Labile molecules are more likely to be preserved in crab burrows under climate regulation. Cascading relationships of DOM marks with environmental factors. The best-supported structural equation models showed major pathways of the influences of environmental factors on NOSC and AI_mod in the (a, c) sediment matrix and (b, d) crab burrows, respectively. Single-headed arrows indicate the hypothesized direction of causation, and df means degree-of-freedom. Numbers on the red (i.e., positive relationships) and blue (i.e., negative relationships) arrows indicate significant standardized path coefficients at p < 0.05, whereas dotted arrows indicate insignificant pathways. The numbers adjacent to the arrows are standardized path coefficients that reflect the effect size of the relationship. The goodness-of-fit statistics for the model are presented below. Heatmap of correlations (r) between environmental variants and different fractions of Fe and Mn minerals in (e) sediment matrix and (f) crab burrows. *, **, and *** indicate significant correlation between environmental variants and the minerals at p < 0.05, p < 0.005, and p < 0.001, respectively.