Sampling area and protocol
A total of 92 water samples were collected during October and November 2017 along the south coast of the Bird’s Head region of West Papua (500 km) across different habitats but mainly coral reefs (Fig. 1). Samples were collected in DNA-free plastic bags at the surface from a dinghy boat, at depths between 10 – 100m during close circuit rebreather dives, and (iii) at depths between 100 - 300m using Niskin water samplers. A pressure and temperature sensor was coupled to the Niskin bottle to control the sampling depth and characterize the water mass via the vertical temperature profile. For each sample, 2L of seawater were filtered with sterile Sterivex filter capsules (Merck© Millipore; pore size 0.22µm) using disposable sterile syringes. Immediately after, the filter units were filled with lysis conservation buffer (CL1 buffer SPYGEN©) and stored in 50 mL screw-cap tubes at -20°C. A contamination control protocol was followed in both field and laboratory stages ((27) Goldberg et al 2016; (26) Valentini et al. 2016). Water sample processing included the use of disposable gloves and single-use filtration equipment, and the bleaching (50% bleach) of Niskin water sampler.