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Habitat characterization provides predictive information about the distribution of species and is useful for as­sessing habitat quality and population stability. Larval abundance of six frequent and abundant demersal species and the relationship of each with the environment were analysed through generalized additive models to determine their preferential distribution and predictive response to the environmental variables in the southern part of the California Current (25-31°N) between two periods of data collection: 1997-2000 and 2006-2010. Essentially, the main associated variables governing the distribution patterns were related to common and oceanographic characteristics of the water column (temperature and salinity at 50 m depth, dynamic height and degree of water column stratification); however, the set of variables and their ranges are usually species-specific. Species of northern distribution, Sebastes sp. and Citharichtys stigmaeus, were recorded mainly in newly emerged, relatively unstratified waters characterized by a shallow mixed layer and low temperatures. Low dynamic height values were the most significant predictor of larval distribution for Merluccius productus. Citharichthys xanthostigma and Symphurus atricaudus were widespread, distributed across the study area mainly in autumn in unstratified or stratified waters and at a shallow mixed layer. Particularly C. Xanthostigma and S. Lucioceps were related to high dynamic height val­ues, likely influenced by a coastal flow towards the pole, as evidenced by counter-currents. La caracterización del hábitat proporciona información predictiva sobre la distribución de las especies y es útil para evaluar la calidad del hábitat y estabilidad de la población. La abundancia larval de seis especies demersales frecuentes y abundantes y de su relación con el medio ambiente se analizaron a través de modelos aditivos generalizados (GAM) para determinar su distribución preferencial y respuesta a las variables ambientales en la parte sur de la corriente de California (25-31°N) entre dos periodos de datos recolectados 1997-2000 y 2006-2010. Esencialmente, las principales variables aso­ciadas que rigen los patrones de distribución fueron en términos de las variables comunes y oceanográficas de la columna de agua (temperatura y salinidad a 50 m de profundidad, altura dinámica y grado de estratificación de la columna de agua), sin embargo, el conjunto de variables y los rangos suelen ser específicos de la especie. Especies con distribución norteña, Sebas­tes sp. y Citharichtys stigmaeus, se registraron principalmente en aguas de surgencia, identificadas por aguas relativamente no estratificadas, poca profundidad de capa mixta y menor temperatura; y menor altura dinámica, como el predictor más significativo de la distribución de larvas de Merluccius productus. Citharichthys xanthostigma y Symphurus atricaudus se distribuyeron ampliamente a lo largo del área de estudio preferentemente en otoño, en aguas no estratificadas o estratificadas y baja profundidad de la capa de mezcla, pero particularmente C. Xanthostigma y S. Lucioceps en valores altos de alturas dinámicas probablemente influenciadas por el flujo costero hacia el polo indicado por las contracorrientes.

Atlantids are holoplanktonic gastropods present in tropical to sub-polar waters, and have gained an increasing interest due to their potential use as biological indicators of climate change and ocean acidification. However, there is a lack of information regarding their distribution for large areas of some oceans, particularly in the California Current System (CCS), which has been used as a model for many acidification studies and where intense warming events occur. The distribution patterns of 18 species of Atlantidae off the west coast of the Baja California Peninsula, Mexico, representing 90% of the atlantid species registered for the Pacific Ocean, were analyzed during a period of warm anomalies associated with the El Niño of 2015-2016 and the 2014-2016 marine heat wave (MHW). The species distribution showed 3 groups: 2 in the north (coastal and oceanic) and 1 in the south. The limit of distribution between these 3 groups was found in the vicinity of Punta Eugenia (PE). The southernmost community of atlantids was characterized by tropical and subtropical species that were transported northward due to coastal advection of warm waters associated with the El Niño of 2015-2016. North of PE, the warm-water affinity oceanic speciesAtlanta roseaandA. fragiliswere found, evidencing the entrance of water from the Central Pacific related to MHW which affected the oceanic region off the coast of PE. The response of the distribution patterns proves that atlantids can be used as biological indicators, as they reflect the effect of environmental anomalies in the southern CCS.

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 m s–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.

Anomalies occurring in the California Current System during 2013–2016 were examined using remote sensing data and in-situ measurements. Positive anomalies in sea surface temperature (SST, up to 4 °C) and absolute dynamic topography (ADT, up to 20 cm), as well as negative anomalies in satellite chlorophyll concentration (CHL, up to -3.0 mg m -3 ) were recorded. In-situ temperature anomalies in August 2014 increased equatorward, from 2°C along the northernmost line (CalCOFI hydrographic line 76.7) to 10 °C (below ~80 m depth) at the southernmost hydrographic line (off Baja California). In-situ negative Chlorophyll- a (Chl- a ) surface anomalies were similar in most of the lines examined (~ -1.5 mg m -3 ), but for the CalCOFI lines, larger anomalies (~ -3.5 mg m -3 ) were recorded. As a result of increased stratification, mirrored in the increase in mean monthly ADT and the upper water-column temperature, the 2003–2016 CHL time series showed a declining trend in phytoplankton production and biomass, which was particularly pronounced during the last four years in the central and southern zones of the California Current System. The mechanisms responsible for this trend seem to be related to a climate shift from cold to warm in the northeastern Pacific Ocean, as evidenced by large correlations between the CHL anomalies and the Pacific Decadal Oscillation, Multivariate ENSO Index, and Oceanic El Nino indices. Generalized additive models were used to explore the relationship between stratification and the decline in phytoplankton production. Two ADT ranges—characteristic of either highly dynamic or stratified environments—were defined, both of which led to a drop in primary production. The effects of these environments have been associated with the photo acclimation of phytoplankton to irradiance and nutrient availability regimes, by which primary production and biomass decrease due to the limitation of either of these factors. This study reveals some of the effects of the warm anomalies occurring from 2013 to 2016 in the California Current ecosystem, which will help to understand changes in higher trophic levels in this region.

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 Nino 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 processes. Satellite-derived sea-level data revealed an alongshore propagation of remote signals, identified as shallow coastal poleward flows. En el periodo 2013–2016 se presento en el Pacifico una sucesion de eventos calidos de escala interanual, durante los cuales se manifestaron anomalias termicas positivas. Durante 2013 se observo una region muy extensa de aguas anomalamente calidas, la cual se formo en el Pacifico nororiental y, para 2015, se extendio hacia aguas frente a Baja California (Mexico). Tambien en 2015, ademas del efecto de calentamiento ya existente, se registraron las primeras evidencias de un evento El Nino. En este trabajo se analizan los datos hidrograficos medidos en la bahia Todos Santos y sus alrededores, asi como datos satelitales del nivel del mar, para caracterizar los cambios en las condiciones hidrograficas durante el periodo 2013–2016. Las observaciones mostraron las maximas anomalias positivas de temperatura (~5 oC) durante septiembre de 2015 y un rapido decaimiento hacia condiciones neutras en la primavera de 2016. Los registros para la bahia mostraron cambios leves en las condiciones hidrograficas durante la primavera, lo cual evidencio la importancia de los forzamientos locales sobre los forzamientos remotos en esa epoca del ano. En contraste, en otono las senales interanuales dominaron sobre los procesos locales. El analisis de datos de altimetria sugirio una conectividad entre el norte y sur frente a la peninsula a traves de la propagacion de senales, identificadas como un flujo costero superficial hacia el polo.

The ocean off the Baja California Peninsula (Mexico) has been affected by interannual processes. Some of these processes have produced changes in oceanic circulation and the atmosphere, which have been reflected in the structure of the water column. Stratification, defined as the amount of energy needed to mix water throughout the water column, determines nutrient availability in the euphotic zone for phytoplankton growth. The aim of this study is to describe and relate the interannual variations of phytoplankton production and biomass with changes in the structure of the water column. To this end, we analyzed time series (1997–2016) for integrated Chlorophyll a, integrated primary production, pycnocline depth, mixed layer depth, and stratification indices along line 100 of the Investigaciones Mexicanas de la Corriente de California (IMECOCAL) program. The results showed 2 periods of high stratification and a decrease in phytoplankton production and biomass off Baja California, corresponding to the intrusion of subarctic water and El Nino 2015–2016. Finally, by using generalized additive models, we related 2 photosynthethic parameters-maximum photosynthetic rate and maximum light utilization coefficient-with water stratification. These relationships explained interannual variations in phytoplankton production in terms of water column stratification. The time series and the analysis reported here for IMECOCAL line 100 could be used to extrapolate the effects of interannual physical processes on phytoplankton in other zones off the Baja California peninsula. El oceano frente a las costas de la peninsula de Baja California ha sido afectado por diferentes procesos interanuales. Algunos de estos procesos han generado cambios en la circulacion oceanica y en la atmosfera que se han reflejado en la estratificacion de la columna de agua. La estratificacion, definida como la cantidad de energia necesaria para mezclar una columna de agua, determina la disponibilidad de nutrientes necesarios para el crecimiento del fitoplancton. El objetivo de este articulo es describir y relacionar las variaciones interanuales de la biomasa y produccion del fitoplancton con la estructura de la columna de agua. Para esto, se analizaron las series de tiempo (1997–2016) de clorofila a y produccion primaria integradas, profundidad de la picnoclina y de la capa de mezcla y los indices de estratificacion entre la superficie y los 100 y 200 m en la Linea 100 del programa Investigaciones Mexicanas de la Corriente de California (IMECOCAL). Los resultados mostraron que los periodos de mayor estratificacion en la columna de agua fueron durante la intrusion de agua subartica 2002–2007 y El Nino 2015–2016, los cuales trajeron como consecuencia el mayor declive en la biomasa del fitoplancton (en ambos periodos) y de produccion primaria (durante El Nino 2015–2016) en la zona norte frente a Baja California. Finalmente, se relacionaron la tasa fotosintetica maxima y el coeficiente de utilizacion maxima de la luz, con el indice de estratificacion por medio de modelos aditivos generalizados. Estas relaciones explicaron las variaciones interanuales en la produccion primaria en correspondencia con la estratificacion de la columna de agua. Las series de tiempo y el analisis presentado aqui para la linea 100 del IMECOCAL podran ser extrapoladas a otras zonas frente a la peninsula para entender la relacion entre los procesos fisicos con la biomasa y produccion primaria del fitoplancton. Palabras clave: fitoplancton, estratificacion, produccion primaria, Baja California, MECOCAL.

Threshold is defined as the point where small changes in an environmental driver produce large responses in the ecosystem. Generalized additive models (GAMs) were used to estimate the thresholds and contribution of key dynamic physical variables in terms of phytoplankton production and variations in biomass in the tropical-subtropical Pacific Ocean off Mexico. The statistical approach used here showed that thresholds were shallower for primary production than for phytoplankton biomass (pycnocline 0 cm d-1 vs. ADT 4 cm d-1). The relatively high productivity on seasonal (spring) and interannual (La Nina 2008) scales were linked to low ADT (45-60 cm), and shallow pycnocline depth (9-68 m), and mixed layer (8-40 m). Statistical estimations from satellite data indicated that the contribution of ocean circulation to phytoplankton variability was 18% (for phytoplankton biomass), and 46% (for phytoplankton production). Although the statistical contribution of models constructed with in-situ integrated chlorophyll-a and primary production data was lower than the one obtained with satellite data (11%), the fits were better for the former, based on the residual distribution. The results reported here suggest that estimated thresholds may reliably explain the spatial-temporal variations of phytoplankton in the tropical-subtropical Pacific Ocean off the coast of Mexico.

An analysis was conducted of the community structure variability of demersal fish larvae and its relationship with environmental forcing on the west coast of the Baja California Peninsula (25–31°N). The information comes from two data sets of oceanographic cruises in 1997–2000 and 2006–2010. From a total of 190 identified taxa, a high number of species (71) was shared throughout the peninsula. The spatiotemporal contrast in the community structure suggests the separation of two groups (northern and southern) whose boundary is located around Punta Eugenia. The northern group showed an alternate dominance of species with a subarctic-transitional faunistic affinity during the winter and spring and species of a subtropical affinity during summer–autumn. In contrast, the dominant taxa in the southern group have a tropical–subtropical affinity throughout the year, although some taxa of subarctic-transitional affinity also occur during winter–spring. In the spatiotemporal scale, these results suggest tha...

The hydrographic structure and circulation of the Southern Mexican Pacific, from August 31 to September 24 2004, when tropical atmospheric activity was at its peak, was analyzed based on AVISO absolute dynamic topography and an array of 106 CTD profiles, within an area of about 500 km×500 km between Punta Maldonado and Puerto Chiapas. The surveyed area was occupied by mesoscale anticyclonic and cyclonic eddies that determined the path of water with temperature and salinity characteristic of the Costa Rica Coastal Current. The origin of each eddy was investigated with respect to QuikSCAT wind conditions. The sequence of AVISO images and wind data showed that the largest anticyclonic eddies originated outside the Gulf of Tehuantepec through mechanisms distinct from local wind forcing, although two northerly wind events in the Gulf of Tehuantepec possibly had an influence on the smallest anticyclonic and cyclonic eddies. The relative position of each eddy allowed the flow of relatively low temperature and salinity water (the Costa Rica Coastal Current) into and throughout the Gulf of Tehuantepec, converging at about Puerto Angel with relatively high temperature and salinity water moving from the west.

The distribution of ichthyoplankton assemblages (summer 1999 and winter 2000) from the southern region of the California Current (CC) off the Baja California Peninsula were analyzed. Latitudinal and ocean-coast distribution limits of the assemblages were associated with the geostrophic flow, which showed the presence of cyclonic and anticyclonic eddies in the northern and central region of the Baja California Peninsula. The comparative analysis of distribution and abundance of the developmental stages (egg to preflexion, flexion, and postflexion larval stages), showed that each mesoscale eddy had a specific ichthyoplankton assemblage, and the ichthyogeographic regionalization of the study area was determined by the presence of eddies and fronts. Retention processes were observed on epipelagic and demersal species where the fish larvae were maintained near the coastal region. Normal 0 21 false false false ES X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabla normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Calibri",sans-serif;}

13 pages, 11 figures, 2 tables, Sediment traps were deployed at two depths (300 m and 1200 m) off Monterey Bay (36°40′N and 122°25′W, Central California) for 7.3 years (1998–2005). The sediment trap data provided information about the quantity and quality of settling material, and allowed exploration of the relationship of the sinking material with the environmental conditions in this coastal upwelling region. The magnitude and composition of the settling material were highly variable over time. Organic carbon (Corg) fluxes ranged between 4–296 mg C m−2 day−1 and 0.1–142 mg C m−2 day−1 for shallow and deep sediment traps, respectively. The time series of Corg vertical flux was characterized by pulses of intense fluxes that were associated with peaks of primary production, generally during upwelling periods. Despite considerable variability, fluxes varied seasonally with highest values during the upwelling season and the lowest in winter. Attenuation of Corg vertical fluxes with depth (300 m vs. 1200 m) varied between 31% and 24% except for the late upwelling period, when there was an increase with depth likely due to resuspension of material from Monterey Canyon. Calculation of a seasonal vertical budget of organic carbon off Monterey Bay resulted in a transfer between 4.0% and 4.9% of the primary production to the deep ocean, suggesting that coastal upwelling efficiently sequestered CO2, The principal source of support for these measurements was the David and Lucile Packard Foundation. CGC was partially supported by a National Research Council Fellowship at the Naval Postgraduate School

espanolEntre 1997 y 2016, en el programa de Investigaciones Mexicanas de la Corriente de California (IMECOCAL) se realizaron medi-ciones de clorofila a y produccion del fitoplancton frente a la peninsula de Baja California. En este trabajo se resumen los resultados del periodode observaciones. Se encontro que la productividad promedio fue alta en zonas de surgencias costeras, y en el giro ciclonico semipermanente frente a punta Eugenia. A escala estacional, la variacion de la produccion primaria fue diferente a la de la clorofila a integrada. La clorofila aintegrada presento maximos durante la epoca de surgencias costeras en primavera y verano, y minimos durante la influencia de agua calida de origen tropical-subtropical en la zona al sur de punta Eugenia en otono e invierno. Los mayores valores de produccion primaria integrada ocurrieron en primavera y verano al norte de punta Eugenia y en invierno y otono al sur de esta localidad. Esta variabilidad se relaciono con la presencia de fitoplancton de ciertos tamanos y sus tasas fotosinteticas maximas caracteristicas. A escala interanual, la menor productividad estuvo asociada con la mayor estratificacion durante los eventos de intrusion de agua subartica, y los eventos el “Blob” y El Nino entre 2015 y 2016. Los cambios en la productividad observados concuerdan con la variacion temporal del indice de la Oscilacion del Giro del Pacifico Norte. La variabilidad observada en ambas escalas contribuye a entender la variacion regional en niveles troficos superiores, dado que el fitoplancton es el principal componente de la cadena trofica marina. EnglishBetween 1997 and 2016, the Investigaciones Mexicanas de la Corriente de California (IMECOCAL, Mexican Investigations of the California Current) program conducted measurements of chlorophyll a and phytoplankton production off Baja California. Here, we summarize the main results obtained during the survey period. Long-term means indicated that high productivity occurred along the coastal zone where upwelling occurs, and in a semi-permanent cyclonic gyre off Punta Eugenia. At the seasonal scale, the variability of integrated primary production showed differences with respect to integrated chlorophyll a variability. Integrated chlorophyll a exhibited maximum values during the coastal upwelling season in spring and summer, while minimum values occurred during the inflow of tropical-subtropical waters south of Punta Eugenia in autumn and winter. In contrast, the highest values of integrated primary production occurred in spring and summer to the north of Punta Eugenia, whereas to the south of this location, the highest values occurred in winter and autumn. This seasonal variability was associated with phytoplankton size and maximum photosynthetic rates. At the interannual scale, low productivity was associated with increased stratification during the subarctic water intrusion events and the “Blob” and El Nino events in 2015–2016. Productivity time-series were in agreement with the seasonal variability of the north Pacific Gyre Oscillation index. Given that phytoplankton is the first level of the marine food web, this study contributes to the understanding of regional variations in higher trophic levels at the seasonal and interannual scales.

The southern Mexican Pacific Ocean presents seasonal changes related to the rainy season and Tehuano winds, which generate mesoscale processes affecting biological productivity and marine biodiversity. Size distributions of squid paralarvae collected in this region during the rainy season (July 2007 and May-June 2008) were analyzed in relation to regional oceanography. Samples were collected through oblique hauls, and CTD casts were used to determine the structure of the water column. Between surveyed periods, there were no significant changes in the water temperature at 10 m, but there were significant variations in the mixed layer depth (MLD). The number of taxa, community composition and total abundance of paralarvae were similar between periods. However, in July paralarvae ≤2.0 mm were distributed along the margins of cyclonic and anticyclonic eddies associated with high temperatures. In May-June, the MLD and high concentrations of chlorophyll a (Chl- a ) determined the presence of a group of oceanic paralarvae and another of coastal paralarvae, separated by an upwelling front. The percentage of recently spawned paralarvae (≤2.0) nearly doubled during this period as a result of increased coastal sampling and high concentrations of Chl- a , indicating a coupling of adult reproduction with regional productivity. In the absence of winds, the mesoscale oceanographic complexity generates gradients and a differential effect on the distribution, transport and survival of cephalopod paralarvae. Normal 0 21 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabla normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Calibri",sans-serif; mso-ansi-language:EN-US; mso-fareast-language:EN-US;} Normal 0 21 false false false EN-US X-NONE X-NONE

The aim of this work was to determine if the variation patterns in the abundance of dominant species of fish larvae in the transition zone off Bahia Sebastian Vizcaino, Mexico, could be used as indicators of interannual environmental variability, and how larval fish assemblages respond to this environmental variability during the period 1997–2013. With the 16 years of plankton data in the southern region of the California Current System, anomaly curves of larval abundance were calculated, from which the temporal abundance patterns of the dominant fish larvae of the mesopelagic, epipelagic and demersal environments were obtained. Classification and ordination analyses were carried out to obtain the larval fish assemblages as well as their relations with environmental variables (sea surface temperature, surface salinity, concentration of Chlorophyll-a and zooplanktonic volume) and climatic indexes (ONI, MEI, PDO and NPGO). Results showed a high positive correlation between the mesopelagic abundance with MEI and PDO indices, demonstrating their affinity with warm oceanic waters, while there were not statistically significant correlation between the climatic indexes and the epipelagic (Sardinops sagax and Engraulis mordax) or demersal species (Synodus lucioceps). The interannual variability of the abundance of three dominant mesopelagic species (Vinciguerria lucetia, Diogenichthys laternatus and Cyclothone signata) show that these species had a clearer response to environmental variability than epipelagic and demersal species. Trends in the abundance of mesopelagic species larvae and their high correlation values with the environmental variables used, demonstrate their potential as indicators of environmental change of the pelagic ecosystem in the transitional area off Bahia Sebastian Vizcaino.