Contents lists available at ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul Impact of environmental hypercapnia on fertilization success rate and the early embryonic development of the clam Limecola balthica (Bivalvia, Tellinidae) from the southern Baltic Sea – A potential CO 2 leakage case study Justyna Świeżak a, ⁎ , Ana R. Borrero-Santiago b , Adam Sokołowski a , Anders J. Olsen c a Department of Marine Ecosystems Functioning, Institute of Oceanography, University of Gdańsk, Al. Marszałka Józefa Piłsudskiego 46, 81-378 Gdynia, Poland b Department of Chemistry, Norwegian University of Science and Technology, Høgskoleringen 5, 7491 Trondheim, Norway c Department of Biology, Norwegian University of Science and Technology, Brattørkaia 17B, 7010 Trondheim, Norway ARTICLE INFO Keywords: Carbon capture and storage CO 2 leakage Fertilization rate Embryonic development Limecola balthica Baltic Sea ABSTRACT Carbon capture and storage technology was developed as a tool to mitigate the increased emissions of carbon dioxide by capture, transportation, injection and storage of CO 2 into subterranean reservoirs. There is, however, a risk of future CO 2 leakage from sub-seabed storage sites to the sea-floor sediments and overlying water, causing a pH decrease. The aim of this study was to assess effects of CO 2 -induced seawater acidification on fertilization success and early embryonic development of the sediment-burrowing bivalve Limecola balthica L. from the Baltic Sea. Laboratory experiments using a CO 2 enrichment system involved three different pH variants (pH 7.7 as control, pH 7.0 and pH 6.3, both representing environmental hypercapnia). The results showed significant fer- tilization success reduction under pH 7.0 and 6.3 and development delays at 4 and 9 h post gamete encounter. Several morphological aberrations (cell breakage, cytoplasm leakages, blastomere deformations) in the early embryos at different cleavage stages were observed. 1. Introduction Carbon dioxide (CO 2 ) concentration in the atmosphere has in- creased from the pre-industrial level of 280 ppm to 407 ppm observed nowadays (Tans and Keeling, 2017). According to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) sur- face seawater pH decline resulting from increased atmospheric CO 2 concentration may reach as much as 0.1 to 0.3 units over the next century. In this context, Carbon Capture and Storage (CCS) offers an innovative technique aiming to reduce emissions of carbon dioxide from industrially combusted fuels to the atmosphere by interception, concentration and deposition of CO 2 into geological formations (IPCC, 2013). Potential reservoirs can be located in natural, either terrestrial or sub-seabed geological formations (Bouzalakos and Mercedes, 2010). The risk associated with implementation of such techniques includes the environmental safety during injection into the storage place and the risk of leakage within deposition period, due to the cap rocks breakage (Damen et al., 2006; Shaffer, 2010). In case of a leakage from the sub- seabed storage site, an excess of CO 2 will cause a decrease of seawater pH, and thus alter physical, chemical and biological processes in situ (Rastelli et al., 2015; Clements and Hunt, 2017). Recently, the interest in studying effects of high partial CO 2 has increased due to the rising awareness of consequences of potential leakage on benthic biota worldwide (Rodríguez-Romero et al., 2014; Basallote et al., 2015; Borrero-Santiago et al., 2017). A potential CO 2 storage site in the Polish Exclusive Economic Zone (oil-carrying B3 field) at a water depth of 80 m has been proposed and offers a promising perspective of CCS implementation in the southern Baltic Sea region (for review see: Sliaupa et al., 2012; ECO2, 2014). With ongoing global ocean acidification, the Baltic Sea appears to be more susceptible to increasing levels of carbon dioxide due to its low salinity buffering capacity, especially in the highly productive coastal areas (Müller et al., 2016). The high biomineralization rates of organic matter deposited on the seafloor in this eutrophic water-basin often cause bottom sediment interstitial water pH to decrease below 7.0, particularly in organic-rich, stratified surface sediments in deep areas (Jansson et al., 2013). Formation of seasonal halocline, that reduces vertical water mixing, implies that deeper- and near-bottom waters should not immediately be affected by increased uptake of carbon di- oxide from the atmosphere (Väli et al., 2012). On the other hand, a halocline may also act as a natural hindrance for vertical carbon dioxide dispersal, and hence dilution, in case of a potential CO 2 leakage from a https://doi.org/10.1016/j.marpolbul.2018.09.007 Received 13 June 2018; Received in revised form 15 August 2018; Accepted 5 September 2018 ⁎ Corresponding author. E-mail address: justyna.swiezak@ug.edu.pl (J. Świeżak). Marine Pollution Bulletin 136 (2018) 201–211 0025-326X/ © 2018 Elsevier Ltd. All rights reserved. T