Table 1 Species ID, number of MAG per species (in parenthesis), approved names of the species and genera of the RCA cluster, the location of the MAGs used for denomination, mean genome size ± standard deviation (SD), mean number of coding sequences (CDS) ± SD and mean G + C content ± SD of 13 RCA species

Species C1 (3)

Cand norwegica

Planktomarina

Arctic Ocean

1.91 ± 0.17

2.44 ± 0.14

1754.7 ± 170.6

48.56 ± 0.2

Species C2 (1)

Cand australis

Southern Ocean, ANT28-4, station 241

2.32

3.12

2122.0

46.36

Species C3 (14)

forsetii^a

North Sea, Helgoland

2.31 ± 0.28

2.64 ± 0.22

2208.9 ± 294.7

52.00 ± 0.5

Species C4 (8)

arctica^a

Arctic Ocean

2.30 ± 0.13

2.85 ± 0.19

2144.3 ± 131.5

47.91 ± 0.1

Species C5 (7)

antarctica^a

Southern Ocean, ANT28-4, station 241

2.60 ± 0.85

3.12 ± 0.18

2426.6 ± 90.1

47.96 ± 0.1

Species C6 (6)

temperata

North Sea, type strain

3.09 + 0.29

3.09 + 0.29

3040.5 ± 329.8

53.70 ± 0.9

Species C7 (2)

Cand atlantica

Atlantic SW

2.17 ± 0.65

2.49 ± 0.15

2104.5 ± 60.1

53.55 ± 0.0

Species C8 (1)

Cand helgolandica

North Sea, Helgoland

2.18

2.92

2112

53.22

Species B1 (2)

Cand australis

Pseudoplanktomarina^a

Southern Ocean, ANT28-4, station 241

1.97 ± 0.52

2.36 ± 0.12

1844.5 ± 37.5

43.69 ± 0.1

Species B2 (23)

karensis^a

Arctic Ocean

2.17 ± 0.11

2.34 ± 0.11

2042.3 ± 50.0

43.72 ± 0.1

Species B3 (9)

bipolaris^a

Southern Ocean, ANT28-4, station 241

1.86 ± 0.14

2.26 ± 0.08

1707.6 ± 117.8

44.10 ± 0.1

Species B4 (9)

atlantica^a

Atlantic Ocean

2.20 ± 0.19

2.72 ± 0.12

2013.9 ± 180.5

42.22 ± 0.2

Species A1 (2)

Cand aphotica

Paraplanktomarina

Arctic Ocean

1.93 ± 0.21

2.40 ± 0.11

1774.5 ± 195.9

45.85 ± 0.0