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Rising nutrient-pulse frequency and high UVR strengthen microbial interactions
Cabrerizo MJ, JM Medina-Sánchez, I Dorado-García, M Villar-Argaiz, P Carrillo. - 2017
Experimentos en la Laguna de La Caldera muestran que el efecto de la adición de nutrientes en los ecosistemas varía dependiendo de que su adición se realice de forma estocástica en un único evento en comparación a si ésta se lleva a cabo de forma crónica y espaciada en el tiempo. La adicción fraccionada favorece el crecimiento de las algas algal y la persistencia de una mayor biodiversidad funcional.
| Solar radiation and nutrient pulses regulate the ecosystem’s functioning. However, little is known about how a greater frequency of pulsed nutrients under high ultraviolet radiation (UVR) levels, as expected in the near future, could alter the responses and interaction between primary producers and decomposers. In this report, we demonstrate through a mesocosm study in lake La Caldera (Spain) that a repeated (press) compared to a one-time (pulse) schedule under UVR prompted higher increases in primary (PP) than in bacterial production (BP) coupled with a replacement of photoautotrophs by mixotrophic nano agellates (MNFs). The mechanism underlying these ampli ed phytoplanktonic responses was a dual control by MNFs on bacteria through the excretion of organic carbon and an increased top-down control by bacterivory. We also show across a 6-year whole-lake study that the changes from photoautotrophs to MNFs were related mainly to the frequency of pulsed nutrients (e.g. desert dust inputs). Our results underscore how an improved understanding of the interaction between chronic and stochastic environmental factors is critical for predicting ongoing changes in ecosystem functioning and its responses to climatically driven changes. |
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