The Relationship between Photosynthesis and Irradiance for Gulf of California Phytoplankton

During June 17-28, 1982, we carried on experiments to generate photosynthesis-irradiance curves for phytoplankton from five locations of the central and northern Gulf of California. Using natural sunlight, on board 14C incubations were done with samples collected from five different depths within the euphotic zone. In general there were great vertical changes of variables controlling primary productivity, even in cases where weak vertical TOC gradients indicated high instability and mixing of the euphotic zone. The assimilation number (PBm) had a two fold variation within the mixed layer. In general PBm decreased monotonically with depth due to phytoplankton conditioning to lower irradiances. Surface PBm values had a range of 8 to 15mg C. mg Chl a- 1. h-1. When a thermocline was present, PBm for the bottom of the euphotic zone was about 4 to 10% of that for surface waters. But, without a thermocline, P~ for the bottom of the euphotic zone was ~ 60% of that for surface waters, due to turbulence moving phytoplankton up and down the water column. Diatoms were abundant in three stations near Angel de la Guarda and Tiburon islands. For the station at the central gulf and the one at the very northern gulf, very few nano and microplankton were found with the inverted scope technique, but high chlorophyll concentrations and primary productivity indicated a high abundance of picoplankton. This difference in plankton size composition was not reflected in PBm values. Nutrient concentrations were high and did not limit PBm values. Our PBm values are higher than those reported for the gulf's winter phytoplankton; and they are about two times higher than those for winter phytoplankton of the oceanic region between San Diego and Acapulco. Our Gulf of California integrated primary productivity values had a range of 1.3 to 4.4gC. m-2. d-1

Phytoplankton size-fractionated chlorophyll-a off Baja California during winter, spring, and summer 2008

Spatial and temporal size-fractionated phytoplankton chlorophyll-a (Chl-a) variability as pico-nanoplankton (PN, 0.4- 8.0 µm) and nano-microplankton (NM, >8.0 µm) off Baja California is shown. Chl-a samples from the upper 200 m were obtained from nearshore, offshore, and intermediate locations during winter, spring, and summer 2008. PN-Chl-a contribution to phytoplankton biomass was ~4 times higher than NM fraction. Chl-a PN/NM ratio increased toward offshore, while total Chl-a (PN + NM) decreased. Seasonally, offshore phytoplankton cells abundance had a comparable contribution for both size-fractions, without an apparent change by the integrated water-column total Chl-a (60 mg m?2). Vertical Chl-a profiles were similar for winter and summer seasons. The highest Chl-a concentration and phytoplankton-cells abundance arose in spring, predominantly for NM at nearshore locations, reaching from 2.7-fold (nearshore: middle) to 4.2-fold (middle: offshore) ratios. Phytoplankton Chl-a increased from winter to spring (5.4 times), with maximum contribution of NM (6.6 times) at nearshore zones. Water-column integrated phytoplankton abundance was 5-fold higher in spring than winter, and 2-fold over summer. Using optical microscopy, dinoflagellate cells were the most abundant and variable phytoplankton recognizable group at intermediate zone. Smaller phytoplankton cells sustained approximately continuous biomass off Baja California. The spatial and temporal phytoplankton biomass variability was mainly influenced by an increase of larger cells as result of spring coastal upwelling events

Seasonal and interannual variability of satellite-derived chlorophyll pigment, surface height, and temperature off Baja California

Mean fields, seasonal cycles, and interannual variability are examined for fields of satellite-derived chlorophyll pigment concentrations (CHL), sea surface height (SSH), and sea surface temperature (SST) during 1997–2002. The analyses help to identify three dynamic regions: an upwelling zone next to the coast, the Ensenada Front in the north, and regions of repeated meanders and/or eddy variability west and southwest of Point Eugenia. High values of CHL are found in the upwelling zone, diminishing offshore. The exception is the area north of 31°N (the Ensenada Front), where higher CHL are found about 150 km offshore. South of 31°N, the long-term mean dynamic topography decreases next to the coast, creating isopleths of height parallel to the coastline, consistent with southward geostrophic flow. North of 31°N the mean flow is toward the east, consistent with the presence of the Ensenada Front. The mean SST reveals a more north-south gradient, reflecting latitudinal differences in surface heating due to solar radiation. Harmonic analyses and EOFs reveal the seasonal and interannual patterns, including the region of repeated eddy activity to the west and southwest of Point Eugenia. A maximum CHL occurs in spring in most of the inshore regions, reflecting the growth of phytoplankton in response to the seasonal maximum in upwelling-favorable winds. SST and SSH anomalies are negative in the coastal upwelling zone in spring, also consistent with a response to the seasonal maximum in upwelling. When the seasonal cycle is removed, the strongest signal in the EOF time series is the response to the strong 1997– 1998 El Niño, with a weaker signal representing La Niña (1998–1999) conditions. El Niño conditions consist of low chlorophyll, high SSH, and high SST, with opposite conditions during La Niña

Carbono orgánico nuevo frente a la Península de Baja California: series de tiempo y climatología

Time series of new phytoplankton production (Pnew) off Baja California from 1970 to 2008 computed using statistical models of temperature-nitrate relationship in ten groups of coastal and oceanic stations (Lines 90, 107, 120, 137 and 157) of the CalCOFI-IMECOCAL network, are presented. Pnew was calculated from the -ratio and total primary production (Ptotal). Spatially, the most productive areas of the region were Lines 90, 120 and 157. Pnew of lines 107 and 137 had relatively low values. These two lines marked the border between the northern and southern areas of the studied region. Seasonally, Pnew was high in the spring-summer transition, decreased in summer and autumn, and increased in winter. Pnew was related to coastal upwelling index, and we conclude that for an index of less than 200 m3/s/100 m, Pnew increases and its maximum occurs in phase with the coastal upwelling index. For an upwelling index greater than200 m3/s/100 m Pnew decreases and both series are out of phase.Se presenta la serie de tiempo de la producción fitoplanctónica nueva (Pnueva) frente a la Península de Baja California de 1970 a 2008, calculada por modelos estadísticos de la relación temperatura-nitrato en diez grupos de estaciones costeras y oceánicas de las Líneas 90, 107, 120, 137 y 157 de la red CalCOFI-IMECOCAL. La Pnueva se calculó a partir de la razón- y la producción primaria total (Ptotal). Espacialmente las zonas más productivas fueron las oceánicas de las Líneas 90, 120 y 157. La Pnueva en las Líneas 107 y 137 presentó valores bajos y se comportó como un parte-aguas entre las regiones norte y sur. Estacionalmente la Pnueva fue alta en la transición primavera-verano; disminuyó en el verano y el otoño, con aumento en invierno. La Pnueva se relacionó con el índice de surgencias costeras y se concluye que para un índice de surgencias costeras menor a 200 m3/s/100 m, la Pnueva aumenta y el máximo se produce en el mismo período que las surgencias costeras. Para un índice superior a 200 m3/s/100 m la Pnueva disminuye y ambas series se desfasan temporalmente

Frequency and risk factors of intestinal parasites in pet dogs from Mexicali, Mexico

Parasitic intestinal infections in dogs represent a problem for human health, because a wide variety of these parasites have zoonotic potential. Therefore, proximity to pets puts us at risk. The objective of this study was to determine the frequency and risk factors (age, sex, size, breed, presence of ectoparasites and gastrointestinal disorders) of intestinal parasites in the feces of dogs attending a Veterinary Hospital in the City of Mexicali, Baja California, Mexico. A total of 148 fecal samples were collected from canine patients and analyzed for parasite identification and parasite load. A 12.2% (18/148) of the samples were positive to parasitic intestinal infections. The frequency of specific infections was an 8.1% of Cryptosporidium sp., followed by a 2.7% of Cystoisospora sp., and 1.4% of Toxascaris leonina. A statistical significance was identified between the presence of intestinal parasites and mongrel breed. The predominance of protozoa shows the importance of diagnosis prior to treatment with anthelminthic drugs, since preventive antiparasitic protocols are commonly used, although these particular parasites are out of the spectrum of those drugs. Cryptosporidium spp. have zoonotic potential, particularly in immunocompromised patients, and there are few or no treatment options

Effects of mesoscale processes on phytoplankton chlorophyll off Baja California

Using satellite sea surface height (SSH) and chlorophyll (CHL), the year 2000 is analyzed to characterize the effects of mesoscale circulation patterns on phytoplankton spatial variability in the California Current (CC) off Baja California. Satellite data are combined with and compared to in situ field measurements (chlorophyll-a and hydrographic variables) along vertical alongshore sections located similar to 130 km offshore between similar to 24.5 degrees -33 degrees N. Monthly average maps of SSH and surface geostrophic velocities depict the characteristics of mesoscale meanders and eddies, which correspond well with the subsurface hydrographic and velocity fields. Satellite-derived pigment (CHL) represent in situ fields in the upper 0-20 m (overall r = 0.53; p < 0.05), but their representation of peak values in Deep Chlorophyll Maxima (DCM) at similar to 50 m depth are inaccurate. DCM are traced in all three seasons (January-July), descending from near the surface (north of 31 degrees N) to 50 m over a large extent of the transect to the south, approximately following the 24.7-25.1 isopycnals as they and the isotherms deepen to the south. In January, phytoplankton chlorophyll concentrations in the DCM are relatively uniform, originating during upwelling events that occur farther north, then following the equatorward flow of the CC. During April and July, the discrete maxima in the DCM occur at the centers of cyclonic meanders and the chlorophyll concentrations inside these maxima are enhanced as a result of local coastal upwelling off Baja California. Phytoplankton blooms created by coastal upwelling spread offshore and subduct along the 24.7-25.1 isopycnals, creating the DCM along the inner part of the meandering jet.KEYWORDS: Current system, Satellite, Pigment, State, Temperature, El Nino, Salinity, Evolution, Interannual variability, Coastal transition zon

Phytoplankton absorption, photosynthetic parameters, and primary production off Baja California: summer and autumn

Abstract To estimate ocean primary production at large space and time scales, it is necessary to use models combined with ocean-color satellite data. Detailed estimates of primary production are typically done at only a few representative stations. To get survey-scale estimates of primary production, one must introduce routinely measured Chlorophyll-a (Chl-a) into models. For best precision, models should be based on accurate parameterizations developed from optical and photosynthesis data collected in the region of interest. To develop regional model parameterizations 14 Cbicarbonate was used to estimate in situ primary production and photosynthetic parameters ða à ; P à m , and E k ) derived from photosynthesis-irradiance (P-E) experiments from IMECOCAL cruises to the southern California Current during July and October 1998. The P-E experiments were done for samples collected from the 50% surface light depth for which we also determined particle and phytoplankton absorption coefficients (a p , a f , and a à f Þ. Physical data collected during both surveys indicated that the 1997-1998 El Nin˜o was abating during the summer of 1998, with a subsequent transition to the typical California Current circulation and coastal upwelling conditions. Phytoplankton chl-a and in situ primary production were elevated at coastal stations for both surveys, with the highest values during summer. Phytoplankton specific absorption coefficients in the blue peak ða à f (440) ) ranged from 0.02 to 0.11 m 2 (mg Chl-a) À1 with largest values in offshore surface waters. In general a à f was lower at depth compared to the surface. P-E samples were collected at the 50% light level that was usually in the surface mixed layer. Using a à and spectral absorption, we estimated maximum photosynthetic quantum yields (f max ; mol C/mol quanta). f max values were lowest in offshore surface waters, with a total range of 0.01-0.07. Mean values of f max for July and October were 0.011 and 0.022, respectively. In July P à m was approximately double and a à was about 1.4 times the values for October. Since the P-E samples were generally within the upper mixed layer, these tendencies in the photosynthetic parameters are attributed to deeper mixing of this layer during October when the mean mixed layer for the photosynthesis stations was 35 m compared to a mean of 10 m in July. Application of a semi-analytical model using mean values of P-E parameters determined at the 50% light depth provided good agreement with 14 C in situ estimates at the discrete 50% light depth and for the water-column integrated primary production.

Ordenamiento Ecológico Marino en el Pacífico Norte mexicano: propuesta metodológica

The dynamic oceanic and coastal regionalization of the Mexican North Pacific in front of the Baja California Peninsula was proposed based on a temperature and new primary production model (Pnew). Pnew was calculated based on temperature AVHRR images; SeaWiFS chlorophyll and PAR sensor and total phytoplankton production (PPz) and the reason for each depthfz multiplied. Monthly temperature maps and Pnew were done for different depths: 0, 10, 30, 50, 75 and 100 m. This is the first marine regionalization using the concept of territorial regionalization. The results show the oceanographic dynamic in front of the Baja California Peninsula; this varied from the coast to the ocean in a latitudinal manner. For the regionalization of the Mexican North Pacific, nine Environmental Management Units (EMU) are being proposed: three oceanic and six coastal. The oceanic EMU VIII and the neighboring coastal areas IV and V are considered transition zones between the northern (subarctic waters) and the southern (tropical waters) conditions. In particular, the region of Isla Navidad stands out as the division between the cold northern waters and the warm waters to the south. In the spring, the effect of the coastal upwellings of the EMUs I and II is visible from the surface up to 100 m, with eutrophic zones in the coastal EMUs IV and V at 30-50m. In the fall, the area of study is oligotrophic.Se propone una regionalización oceánica y costera dinámica del Pacífico Norte mexicano frente a la Península de Baja California a partir de un modelo de temperatura y producción primaria nueva (Pnueva). La Pnueva se calculó con base en imágenes de temperatura del AVHRR; clorofila y PAR del sensor SaeWiFS y se multiplicó por la producción fitoplanctónica total (PPZ) y la razón-fz para cada profundidad. Se confeccionaron mapas mensuales de temperatura y Pnueva para profundidades de 0, 10, 30, 50, 75 y 100 m. Esta es la primera regionalización marina con el concepto de regionalización territorial. Los resultados muestran la dinámica oceanográfica frente a la Península de Baja California; ésta varió de lacosta al océano y de forma latitudinal. Para la regionalización del Pacífico Norte mexicano, se propone nueve Unidades de Gestión Ambiental (UGA): tres oceánicas y seis costeras. La UGA oceánica VIII y las vecinas costeras IV y V son consideradas zona de transición entre las condiciones norteñas (agua subártica) y las sureñas (agua subtropical). En particular, la región de Isla Navidad se destaca como divisoria entre el agua fría al norte y cálida al sur. En primavera, el efecto de las surgencias costeras de las UGAs I y II se distingue desde la superficie hasta 100 m, con zonas eutróficas en las UGAS costeras IV y V en 30-50 m. En otoño el área de estudio es oligotrófica

Detección molecular de coronavirus bovino asociado al complejo respiratorio bovino en ganado de engorda del valle de Mexicali, Baja California, México

The bovine respiratory complex (BRC) is the leading cause of disease and death in beef cattle worldwide. It is a multifactorial infectious syndrome caused by different viruses and bacteria that reduce the productive efficiency and cause economic losses. In Mexico, BRC has been reported in all regions where cattle are fattened; however, these reports lack information on the presence of bovine respiratory coronavirus (BCV). This makes it necessary to have reliable and accurate diagnostic tools for detecting the presence of BCV in beef cattle fattened in Mexico, in order to propose appropriate sanitary measures for their clinical management. In this work, a real-time-PCR molecular diagnostic platform (rt-PCR) was developed to amplify a fragment of the BCV S protein in nasal exudate samples. When applying the rt-PCR platform for BCV in seemingly healthy beef cattle with signs of respiratory disease associated to BRC, 19/50 (38 %) were found to be positive, confirming the presence of this virus in the cattle of the region. The results of this work constitute the first report on the presence of the BCV associated to the BRC in the cattle region of northwestern Mexico and establish the bases for future research about the role that this virus plays in the presentation of the pathology of the BRC in beef cattle exploitation systems in this region and across the country.El complejo respiratorio bovino (CRB) es la principal causa de enfermedad y muerte en el ganado de engorda en todo el mundo. Es un síndrome infeccioso multifactorial provocado por distintos virus y bacterias que disminuyen la eficiencia productiva y ocasionan pérdidas económicas. En México, el CRB se ha reportado en todas las regiones donde se engorda ganado; sin embargo, esos reportes carecen de información sobre la presencia del coronavirus respiratorio bovino (CVB), haciendo necesario contar con herramientas de diagnóstico confiables y precisas para detectar la presencia de CVB en el ganado que se engorda en México, para proponer las medidas sanitarias apropiadas para su manejo clínico. En este trabajo, se desarrolló una plataforma de diagnóstico molecular de PCR en tiempo real (rt-PCR) que amplifica un fragmento de la proteína S del CVB en muestras de exudado nasal. Al aplicar la plataforma rt-PCR para CVB en bovinos de engorda en aparente estado de salud y con signos de enfermedad respiratoria asociados a CRB se encontró que 19/50 (38 %) resultaron positivos, confirmando la presencia de ese virus en el ganado de la región. Los resultados de este trabajo significan el primer reporte sobre la presencia del CVB asociado al CRB en la región ganadera del noroeste de México y sienta las bases para futuras investigaciones sobre papel que juega este virus en la presentación de la patología del CRB en los sistemas de explotación de bovinos de engorda en nuestra región y el país