Sustained effects of volcanic ash on biofilm stoichiometry, enzyme activity and community composition in North- Patagonia streams

CARRILLO, UARA; DÍAZ-VILLANUEVA, VERÓNICA; MODENUTTI, BEATRIZ

THE SCIENCE OF TOTAL ENVIRONMENT

Elsevier

Año: 2018 vol. 621 p. 235 - 244

0048-9697

Volcanic eruptions are extreme perturbations that affect ecosystems. These events can also produce persistenteffects in the environment for several years after the eruption, with increased concentrations of suspended particlesand the introduction of elements in the water column. On 4th June 2011, the Puyehue-Cordón Caulle VolcanicComplex (40.59°S-72.11°W, 2200 m.a.s.l.) erupted explosively in southern Chile. The area affected by thevolcano was devastated; a thick layer of volcanic ash (up to 30 cm) was deposited in areas 50 km east of the volcanotowards Argentina. The aim of the present study was to evaluate the effect of volcanic ash deposits onstream ecosystems four years after the eruption, comparing biofilm stoichiometry, alkaline phosphatase activity,and primary producer´s assemblage in streams which were severely affected by the volcano with unaffectedstreams.We confirmed in the laboratory that ash deposited in the catchment of affected streams still leach phosphorus(P) into the water four years after eruption. Results indicate that affected streams still receive volcanicparticles and that these particles release P, thus stream water exhibits high P concentration. Biofilm P contentwas higher and the C:P ratio lower in affected streams compared to unaffected streams. As a consequence ofless P in unaffected streams, the alkaline phosphatase activity was higher compared to affected streams.Cyanobacteria increased their abundances (99.9% of total algal biovolume) in the affected streams suggestingthat the increase in P may positively affect this group. On the contrary, unaffected streams contained a diatomdominant biofilm. In this way, local heterogeneity was created between sub-catchments located within 30 kmof each other. These types of events should be seen as opportunities to gather valuable ecological informationabout how severe disturbances, like volcanic eruptions, shape landscapes and lotic systems for several yearsafter the event.