Assessing relative biomarker responses in marine and freshwater bivalve molluscs following exposure to phosphorus 32 (32P): Application of genotoxicological and molecular biomarkers

Abstract

Anthropogenic radionuclides can enter water bodies through accidental or controlled discharges. In order to assess their potential impact, understanding the link between exposure, tissue specific bioaccumulation and radiation dose rate, to biological or biomarker responses in aquatic biota is required. Adopting an integrated, multi-biomarker, multispecies approach, we have investigated potential biological responses induced by short-lived radionuclide, phosphorus-32 (32P, radiophosphorus) in two ecologically important mussel species, the freshwater Dreissena polymorpha (DP) and marine Mytilus galloprovincialis (MG). Adult individuals were exposed to 32P for 10 days, to acquire nominal whole-body average dose rates of 0.10, 1 and 10 mGy d-1, which encompass a screening value of 10 μGy h-1 (0.24 mGy d-1), in accordance with the ERICA tool. Following exposure, a suite of genotoxic biomarkers (DNA damage, γ-H2AX induction and micronucleus [MN] formation) were measured in gill and digestive gland tissues, along with transcriptional expression of selected stress-related genes in both the species (i.e. hsp70/90, sod, cat and gst). Our results demonstrate the relationship between tissue specific dosimetry, where 32P induced a dosedependent increase, and biological responses independent of species. Gene expression analysis revealed little significant variation across species or tissues. Overall, MG appeared to be more sensitive to short-term damage (i.e. high DNA damage and γ-H2AX induction), particularly in digestive gland. This study contributes to limited knowledge on the transfer and biological impact of radionuclides within differing aquatic systems on a tissue specific level, aiding the development of adequate management and protective strategies.

Evaluation of interactive effects of phosphorus-32 and copper on marine and freshwater bivalve mollusks

“…Comet IV imaging software (Perceptive Imaging, Bury St Edmunds, UK) was used for scoring the cells (100 cells per slide). Genotoxicity data are presented as % Tail DNA in accordance to previous studies (Kumaravel and Jha 2006;Vernon et al 2020).…”

“…Biological assays are described in detail in previous studies from our laboratory (Jha et al 2005;Cheung et al 2006;Al-Subiai et al 2011;Dallas et al 2013;Pearson et al 2018;Vernon et al 2020). DNA strand breakage was determined using the single-cell gel-electrophoresis or comet assay.…”

“…MN induction and γ-H2AX expression analysis are described in full in Vernon et al (2020). MN were scored following widely accepted criteria (Venier et al 1997;Bolognesi and Fenech 2012).…”

“…RNA extraction, cDNA synthesis and Real-time Polymerase chain reaction (qPCR) were performed in accordance to Vernon et al (2020).…”

“…The ERICA (Environmental Risk from Ionizing Contaminants: Assessment and Management) tool was used for dose estimation, as described in detail in Vernon et al (2018Vernon et al ( , 2020. Dose rates for whole-body and tissue-specific 32P concentrations are presented in Table 1.…”