The susceptibility of cladocerans in North Andean-Patagonian lakes to volcanic ashes

WOLINSKI, L.; C. LASPOUMADERES; M. A. BASTIDAS NAVARRO; B. MODENUTTI; E. BALSEIRO

FRESHWATER BIOLOGY (PRINT)

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2013 vol. 58 p. 1878 - 1888

0046-5070

1- Explosive volcanic eruptions are one of the few natural phenomena that can produce global catastrophic effects. On 4 June 2011, an eruption in the Puyehue volcanic complex (40°35’S, 72°06’W, Chile) discharged massive amounts of ash and pumice into the surrounding landscape in Argentina (North-Andean Patagonia). The ejected material affected the nearby aquatic environments, producing an increase in total suspended solids (TSS). 2- We combined field data and laboratory experiment data to determine the effect of the volcanic ashes suspended in the water column on cladoceran populations. 3- During the summer of 2011-2012 (6 months after the eruption), the zooplankton populations in these lakes decreased, due mainly to the disappearance of cladocerans. This decrease in zooplankton was not caused by a food shortage; the chlorophyll a concentrations in the lakes were higher than those in previous years or in the following season, and no change in phytoplankton size was observed. By the following summer (2013), 18 months after the eruption, a recovery of cladoceran populations was observed, with a concomitant decrease in TSS. 4- We performed a life table experiment, examining Daphnia commutata survival and fecundity at a series of ash concentrations. We showed that ash concentrations of 2, 3, 5 and 8 mg L-1 negatively affected survival and fecundity. Populations exposed to 8 mg L-1 of ash cannot succeed; these organisms fail to produce offspring because they die before reaching reproductive age. 5- We conclude that the disappearance of cladocerans was due to the presence of ash. As the sedimentation process occurs, the ash concentrations decrease, favouring population recovery. This was observed in the following summer; when the lakes recovered their original transparency with low TSS values, the cladoceran populations also returned to their historical abundances. In conclusion, previous data on other explosive volcanic eruptions and the present data suggested that immediately after the ash fall zooplankton suffer reduction in abundance in particular non-selective filter feeders such as daphnids. However, few years after the eruption a recovery in zooplankton population growth may be expected.