Table 1. Number of reads, observed fungal OTUs, expected fungal OTUs (Chao1), Coverage (Good’s coverage) and Shannon’s index in seawater and sponge samples at a 97% sequences similarity threshold.

Sample name	Abbreviation	Total no. of quality-filtered reads	No. of fungal reads	Observed fungal OTUs	Expected OTUs (Chao1) ± SE (sub-sampled)	Good’s coverage (sub-sampled)	Shannon’s index (sub-sampled)
C. concentrica 1 2014	C_1_14	16,199	14,849	8	3 ± 0	1.00	0.09
C. concentrica 2 2014	C_2_14	3,026	1,120	4	3 ± 0	1.00	0.90
C. concentrica 3 2014	C_3_14	6,198	4,808	4	1 ± 0	1.00	0.00
C. concentrica 1 2016	C_1_16	6,578	269	24	28 ± 18	0.97	1.94
C. concentrica 2 2016	C_2_16	21,700	3,437	27	10 ± 3	0.99	0.63
C. concentrica 3 2016	C_3_16	9,483	320	30	44 ± 35	0.94	2.07
Scopalina sp. 1 2014	S_1_14	1,532	49	2	NA	NA	NA
Scopalina sp. 2 2014	S_2_14	7,071	12	3	NA	NA	NA
Scopalina sp. 3 2014	S_3_14	1,992	107	4	NA	NA	NA
Scopalina sp. 1 2016	S_1_16	4,859	444	29	27 ±15	0.97	1.33
Scopalina sp. 2 2016	S_2_16	3,281	206	32	NA	NA	NA
Scopalina sp. 3 2016	S_3_16	24,565	665	36	39 ± 50	0.96	1.38
T. anhelans 1 2014	T_1_14	681	681	2	2 ± 1	1.00	0.03
T. anhelans 2 2014	T_2_14	6,947	6,703	9	5 ± 4	1.00	0.96
T. anhelans 3 2014	T_3_14	64	8	3	NA	NA	NA
T. anhelans 1 2016	T_1_16	19,481	18,300	21	5 ± 4	1.00	1.21
T. anhelans 2 2016	T_2_16	16,379	6,947	27	9 ± 17	0.99	0.77
T. anhelans 3 2016	T_3_16	30,977	30,956	19	3 ± 2	1.00	0.72
Seawater 1 2014	SW_1_14	1,066	2	2	NA	NA	NA
Seawater 2 2014	SW_2_14	3,379	3,314	2	2 ± 1	1.00	0.03
Seawater 3 2014	SW_3_14	2,647	1,588	3	1 ± 0	1.00	0.00
Seawater 1 2016	SW_1_16	6,139	3,379	33	12 ± 8	1.00	2.05
Seawater 2 2016	SW_2_16	12,439	5,576	45	21 ± 9	0.98	2.37
Seawater 3 2016	SW_3_16	25,069	19,496	40	14 ± 18	0.99	1.24