[1] The Mg/Ca ratio within foraminiferal calcareous tests (shells) is widely used to reconstruct past seawater temperature. However, recent studies reported that the organic components within a test affect the Mg/Ca distribution. In this study, we have measured the Mg/Ca, Sr/Ca, and Ba/Ca ratios within the planktonic foraminifera Pulleniatina obliquiloculata by using a NanoSIMS (secondary ion mass spectrometer (SIMS)), which has excellent spatial resolution ($1 mm) and allows us to compare the distribution of chemical compositions with that of the organic components. Element compositions show banding distributions composed of alternately higher and lower values of those elemental ratios. The Mg/ Ca ratios, previously considered to be mainly controlled by calcification temperature, show larger variations than the values expected from the seawater temperature at the habitat depth of P. obliquiloculata. Comparison of the elemental distribution with the test microstructure reveals that the bands of high Mg/Ca and Sr/Ca ratios correspond with layers of the organic components. Such coincidence suggests that the organic components strongly affect the Mg/Ca and Sr/Ca ratios within a test. In spite of the heterogeneous distribution, temperature estimated from the averaged Mg/Ca ratio within a test is consistent with seawater temperature at the habitat depth of P. obliquiloculata, indicating that whole Mg/Ca ratio of foraminiferal test may be useful as paleotemperature proxy. In contrast to the Mg/Ca ratio the heterogenity in Ba/Ca ratio, which previously has been considered to be mainly controlled by the ambient seawater composition, is not fully matched with the layers of the organic compositions. Although the organic components concentrate Ba, other unknown factors appear to also cause heterogenity in Ba incorporation.Components: 5208 words, 6 figures.

The historical record of daily light cycle in tropical and subtropical regions is short. moreover, it remains difficult to extract this cycle in the past from natural archives such as biogenic marine carbonates. Here we describe the precise analysis of sr/Ca, mg/Ca, and Ba/Ca ratios in a cultivated giant clam shell, using a laterally high-resolution secondary ion mass spectrometer with 2 µm resolution. The sr/Ca ratio exhibits striking diurnal variations, reflecting the daily light cycle. A clear seasonal variation in sr/Ca is also observed in another longer set of measurements with 50 µm resolution. Light-enhanced calcification and elemental transportation processes, in giant clam and symbiotic algae, may explain these diurnal and annual variations. This opens the possibility to develop the sr/Ca ratio from a giant clam shell as an effective proxy for parameters of the daily light cycle.

Huge tsunami waves associated with megathrust earthquakes have a severe impact on shallow marine ecosystems. We investigated the impact of a tsunami generated by the 2011 M9.0 Tohoku-Oki earthquake on the seafloor and large benthic animals in muddy and sandy ria coasts (Otsuchi and Funakoshi bays) in northeastern Japan. We conducted underwater field surveys using scuba equipment in water depths of <20 m before the tsunami (September 2010) and after the tsunami (September 2011 and September 2012). During the study period, episodic changes in topography and grain-size composition occurred on the seafloor of the study area. Megabenthos sampling revealed a distinct pattern of distribution succession for each benthic species. For example, the protobranch bivalve Yoldia notabilis (Bivalvia: Nuculanidae) and the heterodont bivalve Felaniella usta (Bivalvia: Ungulinidae) disappeared after the tsunami event, whereas the distribution of the venus clam Gomphina melanaegis (Bivalvia: Veneridae) remained unchanged. In addition, the patterns of succession for a single species, such as the giant button top shell Umbonium costatum (Gastropoda: Trochidae) and the heart urchin Echinocardium cordatum (Echinoidea: Loveniidae), varied between the two bays studied. Our data also show that reestablishment of some benthic animal populations began within 18 months of the tsunami disturbance.

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Tridacna derasa shells show a crossed lamellar microstructure consisting of three hierarchical lamellar structural orders. The mineral part is intimately intergrown with 0.9 wt% organics, namely polysaccharides, glycosylated and unglycosylated proteins and lipids, identified by Fourier transform infrared spectrometry. Transmission electron microscopy shows nanometre-sized grains with irregular grain boundaries and abundant voids. Twinning is observed across all spatial scales and results in a spread of the crystal orientation angles. Electron backscatter diffraction analysis shows a strong fibre texture with the [001] axes of aragonite aligned radially to the shell surface. The aragonitic [100] and [010] axes are oriented randomly around [001]. The random orientation of anisotropic crystallographic directions in this plane reduces anisotropy of the Young's modulus and adds to the optimization of mechanical properties of bivalve shells.

To detect the relationship between ambient temperature and otolith stable oxygen isotope (δ O, −0.17 ‰) were lower, but were not significantly different from those of larvae reared in + 0.31 ‰ water, which is the δ 18 O value of the water in which the spawners were raised. These results suggest that the sample size for the 32 psu experiment was too small and that the rearing durations were too short to affect the otoliths completely. Our results demonstrate that otolith δ

Recent dynamical models of Solar System evolution and isotope studies of rock-forming elements in meteorites have suggested that volatile-rich asteroids formed in the outer Solar System beyond Jupiter's orbit, despite being currently located in the main asteroid belt 1-4 . The ambient temperature under which asteroids formed is a crucial diagnostic to pinpoint the original location of asteroids and is potentially determined by the abundance of volatiles they contain. In particular, abundances and 13 C/ 12 C ratios of carbonates in meteorites record the abundances of carbonbearing volatile species in their parent asteroids. However, the sources of carbon for these carbonates remain poorly understood 5-8 . Here we show that the Tagish Lake meteorite contains abundant carbonates with consistently high 13 C/ 12 C ratios. The high abundance of 13 C-rich carbonates in Tagish Lake excludes organic matter as their main carbon source 5,9 . Therefore, the Tagish Lake parent body, presumably a D-type asteroid 10 , must have accreted a large amount of 13 C-rich CO2 ice. The estimated 13 C/ 12 C and CO2/H2O ratios of ice in Tagish Lake are similar to those of cometary ice 11,12 . Thus, we infer that at least some D-type asteroids formed in the cold outer Solar System and were subsequently transported into the inner Solar System owing to an orbital instability of the giant planets 1,3 .We performed in situ C-isotope measurements on individual grains of carbonate minerals, calcite (CaCO3) and dolomite (CaMg(CO3)2), in Tagish Lake, an ungrouped carbonaceous chondrite (CC) with a petrologic type of 2, indicating that it underwent aqueous alteration 13,14 (Methods). For comparison, we also conducted C-and O-isotope measurements on calcite grains in two Mighei-type carbonaceous chondrites (CM chondrites) with a petrologic type of 2, Nogoya and LaPaz Icefield (LAP) 031166. Due to the small grain size of Tagish Lake carbonates, we were not able to measure O isotopic ratios ( Supplementary Fig. 1). The  13 C and  18 O values ( 13 C/ 12 C and 17,18 O/ 16 O ratios are also expressed as  13 CVPDB and  17,18 OVSMOW, respectively, which represent permil, 10 -3 expressed as ‰, deviations from the isotopic ratios of standard materials: VPDB, Vienna Pee Dee Belemnite; VSMOW, Vienna Standard Mean Ocean Water) of CM carbonates are highly variable, ranging from approximately 20 to 80‰ and from approximately 15 to 40‰, respectively, and do not correlate with each other (Fig. 1a and Supplementary Table 1).The O-isotope data of CM carbonates plot on a single trend line (Fig. 1b), reflecting a change in formation temperatures and/or in the O isotopic ratios of fluids from which they formed. Therefore, the lack of correlation between  13 C and  18 O indicates that the variable  13 C values of CM carbonates must reflect isotopic heterogeneity of carbon sources (Methods). In contrast to CM carbonates, Tagish Lake carbonates have 478, 218-220 (2011). 28. Dauphas, N. The isotopic nature of the Earth's accreting material through time. Nature 541, 5...

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