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Due to ocean acidification and global warming, surface seawater of the western Baltic Sea is expected to reach an average of similar to 1100 mu atmpCO(2)and an increase of similar to 5 degrees C by the year 2100. In four consecutive experiments (spanning 10-11 weeks each) in all seasons within 1 year, the abiotic factors temperature (+5 degrees C abovein situ) andpCO(2)(adjusted to similar to 1100 mu atm) were tested for their single and combined effects on epibacterial communities of the brown macroalgaFucus vesiculosusand on bacteria present in the surrounding seawater. The experiments were set up in three biological replicates using the Kiel Outdoor Benthocosm facility (Kiel, Germany). Phylogenetic analyses of the respective microbiota were performed by bacterial 16S (V1-V2) rDNA Illumina MiSeq amplicon sequencing after 0, 4, 8, and 10/11 weeks per season. The results demonstrate (I) that the bacterial community composition varied in time and (II) that relationships between operational taxonomic units (OTUs) within an OTU association network were mainly governed by the habitat. (III) Neither singlepCO(2)norpCO(2):Temperature interaction effects were statistically significant. However, significant impact of ocean warming was detected varying among seasons. (IV) An indicator OTU (iOTU) analysis identified several iOTUs that were strongly influenced by temperature in spring, summer, and winter. In the warming treatments of these three seasons, we observed decreasing numbers of bacteria that are commonly associated with a healthy marine microbial community and-particularly during spring and summer-an increase in potentially pathogenic and bacteria related to intensified microfouling. This might lead to severe consequences for theF. vesiculosusholobiont finally affecting the marine ecosystem.

The pseudocolonial coral Lophelia pertusa (Scleractinia, Caryophylliidae) is a eury¬ba¬thic, steno¬ther¬mal cosmopolitan cold-water species. It occurs in two colour vari¬eties, white and red. L. pertusa builds vast cold-water coral reefs along the con¬tinental margins, which are among the most diverse deep-sea ecosystems. Micro¬biology of L. pertusa has been in scientific focus for only a few years. The question whether the coral holds a host-specific bac¬te¬rial commu¬nity is not finally answered. Possible implications of the two colour varieties for microbial colonisation must be taken into account. Bio imaging can reveal the in-situ location of bacterial groups on and possible interactions with the coral. The pre¬sent study aimed at investigating these aspects, drawing a more compre¬hen¬sive pic¬ture of commu¬nity struc¬ture, taxo¬no¬my, and in-situ location of L. pertusa-hosted microbes. Lophelia pertusa (Scleractinia, Caryophylliidae) ist eine eurybathe, stenotherme Kaltwasserkoralle. Sie tritt als rote und weiße Farbvarietät auf. L. pertusa bildet ausgedehnte Kaltwasserriffe entlang der Kontinentalränder, die zu den artenreichsten Lebensräumen der Tiefsee zählen. Die Mikro¬bio¬logie von L. pertusa steht erst seit wenigen Jahren im Fokus des wissenschaftlichen Interesses. Die Frage, ob die Koralle eine wirtsspezifische Bakteriengemeinschaft beherbergt, ist nicht end¬gül¬tig beantwortet. Mögliche Auswirkungen der unterschiedlichen Farbvarietäten auf die bak¬te¬ri¬elle Be¬sied¬lung der Koralle sind zu berücksichtigen. Bildgebende Verfahren können Auf¬schluss über die genaue Lage der Bakteriengruppen und mögliche Wechselwirkungen mit der Koralle ge¬ben. Ziel der dieser Arbeit ist es, diese Aspekte zu untersuchen und ein umfassen¬de¬res Bild der Struk¬tur, Taxo¬nomie und Ver¬tei¬lung der Bakteriengemeinschaft auf L. pertusa zu zeichnen.

Northeast Atlantic 2004 Cruise No. 61, Leg 1 April 19 to May 4, 2004, Lisbon – Cork