Comparison between resident and caged mussels: Polycyclic aromatic hydrocarbon accumulation and biological response

•„Active „ and „passive“ biomonitoring were compared, advantages and limitations of each approach discussed.•Resident mussels were better in reflecting the level of PAH loads while only caged mussel could detect input of HMW PAHs.•The majority of differences between resident and caged mussels biological response patterns were site-specific.•Integration of contaminant bioaccumulation and biological endpoints reveals resident mussels as a reliable bioindicator.

The aim of this study was to compare the capability of “passive” and “active” biomonitoring to determine the environmental pressure. For this purpose, PAHs content and several biological responses in resident and caged mussels (Mytilus galloprovincialis) at five sampling sites (Rijeka Bay, Adriatic Sea) were analsed. Resident mussels were found better in reflecting the level of PAH loads at particular sites while only caged mussels could detect input of HMW PAHs. When data of each investigated parameter were compared separately, the majority of differences between resident and caged mussels' results were site-specific. Integration of biological response patterns expressed as Index of Biological Response (IBR) resulted with different sampling sites ranking for resident and caged mussels. Multiple Factor Analysis (MFA) based on integration of tissue PAH concentration and biological response revealed resident mussels as more powerful for detection of environmental pressure. The use of resident mussels is recommended as appropriate and less costly approach for monitoring the effect of pollution.