Alberto J. Sánchez

The variability of 11 physicochemical and biological variables in the water column was analyzed in lentic and lotic environments during two intraannual water level periods over 10 non-consecutive years within a hydraulically interconnected alluvial zone of a tropical fluvial system. The evaluation included the limnological characterization, a principal component analysis (PCA) based on eight key variables, and the examination of inherent and recurrent variability of data through violin plots. The limnological characterization and PCA, both based on variable-level analysis, partially explained the variation among four conditions: lotic high water level, lentic high water level, lotic low water level, and lentic low water level. Whereas, the analysis of inherent data variability pointed out three conditions associated with kinetic energy and water column processes. First, the fluvial explained primarily by sediment transport and nutrient enrichment. Second, lateral homogenization of electric conductivity, water transparency and dissolved oxygen saturation. Third, lentic in low water level, when lakes worked as bioreactors exhibiting high biology productivity and oxygen supersaturation. In conclusion, the inherent data variability of the key variables supports the hypothesis that the physicochemical variability is driven by recurrent and interactive conditions. These findings show that the analysis of data variability provides a useful tool for understanding water column dynamics and identifying the principal conditions regulating the ecological functioning of tropical riverine wetlands.

The spatial–temporal dynamics of an in vitro radicular system of Typha domingensis for the development of rhizofiltration technologies, with the potential for use as a phytotreatment of eutrophicated water, were studied for the first time in the roots of seedlings and in rhizotron systems. The effect of indole-3-acetic acid (AIA) in combination with kinetin (CIN) or 6-benzylaminopurine (BAP) on seedlings cultivated in the light and dark in three radicular systems and in a rhizotrophic regime for the screening of dynamic rhizogenic lines, by weekly allometric measurements of the length and number of roots, were studied. Inhibition of the elongation and branching velocities of roots by BAP and light was observed but CIN increased elongation and branching. In rhizotrons cultivated in light and dark conditions with different AIA/CIN ratios, isolated root explants remained inactive; however, roots attached to a meristematic base presented a significant increase in growth development, with values comparable to those of roots attached to seedlings cultivated in light without hormones. The results revealed that six adventitious rhizogenic root lines with basal meristems have the potential for use in a wide range of environmental and innovative applications in phytotreatment technologies involving eutrophicated water.

El ecosistema de manglar es diverso y la composición de sus especies varía longitudinalmente en todo el mundo, por ello, la productividad primaria en base a la caída de hojarasca ha sido estudiada ampliamente. En el presente estudio se evaluó la producción de hojarasca durante tres años para identificar patrones en relación a físico químicos del agua y sedimento. La caída de hojarasca se midió por medio de trampas, además, se midieron los físicos químicos (salinidad, potencial redox, conductividad, temperatura y pH) de agua superficial, intersticial y subterránea, y de sedimentos del manglar (Textura, pH, materia orgánica, densidad aparente y contenido de humedad). Los principales resultados mostraron que la producción de hojarasca registró baja variación interanual, con 5.15 ton•ha-1•año-1 el primer año (2014-2015), el segundo año (2015-2016) fue de 5.1 ton•ha-1•año-1 y el tercer año (2016-2017) registró una producción menor con 4.93 ton•ha-1•año-1, con alta influencia de los niveles de salinidad, patrón de inundación y las precipitaciones, además el tipo de sustratos finos (arcillas) mantienen las condiciones de retención de humedad y materia orgánica, que permiten al manglar un mayor reciclamiento de nutrientes in situ que se refleja en mayor productividad primaria. Así mismo, la respuesta negativa en la producción de hojarasca del manglar al aumento de la salinidad, enfatiza la necesidad de documentar dichos procesos ante escenarios de cambio climático global.

Eutrophication-resistant phytoplankton communities in freshwater ecosystems have a novel lipid potential to contribute to the development of tropical regions. The question that arises due to the unsustainability of their eutrophicated waters is how the recognition of the lipids of the resident phytoplankton progresses. Our aim was to provide an overview of the pico-, nano- and micro-cellular lipids of phytoplankton with a focus on eutrophic tropical freshwater ecosystems. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) framework, global and Latin American publications were retrieved based on search equations and specific questions. In total, 490 studies were reviewed. The inclusion criteria, in order, were (1) peer-reviewed articles, (2) articles investigating phytoplankton strains or communities from any aquatic environment, (3) articles on freshwater ecosystems, and (4) research in tropical climates. The contribution of freshwater phytoplankton was high and discontinuous, with a representation of 63% in the 21st century. Freshwater themes were resolved in the ecological context with phytoplankton or algae keywords, while microalgae were targeted using resource use keywords. On the tropical scale, technological themes on lipid microalgae were related to fatty acids, biofuels, biodiesel, antioxidants, and recombinant DNA. It is concluded that studies of the lipid composition of phytoplankton communities are delayed in the case of eutrophic tropical freshwater ecosystems.

The intake of microplastics by freshwater fishes has been scarcely studied, and it is not yet clear whether the amount of particles these vertebrates ingest is associated with their feeding strategies. Hence, this study is focused on the suckermouth armored catfish (Pterygoplichthys spp.) under the hypothesis that, due to its detritivorous habits and demersal distribution, it may show evidence of the presence of microplastics in the sediments of a lake located in the Metropolitan Area of Villahermosa. A total of 21 organisms contained plastic microfibers throughout their digestive systems. These were treated with three solutions (hydrogen peroxide, potassium hydroxide, and sodium hypochlorite) to separate the microplastics. A total of 147 plastic particles of two categories were collected: microfibers (92%) and fragments (8%). Considering these results, as well as evidence in the literature, these species may constitute a global indicator of the incorporation into the trophic chain of microfibers deposited in the sediments of freshwater ecosystems.

Water quality indicators have been tied to natural or man-made surface hydraulic connection (SHC) conditions. Among these, temporally connected lakes (TCL) are hydraulic intermediates between isolated (IL) and permanently connected lakes (PCL). Therefore, the aim of this study is to answer if water quality indicators can estimate the possible overlap between the two opposed conditions of SHC (IL and PCL) with the intermediate one (TCL) in lakes with similar modifications in the water level regulation at the basin level. Among nine water variables sampled in six lakes with the three SHC conditions mentioned, chlorophyll a (Chl-a), Secchi disk (SD), and total phosphorus (TP) were identified as quality water indicators through principal component analysis. Furthermore, said indicators were used to measure their overlap and trophic state index deviations. The Chl-a, SD, and TP values in TCL showed a 0.72 overlap of PCL and IL. TP surplus measured in all the lakes was meaningful in urbanized ILs and lessened in a rural lake (PCL6) with submerged rooted macrophytes. The estimated overlap of trophic indicators between TCL, IL, and PCL in this study must be verified at a global representative scale for predictive and preventive use in the conservation of tropical coastal plain lakes.

Objective: To study the conservation status of the tropical rainforest in the “Cañón del Usumacinta” Flora and Fauna Protection Area in Mexico, through an analysis of the change in land use and vegetation (1997, 2009 and 2016). Design/Methodology/Approach: Vegetation and land use shapefiles at 1:250,000 scale (national continuum) corresponding to 1997 (series I), 2009 (series IV), and 2016 (series VI) were downloaded. Finally, a spatial analysis was generated with calculation of exchange rates, using the Land Change Modeler between 1997-2009 and 2009-2016. Results: During 1997-2009, the tropical rainforest occupied 31.2% and the greatest impact of the period seen was a change rate of 7.4%. Subsequently, between 2009 and 2016 there was a great decrease in the land use change rate in the forest (0.8%), due to its decree as a federal Protected Area in 2008, as well as natural regeneration and the promotion of ecological restoration programs. Study Limitations/Implications: Absence of geographic variables to analyze factors driving change in land use. Conclusions: It is essential to promote the sustainable management of the Usumacinta Canyon based on what is established in the land use planning program and the management plan, and to redouble efforts to implement actions for restoring ecosystem services and the continuous monitoring of change in land use.