The annual occurrence of harmful algal blooms (HABs) of the dinoflagellate Gymnodinium catenatum in the northern Gulf of California (NGC) during winter and spring has negative ecological, economic, and social impacts on the local coastal population. G. catenatum produces paralytic shellfish toxins, and a robust monitoring program of the species is necessary to sustain mitigation actions against their detrimental effects. Here, we applied the maximum-likelihood classification (MLC) method to classify satellite images from MODIS and Sentinel-3 to evaluate their effectiveness to detect G. catenatum. Different classes associated with the presence of the species were developed from data of two HABs that occurred in 2015 and 2017. Two classes derived from Sentinel-3 data from the 2017 HAB allowed the detection of this species. These Sentinel-3 classes adequately represented the temporal and geographical distribution of G. catenatum in the region and the no-bloom condition during the summer. The concordance between the detection of the Sentinel-3 classes on the west coast of the NGC and the recorded presence of G. catenatum (75% of concordance) in the area indicates that the MLC method could be applied for early detection of the species in the NGC, using Sentinel-3 full resolution images.

El lago-cráter de Santa María del Oro en el estado de Nayarit, México, presenta Florecimientos Algales (FA) de manera cíclica anual, el florecimiento y posterior decaimiento de estas poblaciones de crea cambios de color en el agua, generalmente en la primera mitad del año. Este trabajo evalúo algoritmos de clasificación supervisada que permitan identificar estos cambios usando datos de los productos MOD09GQ y MYD09GQ del sensor MODIS en el período de enero 2003 a diciembre 2020. A partir de una revisión de FA registrados en la literatura y análisis estadísticos de gráficos de dispersión, se construyó una base de datos de información espectral y etiquetas del estado de color del lago para evaluar los diferentes algoritmos de clasificación. El mejor clasificador fue Random Forest con una precisión de 87.1 %, El análisis temporal y la evaluación espacial de la incidencia de los florecimientos mostraron que mayo, abril y marzo son los meses con mayor presencia de cambios de color en el lago relacionados a FA. En el análisis espacial se encontró que la mayor incidencia de florecimientos se da en la región sureste del lago y las mayores cantidades de eventos ocurrieron en los años 2011, 2008 y 2012 respectivamente. Se determina la influencia del fenómeno El Niño- Oscilación del Sur (ENSO) en la incidencia de florecimientos algales en el lago-cráter debido al patrón temporal entre las anomalías en los FA y el índice multivariado de El Niño-Oscilación del Sur, donde el mayor número de eventos de FA se presentaron en las fases frías del ENSO.

Diatoms interact with aquatic environments in such a manner that their distribution determines how other organisms are distributed, e.g., bivalve mollusks who feed on them. The aim of this study was to determine if the diatom taxa filtered by Crassostrea corteziensis in the wild remained constant or changed due to substrate, site or season in which they grow. Thus, we tested the null hypothesis (H₀) that the species composition of diatoms filtered by oysters from different substrates, sites and seasons were to be similar. So, diatoms extracted from the digestive tract of oysters from different substrates, sites, and seasons were identified and quantified. Diatom structure was described based on ecological indices (H', N1, J', 1-λ). Similarity measured using the Bray-Curtis index, from which a PERMANOVA test was performed and graphed using non-metric multidimensional scaling (nMDS) and similarity profile (SIMPROF). Analyses indicated that diatom assemblages filtered by oysters varied by site and season, but not by substrate. The diatom assemblages defined by sites were characterized by Neodelphineis silenda, Thalassionema nitzchioides, Cymatotheca complex (C. weissflogii and C. minima), and Navicula sp. 5; while the diatom assemblages defined by seasons were characterized by N. silenda, Skeletonema costatum, Aulacoseira granulata, and A. granulata var. angustissima. Meanwhile, N. silenda, T. nitzschioides, and Cymatotheca complex remained constant throughout the substrates. The evidence generated allows us to conclude that C. corteziensis filtered on the same diatom assemblage regardless of the substrate in which it was found; however, these assemblages differed depending on the site and the season.

Statistics were generated for tropical cyclones (TCs) that made landfall along the Mexican coast during 1965-2024 using the International Best Track Archive for Climate Stewardship (IBTrACS). Monthly, annual, and decadal cumulative events were calculated and disaggregated by TC category according to the Saffir-Simpson scale and oceanic basin (Atlantic and Pacific). Additionally, the relationship between TC landfalls and El Niño-Southern Oscillation (ENSO), the Atlantic Multidecadal Oscillation (AMO), and the Pacific Decadal Oscillation (PDO) was analyzed. In Mexico, most TC landfalls (66%) originated in the Eastern Tropical Pacific (ETP) basin. Although the total number of ETP systems making landfall shows no significant trend, the number of major hurricanes (Category 3 or higher) making landfall shows a significant increase during the study period, particularly over the last two decades. In contrast, along the Atlantic Mexican coast, the total number of TC landfalls has increased in recent years, while major hurricane landfalls do not show a significant trend. Landfalls associated with TCs originating within the Gulf of Mexico have also increased. Regarding the relationship with natural climate oscillations, a positive correlation was found between ENSO and major hurricane landfalls in the ETP. On the Atlantic side, years characterized by La Niña or neutral ENSO phase conditions combined with a negative PDO and a positive AMO phase tend to exhibit higher TC landfalls on Mexican coasts. Conversely, during El Niño conditions combined with a negative PDO, TC landfalls tend to decrease, particularly during a negative AMO phase.

Lakes represent a significant component of the planet’s freshwater reserves which are highly vulnerable to pollution, overexploitation, and climate change. In these systems, biodiversity loss due t...