Central Pacific Coast Of Mexico Research Articles

Characterization, variability and long‐term trends on local climate in a Mexican tropical dry forest

AbstractBased on 40 years of meteorological data, we characterized and analysed long‐term climatic trends in the Chamela‐Cuixmala Biosphere Reserve on the Pacific coast of central Mexico. The region is still covered by a large proportion of well‐preserved tropical dry forest, characterized by a short period of rain and a dry season of around 8 months. We found a sustained temperature increase which is likely driven by global climate change. An increasing trend in rainfall was also found, but the trend was detected only during the wet season. Correspondingly, an increase in runoff during the rainfall season was also detected; this seems to be linked with an increasing number of intense rainfall events, rather than an increase in the total number of rainy days. El Niño years are likely to present below average precipitation during the wet season and above average precipitation during the dry season. The opposite is expected during La Niña years, when tropical cyclones are likely to come closer to the coast and cause intense rainfall events during the hurricane season. As many of the studied variables are likely to change under climate change scenarios, our results highlight the need to understand the expected impacts of global climate change on tropical dry forests. In particular, it is necessary to monitor changes in water availability to anticipate its consequences for the forest and the human communities that depend on it.

Underwater vessel noise in a commercial and tourist bay complex in the Mexican Central Pacific

Noise generated by ship traffic is increasing around the world. Hence, there is need to effectively evaluate anthropogenic noise levels in marine habitats. In this study, the noise contribution of ships in the Santiago–Manzanillo bay complex, on the Pacific coast of central Mexico, was assessed. The semienclosed bay complex is one of the most important commercial ports in Mexico, and it is an area with high biological richness and tourism demand, including demand by the informal humpback whale watching industry. Bottom-fixed recording systems were deployed at the entrance to the bay, near the commercial port (Manzanillo Bay), and within the tourist area (Santiago Bay). Monthly acoustic records were obtained from September 2015 to August 2016. Boat categories confirmed by visual sightings were associated with their acoustic signals. According to the diagnostic frequency range, vessel noise was classified into noise coming from large ships (50–220 Hz) or from small vessels (290–500 Hz). Large ships were always detected at both stations, while, as expected, small vessels were more common in tourist areas. Vessel noise in the entire area ranged from 130 to 170 dB (RMS re 1 μPa) and was present up to a median of 81.8% of the time throughout the year, with higher prevalence from 1200 to 1600 hours. Marine traffic activities were constant in the area, but frequency content and sound pressure levels were not equally distributed across the bay. Therefore, it is important to consider the possible differential impacts on marine fauna inhabiting the area.

Coastal response to the passage of tropical cyclone Juliette on the Central Pacific Coast of Mexico

In situ coastal oceanographic and meteorological data were collected on the Mexican Tropical Pacific coast near Barra de Navidad, Jalisco, Mexico during September 2001 from before and after the passing of Hurricane Juliette. When the leading and trailing edges of the hurricane passed through the study area, wind speeds reached 15 m s-1 and caused a significant deepening of the thermocline, mixing of the upper 40 m of the water column, and a rise in sea level of almost 50 cm at the coast, with effects lasting for about 5 days. A decrease in temperature and an increase in salinity occurred in the upper 20 m, with the opposite occurring below 20 m. Although analyses of open ocean responses to hurricanes are widely available from satellite data, in situ coastal water-column and sea-level data are difficult to acquire, yet crucial to inform coastal flooding models and risk assessment studies. This short data set provides a rare opportunity to explore in situ hurricane effects on this understudied coast.

Phylogenetic placement of enigmatic Astianthus (Bignoniaceae) based on molecular data, wood and bark anatomy

Background: Astianthus is a monospecific arborescent genus of Bignoniaceae that occur in the Pacific Coast of central Mexico and northern Central America, where it grows in dense populations along riversides. Its phylogenetic placement has remained controversial since Astianthus has unusual morphological characters such as a four-loculed ovary, and simple, pulvinate, verticillate leaves.
 Methods: Here we used three plastid markers ndh F, rbc L, and trn L-F, wood, and bark anatomical data to investigate the phylogenetic placement of Astianthus and assign it to one of Bignoniaceae’s main clades.
 Results: Our molecular phylogenetic analyses indicated that Astianthus belongs in tribe Tecomeae s.s. , where other charismatic Neotropical Bignoniaceae genera such as Campsis and Tecoma are currently placed. Wood and bark anatomy support this placement, as Astianthus reunites a unique combination of features only known from members of Tecomeae s.s. , such as storied axial parenchyma, the co-occurrence of homo- and heterocellular rays, septate fibers, and scattered phloem fibers in the bark.
 Conclusions: The placement of Astianthus within Tecomeae s.s. provides further support to previous proposals for the Neotropical origin of this Pantropical tribe.

Contrasting effects of the El Niño 2015–16 event on coral reefs from the central pacific coast of Mexico

AbstractCoral reefs are highly diverse and productive ecosystems, and certain oceanographic processes, such as El Niño, have resulted in severe coral bleaching and mortality of reef‐building corals and to the global decline of the area covered by coral reefs. Here, we report the response of corals and both green and red filamentous and coralline algae from the central Mexican Pacific coast to the 2015–16 El Niño event. Sea surface temperature (SST) was recorded in the area between june 2012 and December 2018. Additionally, SST, DHW and the Oceanic El Niño Index (ONI) provided by NOAA for the El Niño 3 region during the same period were considered. Relative cover (%) of healthy, pale, bleached and dead corals, coral rubble, filamentous algae, rocks, and sand were recorded at five reefs during 2010, 2015, and 2018. Between April 2015 and April 2016, the SST was warmer than average, and the ONI showed temperature anomalies near 3, indicating a strong El Niño event. The response of corals varied among reefs and years. No relevant changes in substrata cover were recorded at two reefs through the years, but extensive coral bleaching occurred at the other reefs in June 2015, with dramatic coral mortality as a consequence. An inability to recover and the resulting dominance of filamentous algae over dead corals was evident at two reefs in January 2018. Multivariate analysis based on the cover of substrata and the comparison with previous studies suggested that the response of the coral reefs was not related to the previous state of conservation or the level of anthropogenic impact at each reef. The causes of such thermal resistance are uncertain; nonetheless, it has a high potential to cope with future El Niño impacts.

DSPIR Framework as Planning and Management Tools for the La Boquita Coastal System, Manzanillo, Mexico

Coastal ecosystems are attractive sites for tourism. In the central Pacific coast of Mexico in the La Boquita coastal system (LBCS), consisting of a beach and a coastal lagoon, the Driver-Pressure-State-Impact-Response (DPSIR) model was implemented for the spatial and temporal analysis of socio environmental indicators, aiming to gather information for decision-making and implementation of management strategies. The spatial occupation (umbrellas and tables) of the beach showed a 50–200% increase during the Easter season relative to the low season, while the area containing restaurants (called “ramadas”) increased by 396% in 15 years, representing pressure on land use for tourism purposes. The density of beach users ranged from moderate to high (<10 m2/user) during the holiday seasons in the tourism area. The Trophic index (TRIX), used as an indicator of trophic status, revealed mesotrophic-to-eutrophic conditions in lagoon water due to the limited water exchange with the adjacent ocean and to DIN and DIP inputs from adjacent tourist areas. The analysis of the environmental legislation showed that law enforcement in the LBCS is poor or nil, with most environmental regulations either ignored or having inadequate enforcement monitoring. This has led to the current state of socio environmental disruption.

Presence of Acute Chagas Disease Among Febrile Patients in the Western Coast of Mexico.

Chagas disease (ChD) is a parasitosis caused by the protozoan Trypanosoma cruzi (Tc). It is endemic to almost all Latin American countries, including the southern United States. The acute form of ChD and its actual incidence have rarely been described in Mexico, despite the extensive presence of favorable niches for its transmission. The objective of this study was to estimate the frequency of acute ChD in febrile patients at the central Pacific coast of Mexico. For this, we surveyed patients with persistent fever (5 to 10 days) in five hospitals at the Mexican states of Jalisco, Colima, and Nayarit in 2012. Samples were taken from a total of 485 patients to detect Tc in blood using the polymerase chain reaction (PCR) test and direct microscopic examination. Of these subjects, 10 were positive for PCR and none for microscopic examination (2% in 12 months). We adjusted this rate by the total people at risk in the area and obtained an incidence of 7.4/100,000 habs./year. The positive cases showed no association with sex, rural settlement, or pet ownership, only with the contact with Triatominae insects (odds ratio = 9.22 and confidence interval: 1.93-44.06). The clinical picture of positive patients showed an association with the diagnosis of lower respiratory tract infections. Meanwhile, only one fatal case showed the typical picture of acute fatal cardiomyopathy. The pulmonary manifestations of our patients suggest possible lung pathogenicity of Tc, which merits further investigation. Our findings differ markedly from the official reports for ChD. This difference suggests an underestimation of the disease. These findings urge the Mexican health authorities to implement more vigorous actions aimed at improving medical skills in the timely diagnosis of ChD, as well as to apply efficient preventive programs.

Trophic interactions between the 11 most abundant demersal fish species on the Pacific coast of central Mexico

We describe the diet, feeding strategy, and trophic interactions between the 11 most abundant demersal fish species on the Pacific coast of central Mexico during both the warm and cold seasons. A total of 4,547 stomachs were collected, with 1,921 empty stomachs being discarded. According to the stomach content analysis, 95 prey items were identified and grouped into 70 food categories belonging to crustaceans, mollusks, fish, polychaetes, and echinoderms. The Smith index value and high prey diversity indicated that the 11 fish species exhibited a generalist opportunistic feeding strategy in both survey seasons. Low values of dietary overlap were recorded, and only a few significant cases of dietary overlap were found in the interaction between some rays (Urotrygonidae) and flatfish species (Pleuronectiformes). The availability and abundance of prey resources in the environment and the generalization of niche breadth allows the demersal predator community of the soft shallow bottoms to coexist without any evident competition for trophic resources.

Ecological and population characteristics of the seashell Conus princeps on the Pacific coast of central Mexico

Marine snails of the genus Conus have acquired remarkable biomedical importance because of the high number of toxins they produce for feeding and self-defense. One of these toxins gave way to a new medication and two other are under development for clinical and cosmetic purposes. Nevertheless, there is little basic knowledge about this group of species, particularly in Mexico. This study aimed to determine the relative abundance, spatial distribution, bathymetric distribution, and habitat preference of the snail Conus princeps along the southern coast of Jalisco (Mexico). To achieve this goal, we conducted direct samplings by snorkeling or scuba diving at 13 beaches, covering the intertidal, shallow subtidal, and deep subtidal zones. Relative density was between 0.021 and 0.418 snails per 100 m2, with an average value of 0.152 snails per 100 m2. The population showed an aggregated spatial distribution pattern according to the nearest neighbor index. Snails had shells that measured between 23.1 mm and 52.2 mm long, with an average shell size of 39.7 mm. Conus princeps was mainly distributed in the intertidal and shallow subtidal zones. The smaller organisms were present at shallower depths, while the larger organisms were distributed throughout the sampled depth habitats. In general, snail abundance decreased as depth increased. From the underwater photography analysis, we determined that Conus princeps snails prefer rocky bottom habitats covered with brown seaweed.

First verified record of Anolis sagrei Cocteau in Duméril and Bibron, 1837 from the central Pacific coast of Mexico

First verified record of Anolis sagrei Cocteau in Duméril and Bibron, 1837 from the central Pacific coast of Mexico

Bilingually traversing the US/Mexico "wall" via a classroom telecollaborative exchange: Translanguaging online with the Functional Approach to Code-switching Electronically (FACE)

This study proposes to make the concept of translanguaging online accessible for teachers who wish to connect their classrooms with students in other countries via telecollaboration projects. I explore the role of instructed code-switching, as a strategic and intentional translanguaging strategy, for developing learners’ symbolic competence and in promoting the kind of communication in transnational telecollaboration projects that leads to positive bilingual identity and language development. The majority of telecollaboration projects reported in the literature describe projects at the university language classroom setting and the varied dysfunctions that may lead to “failed communication” (O’Dowd & Ritter, 2013) or “missed communication” (Ware, 2005). In contrast, the study within describes the successful impact of a pedagogical intervention, the Functional Approach to Code-switching Electronically (FACE) (Author, 2014), that fostered intercultural understanding among public high school students in an American Government class in the Southwestern United States and students in an English as a Foreign Language (EFL) class in the Central Pacific Coast of Mexico. Findings demonstrate how teachers can adopt translanguaging practices in their classrooms by instructing the purposeful use of code-switching for facilitating the development of students’ L2, content acquisition, symbolic competence, and positive identities as bilinguals. In doing so, students are given the strategies needed to successfully play within the power games situated across semi-anonymous online borders, walls, and contact zones (Vinall, 2010). DOI:10.2458/azu_itet_v5i2_przymus

Ocean–atmosphere conditions related to severe and persistent droughts in the Mexican Altiplano

ABSTRACTOcean and atmospheric patterns associated with the most severe and most persistent droughts in the Mexican Altiplano region are explored. The standardized precipitation index on a time scale of 12 months was used and compared with time series of other atmospheric conditions to identify major dry episodes from 1970 to 2012. The time series were derived from the second mode of a varimax‐rotated empirical orthogonal functional analysis from the mean summer rainfall series observed at weather stations located in the Mexican Altiplano from 1970 through 2000. The results showed that the longest and most persistent episode occurred from 1998 through 2001, while the most severe dry episode occurred in 2011–2012, when the Pacific Decadal Oscillation was in a negative phase and the Atlantic Multidecadal Oscillation in a positive phase, both in combination with a La Niña event. A large upper‐level anticyclone over the north‐central United States is related to droughts in the Altiplano. Under these conditions, the droughts were linked to a large anticyclone positioned over the central‐north of the United States, with consequent negative anomalies of specific humidity over central‐northern Mexico. Concurrent with droughts in the interior of Mexico, are positive rainfall anomalies along the central Pacific coast of Mexico near the study area. Under different atmospheric conditions, opposite anomalous behaviour between the coast and interior can exist. The mechanism driving this see‐saw behaviour between the west coast of Mexico and the Altiplano is explored.

First record and range extension of the Galapagos slipper lobster, Scyllarides astori (Decapoda, Scyllaridae) in the central Pacific coast of Mexico mainland.

The Galapagos slipper lobster Scyllarides astori was found for the first time off western Mexico mainland. A male and two female specimens were collected in south Jalisco and north Colima. This represents a new record from central Pacific coast of Mexico and a range extension of 700 km southwards, as the species was previously reported from the Gulf of California, 780 km eastwards from Revillagigedo Archipelago and 2400 km northwestwards from Isla del Coco and Galapagos Archipelago.

Parasites of the green jack Caranx caballus (Pisces: Carangidae) in three locations from Pacific coasts of Mexico, and their utility as biological tags

Parasites are known to be useful as biological tags in distinguishing fish stocks, but the parasite fauna method has received limited use in the fisheries of Mexico. Parasite fauna composition and their infection levels were quantified for Caranx caballus populations at 3 locations on the south central Pacific coast of Mexico. Three hundred eighty-eight fish were collected and examined between December 2009 and February 2012. Twenty-four species of parasites were identified: 2 monogeneans, 6 digeneans, 1 cestode, 5 nematodes, 8 copepods, and 2 isopods. At the component community level, species richness of parasites varied significantly from 9 to 18 (in 2011 and 2012, respectively, for Acapulco Bay), and was similar to previous reports for other species of Carangidae. The component communities and infracommunities of C. caballus exhibited a similar pattern: low species numbers, low diversity, and dominance by a single species. Multivariate discriminant analysis used to distinguish between the C. caballus populations, indicated that each location can be considered as a different fish stock, and that C. caballus, therefore, does not migrate between the studied locations, even though they are close from each other.

Flowpaths, source water contributions and water residence times in a Mexican tropical dry forest catchment

Summary Runoff in forested tropical catchments has been frequently described in the literature as dominated by the rapid translation of rainfall to runoff through surface and shallow subsurface pathways. However, studies examining runoff generation in tropical catchments with highly permeable soils have received little attention, particularly in tropical dry forests. We present a study focused on identifying the dominant flowpaths, water sources and stream water residence times in a tropical dry forest catchment near the Pacific coast of central Mexico. During the wet season, pre-event water contributions to stormflow ranged from 72% to 97%, with the concentrations of calcium, magnesium, sodium and potassium closely coupling the geochemistry of baseflow and groundwater from the narrow riparian/near-stream zone. Baseflow from the intermittent stream showed a strongly damped isotopic signature and a mean baseflow residence time of 52–110 days was estimated. These findings all suggest that instead of the surface and near-surface subsurface lateral pathways observed over many tropical catchments, runoff is generated through vertical flow processes and the displacement and discharge of stored water from the saturated zone. As the wet season progressed, contributions from the saturated zone persisted; however, the stormflow and baseflow geochemistry suggests that the contributing area of the catchment increased. Our results show that during the early part of the wet season, runoff originated primarily from the headwater portion of the catchment. As the wet season progressed and catchment wetness increased, connectivity among sub-basin was improved, resulting in runoff contributions from across the entire catchment.

Soil water storage, rainfall and runoff relationships in a tropical dry forest catchment

AbstractIn forested catchments, the exceedance of rainfall and antecedent water storage thresholds is often required for runoff generation, yet to our knowledge these threshold relationships remain undescribed in tropical dry forest catchments. We, therefore, identified the controls of streamflow activation and the timing and magnitude of runoff in a tropical dry forest catchment near the Pacific coast of central Mexico. During a 52 day transition phase from the dry to wet season, soil water movement was dominated by vertical flow which continued until a threshold soil moisture content of 26% was reached at 100 cm below the surface. This satisfied a 162 mm storage deficit and activated streamflow, likely through lateral subsurface flow pathways. High antecedent soil water conditions were maintained during the wet phase but had a weak influence on stormflow. We identified a threshold value of 289 mm of summed rainfall and antecedent soil water needed to generate >4 mm of stormflow per event. Above this threshold, stormflow response and magnitude was almost entirely governed by rainfall event characteristics and not antecedent soil moisture conditions. Our results show that over the course of the wet season in tropical dry forests the dominant controls on runoff generation changed from antecedent soil water and storage to the depth of rainfall.

Oxidative damage associated with thermal stress in Pocillopora verrucosa from the Mexican Pacific

Coral communities are under increasing pressure from anomalous increases in sea surface temperature. These events have had negative effects on reef ecosystems and it is important to get a better understanding of the cellular mechanisms that allow organisms to survive the stress period before bleaching is evident. To gain insight into the effect of increased temperature on coral communities off the Pacific coast of central Mexico, we evaluated CuZnSOD (superoxide dismutase) activity in branches of Pocillopora verrucosa by simulating stress conditions (31 ºC) and non-stress conditions. There was an increase in SOD activity after 18 h of exposing the corals to 31 ºC, while no increase in activity was observed at 28 ºC. These results were used to quantify the maximum levels of CuZnSOD activity before Symbiodinium were expelled to prevent cell damage due to oxidative stress. We determined that CuZnSOD can be used as a molecular marker to quantify stress levels, prior to bleaching, in coral communities of the region.

Recent increase in the distribution of the snail kite (Rostrhamus sociabilis) along the central Pacific Coast of México

New records of the snail kite (Rostrhamus sociabilis) are presented for the central Pacific Coast of Mexico. From April 2010 to August 2011, weekly or biweekly surveys were made through several wetlands of coastal Jalisco and Colima. We recorded 32 snail kites from October 2010 to August 2011. The recordings were in 8 wetlands. In all wetlands there was only 1 individual, except in the lagoons El Aguacate (June 2010) and El Tule (August 2012), where we recorded 3 and 5 individuals, respectively. Although we did not find any nests, we believe reproduction of snail kites is currently occurring because of the observed adult behavior (carrying small branches in its feet) and the records of juveniles during the month of February to July, a time corresponding to the breeding season of the species in Florida. Our records expand the distribution of the snail kite in Mexico as much as 900km northwest of the previously published distribution of the species.

Land use changes and impact on coral communities along the central Pacific coast of Mexico

The loss of coral coverage from environmental degradation is a progressive phenomenon that occurs in coral communities around the world. However, the consequences of land use changes and its impact on the state of conservation of coral communities are not yet understood. This study compares the impact of coastal land use changes on four coral communities near rural (Isla Faro and El Zapote) and suburban (Caleta de Chon and Playa Manzanillo) sites in the states of Michoacan and Guerrero, along the central Pacific coast of Mexico. Indicators of environmental degradation in coral communities (sediment deposition, water transparency, total suspended solids, and chlorophyll concentration) show that signs of eutrophication are absent from both rural sites in Michoacan. This absence suggests that human impact is not the main cause of the observed degradation (coral Mortality Index MI = 0.85, a high death coral coverage ~42% and the lowest species richness). Instead, the 1997–1998 El Nino-Southern Oscillation (ENSO) event (the strongest in the last decade) appears to be the major factor in this coral cover decline, as it occurred in the eastern Pacific and other regions of the world. In contrast, coral communities near the suburban sites in Guerrero are well developed, and their coral coverage and species richness (up to 67.7% and 7 species, respectively) are comparable to other major coral communities in this region. Nonetheless, indicators of human-derived degradation in the Guerrero coastal zone near Caleta de Chon and Playa Manzanillo, including high sediment deposition up to 1.2 kg m−2 d−1, low water transparency <5 m, presence of filamentous algae on dead corals and a coral Mortality Index of MI ~0.6 show that human impact is beginning to affect the conservation state of these coral communities, reducing their species richness and coral coverage. Although the ENSO impact on coral communities could be more drastic than the anthropogenic impact, the current study confirms that increased land use changes and coastal erosion are causing progressive coral community degradation. Therefore, land and coastal changes must be rigorously regulated.

Feeding habits of three round stingrays (Rajiformes: Urotrygonidae) in the central Mexican Pacific

Stomach contents and dietary overlap of three round stingray species (Urobatis halleri, Urotrygon munda, and Urotrygon rogersi) captured off the central Pacific coast of Mexico were analyzed during the two main hydroclimatic periods (T1 and T2) that characterize the environmental variability in the area. The three round stingray species showed a narrow bathymetric distribution range, and the highest abundances were located at 20 m depth in both seasons. In general, the diets were mainly composed of benthic microcrustaceans (caridean shrimps) and to a lesser extent of fishes, polychaetes, and molluscs. The most abundant prey items in the diets were carideans of the families Processidae and Ogyriididae, and penaeids, followed by brachyuran and stomatopod larvae. All three stingrays exhibited a generalist feeding strategy. The diets showed high overlap values during period T1 in both inter- and intraspecies analyses, but lower values during period T2. There was no evidence of ontogenetic diet changes and sex was not a factor for trophic differences. The slight differences among diets were due to seasonal changes in the soft-bottom macrobenthic invertebrate assemblages in the shallow waters, and relationships like predation and competition were not the main factors influencing the population dynamics of the three stingray species.