Short 18S amplicons from Nam Co sediment core (C8, 2019). Primers for ostracods 18SV4osF (GCT CGT AGT TGG ATC TCA GT) 18SV4osRs (TYG CCT GCT TTR AGC ACT C).
The total PCR mix volume per sample was 50 l and consisted of 10 l Hot Start FirePol Master Mix (Solis BioDyne, Estonia), 1 l of forward and reverse primer (10 M), and a template DNA concentration of 4 ng/ml. The rest of the volume was filled with nuclease-free water. PCR cycling conditions were as follows: 95 C for 15 min; 50 cycles of 98 C for 20 s, 54 C for 45 s, and 72 C for 1 min; with a final extension at 72 C for 5 min. Two uniquely indexed PCR replicates per sample were amplified and checked using a gel electrophoresis with 5 l PCR product on a 1 % agarose gel. The MinElute PCR Purification Kit (Qiagen, Germany) was used for the purification of all PCR products, following the manufacturers protocol. Samples were pooled equimolarly for sequencing on an Illumina NextSeq 550 system, using the high-output kit to generate 2 x 150 bp paired-end reads.