Increases in atmospheric carbon dioxide (CO2) change ocean chemistry, as dissolved CO2 leads to a reduction in the seawater pH. Many marine taxa have been shown to be affected by ocean acidification; however, information on marine fungi is lacking. We analyzed the effect of pH on mycoplankton communities. The pH of microcosms was adjusted to a value mimicking the predicted ocean acidification in the near future. Fungal communities were analyzed using a double-marker gene approach, allowing a more detailed analysis of their response using 454 pyrosequencing. Mycoplankton communities in microcosms with in situ and adjusted water pH values differed significantly in terms of structure and diversity. The differences were mainly abundance shifts among the dominant taxa, rather than the exclusion of fungal groups. A sensitivity to lower pH values was reported for several groups across the fungal kingdom and was not phylogenetically conserved. Some of the fungal species that dominated the communities of microcosms with a lower pH were known pathogenic fungi. With the increasing awareness of the significant role fungi play in marine systems, including performing a diverse range of symbiotic activities, our results highlight the importance of including fungi in further research projects studying and modeling biotic responses to the predicted ocean acidification.

In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Gattuso et al, 2016) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI). The date of carbonate chemistry calculation by seacarb is 2017-08-22.

Supplement to: Reich, Marlis; Wichels, Antje; Panzer, Katrin; Krause, Evamaria; Giménez, Luis; Gerdts, Gunnar (2017): Impacts of a reduction in seawater pH mimicking ocean acidification on the structure and diversity of mycoplankton communities. Aquatic Microbial Ecology, 79(3), 221-233