The SARS-CoV-2 Omicron variant has increased infectivity and immune escape compared with previous variants, and caused the surge of massive COVID-19 waves globally. Despite a vast majority (~90%) of the population of Santa Fe city, Argentina, had been vaccinated and/or had been infected by SARS-CoV-2 when Omicron emerged, the epidemic wave that followed its arrival was by far the largest one experienced in the city. A serosurvey conducted prior to the
La complejidad de hábitats generada por macrófitas en ambientes acuáticos favorece la diversidad y producción de la biota. A pesar de la gran abundancia de macrófitas, existe escasa información en humedales aluviales del río Paraná. Nuestro objetivo fue determinar la relación de los atributos de ensambles de invertebrados pleustónicos con la complejidad de hábitat generada por los sustratos vegetales. Se recolectaron muestras en seis humedales en la llanura aluvial. Para determinar las medidas de complejidad de hábitat, se obtuvieron la biomasa, riqueza y dimensión fractal promedio de partes sumergidas de las macrófitas. Los invertebrados se identificaron y categorizaron en grupos funcionales, se contabilizaron y se obtuvo su biomasa por pesaje directo o empleando factores de corrección disponibles. Los atributos se relacionaron con la complejidad de hábitat empleando correlaciones lineales. Se registró una elevada diversidad, densidad y biomasa de taxones y de diferentes grupos funcionales de macroinvertebrados. Hubo una relación directa de la complejidad de hábitat con la riqueza y densidad del grupo de mayor especificidad por el sustrato vegetal (trituradores, herbívoros, raspadores) e indirecta con la densidad total y de recolectores. Concluimos que las macrófitas son generadoras de hábitat para diversos y abundantes macroinvertebrados en el río Paraná. Los atributos se relacionan con la complejidad de las partes sumergidas diferencialmente de acuerdo con su especificidad por el sustrato. Las macrófitas y losinvertebrados pleustónicos intervienen por deriva en diferentes procesos local y regionalmente, por lo que aportarían a la resiliencia del sistema río-llanura aluvial.
Dispersal is a key process affecting the diversity of natural communities. We addressed hydrochory of wetland plant seeds in the Middle Paraná River floodplain. We first studied seed dispersal by drifting macrophytes in the Paraná River main channel (MC), in a high discharge secondary channel (HD) and in two low discharge channels (LD) during an extraordinary flood. We then experimentally analyzed the effect of standing (SW) and moving water (MW) on seed buoyancy of different plant communities. We recorded seeds of 27 taxa distributed in 12 families. Taxa richness ranged from 17 in LD to 25 in MC, and included seeds of terrestrial, palustrine and aquatic plants. River discharge did not affect seed richness and density, which was probably associated with a homogenization process caused by the flood. Seed buoyancy significantly differed between water movement treatments independently of the source community, lasting longer in SW than in MW. Our results suggest that drifting macrophytes contribute to seed dispersal of several communities in the Middle Paraná River, and probably over long distances. Furthermore, seed buoyancy might be more important for surficial dispersal in low-energy systems, where subaqueous dispersal may be difficult due to the lack of current.
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