Persistent natural acidification drives major distribution shifts in marine benthic ecosystems

Abstract

Ocean acidification is receiving increasing attention because of its potential to affect marine ecosystems. Rare CO 2 vents offer a unique opportunity to investigate the response of benthic ecosystems to acidification. However, the benthic habitats investigated so far are mainly found at very shallow water (less than or equal to 5 m depth) and therefore are not representative of the broad range of continental shelf habitats. Here, we show that a decrease from pH 8.1 to 7.9 observed in a CO 2 vent system at 40 m depth leads to a dramatic shift in highly diverse and structurally complex habitats. Forests of the kelp Laminaria rodriguezii usually found at larger depths (greater than 65 m) replace the otherwise dominant habitats (i.e. coralligenous outcrops and rhodolith beds), which are mainly characterized by calcifying organisms. Only the aragonite-calcifying algae are able to survive in acidified waters, while high-magnesium-calcite organisms are almost completely absent. Although a long-term survey of the venting area would be necessary to fully understand the effects of the variability of pH and other carbonate parameters over the structure and functioning of the investigated mesophotic habitats, our results suggest that in addition of significant changes at species level, moderate ocean acidification may entail major shifts in the distribution and dominance of key benthic ecosystems at regional scale, which could have broad ecological and socio-economic implications.

Acclimation of bloom‐forming and perennial seaweeds to elevated pCO2 conserved across levels of environmental complexity

“…Our results stand in contrast to studies carried out in naturally CO 2 rich systems, where it is often nonbloom‐forming species traditionally grouped within the Phaeophyta that perform best (Enochs et al., ; Johnson et al., ; Linares et al., ; Porzio et al., ). Similar studies that find heterokont algae to cope best at high p CO 2 levels, with only some green seaweeds (such as Ulva ) surviving the long‐term effects of ocean acidification (Newcomb, Milazzo, Hall‐Spencer, & Carrington, ).…”

“…Further, interactions of rising p CO 2 and other aspects of climate change can alter the response to elevated p CO 2 greatly: temperature (Pandolfi, Connolly, Marshall, & Cohen, ) and nutrient load (Cai et al., ; Flynn et al., ; and e.g., Porzio, Buia, & Hall‐Spencer, ; for a study on natural high‐CO 2 regions in nutrient deplete conditions) are known to alter how microalgae and macroalgae respond to ocean acidification. Observational and experimental studies show that OA alters the community structure of seaweed assemblages (Hepburn et al., ; Kroeker, Micheli, & Gambi, ; Porzio et al., ), where, under oligotrophic conditions, Phaeophytes tend to fare best and corallines, worst, under acidification (Enochs et al., ; Johnson, Russell, Fabricius, Brownlee, & Hall‐Spencer, ; Linares et al., ).…”

Tropicalisation of temperate reefs: Implications for ecosystem functions and management actions

“…This suggests that high latitude coral‐dominated reefs of the future may not form accreting reef frameworks (Perry & Alvarez‐Filip, ), and this may limit associated biodiversity. Ocean acidification may also limit corals by enhancing the competitive strength of turf and seaweeds generally (Connell & Russell, ; Diaz‐Pulido, Gouezo, Tilbrook, Dove, & Anthony, ) and of kelp in particular (Linares et al, ).…”

Molecular response of Sargassum vulgare to acidification at volcanic CO2 vents: insights from de novo transcriptomic analysis

“…Therefore, areas with natural CO 2 vents represent useful experimental systems to investigate the impact of OA on macroalgae in their natural ecosystem. Such sites have been discovered around the globe and few of them have already been used as a 'natural laboratory' to study elevated CO 2 /OA (Vizzini et al 2010;Lauritano et al 2015;Linares et al 2015).…”