The ocean and the atmosphere exchange massive amounts of carbon dioxide (CO2). The pre-industrial influx from the ocean to the atmosphere was 70.6 Gt C yr –1 , while the flux in the opposite direction was 70 Gt C yr –1 ( IPCC 2007 ). Since the Industrial Revolution an anthropogenic flux has been superimposed on the natural flux. The concentration of CO2 in the atmosphere, which remained in the range of 172–300 parts per million by volume (ppmv) over the past 800 000 years ( Lüthi et al. 2008 ), has increased during the industrial era to reach 387 ppmv in 2009. The rate of increase was about 1.0% yr –1 in the 1990s and reached 3.4% yr –1 between 2000 and 2008 ( Le Quéré et al. 2009 ). Future levels of atmospheric CO2 mostly depend on socio-economic parameters, and may reach 1071 ppmv in the year 2100 ( Plattner et al. 2001 ), corresponding to a fourfold increase since 1750. As pointed out over 50 years ago, ‘human beings are now carrying out a large scale geophysical experiment of a kind that could not have happened in the past nor be reproduced in the future’ ( Revelle and Suess 1957 ). Anthropogenic CO2 has three fates. In the years 2000 to 2008, about 29% was absorbed by the terrestrial biosphere and 26% by the ocean, while the remaining 45% remained in the atmosphere ( Le Quéré et al. 2009 ). The accumulation of CO2 in the atmosphere increases the natural greenhouse effect and generates climate changes ( IPCC 2007 ). It is estimated that the surface waters of the oceans have taken up 118 Pg C, or about 25% of the carbon generated by human activities since 1800 ( Sabine et al. 2004 ). By taking CO2 away from the atmosphere, the oceanic and terrestrial sinks mitigate climatic changes. Should their efficiency decrease, more CO2 would remain in the atmosphere, generating larger climate perturbations. This book has four main groups of chapters.
Cold-water coral ecosystems are more widespread, diverse and productive than previously thought. However, little is known about the interaction of deep-water corals with microorganisms. To understand whether coral species have specific prokaryotic communities, it is necessary to assess the within and between colony variability. This was studied based on 16S rRNA gene and denaturing gradient gel electrophoresis (DGGE) for one of the main cold-water corals Madrepora oculata at Rockall Bank off the coast of Ireland. We successfully applied a rapid, non-toxic and inexpensive method for extracting DNA for 16S rRNA gene fingerprinting of marine prokaryotic communities based on a heat and salt lysis with simultaneous salt extraction (HEATSALT). The within and between colony variability of the community composition of bacteria associated to the mucus and ectodermal tissue of M. oculata was then evaluated using a 16S rRNA gene PCR and DGGE approach. Bacterial community composition (BCC) clearly differed between living coral and reference samples (dead coral and surrounding water; 80% dissimilarity). A large within (35-40% dissimilarity between polyps) and between colony variability (ca. 50% dissimilarity) of BCC was detected. We also found preliminary evidence that BCC differed between M. oculata and Lophelia pertusa. The high intraspecific variability found has consequences for selecting sampling strategies when assessing bacterial diversity and refines the question of controlling mechanisms of bacterial diversity on corals. Sequencing of DGGE bands showed that Spongiobacter type phylotypes (STP) dominated the DGGE bands. STP of M. oculata were grouped together and were different from those detected in other corals and sponges. In addition, the high sequence diversity of STP suggests specific ecological roles and adaptations of this group in M. oculata. KEYWORDS: DNA extraction · Diversity · Spongiobacter · Lophelia pertusa Resale or republication not permitted without written consent of the publisher Contribution to the Theme Section 'Conservation and management of deep-sea corals and coral reefs'OPEN PEN
FIG. 1. The antFOCE experiment was deployed in 14m of water under sea ice at Casey Station, in East Antarctica. Mixing ducts 40m long were required to allow pH to equilibrate following the addition of CO 2 enriched seawater into the flow-through system.
Abstract. Free-ocean CO 2 enrichment (FOCE) systems are designed to assess the impact of ocean acidification on biological communities in situ for extended periods of time (weeks to months). They overcome some of the drawbacks of laboratory experiments and field observations by enabling (1) precise control of CO 2 enrichment by monitoring pH as an offset of ambient pH, (2) consideration of indirect effects such as those mediated through interspecific relationships and food webs, and (3) relatively long experiments with intact communities. Bringing perturbation experiments from the laboratory to the field is, however, extremely challenging. The main goal of this paper is to provide guidelines on the general design, engineering, and sensor options required to conduct FOCE experiments. Another goal is to introduce xFOCE, a community-led initiative to promote awareness, provide resources for in situ perturbation experiments, and build a user community. Present and existing FOCE systems are briefly described and examples of data collected presented. Future developments are also addressed as it is anticipated that the next generation of FOCE systems will include, in addition to pH, options for oxygen and/or temperature control. FOCE systems should become an important experimental approach for projecting the future response of marine ecosystems to environmental change.
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