Table S1. Physicochemical profiles of three spatial Groups and community sample mapping								
"Physicochemical measurements are available as three Group-level profiles, not seven independently matched environmental measurements. Values are descriptive only. Microhabitat Type and Group are incompletely crossed; this table does not identify environmental effects."								
								
Group	Temperature (??C)	pH	DO (mg/L)	EC (?S/cm)	ORP (mV)			
1st	17.9	2.47	1.33	2760	448.7			
2nd	15.6	2.79	2.27	2048	487.6			
3rd	17	2.52	2.02	1361	534.5			
								
"Each Group-level profile is shown once. No environmental correlation matrix, Mantel/envfit result or physicochemically constrained ordination output is reported."								
Mapping of the seven microbial-community samples to spatial Group and microhabitat Type								
Sample	Group	Type					seq_ID	analysis_name
1st_BFP	1st	AMD precipitate-associated biofilm					IG-2P	1st_G
1st_BFW1	1st	wall-attached biofilm					IG-2PW	1st_BF1
1st_BFW2	1st	wall-attached biofilm					IG-W2	1st_BF2
2nd_BFP	2nd	AMD precipitate-associated biofilm					IG-1P	2nd_G
2nd_BFW	2nd	wall-attached biofilm					IG-W1	2nd_BF
2nd_wt	2nd	water					IG-WAT-1	2nd_wt
3rd_wt	3rd	water					IG-WAT-R	3rd_wt
								
Mapping rows describe sample identities and do not add environmental replication. Alpha-diversity and Type-constrained ordination results are reported separately in their dedicated tables.