“…Thus, the observed decrease in relative nifH gene copy numbers, i.e., relative diazotroph abundances, with increasing water depth may indeed be linked to reduced photosynthate translocation by Symbiodiniaceae (Lesser et al, 2007;Bednarz et al, 2018). Other studies have reported increased dependence on heterotrophy by coral holobionts with increasing water depth, decreasing temperature and/or light availability (Anthony and Fabricius, 2000;Palardy et al, 2008;Einbinder et al, 2009;Ferrier-Pagès et al, 2011;Godinot et al, 2011;Mies et al, 2018;Williams et al, 2018). Thereby, heterotrophy could provide the coral holobiont with a large part of its nutrient demand at these greater depths (Houlbrèque and Ferrier-Pagès, 2009;Lesser et al, 2010;Wijgerde et al, 2011;Burmester et al, 2018).…”