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A unique combination of light and algae in the Rosh Nikara cave - the National Science Foundation

Measuring the light reflected from the algae makes it possible to calculate the light used for photosynthesis

Light and algae in the Rosh Hankara cave. Photo by Prof. Zvi Dubinsky and the other researchers.
Light and algae in the Rosh Hankara cave. Photo by Prof. Zvi Dubinsky

Light penetrates the depth of the Rosh Hankara cave in three ways, different in their properties. Direct sunlight penetrates deep into the cave only towards sunset, and on days when the sun sets in the direction of the cave. In all seasons and at all times of the day, light reflected from the surface of the water penetrates the cave, and its intensity increases the closer the sun is to the horizon. In addition, light penetrates the cave that passes through the water that fills the lower part of the cave. Therefore, the light field in the cave changes from hour to hour, and from day to day in its intensity and composition of colors.

On the walls of the cave, and in the seawater in its flooded part, there is a colorful algae population, unique and diverse in terms of the species that make it up and in terms of the pigments adapted to the special lighting conditions in the cave.

For the purpose of measuring and characterizing these light sources, sensitive spectrometric and polarimetric equipment was purchased and adapted. The researchers also placed automatic temperature and humidity sensors at the sampling sites. In the laboratory of Prof. Sophia Barinova at the University of Haifa, the algae species that make up the algae population will be characterized, using advanced molecular methods. This makes it possible, for the first time, to document the species of algae that make up the plant community unique to the cave. The algae samples are collected separately from each lighting area in order to diagnose the compatibility of the different species and their pigment colors with the dominant light colors at the point from which they were collected. In these places, the researchers placed suitable tiles for the development of the algae to determine their settlement rates and growth speed. The tiles are collected for this purpose at regular intervals and distributed to the two laboratories partnering in the research: molecular taxonomy in Prof. Barinova's laboratory at the University of Haifa, where clean cultures of each species will also be grown separately, and transferred to the photobiology and ecophysiology laboratory of Professors Zvi Dubinsky from Bar Ilan University, and David Iloz from Bar Ilan University and Beit Berel College, where the postdoctoral student Said Abu Ghosh and the doctoral student Efrat Goldstein also work and research.

The characterization of the photosynthetic pigments of the algae is carried out using chromatography adapted to the separation and quantification of these pigments. At Bar Ilan University, with the help of a research grant from the National Science Foundation, the optical and physiological properties that allow the different species of algae to thrive in the different areas of the cave are being examined in terms of the light regime characteristic of each of them.

Using unique equipment developed by the laboratory team, the limits of the ability of the different algae species to withstand the low lighting conditions are investigated, thanks to high quantum utilization in low light conditions, and in the different compositions of the color spectrum of the light field. Highly sensitive spectrophotometric equipment makes it possible to measure in every area of ​​the cave the intensity and composition of the light hitting the algae in the different areas. Measuring the light reflected from the algae makes it possible to calculate the light used for photosynthesis.

The compositions of the light field and the different species are compared to those found in sea caves studied at other sites in the world. Based on the results of the research, suggestions will be formulated on how to preserve the flora of the Nikara and also ways to avoid harming it with the lighting installed for the safety of visitors.

During the performance of two certified works by Daniel Meir and Hamzi Asfor, the special and unknown nature of the field of light in the Rosh Neikara cave became clear. These findings, which dealt only with the light field, led the researchers to formulate the current research proposal.

Life itself:

Prof. Dubinsky, a marine biologist, is a well-known photographer, and his works have been exhibited in several galleries in Israel. He has published many covers in scientific journals. "I started taking pictures when I received my first camera as a bar mitzvah gift," he says. "For me, the camera was a natural part of the eye, not a technical accessory."

His scientific activities brought him to sites such as active volcanoes in Hawaii and Sicily, the frozen landscapes of Antarctica and coral reefs in Micronesia, Mexico, Bermuda and Australia. The practice of science, the study of natural phenomena and familiarity with the structure of matter, made Dubinsky's eye a "knowing" eye in the biblical sense. He does not watch from the side, but connects with the forces of nature, feels intimacy in front of the photographed subject, and delights in its structure, texture and the light playing on it.

  • The postdoctoral researcher Dr. Abu Ghosh is a Jordanian citizen who was an outstanding doctoral student in Prof. Dubinsky's laboratory at Bar Ilan University.

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