Table 3. Core and abundant OTUs found in the Porphyra umbilicalis microbiome identified using V8 (Taxonomic level 2 = phylum, 3 = class, 4 = order, 5 = family, 6 = genus).

A. Core Microbiomea
Tax level	Taxon	No. of OTUs	OTU code number
2	Bacteroidetes	7
3	Sphingobacteria	4
5	Saprospiraceae	4	1982(F)*, 2434(E)*, 2521(W)**, 2525(E)*
3	Flavobacteria	2
5	Flavobacteriaceae	2	2410(F)*, 2427(W)*
3	Unclassified	1	2387(W)
2	Chloroflexi	1	2493(E)*
2	Proteobacteria	5
3	Gammaproteobacteria	1
6	Granulosicoccus	1	2408(W)*
3	Alphaproteobacteria	4
5	Hyphomonadaceae	1	2494(W)* L
5	Rhodobacteraceae	1	2225(E)* L
5	Unclassified	2	1933(E), 2219(W)*
B. Lab: Most abundant OTUsb
Tax level	Taxon	No. of OTUs	OTU code number
2	Bacteroidetes	3
3	Sphingobacteria	1
5	Saprospiraceae	1	2521
3	Flavobacteria	2
5	Flavobacteriaceae	2	2367, 2427
2	Planctomycetes	1	1352
2	Proteobacteria	4
3	Gammaproteobacteria	1
5	Alteromonadaceae	1	2182
3	Alphaproteobacteria	1
5	Rhodobacteraceae	1	2225
5	Sphingomonadaceae	1
6	Sphingopyxis	1	1938
C. Field: Most abundant OTUsc
Tax level	Taxon	No. of OTUs	OTU code number
2	Bacteroidetes	9
3	Sphingobacteria	9
4	Sphingobacteriales	3	1875, 2381, 2383
5	Saprospiraceae	4	2434, 2497, 2521, 2525
6	Lewinella	2	2302, 2475
3	Flavobacteria	1
5	Flavobacteriaceae	1	2410
3	Unclassified	1	2435
2	Proteobacteria	1
3	Alphaproteobacteria	1	2514
2	Unclassified (Bacteria)	3	2489, 2500, 2524

^a13 OTUs (0.03 distance) found across fall, winter & lab groups.

^*present at≥1% of all sequences on at least one blade (n = 12)

^{* L}≥1% on a lab blade

^**present at ≥1% on all 12 blades

^bOTUs (0.03 distance) with sequence abundance greater than 1% on both lab blades

^cOTUs (0.03 distance) with sequence abundance greater than 1% on at least 3 of the 10 winter (n = 5) and fall (n = 5) blades; underlined OTUs present on at least 5 of 10 blades; OTU 2521 present on all.

Designations of F = Fall, E = Evenly distributed between fall and winter, W = Winter refer to a ≥3× skew in sequence abundance toward that group.