1 3 Mar Biol DOI 10.1007/s00227-015-2722-9 ORIGINAL PAPER Combined effects of short-term ocean acidification and heat shock in a benthic copepod Tigriopus japonicus Mori Wei Li 1,2 · Guodong Han 1 · Yunwei Dong 1 · Atsushi Ishimatsu 3 · Bayden D. Russell 4 · Kunshan Gao 1 Received: 20 March 2015 / Accepted: 6 August 2015 © Springer-Verlag Berlin Heidelberg 2015 not affected across all treatments. Our results demonstrate that T. japonicus responds more sensitively to heat shocks rather than to seawater acidification; however, ocean acidi- fication may synergistically act with ocean warming to mediate the energy allocation of copepods. Introduction Increasing global temperatures are broadly predicted to cause changes to the distributions of species. While virtu- ally all biological processes are affected by temperature, there is recent recognition that the degree to which spe- cies are affected will be determined in part by their inher- ent ability to acclimate and adapt to increased temperatures (Sanford and Kelly 2011). In addition, many habitats dem- onstrate large variability in environmental conditions, both spatially and temporally, altering predicted biological out- comes (Helmuth et al. 2006; Mislan et al. 2014). Coastal marine environments in particular are usually characterized by large changes in both chemical and physical properties, with diel, seasonal and inter-annual perturbations of tem- perature, pH and oxygen along with tide cycle, upwelling events and biological activities (Duarte et al. 2013; Mar- shall et al. 2011; Melzner et al. 2013). Organisms inhabiting coastal waters experience strong fluctuations of temperature both daily and seasonally (Davison and Pearson 1996). Moreover, sea surface tem- perature (SST) has been increasing in the last several dec- ades, with shallow coastal waters being strongly impacted (Lima and Wethey 2012), and surface ocean temperature likely to further increase between 0.6 and 2.0 °C by the end of this century (Stocker et al. 2013). Importantly, in addition to this rise in mean temperature, there will be an increase in temperature variation, leading to more extreme Abstract Warming of the world’s oceans is predicted to have many negative effects on organisms as they have optimal thermal windows. In coastal waters, however, both temperatures and pCO 2 (pH) exhibit diel variations, and biological performances are likely to be modulated by physical and chemical environmental changes. To under- stand how coastal zooplankton respond to the combined impacts of heat shock and increased pCO 2 , the benthic copepod Tigriopus japonicus were treated at temperatures of 24, 28, 32 and 36 °C to simulate natural coastal tempera- tures experienced in warming events, when acclimated in the short term to either ambient (LC, 390 μatm) or future CO 2 (HC, 1000 μatm). HC and heat shock did not induce any mortality of T. japonicus, though respiration increased up to 32 °C before being depressed at 36 °C. Feeding rate peaked at 28 °C but did not differ between CO 2 treatments. Expression of heat shock proteins (hsps mRNA) was posi- tively related to temperature, with no significant differences between the CO 2 concentrations. Nauplii production was Communicated by H. Pörtner. Reviewed by undisclosed experts. * Kunshan Gao ksgao@xmu.edu.cn 1 State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, China 2 College of Life and Environmental Sciences, Huangshan University, Huangshan 245041, China 3 Institute for East China Sea Research, Nagasaki University, Nagasaki 851-2213, Japan 4 Swire Institute of Marine Science and School of Biological Sciences, The University of Hong Kong, Hong Kong SAR, China Author's personal copy