Cyanobacteria Affect Unique Ancient Monuments
The tales of my studies in Rome are long and relate mainly to the triumphal column erected by Trajanus Caesar. During my visits there in 1988-1990, my colleagues from the restoration authorities in Rome worked intensively on cleaning the Titus Arch of Triumph in Forum Romanum. During my first visit there, in 1973, I felt deeply insulted, and was very angry at those who took away the candlestick of “my” Temple (Figs. 6.11.1, 6.11.2). Like the other tourists I passed below the Menorah relief and photographed it with the fine-grained sediment that had settled there by natural processes over hundreds of years.
During my visit in 1988 there was scaffolding around the monument. With the aid of my colleagues I got near to the candles of the Menorah and became once again the scientist interested in biodeterioration of the monument’s marble. The restorers cleaned off most of the layers of sediment from the relief (Figs. 6.11.3, 6.11.4). I assume that one can “blame” the chasmoendolithic cyanobacteria for the grave damage to our Menorah. In five of the seven branches of the Menorah the upper part with the apple-like part is missing. So are the heads of a few of the men carrying the temple’s artifacts. The cuts of the images carved in the marble are oblique and seem parallel to each other. It seems that there is a combination of joints in the marble and development of cyanobacteria in the fissures. As in the rocks in the Negev Desert described above, the organisms multiply, create internal pressure, open fissures, and form “calcite wedges” until breaking parts of the relief.
The restorers discovered stones that had fallen down from the relief, cleaned them and preserved them. On the stone in Fig. 6.11.5 one can see depressions with stains of dark compounds deposited by the cyanobacteria around their dwelling site. I would not declare it with such certainty were it not for my experience in Namibia in 1989. I participated in a conference in Namibia and went with a new friend (who had a red scale-ruler) to a vein of calcite. The owners of that area were probably laughing at our excitement. They obtained gold and diamonds from the rocks in that area and we “jumped for joy” when discovering cyanobacteria in the fissures among the large calcite crystals (Fig. 6.11.5 “1”). The interesting environmental peculiarity of that area is the almost zero rainfall. Due to the position of Namibia near a place where there are cold oceanic currents, hardly any showers fall in the coastal area. However, there are some 200 nights when dense fog brings humidity inland and facilitates the development of organisms well adapted to this kind of moisture input.
The cyanobacteria developing in the fissures among the calcite crystals are hidden from sight and unlike the organisms forming pits, there is no involvement of rain splashing out free calcite crystals. The mist water that condenses and drips into the fissures and crystal “2” in Fig. 6.11.7 enables the growth of cyanobacteria. The result seems to be dissolution and the formation of a depression on the crystal’s side, resembling the depression found in the stone below the relief of the Menorah in Rome. In both cases cyanobacteria promoted dissolution of calcite in the fissures.
Participation in a scientific conference in Didim, southern Turkey enabled me to reach a huge monument, well constructed from marble. The microorganisms that developed on the exposed walls caused its total blackening. Here and there one can see (Fig. 6.11.8) white corners of the wall stones. There are white dots on the wall stones. When approaching a white dot (Fig. 6.11.9) one can recognize the exfoliation surface, testifying to the activity of chasmoendolithic cyanobacteria. Hence, following the peeling of a “leaf” from the white zone, the finger points out the dark green cyanobacteria.