Table 2.

Description of samples for each analysis grouping.

Analysis grouping	Analysis grouping/Figure	Number of samples	Subsampled sequence depth range	Oligotypes before (after) quality filtering	Percentage of reads represented by top 5% (10%) oligotypes	Components (position in alignment)
All substrates	1	104	83–30,000	882 (74)	76 (94)	13, 15, 20, 21, 22, 23, 25, 31, 32, 45, 50, 55
Plastics and surrounding seawater	2C	71	83–13,359	415 (71)	90 (96)	13, 15, 20, 21, 22, 23, 25, 31, 32, 45, 50, 55
Sponges and surrounding seawater	2B	58	1822–10,000	681 (45)	71 (90)	13, 15, 20, 21, 22, 23, 25, 31, 32, 45, 50, 55
Fish and surrounding water	2A	51	636–85,000	604 (21)	80 (97)	13, 15, 20, 21, 22, 23, 25, 31, 32, 45, 50, 55
Mixed habitat	4	179	83–20,000	1452 (99)	65 (90)	13, 15, 20, 21, 22, 23, 25, 31, 32, 37, 45, 50, 55

Some samples were included in more than a single grouping.