Ferenc L. Forray

Evidence of long-term NAO influence on East-Central Europe winter precipitation from a guano-derived δ 15 N record

Currently there is a scarcity of paleo-records related to the North Atlantic Oscillation (NAO), particularly in East-Central Europe (ECE). Here we report δ15N analysis of guano from a cave in NW Romania with the intent of reconstructing past variation in ECE hydroclimate and examine NAO impacts on winter precipitation. We argue that the δ15N values of guano indicate that the nitrogen cycle is hydrologically controlled and the δ15N values likely reflect winter precipitation related to nitrogen mineralization prior to the growing season. Drier conditions indicated by δ15N values at AD 1848–1852 and AD 1880–1930 correspond to the positive phase of the NAO. The increased frequency of negative phases of the NAO between AD 1940–1975 is contemporaneous with higher δ15N values (wetter conditions). A 4‰ decrease in δ15N values at the end of the 1970’s corresponds to a strong reduction in precipitation associated with a shift from negative to positive phase of the NAO. Using the relationship between NAO index and δ15N values in guano for the instrumental period, we reconstructed NAO-like phases back to AD 1650. Our results advocate that δ15N values of guano offer a proxy of the NAO conditions in the more distant past, helping assess its predictability.

Water isotopic variability in Mallorca: a path to understanding past changes in hydroclimate

This paper reports the first results on δ18O and δ2H analysis of precipitations, cave drip waters, and groundwaters from sites in Mallorca (Balearic Islands, western Mediterranean), a key region for paleoclimate studies. Understanding the isotopic variability and the sources of moisture in modern climate systems is required to develop speleothem isotope-based climate reconstructions. The stable isotopic composition of precipitation was analyzed in samples collected between March 2012 and March 2013. The values are in the range reported by GNIP Palma station. Based on these results, the local meteoric water line δ2H = 7.9 (±0.3) δ18O + 10.8 (±2.5) was derived, with slightly lower slope than GMWL. The results help tracking two main sources of air masses affecting the study sites: rain events with the highest δ18O values (> –5 ‰) originate over the Mediterranean Sea, whereas the more depleted samples ( 50 m) limestone cap (Arta) exhibit more negative values. A well-homogenized aquifer supplied by rainwaters of both origins is clearly indicated by groundwater δ18O values, which show to be within 2.4 ‰ of the unweighted arithmetic mean of –7.4 ‰. Although limited, the isotopic data presented here constitute the baseline for future studies using speleothem δ18O records for western Mediterranean paleoclimate reconstructions.

A guano-derived δ13C and δ15N record of climate since the Medieval Warm Period in north-west Romania: A GUANO-DERIVED δ13C AND δ15N RECORD

A 285‐cm core of bat guano was recovered from Măgurici Cave in north‐west Romania and analyzed for δ13C, δ15N and pollen. Guano deposition occurred from AD 881 until 1240 and from AD 1651 to 2013, allowing for the interpretation of summer variations in precipitation and temperature during the Medieval Warm Period (MWP) and the Little Ice Age (LIA). A 2‰ increase in δ13C, 1.5‰ decrease in δ15N, and the presence of Ulmus, Quercus and Carpinus betulus indicate a warm and dry MWP occurred in the region. The lack of deposition during the beginning of the LIA suggests a possible climate‐induced change in prey availability resulting in bats vacating the cave. Variation of δ13C values between −25 and −23‰ at AD 1650 (LIA) indicates similar drier conditions as at the end of MWP. However, a 2‰ decrease in δ13C values that occurred between AD 1790 and 1900 suggests climate was trending towards wetter conditions at the end of the LIA. From AD 1938 to 2013, δ13C values appear to be more influenced by temperature, indicating that this parameter had a more significant effect on carbon discrimination than water availability.

Sulfur cave (Romania), an extreme environment with microbial mats in a Co2-H2S/O2 gas chemocline dominated by mycobacteria

Sulfur Cave (Puturosu Mountain, Romania) is an extreme environment, unique for displaying life in a gas chemocline. The lower part of the cave is filled with CO2, CH4, and H2S of mofettic origin, while the upper part contains air that floats above the heavier volcanic gasses. S° and H2SO4 (from sulfur-oxidation) cover the cave wall at and below the CO2-H2S:O2 gas/gas interface. On the cave wall, near the interface the pH is <1 and unusual microbial biofilms occur on the rock’s surface. We provide context information on the geology, mineralogy, chemistry and biology to better understand this unique environment. We have used X-ray diffraction, optical microscopy, scanning electron microscopy with EDAX capabilities, stable isotope analysis and 16S and 18S rDNA amplicon sequencing. The most common taxa in the microbial biofilms are Mycobacteria, Acidithiobacillus and Ferroplasmaceae. Liquid water in this system originates solely from condensation of water vapor onto the cave walls making inflow of organic carbon from outside unlikely. The most likely primary source of energy for this microbial community is sulfur oxidation with H2S and S° as main reductants and atmospheric O2 as the main oxidant. Ferric iron from the rock surface is another potential oxidant. In Sulfur Cave, gaseous CO2 (from mofettic emission) maintains the stability of the gas chemocline. Sulfur Cave biofilms can help the search for extreme life in the subsurface, near volcanic systems on Earth and Mars. The Sulfur Cave example shows that a habitable environment can be established underground in gas chemoclines near CO2-dominated gas discharge zones, where it can have a steady supply of water and energy.

Bat guano δ13C and δ15N values as climate proxy

The aim of the present study is to demonstrate the usefulness of stable carbon and nitrogen isotopes in bat guano as proxies for paleoclimate changes. We show a 2500-year record of environmental change in Romania using δ 13 C, δ 15 N, and (C:N) derived from precisely 14 C-dated bat guano cores recovered from Gaura cu Musca (GM), Zidită (ZC), and Magurici (MC) caves