition to cold and warm interannual events affecting the waters off the Baja California Peninsula from 2007 to 2016 based on data obtained from a single marine station (31.75 • N/116.96 • W). Included variables were satellite chlorophyll a, sea surface temperature (MODIS/Aqua), upwelling intensity, and field data (phytoplankton pigments, inorganic nutrients, light penetration). Phytoplankton pigments were determined by high performance liquid chromatography, and CHEMTAX software was used to determine the relative contributions of the main taxonomic groups to chlorophyll a. Our results confirm the decrease in phytoplankton biomass due to the influence of the recent Pacific Warm Anomaly (2014) and El Niño 2015-2016. However, this decrease was especially marked at the surface. When data from the entire water column was considered, this decrease was not significant, because at the subsurface Chla did not decrease as much. Nevertheless, significant changes in community composition occurred in the entire water column with Cyanobacteria (including Prochlorococcus) and Prymnesiophytes being dominant at the surface, while Chlorophytes and Prasinophytes made a strong contribution at the subsurface. Analysis of the spatial distribution of SST and satellite chlorophyll a made it possible to infer the spatial extension of these anomalies at a regional scale.
Ciencias Marinas, 2004
Procesos abióticos como la resuspensión sedimentaria pueden contribuir a los flujos no conservati... more Procesos abióticos como la resuspensión sedimentaria pueden contribuir a los flujos no conservativos del fósforo inorgánico disuelto (PID) en sistemas someros como Bahía San Quintín (BSQ), ya que los sedimentos resuspendidos pueden adsorber o desadsorber fósforo inorgánico. Se determinó en el laboratorio, mediante experimentos de adsorción-desadsorción, la contribución de los sedimentos en suspensión a las concentraciones del PID observadas en la columna de agua de BSQ variando el tipo de sedimento (arena fina y limo arenoso) en suspensión y su concentración, la concentración inicial de PID y el tiempo de resuspensión. En la primera etapa del proceso de adsorción (etapa rápida), ocurrida antes de las 10 h, se observó la concentración de fósforo en equilibrio (EPC 0 , por sus siglas en inglés). En sedimentos expuestos a > 24 h de resuspensión, la EPC 0 fue rebasada, indicando la movilización del P de la superficie hacia el interior de las partículas (etapa lenta). La adsorción fue el proceso dominante en los experimentos y, al aumentar la cantidad de sedimento resuspendido, los procesos de adsorción-desadsorción se acentuaron. Al comparar los flujos no conservativos de PID obtenidos con el modelo de LOICZ y los obtenidos en los experimentos de resuspensión, se observa que la adsorción del PID por las partículas puede generar una subestimación de ~20% de la heterotrofía neta del sistema, ya que la remoción de PID por adsorción enmascara su adición por la respiración neta de la comunidad.