Data associated with the study "Brilliantia kiribatiensis, a new genus and species of Cladophorales (Chlorophyta) from the remote coral reefs of the Southern Line Islands, Pacific Ocean". ITS.fasta, ITS_bmge.fasta, LSU.fasta, LSU_bmge.fasta, SSU.fasta, SSU_bmge.fasta: SSU rDNA, LSU rDNA and rDNA ITS sequences used in phylogenetic analyses. Sequences of Brilliantia kiribatiensis were added to updated phylogenetic datasets used previously (Leliaert et al. 2007a, Leliaert et al. 2009b), aligned in MAFFT v7.215 (Katoh and Standley 2013), and stripped of hypervariable sites in BMGE v1.1 (Criscuolo and Gribaldo 2010) by using the -h 0.4 -g 0.35 parameters. Alignments were visually checked and concatenated in Seaview v4.4.2. concatenated_SSU_ITS_LSU.fasta: concatenated alignment with following partitions: SSU: 1-1797, ITS1+5.8S+ITS2: 1798-3335, LSU: 3336-3926. Table_S1_sequence_sources.xls: GenBank accessions, sample isolate codes and sites of collection for sequences included in the concatenated phylogenetic data set. Table S2. Percent cover of different algal groups in 1 m2 photoquadrats. Algal groups are identified to genus level for fleshy macroalgae or functional group for turf algae, branched red algae, crustose coralline algae, and cyanobacteria. Table SX. Morphological measurements of Brilliantia kiribatiensis.