The genus
According to Lange-Bertalot, in 2001 about 30 species were known from the genus
There is relatively little literature available on diatoms of the Raška River (Vidaković 2013; Vidaković et al. 2014), and there are no published data on the diatom microflora of the Mlava River. So far only five
The aim of this contribution was to collect and review information on the distribution and ecology of
The Raška River and the Mlava River belong to the Black Sea drainage basin. The Raška River is a tributary of the Ibar River in the southwestern part of Serbia. The Mlava River is a tributary of the Danube in eastern Serbia (Marković 1980). The rivers have a carbonate bedrock and run through trout ponds. Samples were collected at the sites located downstream and upstream of the trout ponds. Some of the sites are exposed to seasonal desiccation when the discharge drops.
Diatoms were sampled from 5 localities in the Raška and Mlava rivers in April, June, August, and November 2011, and March and May 2012. Epilithon and epibryon were considered in the Raška River, while only epilithon was sampled in the Mlava River. Samples were immediately fixed with formaldehyde to a final concentration of 4%. Conductivity, oxygen, pH, and water temperature were measured in the field. Hydrochemical analyses were carried out at the Institute of General and Physical Chemistry, University of Belgrade, following standard methods (APHA 1998). Diatom samples were treated according to standard methods to obtain permanent slides (Krammer & Lange-Bertalot 1986). Permanent slides, prepared material, and aliquots of the samples were deposited in the diatom collection of the University of Belgrade, Faculty of Biology.
Slides from the Raška (14 samples) and Mlava (8 samples) rivers were used for microscope observations. Light microscope observations and micrographs were made using a Zeiss AxioImagerM.1 microscope with DIC optics and AxioVision 4.8 software. SEM observations were made at the Institute of Physics, University of Belgrade, using a TESCAN MIRA 3 scanning electron microscope with maximum accelerating voltage of 30 kV. Sample surfaces were sputtered with gold using QUORUM TECHNOLOGIES MINI SPUTTERCOATER SC7620 for enhanced conductivity.
Trying to gather as much data on the distribution of
SEM: external view (Fig. 2b): Proximal ends of the raphe expanded and moderately deflected whilst distal ends are hooked. Striae uniseriate throughout. Areolae apertures as short slits (55-60 in 10 μm). Annulus evident as three rows of areolae larger than in stria areolae, apically elongated. In each row, from 3 to 6 apically elongated areolae are present.
SEM: internal view (Fig. 2 a and c): Distal raphe ends slightly deflected in a small, aureole-shaped helictoglossa, central raphe endings straight. Annulus structure with warty outgrowths.
Value ranges of physical and chemical parameters of the sites with – No data Data from the springs in the Alps were provided by Marco Cantonati.
Parameters/Sampling sites
Rivers in Serbia
Spring SE Alps (Trentino)
Springs Alpine foothills (Verona Province, Lessinia)
Springs in the south-western Alps
Raška River
Mlava River
AT0756
ML0622
DC1620
RF1477
MT1300
SB1050
MC1650
MC1652
MC1655
RP1800
Shading (1-5 scale)
2
1
1
1
4
3
1
1
1
2
Temperature (°C)
7.5-14
9.1-14.6
9.4
11
8.4
8.1
5.8
7
4
3.4
3.2
2
pH
7.02-8.23
6.95-7.95
7.6
7.3
8.4
7.39
8.33
8.31
8.48
8.56
8.43
8.9
Conductivity (μS cm-1)
305-420
389-490
356
411
200
105
125
175
198
200
201
170
Alkalinity (as mg CaCO3 l-1)
7-120.8
12.6-120.6
195
240
25
15.2
17.7
26
23
23
24
18.4
N-NH4+ (μg I-1)
<18.9-473.8
<18.9-355.8
< 20
<100
< 10
< 10
< 10
< 10
< 10
< 10
< 10
< 10
N-NO3- (μg I-1)
6300-7900
6900-9500
224
3160
45
147
481
565
361
373
230
319
TP (μg P I-1)
13.5-104.2
8.7-112.8
4
-
-
-
-
-
-
-
-
-
SRP (μg P I-1)
5.2-51.7
3.7-46.8
2
-
-
-
-
-
-
-
-
-
Cl-(mg l-1)
1.2-2.2
0.9-2
1.0
8.0
0.4
0.4
0.3
0.3
0.5
0.5
0.4
0.2
SO42-(mg l-1)
1.4-3.4
5.5-22.4
21.0
10.0
-
1.6
1.8
4.3
-
-
-
-
%
0.5-3
-
<0.2
4.5
1.0
2.3
0.2
0.5
1.0
0.8/0.5
0.5
0.8
Substrate
epil./epib.
epilithon
epilithon
epilithon
epilithon
epilithon
epilithon
epilithon
epilithon
epil./epib.
epilithon
epilithon
The morphological features of the
Our data increase the number of known sites of the species from 2 to 13, and the populations are no longer limited to the Alpine area.
The ecological characteristics of the new sites revealed that
Our data and observations provide insights into the niche of
A preference for carbonate stony substrate is confirmed, although it is shown that the species can thrive on bryophytes substrate as well.
The two main determinants for the species occurrence appear to be the carbonate nature of the catchments or aquifers of the environments colonized, and the ability of the species to be competitive in habitats (small springs) or microhabitats (river wetted surface and bryophytes) exposed to seasonal desiccation because of fluctuating and low discharge values.