Acid Phosphatase Activity in Freshwater Ecosystems of Western Cuba and its Relationship with Water Quality

Enzyme activity plays an important role in the functioning of aquatic ecosystems. It is sensitive to changes in environmental conditions such as pH, temperature, and nutrient concentration. The objective of this work was to determine the acid phosphatase activity (AcPA) in the Almendares and San Juan rivers (western Cuba) and its relationship with physicochemical and microbiological indicators. For this purpose, AcPA, temperature, pH, total dissolved solids, electrical conductivity, dissolved oxygen, concentration of nitrates, nitrites, ammonium, phosphates, total heterotrophs, enterococci, Escherichia coli, thermotolerant coliforms, chlorophyll a and chemical oxygen demand (COD) were determined at three sampling stations on the Almendares River and at three sampling stations on the San Juan River. In addition, the nutrient pollution index (NPI) and the N:P ratio were calculated. In both ecosystems, spatio-temporal variability was observed in the enzymatic activity. In the Almendares River (polluted ecosystem), AcPA was positively correlated with nitrate concentration and COD. While in the San Juan River (slightly contaminated ecosystem) the AcPA correlated negatively with the pH and NPI and positively with the concentrations of total heterotrophs, Escherichia coli, chlorophyll a and the N:P ratio. These results show the impact of anthropogenic pollution on AcPA in freshwater ecosystems with a tropical climate.

Condiciones de exposición y sensibilidad de la comunidad La Barra frente a los fenómenos meteorológicos extremos

El presente artículo analiza las condiciones de vulnerabilidad de una comunidad pesquera frente a los fenómenos meteorológicos extremos agravados por el cambio climático. Se utiliza la metodología cualitativa, con apoyo en métodos geográficos, y con base en un estudio de caso: la comunidad afrodescendiente La Barra, localizada en el litoral Pacífico colombiano, en la desembocadura del río San Juan. Al existir un acceso limitado a la comunidad por sus condiciones geográficas, además de los requisitos de bioseguridad establecidos por la pandemia de COVID-19, se realizan un análisis documental y mapas multitemporales, a partir de imágenes satelitales, para visualizar los cambios espaciales de la línea costera de La Barra durante los años 2001, 2011 y 2019. Asimismo, se realizan entrevistas a expertos académicos y pobladores de la comunidad. La vulnerabilidad es entendida desde la escuela de pensamiento de la ciencia del cambio climático y la investigación sobre adaptación. Se concluye que no solo depende de los estímulos climáticos, sino también de las condiciones racializadas y marginalizadas de poblaciones afro ubicadas en territorios rurales aislados. De tal manera, la naturaleza social y política de los fenómenos meteorológicos puede transformarlos en eventos catastróficos para poblaciones vulnerables. Abstract This article analyses the vulnerability conditions of a fishing community facing the extreme meteorological phenomena aggravated by climate change. The methodology is qualitative, supported by geographic methods, based on the case study of the “La Barra afro-descendant community”, located in the Colombian Pacific Coast, in the mouth of San Juan River. As there is limited access to the community due to its geographical conditions, besides the biosecurity requirements due to the COVID-19 pandemic, a documentary analysis, as well as multi-temporal maps based on satellite images, show the spatial changes on the coastline of La Barra, during the years 2001, 2011 and 2019. In addition to the above, interviews with academic experts and community residents are conducted. The term “vulnerability” is understood from the school of thought of climate change science and adaptation research. It is concluded that the vulnerability not only depends on climatic stimuli but also on the racialized and marginalized conditions of Afro populations located in isolated rural territories. In that way, the social and political nature of the meteorological phenomena could transform them in catastrophic events for vulnerable populations.

Development of a Culturally Anchored Qualitative Approach to Conduct and Analyze Focus Group Narratives Collected in Diné (Navajo) Communities to Understand the Impacts of the Gold King Mine Spill of 2015

The Gold King Mine Spill (Spill) occurred in August 2015 upstream from Silverton, Colorado and released three million gallons of contaminated water into the Animas River, a tributary to the San Juan River that flows across the Navajo Nation. Using principles of community-engaged research, the Gold King Mine Spill Diné Exposure Project co-developed a culturally anchored approach to conduct focus groups and analyze narratives collected in three Diné (Navajo) communities along the San Juan River within 9 months of the Spill. Focus group questions were designed to document the socio-cultural impacts of the Spill. This paper: (1) outlines the partnerships and approvals; (2) describes focus group design, training, data collection and analysis; and (3) reflects on the use of a culturally anchored approach in Indigenous, specifically Diné-centered research. Diné social and cultural etiquette and concepts of relationality were used to adapt standard (non-Indigenous) qualitative methods. Findings describe community perceptions of short-term impacts of the disaster, as well as past and present injustices, communication related to the Spill, and concerns of persistent threats to Diné lifeways. The culturally anchored approach was critical in fostering trust with Diné participants and aligned with the candor of the discussions.

Parallel Evolution of Allometric Trajectories of Trophic Morphology between Sympatric Morphs of Mesoamerican Astyanax (Characidae)

Parallel evolution of the body shape and trophic-related traits has been detected between sympatric pairs of lake-dwelling characin fishes in Mesoamerica. Here, we evaluated the variation in and the ontogenetic allometric trajectories of trophic morphology between sympatric Astyanax morphs (elongate and deep-body) in two geographic systems, Lake Catemaco (Mexico) and San Juan River basin (Nicaragua and Costa Rica). Using geometric morphometrics, we determined the shape variation and disparity in the premaxillary bone, and the patterns of allometric trajectories between morphs in each system. We found a higher differentiation and disparity in the premaxilla shape between morphs from San Juan River basin than between the Lake Catemaco ones. We found shared (parallel evolution) patterns of divergence between systems, which included allometric trajectories showing a positive correlation between the premaxilla shape and log centroid size, as well as trajectories being extended in the elongated-body morph (truncated in the deep-body morph). Regarding the unique patterns of divergence, we recovered parallel allometric trajectories between morphs from Lake Catemaco, while the San Juan River basin morphs showed divergent trajectories. Our results are congruent with the hypothesis that divergence in trophic morphology can be considered a triggering factor in the divergence in the genus Astyanax from Mesoamerica.

Susceptibilidad a la licuación de suelos y sedimentos en el valle Ullum-Zonda (31º30’ S-68º25’ O), Precordillera, Andes Centrales, Argentina

. The earthquakes of 1894, 1944, 1952 and 1977 occurred in the province of San Juan in central-wesern Argentina caused numerous processes of soils and sediment liquefaction, including those in the Ullum-Zonda valley. Historical records showed cracks, sand volcanoes, craters and differential settlements, which caused significant damage to housing and the agro-industrial sector of the region. In this work, we carried out a study of the susceptibility to liquefaction of soils and sedimentary deposits in the Ullum-Zonda valley. This was conducted using a methodology in which conditioning factors such as depth of the water table, historical records of liquefaction, potential seismogenic sources, origin, age and grain size of the soils and sedimentary deposits, among others, were evaluated and weighted. An iterative process of overlapping maps weighted the influence of the different factors in the assessment of susceptibility. Once the optimal combination was achieved, a final map with the zoning of soils and sediment susceptibility to liquefaction was obtained for the Ulum-Zonda Valley. The achieved zoning was related to a susceptibility index (SI), qualitatively classified as very high, high, moderate and low. The zone of very high susceptibility to liquefaction is located in the distal portion of the alluvial fan formed by the San Juan River in the Ullum-Zonda Valley, the areas of high to moderate susceptibility in the middle sector of the fan, and those of moderate to low susceptibility correspond to the proximal-middle sector of the fan. The main villages of the Ullum-Zonda valley, Ibáñez (head of the Ullum department) to the north of the San Juan River, Basilio Nievas (head of the Zonda department), to the south of the river, Tacú residential sector (located south of the Ullum dam) and the yacht clubs (located on the northeast periphery of the dam) are located in the areas of high to very high susceptibility, where the main conditioning factors are soil and sediments granulometry and the depth of the phreatic level.

Economic Valuation of Benefits in Freshwater Ecosystems: Complex Wetlands System Belonging to the San Juan River in the Magdalena Medio Region, Colombia

This paper identifies and assesses the economic value of the main natural benefits relating to the complex system of wetlands (CSW) belonging to the San Juan River in the Colombian Magdalena Medio. This is a region rich in biodiversity and natural resources, which in the past was hit by violence and the actions of different armed groups. Benefit estimation takes into account diverse monetary valuation techniques, such as market prices for direct wetland uses and the transfer of benefits, for the assessment of indirect use and non-use values. The results reveal that the most important values relate to ecotourism (60.1%) as a possible future use of the CSW, the benefit of preventing flooding (28.4%), and the biodiversity that inhabits the area (6.7%). All three values represent the total economic value of the CSW. This research also finds that the benefits of the ecosystems currently provided by the CSW exceed the opportunity cost, represented by the total conversion of the area to livestock. Lastly, the net present value (NPV) of 25 and 75 years, relating to the benefits of the CSW, exceeds the income from the conversion of land to livestock, revealing profitable investments in conservation and ecotourism projects.

Detrital sanidine 40Ar/39Ar dating confirms <2 Ma age of Crooked Ridge paleoriver and subsequent deep denudation of the southwestern Colorado Plateau

Crooked Ridge and White Mesa in northeastern Arizona (southwestern United States) preserve, as inverted topography, a 57-km-long abandoned alluvial system near the present drainage divide between the Colorado, San Juan, and Little Colorado Rivers. The pathway of this paleoriver, flowing southwest toward eastern Grand Canyon, has led to provocative alternative models for its potential importance in carving Grand Canyon. The ∼50-m-thick White Mesa alluvium is the only datable record of this paleoriver system. We present new 40Ar/39Ar sanidine dating that confirms a ca. 2 Ma maximum depositional age for White Mesa alluvium, supported by a large mode (n = 42) of dates from 2.06 to 1.76 Ma. Older grain modes show abundant 37–23 Ma grains mostly derived ultimately from the San Juan Mountains, as is also documented by rare volcanic and basement pebbles in the White Mesa alluvium. A tuff with an age of 1.07 ± 0.05 Ma is inset below, and hence provides a younger age bracket for the White Mesa alluvium. Newly dated remnant deposits on Black Mesa contain similar 37–23 Ma grains and exotic pebbles, plus a large mode (n = 71) of 9.052 ± 0.003 Ma sanidine. These deposits could be part of the White Mesa alluvium without any Pleistocene grains, but new detrital sanidine data from the upper Bidahochi Formation near Ganado, Arizona, have similar maximum depositional ages of 11.0–6.1 Ma and show similar 40–20 Ma San Juan Mountains–derived sanidine. Thus, we tentatively interpret the &lt;9 Ma Black Mesa deposit to be a remnant of an 11–6 Ma Bidahochi alluvial system derived from the now-eroded southwestern fringe of the San Juan Mountains. This alluvial fringe is the probable source for reworking of 40–20 Ma detrital sanidine and exotic clasts into Oligocene Chuska Sandstone, Miocene Bidahochi Formation, and ultimately into the &lt;2 Ma White Mesa alluvium. The &lt;2 Ma age of the White Mesa alluvium does not support models that the Crooked Ridge paleoriver originated as a late Oligocene to Miocene San Juan River that ultimately carved across the Kaibab uplift. Instead, we interpret the Crooked Ridge paleoriver as a 1.9–1.1 Ma tributary to the Little Colorado River, analogous to modern-day Moenkopi Wash. We reject the “young sediment in old paleovalley” hypothesis based on mapping, stratigraphic, and geomorphic constraints. Deep exhumation and beheading by tributaries of the San Juan and Colorado Rivers caused the Crooked Ridge paleotributary to be abandoned between 1.9 and 1.1 Ma. Thermochronologic data also provide no evidence for, and pose substantial difficulties with, the hypothesis for an earlier (Oligocene–Miocene) Colorado–San Juan paleoriver system that flowed along the Crooked Ridge pathway and carved across the Kaibab uplift.