Physiological responses and scope for growth upon medium-term exposure to the combined effects of ocean acidification and temperature in a subtidal scavenger Nassarius conoidalis Haoyu Zhang a , Paul K.S. Shin a, b , S.G. Cheung a, b, * a Department of Biology and Chemistry, City University of Hong Kong, Hong Kong, China b State Key Laboratory in Marine Pollution, City University of Hong Kong, Hong Kong, China article info Article history: Received 11 August 2014 Received in revised form 23 February 2015 Accepted 1 March 2015 Available online 4 March 2015 Keywords: Gastropods Physiological energetics Ocean acidification Nassarius conoidalis Temperature abstract Physiological responses (ingestion rate, absorption rate and efficiency, respiration, rate, excretion rate) and scope for growth of a subtidal scavenging gastropod Nassarius conoidalis under the combined effects of ocean acidification (pCO 2 levels: 380, 950, 1250 matm) and temperature (15, 30  C) were investigated for 31 days. There was a significant reduction in all the physiological rates and scope for growth following short-term exposure (1e3 days) to elevated pCO 2 except absorption efficiency at 15  C and 30  C, and respiration rate and excretion rate at 15  C. The percentage change in the physiological rates ranged from 0% to 90% at 15  C and from 0% to 73% at 30  C when pCO 2 was increased from 380 matm to 1250 matm. The effect of pCO 2 on the physiological rates was enhanced at high temperature for ingestion, absorption, respiration and excretion. When the exposure period was extended to 31 days, the effect of pCO 2 was significant on the ingestion rate only. All the physiological rates remained unchanged when temperature increased from 24  C to 30  C but the rates at 15  C were significantly lower, irrespective of the duration of exposure. Our data suggested that a medium-term exposure to ocean acidification has no effect on the energetics of N. conoidalis. Nevertheless, the situation may be complicated by a longer term of exposure and/or a reduction in salinity in a warming world. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction As the largest carbon sink in the world, ocean has absorbed and stored about 118 Pg C, or 25% of the carbon released by human activities since 1800 (Sabine et al., 2004). With this amount of carbon dioxide in seawater, the ocean has come to a bottle neck of its uptake efficiency and buffer capacity, resulting in more carbon dioxide remaining in the atmosphere. The global pCO 2 level has reached 395 matm and is predicted to be around 985 matm by 2100 (IPCC, PCR8.5 scenario, Collins et al., 2013). As a result, an increase in the dissolution of carbon dioxide in the ocean causes chemical changes in sea water and generates ocean acidification (OA) (Ries, 2011). OA has wide-ranging effects on marine organisms. In a meta-analysis of the sensitivities of invertebrates and fishes to OA, all animal taxa studied (corals, echinoderms, molluscs, crustaceans, fishes) were negatively affected by moderate OA (RCP8.5, 936 matm in 2100) and those possessing heavily calcified structures and with low capacities in acid-base regulation (i.e., corals, echinoderms and molluscs) suffer the most, whereas crustaceans are relatively resistant (Wittmann and P€ ortner, 2013). Effects of OA include reduction in the fitness of offspring in littoral spawners (Bartolini et al., 2013) and the calcification rate of calcifying organisms, changes in the physiological responses of benthic animals (Schalkhausser et al., 2014) and disturbance in ecosystem stability (reviewed by Andersson et al., 2011; Kelly and Hofmann, 2013). Nevertheless, not all species are negatively affected. For example, photosynthesis and net primary production of primary producers increased in a high CO 2 world (Semesi et al., 2009). A sea urchin Echinometra sp. from the Red Sea showed high resistance to high pCO 2 (1433 matm) after exposure for 11 months (Yael et al., 2014). An ophiuroid brittlestar Amphiura filiformis showed an increase in metabolism and calcification when exposed to acidified seawater of pH 7.3, although with a substantial cost in the form of muscle wastage (Wood et al., 2008). Even within the same taxon, responses can be species specific. For example, the Mediterranean mussel * Corresponding author. Department of Biology and Chemistry, City University of Hong Kong, Hong Kong, China. E-mail address: bhsgche@cityu.edu.hk (S.G. Cheung). Contents lists available at ScienceDirect Marine Environmental Research journal homepage: www.elsevier.com/locate/marenvrev http://dx.doi.org/10.1016/j.marenvres.2015.03.001 0141-1136/© 2015 Elsevier Ltd. All rights reserved. Marine Environmental Research 106 (2015) 51e60