Contents lists available at ScienceDirect Aquatic Toxicology journal homepage: www.elsevier.com/locate/aqtox Copper and ocean acidification interact to lower maternal investment, but have little effect on adult physiology of the Sydney rock oyster Saccostrea glomerata Elliot Scanes a,b, ⁎ , Laura M. Parker a , Wayne A. O’Connor b , Mitchell C. Gibbs a , Pauline M. Ross a a The University of Sydney, School of Life and Environmental Sciences, Camperdown, NSW, 2006, Australia b Department of Primary Industries, Port Stephens Fisheries Institute, Taylors Beach Road, Taylors Beach, NSW, 2316, Australia ARTICLE INFO Keywords: Copper Ocean acidification Mollusc Oysters Lipids Eggs Transgenerational effects Resilience Climate change ABSTRACT It remains unknown how molluscs will respond to oceans which are increasingly predicted to be warmer, more acidic, and heavily polluted. Ocean acidification and trace metals will likely interact to increase the energy demands of marine organisms, especially oysters. This study tested the interactive effect of exposure to elevated pCO 2 and copper on the energetic demands of the Sydney rock oyster (Saccostrea glomerata) during reproductive conditioning and determined whether there were any positive or negative effects on their offspring. Oysters were exposed to elevated pCO 2 (1000 μatm) and elevated copper (Cu 50 μgL -1 [0.787 μM]) in an orthogonal design for eight weeks during reproductive conditioning. After eight weeks, energetic demands on oysters were mea- sured including standard metabolic rate (SMR), nitrogen excretion, molar oxygen to nitrogen (O:N) ratio, and pH e of adult oysters as well as the size and total lipid content of their eggs. To determine egg viability, the gametes were collected and fertilised from adult oysters, the percentage of embryos that had reached the tro- chophore stage after 24 h was recorded. Elevated pCO 2 caused a lower extracellular pH and there was a greater O:N ratio in adult oysters exposed to copper. While the two stressors did not interact to cause significant effects on adult physiology, they did interact to reduce the size and lipid content of eggs indicating that energy demand on adult oysters was greater when both elevated pCO 2 and copper were combined. Despite the lower energy, there were no negative effects on early embryonic development. In conclusion, elevated pCO 2 can interact with metals and cause greater energetic demands on oysters; in response oysters may lower maternal investment to offspring. 1. Introduction The legacy of poor environmental management lingers in estuaries around the world. Anthropogenic rubbish, persistent organic com- pounds, nutrients and trace metals pollute estuaries adjacent to urban and industrial areas (Nriagu, 1990; Ridgway and Shimmield, 2002; Halpern et al., 2008). Despite their degraded nature, polluted estuaries support a diversity of marine organisms including bivalve oysters. Oysters are integral to functioning estuaries because they filter the water column, cycle nutrients and provide biogenic habitat, but these traits also make oysters vulnerable to toxic pollutants like trace metals (Connell, 1990). Exposure to trace metals can affect cellular function, damage DNA, and ultimately lead to cellular death because oysters exposed to trace metals need to expend energy on protein synthesis to repair and detoxify cells (Cherkasov et al., 2006; Sokolova and Lannig, 2008). As oceans warm and acidify over the next century (Collins et al., 2013) oysters and other bivalves will be particularly vulnerable (Gazeau et al., 2013). Several studies have shown that ocean acid- ification alone will alter the physiology of oysters and restrict their capacity to grow and reproduce (Pörtner, 2001; Pörtner et al., 2004; Fabry, 2008; Doney et al., 2009; Parker et al., 2013). Other stressors like low-salinity, air exposure or trace metals have been shown to ex- acerbate the effects of elevated CO 2 (Ivanina and Sokolova, 2015; Parker et al., 2017a, b; Scanes et al., 2017). Ivanina and Sokolova (2015) found that elevated partial pressure of CO 2 (pCO 2 ) and trace metals acted indirectly on a range of metabolic and physiological processes in oysters but it is difficult to identify the mechanisms that underpin such interactions. Lewis et al. (2016) found copper and CO 2 interacted synergistically to reduce extracellular pH (pH e ) in the mussel Mytilus edulis. The mussel respired less when ex- posed to the trace metal copper. Respiring less had no effect on pH e https://doi.org/10.1016/j.aquatox.2018.07.020 Received 15 June 2018; Received in revised form 26 July 2018; Accepted 26 July 2018 ⁎ Corresponding author. Current address: School of Life and Environmental Sciences, University of Sydney, Building A11, Camperdown, NSW, 2006, Australia. E-mail address: elliot.scanes@sydney.edu.au (E. Scanes). Aquatic Toxicology 203 (2018) 51–60 Available online 30 July 2018 0166-445X/ © 2018 Elsevier B.V. All rights reserved. T