Conservation management of marine biodiversity depends on biomonitoring of marine habitats, but current approaches are resource‐intensive and require different approaches for different organisms. Environmental DNA (eDNA) extracted from water samples is an efficient and versatile approach to detecting aquatic animals. In the ocean, eDNA composition reflects local fauna at fine spatial scales, but little is known about the effectiveness of eDNA‐based monitoring of marine communities at larger scales. We investigated the potential of eDNA to characterize and distinguish marine communities at large spatial scales by comparing vertebrate species composition among marine habitats in Qatar, the Arabian Gulf (also known as the Persian Gulf), based on eDNA metabarcoding of seawater samples. We conducted species accumulation analyses to estimate how much of the vertebrate diversity we detected. We obtained eDNA sequences from a diverse assemblage of marine vertebrates, spanning 191 taxa in 73 families. These included rare and endangered species and covered 36% of the bony fish genera previously recorded in the gulf. Sites of similar habitat type were also similar in eDNA composition. The species accumulation analyses showed that the number of sample replicates was insufficient for some sampling sites but suggested that a few hundred eDNA samples could potentially capture >90% of the marine vertebrate diversity in the study area. Our results confirm that seawater samples contain habitat‐characteristic molecular signatures and that eDNA monitoring can efficiently cover vertebrate diversity at scales relevant to national and regional conservation and management. Article impact statement: Environmental DNA provides habitat‐characteristic molecular signatures and can be used efficiently to map marine biodiversity at large spatial scales. This article is protected by copyright. All rights reserved

10 páginas, 3 tablas, 1 figuraCoastal ocean acidification is expected to interfere with the physiology of marine bivalves. In this work, the effects of acidification on the physiology of juvenile mussels Mytilus galloprovincialis were tested by means of controlled CO2 perturbation experiments. The carbonate chemistry of natural (control) seawater was manipulated by injecting CO2 to attain 2 reduced pH levels: −0.3 and −0.6 pH units as compared with the control seawater. After 78 d of exposure, we found that the absorption efficiency and ammonium excretion rate of juveniles were inversely related to pH. Significant differences among treatments were not observed in clearance, ingestion and respiration rates. Coherently, the maximal scope for growth and tissue dry weight were observed in mussels exposed to the pH reduction ΔpH = −0.6, suggesting that M. galloprovincialis could be tolerant to CO2 acidification, at least in the highly alkaline coastal waters of Ria Formosa (SW Portugal).This is a contribution to the ‘The integrated\ud impacts of marine acidification, temperature and precipitation\ud changes on bivalve coastal biodiversity and fisheries:\ud how to adapt?’ project, which is part of the CIRCLE\ud Med projects, funded by the Regional Ministry of Innovation\ud and Industry of the Galician Government (08MDS\ud 018402PR), the Italian Ministry for Environment, Land and\ud Sea, and the Foundation for Science and Technology of\ud Portugal (ERA-CIRCLE/0004/2007), in the framework of the\ud Circle ERA Net project (which is funded by the European\ud Commission 6th Framework Programme).Peer reviewe

9 páginas, 3 tablas, 1 figuraEffects of coastal ocean acidification, other than calcification, were tested on juvenile\ud clams Ruditapes decussatus during a controlled CO2 perturbation experiment. The carbonate chemistry\ud of natural (control) seawater was manipulated by injecting CO2 to attain 2 reduced pH levels\ud (–0.4 and –0.7 pH units) as compared with the control seawater. After 87 d of exposure, we found that\ud the acidification conditions tested in this experiment significantly reduced the clearance, ingestion\ud and respiration rates, and increased the ammonia excretion rate of R. decussatus seeds. Reduced\ud ingestion combined with increased excretion is generally associated with a reduced energy input,\ud which will likely contribute to a slower growth of the clams in a future high CO2 coastal ocean. These\ud results emphasize the need for management policies to mitigate the adverse effects of global change\ud on aquaculture, which is an economically relevant activity in most coastal areas worldwide.This is a contribution to the\ud ACIDBIV project, which is part of the CIRCLE Med projects,\ud funded by the Regional Ministry of Innovation and Industry of\ud the Galician Government (08MDS018402PR), the Italian Ministry\ud for Environment, Land and Sea, and the Foundation for\ud Science and Technology of Portugal (ERA-CIRCLE/0004/\ud 2007), in the framework of the Circle ERA Net project (which\ud is funded by the European Commission 6th Framework\ud Programme).Peer reviewe