Biogeographic Vulnerability to Ocean Acidification and Warming in A

Marine Pollution Bulletin 126 (2018) 308–311

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Marine Pollution Bulletin

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Baseline Biogeographic vulnerability to ocean acidiﬁcation and warming in a marine T bivalve ⁎ Carl Van Colena, , Anna Janssonb,c, Alice Saunierd,1, Thomas Lacoue-Labathed, Magda Vincxa a Ghent University, Marine Biology Research Group, Krijgslaan 281 – S8, 9000 Gent, Belgium b Environmental and Marine Biology, Faculty of Science and Engineering, Åbo Akademi University, Åbo, Finland c Tvärminne Zoological Station, University of Helsinki, Hanko, Finland d Littoral Environnement et Sociétés (LIENSs), UMR 7266 CNRS - Université de La Rochelle, 2 rue Olympe de Gouges, 17000 La Rochelle, France

ARTICLE INFO ABSTRACT

Keywords: Anthropogenic CO2 emissions are rapidly changing seawater temperature, pH and carbonate chemistry. This fi Ocean acidi cation study compares the embryonic development under high pCO2 conditions across the south-north distribution Sea surface temperature rise range of the marine clam Limecola balthica in NW Europe. The combined effects of elevated temperature and Biogeography reduced pH on hatching success and size varied strongly between the three studied populations, with the Gulf of Mollusks Finland population appearing most endangered under the conditions predicted to occur by 2100. These results Embryogenesis demonstrate that the assessment of marine faunal population persistence to future climatic conditions needs to Limecola (Macoma) balthica consider the interactive effects of co-occurring physico-chemical alterations in seawater within the local context that determines population fitness, adaptation potential and the system resilience to environmental change.

Anthropogenic carbon dioxide emissions are rapidly changing sea- et al., 2014), from which adult organisms were sampled in this ex- water pH and carbonate chemistry at global scales with vast repercus- periment (Table 1): a Baltic lineage, and a southern and northern sions on marine biodiversity and ecosystem functioning (Dupont and Atlantic lineage that are separated by the French Finistère peninsula. Portner, 2013). Meta-analysis (Kroeker et al., 2013) revealed that the The low saline water at the subtidal sampling location in the Gulf of early life stages of mollusks are particularly vulnerable to ocean acid- Finland (6 PSU) had lower buffering capacity to change in seawater − ification. Disruption of physiological processes and altered mineral ki- carbonate chemistry (total alkalinity = 1.47 μmol·kg 1 ± 0.03 SD; netics associated with low carbonate saturation states and low pH in Gran titration (Dickson et al., 2007), n = 6 per location) as compared to high pCO2 waters hinder the ability to normally develop shells during the two intertidal sampling locations along the NE Atlantic coast (Gulf − the pelagic larval development phase and increase dissolution mortality of Biscay and southern North Sea TA = 2.35 μmol·kg 1 ± 0.02 SD − during the early settlement phase (Waldbusser et al., 2015a; and 2.48 μmol·kg 1 ± 0.04 SD, respectively). The experiments were Waldbusser et al., 2015b). Hence exposure of early life stages of mol- performed in February 2014 (northern Atlantic lineage; SST = 5.7 °C), lusks to ocean acidification may represent a bottleneck for their po- March 2014 (southern Atlantic lineage; SST = 10.6 °C) and May 2014 pulations. Yet, evidence exist that the magnitude of acidification effects (Baltic lineage; SST = 6.5 °C). About 120 adults of each population on marine biota might strongly depend on the local environmental were induced to spawn in 0.2 μm filtered seawater from the study area context such as temperature and food availability (Kroeker et al., 2013; following the procedures described in (Van Colen et al., 2009). Thomsen et al., 2013), as well as on the potential for local adaptation Spawning success and egg production per female varied among popu- (Calosi et al., 2017). In this study we compared the embryonic devel- lations with the highest reproductive output for the southern North Sea opment under combined conditions of seawater pH and temperature population (Table 1). After 3 h of gamete fertilization under ambient predicted for 2100 (IPCC, 2014) between different clades of the benthic seawater pH (Bay of Biscay, southern North Sea, Gulf of Finland: 8.14, tellinid bivalve Limecola (Macoma) balthica that occur across the coastal 7.89, 8.04 respectively) and a temperature of 15 °C, embryos were south-north range of the species in northwestern Europe. transferred to 5 replicate 58 mL vials containing 0.2 μm filtered sea- Previous work on L. balthica demonstrated the presence of at least water that was conditioned to different carbonate chemistry (Table 2) three divergent mitochondrial clades in northwestern Europe (Saunier and temperature, i.e. 15 °C and 18 °C. The 15 °C treatment represents

⁎ Corresponding author. E-mail address: [email protected] (C. Van Colen). 1 Present address: IFREMER, SG2M-LGPMM, Laboratoire de Génétique et Pathologie des Mollusques Marins, Avenue de Mus de Loup, 17,390 La Tremblade, France. https://doi.org/10.1016/j.marpolbul.2017.10.092 Received 1 April 2017; Received in revised form 22 October 2017; Accepted 31 October 2017 0025-326X/ © 2017 Elsevier Ltd. All rights reserved. C. Van Colen et al. Marine Pollution Bulletin 126 (2018) 308–311

Table 1 − Characteristics of the sampling location and parental properties of the studied populations. Condition index is determined as shell-free dry weight·shell dry weight 1 in − mg g 1 from 15 individuals per population. Mud content is taken from (Du et al., 2017)* and (Van Colen et al., 2010)** and calculated from 4 replicate samples collected at Storfjärden. Error bars denote standard deviations.

Sampling location

Region Gulf of Biscay Southern North Gulf of Finland Sea Sampling site Aytré Schelde, Paulina Storfjärden Coordinate 46.13 N, 51.34 N, 3.72E 59.84 N, 22.44E 1.13 W Mud content 37.33* 30.9** 92.2 (% < 63 μm)

Parental properties

Mitochondrial lineage Southern NE Atlantic Northern NE Atlantic Baltic Condition index 118.60 ± 6.75 108.78 ± 7.62 112.94 ± 6.87 Spawning success (%) 4.3 31.4 7.6 − Egg production·spawning female 1 22,222 13,615 3051

Table 2 therefore calculated as the average of the pH at the start and end of μ Average pH (NBS scale), partial pressure of CO2 (pCO2 in atm), carbonate ion con- incubation. All parameters of the carbonate chemistry were determined 2– − 1 centration (CO3 in μmol·kg ) and saturation state of the water regarding calcite from pHNBS,TANBS, temperature and salinity using CO2SYS (Pelletier (Ωcalcite) during the 72 h incubations (salinity Bay of Biscay, southern North Sea, Gulf of Finland: 32, 31, 6 PSU respectively). et al., 2007). The regional diﬀerence in ambient pH and the variable pH change Population 15 °C 18 °C during the incubation resulted in a gradient of tested pH conditions

– – (Fig. 1, Table 2). Simple linear regression models were used to de- pH pCO CO 2 Ω pH pCO CO 2 Ω 2 3 c 2 3 c termine the influence of pH on hatching success and median size of Bay of Biscay 8.09 365.8 168.6 4.1 8.07 440.3 162.3 4.0 embryos. Extreme outliers were excluded from the analysis to achieve 8.02 443.5 146.8 3.6 7.99 548.0 138.3 3.4 normality of residuals (casewise plot of residuals ± 3 sigma; Statistica 7.92 576.9 120.3 2.9 7.88 721.8 111.8 2.7 5.5). Subsequently, the effects of pH and temperature were analyzed 7.82 769.1 95.6 2.3 7.79 932.0 90.9 2.2 through a series of regression slope comparisons. First, a homogeneity 7.73 956.4 79.7 1.9 7.70 1165.7 75.3 1.8 7.61 1314.5 60.5 1.5 7.60 1522.5 59.7 1.5 of slopes model was calculated to analyze whether the pH (i.e. con- Southern North Sea 7.80 848.2 95.7 2.3 7.79 996.7 93.4 2.3 tinuous predictor) and temperature (i.e. categorical predictor) inter- 7.70 1099.3 76.9 1.9 7.68 1303.7 74.4 1.8 acted in influencing hatching success and size. Subsequently a separate 7.62 1350.3 64.3 1.6 7.59 1666.6 59.9 1.5 slopes model was applied when both predictors interacted, while ana- 7.51 1836.3 48.8 1.2 7.48 2179.9 47.0 1.2 7.45 2103.1 43.1 1.1 7.43 2477.7 41.8 1.0 lysis of covariance (ANCOVA) was applied when both predictors did not 7.35 2716.5 34.0 0.8 7.34 3066.0 34.4 0.8 interact in affecting hatching success and size (Statistica 5.5). Baltic Sea 7.87 680.5 23.9 0.7 7.84 805.1 23.1 0.7 Hatching success under control conditions (15 °C and ambient pH) 7.78 849.8 19.4 0.6 7.73 1056.3 17.9 0.5 varied significantly across populations with a higher number of devel- 7.67 1122.5 14.9 0.4 7.63 1367.3 14.0 0.4 oped D-shaped shelled larvae in the Bay of Biscay population (70 ± 3 7.58 1410.0 12.0 0.3 7.56 1629.5 11.8 0.3 7.52 1632.8 10.4 0.3 7.49 1905.3 10.1 0.3 SE %) as compared to the southern North Sea (22 ± 3 SE %) and Gulf 7.44 1969.6 8.6 0.2 7.41 2300.1 8.4 0.2 of Finland population (39 ± 2 SE %) (Kruskal-Wallis rank sum test: H (2) = 11.57, p = 0.003). Decreasing seawater pH significantly reduced hatching success in all populations (p < 0.001), but an antagonistic the seawater temperature during the temporal pelagic occurrence of the temperature × pH interaction effect was observed in the Bay of Biscay larvae in the three regions (Gilbert, 1978) and the latter temperature population (Separate slopes model: temperature × pH F2, 51 = 31.586, fl re ects a 3 °C increase by 2100 according to IPCC RCP 8.5 (current p < 0.001) whereas the pH effect on hatching success was in- emission trajectory) model prediction (IPCC, 2014). Seawater carbo- dependent of temperature in the southern North Sea and Gulf of Finland nate chemistry was manipulated through bubbling with pure CO2 de- population (Fig. 1, upper panel). For the southern North Sea population creasing pH in a stepwise fashion of ~0.1 pH units down to ~0.5 pH a higher hatching success was observed at 18 °C as compared to 15 °C units below ambient conditions covering the variability in predicted pH (ANCOVA: pH F1, 57 = 45.66, p < 0.001; temperature F1, 57 = 13.85, conditions by 2100 according to IPPC models (IPCC, 2014) and the p < 0.001), whereas temperature did not affect hatching success in the even more acidic conditions expected to occur in coastal regions Gulf of Finland population (ANCOVA: pH F1, 57 = 131.86, p < 0.001; (Wootton et al., 2008; Provoost et al., 2010). Density of embryos was temperature F1, 57 = 1.24, p = 0.974). The size of hatched embryos −1 −1 10 mL for the Gulf of Finland population and 15 mL for the two under control conditions varied significantly across populations with a other populations. Embryonic development was stopped after 72 h by larger size in the southern North Sea population (141 ± 2 SE μm) as – adding 1 mL of a neutralized 4% formaldehyde tap water solution to compared to the Bay of Biscay (136 ± 0.8 SE μm) and Gulf of Finland fi the culture. Hatching occurs within the rst three days of development population (122 ± 0.5 SE μm) (Kruskal-Wallis rank sum test: H(2) fi [personal observations] and hatching success was de ned accordingly = 12.02 p = 0.003). Hatching size in the Bay of Biscay population did as the proportion of embryos that developed a D-shaped shell after 72 h. not vary significantly among pH levels for both tested temperatures Δ During the incubations respiration caused pH to decrease ( pH Bay of (Kruskal-Wallis rank sum test: 15 °C H(5) = 1.70, p = 0.889; 18 °C H − − Δ Biscay: 0.06 ± 0.02SD (15 °C), 0.14 ± 0.01SD (18 °C); pH (5) = 10.20, p = 0.069). In contrast, the size of hatched embryos in the − − southern North Sea: 0.17 ± 0.05SD (15 °C), 0.22 ± 0.07SD southern North Sea and Gulf of Finland population decreased sig- Δ − (18 °C); pH Gulf of Finland 0.25 ± 0.08 SD (15 °C), nificantly with decreasing pH with the smallest sizes found in calcite- −0.31 ± 0.09 (18 °C)). pH values reported in this study were

309 C. Van Colen et al. Marine Pollution Bulletin 126 (2018) 308–311

Seasonal pH variability in the Gulf of Finland (> 1 pH unit; (Brutemark et al., 2011)) is generally about twice as high as in the Schelde estuary (Provoost et al., 2010) and Gulf of Biscay (d'Elbee et al., 2014). Despite that such high seasonal variability could potentially facilitate evolu- tionary adaptation (Sunday et al., 2014), the Gulf of Finland population appears to be most endangered in future more acidic and warmer coastal seas with < 15% of the embryos hatching successfully at a pH of 7.5. In contrast, temperature rise moderately alleviated negative acidification effects on hatching success in both populations from the Atlantic coast. In summary our results demonstrate that the assessment of marine faunal population persistence to future climatic conditions needs to consider the interactive effects of co-occurring physico-chemical alterations in seawater within the local context that determines population fitness, adaptation potential and the system resilience to environmental change.

Author contributions

Conceived and designed the experiments: CVC, TLL, AJ. Performed the experiments: CVC, TLL, AJ, AS; Analyzed the data: CVC, TL; Wrote the paper: CVC, MV, TLL.

Acknowledgements

This work was financially supported through the provision of a post- doctoral fellowship to the first author by the Flemish Fund for Scientific Research (FWO Flanders, 1.2.380.11.N.00) and through UGent BOF GOA projects 01GA1911 and 01G02617. This paper is dedicated to Otis.

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