La basura marina antropogénica ha sido reconocida como un serio problema ambiental, económico, de salud humana y estético a nivel mundial. Las playas de arena proveen una gran cantidad de servicios ecosistémicos además de recreación, y son altamente afectadas por la presencia de basura. En este trabajo se evaluó la composición de la basura marina encontrada en tres playas oceánicas de Uruguay, y se determinó su flotabilidad y la presencia/ ausencia de organismos epibiontes sobre ella. Los plásticos flotantes sin epibiontes fueron el tipo de ítem más abundante en todas las playas, la ausencia de epibiontes permitió inferir que las fuentes son principalmente locales. También se registró una pequeña proporción de plásticos flotantes con epibiontes (bivalvos, briozoos y balanos), indicando evidencia de que estos ítems permanecieron en el medio marino durante un tiempo suficiente para ser colonizados antes de ser depositados en la playa, posiblemente impulsados por las corrientes. Nuestros resultados sugieren que gran parte de la basura es de origen local. Esto podría ser una consecuencia de una deficiente gestión de residuos que se derivan de la actividad humana en la región. Por ello, se recomienda abordar el problema desde una perspectiva local de gestión y educación ambiental comunitaria.

Raphidiopsis (Cylindrospermopsis) raciborskii, a globally distributed bloom-forming cyanobacterium, produces either the cytotoxin cylindrospermopsin (CYL) in Oceania, Asia and Europe or the neurotoxin saxitoxin (STX) and analogues (paralytic shellfish poison, PSP) in South America (encoded by sxt genetic cluster) and none of them in Africa. Nevertheless, this particular geographic pattern is usually overlooked in current hypotheses about the species dispersal routes. Here, we combined genomics, phylogenetic analyses, toxicity data and a literature survey to unveil the evolutionary history and spread of the species. Phylogenies based on 354 orthologous genes from all the available genomes and ribosomal ITS sequences of the taxon showed two well-defined clades: the American, having the PSP producers; and the Oceania/Europe/Asia, including the CYL producers. We propose central Africa as the original dispersion center (non-toxic populations), reaching North Africa and North America (in former Laurasia continent). The ability to produce CYL probably took place in populations that advanced to sub-Saharan Africa and then to Oceania and South America. According to the genomic context of the sxt cluster found in PSP-producer strains, this trait was acquired once by horizontal transfer in South America, where the ability to produce CYL was lost.

It is widely known that the environmental conditions caused by the construction of reservoirs favor the proliferation of toxic cyanobacteria and the formation of blooms due to the high residence time of the water, low turbidity, temperature regimes, among others. Microcystin-producing cyanobacteria such as those from the Microcystis aeruginosa complex (MAC) are the most frequently found organisms in reservoirs worldwide, being the role of the environment on microcystin production poorly understood. Here, we addressed the community dynamics and potential toxicity of MAC cyanobacteria in a subtropical reservoir (Salto Grande) located in the low Uruguay river. Samples were taken from five different sites (upstream, inside the reservoir and downstream) during contrasting seasons (summer and winter) to analyze: (i) the MAC community structure by amplicon sequencing of the phycocyanin gene spacer, (ii) the genotype diversity of microcystin-producing MAC by high resolution melting analysis of the mcyJ gene, and (iii) the abundance and mcy transcription activity of the microcystin-producing (toxic) fraction. We found that MAC diversity decreased from summer to winter but, despite the observed changes in MAC community structure, the abundance of toxic organisms and the transcription of mcy genes were always higher inside the reservoir, regardless of the season. Two different genotypes of toxic MAC were detected inside the reservoir, one associated with low water temperature (15 °C) and one thriving at high water temperature (31 °C). These findings indicate that the environmental conditions inside the reservoir reduce community diversity while promoting the proliferation of toxic genotypes that actively transcribe mcy genes, whose relative abundance will depend on the water temperature.

Knowledge about biodiversity changes during transitions from glacial landscape to lake formation is limited to contemporary studies. Here, we combined analyses of lithology, chronology and geochemistry with sedimentary ancient DNA metabarcoding to assess such transition in maritime Antarctica. We inferred three paleoenvironmental stages covering the Holocene glacier retreat process. From 4900 to 3850 years before the present, we found the lowest prokaryotic richness/diversity, with bacterial taxa indicators associated to soil and terrestrial environments. From 3850 to 2650 years before the present, a higher carbon content, higher Carbon/Nitrogen variability, increased species richness/diversity, and prokaryotic taxa indicators of long-term energy starvation were detected. Finally, from 2650 to 1070 years before the present, we inferred the onset of a genuine lacustrine environment holding stable Carbon/Nitrogen ratios and the highest prokaryotic diversity, with known aquatic bacterial taxa. Our study unveils for the first time the evolution from a glacier-covered to a freshwater lake through a millennial scale.

La diversidad de miradas y aproximaciones a un mismo problema resulta en mayores alternativas para su solución. Esto es especialmente relevante en el ámbito de la ciencia y la innovación tecnológica, en el que a las mujeres se las reconoce por promover el trabajo y la interdisciplina con más fuerza que los varones. Pero las contribuciones de las mujeres son invisibilizadas, su avance en la carrera académica es afectado y sufren situaciones en el ambiente laboral que afectan su salud. Entre las áreas con mayor sesgo desfavorable a las mujeres se encuentran las ciencias del mar y la ecología acuática. Para mejorar esta situación es fundamental visibilizar y discutir estas temáticas para también contribuir a la diversidad del pensamiento. En este marco, nuestro objetivo fue investigar sobre distintos aspectos del rol de la mujer en estos espacios y contribuir a eliminar sesgos de género. Para ello, realizamos un cuestionario sobre la brecha de género y su percepción en las ciencias del mar y la ecología acuática en Uruguay, analizando también la relación con las tareas de cuidados y las formas de discriminación. La consulta incluyó a participantes de distintos géneros. Los resultados evidencian la brecha de género durante la formación académica y en el acceso a cargos; en especial, a los más altos. Se identificaron diversas formas de violencia sobre las mujeres. Sin embargo, la discriminación fue percibida como ajena en el ámbito de trabajo propio y no siempre como relevante, sobre todo por los varones. Estos resultados coinciden con la estereotipificación que históricamente han sufrido las mujeres trabajando en ciencias en general, y en ciencias del mar y ecología en particular. Planteamos que es fundamental generar cambios en los paradigmas para promover una cultura científica inclusiva y cooperativa, y la coexistencia de diversidad de enfoques.

Toxic blooms dominated by cyanobacterial colonies of Microcystis aeruginosa complex (MAC) accumulate in the water surface, so they can be tracked by remote sensing. The abundance of toxic MAC cells is related to colony size, a parameter affecting water-leaving radiance (L_w). Here, we design a strategy to estimate the in situ abundance of toxic MAC based on optical remote sensing. Bio-geo-optical models were constructed for a large subtropical reservoir (Salto Grande in the Uruguay River) to estimate the abundance of toxic MAC using remote sensing reflectance (R_rs or L_w normalized by downwelling irradiance) indices. Spectrally weighted R_rs ratios were derived from smartphone measurements and related to three aggregated proxies of MAC (chlorophyll a, biovolume, and the abundance of mcyE gene copies, C^mcyE) using regression models and machine learning techniques. A classification tree (CART) model identified a threshold in the red/green reflectance ratio of 1.216 to predict the presence of high (> 1000 cells mL^-1) or low (< 1000 cells mL^-1) C^mcyE (average accuracy = 0.66, sd = 0.14). Our results suggest that MAC toxic and non-toxic cells can be discriminated in Salto Grande reservoir by using first-order optical proxies derived by a smartphone. The resulting R_rs ratio thresholds can be exploited to develop a cell phone-based tool able to detect toxic blooms, allowing citizen monitoring of aquatic ecosystems and provide a fruitful avenue to advance in the remote prediction of harmful blooms. The generalization of the method to other water bodies requires validation with local measurements.

The toxic cyanobacterium Microcystis causes worldwide health concerns, being frequently found in freshwater and estuarine ecosystems. Under natural conditions, Microcystis spp. show a colonial lifestyle involving a phycosphere populated by a highly diverse associated microbiome. In a previous study, we have proposed that colony formation and growth may be achieved through mechanisms of multispecies bacterial biofilm formation. Starting with single-cells, specific bacteria would be recruited from the environment to attach and create a buoyant biofilm or colony.