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

Abstract

Volcanic eruptions are extreme perturbations that affect ecosystems. These events can also produce persistent effects in the environment for several years after the eruption, with increased concentrations of suspended particles and the introduction of elements in the water column. On 4th June 2011, the Puyehue-Cordón Caulle Volcanic Complex (40.59°S-72.11°W, 2200m.a.s.l.) erupted explosively in southern Chile. The area affected by the volcano was devastated; a thick layer of volcanic ash (up to 30cm) was deposited in areas 50 km east of the volcano towards Argentina. The aim of the present study was to evaluate the effect of volcanic ash deposits on stream 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 unaffected streams. 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 volcanic 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 to affected streams. Cyanobacteria increased their abundances (99.9% of total algal biovolume) in the affected streams suggesting that the increase in P may positively affect this group. On the contrary, unaffected streams contained a diatom dominant biofilm. In this way, local heterogeneity was created between sub-catchments located within 30 km of each other. These types of events should be seen as opportunities to gather valuable ecological information about how severe disturbances, like volcanic eruptions, shape landscapes and lotic systems for several years after the event.

Impacts of volcanic eruptions and early recovery in freshwater environments and organisms

“…Pumice rafting can generate increased turbidity in streams and lakes (Fig. 2A, B) (Larson, 1993;Inbar et al, 1995;Bisson et al, 2005;Carrillo et al, 2018). As a consequence, light penetration decreases, affecting primary producers (Table 1).…”

“…On the other hand, little is known about the immediate effects of tephra inputs on bacterial communities in stream biofilms. A recent study showed that increased inorganic P levels due to tephra input in streams reduced the activity of alkaline phosphatase, implying a reduction in P-limitation of the biofilm community (Carrillo et al, 2018). It would be of interest to investigate this community further to identify the effects of these changes on community structure (bacterial diversity) and biofilm functioning (enzymatic activity).…”

Living at the Frontiers of Life: Extremophiles in Chile and Their Potential for Bioremediation

“…Volcanic activity has been also reported with a high eruption frequency ( Carrillo et al, 2018 ), which has formed numerous hydrothermal fields including Porcelana Hot Spring and Geyser, and Cahuelmo Hot Spring. Cahuelmo Hot Spring is a geothermal site located at the sea level coast of Cahuelmo Fjord, that contains waters rich in metallic minerals and elements such as pyrite, polonium, magnetite, and chalcopyrite ( Mackenzie et al, 2013 ).…”

Variation in riparian and stream assemblages across the primary succession landscape of Mount St. Helens, U.S.A.

“…Current understanding of volcanic disturbance effects in streams is mostly associated with ash deposition in pre‐existing channels (e.g. Ayris & Delmelle, 2012; Carrillo et al., 2018). Overall effects range from partial loss of taxonomic and functional diversity (e.g.…”