The marine shrimp Litopenaeus vannamei were used as an active biomonitoring organism to assess the bioavailability and impact of metal contaminants in seven study sites along the Maluan Bay of China. Metal concentrations in the hepatopancreas of shrimps were determined in conjunction with four biomarkers responses after a 7 day in situ cage exposures. The results showed that contaminant tissue burdens at the deployment sites were greater than those of the reference site, and antioxidant enzyme activities were strongly inhibited compared to those of reference organisms. Variations in these biomarker responses were correlated significantly (p < 0.05 or p < 0.01) with the specific metal pollutants at the study sites, but no significant correlations existed between catalase activity responses and the metal contaminants. This suggests the presence of undetermined contaminants or other exposure routes that may be responsible for the decreased catalase activity. Multivariate analysis revealed a causal relationship between contaminants at each deployment site and the biochemical “response” of the caged shrimps at these sites and demonstrated the presence of two contaminant “hot” spots. This investigation suggested that the incorporation of chemical data on trace metal concentrations with the analysis of antioxidant enzymatic activities in caged shrimps can be a useful tool for the identification of causal toxic contaminants in complex mixtures.