2.1. Collection of precipitation and surface water samples
Daily precipitation samples (N = 512) were collected at the Base Crestones shelter (-83.480°, 9.460°, 3,400 m asl) on the Pacific slope of Chirripó using a passive collector (Palmex Ltd., Croatia). Samples were collected manually on every rainy day at 07:00 hr (−06:00 GMT). Lake water samples were collected at Lake Chirripó (-83.494°, 9.483°, 3,524 m asl, N= 48), Lake Ditkevi (-83.481°, 9.469°, 3,506 m asl, N= 66), and Morrenas Lakes (-83.486°, 9.492°, 3,495 m asl, N= 38) following a roughly biweekly sampling plan. Lake water samples were manually collected from about 20 cm below the surface and ~25 m away from surface stream inlets. Stream water (N= 74) was collected at several sites where surface water was flowing into the lakes or into the main channelized stream of CHRS (Talari River, -83.503°, 9.458°, 3,352 m asl).