Fig. 1

Location of Ace Lake, Ellis Fjord, and Taynaya Bay in the Vestfold Hills, East Antarctica. Ace Lake (68° 28′ S, 78° 11′ E) is 25 m deep with a strong halocline and chemocline that coincides with the oxic-anoxic interface at a depth of 12–15m, and supports the growth of a microbial community that was derived from the Southern Ocean about 5,000 years ago [19, 27, 29, 30]. Ellis Fjord (68° 36′ S, 78° 07′ E) is an ~ 10-km-long, narrow water inlet that contains six basins (EF1–EF6) that are up to 117 m deep, with the two inner basins (EF1 and EF2) being meromictic [31]. The sill at the entrance to Ellis Fjord is 4 m deep and the six marine basins are separated by sills of different depths (1–30 m) [8, 29, 31, 32]. Taynaya Bay (68° 27′ S, 78° 17′ E) is a marine water inlet with a maximum depth of up to 80 m, containing six basins, of which five (Burke and TB1–TB4) are meromictic [29, 31]. Ace Lake and Taynaya Bay Basin 1 are ~ 2 km apart, and Ellis Fjord Basin 2 is ~ 14 km to the west of Ace Lake. All three systems are covered by ice for much of the year. The satellite map of the Vestfold Hills and the distance measurements were produced using the interactive atlas available on Landsat Image Mosaic of Antarctica website [33]. The locations of Ellis Fjord and Taynaya Bay basins were from published data [29, 31]. The photos of the aquatic systems were taken by Sarah Brazendale and Rick Cavicchioli