The acidification of the oceans could potentially alter marine plankton communities with consequences for ecosystem functioning. While several studies have investigated effects of ocean acidifications on communities using traditional methods, few have used genetic analyses. Here, we use community barcoding to assess the impact of ocean acidification on the composition of a coastal plankton community in a large scale, in situ, long-term mesocosm experiment. High-throughput sequencing resulted in the identification of a wide range of planktonic taxa (Alveolata, Cryptophyta, Haptophyceae, Fungi, Metazoa, Hydrozoa, Rhizaria, Straminipila, Chlorophyta). Analyses based on predicted operational taxonomical units as well as taxonomical compositions revealed no differences between communities in high CO2 mesocosms (~760 µatm) and those exposed to present day CO2 conditions. Observed shifts in the planktonic community composition were mainly related to seasonal changes in temperature and nutrients.

Net (>200 µm 0.45 mm <200 µm) samples were taken from the mesocosms and the surrounding fjord.Mixed DNA samples were sequenced on an Illumina MiSeq platform using the paired end (2 x 300 bp) option.Pseudocalanus acuspes sequences were obtained by standard Sanger sequencing of the 18S and _cox_1 gene region.The allocation of OTUs (with assigned sequence reads) to the mesocosm and fjord samples can be found in the excel files.

Supplement to: Langer, Julia A F; Sharma, Rahul; Schmidt, Susanne I; Bahrdt, Sebastian; Horn, Henriette G; Algueró-Muñiz, Maria; Nam, Bora; Achterberg, Eric Pieter; Riebesell, Ulf; Boersma, Maarten; Thines, Marco; Schwenk, Klaus (2016): Community barcoding reveals little effect of ocean acidification on the composition of coastal plankton communities: evidence from a long-term mesocosm study in the Gullmar Fjord, Skagerrak. PLoS ONE