Figure 1
Distribution of the sampling sites (VR1-VR6) along the Vrla River
Table 1
Dominance in diatom communities in the Vrla River at sites VR1-VR6 in 2011-2012, in six seasons
Figure 2
LM micrographs of G. acceptata. Scale bar = 10 μm
Table 2
Chemical water parameters of the Vrla River at the studied sites (VR1-VR6) in 2011-2012
| Parameter | VR1 | VR2 | VR3 | VR4 | VR5 | VR6 |
|---|---|---|---|---|---|---|
| Temperature (°C) | 2.2-13.0 | 2.3-12.4 | 2.0-15.0 | 2.3-15.2 | 2.5-15.5 | 2.0-17.3 |
| Conductivity (μS cm-1) | 50-90 | 50-80 | 60-100 | 60-90 | 60-90 | 70-110 |
| PH | 7.0-8.4 | 7.1-8.6 | 7.0-8.8 | 7.1-8.7 | 7.0-8.7 | 6.9-8.3 |
| Ammonia (mg l-1) | <0.01-0.15 | <0.01-0.13 | <0.01-0.26 | <0.01-0.16 | <0.01-0.18 | <0.01-0.10 |
| Nitrates (mg l-1) | 1.7-3.4 | 1.5-2.7 | 1.6-2.9 | 1.5-3.1 | 1.5-2.8 | 1.3-2.1 |
| Oxygen (mg l-1) | 9.4-15.1 | 9.2-14.8 | 9.0-13.9 | 9.0-14.2 | 9.1-14.3 | 8.8-13.3 |
| BOD5 (mg l-1) | 0.4-8.6 | <0.2-6.6 | <0.2-6.7 | 0.3-6.1 | 0.2-6.2 | 0.3-6.0 |
| Alkalinity (Mmoll-1) | 0.4-2.6 | 0.4-2.3 | 0.7-2.6 | 0.5-2.6 | 0.4-2.8 | 0.5-2.5 |
| Total P (mg Pl-1) | 0.03-0.06 | 0.02-0.07 | 0.02-0.09 | 0.02-0.05 | 0.02-0.07 | 0.02-0.07 |
| Orthophosphates (mg Pl-1) | 0.02-0.04 | 0.01-0.04 | 0.01-0.05 | 0.01-0.03 | 0.01-0.03 | 0.01-0.03 |
| Water hardness (°dH) | 0.12-12.01 | 0.15-11.79 | 0.22-11.79 | 0.16-11.79 | 0.16-12.24 | 0.16-12.24 |
Figure 3
Canonical correspondence analysis (CCA) biplot ordination on the basis of the measured environmental variables (temperature-T, conductivity, pH, total phosphorus-TP, O2, biochemical oxygen demand-BOD, NO3, alkalinity, water hardness-WH, orthophosphates-OP and ammonium) and diatom taxa recorded in the Vrla River, with sampling sites (VR1-VR6) and sampling seasons (S1-S6) as supplementary variables (F=1.4, P=0.0002). Due to the large number of data, the graphs A and B are not overlapped, and diatom taxa and explanatory variables (environmental data) are shown on graph A, while sampling sites and sampling seasons used as supplementary variables are shown on graph B for better visualization. NNOV – Navicula novaesiberica, GGRA – Gomphonema gracile, NEDU – Neidium dubium, CSAP – Cymatopleura solea var. apiculata, NVIR – Navicula viridula, NAAM – Navicula amphiceropsis, CBCU – Cymbopleura cuspidata, GANG – Gomphonema angustatum, NSAL – Navicula salinarum, EVUL – Encyonema vulgare, NOLI – Navicula oligotraphenta, NCTE – Navicula cryptotenella, CLAN – Caloneis lancettula, CAEX – Cymbella excisa, NACI – Nitzschia acicularis, NHEU – Nitzschia heufleriana, MAPE – Mayamaea atomus var. permitis, PLFR-Planothidium frequentissimum, GPRI – Gomphonema pumilum var. rigidum, ADDA – Psammothidium daonense, SJOU – Sellaphora radiosa, FCPL – Fragilaria recapitellata, AMJA – Achnanthidium minutissimum var. jackii, FCAP – Fragilaria capucina, DMON – Diatoma moniliformis, ACAF – Achnanthidium affine, DHIE – Diatoma hyemalis, SRPI – Staurosirella pinnata var. intercedens, SSVE – Staurosira venter, SBKU – Surirella brebissonii var. kuetzingii, CEXG – Cymbella exigua, DSEP – Diploneis separanda, CGLA – Handmannia glabriuscula, ACOP – Amphora copulata, GSCI – Gyrosigma sciotoense, LGOE – Luticola goeppertiana, GACU – Gomphonema acuminatum, FUAC – Fragilaria acus, CEPR – Cymbella excisa var. procera, CEXF – Cymbella excisiformis, ENCM – Encyonopsis microcephala, FSBH – Fallacia subhamulata, NHIN – Navicula hintzii, NZAD – Nitzschia adamata, NDOL – Nitzschia oligotraphenta, NREC – Nitzschia recta, SRMA – Martyana martyi
Figure 4
Redundancy analysis (RDA) of dominant diatom taxa and measured environmental variables (temperature-T, conductivity, pH, total phosphorus-TP, O2, biochemical oxygen demand-BOD, NO3, alkalinity, water hardness-WH, orthophosphates-OP and ammonium) with sampling sites (VR1-VR6) and sampling seasons (S1-S6) as supplementary variables. AMIN -Achnanthidium minutissimum, HARC – Hannaea arcus, NIPR – Nitzschia pura, ADSU – Achnanthidium subatomus, GELG – Gomphonema elegantissimum, GPRI – Gomphonema pumilum var. rigidum, PTLA – Planothidium lanceolatum, COPL – Cocconeis pseudolineata, MAPE – Mayamaea atomus var. permitis, CPLA – Cocconeis placentula var. placentula, CPLI – Cocconeis placentula var. lineata, NIAR – Nitzschia archibaldii, NZAB – Nitzschia abbreviata
Table 3
Average values of diatom indices and water quality classes at the studied sites (VR1-VR6) of the Vrla River in 2011-2012
| Site | Values of diatom indices / Water Quality Class | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| IPS | SLA | DESCY | CEE | IBD | TDI | IPS | SLA | DESCY | CEE | IBD | TDI | |
| VR1 | 16.55 | 13.38 | 15.71 | 15.31 | 17.15 | 55.1 | II | II | II | II | I | III |
| VR2 | 16.56 | 12.78 | 15.21 | 15.35 | 17.33 | 55.03 | II | III | II | II | I | III |
| VR3 | 15.43 | 12.63 | 15.55 | 13.91 | 14.76 | 56.56 | II | III | II | II | II | III |
| VR4 | 15.30 | 12.56 | 15.23 | 13.81 | 14.00 | 49.28 | II | III | II | II | II | III |
| VR5 | 15.25 | 13.28 | 15.76 | 13.63 | 13.76 | 47.73 | II | II | II | II | II | III |
| VR6 | 15.36 | 12.88 | 16.05 | 14.66 | 13.73 | 52.88 | II | III | II | II | II | III |