New geological, geophysical and biological insights on the hydrothermal system of the Panarea – Basiluzzo Volcanic complex (Aeolian Islands, Tyrrhenian Sea)
Bortoluzzi G; Spagnoli F; Aliani S; Romeo T; Canese S; Esposito V; Grassi M; Masetti G; Dialti L; Cocchi L; Muccini F; Lacono V; Yakimov M; La Spada G; Ligi M; Giordano P; Franchi F; Ferrante V; Borgognoni L; Tudino T; Guideri M; Ivaldi R; Pratellesi M; Marziani F; Niccolini A; Barbieri E; Capaccioni B; Andaloro F;
Since the exhalative crisis of 2002 cruises were carried out to investigate morphology, magnetic
and gravity fields, fluid escape, plume anomalies, biological and microbiological activity, benthic
fluxes, early diagenesis, mineralogy and geochemistry of water and sediments of the hydrothermal
system of Panarea. The volcanic complex was mapped by multibeam, including backscatter
analysis, and magnetometric surveys were done to detect low magnetization in areas with
hydrothermal activity, i.e., vents, sulphide deposits, chimney fields. CTD by ship and on ROV
detected acidic plumes at bottom (minimum pH value 6.5) and mid depths.
An Automatic Benthic Chamber was deployed on a terrace (40m) and in depressions with gascharged
and hydrothermally altered sediments (80m). At the 40m site, strong releases of Dissolved
Inorganic Carbon (DIC) and Fe, Mn, Zn (75.7, 2.0, 2.9, 3.4 mmol m-2 day-1) were found. Average
decrease of pH in the chamber was ~4 units day-1 with a H+ benthic flux of 0.32 mmol m-2 day-1).
DIC values of seawater had average 2.3, increasing to 3.1 on degassing vents, while 7.5 mmol was
measured on top of a bubbling core.
ROV dives explored and sampled several sites; active chimneys (black, red crusts and yellowishorange
precipitates at top) were recovered on the SE flanks of Basiluzzo; pH value of 5 was
measured aboard on sediments. XRD and XRF data on the external crust showed Fe-Mn
oxyhydroxides, including goethite and opal, with Co, Ce, Sr, Zn and Cu enrichments, whereas the
inner part are depleted of Fe, Mn and other metals, mostly under detection limits. SEM imagery
shows porous filamentous minerals, that are probably bacterial in origin. Dives to SW discovered
fields of partially or totally relict chimneys at the same depth (~200m). Chimneys are present on
the edges of slope failures and settled on areas of relative lower positive magnetic anomaly,
indicating possible shallow depth level of hydrothermal alteration. Reddish crusts and sediments,
and acid, gas boiling water (pH 5.5) were cored at 90 m depth upslope of the ‘active’ chimneys;
upslope from the ‘relict’ chimney’s fields, oxized-normal sediments were found.
Biological investigations on the sediments revealed a community strongly dominated by the
amphipod Ampelisca ledoyeri (43.8 % of the total abundance), probably dwelling in the tubepatches.
Rare species were detected on the chimney’s samples.
The phylogenetic diversity of microbial communities in the precipitates collected on chimneys and
on Bottaro vent was analyzed by bacterial and archaeal 16S rDNA clone libraries, showing a
dominance of sulfur-oxidazing epsilon and gamma proteobacteria. Very interesting groups of
archaea were revealed including methanotrophic Thermoplasmatales and members of SM1
candidate division. Overall prokaryotic diversity was found similar to that of deep sea hydrothermal
vents and other sulfidic habitats. White microbial mats were found in an area S of Panarea, on a NS
oriented fracture.
2014 - Abstract in rivista
Rendiconti online Società Geologica Italiana 31 (2014): 1. doi:10.3301/ROL.2014.140
Keywords: Panarea