that both grew well in the range of 8-40‰ and did not show growth at 2‰ and below. Based
on these
experiments, the author concludes that although in the Baltic local populations are
constantly exposed to low salinity in the Baltic local populations are constantly exposed to low
salinity; this does not lead to the selection of special brackish races.
Discussion
Analyzing the findings of E. Paasche in the light of the hypothesis of E.Pora [Pora
, 1961
],
it can be assumed that the cause of this behavior of the clones of seaweeds is apparently
sought in the ratio of ions in the Baltic water (which, as is known, is close to the full-salt
oceanic water in composition to the full-salt oceanic water), which allows them to tolerate low
water tonicity (2 - 8%); This explains the presence in the Baltic Sea of the oceanic
representatives of other groups of organisms in the Baltic Sea.
In the Black Sea, and even more so in the Caspian Sea, diatom populations are under the
double influence of osmotic and ionic factors, which apparently should lead to the formation
of local populations characterized by physiological
responses, somewhat different from those
of populations from fully saline seas.
Preliminary experiments were conducted to establish the presence of growth of clones
on water with a different ionic composition, in which only a qualitative estimate of growth was
given. In these experiments, the cultures were exposed on the northeasterly window at room
temperature (18
℃). After establishing the fact of growth of the Black Sea and Caspian clones
on
the White Sea water, the ratio of clones to salinity by the fission rate was experimentally
estimated.
The culture of the Black Sea clone
C. granii, previously cultivated at 17‰ on the Black
Sea water, was transferred to medium with a salinity of 12 and 17‰, prepared in the Caspian
water (control was the culture of
S. granii cultivated at 17‰ on its own lead). In the
experimental cultures, a mass of "bare" small spherical bodies and
a slow cell death were
observed for several days. Similar was the behavior of the Black Sea
D.brightwellii, whose
culture in this experiment also died. Thus, the Caspian water proved to be unsuitable for the
Black Sea clones under study; this indicates that the Experiment Black Sea clones are not able
to carry water of a different ionic composition. We believe that it was the rapist factor that
was the barrier to the growth of the Black Sea clones to the Caspian water.
Similar results demonstrating the importance of ionic ratios for algae were obtained by
L.A. Lanskaya [Lanskaya
, 1969
], in whose experiments algae isolated from the Red and
Mediterranean seas were not easily adopted and soon died off with the same salinity, but on
the Black Sea water.
In subsequent experiments, we transferred two Black Sea clones into the White Sea
water. Preliminary experiments showed that both clones carry the White Sea water, and in the
appearance of the culture, no noticeable changes
were observed in the visual observation. One of
these clones (
D.brightwellii) was further
tested for
8 days at 11 saline points. Controls were cultures
on medium with a salinity of 17%, prepared both
on the Black Sea and on the White Sea water. The
growth rate constants were calculated for all
salinity points. It is interesting to note that, on the
whole, the Black Sea clone on the White Sea water
showed the same range of optimum (10-29%) as
on
the Black Sea water, however, the rates of
division of its cells at both the control and optimal
points were much lower than on the Black Sea
water (Fig.1). Thus, the results of the experiment
Figure 1. Rate of cell division of the Black
Sea clone
Ditylum brightwellii (West)
Grun. on the Black Sea (1) and White Sea
(2) waters of different salinity
18
described agree with the thesis of Z.Z. Finenko and L.A.Lanskaya [
Финенко et al., 1972
], that
algae are more intensively divisible by the water of the reservoir from which they were
isolated.
In this experiment,
D.brightwellii cells died at a salinity of 4%. In the lower limit of the
salinity range (13%), this seaweed in the White Sea water showed higher fission rates
compared to the same salinity on the Black Sea water. There are data [
Guillard R, 1970
] that a
small change in the ion composition stimulates the growth of diatoms in dilute media. Thus,
the form of the growth curve with a salinity of 4-8% can be different and depends to a large
extent on the ionic composition of the medium.
Microscopy of cultures in this experiment (to assess their state) showed that
D.brightwellii cells excellently tolerated salinity from 19 to 29%. Moreover, cells, usually single,
and in this range of salinity were connected in chains (8-16 cells each).
The Black Sea clone of
S. granii was also previously tested in medium on the White Sea
water and showed the ability to grow. Growth experiments with this clone were carried out on
the White Sea water at four salinity points corresponding to the average salinity
values of the
Caspian (12‰), Black (17‰) and White Sea (25‰), and average salinity of oceanic water -
34‰. Control was a culture that grew on the Black Sea water (17‰). The Black Sea clone of
S.
granii on the White Sea water also showed lower rates of cell division than on the Black Sea
water; the fission optimum was observed at average salinity values, approximately repeating
the growth optimum on the Black Sea water.
Caspian clones of
S. granii and
Th. nitzchioides in preliminary experiments showed the
ability to grow on the White Sea water. The main experiments were also carried out at four
salinity points. The control was a culture growing on a medium with a salinity of 12%, prepared
in the Caspian water. The results of the experiments are evident that the rates of division of
both Caspian clones on the White Sea water were lower compared
to the rates of division in
the Caspian water (Fig. 2). Optimum fission rates on the White Sea water were observed
approximately in the same salinity range as in the Caspian water.
Figure 2. A-
The rate of division of the cells of the Caspian clone
Coscinodiscus granii Gough in
the Caspian (1) and White Sea (2) waters of different salinity (3-control); B- Rate of cell division
of the Caspian clone
Thalassionema nitzchioides (Grun) Hust. on the Caspian (1) and White Sea
(2) waters of different salinity (3-control).
A comparison of the growth of the Black Sea and Caspian clones of
S. granii clearly
shows that the rates of division of both clones on the White Sea water were lower than on the
water of the reservoir from which they were isolated.
The cultivation of Caspian and Black Sea clones on the White Sea water, close in ionic
composition to typically marine, showed that the general nature
of the growth of cultures
under these conditions did not change, but the rate of cell division decreased markedly. The
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