by Vladimir AVILOV, Dr. Sc. (Tech.), Svetlana AVILOVA, Dr. Sc. (Biol.), chief research associates of the RAS Institute of Oceanology named after P. Shirshov

The World Ocean is one of the few unique natural complexes on the Earth. It is many-sided: it rouses genuine interest and admiration, its depth and power heats up imagination, it can be home, food and safe shelter for its inhabitants. Water surface of the World Ocean covers approximately 71 percent of the Earth and is full of enigmas even today. And it is no wonder: man traversed seas and oceans, fished there for thousands of years, but its studies began only three centuries ago.

Marine science arose with the development and implementation of new technologies: methods and devices to measure depths (plummet) and take water samples (sampler), successfully carried out by Admiral Stepan Makarov (1849-1904), founder of national oceanography. Achievements made in the branch of marine science we are speaking about–bio-geochemistry–are also attributed to the development of innovative research methods. Chemical research works started with the discovery of an exceptional property of the ocean water body–constant salt composition that, according to many scientists (for example Alexander Vinogradov, member of the USSR AS (from 1953), specialist in the field of analytical chemistry and geometry), remained unchanged for the last 250 mln years. Even though this hypothesis was first formulated by English chemist Robert Boyle in the 1670s, it still has no comprehensive scientific substantiation.

The 1970s are considered a milestone in national marine science. Thus, in the course of numerous expeditions on the ships of scientific fleet, national scientists gathered an immense volume of actual data published in 1997 on the initiative of Andrei Monin (Academician from 2000), Director of the RAS Institute of Oceanology named after P. Shirshov, in a ten-volume monograph Oceanology. It included the whole extent of knowledge on the main perspective problems on the subject collected by scientists from all over the world. Further improvement of marine research methods and equipment significantly expanded our knowledge on distribution of the dissolved and suspended organic substance (OS) in the water body that has a number of representative characteristics, including organic carbon (C_org).

Field studies of that time once again confirmed the following ocean regularities: maximal content of the OS is characteristic for a photosynthesis layer, especially for littoral and highly productive areas (C_org 〉 100 mkg/1); the deeper the water body is, the lower is the content of the OS (below 1,000 m 〈50 mkg/1). In general, there is a direct correlation between the content of the OS in deep waters and the volume of phytoplankton production in the surface layer.

As a result, there was developed a general scheme of formation and transformation of the OS in the ocean. Its main producer is phytoplankton. Primary products are observed in the euphotic zone (0-200 m) owing to a photosynthetic activity of the latter, which undergoes a complex process of disposal through trophic chains. Fragments of living organisms (detritus) go down to lightless depths where they are consumed by detritus eaters that in turn are eaten by carnivores. Consequently, the speed of transformation of the OS in the intermediate and deep waters is rather slow, bacterial activity is very low and oxidation of the organic substance is slowed down.

But some researchers noted: there are layers (clouds) of concentrated life in water layers. As early as in 1967, French oceanographer Jean-Louis Fellous discovered a high concentration of yeast organisms and explained this phenomenon by the Somalian Stream. The American researcher David Karl, who in the 1970s studied distribution of the content of the adenosine triphosphoric acid (ATA) in oceanic profiles, traced some irregularities and attributed them to oxygen minimums. A number of regularities were identified by national biologists (Yuri Sorokin, Nikolai Parin, Larisa Ponomareva and many others), who carried out experiments at hundreds of deep water stations: biotope of the phytocene* is inhabited by active cells producing the organic substance; deeper waters contain algae that do not participate in the creation of initial products. Plus a conclusion based on scientific observations made by the afore-mentioned Sorokin: microflora as a whole and its specific groups are distributed rather unevenly. At a depth of 450-550 m in the Pacific Ocean near the upper limit of the intermediate Antarctic waters, he noted a steady maximum of the biomass and explained it in the following way: owing to the increase in a density gradient, settling organic particles of the suspended matter and dying cells characterized by an almost neutral floatability are accumulated (like on the liquid bottom), which creates more favorable conditions for nutrition of the bacterial plankton than in

* Phytocene biotope–an upper layer to the depth of the lower pycno-cline border (the layer of an abrupt change of water thickness at a depth of 20-80 m).–Ed.

the upper or underlying layers. In the mid-1970s, when studying the water body of the western basin of the Indian Ocean, famous national biologists Irina Mitskevich and Anatoly Kriss detected an increased density of the saprophyte microflora consuming detritus at a depth of 300-500 m and near the upper limit of the layer lying at 1,000-1,500 m. Data on the maximal concentrations of heterotrophic organisms discovered by national and foreign scientists in all oceans are gathered in the monograph The Microbiological Oceanography by Anatoly Kriss (1976). The author assumed that their existence and reasons of formation are associated with different hydrolog-ical and hydrochemical factors.

In other words, segmentary observations fitted in the existing scheme, therefore, scientists did not attach essential importance to them. The general process was still perceived as a solid one: the organic substance is formed only in the upper photic layer of the ocean; everything found in the underlying layers is its derivates. Besides, deep waters were regarded as carriers of biogenic remains to bottom sediments.

However, the available information was not enough to understand the essence of oceanic processes. That is why we chose a complex methodology to study the suspended organic substance that involved determination of the most significant biochemical indicators and gaseous components*. Besides, we developed new compensatory samplers that guaranteed impermeability of sea water samples and designed other equipment suitable for ship conditions. After all these preparations in March-July 1976 we set off to the Indian Ocean on board the survey vessel Academician Kurchatov**.

During this expedition more than 20 modern research methods were applied. Presence of the adenosine triphosphate (a universal energy carrier contained only in living cells), enzyme activity (lipolytic, amylolytic, proteolytic and alkaline phosphomonoesterase) and concentration of protein, carbohydrates and phosphorus, gas components (helium, hydrogen, argon, carbon dioxide, permanent and hydrocarbon mixtures) were detected by a specific and highly sensitive method. Two forms of the organic substance were studied: dissolved and suspended

* See: A. Geodekyan, V. Avilov, S. Avilova, "The Ocean Through the Eyes of the Geoecologist", Science in Russia, No. 1, 1993.–Ed.

** See: V. Avilov, S. Avilova, "Ocean Floor Life", Science in Russia, No. 3, 2001.–Ed.

(a conventional difference between them is set by letting water through filters with pores of 1.45-1.0 mkm). The first type includes filtrate compounds, the second one–substance on the filter cleared from big fragments (more than 200 mkm). Let's point out: for the purpose of studies of the dissolved OS we developed a new sephadex method (sephadex–a neutral substance composed of grains of different size) that enabled us to extract delicately the dissolved substance while keeping its native (proper) characteristics, which in turn made it possible to break down its composition by a molecular weight and determine the activity level of extracellular enzymes in each fraction. Obtained data were published in The Oceanology magazine (1977). Scientists of 20 countries got interested in the article.

To ensure authenticity of data, we introduced a notion "active living substance". It is characterized by a quantitative index–biomass of organisms measured by the ATT. Let us clarify: in early 20th century oceanologists tried to determine the ratio between the live and lifeless in the suspended matter, for example, in the plankton. They used methods based on the microscopy. But at that time they could not safely separate a living cell from a dead one that resulted in some inaccurate results. The share of living cells in the suspended matter determined by our method was 1-28 percent and reached 100 percent in the photic layer in the flowering period. The newly developed ATT method totally changed the situation as it made possible to identify living cells and determine the number of microorganisms in water with the accuracy exceeding 10 percent.

We made all measurements in the water body from the surface to the bottom at almost all stations located along the route of the ship. Surprising results were obtained in the Red Sea at the depths of 1,000 and 2,030 m, at the equator (1,500 and 4,900 m), over the Mascarene Range (3,800 and 1,200 m) and at the latitude of the Madagascar Island (500 m). Compared with the surrounding waters, the ATT content in all said layers was increased and sometimes even exceeded concentration in the photic zone: from 10 (2.5) to 60 ng/1 (15 mkgC/1). The ratio between the active living substance and organic carbon (up to 80 percent) that showed an extremely high share of the OS in the suspended matter was one more fact that did not fit in the generally accepted concept. An increased function of local microorganisms could be

compared to that in the Peruvian upwelling–one of the most productive regions of the World Ocean. The similar situation was observed in the distribution of protein: its content was 0.8-3.0 mkg/1 and the share of suspended C_org reached 20 percent. These and other important field experiments indicated formation of the active living substance in the intermediate and deep waters. Moreover, measured concentrations and ratio of the ATT, protein and C_org in the studied samples did not pertain to initial products in the photic layer.

Let's continue. In the vertical profiles activity of alkaline phosphomonoesterase decreased while descending deeper. We traced a direct correlation between this index and protein content but did not identify any relation to the presence of phosphorus (P) in the suspended matter. We observed it only when P was also available in lifeless components of the suspended matter. In this case concentration of phosphorus exceeded common indexes of 0.02 mkg/1 and reached abnormal 0.14. High lipolytic activity was observed in different layers of the ocean down to the bottom and amylolytic activity (decomposition of starch) was directly related to its concentration but had nothing in common with the content of carbohydrates within the limits of 0.7-4.3 mkg/1. We also measured four types of extracellular enzyme activity, which proved to be 2-3 times lower than in the living substance.

Results of the experiments showed a good physiological state of the local community of microorganisms which totally changed all perceptions on the processes going on in the sea water and led us to a discovery registered in 1996 under No. 92 with a priority as compared with 1976. Its essence consists in substantiation and validation of the conclusion that bacterial activity of microorganisms characterized by a chemolitoautotroph-ic metabolism (using inorganic compounds) and living in the intermediate and deep waters of the World Ocean produces an active living substance.

This phenomenon is not directly related to the photosynthesis in the surface layer but depends on the streams of substance and energy released in the course of degassing processes of the Earth. The studies showed abnormally high concentrations of gaseous components and the ATT some meters above the bottom and their dependence on underground processes in active geody-namical zones, including benthic layers of the mid-oceanic ridge of the Indian Ocean.

However, production of organic substances was not registered at all research points. In some places we observed a typical attenuation of life in deeper water layers. At some points–at a depth of 500 m–we found layers with abnormally high concentrations of suspended C_org and protein (71.4 mkg/1) with an analytical absence of the ATT. Rich sea waters of the Persian Gulf and the Gulf of Oman are drawn into the intermediate and deep waters of the Arabian Sea: microorganisms find themselves in a stress situation and die, which affects the ATT concentration; that is the reason why the suspended organic substance is represented by detritus (in this case protein does not have enough time to decompose). Thus, natural processes in the ocean are more complex than we used to think.

Eight years later we formulated a hypothesis that later on was confirmed by American researchers David Karl and George Knauer: during in situ experiments conducted at layers lying at depths of 500 and 1,100 m, they observed spotted points with an increased function of microorganisms that allowed them to conclude that there was produced organic carbon in the ocean depths.

Even though we discovered production of the OS in the deep and intermediate waters 30 years ago, many researchers did not pay adequate significance to this phenomenon. Meanwhile, it sheds light on the general issues of geoecology of the World Ocean and gives the basis to study it as a single global system that means that all its layers are inhabited by living organisms. Their interaction and interrelation with the common environment is accompanied by identical processes, in particular, formation of the bacterial plankton that produces its own initial products. Moreover, our complex studies have shown: the ocean has its own mechanisms of transfer of hereditary information (a unique characteristic of a living organism). This function is executed by dissolved organic compounds (for example, extracellular enzymes) and specific groups of microorganisms.

One more thing. Authors of the article now and then put forward an idea to create an Ecological International Reserve in the central deep water regions of all oceans to preserve a unique microbial community. It becomes more and more necessary while decoding new genomes, after discovery of the effect of "horizontal transfer" of genes, where microbiota is supposedly playing the main role. This idea is of current interest due to an increasing anthropogenic contamination of the Earth and need for constant ecological monitoring. Creation of such water areas will contribute to preservation of the biosphere and, finally, the gene pool of our planet.