Ocean Acidification Induces Changes in Virus-Host Relationships in Mediterranean Benthic Ecosystems.

Roberto Danovaro,Francesca Ape,Franco Andaloro,Michael Tangherlini,Silvestro Greco,Cinzia Corinaldesi,Teresa Romeo

doi:10.3390/microorganisms9040769

Abstract

Acidified marine systems represent “natural laboratories”, which provide opportunities to investigate the impacts of ocean acidification on different living components, including microbes. Here, we compared the benthic microbial response in four naturally acidified sites within the Southern Tyrrhenian Sea characterized by different acidification sources (i.e., CO2 emissions at Ischia, mixed gases at Panarea and Basiluzzo and acidified freshwater from karst rocks at Presidiana) and pH values. We investigated prokaryotic abundance, activity and biodiversity, viral abundance and prokaryotic infections, along with the biochemical composition of the sediment organic matter. We found that, despite differences in local environmental dynamics, viral life strategies change in acidified conditions from mainly lytic to temperate lifestyles (e.g., chronic infection), also resulting in a lowered impact on prokaryotic communities, which shift towards (chemo)autotrophic assemblages, with lower organic matter consumption. Taken together, these results suggest that ocean acidification exerts a deep control on microbial benthic assemblages, with important feedbacks on ecosystem functioning.

Highlights

Over the last two hundred years, anthropogenic activities have led to the continuous increase in the concentration of atmospheric carbon dioxide (CO2 ), from 280 ppm in preindustrial times to a present-day level of ~400 ppm [1,2,3,4,5]
The results provided by those studies might be of limited support to research on the effects of ocean acidification, as either: (i) they mostly focus on the water column, lacking information on benthic environments, which provide a wide array of ecosystem services [15,16,17], (ii) the results were diverging and hard to reconcile, suggesting that the high variability in responses and shifts in prokaryotic assemblage structure and functional responses might be related to the environmental complexity of naturally acidified sites [15,18] and (iii) they were based on laboratory experiments, which do not reflect the real ecosystem dynamics underlying natural assemblages or include few sampling points [6,8,16,19]
Sampling sites within the Ischia area were characterized by sandy sediments, whereas those within the Presidiana area were characterized by a coarser sediment texture

Summary

Introduction

Over the last two hundred years, anthropogenic activities have led to the continuous increase in the concentration of atmospheric carbon dioxide (CO2 ), from 280 ppm in preindustrial times to a present-day level of ~400 ppm [1,2,3,4,5]. Atmospheric CO2 dissolves in seawater, leading to increased concentrations of inorganic carbon in the oceans with a corresponding reduction in mean surface seawater pH, a process called ocean acidification (OA) [4,5,6,7,8] This process, coupled with ocean warming [9], poses significant threats to ocean life and ecosystem functioning on a global scale, such as mass mortalities and spread of pathogenic or invasive species, both in surface waters and in the deep ocean. Those studies showed that volcanic CO2 venting can provide important evidence on the role and impact of pH reduction on prokaryotic-mediated activities (e.g., organic matter degradation, nitrogen fixation and nitrification) [5,7,14] and have an impact on prokaryotic diversity (in terms of both alpha-diversity and assemblage structure) [5,6]

Methods

Results

Discussion

Conclusion