Baja California Sur Research Articles

Can the Adoption of Desalination Technology Lead to Aquifer Preservation? A Case Study of a Sociotechnical Water System in Baja California Sur, Mexico

There is growing concern about the sustainability of groundwater supplies worldwide. In many regions, desalination—the conversion of saline water to freshwater—is viewed as a way to increase water supplies and reduce pressure on overdrawn aquifers. Using data from reports, articles, interviews, a survey, and a focus group, this paper examines if, and how, the adoption of desalination technology can lead to aquifer preservation in Baja California Sur (BCS), Mexico. The paper outlines existing institutional arrangements (i.e., laws, rules, norms, or organizations) surrounding desalination in BCS and concludes that there are currently no effective mechanisms to ensure aquifer preservation. Four mechanisms that could be implemented to improve groundwater management are identified, including: 1) integrated water-and land-use planning; 2) creation of an institute responsible for coordinated and consistent planning; 3) improved groundwater monitoring; and 4) implementation of water conservation measures prior to the adoption of desalination technology. This paper concludes that viewing water technologies, including desalination, as sociotechnical systems—i.e., a set of technological components that are embedded in complex social, political, and economic contexts—has the potential to create a more sustainable human–environment–technology relationship. By assessing desalination technology as a sociotechnical system, this study highlights the need to focus on institutional development and capacity building, especially within local water utilities and urban planning agencies.

An examination of coastal conservation by remote sensing in Baja California Sur, México

The state of Baja California Sur (BCS), Mexico, has a coastline of 2131 km with eight Protected Natural Areas (PNA) (33,075 km2) mainly located in the coastal zone. Here, we (1) review the current status of the diversity and distribution of coastal ecosystems in BCS, (2) assess the composition and coverage of these ecosystems in PNAs, and (3) identify coastal ecosystems of special interest for conservation. The combination of spatial analysis techniques was carried out using LandSat TM images and GIS processing, considering ecoregions and ecosystems in the coastal zone, as well as through the application of an ecosystem diversity index. In the BCS coastal zone, 11 ecosystems were identified: scrub, coastal water body, riparian, bare soil, halophyte, beach, salt flat, mangrove, salt marsh, coral reef, and seagrass. The ecosystem diversity in BCS results from the coastal features that differentiate the Pacific and the Gulf coasts. PNAs include 17 % of coastal ecosystems. Bahia Magdalena (Pacific) and Bahia Concepcion (Gulf of California), which are key for conservation (including mangroves and seagrasses), should be considered either for classification as PNAs or for inclusion in coastal management programs. The combination of remote sensing and GIS with biogeographic and ecosystemic approaches in our study enabled to determine ecosystem diversity and set coastal conservation priorities in Baja California Sur, Mexico. Specifically, coastal ecosystems that are not currently included within PNAs and which should be considered as conservation priorities were identified.

Isolation, characterization, and antibiotic resistance of Vibrio spp. in sea turtles from Northwestern Mexico.

The aerobic oral and cloacal bacterial microbiota and their antimicrobial resistance were characterized for 64 apparently healthy sea turtles captured at their foraging grounds in Ojo de Liebre Lagoon (OLL), Baja California Sur (BCS), Mexico (Pacific Ocean) and the lagoon system of Navachiste (LSN) and Marine Area of Influence (MAI), Guasave, Sinaloa (Gulf of California). A total of 34 black turtles (Chelonia mydas agassizii) were sampled in OLL and eight black turtles and 22 olive ridley turtles (Lepidochelys olivacea) were sampled in LSN and MAI, respectively from January to December 2012. We isolated 13 different species of Gram-negative bacteria. The most frequently isolated bacteria were Vibrio alginolyticus in 39/64 (60%), V. parahaemolyticus in 17/64 (26%), and V. cholerae in 6/64 (9%). However, V. cholerae was isolated only from turtles captured from the Gulf of California (MAI). Among V. parahaemolyticus strains, six O serogroups and eight serovars were identified from which 5/17 (29.4%) belonged to the pathogenic strains (tdh+ gene) and 2/17 (11.7%) had the pandemic clone (tdh+ and toxRS/new+). Among V. cholerae strains, all were identified as non-O1/non-O139, and in 4/6 (66%) the accessory cholera enterotoxin gene (ace) was identified but without virulence gene zot, ctxA, and ctxB. Of the isolated V. parahaemolyticus, V. cholerae, and V. alginolyticus strains, 94.1, 33.4, and 100% demonstrated resistance to at least one commonly prescribed antibiotic (primarily to ampicillin), respectively. In conclusion, the presence of several potential (toxigenic) human pathogens in sea turtles may represent transmission of environmental microbes and a high-risk of food-borne disease. Therefore, based on the fact that it is illegal and unhealthy, we discourage the consumption of sea turtle meat or eggs in northwestern Mexico.

Imaging conservation: Sea turtle murals and their effect on community pro-environmental attitudes in Baja California Sur, Mexico

Public art in Mexico has historically served as a platform for protest and social commentary. The purpose of this action research was to document sea turtle murals throughout Baja California Sur (B.C.S.), Mexico and to better understand the potential relevance of public art as an impetus for fostering pro-environmental attitudes, and the extent to which murals are a useful tool in efforts to protect the marine environment and the recovery of endangered species. Through qualitative research, we conducted 333 surveys and interviews with both adult and student participants in nine B.C.S. communities. Through descriptive narratives of participant responses, and Type I tabulations, we found evidence of outcomes that sea turtle murals may have in relation to respondent environmental attitudes about support for marine protections and the recovery of endangered species of sea turtles. Unexpected results from semi-structured interviews with respondents pointed weakly to the potential for murals in helping to shape pro-environmental behaviors towards the treatment and recovery of endangered sea turtles. The results of this action research may provide useful insights for improving management practices during future efforts to protect and restore marine environments and endangered species. That is, public participation in strategically placed community accessible art, may prove to be a valuable and innovative component of a broader suite of outreach and education initiatives used for bolstering community responsibility and empowerment for conservation of the marine environment.

Marine diet and tobacco exposure affects mercury concentrations in pregnant women (I) from Baja California Sur, Mexico

Seafood provides essential polyunsaturated fatty acids (PUFA) and other nutrients to pregnant women and their fetus(es) while a diet rich in finfish can be a major pathway of monomethyl mercury (MeHg+) exposure. We measured total mercury concentration ([THg]) in hair samples provided by 75 women in Baja California Sur (BCS) to assess its relationship with age, parity, tobacco smoke exposure, and diet based on survey methodologies. Generalized linear models (GLM) were used to explain the possible association of the different variables with [THg] in hair. Median [THg] in hair was 1.52 μg g−1, ranging from 0.12 to 24.19 μg g−1 and varied significantly by segment. Approximately 72% (54/75) of those evaluated exceed 1 μg g−1 [THg] and 8% (6/75) exceed 5 μg g−1 [THg] in hair. Although frequency of fish consumption contributed significantly to explaining hair [THg], fish consumption only explained 43% of [THg] in a GLM incorporating tobacco exposure and body mass index. This study establishes possible relationships among multiple potential sources of exposure and other factors related to [THg] in hair of women in the prenatal period. A more detailed examination of other sources of exposure and factors contributing to [THg] is warranted.

The artisanal elasmobranch fishery of the Pacific coast of Baja California Sur, Mexico, management implications

Artisanal fisheries in Mexico account for approximately 40% of the total national catch. In 2009, Baja California Sur (BCS) had the second largest catch of elasmobranchs on the Mexican Pacific coast. This paper characterizes and describes the artisanal elasmobranch fishery of Pacific coast of BCS from 2000 to 2010. Sixty artisanal camps were documented, of which 45 targeted elasmobranchs, using primarily gillnets and longlines. We identified 52 elasmobranch species. Gillnetting accounted for 73.5% of the fishing effort and most frequently captured Rhinobatos productus, Mustelus henlei and Myliobatis californica . Longline fishing accounted for 26.5% of effort, most frequently capturing Prionace glauca and Isurus oxyrinchus . The prevalence of juveniles of several species (e.g., Cephaloscyllium ventriosum, Galeorhinus galeus, Isurus oxyrinchus , and Myliobatis californica ) within landings suggests that fishing effort may be opportunistically directed at breeding or nursery areas. Despite the dominance of species with wide distributions, we observed a significant biogeographic pattern in the abundance of some species relative to Bahia Magdalena. Results of the present study will be useful to detect changes in the structure of commercially exploited elasmobranch populations, and to provide useful indications for management purposes.

Feeding habits of Mustelus henlei on the western coast of Baja California Sur, México

Palabras clave: Contenido estomacal, superposicion de dieta, especialista, Punta Lobos, Baja California Sur, Mexico Abstract.- The Brown smooth-hound Mustelus henlei is part of an important commercial fishery on the western coast of Baja California Sur (BCS), Mexico. However, very few studies have been performed on the feeding and reproduction biology of these sharks in Mexico. Our study is the first work focusing on this species on the western shelf (14 m to 250 m in depth) of B.C.S. We identified a total of 24 types of prey contents in the stomachs of M. henlei: 15 crustaceans, 6 fish, and 3 cephalopods. According to the index of relative importance (IRI) the main prey items for M. henlei was the pelagic red crab Pleuroncodes planipes (81.4%), followed by unidentified organic material (UOM) (15.7%), the mackerel Scomber japonicus (0.94%), and fish remains (0.84%). Conducting a prey analysis considering sex of M. henlei, P. planipes was the most important prey in both females and males, followed by UOM, and S. japonicus. Sharks found in deeper areas (120-150 m) and those caught on board the exploration ship BIP XII had a similar dietary composition to those found in the shallow waters of Punta Lobos (14-40 m) where for both regions, the dominant prey items were the pelagic red crab and UOM. According to Levin's index, M. henlei may be a specialist feeder in this area. A diet overlap according to sex, area, and size was observed. The SIMPER analysis showed a low similarity in diet in relation to sex, size, and area. According to the ANOSIM test there were no significant differences. Knowing that M. henlei shows a specialist behavior could help research studies not only for species conservation but also for its habitat and the organisms that inhabit it, which are both of vital importance for this shark.

Ecosystem models for management advice: An analysis of recreational and commercial fisheries policies in Baja California Sur, Mexico

Recreational fishing is a vital component of the tourism economy in Baja California Sur (BCS), Mexico, although several artisanal and industrial fisheries continue to operate in the region. The commercial long-liner fleet in particular is widely held to be responsible both for diminishing shark populations and declines in billfish through bycatch. Using available fisheries and ecosystem data, we develop an Ecopath with Ecosim (EwE) model to represent current ecosystem and fishing dynamics in BCS and explore the ecological and economic effects of specific fisheries policy measures. Results suggest that currently mandated bycatch limits for the longlining fleet will have little effect on marlin abundance in the area. In an overfished ecosystem, decreasing fishing effort can result in higher overall catches through population rebuilding. While perhaps ecologically justified, increases in the abundance of sharks, a top predator, can have negative effects on other valued species in the ecosystem. The effects of these trophic dynamics must not be overlooked, as they can negate or even reverse desired outcomes from fisheries management.

To Poach or Not to Poach an Endangered Species: Elucidating the Economic and Social Drivers Behind Illegal Sea Turtle Hunting in Baja California Sur, Mexico

Despite complete legal protection, improvements in infrastructure, and market conditions that provide easier access to other protein sources, illegal poaching of sea turtles for consumption in Baja California Sur (BCS), Mexico remains a major threat to their recovery. Few studies have focused on understanding the economic and social drivers behind this activity, which is fundamental to determining best practices for discouraging it. From June 2007 to April 2008 we conducted eight in-depth, semi-structured interviews with sea turtle poachers at five coastal communities in BCS to determine the drivers influencing them. The most prevalent reasons for illegal poaching were direct economic benefits, lack of law enforcement and ease of escape from or bribery of authorities, and strong family tradition. Our results suggest that to reduce illegal poaching it will be necessary to better enforce existing environmental laws, reduce social acceptance of sea turtle hunting throughout the region, educate fishers on the ecological importance of sea turtles, and show fishers direct economic benefits from non-consumptive use of sea turtles, such as ecotourism.

The Emergence of Associational Life in México’s Wild West: Pioneering Civic Participation, Sea Turtle Conservation, and Environmental Awareness in Baja California Sur

This research explores the contributions of the sea turtle conservation movement in Baja California Sur (B.C.S.), Mexico, to the growth of associational life in the state. Mexico has historically been known as a country with a traditionally weak associational life. Yet, the activities of sea turtle NGOs and community groups presented a unique case study to better understand the social, political, and strategic factors that have contributed to voluntary civic engagement and the environmental successes of the movement. Through 799 interviews and surveys with public stakeholders, this research utilized Sabet’s (Democratization 2:410–432, 2008) focus on political opportunity, efforts to reform informal rules, and supportive social networks, as an explanatory framework to help describe the emergence of associational life. We found that the sea turtle conservation movement in B.C.S. has become accessible to a diversity of interests and individuals. We found unexpected results in the extent of federal environmental agency complaisance in regard to the involvement of NGOs in conservation programs and environmental policy decisions that have traditionally been the sole domain of the Government of Mexico.

The distribution of an invasive plant in a fragile ecosystem: the rubber vine (Cryptostegia grandiflora) in oases of the Baja California peninsula

The rubber vine (Cryptostegia grandiflora) is an aggressive, invasive weed species with a high spreading potential that has caused great ecological impacts and economic costs to the areas in which it has been introduced. In Mexico, there is little information on the invasion of this species. In Baja California Sur (BCS), the first record of the species is documented from 1935 in one oasis. Despite the ecological problems that this invasive species may cause in the oases of BCS, little was known about its distribution and status. The aim of this work was to document the presence of the rubber vine in 57 oases in Baja California Sur during 2006–2008. The rubber vine was present in 22 (39%) of the sampled oases. The distribution pattern strongly suggests that the rubber vine had been introduced by the local population and then spread in the oasis and into the vicinity of streams and canyons. Vertebrate and invertebrate endemic oasis-dependent species may be at risk because the rubber vine can become a dominant species in oases and because reptiles and birds may not use the plant and instead avoid the areas where it grows. This is risky in fragile ecosystems immersed in a desert. Education and eradication of rubber vines from oases should be urgently done.

Efectos económicos y sociales del TLCAN en la pesca del atún en Baja California Sur, México

No obstante que el sistema internacional de comercio se desarrolló sin tomar en consideración un marco de protección ambiental, se han hecho esfuerzos para hacer coincidir objetivos ambientales y políticos. En México, Baja California Sur (BCS) es el estado más árido con la línea costera más extensa en el país (2,200 km). El objetivo de este trabajo fue identificar los impactos económicos y sociales que el Tratado de Libre Comercio para América del Norte (TLCAN) ha provocado en la pesca del atún aleta amarilla (thunnus albacares), en BCS. Analizamos la información más relevante para la pesca del atún en el periodo 1980-2000: crecimiento de la producción, incremento en la cantidad y valor de los productos exportados, número y antigüedad de las embarcaciones dedicadas a la captura del atún, incremento de la inversión en el sector pesquero dedicado al atún y la generación de empleos. Encontramos que en el corto y mediano plazo, el TLCAN no ha tenido efectos significativos sobre las variables económicas y sociales estudiadas para la pesca del atún. No es de esperar que la industria pesquera que participa en la captura del atún experimente cambios, positivos o negativos, en el punto de integración actual en que se encuentra el TLCAN.

Evaluación de la congruencia entre economía y gobierno en torno al desarrollo regional de Baja California Sur, México

En el estado mexicano de Baja California Sur (BCS) se está llevando a cabo una discusión sobre la mejor estrategia de desarrollo económico regional, que le permita al estado aprovechar sus potencialidades y desarrollar algunas nuevas con una estrategia definida en el corto y en el largo plazos. En la discusión de esta estrategia, el concepto de sector clave está jugando un papel fundamental, aunque éste se ha entendido de diversas maneras. El hecho de conceptualizar de manera diferente el término de sector clave no contribuye en la tarea de diseñar una estrategia de desarrollo que sea consistente en el corto y en el largo plazos, sobre todo cuando se busca que estos sectores sean los ejes de la misma. En este trabajo presentamos un análisis relacionado con la identificación de sectores clave para el estado de BCS, mediante el auxilio de varias metodologías que tienen como base el sistema de insumo-producto (MIP).

Anticoagulant screening of marine algae from Mexico, and partial characterization of the active sulfated polysaccharide from Eisenia arborea.

The in vitro anticoagulant activity of 41 water extracts of various seaweeds from Baja CaliforniaSur, Mexico was evaluated. In this study, nine extracts exhibited anticoagulant activity in the prothrombin time assay and 29 extracts were positive in the activated partial thromboplastin time assay. The water extract obtained at 25 °C from the brown seaweed Eisenia arborea was the most active in both assays, increasing the normal blood clotting-time over 300 s at 100 mg mL-1. The fractionation of this extract by anion exchangechromatography yielded 3 fractions. Fraction 2 eluted with 1.0 M sodium chloride increased the clotting-time over 300 s in the activated partial-thromboplastin time assay at 5 mg mL-1, being more active than sodium heparin. Chemical and spectroscopic analysis of fraction 2 showed it to be a sulfated heterofucan composed of 56.2 % ± 0.1% of total sugars and 45 % of sulfates.The neutral sugar constituents of the active heterofucan was determined to be 47.6 % fucose, 35.5 % xylose and 16.9 % rhamnose, with substitutions of sulfate groups at C-4 (axial), and minor substitutions at C-2 and-or C-3.

Sea turtle consumption and black market trade in Baja California Sur, Mexico

We examined sea turtle consumption and illegal trade in Baja California Sur (BCS) using data from (1) bimonthly surveys at beaches, fishing camps and dumpsites and (2) semi-struc- tured interviews with fishermen. From March 2006 to February 2008, we found the carcasses of 1014 sea turtles; the meat of 461 of these turtles (45.5%) had been consumed. The East Pacific green tur- tle Chelonia mydas was the most sought-after species (77% of total consumed turtles). Consumption is still the main cause of mortality for sea turtles and the greatest threat to them in BCS, affecting mostly juvenile-sized specimens. Sea turtle consumption occurred all year round with a lower num- ber recorded from November to February and an increase thereafter. From 151 interviews we iden- tified 3 areas where turtle meat is consumed but not sold, 4 areas with a local black market and 3 areas providing for a regional and/or international black market. Prices vary from 2-5 USD kg -1 (entire turtle sold on the beach) to 4-20 USD kg -1 (meat only). Consumption of sea turtle meat is partly related to cultural factors, as it is consumed more frequently during the Christian fasting period of Lent. While trade and consumption have decreased in recent years, there are still several places that supply sea turtle meat to local, regional, and sometimes even international markets. Authority involvement in sea turtle traffic and the lack of law enforcement need to be addressed to improve sea turtle conservation in the region. The use of both qualitative and quantitative data in the present study has helped to gain a better understanding of sea turtle consumption in BCS.

Renewable energy powered desalination in Baja California Sur, Mexico

Baja California Sur (BCS) is an arid sparsely populated coastal state in northwest Mexico. Population growth, agriculture and booming tourism have lead to severe overexploitation of underground aquifers and saline intrusion. This paper reviews the current water and energy situation in BCS. The state enjoys very high levels of solar radiation, typically above 5 kWh/m2/day, and the suitability of renewable energy powered desalination for BCS is discussed, including past efforts in BCS and present challenges for this technology.

A New Strain of Tomato chino La Paz virus Associated with a Leaf Curl Disease of Tomato in Baja California Sur, Mexico.

Since 2001, geminivirus-like disease symptoms have been observed in tomato plants on the Baja California Peninsula of Mexico. These diseases have been associated with large populations of Bemisia tabaci (Genn.) in commercial fields and have caused dramatic decreases in expected yields. Leaf samples from tomato plants displaying symptoms of stunting and severe upward leaf curling were collected in March 2002 in fields located near the city of La Paz, Baja California Sur (BCS). Total DNA was extracted and tested for the presence of geminiviral DNA using polymerase chain reaction (PCR) with begomovirus-specific degenerate primer pairs PALIv1978/PARIc494 and PALIc1978/PARIv494 (4). PCR products of the expected size (~1.16 and ~1.45 kb) were obtained, cloned into pGEM-T Easy (Promega, Madison, WI), and sequenced. Restriction fragment length polymorphism analysis of the PCR fragments was performed using EcoRI, HindIII, PstI, and XbaI. Restriction fragment patterns were the same for all amplicons and no evidence of mixed infection was obtained. In addition, experimental transmission by whiteflies and inoculations by biolistics consistently induced severe leaf epinasty and stunted growth on tomato seedlings. The complete (2,606 nt) DNA-A sequence of the infecting virus was determined (GenBank Accession No. AY339618) and compared with viral sequences available at GenBank-EMBL databases using BLASTN and the CLUSTAL program (MegAlign, DNASTAR, Madison, WI). The highest nucleotide identity was obtained with the recently described Tomato chino Baja California virus, ToChBCV (90.2%, GenBank Accession No. AY339619), isolated from tomato plantings in El Carrizal, BCS, 100 km from La Paz (3). The second and third best scores were obtained with Tomato severe leaf curl virus from Nicaragua (ToSLCV-NI, 79.6%, GenBank Accession No. AJ508784) and Guatemala (ToSLCV-GT94, 73.8%, GenBank Accession No. AF130415), respectively. Overall, sequence similarity with other New World begomoviruses was rather low (less than 70% identity). Careful analysis of differences between the La Paz isolate and its closest relative, ToChBCV from El Carrizal, revealed that they display different Ori-associated iterons (i.e., replication (Rep)-binding sites) having GGAGTA and GGGTCY core sequences, respectively (1). Moreover, sequence comparisons of the Rep-binding domain (aa 1-120) showed that these domains are only 71% identical. Current taxonomic criteria for begomoviruses establishes that a virus DNA-A sequence identity below 89% with its closest relative is indicative of a separate species (2). Since the La Paz and El Carrizal isolates share 90.2% nt identity, they should be considered strains of a same virus species, recently renamed Tomato chino La Paz virus, ToChLPV (2). Nevertheless, the remarkable differences in their putative replication specificity determinants suggest that ToChLPV and ToChLPV-[BCS] could be incompatible in replication, an interesting issue that should be experimentally addressed.

Flux of nutrients in the Gulf of California: Geostrophic approach

Continental margins exert a strong influence on global biogeochemical cycles; however there have been relatively few attempts to quantify either the magnitude or nature of temporal variability in material fluxes. At present here are no reports on nutrient fluxes at the mouth of the Gulf of California (GC) so further information is needed to provide estimated values from direct measurements. From 1995–1999 during five cruises covering all seasons, seawater samples were collected and measured the nutrient content from the surface to the bottom (some deeper than 2500 m) from a repeated hydrographic sections at the mouth of the GC. This chemical and physical database is unique because it covers an area with important biogeochemical signs, which has been detected as one of the highest in primary productivity of the world oceans. These sections are perpendicular to the coastlines of the Mexican states of Baja California Sur (BCS) and Sinaloa. In this section, the most dynamic area was the surface waters in February 1999 with strong geostrophic currents and temperatures of 20 ± 1.5 °C; salinity 35.091 ± 0.156; pH 8.16 ± 0.13; phosphate 0.85 ± 0.42 μM, nitrate + nitrite 2.35 ± 2.94 μM, and ammonia 2.00 ± 1.25 μM (average ± standard deviation). Geostrophic velocities were computed from high-resolution CTD sections across the entrance to the GC. During winter and spring, the outflow occurred near BCS and the inflow occurred either through the center of the section and/or along the Sinaloa coast. Both inflow and outflow cores were 45 km wide and extended deeper than 700 m. Summer and fall showed a complex pattern, alternating cores of inflow and outflow but with inflow along Sinaloa on all cruises. The maximum flow into the Gulf occurs during May in the center of the section while outflow was concentrated along BCS. Mascarenhas et al. [Mascarenhas, A., Castro, R., Collins, C.A., Durazo, R., 2004. Seasonal variation of geostrophic velocity and heat flux at the entrance to the Gulf of California, Mexico. Journal Geophysical Research, 2124.] calculated the section mean geostrophic velocity that was composed of two alternating cores of inflow and outflow. The two cores that were adjacent to either coast were broader and contained the highest inflow (0.40 m s − 1 ) and outflow (− 0.25 m s − 1 ) velocities, supporting the general idea of inflow along the Sinaloa and an outflow along BCS. The highest nutrient fluxes occur during El Niño conditions in November 1997 with outflows as high as 54.5 Tg yr − 1 for Phosphate, 43.0 Tg yr − 1 for Nitrate and 31.7 Tg yr − 1 for Ammonia, this values were at least three times higher than in February 1999.

Fusarium Wilt of Tomato Caused by Fusarium oxysporum f. sp. lycopersici Race 3 in Baja California Sur, Mexico.

Vascular wilting diseases have become one of the most serious diseases of tomato (Lycopersicon esculentum) throughout the Baja California Peninsula. Since the winter of 2004, a disease with symptoms characteristic of those caused by a Fusarium species has been observed in commercial fields near La Paz and Todos Santos in the state of Baja California Sur (BCS). Symptoms include typical one-sided wilting and dark brown vascular discoloration. Upper stem tissues and wilted seedlings were disinfested by immersion in a 1.0% aqueous solution of sodium hypochlorite for 2 min, rinsed in sterile water, and placed on Komada's medium (pH 6.8) at 22 ± 3°C. After 72 h, hyphal growth was recovered and subcultured on carnation leaf agar and potato dextrose agar and incubated at 25°C in 12-h light/dark cycles. Identification was based on colony morphology, conidial characteristics, and molecular techniques. White cottony mycelium, reddish coloration of the medium, ovoid two-celled macroconidia, and large macroconidia, all characteristic of F. oxysporum, were observed (2). Polymerase chain reaction and restriction fragment length polymorphisms with restriction enzymes EcoRI, RsaI, and HaeIII were used to characterize 24 isolates (sampled during January 2005) from La Paz (Fol-LaP) as formae speciales lycopersici and assigned to vegetative compatibility group 0030 (1). Confirmation of pathogenicity and race determination for the Fol-LaP isolates were as described previously (3). Mexican isolates of races 2 and 3 (one each) were included as positive controls. Conidial suspensions of 7 × 105 CFU/ml were used to inoculate differential tomato cvs. Bonny Best (Millington Co., universally susceptible), Tequila F1 (Vilmorin, race 1 resistant), Rio Grande (Harris Moran, race 1 and 2 resistant), and Sebring (Rogers, race 1, 2, and 3 resistant). Plants at the first true-leaf stage were inoculated by dipping their roots in the conidial suspension. Inoculated seedlings were transplanted into pots containing a sterile 5:1:1 mixture of sand/vermiculite/soil (v/v/v) and maintained in the greenhouse at 25 to 28°C under natural daylight. An equal number of plants of each cultivar dipped in water were used as controls. The experimental design was a completely randomized type with six replications (pots) containing four seedlings per pot. The test was done twice. The most susceptible plants inoculated by root-dipping developed typical symptoms of wilt, slight vein clearing on outer leaflets, stunting, dark brown vascular discoloration, and death. F. oxysporum was recovered from all symptomatic plants, whereas noninoculated tomato seedlings showed no symptoms. According to differential infection and symptomatology observed on infected cultivars, 62.5% of the isolated strains were identified as race 2, 25% as race 3, and 12.5% as an undetermined race isolated from Sebring. The presence of race 3 in BCS has important epidemiological implications since it has been reported on tomato in Sinaloa (4). The potential spread of the pathogen on introduced transplants represents a risk to tomato crops on the peninsula. To our knowledge, this is the first report of F. oxysporum f. sp. lycopersici race 3 in the state of BCS, Mexico.

Mathematical simulation of the diel O, S, and C biogeochemistry of a hypersaline microbial mat

The creation of a mathematical simulation model of photosynthetic microbial mats is important to our understanding of key biogeochemical cycles that may have altered the atmospheres and lithospheres of early Earth. A model is presented here as a tool to integrate empirical results from research on hypersaline mats from Baja California Sur (BCS), Mexico into a computational system that can be used to simulate biospheric inputs of trace gases to the atmosphere. The first version of our model, presented here, calculates fluxes and cycling of O 2, sulfide, and dissolved inorganic carbon (DIC) via abiotic components and via four major microbial guilds: cyanobacteria (CYA), sulfate reducing bacteria (SRB), purple sulfur bacteria (PSB) and colorless sulfur bacteria (CSB). We used generalized Monod-type equations that incorporate substrate and energy limits upon maximum rates of metabolic processes such as photosynthesis and sulfate reduction. We ran a simulation using temperature and irradiance inputs from data collected from a microbial mat in Guerrero Negro in BCS (Mexico). Model O 2, sulfide, and DIC concentration profiles and fluxes compared well with data collected in the field mats. There were some model-predicted features of biogeochemical cycling not observed in our actual measurements. For instance, large influxes and effluxes of DIC across the MBGC mat boundary may reveal previously unrecognized, but real, in situ limits on rates of biogeochemical processes. Some of the short-term variation in field-collected mat O 2 was not predicted by MBGC. This suggests a need both for more model sensitivity to small environmental fluctuations for the incorporation of a photorespiration function into the model.