Cluj-Napoca geologists chart climate changes using bat guano cave deposits

A team of geologists from the Babes-Bolyai University of Cluj-Napoca is conducting a research project that uses guano deposits in several Romanian caves, some of them more than 10,000 years old, to determine the climate changes occurred in various geological periods.

Photo credit: (c) Babes-Bolyai University project website

"We are trying to do paleoclimate and paleoenvironmental reconstructions based on guano (droppings) deposits produced by bat colonies during maternity season; sometimes, these deposits are more than two to three meters thick. Basically, using a core sampler we extract samples from the guano deposit we then analyse for pollen, charcoal content, but especially for carbon isotopes," explained project coordinator Bogdan Onac.

According to the researcher, the most important information comes from isotopic and pollen studies. Pollen gets into the guano deposit when water seeps through from the surface, carrying the grains inside the cave. Alternatively, pollen grains can also reach the guano via the insects consumed by the bats or on the fur of these mammals. The study of pollen can thus help obtain information about the vegetation that existed thousands of years ago in the surroundings of the investigated cave.

"The relationship between the isotopic signature of guano samples and climate is a complex one, which can be summarized as follows: the vegetation is consumed by insects, which in turn are the main food for bats. The carbon isotopic signature in plants depends on the type of photosynthesis, which in turn is influenced by rainfall, temperature, the atmospheric content of carbon dioxide, etc. As a result, the climatic signal archived in the vegetation is transferred into the guano via the food chain that connects...