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

CARRILLO, UARA; DÍAZ VILLANUEVA, VERÓNICA; B. MODENUTTI,

SCIENCE OF THE TOTAL ENVIRONMENT

ELSEVIER SCIENCE BV

Lugar: Amsterdam; 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 suspendedparticles and the introduction of elements in the water column. On 4th June 2011, the Puyehue-Cordón CaulleVolcanic Complex (40.59°S-72.11°W, 2200 m.a.s.l.) erupted explosively in southern Chile. The area affectedby the volcano was devastated; a thick layer of volcanic ash (up to 30 cm) was deposited in areas 50 km east ofthe volcano towards Argentina. The aim of the present study was to evaluate the effect of volcanic ash depositson stream ecosystems four years after the eruption, comparing biofilm stoichiometry, alkaline phosphataseactivity, 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 stillleach phosphorus (P) into the water four years after eruption. Results indicate that affected streams still receivevolcanic particles and that these particles release P, thus stream water exhibits high P concentration.Biofilm P content was higher and the C:P ratio lower in affected streams compared to unaffected streams.As a consequence of less P in unaffected streams, the alkaline phosphatase activity was higher compared toaffected streams. Cyanobacteria increased their abundances (99.9% of total algal biovolume) in the affectedstreams suggesting that the increase in P may positively affect this group. On the contrary, unaffected streamscontained a diatom dominant biofilm. In this way, local heterogeneity was created between sub-catchmentslocated within 30 km of each other. These types of events should be seen as opportunities to gather valuableecological information about how severe disturbances, like volcanic eruptions, shape landscapes and lotic systemsfor several years after the event.