# Organochlorines Accumulation in Caged Mussels
## 1 Introduction  
The most environmentally widespread organic contaminants, persistent organic pollutants (POPs), are polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs). They are resistant to degradation and their toxic properties may result in serious consequences for the environment and human health. Coastal areas are particularly exposed to these chemicals of anthropogenic origin, mainly from direct industrial and urban wastewater discharges, runoffs from agricultural, watershed areas, and rivers, and the atmosphere [1; 2; 3; 4; 5].  
Kastela Bay has been recognized as a pollution hotspot in the middle eastern Adriatic coast [6; 7; 8]. It has been endangered by the fast population growth, industry traffic, and trade development since the 1950s. Results of the analysis of a long-term data series of dissolved oxygen, nutrients, transparency, and phytoplankton have shown a continuous increase of eutrophication in the Bay [9].  
The bivalve genus _Mytilus_ has been extensively used as a suitable indicator of contamination for marine environments because of their sessile life, filter-feeding activity, and low metabolic capacity for contaminant degradation,which leads to accumulation of contaminants in the mussel tissue and contributes to the identification of spatial and temporal trends in coastal pollution [3; 10; 11; 12].  
OC accumulation in mussel tissue depends on the physiological and biochemical status of the organism and its interaction with the environment.  
Studies on the accumulation of OCs in mussel tissue associated with mussel age have been conducted in relation to body size and lipid content on the bioaccumulation of PCBs in zebra mussels, _Dreissena polymorpha_[13], age- and size-dependent changes in parameters of energy metabolism in wild mussels _Mytitlus edulis_ (L.) from the White Sea [14], and the influence of confounding biological factors when estimating bioaccumulation of PCBs with passive samplers in aquatic ecosystems [15]. Small mussels (15 mm shell length) had higher bioconcentration factors and faster uptake kinetics for PCBs and polycyclic aromatic hydrocarbon congeners compared to larger (21 mm shell length) mussels. Also, high lipid, pre-spawning mussels had greater bioconcentration factors and faster uptake kinetics for the highly hydrophobic compounds than low lipid, post-spawning mussels [13]. [PERSON] and [PERSON] [14] showed significantly lower growth rates and feeding rates associated with the aging process. The effects of age and size on the bioaccumulation of PCBs in mussels were documented by [PERSON] et al. [15], showing that the concentration of PCBs in mussel tissues decreases with size and age.  
The effect of biological factors on the accumulation of OCs in mussels has also been investigated in relation to lipid content and condition index observed OCP levels in _Ensis siliqua_[16]; specimen size (2.5-3.5 cm in shell length) and contaminant levels and profiles in caged mussels _Mytitlus trossulus_, translocated in cages in a southern Baltic Sea coastal area of Poland [10]; mussels at different reproductive stages and nutritive states [17], and physiological conditions [18]. Assessment of the relationship between the age (size) of mussels and OC accumulation is limited to the area of the Adriatic Sea.  
The aim of this study is to investigate the effect of mussel age dependence on biological parameters (shell length, soft tissue, condition index (CI) and lipid content) on OC accumulation by applying the mussels' transplantation technique from a reference station (Mali Ston Bay) to KaStela Bay. The assessment of contaminant accumulation was based on bimonthly exposure of 1- and 2-year-old mussels for one year. The 1- and 2-year-old mussels responded quickly to the changes in the environment after transplantation from the reference station (Mali Ston Bay) to KaStela Bay, with the OC accumulation trend being inversely proportional to the age of mussels.