Relationship of human-associated microbial source tracking markers with Enterococci in Gulf of Mexico waters

► Human-specific MST methods were field tested at 5 laboratories across 4 states. ► Enterococci levels were correlated with MST marker detection in 4 regions. ► Enterococci levels correlated with exceedance of regulatory criteria in 3 regions. ► MST markers were frequently, but not always co-detected in water samples. ► Detailed SOPs and frequent communication reduced inter-laboratory variability.