Genotoxic Response and Mortality in 3 Marine Copepods Exposed to Waterborne Copper

Copper (Cu) is an essential trace metal, but may also be toxic to aquatic organisms. Although many studies have investigated the cytotoxicity of Cu, little is known about the in vivo genotoxic potential of Cu in marine invertebrates. We investigated the genotoxicity of Cu in 2 pelagic calanoid copepods, Acartia tonsa and Temora longicornis, and the intertidal harpacticoid copepod Tigriopus brevicornis by exposing them for 6 and 72 h to waterborne Cu (0, 6, and 60 µg Cu/L). A subsequent 24-h period in filtered seawater was used to investigate delayed effects or recovery. Genotoxicity was evaluated as DNA strand breaks in individual copepods using the comet assay. Copper did not increase DNA strand breaks in any of the species at any concentration or time point. The treatment did, however, cause 100% mortality in A. tonsa following exposure to 60 µg Cu/L. Acartia tonsa and T. longicornis were more susceptible to Cu-induced mortality than the benthic harpacticoid T. brevicornis, which appeared to be unaffected by the treatments. The results show major differences in Cu susceptibility among the 3 copepods and also that acute toxicity of Cu to A. tonsa is not directly associated with genotoxicity. We also show that the comet assay can be used to quantify genotoxicity in individual copepods. Environ Toxicol Chem 2019;38:2224-2232. © 2019 SETAC.

Baseline and oxidative DNA damage in marine invertebrates

Anthropogenic pollutants produce oxidative stress in marine organisms, directly or following generation of reactive oxygen species (ROS), potentially resulting in increased accumulation of DNA strand breaks quantified. The aim of this study is to quantify baseline levels of DNA strand breaks in marine species from four phyla and to assess relative sensitivity to oxidative stress as well as ability to recover. DNA strand breaks were determined using a formamidopyrimidine DNA glycosylase (Fpg)-amended comet assay in circulating cells from blue mussel (Mytilus edulis), shore crab (Carcinus maenas), sea star (Asterias rubens), and vase tunicate (Ciona intestinalis). Lymphocytes from Atlantic cod (Gadus morhua) were used as a reference. In addition to immediate analysis, cells from all species were exposed ex vivo to two concentrations of hydrogen peroxide (H₂O₂) at 25 or 250 μM prior to assay. Mean baseline DNA strand breaks were highest for cells from sea star (34%) followed by crab (25%), mussel (22%), tunicate (17%), and cod (14%). Circulating cells from invertebrates were markedly more sensitive to oxidative stress compared to cod lymphocytes. DNA strand breaks exceeded 80% for sea star, crab, and mussel cells following exposure to the lowest H₂O₂ concentration. There was no recovery for cells from any species following 1 hr in buffer. This study provides an in-depth analysis of DNA integrity for ecologically important species representing 4 phyla. Data indicate that circulating cells from invertebrates are more sensitive to oxidative stress than cells from fish as evidenced by DNA strand breaks. Future studies need to address the extent to which DNA strand breaks may exert consequences for body maintenance costs in marine invertebrates.