Abstract
One of the most important pieces of climate change evidence is ocean acidification. Acidification effects on marine organisms are widely studied, while very little is known regarding its effects on assemblages’ β-diversity. In this framework, shallow hydrothermal vents within a Marine Protected Area (MPA) represent natural ecosystems acting as laboratory set-ups where the continuous carbon dioxide emissions affect assemblages with consequences that can be reasonably comparable to the effects of global water acidification. The aim of the present study is to test the impact of seawater acidification on the β-diversity of soft-bottom assemblages in a shallow vent field located in the Underwater Archeological Park of Baia MPA (Gulf of Naples, Mediterranean Sea). We investigated macro- and meiofauna communities of the ‘Secca delle fumose’ vent system in sites characterized by sulfurous (G) and carbon dioxide emissions (H) that are compared with control/inactive sites (CN and CS). Statistical analyses were performed on the most represented macrobenthic (Mollusca, Polychaeta, and Crustacea), and meiobenthic (Nematoda) taxa. Results show that the lowest synecological values are detected at H and, to a lesser extent, at G. Multivariate analyses show significant differences between hydrothermal vents (G, H) and control/inactive sites; the highest small-scale heterogeneities (measure of β-diversity) are detected at sites H and G and are mainly affected by pH, TOC (Total Organic Carbon), and cations concentrations. Such findings are probably related to acidification effects, since MPA excludes anthropic impacts. In particular, acidification markedly affects β-diversity and an increase in heterogeneity among sample replicates coupled to a decrease in number of taxa is an indicator of redundancy loss and, thus, of resilience capacity. The survival is assured to either tolerant species or those opportunistic taxa that can find good environmental conditions among gravels of sand.
Highlights
All biological systems have general properties that, coherently with environmental conditions, modify their structures in order to maximize resources exploitation tending to an equilibrium state
We studied β-diversity as small-scale spatial heterogeneity of meio- and macrobenthic communities inhabiting the soft bottoms of a shallow hydrothermal vents area, and tested if we can consider β-diversity a measure of resilience capacity in acidified seawater environment
The present study aims at detecting the possible effects of hydrothermal vents, located within an Marine Protected Area (MPA), on β-diversity of soft-bottom meiobenthic and macrobenthic assemblages
Summary
All biological systems have general properties that, coherently with environmental conditions, modify their structures in order to maximize resources exploitation tending to an equilibrium state (climax). Many coastal ecosystems are composed of species that are critical for supporting biodiversity, ecosystem function [7], and a suite of critical ecosystem services [8,9] Nowadays, they are at risk of disappearing since climate changes are often faster than species/communities resilience capacity [10,11,12,13] and they have no time to modify themselves in order to reach a climax state. They are at risk of disappearing since climate changes are often faster than species/communities resilience capacity [10,11,12,13] and they have no time to modify themselves in order to reach a climax state Investigations on these systems are often a challenge since it is difficult to disentangle the effects of climate change and anthropic impact on assemblage structure. In the case of Marine Protected Areas, we can exclude anthropic activities as a cause of assemblage modifications
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