Supplemental Material: Carbon isotope excursions during the late Miocene recorded by lipids of marine Thaumarchaeota, Piedmont Basin, Mediterranean Sea

Geological setting, methodology, and lipid abundance, carbon stable isotopes, and sources (Tables S1–S4; Figures S1–S3).<br>

Supplemental Material: Carbon isotope excursions during the late Miocene recorded by lipids of marine Thaumarchaeota, Piedmont Basin, Mediterranean Sea

Geological setting, methodology, and lipid abundance, carbon stable isotopes, and sources (Tables S1–S4; Figures S1–S3).<br>

Stable isotopes of oxygen to characterize a Metalimnetic Oxygen Minimum: insights from a 48 hours field campaign at Rappbode Reservoir, Germany

&lt;div&gt;&lt;span&gt;The appearance of a Metalimnetic Oxygen Minimum (MOM) has been recorded in many natural lakes and reservoirs. However, its isotopic characterization with oxygen and carbon stable isotopes have not yet been fully constrained. The purpose of this work is to apply stable isotopes of carbon and oxygen to characterize photosynthetic and respiratory activities in the Rappbode Reservoir, Germany. Here we present the results of a 48 hours intensive sampling in July 2020. We provide preliminary data of dissolved oxygen (DO) concentration and saturation profiles, together with dissolved inorganic carbon (DIC). This includes data of oxygen (&lt;/span&gt;&lt;span&gt;&amp;#948;&lt;/span&gt;&lt;sup&gt;&lt;span&gt;18&lt;/span&gt;&lt;/sup&gt;&lt;span&gt;O&lt;sub&gt;DO&lt;/sub&gt;) and carbon (&lt;/span&gt;&lt;span&gt;&amp;#948;&lt;/span&gt;&lt;sup&gt;&lt;span&gt;13&lt;/span&gt;&lt;/sup&gt;&lt;span&gt;C&lt;sub&gt;DIC&lt;/sub&gt;) stable isotopes with particular focus on the metalimnion. Our profiles identified minor differences from day to day, such as an additional respiration-like peak above the MOM. Samples from within the MOM were characterized by the lowest oxygen content and saturation (7.05 mg L&lt;sup&gt;-1&lt;/sup&gt; and 75&amp;#160;%, respectively) and the highest &lt;/span&gt;&lt;span&gt;&amp;#948;&lt;/span&gt;&lt;sup&gt;&lt;span&gt;18&lt;/span&gt;&lt;/sup&gt;&lt;span&gt;O&lt;sub&gt;DO&lt;/sub&gt; (up to +30.1&amp;#8240;). These samples also showed the lowest &lt;/span&gt;&lt;span&gt;&amp;#948;&lt;/span&gt;&lt;sup&gt;&lt;span&gt;13&lt;/span&gt;&lt;/sup&gt;&lt;span&gt;C&lt;sub&gt;DIC &lt;/sub&gt;values (down to -12.8&amp;#8240;). Surface layers (between 0 and 9 meters) and the deepest water sample (65 meters) did not follow the expected depth profiles for &lt;/span&gt;&lt;span&gt;&amp;#948;&lt;/span&gt;&lt;sup&gt;&lt;span&gt;18&lt;/span&gt;&lt;/sup&gt;&lt;span&gt;O&lt;sub&gt;DO&lt;/sub&gt; and &lt;/span&gt;&lt;span&gt;&amp;#948;&lt;/span&gt;&lt;sup&gt;&lt;span&gt;13&lt;/span&gt;&lt;/sup&gt;&lt;span&gt;C&lt;sub&gt;DIC&lt;/sub&gt;. Surface layers were likely influenced by equilibration with the atmosphere that was enhanced by windy conditions. On the other hand, samples from 65 meters depth could have been perturbed by the presence of organic material from sediments. Moreover, oxygen and carbon stable isotopes patterns were able to show that the MOM can migrate within the water column up to 5 meters within 12 hours. These findings offer an interesting basis to establish mass balances of oxygen and carbon turnover in water bodies.&lt;/span&gt;&lt;/div&gt;

Oxygen and carbon stable isotopes of Mytilus galloprovincialis Lamarck, 1819 shells as environmental and provenance proxies

Mollusc shell stable isotopes are commonly used to reconstruct past environmental conditions. However, despite being abundant components of natural and anthropogenic fossil accumulations, the geochemical composition of mussel shells ( Mytilus spp.) has rarely received attention in palaeoenvironmental studies. This study tests the suitability of oxygen isotopes (δ18Os) of Mytilus galloprovincialis as palaeothermometer. For 1 year, mussels and water samples were collected twice a month from Berria Beach, in Northern Spain. The geochemical data of the shells indicate that water temperatures can be reconstructed with an average offset of 1.2 ± 0.7°C with respect to the measured values. Furthermore, no prolonged shell growth cessations are observed. These results validate M. galloprovincialis as reliable recorders of seasonal water temperature fluctuations, supporting their use in palaeoenvironmental studies. In addition, further shell and water collections were carried out in the upper and lower areas of a nearby estuary. The geochemical analyses of these shells were aimed to test whether oxygen and carbon stable isotopes (δ13Cs) may be used as novel proxies to identify the shell provenance at local scale. The results show that the δ18Os versus δ13Cs correlation direction varies along the coast–upper estuary geographical gradient, suggesting it to be a potential new proxy to distinguish between marine and estuarine mussel specimens.