Are the small-sized plankton communities of oligotrophic ecosystems resilient to UVR and P pulses?

Abstract

Evaluating how environmental stressor interactions influence ecosystem structure and functioning is critical to understanding the response of ecosystems to global change. We exposed a species-poor planktonic community to P pulses in the absence and presence of solar ultraviolet radiation (UVR). We used a field-mesocosm study in an oligotrophic mid-altitude lake to test the hypothesis that interaction between these factors affects the community's diversity and composition, but not its biomass-size spectrum, making this community resilient in terms of its C-transfer function. Our findings show that P pulses and UVR affected the relative abundance of different planktonic populations. The abundance of phytoplankton was enhanced strongly by P pulses and secondarily by UVR. The UVR Â P interaction affected only the smallest autotrophic species. Chlorococcal abundance increased, whereas chroococcal cyanobacteria decreased. However, UVR had a much more pronounced effect than P on the composition of microcrustaceans, and both factors interactively affected their biomass. Hence, the biomass-size spectrum was not resilient to the UVR Â P pulse interaction. The steepness of the slope increased under P-pulse conditions because zooplankton were not able to grow concomitantly with phytoplankton, as confirmed by the low zooplankton to phytoplankton biomass ratio (Z∶P). The observed planktonic changes under new foreseeable conditions that include an increase in UVR fluxes and P inputs might decouple the C cycle in inland oligotrophic lakes in the Mediterranean region.

Multiple interacting environmental drivers reduce the impact of solar UVR on primary productivity in Mediterranean lakes

“…Nine lakes from the Sierra Nevada National Park and Lagunas de Ruidera Natural Park were used to establish a gradient of Kd PAR . Lakes from Sierra Nevada National Park are mixed, oligotrophic high-mountain lakes located above the tree line on a siliceous bedrock in a glacial cirque 41 , whereas lakes in Lagunas de Ruidera Natural Park are mixed, oligotrophic ecosystems with high nitrate concentrations from land use, located on calcareous www.nature.com/scientificreports/ substrates 42 . Phytoplankton communities from these lakes have been the focus of recent studies aiming to determine the single effects of solar UVR, or their interaction in 2-level combinations, such as nutrient inputs 14,[42][43][44] , vertical mixing or stratification 18,45 and/or increased temperatures 46,47 on PP.…”

Macrophyte meadows mediate the response of the sediment microbial community to ultraviolet radiation

“…Furthermore, these shifts in the sediment microbial community are especially worrying in shallow lakes or wetlands, since these ecosystems are highly vulnerable to global change (Jeppesen et al, 2014). In fact, disturbances can occur rapidly in these systems (within a few days), making shallow lakes a type of temporary waterbody, where the microbial community will have to respond in the short-term (Rojo et al, 2017b).…”