Estudio de la sucesión de microorganismos acuáticos en suelos con distintos usos en la cuenca del río Salado (provincia de Buenos Aires)

Abstract

Las diferencias en la topografía determinan diferencias en la frecuencia, intensidad y duración de las fases de inundación y sequía así como la oferta de hábitat para micro y macroorganismos, mientras que distintos usos del suelo afectan la concentración de nutrientes, y la actividad biológica influye en la dinámica de nutrientes del ambiente. El conocimiento de los efectos de la inundación sobre la fertilidad de los suelos y sobre el río permitirá conocer las respuestas de ambos ecosistemas frente a los disturbios que provoca el uso actual de la tierra y los que ocurrirán con las acciones planificadas de manejo y regulación del cauce principal en un futuro cercano. El objetivo general del trabajo fue identificar las especies de microorganismos (productores y consumidores) del agua de inundación que se suceden desde el anegamiento a la desecación en suelos con distinto uso y pendiente así como también conocer los principales cambios físico-químicos, contenido de nutrientes y materia orgánica del agua en los diferentes estadios de inundación del suelo, y finalmente construir modelos conceptuales de funcionamiento de estos sistemas naturales y sus efectos sobre las características del agua de escorrentía superficial.

Effects of surface runoff from agricultural soils on the succession of microconsumer organisms in a lotic mesocosm

“…Nitrates and nitrites increased gradually during the experiment, owing to the endogenous nitri cation processes and the incorporation of water to maintain the water level of the mesocosm. Nevertheless, the previous investigations involving a long ooding period in lentic systems (Quaíni 2011;Solari et al 2018;Zaplara et al 2023) observed that the water nitrate decreased markedly for up to 15 days and remained very low thereafter. This nding was attributable to a consumption by the producing microorganisms, which registered a substantial development until the end of the ooding, and also coincided with the observed decrease in SRP.…”

“…These redox reactions are affected by the physical, chemical, and biologic characteristics of soils; the organic substrates; and the thickness of the water layer (Morales 2004). We therefore analyzed the nutrient dynamics in studies performed in ooded soils under lentic conditions and observed that during the rst days of ooding the phosphorus concentrations in the water increased since phosphorus was released from the soil under anoxic conditions, thus being available for the primary producers (Quaíni 2011;Zaplara 2021;Zaplara et al 2023).…”

“…Zooplankton dynamics in lentic systems are considered to be predictable and mainly driven by biologic processes (Sommer et al 1986). For example, a relationship between the number of taxa, the topographic position, and the ooding time in soils has been observed under lentic conditions (Quaíni 2011;Solari et al 2018; Zaplara 2021; Zaplara et al 2023), with early successions and simple trophic webs developing in soils ooded for short periods and advanced successions with more complex trophic webs in longer oods.…”

“…The term succession refers to the changes that occur in the composition and structure of communities after a discrete and usually unpredictable disturbance in a given environment (Fisher 1990). Accordingly, the hypothesis and objectives of this present investigation arose from other studies performed in the Salado-River basin (Quaíni 2011) in relation to the observation that soil exposure to ooding under lotic conditions-those including surface runoff, current speed, turbulence, and turbidity, among othersgenerates a low availability of nutrients owing to the aforementioned inability of the soil to release phosphorus under oxidizing conditions. These environmental alterations become re ected in the development of producers and higher trophic chains, a restructuring that can determine the development and succession of microconsumers, depending on the degree of the latter's susceptibility or tolerance to such changes.…”