Search Results (97)

We use 29 years of altimeter-derived sea level anomalies and geostrophic velocities (1993–2021) from the Copernicus Marine Service to identify the Mexican Coastal Current (MCC) and to examine how it interacts with the coastline. Variance-ellipse and empirical orthogonal function analyses isolate a narrow alongshore jet with a mean width of about 95 km and average speeds near 0.3 m ${\mathrm{s}}^{-1}$ that reverses direction semiannually: poleward in June and July and equatorward in the rest of the year. When the MCC impinges on broad concavities in the coast, the boundary layer separates, forming recirculation cells that intensify and detach as coherent eddies. These near-shore eddies have similar radii (from ∼30 km) and relative vorticity of $\pm 0.5\times {10}^{-5}$${\mathrm{s}}^{-1}$ at the beginning of their generation, and they propagate offshore once the current weakens. A simple numerical model reproduces the observed behavior and suggests that eddy formation is controlled by flow separation rather than generic instability. The semiannual change in direction of the MCC indicate a link with the larger-scale North Equatorial Countercurrent and Costa Rica Coastal Current systems of the eastern tropical Pacific. Full article

Pleurobrachia pileus and P. bachei are among the most frequently recorded ctenophores worldwide. Despite their long-standing descriptions dating back nearly 250 years, their taxonomic boundaries remain ambiguous due to the lack of definitive diagnostic features. In Mexican waters, records of both species are primarily based on geographic distribution, with limited morphological evidence supporting their separation. This study aimed to evaluate the morphological diversity of Pleurobrachia spp. along the Mexican coast through a comprehensive morphological approach. Specimens from four sites representing two marine regions (the Gulf of Mexico and the Southern Mexican Pacific coast) were examined for phenotypic variation. A standardized methodology was developed for specimen handling, observation, and digital reconstruction of body plans, enabling the extraction of 38 discrete and continuous morphological traits. Our analysis revealed two distinct and internally consistent phenotypic groups, each corresponding to one of the two regions, with notable differences in tentacular sheath structure, tentacular canals, gastrovascular cavity pigmentation pattern, and pharyngeal morphology. A clinal pattern in body size was observed, with smaller specimens in the north and larger ones in the south. Importantly, neither phenotype matched the diagnostic traits of P. pileus or P. bachei, suggesting that the Mexican populations represent separate, previously unrecognized species. These findings highlight the necessity to re-evaluate the taxonomy of Pleurobrachia in these regions and contribute valuable morphological data toward resolving longstanding questions about species boundaries within this genus. Full article

The swimming crab is a commercially and nutritionally important marine resource with the highest catch volumes in Mexico occurring along the East Pacific coast. Among the Pacific species of the genus Callinectes, the blue crab C. arcuatus has the widest distribution and is found throughout the year. Its close resemblance to the well-studied Atlantic blue swimming crab (C. sapidus) makes it an excellent model for molecular reproductive studies in the Mexican Pacific. Using next-generation sequencing, this study aimed to characterize maturation-associated genes in an ovary–hepatopancreas transcriptome of C. arcuatus, with a particular focus on vitellogenin (Vtg) and its expression in the ovaries and hepatopancreas across different gonadal maturity stages. The transcriptome library generated from pooled samples produced 27,729 unigenes, of which, 196 (1.81%) were identified as reproduction-related genes. Notably, 33 of these genes, including the complete Vtg sequence, have not been previously reported in this species. Vtg expression was found to be tissue-specific, with levels in the hepatopancreas up to 13 orders of magnitude higher than in the ovary. In the hepatopancreas, Vtg expression increased exponentially from stage I to stage V of gonadal maturity, whereas in the ovaries, its expression showed the opposite trend. These findings highlight that the hepatopancreas, with its abundant nutrient reserves, serves as the primary site of Vtg expression and synthesis. Full article

Bahía de La Paz is the largest bay in the southern Gulf of California. This bay is an important area with a variety of commercial fish species and other natural resources and recreational activities. Epibenthic dinoflagellates are common inhabitants of harbors, inlets and semi-enclosed coastal lagoons; they produce potent toxins that may negatively affect human health and marine biota. The purpose of the present study was to identify potentially harmful epibenthic dinoflagellates growing on macroalgae from different coastal sites of the bay to determine their species composition, abundances, seasonal distributions, interannual and spatial variations. A total of 153 quantitative samples were collected in 2015–2019 (at 10 sites during four samplings in May, June and December) mainly from macroalgae. About 23 dinoflagellate species from the genera Prorocentrum, Ostreopsis, Sinophysis, Gambierdiscus, Fukuyoa, Amphidinium, Blixaea, Bysmatrum, Cabra, Coolia, Durinskia and Plagiodinium were found as epiphytes on at least 58 macroalgal species of 42 genera. Toxigenic genera, such as Gambierdiscus, Ostreopsis, Coolia and Prorocentrum, were widespread throughout the study area. Playa El Tecolote and Playa Costa Baja were the best habitats for dinoflagellates; therefore, the two locations can be considered the beaches with the greatest risk to human health. Full article

There has been an increasing interest in studying species of the thecate dinophysoid dinoflagellates, especially the genera Dinophysis and Phalacroma, all around the world. Abundant net phytoplankton material collected from coasts of the western coast of Baja California, the central Mexican Pacific (including the Gulf of California), and the Gulf of Mexico was analyzed, and the diversity and morphology of planktonic species of dinophysoids were studied in certain detail by LM and SEM. Particular morphological characteristics, which can be critical, such as the structure of the cingulum and cingular lists, union of sulcal lists, and theca ornamentation, were observed using SEM. Seventy-five (75) taxa (73 species and two varieties) were found and identified, which belong to the following 10 genera: Amphisolenia, Citharistes, Dinofurcula, Dinophysis, Histioneis, Metaphalacroma, Ornithocercus, Oxyphysis, Phalacroma, and Pseudophalacroma. We also included the following four new records: three for the Mexican Pacific (Amphisolenia brevicauda, A. deltiana, and Phalacroma stenopterygium) and one for the Gulf of Mexico (Phalacroma ornamentatum). Descriptions, illustrations, measurements, and distribution data are provided for each species. Taxonomical remarks concerning synonymies of species of the genus Phalacroma were added. Phalacroma whittingiae (Balech) Esqueda-Lara et Hernández-Becerril nov. comb. is a new taxonomic proposal. Full article

Temperature affects the morphology, physiology, and distribution of marine macroalgae, as supported by studies that used long-term data from herbaria. In the present study, sea surface temperature (SST), latitudinal distribution, and La Niña or El Niño years were correlated to the morphology of two macroalgal species of the Mexican Pacific: Ceratodictyon tenue and C. variabile. Twenty-four morphological characteristics were evaluated, and 95 samples from 1965 to 2013 in the Escuela Nacional de Ciencias Biológicas herbarium were reviewed. In 2017, 2023, and 2024, 12 specimens were sampled at three locations. Low positive correlations were found between thallus diameter and SST for C. tenue, while low positive correlations were detected for thallus length and medullary cell diameter vs. SST and medullary cell length vs. year for C. variabile. Significant relationships were found between the thallus length and cortical cell diameter of C. variabile with latitude and SST. It is concluded that SST contributes to changes in morphology, but is not the only factor that affects them. For the first time in a tropical area, the present study explores whether there is a relationship between SST, latitudinal distribution, and El Niño and La Niña years and the morphology of a genus of red algae. Full article

Pelagic nudibranchs exemplify evolutionary convergences towards streamlined, transparent body forms adapted for life in the planktonic environment. Here, we describe a new genera and species, designated as Pleuropyge melaquensis gen. et sp. nov. This species belongs to the family Phylliroidae and is distinguished by key diagnostic characters, including a laterally positioned anus approximately one-third of the body length from the head, the absence of a cephalic disc, and an anterior hepatic caecum that is longer than the intestine. The description of P. melaquensis contributes to the classification of a third genus and a fourth species within the Phylliroidae family. This study offers novel insights into the functional and structural traits that have enabled nudibranchs to transition from benthic to pelagic environments. Full article

Currently, the management, availability, and equitable access to water are some of the most critical environmental challenges in many countries, including Mexico. The Household Water Insecurity Experience Scale (HWISE) offers a more comprehensive and accurate assessment of water insecurity (WI) as well as its relationship to poverty, at the local, state, and national levels, than traditional usage indicators do. Therefore, this study aims to estimate the association between water insecurity and household wellbeing in Mexico, as well as the role of geographic factors. Methods: We analyzed data from 11,512 households that had previously participated in a representative survey at the national, regional, and urban/rural levels. We conducted descriptive and bivariate analyses on the variables of interest according to household WI status. Multivariate logistic regression models were used to determine the association between WI and the geographic, household, and household head variables of interest. Results: The factors associated with a greater odds ratio of household WI were low wellbeing conditions (OR = 1.74, p < 0.01), no running water in the home (OR = 2.71, p < 0.01), a monthly household income less than 6000 Mexican pesos (less than 352 dollars) (OR = 2.31, p = 0.006), living in an urban area (OR = 1.93, p = 0.001), and living in the Mexico State (OR = 3.92, p < 0.01), Mexico City (OR = 3.19, p < 0.01), or Central Pacific (OR = 3.27, p < 0.01) regions. Conclusions: Currently, multiple factors threaten household water security. These findings can inform decision-makers about the driving factors behind gaps in water access, availability, and use in Mexican households, thereby ensuring the “availability and sustainable management of water and sanitation for all”. Full article

Cephalopods have been widely studied around the globe. However, some areas are poorly understood. In Mexico, there is a significant lack of knowledge, particularly in the coastal zone of the eastern Pacific Ocean, where most studies have focused on commercial fisheries. An exhaustive review of documents (articles, books, theses, and regional reports) dealing with the cephalopods of the eastern Pacific in general and of Pacific Mexico in particular was undertaken along with an examination of malacological collections and databases available in Mexico and the USA. As a result, we obtained 3752 records corresponding to 3339 taxonomic records, featuring two superorders, six orders, 29 families, 60 genera, and 105 species. Of these, 89 species occurring in Mexican waters were confirmed, 76% pelagic, 21% in strictly benthic habitats, 2% benthopelagic, and 1% corresponding to demersal species. We proposed a modification for the distribution of 21 species and found 10 new records for Mexican waters. Full article

Globally, coastal wetlands are among the most dynamic and important environments due to their wide range of environmental services, from which coastal communities benefit. Mexico has coastal wetlands that are a priority in the Pacific Flyway in America, since every year millions of shorebirds use these wetlands to reproduce and rest during their migration, in addition to various species that live there and are under some protection standard or in danger of extinction. In addition, these Mexican wetlands are also spaces from which important growing coastal communities benefit. However, the conservation of these coastal sites will be compromised in the coming decades by sea level rise and increasing pressure derived from coastal development, which directly impact the potential loss of space and consequently the decrease in migratory bird populations. This work identifies hydrodynamic changes and the effects of sea level rise in five coastal wetlands in Mexico and the Pacific Flyway in America, focusing on the future availability of space and the potential loss of ecosystem services under projected scenarios. The results generated give us a knowledge base to design strategies focused on the conservation and resilience of these wetlands in the face of sea level rise. Full article

Research on the trophic transfer of trace elements in food chains, particularly toxic elements like mercury (Hg) and essential elements like selenium (Se), is crucial for understanding their impact on human health. In this work, we assessed the transfer of Hg and Se in the blue shark (Prionace glauca), a top predator with economic importance. Muscle samples from sharks, as well as their main prey (squid, red shrimp, sardine, and mackerel), were analyzed for Hg and Se concentrations. The Hg levels of sharks were below the recommended legal limit for seafood consumption in Mexico (1 µg·g⁻¹ ww), while Se levels were significantly lower than previously reported for the species. Biomagnification was evaluated in this species by calculating biomagnification factors (BMF) for Hg and Se based on predator-prey element concentrations. Hg showed a BMF of 2.8, indicating biomagnification, while Se had a BMF of 0.2, suggesting biodilution. Trophic transfer factor models supported these findings, showing a positive correlation of Hg concentration with trophic level and a negative correlation with Se. However, while a hazard quotient under one does not pose a risk for consumption, a Se:Hg molar ratio under one estimated in the muscle tissue indicates that Hg levels along this food web should be approached with caution. Full article

Meteorological droughts are a complex and recurring phenomenon in Mexico, posing significant challenges for water availability, ecosystems, and socio-economic activities. Furthermore, several worldwide studies highlight that the impacts of droughts may intensify due to the potential effects of climate change. Using projections from global climate models in the Coupled Model Intercomparison Project Phase 6 (CMIP6), this study evaluates future trends in drought frequency and severity across the Mexican hydrological regions. We applied the Standardized Precipitation Index (SPI) to assess meteorological drought indicators under two Shared Socio-economic Pathway (SSP) scenarios (SSP2-4.5 and SSP5-8.5) for the periods 2040–2069 and 2070–2099. Climate models show high variability in projected precipitation changes between the reference and future periods. The SSP5-8.5 scenario indicates the greatest decrease, with reductions of at least 5 to 10%, and even larger declines projected for hydrological regions along the Pacific and Gulf of Mexico coasts, as well as the Yucatán Peninsula. Changes in drought indicators vary depending on the time horizon and scenario considered. For instance, projections for the period 2070–2099 under the high-emission scenario SSP5-8.5 suggest more frequent (three to four events) and prolonged (15 to 18 months) droughts in central and southern hydrological regions. These insights highlight the urgency of strengthening water management policies and adaptive strategies to mitigate the anticipated impacts of climate change on Mexico’s water resources. Full article

The present study analyzed the growth pattern of the stingray Urotrygon chilensis caught as bycatch by the shrimp fishery in the southeastern Mexican Pacific. From January to December 2012, the thoracic vertebrae of 491 females and 205 males were collected. Female ages ranged from 0 to 14 years, whereas male ages ranged from 0 to 12 years. The marginal increment and edge analyses suggested the annual formation of growth bands in the vertebrae. The size-at-age data were analyzed using the multimodel inference approach; six candidate growth models were compared, including models with a theoretical age-at-zero total length, mean size-at-birth, and generalized models. Based on Akaike’s information criterion, the best statistical fit to the size-at-age data was the two-phase Gompertz growth model (k = −0.13, G = 1.59, $L_0$ = 10.40) for males and the two-parameter Gompertz growth model (k = 1.42, α = 0.15, $L_0$ = 10.90) for females. In this study, we compare the growth parameters among batoid species, finding that U. chilensis has a relatively short lifespan, slower growth, and that females are larger than males. Full article

This paper analyzes phytoplankton communities in the Eastern Tropical Pacific Ocean off Mexico (ETPOM) and the Southern Gulf of California (SGC) during the strong El Niño event of 2023/24. A multidisciplinary research cruise was conducted in the winter of 2024, during which high-resolution hydrographic data and water samples for phytoplankton cell determinations were collected at 33 sites. Additionally, satellite data were obtained to evaluate sea surface temperature and chlorophyll-a levels. A total of 269 phytoplankton species were identified, comprising one hundred and fifty diatoms, one hundred and twelve dinoflagellates, five silicoflagellates, one ciliate and one cyanobacteria. The dominant species included the diatom Pseudo-nitzschia pseudodelicatissima, the dinoflagellate Gyrodinium fusiforme, the silicoflagellate Octactis octonaria, and the ciliate Mesodinium rubrum. The cyanobacterium Trichodesmium hildebrandtii was also identified. In terms of total abundances, diatoms were the most prevalent, with 224,900 cells L⁻¹, followed by dinoflagellates at 104,520 cells L⁻¹, ciliates at 20,980 cells L⁻¹, cyanobacteria at 1760 cells L⁻¹, and silicoflagellates at 1500 cells L⁻¹. Notably, interesting differences emerged in species richness and abundance when comparing both regions. These results enhance our understanding of phytoplankton dynamics associated with strong El Niño events. The ETPOM remains a region that requires further monitoring through in situ observations. Full article