El Hombre y su Ambiente

A taxonomic study of diatoms was carried out in a tropical coastal lagoon. Material for this study consists of water samples obtained from February-March 1992 to November-December 2000. Qualitative and quantitative analyses showed the presence of 373 taxa of which the families Bacillariaceae (67 species) and Chaetocerotaceae (37 species) were the most abundant groups. The species Skeletonema costatum, Chaetoceros curvisetus, Coscinodiscus radiatus var. radiatus, Ditylum brightwellii, Thalassiosira eccentrica and Entomoneis alata were found associated with moderate water quality and forming blooms. In addition, a regional comparison between Mexico and South America of the identified species is given. For practical handling, indicative values obtained from their ecological composition are incorporated as well as a code of the floristic list. A checklist of the species and their occurrence are given.

Guadalupe de la Lanza Espino, étal. en la concentración salina y de nutrientes a través de cambios de las masas de agua, como fue determinado por Caffrey y Day {1986} en el estuario del Río Atchafalaya. A pesar de que existe una variabilidad en la distribución de los compuestos ...

A taxonomic study of diatoms was carried out in a tropical coastal lagoon. Material for this study consists of water samples obtained from February-March 1992 to November-December 2000. Qualitative and quantitative analyses showed the presence of 373 taxa of which the families Bacillariaceae (67 species) and Chaetocerotaceae (37 species) were the most abundant groups. The species Skeletonema costatum, Chaetoceros curvisetus, Coscinodiscus radiatus var. radiatus, Ditylum brightwellii, Thalassiosira eccentrica and Entomoneis alata were found associated with moderate water quality and forming blooms. In addition, a regional comparison between Mexico and South America of the identified species is given. For practical handling, indicative values obtained from their ecological composition are incorporated as well as a code of the floristic list. Achecklist of the species and their occurrence are given.

The recent interest in the plankton structures and dynamics in tropical and subtropical lakes has revealed important trends that set these lakes apart from temperate lakes, and one of the main differences is the enhanced importance of the microbial food web with respect to net plankton. Ciliates are a key component of subtropical and tropical microbial webs because of their role as dominant picoplankton grazers and their ability to channel picoplankton production to the uppermost trophic levels. Plankton ciliates have been found to play a crucial role in the survival of fish larvae in lakes that share several features with Lake Catemaco, a eutrophic tropical Mexican lake. Therefore, the plankton ciliate composition, abundance, and biomass of Lake Catemaco were studied to assess their role in the microbial food web. The data were obtained from surface and bottom water samples collected at eleven points during three surveys in 2011 and an additional survey in 2013, with the surveys co...

We determined the structure of the phytoplankton community along a circadian cycle and itsrelation to species Harmful Algae Species (HAB), at the mouth of the coastal lagoon, Sontecomapan Veracruz, during the 27th and 28th of October, 1999. Water samples were collected every two hours employing a van Dorn bottle, to measure temperature, salinity, pH, dissolved oxygen, the composition and abundance of phytoplanktoncommunity and reviewed the behavior of ebb and flow of tides. In order to describe the behavior of the community the following criteria were used: simple dominance index, the Shannon diversity (H ‘), the Pielou equity (J`) and a canonical correspondence analysis was applied to understand the relationship between the abundance ofphytoplankton species and environmental variables. The results showed a total of 179 taxa, 27 of which form HAB elsewhere. At 11:00 hours on October 27 and 28 maximum values of H ‘= 5.8, J`= 0.9 are reported, the minimum of H’= 3.79, J`= 0.6 at 15:00...

The objective of this study was to estimate electromagnetic pollution by radio frequency (RF) and magnetic field (CM) over one year by measuring the intensity near schools, hospitals, business premises, and homes in a commercial and a residential zone of Xochimilco, México City. The RF and the CM were measured using an EXTECH® EMF450 meter. We compared the values of nonionizing radiation (NIR) found in the environment with the levels reported to affect the biological systems of both humans and animals. We also compared these values with the limits established both nationally and internationally. The highest average CM and RF values in the central zone were 6.38 μT and 1316 μW/m2, respectively, while in the housing area, they were 5.08 μT and 66 μW/m2. The values we registered were below the permissible limits both nationally and internationally. However, they were above the reported threshold that could trigger adverse health effects according to some authors. These values are withi...

Coyotes (Canis latrans) and gray foxes (Urocyon cinereoargenteus) are abundant and widely distributed in México, with no information currently available about their spatial interactions in the country. Our objectives were to evaluate the habitat use of these species and the environmental interactions between them throughout the overlapping areas of their home ranges in temperate forests of Durango, México. We expected that their coexistence would be facilitated by the spatial segregation of their ecological niche, exhibited by the low or nil overlap between their home ranges or by differentiated habitat use. Radio-collars (VHF) were attached to nine individuals-four coyotes (two males and two females) and five gray foxes (females)-that were radio-tracked from September 2017 to August 2019. We estimated their home ranges and the size of their core areas through the minimum convex polygon and determined the extent of overlap between them. Also, we evaluated third-order habitat selection and use based on habitat availability using Manly's habitat-selection ratios and simultaneous Bonferroni confidence intervals (95 %). The mean home range size for coyotes was larger (12.2 ± 1.74 km 2) than for gray boxes (5.3 ± 0.67 km 2); the interspecific mean overlap was 42 % (moderate). Of these two canids, just the gray fox showed a markedly selective habitat use. Our findings revealed a moderate overlap between the home ranges of both canids, so spatial segregation did not occur. Although a differential habitat use was observed, explaining the coexistence between these two canids in the areas where they thrive, they tend to avoid agonistic interactions.

El coyote (Canis latrans) y la zorra gris (Urocyon cinereoargenteus) son especies abundantes y de amplia distribución en México y con poca información acerca de sus interacciones espaciales. Nuestros objetivos fueron, evaluar sus interacciones ecológicas espaciales, a través de la superposición de sus ámbitos hogareños y del uso de hábitat en los bosques templados de Durango, México. Esperábamos que su coexistencia fuera facilitada por la segregación de su nicho ecológico a nivel espacial, exhibida por la baja o ausente superposición entre sus ámbitos hogareños y/o por un marcado uso diferenciado del hábitat. Se colocaron radio-collares (VHF) en nueve individuos, cuatro coyotes (dos machos y dos hembras) y cinco zorras grises (hembras), monitoreándolos entre septiembre de 2017 y agosto de 2019. Estimamos el tamaño de ámbito hogareño y zona núcleo de cada individuo mediante el método del mínimo polígono convexo y determinamos la proporción del área de superposición entre ellos. Además, evaluamos el uso y selección de hábitat de tercer orden con respecto a su disponibilidad mediante el coeficiente de selección de hábitat de Manly e intervalos de confianza de Bonferroni (95 %). El tamaño promedio del ámbito hogareño fue mayor para coyotes (12.2 ± 1.74 km 2), que para las zorras grises (5.3 ± 0.67 km 2); mientras que, el promedio de la superposición interespecífica fue de 42 % (intermedio). De los dos cánidos, sólo la zorra gris presentó un marcado uso selectivo del hábitat. Nuestros resultados mostraron que los ámbitos hogareños de ambos cánidos presentaron una superposición intermedia, por lo que no se presentó segregación espacial. Aunque si existió un uso diferencial del hábitat, que explica la coexistencia entre estos dos cánidos en los sitios donde ocurren, ya que tienden a evitar interacciones antagónicas.

Resource partitioning, and especially dietary partitioning, is a mechanism that has been studied for several canid species as a means to understand competitive relationships and the ability of these species to coexist. Coyotes (Canis latrans) and gray foxes (Urocyon cinereoargenteus) are two canid species that are widely distributed, in Mexico, and they are sympatric throughout most of their distribution range. However, trophic dynamic and overlap between them have not been thoroughly studied. In order to better understand their ecological relationship and potential competitive interactions, we studied the trophic niche overlap between both canids in a temperate forest of Durango, Mexico. The results are based on the analysis of 540 coyote and 307 gray fox feces collected in 2018. Both species consumed a similar range of food items, but the coyote consumed large species while the gray fox did not. For both species, the most frequently consumed food categories throughout the year and...

Sympatric species reduce competitive interactions by segregating their ecological niche as a strategy that promotes coexistence. Two main dimensions in which niche differentiation occurs are spatial and temporal axes. Thus, describing the spatiotemporal patterns of sympatric species help us better grasp how species coexist. In Mexico, coyotes (Canis latrans) and gray foxes (Urocyon cinereoargenteus) are sympatric and widely distributed, and information about their temporal and spatiotemporal interactions is needed to explain their coexistence. As an approach to exploring the coexistence between these species in a temperate forest, we pose the following question: Is there temporal or spatiotemporal segregation between sympatric coyotes and gray foxes? We aimed to evaluate indicators of ecological niche segregation through two approaches: i) temporal partitioning, measuring the levels and overlap of daily activity patterns; and ii) spatiotemporal partitioning, through temporal co-occu...