This study focusses on the plants in the open parts of the lake - mostly aquatic charophytes and mosses, in what are called in Lake Sevan (Armenia), the ”zones of chara and moss”. Distribution and other ecological conditions are reviewed. Quantity of chara in the littoral zone of lake Sevan is provide

Markoyan, A.K.

English

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MARKOSYAN A.K. 1951 
Rasprostranenie i biomassa kharovykh vodoroslei 
i mkha v os. Sevan. 
Extent and biomass of the aquatic chariphytes 
and mosses in lake Sevan. 
Trudy Sevanskoi gidrobiologicheskoi S tant s i i . Tom. 12 
pp. 29-34. 
Translated by J .J . Holmes 
FRESHWATER BIOLOGICAL ASSOCIATION. 
July, 1962. 
[page 29]. 
The littoral zones of Lake Sevan have been studied by Arnol'di 
(1929), Fridman (1948, 1950) and Markosyan (1947, 1948). The washing 
effect is on the average not deeper than 15m and on this depends the extent 
and depth of the macrophytes. 
The fundamental mass of this data is on the plants in the open parts 
of the lake - mostly aquatic charophytes and mosses, in what are called in 
Lake Sevan, the "zones of chara and moss". The extent of these zones is 
not the same in different parts of the lake. Along the eastern shore, where 
the bottom dips suddenly and the deep isobaths approach close to the shore, 
the aquatic charophytes occupy plots of from 6-17m deep, and the mosses to 
l8-19m. On the western and southern shores, where the bottom is more gently 
sloping and the deep isobaths lie a considerable way from the coastline, the 
chara and moss are found from 6-7m to 14m, and rarely up to 15m deep. 
The soil on which the chara and moss is native, is a sandy silt. 
Its origin, as indicated by Arnol'di, is due to the dying and decomposition 
of the macrophytes, giving rise to a silt of organic origin. 
Reduction of the water level of Lake Sevan, as shown in our own previous 
work, is not a disturbing effect, for the chara and moss of the littoral zones 
continue with the alteration of level and occupy the previous depths. 
At the present time the level of water in the lake is, by comparison 
with 1938, lower by 4m. As before, the chara and moss occupy plots on the 
bottom of the littoral zone of 6-7m to 14m on the western shores, and to 17m 
on the eastern shore. Such a pattern shows that the lowering of the level 
of the lake does not have a negative effect on the zones of chara and moss. 
Because of this situation, there naturally arises the question - what factors 
cause the spreading of the chara and moss in the littoral zone? 
We have observed in those of our open coastal regions of the lake which 
are almost constantly under the influence of breaking waves, that the zones of 
chara and moss commence at a depth of 6-7m. In parts of the lake which are 
sheltered from wave action (coves, bays) a different picture is revealed; 
2. 
here the chara and moss start at a depth of 1-2m. 
The fundamental factors limiting the upper-most boundary of extent 
in the chara and moss, of the open districts of the lake, to a depth of 
6-7m [page 30] are the violent actions of the breaking waves. In the 
waters of less than 6-7m thanks to the mechanical action of the surf, 
the underground of chara and moss is destroyed, and together with the silt 
on the bottom, is washed into the deep parts of the lake. 
The lower boundary of extent of the chara and moss, as we have already 
pointed out, is not the same in different regions of the lake. Along the 
eastern shore, where there are not any rivers falling into the lake, and 
where the transparency of the water is high, the chara and moss extend to 
19m, but by the western shore where the water is not so deep but is effected 
by rivers, they extend to only 14m deep. In spite of considerably lowering 
the level of the lake, the chara and moss are, as before, available at the 
same depths to which they previously grew. From this we see that the lower 
boundary of extent of water plants is determined by the depth to which the 
sunlight can penetrate the water. 
The littoral zone of the lake has a rich animal population, particularly 
Gammarus, which forms a fundamental component of the benthos and is the major 
food object of the Sevan front. 
The overwhelming mass of Gammarus is concentrated in the zones of chara 
and moss, where the undergrowth of these plants apparently create the most 
favourable conditions for existence. In this connection, the quantitative 
calculations of the chara and moss have a definite interest. 
Below (Table 1) we have the data on the biomass (wet weight) of the 
aquatic charophytes, received from material gathered during the March 1947 -
August 1948 series, taking two winter/spring and two summer periods. 
At the time when the material was collected, we carried out a round-
the-year observation on the chara vegetation and as shown by the data on the 
table, the largest amount of growth was concentrated into the winter. At the 
3. 
beginning of the year there took place, in almost all the regions of the 
lake, a sharp decrease in the quantity of chara, while in the second 
half of the year it began to increase. Thus, during the year the chara 
had one winter maximum biomass (240.2 g/m2) and one summer minimum 
(85.5g). 
The development of the chara in different parts of the lake is not 
the same, and the variation of biomass attained on 1m2 ranges from 10g at 
Sarykaya to 470g at Babadshan. 
On examination of the table it is obvious that the average annual 
biomass of lesser and greater Sevan is not the same, in the first there is 
an over-all average of 194.1 g/m2 while in the latter this is 130.6g. 
The area of the bottom of the lake limited by the 7-15m isobaths 
(Calculated for a lowering of the level by 4m) from the data by Kireeva (1933), 
total in Lesser Sevan 29Km2 and in Greater Sevan 54Km2. Accordingly, this 
is the area where there is always a rich population of aquatic charophytes, 
[page 31] the latest biomass of Lesser Sevan being 5050T and of Greater 
Sevan 6950T, giving a total of 12000T. 
The extent of the moss in Lake Sevan is similar to that of the aquatic 
charophytes. The quantitative data on their distribution in the lake (Table 2) 
was taken during the period January to August 1948. The material was gathered 
from 3 regions of the lake - Noradus, Areguni and Sarukaya. The first and 
second regions are in Lesser Sevan, the third in Greater Sevan. We compared 
the distribution of chara with moss in the separate regions of the lake, and 
discovered that it considerably exceeded the quantity of chara. For example, 
in the Noradus region the biomass on 1m2 exceeds that of the chara by about 
2.5 times and in all the rest of the lake by about two times. 
[page 32] At the time of collection we came across a considerable 
amount of dead material in the Noradus region, but less in the Areguni region. 
Apparently, here, owing to the steep dip in the bottom of the lake, the dead 
moss rapidly washes off into the lake depths, while in the Noradus region the 
4. 
dead moss remains and decomposes and is not swept away. 
The quantity of moss in Lesser Sevan is almost two times greater 
(401.9 g/m2) than in Greater Sevan (214.7 g). The average biomass for 
Lesser Sevan, taken over 8 months was 10,450 tons, while for Greater Sevan 
it was around 11,600 tons, giving a total for the whole lake of 22,050 tons. 
The average biomass of the chara and the moss therefore comes to 34,OOO 
tons. 
Examination of the chara and moss in the lake showed that there was 
considerably more plants in Lesser Sevan than in Greater Sevan. At the same 
time, two regions in Greater Sevan - Babadzhan and Sarykaya, the first on the 
eastern coast, the other on the western, are sharply distinguished between t 
on the quantitative distribution of chara. The chara is 4 times greater 
in the Babadzhan region than in Sarykaya. 
One reason for this is that in the Sarykaya region fishing is 
done with seine - nets, and every time are dragged from the lake onto the bank 
they bring up a great quantity of chara and moss together with Gammarus and 
other living creatures. 
Constant repetition of this results in the "ploughing" of the plots 
on the bottom and breaks the normal conditions of growth and development of the 
macrophytes. 
The best places for working with seine nets are on the western and 
southern shores of Greater Sevan. On the eastern shores of Greater Sevan and 
Lesser Sevan, it is not so good and the amount of netting done here is 
negligible. 
The use of seine nets to catch fish changes the conditions and way of 
life of the most productive zone of chara and moss. 
In order to avoid this the fishing organisations would have to use 
drift nets and shutter (0)(?) nets. 
Quantity of chara in the littoral zone of lake Sevan (g/m2). 
TABLE 1. 
TABLE 2. 
Quantitative development of moss in the littoral zones of L. Sevan. (g/m2). 
LITERATURE. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Notice 
 
 
Please note that these translations were produced to assist the scientific staff of the 
FBA (Freshwater Biological Association) in their research. These translations were 
done by scientific staff with relevant language skills and not by professional 
translators. 
 
 
 


Extent and biomass of the aquatic chariphytes and mosses in Lake Sevan [Translation from: Rasprostranenie i biomassa kharovykh vodoroslei i mkha v os. Sevan, 1951]

http://aquaticcommons.org/5028/1/os7_1951_mark_exte.pdf

Extent and biomass of the aquatic chariphytes and mosses in Lake Sevan [Translation from: Rasprostranenie i biomassa kharovykh vodoroslei i mkha v os. Sevan, 1951]

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