Doing mantel test on each taxon

If I want to answer the question of which gut taxa are associated with a continuous biological variable of interest (eg serum data)- is it a proper use of mantel test to compute the distance matrix of each individual taxon and correlate it against the distance matrix of the response variable? Or am I better off doing an all-vs-all Spearman correlation on the abundance data (rarefied counts/relative abundance) itself (instead of the distance matrix) against the quantities of the variable of interest?