Abstract Metallothionein-like protein concentrations (MT) and three functionally defined fractions of cholinesterase activity (ChE: total, eserine-sensitive, eserine-resistant) were quantified in gill and digestive gland homogenates of tropical cup oysters from 5 nearshore locations in the Colombian Caribbean and correlated with sediment and tissue metal (9 metals) and pesticide (22 organophosphates, OPs, and 20 organochlorines- OCPs), as well as water physical-chemical parameters (salinity, pH, temperature and dissolved oxygen). Tissue and sediment pesticide concentrations were below detection limits in all samples, whereas sediment and tissue metal concentrations exceeded environmental thresholds at several locations. Tissue MT and ChE biomarkers varied by a factor of 5-6 between locations and correlated with tissue and sediment concentrations. However, statistically significant covariance between biomarkers and water chemistry parameters was also observed, indicating that both, metal concentrations and physical-chemical variables, are likely to be responsible for generating the observed spatial-temporal variations in biomarker patterns.