Shallow Water Marine Sediment Bacterial Community Shifts Along a Natural CO2 Gradient in the Mediterranean Sea Off Vulcano, Italy

Abstract

The effects of increasing atmospheric CO(2) on ocean ecosystems are a major environmental concern, as rapid shoaling of the carbonate saturation horizon is exposing vast areas of marine sediments to corrosive waters worldwide. Natural CO(2) gradients off Vulcano, Italy, have revealed profound ecosystem changes along rocky shore habitats as carbonate saturation levels decrease, but no investigations have yet been made of the sedimentary habitat. Here, we sampled the upper 2 cm of volcanic sand in three zones, ambient (median pCO(2) 419 μatm, minimum Ω(arag) 3.77), moderately CO(2)-enriched (median pCO(2) 592 μatm, minimum Ω(arag) 2.96), and highly CO(2)-enriched (median pCO(2) 1611 μatm, minimum Ω(arag) 0.35). We tested the hypothesis that increasing levels of seawater pCO(2) would cause significant shifts in sediment bacterial community composition, as shown recently in epilithic biofilms at the study site. In this study, 454 pyrosequencing of the V1 to V3 region of the 16S rRNA gene revealed a shift in community composition with increasing pCO(2). The relative abundances of most of the dominant genera were unaffected by the pCO(2) gradient, although there were significant differences for some 5 % of the genera present (viz. Georgenia, Lutibacter, Photobacterium, Acinetobacter, and Paenibacillus), and Shannon Diversity was greatest in sediments subject to long-term acidification (>100 years). Overall, this supports the view that globally increased ocean pCO(2) will be associated with changes in sediment bacterial community composition but that most of these organisms are resilient. However, further work is required to assess whether these results apply to other types of coastal sediments and whether the changes in relative abundance of bacterial taxa that we observed can significantly alter the biogeochemical functions of marine sediments.

Rapid response of the active microbial community to CO 2 exposure from a controlled sub-seabed CO 2 leak in Ardmucknish Bay (Oban, Scotland)

“…4). This is similar to findings for biofilms exposed to low light conditions (Lidbury et al, 2012), intertidal epilithic biofilms (Taylor et al, 2014) and also sediments at natural CO 2 vent sites (Yanagawa et al, 2012;Kerfahi et al, 2014). All reported a decrease in measurements of alpha diversity with increasing pCO 2 concentrations.…”

“…This suggests that benthic microbial communities within surface sediments at zone 1 became more dominated by a few species. However, similar to detailed studies of the impact of elevated pCO 2 on both pelagic (Roy et al, 2012;Oliver et al, 2014) and benthic communities (Kerfahi et al, 2014), the majority of bacterial taxa were unaffected. The predominant response of the active community was temporal: clear differences occurred over time for many of the major taxonomic groups (Table 3).…”

Exploring the diversity and metabolic potential of actinomycetes from temperate marine sediments from Newfoundland, Canada

“…An advantage to using non-selective primers to assess bacterial diversity is that it allows one to assess abundance of Actinobacteria relative to other bacterial groups in a given habitat. The prevalence of Actinobacteria in NL sediments (<6 %) is similar to the prevalence observed in geographically diverse marine sediments, which varies from rare to <8 % [21,26,38,79]. In comparison, Actinobacteria may comprise up to 30 % of soil microbial communities [1,40].…”

“…Several reports have recently investigated the geographic effects on species distribution of marine planktonic diatoms [11], spore-forming thermophillic bacteria in Arctic marine sediment [31] and Arctic microbial communities [13] with some studies reporting an effect on microbial diversity that has been observed with spatial distribution [48,63,83]. Freel et al suggested that secondary metabolism influences ecological diversification within the genus Salinispora, where distinct species distribution is linked to specific geographic location and speciesspecific secondary metabolite profiles have been observed [24,38]. Actinomycetales, have been successfully cultured from the marine environment from varied habitats including the Mariana Trench [60], tropical sediments [29,33,34,45,50], sponges [53], North Sea sediments [82] and sediment from a Norwegian fjord [8].…”

Shift from coral to macroalgae dominance on a volcanically acidified reef

“…Volcanic enrichment of CO 2 from submarine vents has been shown to impact the structure of temperate and sub-tropical ecosystems, including seagrasses 18 , rocky-shore and rocky-reef communities 19,20 , soft sediments 21 and vermetid reefs 22 . The occurrence of CO 2 vents near coral reef ecosystems is rare and, at present, only two regions have been studied: Papua New Guinea (PNG; ref.…”