## 9 Impact of Micro and Nano Plastics Bioaccumulation on Blood Response in Fish
The harmful effects caused by microplastics are due to additives and chemical substances used during their production or utilization of pollutants absorbed from the environment [206; 207; 51]. MP/NPs induce physical and chemical toxic effects in various organisms including fish. These effects have an impact on the blood response of the exposed organism. In this regard, a study conducted by [PERSON] et al. [184] on Nile Tilapia (_O. niloticus_) showed variations in hematological and hematochemical parameters of this species after exposure to MPs. Regarding to the hematological profile, the obtained results revealed a significant reduction in red blood cell (RBC), hemoglobin concentration (Hb), hematocrit (Ht), mean corpuscular hemoglobin concentration (MCHC), thrombocytes (PT), white blood cell (WBC), and percent of monocytes after exposure to MPs. Percent of lymphocytes, eosinophils and neutrophils showed fluctuation after exposure to MPs. On the contrary, mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) exhibited significant increase. These changes in hematological parameters represent a defense mechanism as a response to MPs toxicity [208]. Similar results were previously found by [PERSON] and [PERSON] [209] in a study on Indian freshwater major carp exposed to cadmium. Moreover, the immune system may be influenced by toxic chemicals in the micro and nano plastics [107]. The immune system of fish is a useful indicator of negative response to environmental stressors [210]. Effects of MP/NPs on chemokines, cytokines and phagocytes, and increased levels of globulins and immunoglobulins [145] were demonstrated in a previous study by [PERSON] et al. [13]. Changes in hematochemical parameters due to exposure to micro- and nano-plastics were detected in different species of fish [73; 182; 184; 187; 211]. A significant increment of creatinine, uric acid, AST, ALT, ALP, glucose, cholesterol, total protein, albumin, globulin, and A/G ratio was found in Nile Tilapia _O. nilicticus_[184] and common goby _P. microps_[73; 211] after exposure to MPs. Increased levels of ALT, AST, ALP, creatinine, glucose, also occur in common carp (_C. carpio_) exposed to sublethal concentrations of micro-plastic [187]. Furthermore, it was shown that nano-plastic intake in fish can alter the proportion of triglycerides/cholesterol of blood [212]. Contrary to what was observed in Nile tilapia and common goby the exposure to MPs causes a decrease of the cholesterol, high-density lipoprotein and triglyceride levels in African catfish and common carp [145; 187]. The increased albumin levels observed in fish after MPs exposure indicate a liver or kidney damage [213] caused by the harmful effects of micro-plastics [182]. All the variations of blood parameters that occur in fish exposed to MP/NPs, represent an effective physiological response of the organism to toxic effects of plastic particles. These blood changes are important biomarkers in toxicological research, environmental monitoring, and prediction of fish health conditions. In the future, it will be important to refine the diagnostic techniques of fish hematology in order to define the potential blood biomarkers related to micro and nano plastics bioaccumulation.