Deep sequencing uncovers protistan plankton diversity in the Portuguese Ria Formosa solar saltern ponds
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We used high-throughput sequencing to unravel the genetic diversity of protistan (including fungal) plankton in hypersaline ponds of the Ria Formosa solar saltern works in Portugal. From three ponds of different salinity (4, 12 and 38 %), we obtained ca. 105,000 amplicons (V4 region of the SSU rDNA). The genetic diversity we found was higher than what has been described from solar saltern ponds thus far by microscopy or molecular studies. The obtained operational taxonomic units (OTUs) could be assigned to 14 high-rank taxonomic groups and blasted to 120 eukaryotic families. The novelty of this genetic diversity was extremely high, with 27 % of all OTUs having a sequence divergence of more than 10 % to deposited sequences of described taxa. The highest degree of novelty was found at intermediate salinity of 12 % within the ciliates, which traditionally are considered as the best known and described taxon group within the kingdom Protista. Further substantial novelty was detected within the stramenopiles and the chlorophytes. Analyses of community structures suggest a transition boundary for protistan plankton between 4 and 12 % salinity, suggesting different haloadaptation strategies in individual evolutionary lineages as a result of environmental filtering. Our study makes evident the gaps in our knowledge not only of protistan and fungal plankton diversity in hypersaline environments, but also in their ecology and their strategies to cope with these environmental conditions. It substantiates that specific future research needs to fill these gaps.
KeywordsHypersaline Novel diversity Protistan plankton Salt gradient Solar saltern
We would like to thank A. M. Amaral, J. Reis and R. Costa from CCMAR for their help and support during the sampling period in Faro, Portugal. We appreciate the permission and support of the Ria Formosa salt works staff for sampling. We also thank R. Müller for writing the script to merge the output files from QIIME and JAguc, L. Bittner and D. Forster for help with QIIME and R and the anonymous reviewers for constructive comments. This research was funded by an ASSEMBLE grant to TS and SF and the Deutsche Forschungsgemeinschaft (DFG) grant STO414/3-2.
Conflict of interest
The authors declare that they have no conflict of interest.
All performed experiments comply with the current laws of our country.
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