Sensor calibration for dissolved gas is a critical and necessary step to ensure consistent sensor response over time and under different conditions. In this work, we describe a 3D printed device that facilitates the calibration of gas sensors. The device effectively maintained gas concentration in the solution for at least 2 h. Analytical curves were constructed in the pH range of 2 to 12, yielding determination coefficients surpassing 0.98. The chosen method proved suitable for the calibration of the sensors. Furthermore, using accurate and reliable reference sensors contributed to obtaining precise and trustworthy measurements. conditions work D h 12 098 0 98 0.98 Furthermore measurements 1 09 9 0.9 0.

Abstract Introduction: The Mar Muerto lagoon is an ecosystem characterized by high productivity upon which various inhabiting organisms depend. Additionally, it is a system susceptible to environmental impacts. Consequently, indices have been developed to determine the degree of disturbance caused by natural and/or anthropogenic factors. Objective: To assess the degree of disturbance in the Mar Muerto lagoon using a Biotic Integrity Index (BII) based on ichthyofauna. Methods: From December 2019 to March 2021, 12 sampling stations were established in the lagoon. The Biotic Integrity Index was developed by collecting data on hydrological variables (salinity, dissolved oxygen, pH, electrical conductivity, suspended solids, temperature, nitrites, nitrates, phosphates, and transparency) and classifying fish species based on their composition and richness. This was followed by a Water and Habitat Quality Index (WHQI) derived from the characterization and classification of sampling stations based on physicochemical variables. The correlation of the two indices allowed for the evaluation of the effectiveness of the BII. Results: 65 species were reported for the lagoon, with Lile gracilis, Oligoplites altus, Eucinostomus currani, and Gerres simillimus being the most frequently recorded. Only station 10 exhibited poor biotic integrity (BII = 26), while the rest displayed regular biotic integrity (BII = 30 - 44), with station nine presenting the highest calculated value (BII = 42). The assessment of the lagoon’s BII demonstrated an average biotic integrity considered “regular.” Conclusion: Through this study, the functionality of the modified BII for the Mar Muerto lagoon was verified, allowing for the evaluation of the present conservation status and comparison with previous studies.

Resumen Introducción: La laguna Mar Muerto es un ecosistema caracterizado por una gran productividad, de la cual dependen diversos organismos que la habitan; también es un sistema susceptible a impactos ambientales. Por lo anterior, se han desarrollado índices que permiten conocer el grado de alteración por causas naturales y/o antropogénicas. Objetivo: Evaluar el grado de perturbación de la laguna Mar Muerto, mediante un índice de integridad biótica (IBI) basado en la ictiofauna. Métodos: De diciembre 2019 a marzo 2021, se establecieron 12 estaciones de muestreo en la laguna. La elaboración del índice de integridad biótica fue a partir de la recopilación de datos de las variables hidrológicas (salinidad, NO2, NO3, PO4, pH, OD, T, CE, transparencia y SDT) y la clasificación de las especies ícticas según su composición y riqueza; seguido de un índice de calidad de agua y hábitat (ICAH), elaborado a partir de la caracterización y clasificación de las estaciones de muestreo en función de variables fisicoquímicas. La correlación de los dos índices permitió evaluar la efectividad del IBI. Resultados: 65 especies fueron reportadas para la laguna, de las cuales Lile gracilis, Oligoplites altus, Eucinostomus currani y Gerres simillimus se registraron con mayor frecuencia. Sólo la estación 10 presentó una integridad biótica pobre (IBI = 26), el resto presentó un IBI regular (IBI = 30 - 44), siendo la estación nueve la que presentó el valor máximo calculado (IBI = 42). La valoración del IBI de la laguna demostró que ésta presenta una integridad biótica promedio considerada “regular”. Conclusión: A través de este trabajo, se comprobó la funcionalidad del IBI modificado para la laguna Mar Muerto, permitiendo evaluar el grado de conservación presente y compararlo con trabajos previos.

Abstract Introduction: Reservoirs are conceived as a set of interactions in which physical, chemical, and biological instability determines changes in the density of planktonic communities. Objective: To evaluate the instability of phytoplankton and zooplankton, and their interactions with environmental factors in four tropical Andean reservoirs with different trophic status. Methods: Physical and chemical variables and phytoplankton and zooplankton densities were measured between 2010-2018 in the oligotrophic reservoirs Punchiná and San Lorenzo and between 2013 and 2015 in the hypereutrophic reservoir Porce II and in the eutrophic Porce III reservoir (total N = 248). The Factor Shaping Community Assemblages (FCA) was used to calculate environmental and biotic instability as well as their interaction. Results: High environmental and biological instability was observed in the studied reservoirs. Oxygen saturation, pH, total nitrogen, water temperature, nitrites, total phosphorus (only for zooplankton), and total solids were the abiotic variables with the greatest contribution to planktonic instability, regardless of trophic state. Particularly, Cryptomonas sp., Aulacoseira sp., Cyclotella sp., Dinobryon sp., Nephrocytium sp., Tetraëdron caudatum and Oscillatoria sp. had the greatest influence on the instability of various rotifer taxa and some copepods. Conclusions: Regardless of trophic state, pH dynamics, nutrients availability, amount of suspended solids and the availability of gases, such as dissolved oxygen, mainly determined the instability of phytoplankton and to a lesser extent that of zooplankton. In the oligotrophic reservoirs, zooplankton instability was mainly influenced by highly palatable algae with no toxicity, and in reservoirs highly enriched, the instability was influenced by algae with low nutritional quality and difficult to ingest and manipulate.

Resumen Introducción: los embalses deben ser concebidos como un conjunto de interacciones, donde la inestabilidad física, química y biológica determinan cambios en la densidad de las comunidades planctónicas. Objetivo: Evaluar la inestabilidad del fitoplancton y zooplancton y su interacción con factores ambientales en cuatro embalses tropicales andinos con diferente estado trófico. Métodos: Se analizaron datos de variables físicas y químicas y de las densidades del fitoplancton y del zooplancton, medidas entre 2010-2018, en los embalses oligotróficos Punchiná y San Lorenzo y, entre 2013 y 2015, en el embalse hipereutrófico Porce II y en el embalse eutrófico Porce III (total N = 248). Se empleó el Factor Shaping Community Assemblages (FCA), para calcular la inestabilidad biótica y ambiental y la interacción entre estas. Resultados: En los embalses estudiados hubo una alta inestabilidad ambiental y biológica. El pH, la saturación de oxígeno, el nitrógeno total, la temperatura del agua, los nitritos, el fósforo total (solo para el zooplancton) y los sólidos totales, son las variables abióticas con mayor aporte a la inestabilidad planctónica, independientemente del estado trófico. Particularmente, Cryptomonas sp., Aulacoseira sp., Cyclotella sp., Dinobryon sp., Nephrocytium sp., Tetraëdron caudatum y Oscillatoria sp., tuvieron mayor influencia sobre la inestabilidad de diferentes taxones de rotíferos y de algunos copépodos. Conclusión: Independiente del estado trófico, la dinámica del pH, la disponibilidad de nutrientes, la cantidad de sólidos suspendidos y la disponibilidad de gases como el oxígeno disuelto determinaron principalmente la inestabilidad del fitoplancton, y en menor medida la del zooplancton. En los embalses oligotróficos la inestabilidad del zooplancton es influenciada principalmente por algas altamente apetecibles con toxicidad nula, y en embalses altamente enriquecidos la inestabilidad fue influenciada por algas con baja calidad nutricional y de difícil ingestión y manipulación.

Abstract Introduction: The brackish lagoons are ecosystems with great diversity and possibilities for human use. Therefore, the knowledge about phytoplankton needs to be improved to understand its real impact. Objective: To relate the Mandinga’s Lagoon phytoplankton to the limnological conditions during the dry and wet seasons. Methods: The material was collected in three stations: Isla Conchas (ICO), Mandinga Chica (MCH) and Isla del Amor (IA) during the dry (March 2018) and wet (September 2017 and 2018) seasons. The limnological analysis included ten abiotic variables, and the phytoplankton was analyzed by the Utermöhl method. Data was analyzed with the Shannon index (H') and Canonical Correspondence Analysis (CCA). Results: 136 species were identified: 68.4 % Heterokontophyta, 22.8 % Dinoflagellata, and 5.9 % Cyanobacteria; with 40 euryhaline and 96 stenohaline. The most abundant species were: Bacillaria paxillifera, Chaetoceros compressus, Coscinodiscus rothii, and Chaetoceros atlanticus. The highest abundance was in ICO (dry) and the lowest in MCH (wet), with 307 x 103 and 76 x 103 cells/ml, respectively; the H' ranged from 1.31 to 0.70 bits/ind. The CCA showed a relationship between salinity and dissolved oxygen with C. rothii and Ceratoneis closterium. The phosphates were associated with B. paxillifera, C. atlanticus, and Podosira stelligera. The nitrate, water temperature and pH were related to Tripos hircus, T. furca, Diploneis bombus, and Merismopedia elegans. In contrast, Skeletonema costatum, Cocconeis scutelum, and Nitzschia bicapitata did not correlate with the limnological variables. Conclusions: The Mandinga’s Lagoon is a shallow, euryhaline and well-oxygenated ecosystem. The dominance of diatoms and dinoflagellates was evidenced by their ability to survive in different salinities and temperatures. It is recommended monitor phytoplankton, in particular Microcystis wesenbergii, B. quinquecornis, Pseudo-nitzschia cf. pungens, and P. cf. pseudodelicatissima as they are harmful algae.

Resumen Introducción: Las lagunas salobres son ecosistemas de alta diversidad y con posibilidades para uso humano. Por lo que es necesario mejorar el conocimiento del fitoplancton para entender su impacto real. Objetivo: Relacionar el fitoplancton de la Laguna Mandinga con las condiciones limnológicas durante épocas de secas y lluvias. Métodos: El material se recolectó en tres estaciones: Isla Conchas (ICO), Mandinga Chica (MCH) e Isla del Amor (IA) en secas (marzo 2018) y lluvias (septiembre 2017 y 2018). El análisis limnológico incluyó diez variables abióticas, además del fitoplancton mediante el método de Utermöhl. Los datos fueron analizados por el índice de Shannon (H') y Correspondencia Canónica (ACC). Resultados: Análisis de 136 especies; 68.4 % Heterokontophyta, 22.8 % Dinoflagellata, 5.9 % Cyanobacteria; con 40 eurihalinas y 96 estenohalinas. Las especies más abundantes fueron: Bacillaria paxillifera, Chaetoceros compressus, Coscinodiscus rothii y Chaetoceros atlanticus. La mayor abundancia se registró en ICO (secas) y la menor en MCH (lluvias) con 307 x 103 y 76 x 103 cell/ml, respectivamente. El H' osciló entre 1.31 y 0.70 bits/ind. El CCA mostró una relación entre salinidad y oxígeno disuelto con C. rothii y Ceratoneis closterium. Los fosfatos se asociaron con B. paxillifera, C. atlanticus y Podosira stelligera. Los nitratos, temperatura y pH se correlacionaron con Tripos hircus, T. furca, Diploneis bombus y Merismopedia elegans. Mientras, Skeletonema costatum, Cocconeis scutelum y Nitzschia bicapitata no presentaron correlación con las variables limnológicas. Conclusiones: La Laguna Mandinga es un ecosistema somero, eurihalino y bien oxigenado. La dominancia de diatomeas y dinoflagelados se evidenció por su capacidad para sobrevivir en diferentes concentraciones de salinidad y temperatura. Sugerimos monitorear al fitoplancton por la presencia de Microcystis wesenbergii, B. quinquecornis, Pseudo-nitzschia cf. pungens y P. cf. pseudodelicatissima ya que pueden formar proliferaciones dañinas.

Summary: The municipality of Medellín, Veracruz, México has a type A landfill, whose operation level has recently increased due to landfill closure in the city of Veracruz. The objective of this study is to analyze and evaluate the quality of groundwater surrounding the landfill of the municipality of Medellín., such as hydrogen potential (pH), electrical conductivity (EC), turbidity (T), chemical oxygen demand (COD), total phosphorus (TP), nitrates (NO3 -), total dissolved solids (TDS) and heavy metals Lead (Pb), cadmium (Cd) and copper (Cu) in seven groundwater wells near the landfill during the “north” and dry season. The physicochemical water results from the seven wells analyzed were within the maximum permissible limits of Mexican regulations: turbidity values exceeded international regulations and four wells were found contaminated according to COD levels. The concentrations of Pb and Cd in both seasons were higher than the maximum permissible limits for human consumption in accordance with national and international regulations. Therefore, the results indicated the negative influence of the landfill on groundwater quality.

Resumen: Los rellenos sanitarios se han vuelto una fuente de contaminación de aguas superficiales y subterráneas, debido a la generación de lixiviados que pueden llegar hasta los cuerpos de agua con efectos adversos al ambiente. El municipio de Medellín, Veracruz, México; cuenta con un relleno sanitario tipo A cuyo nivel de operación se ha incrementado recientemente debido a la clausura del relleno sanitario de la ciudad de Veracruz. El objetivo del presente estudio fue analizar la calidad del agua subterránea aledaña al relleno sanitario del municipio de Medellín. Se evaluaron potencial de hidrógeno (pH), conductividad eléctrica (CE), turbidez (T), Demanda Química de Oxigeno (DQO), Fósforo Total (PT), Nitratos, (NO3 -), Sólidos Disueltos Totales (SDT) y metales pesados Plomo (Pb), Cadmio (Cd) y Cobre (Cu) en 7 pozos de agua subterránea próximos al relleno sanitario durante la temporada de “nortes” y estiaje. Los resultados fisicoquímicos del agua de los 7 pozos analizados se encontraron dentro de los límites máximos permisibles de la normatividad mexicana; los valores de turbidez superaron la normatividad internacional y 4 pozos mostraron estar contaminados de acuerdo a los niveles de DQO. Las concentraciones de Pb y Cd en ambas temporadas se encontraron superiores a los límites máximos permisibles para consumo humano de acuerdo con la normatividad nacional e internacional. Los resultados indicaron la influencia negativa del relleno sanitario en la calidad del agua subterránea.

Abstract (Objective) This study aimed to evaluate the short-term response of four different odor control measures in a homogenization tank of a university Wastewater Treatment Plant (WWTP). (Methodology) The following were implemented: aeration, adding lime, adding iron sulfate, and adding the commercial product BiOWiSH® Odor over four hydraulic retention times. The effluent and the unit were monitored during each period, using a baseline to compare the measures. Hydrogen potential, oxidation-reduction potential, dissolved oxygen, and dissolved sulfide concentration were measured in triplicate every 30 minutes. An odor perception survey was administered to WWTP visitors to evaluate intensity, offensiveness, and character (15 surveys per monitoring period). Differences were determined between control measures and the baseline using Student’s t-tests (quantitative data) and Mood’s median tests (qualitative data). Minitab 2019 was used with a 95% confidence level. (Results) All control measures significantly reduced the dissolved sulfide concentration in the unit. Aeration prevented oxygen depletion, reductive regime, and acid fermentation, which favored the oxidation of odorants. Aeration was also the only studied control measure that reduced odor intensity and offensiveness. (Conclusions) Applying aeration changed unit behavior and odor perception, which confirms its effectiveness, while adding iron sulfate, lime, and BiOWiSH® did not significantly change odor perception.

Resumen (Objetivo) El objetivo de este estudio fue evaluar la respuesta, a corto plazo, de cuatro diferentes medidas de control de olores en un tanque de homogeneización de una PTAR universitaria. (Metodología) Se aplicaron la aireación, adición de cal, adición de sulfato de hierro y adición del producto comercial BiOWiSH® Odor, durante cuatro tiempos de retención hidráulica. Se monitoreó el afluente y la unidad en cada periodo, utilizando una línea base como comparación de las medidas. Se midió por triplicado, cada 30 min, el potencial de hidrógeno, potencial de oxidación-reducción, oxígeno disuelto y la concentración de sulfuro disuelto. Se pasó una encuesta de percepción de olores a visitantes de la PTAR, con el propósito de evaluar intensidad, ofensividad y carácter (en total, 15 encuestas por periodo de monitoreo). Se determinaron diferencias entre las medidas de control y la línea base, con pruebas t-student (datos cuantitativos) y medianas de Mood (datos cualitativos). Se usó Minitab2019 y un límite de confianza de 95 %. (Resultados) Todas las medidas de control disminuyeron significativamente la concentración de sulfuro disuelto en la unidad. La aireación evitó el agotamiento de oxígeno, el régimen reductivo y la fermentación ácida, favoreciendo la oxidación de odorantes; además, fue la única medida de control estudiada que generó una reducción en la intensidad y ofensividad del olor. (Conclusiones) La aplicación de aireación generó un cambio en el comportamiento de la unidad y la percepción de olor, hecho que confirma su efectividad. La adición de sulfato de hierro, cal y BiOWiSH® no produjeron modificaciones significativas en la percepción de olor.

Resumo (Objetivo) O objetivo deste estudo foi avaliar a res em curto prazo de quatro diferentes medidas de controle de odores em um tanque de homogeneização de uma ETE universitária. (Metodologia) Foram aplicadas aeração, adição de cal, adição de sulfato de ferro e adição do produto comercial BiOWiSH® Odor durante quatro tempos de detenção hidráulica. O afluente e a unidade foram monitorados em cada período, utilizando uma linha de base como comparação das medições. Foram medidos em triplicata a cada 30 minutos o potencial de hidrogênio, o potencial de oxidação-redução, o oxigênio dissolvido e a concentração de sulfeto dissolvido. Foi aplicado um questionário de percepção de odores aos visitantes da ETE, com o objetivo de avaliar a intensidade, a ofensividade eo carácter (no total, 15 questionários por período de monitorização). Foram determinadas diferenças entre as medidas de controle e a linha de base, com testes t-Student (dados quantitativos) e da mediana de Mood (dados qualitativos). Foram utilizados Minitab2019 e limite de confiança de 95%. (Resultados) Todas as medidas de controle diminuíram significativamente a concentração de sulfeto dissolvido na unidade. A aeração evitou o esgotamento do oxigênio, o regime redutor e a fermentação ácida, favorecendo a oxidação dos odorantes; além disso, foi a única medida de controle estudada que gerou redução na intensidade em a ofensividade do odor. (Conclusões) A aplicação da aeração gerou uma mudança no comportamento da unidade e na percepção do odor, fato que confirma sua eficácia. A adição de sulfato de ferro, cal e BiOWiSH® não produziu modificações significativas na percepção do odor.

ABSTRACT The present study aimed to evaluate the ecology considering distribution, abundance, population structure, and fecundity of the marine diplostraceans Penilia avirostris and Pseudevadne tergestina in the Veracruz Reef System National Park, southwest Gulf of Mexico. Surface samples were collected with a 300 μm mesh plankton net at 26 sampling sites in June, August, October (2011), May (2012) and June (2013). Temperature, salinity, and dissolved oxygen were measured in situ. The temperature range was 26.53 ± 0.41 and 29.29 ± 0.27°C, salinity between 33.43 ± 0.49 and 35.91 ± 0.09, and dissolved oxygen between 2.92 ± 0.08 and 6.56 ± 0.08 mg L-1. P. avirostris and P. tergestina presented the highest density, with 2200 ind 100 m-3 in June and 5980 ind 100 m-3 in October, respectively. Four stages were determined in P. avirostris. In P. tergestina, there were five instars, with males in August and October. The size of parthenogenic females of P. avirostris was 773.4 ± 20.08 μm. In P. tergestina, it was 637.6 ± 49.28 μm. The number of embryos in P. avirostris was 2 to 7, and in P. tergestina, 2 to 8 embryos. The correlations between body length and the number of embryos in both species were statistically significant under the potential model (r > 0.68 for both species, P < 0.001). The transects with the highest abundance were the northern and the southern zones because they are far from the influence of the Jamapa River. The density of these crustaceans is related to optimal temperature, salinity, and dissolved oxygen values. The low proportions obtained from gamogenic individuals of P. avirostris and P. tergestina suggest that in tropical and subtropical regions, gamogenesis is not crucial for the life cycle of these organisms.

Abstract Common duckweeds are flowering plants of the family Araceae, comprising the smallest angiosperms of the plant kingdom, a species of aquatic algae of universal distribution, found on the surface of freshwater bodies, mainly in puddles, swamps, lakes, and calm rivers. Recently, different research has been carried out on its potential and usefulness. Due to its nutritional composition, protein contribution, high fiber content and low fat and carbohydrate content, it would be an adequate input to generate products of high nutritional value, characteristics that make it interesting compared to other species. It is used as a complement to commercial diets in a wide variety of animals such as birds, ruminants, non-ruminants, crustaceans, and fish, reducing feed costs by up to 50 %. Likewise, used in remediation processes of a wide range of chemical contaminants with a high elimination rate, they can absorb some dissolved substances and provide oxygen through photosynthesis. It has been indicated that they are low cost of construction, maintenance, easy to operate, have a wide tolerance to growing conditions, are generally easy to harvest, and do not compete with farmland. In the environmental field, it is important to find alternative and innovative raw materials, even without the need to use growth media or fertilizers, however, their acceptance as a food source needs extensive research regarding their nutritional value, large-scale yield, economic market supply and analysis of antinutritive components for human food.

Resumen Las lentejas de agua son plantas con flores de la familia Aráceas, comprenden las angiospermas más pequeñas del reino vegetal, una especie de algas acuáticas de distribución universal, se encuentran en la superficie de los cuerpos de agua dulce principalmente en charcos, ciénagas, lagos y ríos calmados. Recientemente, se han llevado a cabo diferentes investigaciones sobre su potencial y utilidad. Por su composición nutricional, aporte de proteína, alto contenido de fibra y bajo contenido de grasas y carbohidratos, resultaría ser un insumo adecuado para generar productos de alto valor nutricional, características que la hacen interesante frente a otras especies. Se emplea como complemento a dietas comerciales en una gran variedad animales como aves, rumiantes, no rumiantes, crustáceos y peces, reduciendo hasta un 50 % los costos por alimentación. Así mismo, usada en procesos de remediación de una amplia gama de contaminantes químicos con alta tasa de eliminación, pueden absorber algunas sustancias disueltas y brindar oxígeno mediante la fotosíntesis. Se ha indicado bajo costo de construcción, mantenimiento, fáciles de operar, poseen amplia tolerancia a condiciones de crecimiento, facilidad general de cosecha y no compiten con las tierras de cultivo. En el ámbito ambiental es importante encontrar materias primas alternativas e innovadoras, incluso sin la necesidad de utilizar medios de crecimiento o fertilizantes, sin embargo, su aceptación como fuente de alimento necesita investigaciones exhaustivas con respecto a su valor nutritivo, rendimiento a gran escala, suministro de mercado económico y análisis de componentes antinutritivos para la alimentación humana.

Resumen Marca-Zevallos, M. J.; W. Galiano, R. Chevarría, G. Sebastián, K. Huamani, J. A. Ochoa & J. Mendoza. 2024. Influencia de factores ambientales en la composición de macrofitas acuáticas en lagos (cochas) de la Amazonía sur del Perú. Darwiniana, nueva serie 12(1): 170-191. La riqueza y composición de macrofitas acuáticas está influenciada por la morfometría y las condiciones físicas y químicas del cuerpo acuático. Sin embargo, el efecto de estos factores en las comunidades vegetales no ha sido corroborado para los lagos con forma de herradura o comúnmente llamados como “cochas” de la Amazonía peruana. En el presente estudio se evaluó 10 cochas desconectadas del curso principal del río en la Amazonia Sur del Perú para conocer 1) la riqueza de macrofitas acuáticas, 2) su forma de vida y 3) la influencia del área y la profundidad del cuerpo acuático, la transparencia, pH, oxígeno disuelto, sólidos totales disueltos y la temperatura del agua en la riqueza y en los cambios de la composición de especies. Se reportó 68 taxones, donde Cyperaceae y Poaceae fueron las familias más diversas. Además, las formas de vida predominantes fueron las emergentes (47,1 %) y anfibias (36,8 %). Finalmente, se encontró que cochas con mayor área, pH y oxígeno disuelto, a la vez, con menor temperatura, abrigan una mayor riqueza de especies y favorecen el establecimiento de especies estrictamente acuáticas, indicando que existe un recambio de especies a lo largo de la gradiente conformada por la asociación de estas variables. Estos resultados demuestran que la Amazonía sur del Perú posee una importante riqueza de macrofitas acuáticas que está asociada al área, pH, oxígeno disuelto y temperatura del cuerpo acuático.

Abstract. Marca-Zevallos, M. J.; W. Galiano, R. Chevarría, G. Sebastián, K. Huamani, J. A. Ochoa & J. Mendoza. 2024. Influence of environmental factors on aquatic macrophytes composition in oxbow lakes in the Southern Peruvian Amazon. Darwiniana, nueva serie 12(1): 170-191. Species richness and composition of aquatic macrophytes are influenced by morphometry and physical and chemical conditions of the aquatic body. However, the influence of these variables has not been confirmed for oxbow lakes or commonly called “cochas” in the Peruvian Amazon. 10 cochas disconnected from the main course of the river were investigated in the Southern Amazon of Peru to know 1) the species richness of aquatic macrophytes, 2) their life form, and 3) the influence of area and depth of the water body and, transparency, pH, dissolved oxygen, total dissolved solids, and temperature of the water on species richness and composition changes of aquatic macrophytes. 68 taxa were reported, where Cyperaceae and Poaceae were the most diverse families. Moreover, he predominant life forms were emergent (47,1 %) and amphibian (36,8 %). Finally, cochas with greater area, pH, and dissolved oxygen, at the same time, with lower temperature, shelter a higher species richness and favour strictly aquatic species establishment, indicating that exists a species turnover along the conformed gradient by the association of these variables. These results demonstrate that southern Amazon of Peru has an important aquatic macrophytes richness that is associated with area, pH, dissolved oxygen, and temperature of the aquatic body.

ABSTRACT The semi-permanent coastal upwelling system within the Humboldt Current System (HCS) off northern Chile provides nutrient-rich, oxygen-poor water to the euphotic zone that contributes to high levels of primary production and restricts the vertical distribution of most zooplankton species according to their tolerance to hypoxia within this highly heterogeneous environment. The day/night vertical distributions of two calanoid copepods, Eucalanus inermis and Nannocalanus minor, were studied concerning the presence of oxygen-poor water associated with the Oxygen minimum zone (OMZ) at a coastal and an offshore station off northern Chile (∼20°S), by stratified sampling from the surface to a depth of 600 m. At the coastal station, most of the population of both species remained above the OMZ, whereas at the offshore station, most populations remained at the edge of the OMZ. Both species exhibited reverse diel vertical migration between day and night and were positively correlated with dissolved oxygen and chlorophyll-a, suggesting that both species may prefer oxygenated waters and avoid the OMZ. However, E. inermis and N. minor exhibited distinct behavior, with E. inermis displaying significant variations among stations and strata and N. minor showing differences only among strata, particularly in the upper strata where it was more aggregated. The results helped us understand the behavior and distribution of zooplankton related to OMZ and how they may change as ocean temperature increases worldwide.

Abstract The genus Isonychia groups mayflies with large nymphs present in lotic ecosystems. This genus has a very wide distribution, despite of this, in Mexico the records are very scarce and these do not refer to the environmental characteristics of the sites where they were found. The objective of this work is to report for the first time the genus Isonychia in Durango state, as well as to characterize some physicochemical parameters of water associated with its distribution. A total of 19 Isonychia nymphs, which probably correspond to the species I. sicca, were recorded in seven sites within the Nazas River basin. This extends the distribution range of the genus Isonychia for Mexico. The specimens were recorded in environments with moderate current speed and an acceptable water quality compared to other riparian systems, in terms of dissolved oxygen, electrical conductivity, total dissolved solids, pH, temperature and ammonium.

Resumen El género Isonychia agrupa efímeras con ninfas de gran tamaño presentes en ecosistemas lóticos. Este género tiene una distribución muy amplia, a pesar de ello, en México los registros son muy escasos y éstas no refieren las características ambientales de los sitios donde fueron encontradas. El objetivo de este trabajo es reportar por primera vez el género Isonychia en el estado de Durango, así como caracterizar algunos parámetros fisicoquímicos del agua asociados a su distribución. Se registraron 19 ninfas de Isonychia, que probablemente corresponden a la especie I. sicca, en siete sitios dentro de la cuenca del río Nazas. Esto amplía el rango de distribución del género Isonychia para México. Los ejemplares se registraron en ambientes con velocidad de corriente moderada y una calidad del agua aceptable en comparación con otros sistemas riparios, en términos de oxígeno disuelto, conductividad eléctrica, sólidos disueltos totales, pH, temperatura y amonio.

RESUMEN Antecedentes. La aplicación de simbióticos en acuicultura tiene potencial como promotor del crecimiento, como sustituto a los antibióticos, para mejorar la calidad del agua y la digestibilidad de nutrientes. Objetivos. Evaluar el efecto de los simbióticos sobre el crecimiento y la dinámica bacteriana del contenido intestinal de pacú (Piaractus mesopotamicus) y del agua de cultivo, en sistemas acuícolas de recirculación (SAR). Métodos. Se realizaron cultivos de 87 días con P. mesopotamicus en SAR bajo tres condiciones:1) simbiótico mezclado con el alimento, 2) simbiótico activado agregado directamente al agua, y 3) tratamiento control (sin simbiótico). Se evaluaron la calidad del agua, las poblaciones bacterianas en el agua y en el contenido intestinal, y el crecimiento midiendo parámetros morfofisiológicos, Resultados. Pacú presentó crecimiento isométrico y no se encontraron diferencias significativas entre los tratamientos en la tasa de conversión alimenticia, en el factor de condición de Fulton, pH, oxígeno disuelto ni en la eliminación de amonio en el biofiltro. Sin embargo, cuando el simbiótico se mezcló con el alimento, pacú mostró una alta tolerancia al amonio (0.62 mg/L) en cultivos de 87 días. Además, los pesos finales y la tasa de crecimiento específico fueron significativamente mayores (5.4 g y 0.0321 días-1, respectivamente) con probiótico en el alimento. Basado en análisis de secuencias del gen 16S rRNA, se identificaron siete poblaciones bacterianas en el contenido intestinal de pacú y en el agua de cultivo: Microbacterium, Variovorax, Prosthecobacter, Bacillus, Asaccharospora, Turicibacter sanguinis y Limnohabitans planktonicus. Conclusiones. Los simbióticos promueven un mayor crecimiento y tolerancia al amonio en P. mesopotamicus. Los resultados obtenidos marcan un referente en el estudio de la relación longitud-peso de pacú, en la capacidad del biofiltro para eliminar el amonio y en la relación de los probióticos con la dinámica bacteriana en el agua y en el contenido intestinal durante cultivos en SAR.

ABSTRACT Background. The application of symbiotics in aquaculture holds potential as a growth promoter and substitute for antibiotics, while also improving water quality and nutrient digestibility. Goals. This study aimed to assess the impact of symbiotics on the growth and bacterial populations dynamics of the intestinal contents of pacú (Piaractus mesopotamicus) cultured in recirculating aquaculture systems (RAS). Methods. 87-day cultures of P. mesopotamicus were conducted in RAS under three conditions: 1) food-mixed with symbiotic, 2) activated symbiotic directly added to the water and 3) control treatment (without symbiotic). The evaluation included growth parameters, water quality, and bacterial populations in both the water and intestinal content. Results. Under these conditions pacú showed isometric growth, and no significant differences were found between treatments for food conversion ratio and Fulton condition factor. Regarding the performance of the recirculating system, there were no differences in pH, dissolved oxygen and ammonia removal by the biofilter. However, pacú exhibited high ammonia tolerance (0.62 mg/L) in the 87-day cultures when the symbiotic was mixed with the food. Additionally, final weights and specific growth rate were significantly higher (5.4 g and 0.0321 days-1, respectively) compared to the other conditions. Based on 16S rRNA gene sequence analysis, seven bacterial populations were identified in the intestinal content of pacú and in the culture water: Microbacterium, Variovorax, Prosthecobacter, Bacillus, Asaccharospora, Turicibacter sanguinis, and Limnohabitans planktonicus. Conclusions. symbiotics mixed with food, significantly promoted the growth of P. mesopotamicus and enhanced ammonia tolerance in RAS. These results set a benchmark in the study of the length-weight relationship of P. mesopotamicus, the biofilter´s capability to remove ammonia, and the relationship between symbiotics and bacterial dynamics in the water and intestinal content during pacú crops in RAS.

Abstract 19. This study reports an episode of fish mortality occurred in the Garupá and Pindapoy Grande streams, near the confluence with the Paraná River (Garupá, Argentina). Dead and moribund fish of various species were observed floating on the water surface. Environmental parameters measured were temperature 5 °C, water temperature 15.1 (±0.6) °C, dissolved oxygen 8.7 (±1.2) ppm, pH 7.5 (±0.2), electrical conductivity 67.6 (± 8.8) mS cm-1 and mean depth of 1.7 (±1.0) m. Macroscopic examination of moribund fish revealed corneal opacity, whitish tegument, increased gill mucus, and whitish areas on gill filaments. Microscopic analysis of gills revealed severe generalized epithelial hyperplasia, lamellar fusion, congestion, and inflammatory infiltrate, particularly lymphocytes and eosinophilic granular cells. In addition, microscopic examination allowed the identification of the following ectoparasites found in gills and tegument: Chilodonella, Ichthyophthirius, Dactylogyridae and Trichodinidae, representing 98%, 1.2%, 0.6% and 0.2%, respectively. This study constitutes a novel record of wild fish mortality associated with extreme environmental conditions and parasitosis. Furthermore, our findings are significant as there are no prior reports in Argentina of epizootic cases linked to Chilodonella sp. infection in wild or farmed fish populations, being the first report of chilodonelliasis for this region.

Resumen 23. Este estudio reporta un episodio de mortandad de peces ocurrido en los arroyos Garupá y Pindapoy Grande, cerca de la confluencia con el río Paraná (Garupá, Argentina). En este tramo se encontraron flotando en la superficie del agua, peces moribundos y muertos de diferentes especies. Los parámetros medidos fueron: temperatura ambiental 5 °C, temperatura del agua 15,1 (±0,6) °C, oxígeno disuelto 8,7 (±1,2) ppm, 24. pH 7,5 (±0,2), conductividad 67,6 (± 8,8) mS cm-1 y profundidad media de 1,7 (±1,0) m. En el examen macroscópico de peces moribundos se observó opacidad corneal, tegumento blanquecino, aumento de moco branquial y áreas blanquecinas en los filamentos branquiales. El análisis microscópico de las branquias reveló hiperplasia epitelial generalizada grave, fusión laminar, congestión e infiltrado inflamatorio, particularmente linfocitos y células granulares eosinófilas. Además, el examen microscópico permitió identificar los siguientes ectoparásitos encontrados en piel y branquias: Chilodonella, Ichthyophthirius, Dactylogyridae y Trichodinidae, que representó el 98%; 1,2%; 0,6% y 0,2%, respectivamente. El presente estudio es un nuevo registro de mortandad de peces silvestres relacionada con condiciones ambientales extremas y parasitosis. Además, nuestro hallazgo aporta información valiosa, ya que en Argentina no existen registros de casos epizoóticos asociados a infección por Chilodonella sp. en poblaciones de peces silvestres o de criaderos, siendo el primer reporte de quilodonelliasis para esta región.

Leachate from a composting plant was characterized and applied as a biofertilizer in lettuce crops. Characteristics of untreated (UE) and anaerobically treated (TE) leachate samples were compared. The pH of TE (8.2) increased in relation to the UE (5.2) due to an increase in ammonia nitrogen in TE (1197 mg L-1) compared to UE (859 mg L-1). Anaerobic treatment was efficient in the removal of organic matter from the leachate, evaluated by the decrease of dissolved organic carbon, biochemical oxygen demand, total organic carbon and total solids. K presented the highest concentration (1743 mg L-1) in TE, followed by Mg (135 mg L-1). Cd, Pb and Cr were present at low concentrations in the samples, 0.047, 0.206 and 0.081 mg L-1, respectively. Salmonella, thermotolerant coliforms and viable helminth eggs were not present in TE, which was applied as a biofertilizer in a lettuce crop and compared to mineral fertilization based on fresh matter and dry matter production. Lettuce production using TE was statistically equivalent to mineral fertilization. Toxic metals were not detected in the lettuce shoots. It was concluded that the anaerobically treated leachate from the composting company has the potential to be used as a biofertilizer. crops (UE (TE 8.2 82 8 2 (8.2 5.2 52 5 (5.2 1197 (119 L1 L 1 L-1 859 (85 L1. . demand solids 1743 (174 135 (13 Cd 0047 0 047 0.047 0206 206 0.20 0081 081 0.08 L1, 1, respectively Salmonella shoots 8. (8. 5. (5. 119 (11 L- 85 (8 174 (17 13 (1 004 04 0.04 020 20 0.2 008 08 0.0 (5 11 ( 17 00 02 0.

Resumo Objetivo O objetivo deste estudo foi avaliar como a diversidade, dominância e raridade da comunidade fitoplanctônica são influenciadas por diferentes condições ambientais locais em lagos urbanos. Nós esperamos que a riqueza será influenciada negativamente em lagos com maiores concentrações de nutrientes e maior turbidez, enquanto a abundância será influenciada positivamente. Assim, haverá uma maior dominância de poucas espécies e menor raridade em lagos com essas condições, sendo esperado o contrário em lagos com menores concentrações de nutrientes e menor turbidez. Métodos As amostras do fitoplâncton e das variáveis abióticas foram coletadas em quatorze lagos distribuídos no município de Goiânia, Goiás, Brasil, durante um período chuvoso. Resultados Foi possível identificar uma heterogeneidade ambiental entre os lagos. Nós identificamos uma separação dos lagos em função da riqueza e densidade fitoplanctônica, especialmente devido à contribuição de algas verdes, desmídias e cianobactérias. A maioria dos lagos apresentou altos valores de diversidade e equitabilidade, com predominância de táxons raros e poucas espécies dominantes. As principais variáveis que estiveram relacionadas com o fitoplâncton, foram a temperatura da água, oxigênio dissolvido, turbidez e as concentrações de nutrientes. Conclusões Portanto, o estudo da diversidade, dominância e raridade baseada na riqueza e abundância fitoplanctônica e a sua relação com as diferentes condições ambientais locais pode ser um importante modelo na avaliação da qualidade da água em lagos urbanos. urbanos positivamente Assim Goiânia Goiás Brasil chuvoso verdes cianobactérias equitabilidade dominantes dissolvido Portanto

Abstract Aim The aim of this study was to evaluate how phytoplankton community diversity, dominance, and rarity are influenced by different local environmental conditions in urban lakes. We expect that richness will be negatively influenced in lakes with higher nutrient concentrations and high turbidity, while abundance will be positively influenced. Thus, lakes with these conditions will have greater dominance of a few species and lower rarity, and the opposite in lakes with lower nutrient concentrations and less turbidity. Methods Phytoplankton and abiotic variables samples were collected in fourteen lakes distributed in the municipality of Goiânia, Goiás, Brazil, during a rainy period. Results It was possible to identify an environmental heterogeneity among the lakes. We identified a separation of the lakes according to phytoplankton richness and density, especially due to the contribution of green algae, desmids, and cyanobacteria. Most lakes showed high diversity and evenness values, with a predominance of rare taxa and few dominant species. The main variables associated with phytoplankton were water temperature, dissolved oxygen, turbidity, and nutrient concentrations. Conclusions Therefore, the study of species diversity, dominance, and rarity based on phytoplankton richness and abundance and their relationship with different local environmental conditions can be an important model for assessing water quality in urban lakes. turbidity Thus Goiânia Goiás Brazil period density algae desmids cyanobacteria values temperature oxygen Therefore