Population genetic and dispersal modeling data for Bathymodiolus mussels from the Mid-Atlantic Ridge

The zip folder comprises a text file and a gzipped tar archive. 1) The text file contains individual genotype data for 90 SNPs, 9 microsatellites and the mitochondrial ND4 gene that were determined in deep-sea hydrothermal vent mussels from the Mid-Atlantic Ridge (genus Bathymodiolus). Mussel specimens are grouped according to the population (pop)/location from which they have been sampled (first column). The remaining columns contain the respective allele/haplotype codes for the different genetic loci (names in the header line). The data file is in CONVERT format and can be directly transformed into different input files for population genetic statistics. 2) The tar archive contains NetCDF files with larval dispersal probabilities for simulated annual larval releases between 1998 and 2007. For each simulated vent location (Menez Gwen, Lucky Strike, Rainbow, Vent 1-10) two NetCDF files are given, one for an assumed pelagic larval duration of 1 year and the other one for an assumed pelagic larval duration of 6 months (6m).

Ocean acidification alters the material properties of Mytilus edulis shells

Ocean acidification (OA) and the resultant changing carbonate saturation states is threatening the formation of calcium carbonate shells and exoskeletons of marine organisms. The production of biominerals in such organisms relies on the availability of carbonate and the ability of the organism to biomineralize in changing environments. To understand how biomineralizers will respond to OA the common blue mussel, Mytilus edulis, was cultured at projected levels of pCO2 (380, 550, 750, 1000 µatm) and increased temperatures (ambient, ambient plus 2°C). Nanoindentation (a single mussel shell) and microhardness testing were used to assess the material properties of the shells. Young's modulus (E), hardness (H) and toughness (KIC) were measured in mussel shells grown in multiple stressor conditions. OA caused mussels to produce shell calcite that is stiffer (higher modulus of elasticity) and harder than shells grown in control conditions. The outer shell (calcite) is more brittle in OA conditions while the inner shell (aragonite) is softer and less stiff in shells grown under OA conditions. Combining increasing ocean pCO2 and temperatures as projected for future global ocean appears to reduce the impact of increasing pCO2 on the material properties of the mussel shell. OA may cause changes in shell material properties that could prove problematic under predation scenarios for the mussels; however, this may be partially mitigated by increasing temperature.

In situ measurements of hydrogen sulfide, oxygen, and temperature in diffuse fluids of the ultramafic-hosted Logatchev hydrothermal vent field (Mid-Atlantic Ridge)

The Logatchev hydrothermal vent field (14°45'N, Mid-Atlantic Ridge) is located in a ridge segment characterized by mantle-derived ultramafic outcrops. Compared to basalt-hosted vents, Logatchev high temperature fluids are relatively low in sulfide indicating that the diffuse, low temperature fluids of this vent field may not contain sufficient sulfide concentrations to support a chemosymbiotic invertebrate community. However, the high abundances of bathymodiolin mussels with bacterial symbionts related to free-living sulfur oxidizing bacteria suggested that bioavailable sulfide is present at Logatchev. To clarify if diffuse fluids above mussel beds of Bathymodiolus puteoserpentis provide the reductants and oxidants needed by their symbionts for aerobic sulfide oxidation, in situ microsensor measurements of dissolved hydrogen sulfide and oxygen were combined with simultaneous temperature measurements. High temporal fluctuations of all three parameters were measured above the mussel beds. H2S and O2 co-existed with mean concentrations between 9-31 µM (H2S) and 216-228 µM (O2). Temperature maxima (<= 7.4°C) were generally concurrent with H2S maxima (<= 156 µM) and O2 minima (>= 142 µM). Long-term measurements for 250 days using temperature as a proxy for oxygen and sulfide concentrations indicated that the mussels were neither oxygen- nor sulfide-limited. Our in situ measurements at Logatchev indicate that sulfide may also be bioavailable in diffuse fluids from other ultramafic-hosted vents along slow- and ultraslow-spreading ridges.

Absolute abundances of benthic foraminifers and stable isotopes from the Alvin dives 3709-3712

The presence of gas hydrates on the Blake Ridge diapir, northeastern Atlantic Ocean, offers an opportunity to study the impact of methane seepage on the ecology and geochemistry of benthic foraminifera in the late Holocene. Three push cores, covering a time span of ~ 1000 yrs, were retrieved from three distinct microhabitats at the top of the diapir at a water depth of ~ 2150 m: (i) sediments away from seepage (control core), (ii) sediments overlain by clusters of methanotrophic and thiotrophic bivalves, and (iii) chemoautotrophic microbial mats. The foraminiferal assemblages at the two seep sites are marked by a reduction in benthic foraminiferal species diversity, coupled with a near-absence of agglutinated species. However, an opportunistic population rise in CH4- or H2S-tolerant calcareous species (e.g., Globocassidulina subglobosa and Cassidulina laevigata) that utilize the abundant trophic resources at the seeps has led to an increase in the overall assemblage density there. The delta18O and delta13C values of three species of benthic foraminifera - Gyroidinoides laevigatus, Globocassidulina subglobosa, and Uvigerina peregrina - and the planktonic species Globorotalia menardii were acquired from all three cores. The benthic species from methane seeps yield delta13C values of 0.1 to - 4.2 (per mil VPDB), that are distinctly more 13C-depleted relative to the delta13C of 0.4 to - 1.0 (per mil VPDB) at the control (off seep) site. The species from a mussel-bed site exhibit more negative delta13C values than those from microbial mats, possibly reflecting different food sources and higher rate of anaerobic oxidation of methane. The positive delta13C values in the paired planktonic species suggest that authigenic carbonate precipitation did not overprint the observed 13C depletions. Hence the probable cause of negative delta13C of benthic foraminifera is primary calcification from Dissolved Inorganic Carbon (DIC) containing mixed carbon fractions from (a) highly 13C-depleted, microbially-oxidized methane and (b) a seawater source.

Immunomodulating effects of environmentally realistic copper concentrations in Mytilus edulis adapted to naturally low salinities, link to supplementary material

The monitoring of organisms' health conditions by the assessment of their immunocompetence may serve as an important criterion for the achievement of the Good Environmental Status (GES) as defined in the Marine Strategy Framework Directive (EU). In this context, the complex role of natural environmental stressors, e.g. salinity, and interfering or superimposing effects of anthropogenic chemicals, should be carefully considered, especially in scenarios of low to moderate contamination. Organisms from the Baltic Sea have adapted to the ambient salinity regime, however energetically costly osmoregulating processes may have an impact on the capability to respond to additional stress such as contamination. The assessment of multiple stressors, encompassing natural and anthropogenic factors, influencing an organisms' health was the main aim of the present study. Immune responses of Mytilus edulis, collected and kept at natural salinities of 12 per mil (LS) and 20 per mil (MS), respectively, were compared after short-term exposure (1, 7 and 13 days) to low copper concentrations (5, 9 and 16 µg/L Cu). A significant interaction of salinity and copper exposure was observed in copper accumulation. LS mussels accumulated markedly more copper than MS mussels. No combined effects were detected in cellular responses. Bacterial clearance was mostly achieved by phagocytosis, as revealed by a strong positive correlation between bacterial counts and phagocytic activity, which was particularly pronounced in LS mussels. MS mussels, on the other hand, seemingly accomplished bacterial clearance by employing additional humoral factors (16 µg/L Cu). The greatest separating factor in the PCA biplot between LS and MS mussels was the proportion of granulocytes and hyalinocytes while functional parameters (phagocytic activity and bacterial clearance) were hardly affected by salinity, but rather by copper exposure. In conclusion, immune responses of the blue mussel may be suitable and sensitive biomarkers for the assessment of ecosystem health in brackish waters (10-20 per mil S).

Seawater carbonate chemistry and calcification during incubation experiments with Mytilus edulis and Grassostrea gigas, 2006

Ocean acidification resulting from human emissions of carbon dioxide has already lowered and will further lower surface ocean pH. The consequent decrease in calcium carbonate saturation potentially threatens calcareous marine organisms. Here, we demonstrate that the calcification rates of the edible mussel (Mytilus edulis) and Pacific oyster (Crassostrea gigas) decline linearly with increasing pCO2. Mussel and oyster calcification may decrease by 25 and 10%, respectively, by the end of the century, following the IPCC IS92a scenario (?740 ppmv in 2100). Moreover, mussels dissolve at pCO2 values exceeding a threshold value of ?1800 ppmv. As these two species are important ecosystem engineers in coastal ecosystems and represent a large part of worldwide aquaculture production, the predicted decrease of calcification in response to ocean acidification will probably have an impact on coastal biodiversity and ecosystem functioning as well as potentially lead to significant economic loss.

Data compilation on the biological response to ocean acidification: environmental and experimental context of data sets and related literature

The exponential growth of studies on the biological response to ocean acidification over the last few decades has generated a large amount of data. To facilitate data comparison, a data compilation hosted at the data publisher PANGAEA was initiated in 2008 and is updated on a regular basis (doi:10.1594/PANGAEA.149999). By January 2015, a total of 581 data sets (over 4 000 000 data points) from 539 papers had been archived. Here we present the developments of this data compilation five years since its first description by Nisumaa et al. (2010). Most of study sites from which data archived are still in the Northern Hemisphere and the number of archived data from studies from the Southern Hemisphere and polar oceans are still relatively low. Data from 60 studies that investigated the response of a mix of organisms or natural communities were all added after 2010, indicating a welcomed shift from the study of individual organisms to communities and ecosystems. The initial imbalance of considerably more data archived on calcification and primary production than on other processes has improved. There is also a clear tendency towards more data archived from multifactorial studies after 2010. For easier and more effective access to ocean acidification data, the ocean acidification community is strongly encouraged to contribute to the data archiving effort, and help develop standard vocabularies describing the variables and define best practices for archiving ocean acidification data.

Seawater carbonate chemistry and Mytilus edulis biological processes during experiments, 2010

CO2 emissions are leading to an acidification of the oceans. Predicting marine community vulnerability towards acidification is difficult, as adaptation processes cannot be accounted for in most experimental studies. Naturally CO2 enriched sites thus can serve as valuable proxies for future changes in community structure. Here we describe a natural analogue site in the Western Baltic Sea. Seawater pCO2 in Kiel Fjord is elevated for large parts of the year due to upwelling of CO2 rich waters. Peak pCO2 values of >230 Pa (>2300 µatm) and pHNBS values of <7.5 are encountered during summer and autumn, average pCO2 values are ~70 Pa (~700 µatm). In contrast to previously described naturally CO2 enriched sites that have suggested a progressive displacement of calcifying auto- and heterotrophic species, the macrobenthic community in Kiel Fjord is dominated by calcifying invertebrates. We show that blue mussels from Kiel Fjord can maintain control rates of somatic and shell growth at a pCO2 of 142 Pa (1400 µatm, pHNBS = 7.7). Juvenile mussel recruitment peaks during the summer months, when high water pCO2 values of ~100 Pa (~1000 µatm) prevail. Our findings indicate that calcifying keystone species may be able to cope with surface ocean pHNBS values projected for the end of this century when food supply is sufficient. However, owing to non-linear synergistic effects of future acidification and upwelling of corrosive water, peak seawater pCO2 in Kiel Fjord and many other productive estuarine habitats could increase to values >400 Pa (>4000 µatm). These changes will most likely affect calcification and recruitment, and increase external shell dissolution.

Seawater carbonate chemistry and Bathymodiolus brevior shell variables near Eifuku volcano, Japan, 2009

Increasing atmospheric carbon dioxide levels are causing ocean acidification, compromising the ability of some marine organisms to build and maintain support structures as the equilibrium state of inorganic carbon moves away from calcium carbonate. Few marine organisms tolerate conditions where ocean pH falls significantly below today's value of about 8.1 and aragonite and calcite saturation values below 1. Here we report dense clusters of the vent mussel B. brevior in natural conditions of pH values between 5.36 and 7.29 on northwest Eifuku volcano, Mariana arc, where liquid carbon dioxide and hydrogen sulphide emerge in a hydrothermal setting. We find that both shell thickness and daily growth increments in shells from northwest Eifuku are only about half those recorded from mussels living in water with pH>7.8. Low pH may therefore also be implicated in metabolic impairment. We identify four-decade-old mussels, but suggest that the mussels can survive for so long only if their protective shell covering remains intact: crabs that could expose the underlying calcium carbonate to dissolution are absent from this setting. The mussels' ability to precipitate shells in such low-pH conditions is remarkable. Nevertheless, the vulnerability of molluscs to predators is likely to increase in a future ocean with low pH.

(Table S1) Stable isotope record and growth rates of cultured Mytilus edulis

To study the effects of temperature, salinity, and life processes (growth rates, size, metabolic effects, and physiological/genetic effects) on newly precipitated bivalve carbonate, we quantified shell isotopic chemistry of adult and juvenile animals of the intertidal bivalve Mytilus edulis (Blue mussel) collected alive from western Greenland and the central Gulf of Maine and cultured them under controlled conditions. Data for juvenile and adult M. edulis bivalves cultured in this study, and previously by Wanamaker et al. (2006, doi:10.1029/2005GC001189), yielded statistically identical paleotemperature relationships. On the basis of these experiments we have developed a species-specific paleotemperature equation for the bivalve M. edulis [T °C = 16.28 (±0.10) - 4.57 (±0.15) {d18Oc VPBD - d18Ow VSMOW} + 0.06 (±0.06) {d18Oc VPBD - d18Ow VSMOW}**2; r**2 = 0.99; N = 323; p < 0.0001]. Compared to the Kim and O'Neil (1997) inorganic calcite equation, M. edulis deposits its shell in isotope equilibrium (d18Ocalcite) with ambient water. Carbon isotopes (d13Ccalcite) from sampled shells were substantially more negative than predicted values, indicating an uptake of metabolic carbon into shell carbonate, and d13Ccalcite disequilibrium increased with increasing salinity. Sampled shells of M. edulis showed no significant trends in d18Ocalcite based on size, cultured growth rates, or geographic collection location, suggesting that vital effects do not affect d18Ocalcite in M. edulis. The broad modern and paleogeographic distribution of this bivalve, its abundance during the Holocene, and the lack of an intraspecies physiologic isotope effect demonstrated here make it an ideal nearshore paleoceanographic proxy throughout much of the North Atlantic Ocean.

Seawater carbonate chemistry and biological processes of Mytilus edulis during experiments, 2011

Ocean acidification (OA) resulting from anthropogenic emissions of carbon dioxide (CO2) has already lowered and is predicted to further lower surface ocean pH. There is a particular need to study effects of OA on organisms living in cold-water environments due to the higher solubility of CO2 at lower temperatures. Mussel larvae (Mytilus edulis) and shrimp larvae (Pandalus borealis) were kept under an ocean acidification scenario predicted for the year 2100 (pH 7.6) and compared against identical batches of organisms held under the current oceanic pH of 8.1, which acted as a control. The temperature was held at a constant 10°C in the mussel experiment and at 5°C in the shrimp experiment. There was no marked effect on fertilization success, development time, or abnormality to the D-shell stage, or on feeding of mussel larvae in the low-pH (pH 7.6) treatment. Mytilus edulis larvae were still able to develop a shell in seawater undersaturated with respect to aragonite (a mineral form of CaCO3), but the size of low-pH larvae was significantly smaller than in the control. After 2 mo of exposure the mussels were 28% smaller in the pH 7.6 treatment than in the control. The experiment with Pandalus borealis larvae ran from 1 through 35 days post hatch. Survival of shrimp larvae was not reduced after 5 wk of exposure to pH 7.6, but a significant delay in zoeal progression (development time) was observed.