Ozonated seawater induces genotoxicity and hematological alterations in turbot (Scophthalmus maximus): implications for management of recirculation aquaculture systems

Abstract

Ozonation has proven useful in recirculating aquaculture systems promoting the stabilization of water quality and disease control. Nevertheless, its cytogenetic and physiological effects on fish are still largely unknown. Hence, this research investigated the effects of ozone exposure in juvenile turbot (Scophthalmus maximus) by assessing its genotoxic potential (erythrocytic nuclear abnormalities — ENA — assay) and alterations on hematological parameters (hemoglobin concentration — Hb, red blood cell — RBC — count, mean cell hemoglobin — MCH). Fish were subjected to a daily 6-h ozone (0.15 mg L− 1) exposure, repeated for 3 consecutive days. In order to assess the potential recovery after ozone treatment, fish were also analyzed on 1-day (R1) and 7-day (R7) post-treatment. An ENA induction was recurrently detected along the exposure period, suggesting genetic damage. Moreover, this clastogenic effect was prolonged beyond the exposure period up to day R7. The Hb concentration increased on days 1, 3 and R1. Similarly, RBC count increased on days 2 and 3, showing a prolonged effect on day R1. No alterations were observed on MCH levels. Since the previous hematological alterations are regarded as physiologic adjustments rather than as an expression of toxicity, the cytogenetic damage emerged as the most serious outcome of ozone treatment. This ozone-induced genotoxicity can later lead to detrimental effects at the organism level, with negative repercussions on fish health and aquaculture productivity. Therefore, overdose of ozonation, even as short-term events, should be avoided in aquaculture operations.