A description is given of an experimental ecosystem, or Etekos, which was developed at the Moscow University. The experiment lasted about one year, and the results obtained are itemized

Alekseyev, V. V.

Sapozhnikov, V. V.

English

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NASA TECHNICAL MEMORANDUM
	
NASA TM-76079
I
ETEKOS EXPERIMENTAL ECOSYSTEM
V. V. Alekseyev and V. V. Sapozhnikov
(NASA-T'1-76079)	 ETdKCS EXPEillMENTAL
ECOSYSTEM (National APronautiCS dnd Space
Administration)
	 11 p iIC A02/MF A01 CSCL 133,
NBJ-21893
Uilcldj
65/45 4b861
Translation of "Eksperimental'naya ekosistema 'Etekos'",Priroda,
No. 10, Oct. 1979, pp 70-75
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NATIONAL AERONAUTICS AND SPACE ADMINISTRA	 l	 L.,
WASRINGTON, D. C. 20546	 _ IJA^tC	 gg^s
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EXPERIMENTAL ECOSYSTEM "ETEKOS"
By
V. V. A lekseyev and V. V. Sapozhnikov
^ •R1
•	 -r
Vyachesla- Viktorovich Alekseyev, doctor of physical /70*
and mathematical sciences, senior scientist of physics
department of M. V. Lomonosov Moscow State University,
Biophysicist engaged in mathematical modeling of bio-
geocenoses. Author of a number of monographs including
Dinamicheskiye modeli vodnykh bio eotsenozov L"Dynamic
Models of Aquatic B iogeocenoses" , Moscow-, 1976.
Viktor Vol'fovich Sapozhnikov, candidate of geographical
sciences, senior scientist of geographical department
of the same university. Specialist in hydrochemistry
of reservoirs on dry land and oceans.
^• T
Disru ption in the equilibrium in nature as a consequence of environmental
pollution with industrial., agricultural and general wastes has induced enormous
interest in the basic research of ecological problems, that can only be solved by
the joint efforts of different specialties: physicists, chemists, biologists and
so forth. The main information on the ecosystems has been obtained as a result of
Numbers in margin indicate pagination in original foreign text.
1
41$ IK N.,IR Ql.i'AJ DIY
IFlan of Experimental Unit for Studying Ecosystems 	 /71
1--system of air conditioning; 2--controllable system of illumination (soffit
made of 56 fluorescent lamps); 3--xenon lamps moving over arches; 4--electric
motors turning rod with probe and advancing it over the vertical; 5--movable post
with oxygen sensors (oxymeters); 6--sampler; 7- -probe to determine pH, dissolved
oxygen and temperature; 8--electrical heaters; 9--instrument for determination of
water transparency; 10--photoelements to determine light intensity.
observations in nature. However observations are the first, but far from the
most effective method of study. The possibility of obtaining the maximum quanti-
tative informatio,1 and passing to construction of a mythematical model of the
phenomenon is only provided by experiments.
2
The first experiments were made with ecosystems made of microsco-)ic organisms.
In 1912 L. L. V udreff for the first time gave a quantitative description of the
successive change in population of Protozoa in a hzy extract under the influence of
a change in the medium of the populat1on and its organisms. He observed how
numerous flagellates are replaced by varying types of colpodae, and then parade-
.	 cia who are successively replaced by Hypotricha Irfusoria, amoebae and Vorti-
cellae.
A further stage in the development of this type of experiment was the study
of closed micro-ecosystems (volume about 250 ml and more) that require for their
development only light energy, as well as the study of the organisms developing
in the chemostats and turbidostats of different types with controllable influx and
efflux of nutrients. 1 A shortcoming of these systems--spatial heterogeneity of
different physical and chemical properties of the medium. This shortcoming can
be overcome only with the creation of basins of large capacity.
A study of the water biocenosis in a closed basin affords the possibility of
	 /72
tracing the interaction between the components of the oco.3ystem under conditions
close to the natural, but without any external interferences.
In the Moscow University in a special basin of the hydrophysics laboratory
of the physic:. department the collective of authors (V. V. A lekseyev, Yu. I. Gor-
batov, A. A. Georgiyev, M. Ya. Lyamin, V. N. Maksimov and V. V. Sapozhnikov) of the
physics, biological and geographic departments have created a unit for study of
ecosyofams--the experimental ecosystem or Etekos.
In the formation of the structure of the aquatic ecosystem an important role
is played by the vertical distribution of illumination intensity and temperature,
and the intensity of turbulent exchange at different depths--factors that can be
altered only in a basin of sufficiently large dimensions.
The working basin of Etokos is a reservoir of volume jAx3=36 m3 . The basin
itself and the air chamber above it are insulated from the environment. The water
can be heated from below and cooled from above, so that in the system conditions
can be created that are stable in time and uniform in space. However, this pattern,
as a rule, rarely is realized in nature. It is much more interesting to have a
medium in which the temperature, illumination intensity, and intensity of turbu-
]ant exchange are altered with depth. For this the illumination intensity and
^ Iachurkin, N. N. Populyatsionnaya mikrobiologiya ["Population Microbiology"]
Novosibirsk, 1978.
3
Vertical Distributions of Tomparature in Three Days after Engagement of
Fluorescent lamps and with Engagement of Conditioner. Air temperature in
chamber is lower .han in upper layer of water. Due to cooling in the upper
layer of water convective movement begins--an isothermic layer develops (shown
by gray color).
temperature are regulated with the help of a soffit made of 56 fluorescent lamps
of 40 w each. The light falling at an angle to the horizontal surface is created
by lamps whose radiation spectrum can be regulated in certain limits. These
lamps can be moved on the circumference.
The conditioner can maintain a certain temperature and humidity in the air
chamber and at the same time alter the intensity of the convective exchange in
the water Lhat occurs with its cooling from above.
Nutrient salts can be added to the system, or by adding distilled water their
concer. + ration can be reduced, which is very convenient for studying the changes
in the ecosystems that occur, for example, with eutrophication of reservoirs, i.e.,
with an increase in the concentration of nutrient salts in the water.
An important component of the unit is the original complex of measuring
apparatus.
The first group includes physical and chemical parameters whose measurement
is completely automated: temporature and illumination intensity at different
depths, rH values and oxidation-reduction potential of the medium, concentration
of dissolved oxygen. The measurement results are recorded by self-recorders.
4
IThe second group of parameters comprises concentrations of different bio-
genic elements. yn rrinciple their measurements are standard and can be auto-
mated. However, at the given stage the chemical analyses are made manually. With
the help of the sampler, a polyethylene Piro 0.5 cm in diameter, the samples are
taken from the necessary level and further are sent to the chemical laboratory.
The hydrochemical analyses include determination of the organic and mineral forms
of phosphorous and nitrogen, dissolved silicic acid, dissolved amino acids, etc.
Finally, the third group includes primarily the biological parameters--c on-
eentrations of different types of phyto- and zooplankton. Determination of these
parameters is exceptionally difficult to automate. For example, the species
composition of the phytoplankton can be determined only with the help of a micro-
	 X73
scope. However, determination of the amount of primary product or the quantity of
newly formed organic substance is successfully automated. To determine the primary
product of photosynthesis in situ G. G. Shinkar and V. V. Saponhnikov have suggested
a special instrument--productiometer that is two glass tubes (dark and light) through
which water is pumped. By knowing the concentration of oxygen at the inlet into
the system (0 in ) and the concentration of oxygen at the outlet from the dark (0dk
and light tubes (O lt ) one can easily compute the complete product (01t-0dk)' the
pure product (O lt -O in) and the destruction (0in-0dk). The use of this instrument
makes it possible to conduct continuous recording of the product of the photo-
synthesizing algae and evaluate the rate of the destruction processes, or the
amount of biochemical consumption of oxygen in the dark tube. By measuring at
the inlet and outlet from the productlometer not only the concentration of oxygen
but also phosphorous, nitrogen, a;, well as the PH of water, etc. one can evaluate
	
/74
the effect of the processes of photosynthesis on the utilization and regeneration
of the main biogenic rDmponents.
It is understandable that '0 it inin) and (0in-0dk) will be determined by the
time of stay of the water in the tubes. In order to determine more accurately the
momentary value it is necessary to make this time (exposure) less. With large
exposures we obtain the average values of the product for a long time and will
not know the fine structure of the oscillations of the product in time.
A serious method problem in studying the ecosystem is the varying degree of
accuracy of the obtained results and the varying degree of effect of the measure-
ment process on the syste.n. The sensors for temperature measurement can be made
so small that they permit measurement of temperature gradients in a layer of
5
pH 7.3 73 80 75 80
—^
aC1,	 i
_j
7 5 8.0 7.5 8.0
I
I00"r
75 8.0	 75 8,0 75 80 75 80
—_r
If
a
I
chlorella	 I,a phn ia.
Sys 1
	
3	 15
	
30	 37
	 1	 45	 62	 173	 22,
	
C 20 20 25 20 25 20 25 20 25 30 20 25 30 20 25 	 20 25
	
20
I	 I	 i^	 1
p;]"120 too
	 100
	 * 00 _ ,00	 .00 100	 200 100	 100
	 100
icj, µg at/1	 20 25
	 20 25	 20 25	 20
Fmin
	
P com	 I^	 ^-ti
Course of Ecological Experiment
Vertical distribution of temperature, pH, concentration of dissclved oxygen
LO 1, mineral LF	 , and complete phosphorous Lip	 J. Due to the fact that
ni?rates were inm Rie water in a surplus, their concentration during the experiment
changed little, and therefore they are not shown on the figure. At the initial
moment in time all the parameters were uniform.. On the first day of the experi-
ment biogenic elements were added to the water (nitrate--KNO and phosphate--KHZOO
As a consequence of heating the reservoir in the upper layer 3of water (50 cm)
a so-callad thermocline was formed, the concentration of oxygen was reduced due
to the reduction in its solubility with a rise in temperature; the nH rose since
the content of carbon dioxide in the water was reduced.
In two weeks algae (chlorella) were added to the basin: intensive produc-
tion of O2 by the algae began.
In 1.5 months ; ,aphnia were added to the system; they feed on chlorella. This
led to a reduction in oxygen production, decrease in the pH maximum and gradual
stabilization of the system.
water less than a millimater thick (for example, with their help one can find
a cold film on the surface induced by water evaporation). The oxygen sensors
that are a galvaniz3d call made of two electrodes (silver --cath)de and lead--
anode) immersed in a solution of alkali cannot be made small enough. In addition,
the oxygen near the sensor is rapidly consumed, and its constant influx is needed,
therefore it is necessary to install the sensors on mobile noles. Thus, the
6
Ot"' ,t . A'3 .
Pole with Thermal Sensors to Measure Temperature at Different Depths
area of disturbances created by the oxygen sensor is great as compared to the
area of disturbances created by the temperature sensor. Although our sampler
is significantly better than a bathometer, it also introduces strong disturbances
since during the taking of samples 500-800 ml of water are suctioned off.
The ecological experiment we described lasted about a year. The lamps
were turned on for the entire experiment. This made it possible to simplify
the interpretation of the findings, since the question of diurnal changes in
	 /75
the parameters was removed.
I.
	
	 In the beginning of the experiment all the indices were uniform regardless
of depth. The water was supersaturated with oxygen, its concentration rezchod
120% of the equilibrium value, with a temperature of 20 0
 it was 11 mg/l. Nitrate
(KNO 3) and potassium phosphate (KH 2PO4 ) wore added to the water. Heating by the
;amps of the surface layer led fairly ra p idly to formation of a stable stratifi-
cation with respect to the vertical. The concentration of oxygen in the upper
7
layer was reduced due to the fact that the solubility of the molecular oxygen
drops with an increase in temperature.
Roughly in two weeks in the basin algae were added (chlorella). In a week after
the entrance of the algae due to intensive photosynthesis at a death of 40 cm the
maximum content of oxygen was observed (up to 222%). The maximum pH (8.4) was
located somewhat higher, at a depth of 20 cm. Evidently, this is a result of two
processes: impoverishment of the upper layer of CO
2 
due to reduction in its solu-
bility with an increase in temperature and utilization cS CO 2 in the process of
photosynthesis. In nature, (for example, in the Mozhayskiy reservoir) the surface
layer to a depth of 1-2 m is usually mixed, and there the maximums of oxygen and
pH coincide with depth.
In 1.5 months after the start of the experiment Daphnia were placed into the
basin; they feed on chlorella. The balance between the production cf oxygen by
photosynthesis and the consumption of oxygen for respiration of the Laphnia and
oxidation of the organic substance was disrupted. The oxygen concentration in the
upper layer beKEM to drop drastically, and in 20 days oxygen surersaturation was no
longer observed. The concentration of oxygen in the upper meter layer was just below
100%, which indicated the dominant role of the zooplankton.
In the last phase of the experiment such a production-destruction equilibrium
was formed where an insignificant quantity of oxygen released during photosynthesis
was immediately consumed for respiration and oxidation of organic residues falling
out of all links in the food chain (bacteria, phyto- and zooplankton). Impoverish-
ment was noted of the surface layer (0-60 cm) of all forms of nitrogen: there was
a sharp reduction in the concentration of nitrates, nitrites appeared whose concen-
tration was increased depending on depth.
Thus, the processes occurring in the basin simulated well the analogous processes
in natural reservoirs. The studies conducted in the basin indicated the great
potentialities of the Etokos unit: the experiment can be re ­,eated, the conditions
can be controlled, the measurements can be made in considerable more detail than
in nature. In developing these studies one can obtain the necessary coefficients
for compilation of a mathematical model of water biocenosis. Construction of such
a model will permit control of the hydrochemical and hydrobiological pattern of
reservoirs, and consequently, control and prediction of the water quality. This
system can be useful for working out and comparing different types of techniques
8
s	 ^^
N '
Mobile Probe for Measuring Temperature, pH and 02
proposed for monitoring the environment. Knowledge of the details of the pro-
duction-destruction process is necessary in controlling synthesis of organi-:
substances in the photosynthetic layer in order to more efficiently use solar
energy. Acceleration of the turnovor of organic substance in such an ortimized
ecosystem (due to reduction in the number of trophic le 3els) will make it
possible to accumulate a considerable quantity of organic carbon in the bottom
deposits. Thus, one can obtain a biochemical energy source in which the aprro-
priate bottom microorganisms will break down the organic substance into methane
and CO2' As a result solar energy is transformed into a convenient fuel--metharo.
Nature provides us with finished samples of such a fuel element--this is lolease
of methane from the bottom silts of eutrophic reservoirs and stagnant reservoirs.
The deep-water lake Kivu in Central Africa is already being used as a source of
gas. Its water contains 60 billion m3
 of methane in the dissolved form.
Recommended Literature
Alekseyov, V. V. Chelovek 
-1 b1QSLer_ L"Man and the Biosphore"], Moscow, 1973.
Terskov, I. A. at al., EksperK mental ' nyye ek_clogicheskiy system, vklyuchayushchiyo
chelovoka L"Experimental Ecological Systems Including Man"J, Vol. 28,
Moscow, 1975•
Aleksoyev, V. V. at al., "Experimental Ecosystem 'ETEKOS'," Biologichesklye nauki,
No. 7 (1979)
'(' /A,^,^ /	 i.^n1-1 St 3 p AlA 3 4 A	 R	 9


ETEKOS experimental ecosystem

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