Metallic nanoparticle enrichment at low temperature, shallow CO2 seeps in Southern Italy

Abstract

a b s t r a c t a r t i c l e i n f oWe report on metal enrichment along a natural pH gradient owing to increased CO 2 degassing at cold, shallow seeps of Vulcano Island in the Mediterranean Sea, off Sicily. We assessed composition of unfiltered and filtered seawater (b100 nm) along acidic zones ranging between ambient and pH 5, and showed that most seep derived elements are present as nanoclusters which then aggregate into larger colloids while mixing with ambient seawater along a pH gradient. Size and elemental composition of such naturally occurring nanoparticles assessed by modern characterisation methods were in good agreement with the results from conventional analytical methods. We provide analytical evidence for the presence in the water column of a large fraction of seep derived elements (e.g. approximately 50% of iron, over 80% of Mn, 100% of Cr, S and Zn) in the form of nano sized particles (e.g. b 100 nm) even at typical open ocean pHs. We launch in situ sampling protocols and sample preparation procedures for multi-method suitable to obtain accurate measurements on nanoparticles from environmental samples. Based on our results a first insight to the formation of natural nanoparticles at cold CO 2 seeps is presented and the persistence of such nano-clusters in the surrounding seawater is stipulated.

Trace element profiles of the sea anemoneAnemonia viridisliving nearby a natural CO2vent

“…This is in accordance with substantial enrichment in the seawater, as measured by Kadar et al (2012) (Table 1). As seawater pH decreases there is also an increase in free copper ion concentration and hence copper bioavailability (Millero, Santana-Casiano & González-Dávila, 2010).…”

“…Accordingly, a high seawater concentration of dissolved Fe was reported close to the primary CO 2 vent (Kadar et al, 2012; Boatta et al, 2013), as well as in suspended particulate material collected in this study (14 fold higher compared to the control site; Table 1). Indeed, the most significant change at the high p CO 2 site was found for Fe, which accumulated in both the anemone tentacles and pedal disc (5 and 15 fold, respectively; Table 2).…”

Elevated trace elements in Posidonia oceanica and Cymodocea nodosa at six Mediterranean volcanic seeps

“…The ecological risk posed by the effects of OA on metal contaminated water column and sediments is difficult to assess in the laboratory (Millero et al, 2009), which emphasizes the importance of studies on the interplay between trace elements and OA in-situ. Submarine hydrothermal activity is of interest as this causes natural gradients in both ocean acidity and trace elements, providing natural conditions to assess their combined effects (Monia Renzi et al, 2011;Kadar et al, 2012;Vizzini et al, 2013) on marine biota. While relationships among organisms, environmental factors and trace elements have received much attentions at deep sea hydrothermal vents (Kadar et al, 2007;Cravo et al, 2007), those of shallow marine CO 2 seeps are still little understood.…”

“…Shallow water CO 2 seeps represent natural analogues for future coastal ecosystems, providing entire seabed of marine communities exposed to the shifts in carbonate chemistry (low pH) expected for 21 st century (Hall-Spencer et al, 2008;Enochs et al, 2015;Connell et al, 2017). At such seeps, there are often elevated levels of trace elements and hydrogen sulphide (H 2 S) (Kadar et al, 2012;Boatta et al, 2013;Vizzini et al, 2013) combined with low pH that may be harmful to marine biota (Barry et al, 2010;Lauritano et al, 2015;Olivé et al, 2017). At these CO 2 seeps, habitat forming marine fauna (such as macroalgae and seagrass) are observed (Apostolaki et al, 2014;Vizzini et al, 2010) which provides a window of opportunity to investigate the combined effects of OA and metal levels on seagrass.…”

Shallow-water gaseohydrothermal plume studies after massive eruption at Panarea, Aeolian Islands, Italy

“…The mixing of seawater with vent fluids changes geochemical processes and mineralization patterns (Rona et al, 2006) as well as seawater composition which increase the amount of CO 2 , sulfur and metals (Allard et al, 1991;Kadar et al, 2012).…”