*2.1. Study Site*

The Langenuen Fjord in southwestern Norway, south of Bergen (Figure 1), is a 35 km long north-south trending water passage connecting the Korsfjorden with the Hardangerfjord. The system opens up to the Atlantic through Korsfjorden at its northern edge, through Selbjørnsfjorden in the central parts, and through Bømlafjorden at its southern end. Langenuen is ~300 m deep. The deepest point measures 568 m and is located in the northern portion between the islands of Huftarøy and Reksteren. The average width of the fjord is 2.9 km in the northern section and 1.7 km in the southern section. The fjord acts as an ocean water inlet to the Hardangerfjord [59]. It hosts several *L. pertusa*-dominated CWC reefs on the eastern side of the fjord, at depths between 80 and 240 m [60,61]. This study concentrates on five of them in two different settings: corals covering an elevated topographic feature on the fjord bottom here called "bank reef" and corals living on steep walls or cliffs, "wall reefs". The two bank reefs are Nakken (NK, 59.830◦ N, 5.550◦ E) and the northernmost site Bekkjarvik (BV, 59.983◦ N, 5.276◦ E). The southernmost site Huglhammaren near the main sill of the Hardangerfjord (HH, 59.815◦ N, 5.590◦ E), Straumsneset (SN, 59.941◦ N, 5.467◦ E), and Hornaneset (HN, 59.890◦ N, 5.539◦ E) are wall reefs on the near-vertical fjord wall. Sites NK and SN are previously described by Fosså et al. (2015) [60].
