Table 1.

Description of the datasets

	OTUs	OTUs (%)	Sequence abundance (%)*
All OTUsa	2926	100	100
Bacteria	1561	53.3	50.7
Protists	1365	46.7	49.3
Resident microbiotab	709	100	100 (85)
Bacteria	354	49.9	53.6
Protists	355	50.1	46.4
Core microbiotac	259	100	64.5 (54)
Bacteria	182	70.3	46.3
Protists	77	29.7	18.2
Picoplankton	109	42.1	32.4
Nanoplankton	150	57.9	32.1
Protists
Heterotroph	5	1.9	0.3
Photoautotroph	37	14.3	11.8
Parasite	21	8.1	3.5
Mixotroph	3	1.2	0.7
Symbiont	1	0.4	0.1
Unknown	11	4.3	2.0
Bacteria
Photoautotroph (cyanobacteria)	19	7.3	19.3
Non-photoautotrophd	163	62.5	26.8
Seasonal preference core OTUs
Winter	156	60.2	21.8
Spring	24	9.3	16.4
Summer	44	17.0	8.2
Autumn	30	11.6	13.7
No seasonality	5	1.9	4.5
Seasonal subnetworks
Winter	156	60.2	21.8
Spring	19	7.3	13.7
Summer	41	15.8	6.6
Autumn	26	10.0	12.9

^*In italics the abundances relative to all OTUs are indicated. All other values in normal text indicate abundances relative to OTUs in the resident microbiota

^aNumber of OTUs in the full dataset that was left after quality control and rarefaction, which were present in at least 10% of the samples (i.e., 12 months, not necessarily consecutive)

^bOTUs present in at least 30% of the samples (i.e., 36 months, not necessarily consecutive) [= Resident microbiota]

^cOTUs included in the core network (core microbiota) with significant correlations (p < 0.001), local similarity scores > |0.7| and Spearman correlations > |0.7|, being present in at least 30% of the samples

^dIncludes non-photoautotrophic lifestyles (i.e., chemoautotrophs, photoheterotrophs, chemoheterotrophs, etc.)