Lacul Negru din Munţii Vrancei. O posibilă rezervaţie ştiinţifică. Această depresiune lacustră s-a format prin alunecarea unui versant, favorizată de litologia dominată de gresia de Kliwa. Din punct de vedere morfometric este un lac mic (13 300 m2 şi o adâncime de maximum 6,5). Importanţa sa rezidă în biodiversitatea floristică de pe insula plutitoare care acoperă  40% din suprafaţa lacului. Unele aspecte reflectă evoluţii specifice unor anumite condiţii paleoclimatice

Ciurescu, Stefan

Lupascu, Gheorghe

Roman, Florin

Roman, Nicolae Aurelian

English

Scientific Annals of "Alexandru Ioan Cuza" University of Iasi

ANALELE ŞTIINTIFICE ALE UNIVERSITĂŢII „AL I. CUZA” IAŞI 
Tom L III, s. II – c , Geografie 2007 
 
THE NEGRU LAKE FROM VRANCEA MOUNTAINS. A POSSIBLE 
SCIENTIFIC RESERVE. 
 
Florin Roman, Ştefan Ciurescu, Gheorghe Lupaşcu, 
 Aurelian-Nicolae Roman 
 
ICAS Focşani, 
 APM Vrancea,  
Faculty of Geography and Geology, 
 „Al.I.Cuza”  University of Iaşi 
 
Rezumat : Lacul Negru din Munţii Vrancei. O posibilă rezervaţie ştiinţifică. 
Această depresiune lacustră s-a format prin alunecarea unui versant, favorizată de 
litologia dominată de gresia de Kliwa. Din punct de vedere morfometric este un lac mic 
(13 300 m
2
 şi o adâncime de maximum 6,5). Importanţa sa rezidă în biodiversitatea 
floristică de pe insula plutitoare care acoperă  40% din suprafaţa lacului. Unele aspecte 
reflectă evoluţii specifice unor anumite condiţii paleoclimatice. 
 
Key words : Negru Lake, slide, biodiversity, scientific reserve 
 
Position and genesis of the lake 
 
The Lake Negru of Vrancea Mountains, also known as “Lacul cu 
Plamână”, i.e. Lake with marsh trefoil (Menyanthes trifoliata), is situated in 
the upper basin of Năruja River, at an altitude of 1215 m, on the left slope of 
the peak of the left slope of the peak of the Negru Hill (1548-1517 m), at the 
intersection of the geographical coordinates of 45
051’ N and 26027’ E, in a 
mixed forest (coniferous and deciduous trees), on the territory of Nistoreşti 
Commune, Vrancea Department, in the Natural  reserve of Nărujei Gorges, 
created as a consequence of the Decision of Departmental Council of Vrancea 
no. 12/18.09.1992, belonging to the Forrest District of Năruja. 
The geological substratum dates from the Oligocene age - Kliwa grit 
stone, disodil and menilit alternating, as parts of Via Draci structure – 
(Geological map of Romania Socialist Republic, 1:200,00, Covasna map sheet, 
1970), strata being arranged according to Hill Negru. 
 The lake’s genesis was due to a dry (stratification) landslide, 
consequent, of large proportion, that moved an important mass of frost-
shattered blocks coming especially from the Kliwa grit stone, using as a 
gliding surface the layer of disodil. 
76       FLORIN ROMAN, ŞTEFAN CIURESCU, GHEORGHE LUPAŞCU, A-N.ROMAN 
The landslide closed from the left slide and laterally a versant valley 
thus interrupting the drainage of the surface waters that had a torrential regime. 
 The landslide process may have occurred at the beginning of The Late 
Glacial Age (Upper Pleistocene), being favored by the periglacials 
morphoclimatic conditions. 
 
Morphometric and hydrological characteristics 
The lacustrine depression is approximately triangular in shape, its tip 
pointing north. Its transversal section is asymmetrical, in the sense that the 
western slope (hogback) is short and abrupt, while the opposite slope (of 25-
30
0
), corresponding to the landslide, is stabilized and completely covered by 
wood. The lakes receives water from upstream, from a rivulet discharging the 
waters infiltrated in the frost-shattered blocks (deposited in the closed sloping 
valley) and from the left slide, receiving the water infiltrated in the landslide. 
In the same time, the lake has an emissary – Negru Rivulet – which 
allows the evacuation of a flow that is approximately equal to the one taken by 
the lake. At around 250 m downstream, the rivulet goes through an important 
slope break, with specific lithological and structural features. 
 
 
 
The lake’s water is transparent up to the depth of at least 3 m, and on 
27.07.1995 the researchers registered a temperature of 7.5
0
C and a pH of 6-
6.5 in the water (Şt. Ciurescu). Rough measurements have shown that the 
surface of the lake is around 13,300 m
2
 of whom about half (47,78%) is 
77               THE NEGRU LAKE FROM VRANCEA MOUNTAINS… 
 
water luster (6100 m
2
), almost all the other half is covered by moss with 
varied spatial development (5,350 m
2
) while the rest (13,9%) is represented 
by littoral silting (1850 m
2
). 
In the upper half of the water luster numerous old bodies of dislocated 
trees are present (mostly resinous trees), making up a support for the present 
submersed and emerged vegetation – in this case Menyanthes trifoliata. 
The lacustrine depression has a maximum depth of 6.5 m in the central 
area. It is significant that its bottom has 2-3 dorsal-like arranged 
longitudinally, situated on the eastern side. They may represent either 
landslides of nival horseshoes or other pre-existing, preserved microforms of 
relief (fig. 2). 
 
 
 
The layer of moss that covers discontinuously the border of the 
depression, has an external part, anchored on the landslide, and an internal, 
floating part, which suggest the floating inley mentioned above. On the south-
eastern side of the lake (the lower one-third), the moss layer is much better 
developed, making up an unitary surface around 4500 m
2
. 
 
78       FLORIN ROMAN, ŞTEFAN CIURESCU, GHEORGHE LUPAŞCU, A-N.ROMAN 
Hydrobiological characteristics 
The Lake Negru special feature is the large variety of micro- and macro-
flora, of micro- and macro-fauna, of which the following were determined until 
now (Ciurescu, 1994-1995): 
 
I. Phytoplancton 
The division of Bacillariophyta (diatoms) 
1. Tabellaria fenestrate var. intermedia, 2. Pinnularia nobilis, 3. Limophora 
debilis, 4. Eunotia praerupta, 5. Meridion circulare var. constricta, 6. Diatoma 
vulgare, 7. Cymbella cistula, 8. Sydimosphaenia geminata (mountainous species). 
The division of Chlorophyta (green algae) 
1. Micrasterias denticulate, 2. Cosmarium praemorsum, 3. Mothrix tenerrima. 
 
II. Zooplnakton 
The class Crustaceeans: 
 Order: Cladocera, genus:  Daphnia, Moina; 
 Order: Copepoda, genus:  Eucyclops, Paracyclops; 
 Order: Amphipoda, genus:  Rivulogammarus; 
The class Hirudinea: leeches 
 
III. Zoobenthos 
The class Turbellaria 
 Order: Triclade, specie:  Planaria alpina; 
The class Nematomorphae 
 Order: Gordiide, specie:  Gordius acuaticus; 
The class Insects (larvae) 
 Order: Plecoptera, Odonata, Trichoptera ; 
 
IV. Terrestrial invertebrates 
The class Insects: 
 Order: Lepidoptera, species:  Apatura iris L., Nymphalis antiopa L., 
Lymenties anonyma Lew., Neptis rivularis L., Polygonia C-Album L., Inachis io 
L., Aglais urticae L., Papilio machaon L., Leptidea sinapsis l.; 
 Order: Macoptera, specie: Panorpa communis L. 
 
The emerged vegetation that is part of the south-eastern floating islet 
shows the presence of numerous moss species, of which the genus Sphagnum is 
predominant: 6 species out of the total of 9 (determined by Gheorghe Mihai – 
Iaşi, 1983), which are: 
 
79               THE NEGRU LAKE FROM VRANCEA MOUNTAINS… 
 
 
 
 
80       FLORIN ROMAN, ŞTEFAN CIURESCU, GHEORGHE LUPAŞCU, A-N.ROMAN 
The family Sphagnaceae 1. Sphagnum girgensohnii Russ., 2.  
Squarrosum crome, 3. S. palustre L., 4. S.falax (klinggr.) Kling., 5. S.flexuosum 
Roy et Molk., 6. S. magellanicum Bird.; 
 
The family Marchantiaceae 7. Marchantia polymorpha L.; 
 The family Amblystegiacaea 8. Salliersgon giganteum (Schimp.) 
 The family Polytrichaceae 9. Polytrichum commune Hadw 
 
At the same time one can notice the presence of numerous 
cyperaceous plants, for instance Etyophorum vaginatum. Menyanthes 
trifoliate, of the family Gentianaceae and the salicae are abundant on the 
entire surface covered by moss. Towards the inside of the floating islet there 
are rare of Picea abies, which become more and more dystrophic as they reach 
further away from the shore. 
In the lakeside area of the layer of moss one can notice a belt of 
ericaceae (Vaccinium myrtillus L., V. vitis idaea L., V. uliginosum L. – 
bilberry and cowberry bushes) associated with Menyanthes trifoliate, which is 
a glacial relic. 
It is interesting that the south-eastern floating islet floats on a water 
layer whose depth increases from the lakeside towards the inside of the 
lacustrine depression, i.e. from approximately 1 m in the lakeside area to 
around 3 m in the area of water glade, to further reach the depth of 6.5 m 
inside the lacustrine depression. In the same direction (from the lakeside 
towards the center of the lake) spreads the floating islet, tending to close ove 
the water glade. 
This series of hydrobiological strata ends with a stratum of brown 
sapric peat, whose thickness varies from 1.5 to 2.8 m (provisional values) and 
which covers the relief of the mineral substratum. In fact, the surface of the 
substratum of peat corresponds to the bottom of the Lake Negru. 
The Negru Lake, which can be considered an oligotrophic swamp, is 
made up of three layers arranged as follows (fig. 5): 
1. the upper layer, of moss (the floating islet), with a depth of up to 
1.5 m, made up mostly of Sphagnum. 
2. the intermediary layer, of free water, whose depth is of 1-3 m in the 
medium part. 
3. the bottom layer, made up of brown sapric peat, whose depth varies 
between 1 and 2.8 m (its end was not reached), wich covers most of the bottom 
of the lacustrine depression. 
 
81               THE NEGRU LAKE FROM VRANCEA MOUNTAINS… 
 
Conclusions: 
 
Unlike what we know in Romania about oligotrophic swamps, the one 
from the lacustrine depression of the lake known as Lacul Negru (Lake Negru or 
Black Lake), from vrancea Mountainsis remarkable for its really special 
situation: the interposing of the intermediary layer of free water between the 
covering layer of moss (making up a floating islet) and the bottom layer of 
sapric peat. On the other hand, the process of slow silting with moss of this 
lacustrine depression holds the record in Europe, being the most southern one. 
 
This hydrobiological an biological situation is unique in Romania due to 
a set of factors (the morphohydroclimatic one and the time), wich have cotrolled 
the lake’s genetic processes and phenomena. 
In a first phase, corresponding, probably, to the early Late Glacial 
Period, by the appearing of the natural dam, there were created the favorable 
conditions for the formation of the sapric peat, which represents now the bottom 
layer of original peat or paleopeat. 
In a second stage, of favorable conditions for an important collection of 
both underground and surface water, the gliding of frost-shattered blocks was 
reactivated, and, with the over-rising of the dam, the sapric peat from the bottom 
was covered by a thick layer of water (6.5 m), being preserved. 
In a third stage, corresponding to the present period, the conditions have 
started to be convenient for the genesis of a new generation of peat, over the 
intermediary layer of free water. Under these circumstances, numerous trees 
were dislocated in the submersion, thus increasing the quantity of biological 
material in the lake. This phase is also coected to the advancing of the layer of 
moss with Sphagnum towards the inside of the lacustrine depression, along with 
the thickening of the floating islet. 
As it appears as a whole, Lake Negru from Vrancea Mountains attests 
the existence of a climax state evolving towards a slow biological clogging, 
due to the oxygenation of the water by means of the following sources: 1. the 
contact of more than 6000 m
2
 of water glade with the atmosphere; 2. the 
upstream rivulet; 3. the average yearly temperature of 5
0
C; 4. the 
photosynthesis of the algae. 
Thus, we consider that the data presented above are arguments in favor 
of declaring the Lake Negru a scientific reserve. 
 
 
 
82       FLORIN ROMAN, ŞTEFAN CIURESCU, GHEORGHE LUPAŞCU, A-N.ROMAN 
References 
 
Gâştescu P., (1971), Lacurile din România. Limnologie generală (Romanian 
Lakes. Regional Limnology), Edit. Academiei, Bucureşti 
Pop E., (1960), Mlaştinile de turbă din R.P.Română (Romanian Peat Swamps), 
Edit. Academiei, Bucureşti 
Roman F., (1989), Munţii Vrancei – ghid turistic (Vrancea Mountains – A 
Tourists’ Guide), Edit. Sport-Turism, Bucureşti 
*** (1987), Geografia României (Romania Geography), tome III, Edit. 
Academiei, Bucureşti 
*** (1970), Harta geologică a R.S.R (Romania Geological Map), 1:200,000, 
Covasna map sheet, Geological Institute, Bucureşti 
 


The Negru Lake from Vrancea Mountains. A possible scientific reserve

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The Negru Lake from Vrancea Mountains. A possible scientific reserve

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Scientific Annals of "Alexandru Ioan Cuza" University of Iasi