The concentrations of twenty metal elements in seawater and in plankton around the recently erupted submarine volcano Tagoro just South of the island El Hierro (Canary Islands, Spain) were investigated in order to assess their potential hazard to the marine environment. Samples of the seawater and the plankton were collected from 2013 to 2016 during the Vulcano and Vulcana monitoring cruises, using a rosette with Niskin bottles and a WP2 net (200 m mesh size). Significantly higher concentrations of many metals were found in both the seawater and the plankton around the volcano compared to reference stations. The amount of metals emitted by the volcano appeared to be decreasing over the years following the eruption in 2011-2012, which greatly reduced the biomass of the plankton living in the area of influence of the volcano. In 2013 the metal concentrations found in the plankton living in the area were very high, but a decrease in concentrations was found towards 2016. Around the volcano the metal concentrations in the plankton were significantly higher than at the reference stations, just like in the seawater, except for 2016, which showed significantly lower concentrations. The increase in metal concentrations due to the volcano was comparable to increases in concentrations due to anthropogenic pollution in other studies. The decrease in concentrations in 2016 could be attributed to the strong increase in biomass of the plankton, induced by the large amounts of nutrients and Fe(II) emitted by the volcano. It is most likely that the high concentrations of toxic metals caused DNA damage in the plankton and that these metals were tranferred up in the foodchain. But as the concentrations have diminished greatly, they do not seem to pose a hazard anymore in 2016. It appears that the ecosystem, after being strongly damaged and intoxicated by metals from the volcano, was able to recover using elements emitted by the same volcano.

MINECO and FEDER (Vulcano, CTM2012-36317)