Effects of CO 2 enrichment on cockle shell growth interpreted with a Dynamic Energy Budget model Chris Klok a, ⁎, Jeroen W.M. Wijsman b , Klaas Kaag a , Edwin Foekema a a IMARES, Ambachtsweg 8A, P.O. Box 57, 1879 AB Den Helder, The Netherlands b IMARES, Korringaweg 5, P.O. Box 77, 4400 AB Yerseke, The Netherlands abstract article info Article history: Received 18 June 2013 Received in revised form 13 January 2014 Accepted 24 January 2014 Available online 2 February 2014 Keywords: CCS OA Marine Mesocosm Cerastoderma edule Risk assessment The increase in human induced atmospheric CO 2 level leads to an increase in ocean acidification (OA). Mitigation of this increase by storage of CO 2 in abandoned marine oil and gas reservoirs is seen as an interesting cost effec- tive solution. However, this involves a risk of CO 2 loss causing localised reductions in seawater pH. In this paper we report on the effects of CO 2 enhancement on the growth of the bivalve Cerastoderma edule in mesocosms. The experiments show significant reductions in shell length, shell weight and cockle flesh dry weight at increased CO 2 level suggesting both direct (shell erosion) and indirect (metabolic) effects. Indirect effects were analysed and interpreted using a Dynamic Energy Budget model by describing changes in 3 metabolic processes: assimi- lation, maintenance, and growth. Based on cockle size data only we could not differentiate between these pro- cesses, however, by using variability of DEB parameter values in 11 bivalve species, we showed growth to be the least relevant process. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Human fossil fuel combustion is considered a major threat to the marine environment because of atmospheric CO 2 dissolving in seawater and forming carbonic acid (H 2 CO 3 ), which dissociates to bicarbonate (HCO 3 - ), carbonate ions (CO 3 2- ) and protons (H + )(Cigliano et al., 2010). As a result it contributes to acidification of oceans (OA) which is expected to increase unless CO 2 emissions are dramatically reduced (Doney et al., 2009). Oceans have become more acidic since preindustri- al times as is illustrated by the decrease in pH of marine surface waters by 0.1 point (Orr et al., 2005). Among options to reduce CO 2 emissions, such as the use of less carbon-intensive fuels (nuclear power and renewable energy sources), and enhancement of biological sinks, Carbon Dioxide Capture and Stor- age (CCS) is seen as feasible and cost effective (ICPP, 2005). A potentially suitable way for CCS is geological storage in abandoned oil and gas res- ervoirs (Steeneveldt et al., 2006). Injection of CO 2 in reservoirs to en- hance the production of oil and gas is already common practice (Tait et al., in press). Storage in sub-seabed oil and gas fields may, however, involve risks of CO 2 leakage. If, as a consequence of e.g. transport pipe- line failure, CO 2 is lost into the marine environment considerable local- ised reductions in seawater pH can be expected to occur (Blackford et al., 2009). Such pH reductions are especially detrimental to species that form calcareous tissues, like molluscs and corals (Hendriks et al., 2010; Hoegh-Guldberg et al., 2007; Kroeker et al., 2010). Many studies report the effects of OA on calcifying organism at various levels of phys- iological detail (e.g. respiration (Melatunan et al., 2011), neutral red re- tention (Beesley et al., 2008)). Few, however, are able to interpret the ecological consequences of reported effects, given a lack of an interpre- tation framework to assess the overall impact. The Dynamic Energy Budget (DEB) theory (Kooijman, 2010; Kooijman and Metz, 1983), pro- vides a logical and consistent framework to integrate the effects of stress factors such as those coming from OA on the vital rates of a species (growth, development, reproduction and survival). Changes in these vital rates directly affect ecologically relevant parameters such as popu- lation viability (e.g. Jager and Klok, 2010; Klok and De Roos, 1996). In DEB the impact of OA can be interpreted as a change in the energy flow within an organism. DEB gives mechanistic insight by describing how a change in growth changes reproduction by treating both vital rates as interdependent (Klok, 2007; Kooijman and Metz, 1983). Cur- rently the only application of DEB in describing impacts of OA is on coccolithophores (Muller and Nisbet, in press). To illustrate possible ecological risks of CCS on vulnerable species we describe in this paper the effects of CO 2 increase on the marine bivalve Cerastoderma edule using an existing DEB model. 2. Methods 2.1. Introduction to DEB DEB theory describes the energy pathways in individuals (Fig. 1). Ac- cording to DEB theory, a reduction in growth can be caused by reduced assimilation (process of feeding and digestion) (1 in Fig. 1), enhanced Journal of Sea Research 94 (2014) 111–116 ⁎ Corresponding author. Tel.: +31 317481452; fax: +31 317487371. E-mail address: chris.klok@wur.nl (C. Klok). 1385-1101/$ – see front matter © 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.seares.2014.01.011 Contents lists available at ScienceDirect Journal of Sea Research journal homepage: www.elsevier.com/locate/seares