Abstract
Simple SummaryOcean acidification is causing major changes in marine ecosystems, with varying levels of impact depending on the region and habitat investigated. Here, we report noticeable changes in both meio- and macrobenthic assemblages at shallow hydrothermal vents located in the Mediterranean Sea. In general, the areas impacted by the vent fluids showed decrease in the abundance of several taxa and a shift in community composition, but with a clear biomass reduction evident only for macrofauna. CO2 emissions at shallow hydrothermal vents cause a progressive simplification of community structure and a general biodiversity decline due to the loss of the most sensitive meio- and macrofaunal taxa, which were replaced by the more tolerant groups, such as oligochaetes, or highly mobile species, able to escape from extreme conditions. Our results provide new insight on the tolerance of marine meio- and macrofaunal taxa to the extreme conditions generated by hydrothermal vent emissions in shallow-water ecosystems.The Aeolian Islands (Mediterranean Sea) host a unique hydrothermal system called the “Smoking Land” due to the presence of over 200 volcanic CO2-vents, resulting in water acidification phenomena and the creation of an acidified benthic environment. Here, we report the results of a study conducted at three sites located at ca. 16, 40, and 80 m of depth, and characterized by CO2 emissions to assess the effects of acidification on meio- and macrobenthic assemblages. Acidification caused significant changes in both meio- and macrofaunal assemblages, with a clear decrease in terms of abundance and a shift in community composition. A noticeable reduction in biomass was observed only for macrofauna. The most sensitive meiofaunal taxa were kinorhynchs and turbellarians that disappeared at the CO2 sites, while the abundance of halacarids and ostracods increased, possibly as a result of the larger food availability and the lower predatory pressures by the sensitive meiofaunal and macrofaunal taxa. Sediment acidification also causes the disappearance of more sensitive macrofaunal taxa, such as gastropods, and the increase in tolerant taxa such as oligochaetes. We conclude that the effects of shallow CO2-vents result in the progressive simplification of community structure and biodiversity loss due to the disappearance of the most sensitive meio- and macrofaunal taxa.
Highlights
The atmospheric carbon dioxide (CO2) concentration, due to anthropogenic activities, has increased from 280 ppm in preindustrial times to a present-day level of ~418 ppm [1].This increase results in dramatic effects within the oceanic realm, by reducing carbonate saturation of estuarine, coastal, and surface open-ocean waters [2] and expanding the volume of acidified seawater [3]
ocean acidification (OA) leads to a simplification of food webs with the trophic structure of the invertebrate community shifting to fewer trophic groups and the dominance by few generalists in low pH conditions [12]
Adaptation, and response to fluid emissions have been widely investigated in deep-sea hydrothermal vents, the response of meio- and macrofauna to CO2 volcanic emission at shallower (
Summary
The atmospheric carbon dioxide (CO2) concentration, due to anthropogenic activities, has increased from 280 ppm in preindustrial times to a present-day level of ~418 ppm [1].This increase results in dramatic effects within the oceanic realm, by reducing carbonate saturation of estuarine, coastal, and surface open-ocean waters [2] and expanding the volume of acidified seawater [3]. Previous investigations have been conducted at shallow submarine hydrothermal vents around active volcanoes (here referred to as hydrothermal CO2 seeps), where large amounts of CO2 are injected into seawater [4]. They showed different impacts of ocean acidification (OA) on marine life, especially on calcifying species such as corals [5], and on seagrasses, macroalgae [6,7], and meiofauna [8], which are fundamental in the benthic food-web, being responsible for the matter and energy transfer to higher trophic levels [9,10]. OA leads to a simplification of food webs with the trophic structure of the invertebrate community shifting to fewer trophic groups and the dominance by few generalists in low pH conditions [12]
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