The composition of the benthic fauna in the biggest Polish rivers, such as the Vistula and the Oder, clearly changes due to the invasion of alien species from various groups e.g. crustaceans (Konopacka 1998; Jażdżewski et al. 2004; Konopacka 2004; Bącela et al. 2008; Grabowski et al. 2007; 2009), oligochaetous clitellates (formerly Oligochaeta) (Dumnicka 2016; Jabłońska et al. 2015) or mollusks (Piechocki, Szlauer-Łukaszewska 2016), as well as due to the water quality improvement (Absalon, Matysik 2007; Pająk 2016; Schöll 2003). These biological changes have not been documented in the Upper Vistula – the stretch of the Vistula between the mouth of the Przemsza River (95 km of the water course) and the San River mouth (368 km). For many years, this river section has been heavily polluted, mainly by sewage from the Upper Silesian Industrial Region and saline waters from coal mines. Water chemistry of the Upper Vistula has been studied many times (see Kasza, Galas 2002), especially within the shorter stretch between the Przemsza River (95 km) and Kraków (165 km), over a distance of ca. 70 km, and has regularly been monitored by the Regional Inspectorate for Environmental Protection. Research on the composition of benthic invertebrates was performed only twice, between 96 km and 158 km by Zięba & Zaćwilichowska (1966) and between 128 km and 153 km of the river course by Dumnicka & Kownacki (1988). In addition, the composition of oligochaete fauna throughout the Upper Vistula was discussed by Dumnicka (2002). According to Kownacki (1999), the smaller number of species recorded from the Upper Vistula was caused by a high level of pollution, but also by insufficient knowledge about its benthic fauna. Based on the published data and available manuscripts, the author compiled a checklist of taxa found in particular sections of the Vistula, from the sources to the estuary.
The objective of this work was to summarize changes in the composition of benthic invertebrates in the Upper Vistula during the last 50 years. An attempt was also made to determine the rate and directions of these changes.
Research on water chemistry and benthic fauna composition was carried out twice (14 July and 16 December 2014) at 187 km of the Upper Vistula between the town of Oświęcim (96 km) and the town of Szczucin (283 km) (Fig. 1). On the same days, samples were collected from the Gostynka River (heavily polluted by saline mine waters), 100 m upstream from the place where it flows into the Vistula, at 93 km of its course. Moreover, on 2 August 2017, mollusks were collected in the mouth of the Skawinka River (150 km of the Vistula). Water temperature and conductivity were measured in situ using a portable instrument Hi 98312 (Hanna Instr. Inc. Woonsocket-RI-USA). The content of inorganic ions (Cl−, SO42−, HCO3−, NO3−, PO4−, NH4+, Na+, K+, Ca2+, Mg2+) was analyzed using the ion chromatography (DIONEX ICS 1000 and IC DX 320). The remaining parameters of water were determined by classic methods according to APHA (1992).
Qualitative samples of benthic fauna were collected from all habitats using a bottom scraper (20 cm × 20 cm) with 0.3 mm mesh net. In the laboratory, specimens were isolated from the sediments and identified under a stereoscopic microscope to the family level. Selected groups were identified to the species level using the following identification keys depending on the group: Amphipoda (Konopacka 2004), oligochaetous clitellates (Timm 2009), Mollusca (Piechocki, Wawrzyniak-Wydrowska 2016).
In the river section between Oświęcim and Kraków (Fig. 1), the highest values of organic pollution, expressed as BOD5, were recorded in the 1960s when water oxygenation was at the lowest level (Bombówna, Wróbel 1966) (Table 1). Subsequent studies showed a slow improvement in the water oxygenation as well as a smaller amount of organic matter (Kasza 1988; Kasza, Galas 2002) and this trend continues to this day (Table 1).
Comparison of selected chemical water parameters in the Upper Vistula over 50 years (based on literature data,
min.–max values) after Bombówna, Wróbel 1966; after Kasza 1988; after Krokowski et al. 1994; after Kasza, Galas 2002 mean monthly values of conductivity from January to September 1994;
Parameter
Study period
1962–1963
1982–1983
1988–1994
1996–1997
km from the sources
96–158
128–153
160
116–248
Conductivity
μS cm−1
200–1300
no data
2000–5600
400–4300
Cl−
mg dm−3
33–747
250–1400
65–2200
500–1300
O2
0.4–10.0
1.6–13.1
no data
4–12
BOD5
mg O2 dm−3
3–60
4.0–28
no data
4–10
Contrary to organic pollution, water salinity in this section of the Upper Vistula (between 96 km and 165 km) was increasing until the 1990s (Kasza 1988; Gajowiec, Różkowski 1988; Krokowski et al. 1994) (Table 1), and the sodium-chloride type of waters has been confirmed since the mid-20th century (Bombówna, Wróbel 1966). The concentrations of chloride ions at particular sites varied strongly depending on the discharge values (Krokowski et al. 1994). During our study, a very high conductivity value and concentrations of chloride, sodium and sulfate ions were determined in the Gostynka River (Table 2). In the Vistula, all the above-mentioned parameters showed lower concentrations compared to the previous studies (Kasza, Galas 2002) but values of the majority of measured parameters exceeded the limit values for class II of water quality (Dziennik Ustaw 2016).
Chemical characteristics of water at the studied localities in 2014
Parameter
Locality
Gostynka R.
Oświęcim
Czernichów
Szczucin
14 July
14 July
16 Dec.
14 July
16 Dec.
14 July
16 Dec.
km from the sources
91
96
140
283
Conductivity
μS cm−1
21 200
1500
2540
1600
no data
650
1500
Na+
mg dm−3
3223.2
99.0
379.7
161.4
389.9
56.8
145.8
Cl−
5741.8
162.1
705.8
284.1
719.9
94.7
263.1
Ca2+
99.59
50.62
97.99
61.88
118.31
54.64
57.69
Mg2+
307.5
11.77
36.47
19.46
49.03
13.35
18.47
K+
89.66
9.08
11.72
7.69
14.61
5.46
6.66
HCO3−
416.25
196.14
255.6
190.85
350.16
154.86
202.34
SO42−
342.6
35.14
97.12
52.85
160.67
44.73
57.87
NO3−
3.58
0.4
6.79
3.52
7.88
3.29
3.79
NH4+
1.33
0.03
0.36
0.18
0.38
0.02
0.04
PO4−
0.80
0.20
0.21
0.53
0.03
0.14
0.19
Dry residue
947.7
944.9
no data
894.3
no data
747.2
no data
COD
mg O2 dm−3
115.70
56.20
no data
24.79
no data
36.36
no data
The first study on the benthic fauna was carried out at the time of very high water pollution and showed the presence of only Oligochaeta (family Tubificidae sensu Timm 2009) and Chironomidae between 96 km and 128 km of the Vistula course (Zięba, Zaćwilichowska 1966). Several kilometers upstream from the city of Kraków (158 km), four other taxa were recorded (Naididae, Erpobdellidae, Physidae, Ancylidae) (Table 3). In the 1980s, the number of invertebrate taxa found between 128 km to 153 km of the Vistula course increased to 15 (Table 3), but taxa characteristic of strongly polluted (Psychodidae) or temporarily deoxygenated waters (Chaoboridae) still occurred. Although the number of taxa found during our study conducted at these two localities was similar, for the first time Chironomidae were the most abundant group, while previously oligochaetes dominated. In the 1990s, the number of oligochaete species reached 20 (Table 4) in the studied river section, i.e. a similar number to that recorded by Dumnicka (2002). In the course of our current research, the number of species found at particular localities was smaller, but six species previously not recorded in the Vistula were added to the list (Table 4).
Changes in the benthic fauna composition in the Upper Vistula over 50 years (based on literature data and our study) after Zięba, Zaćwilichowska 1966; after Zięba, Zaćwilichowska 1966; after Dumnicka, Kownacki 1988 + – taxon present; +++ – the most numerous taxon;
Study period
1962–1963
1962–1963
1982–1983
2014
2014
Localities
Oświęcim–Spytkowice
Tyniec
Okleśna–Jeziorzany
Oświęcim
Czernichów
km from the sources taxa
96–128
158
128–153
96
140
Tubificidae
+++
+++
+++
+
+
Chironomidae
+
+
+
+++
+++
Naididae
+
+
+
+
Physidae
+
+
Erpobdellidae
+
+
+
Glossiphonidae
+
+
Simuliidae
+
+
Lymnaeidae
+
+
+
Gammaridae
+
+
+
Enchytraeidae
+
+
+
Ancylidae
+
+
Psychodidae
+
Chaoboridae
+
Lumbricidae
+
Coleoptera
+
Hydropsychidae
+
+
Baetidae
+
+
Bithyniidae
+
+
Acroloxidae
+
Pontogammaridae
+
Caenidae
+
Ceratopogonidae
+
Number of taxa
2
6
15
11
14
Changes in oligochaete species composition in the Upper Vistula over 50 years – after Zięba, Zaćwilichowska 1966; after Dumnicka, Kownacki 1988; after Dumnicka 2002; mouth of the Gostynka River A – alien species; B – species typical of brackish waters;
Study period
1962–1963
1982–1983
1997–1998
2014
km from the sources
96–128
158
128–153
115–165
248
337
91
96
140
283
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
Naididae gen. spp.
+
A
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
AB
+
+
+
+
A
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
A
+
+
A
+
+
+
A
+
+
+
+
+
+
AB
+
+
+
+
+
+
+
+
AB
+
Number of taxa
3
3
20
22
19
22
2
9
17
11
Despite high chloride concentrations persisting for many years (Table 1), only a few taxa characteristic of brackish or even marine waters were found in the Upper Vistula (Tables 4 and 5). Among them, the crustacean
Distribution of Amphipoda species in the Upper Vistula in different years after Zięba, Zaćwilichowska 1966 – species incorrectly identified as after Dumnicka, Kownacki 1988; + – single specimens, ++ – numerous specimens, +++ – very numerous specimens
Study period
1962–1963
1982–1983
2014
2014
2014
2014
Locality
Bachórz st.
Czernichów
Gostynka R.
Oświęcim
Czernichów
Szczucin
km from the sources
115
140
91
96
140
283
+
+
+++
++
++
++
++
+
Distribution of alien mollusk species in the Upper Vistula in different years after Zięba, Zaćwilichowska 1966; after Zięba, Zaćwilichowska 1966; after Dumnicka, Kownacki 1988; after Maćkiewicz 2013; + – single specimens, ++ – numerous specimens, +++ – very numerous specimens
Study period
1962–1963
1962–1963
1982–1983
2011
2017
Locality
Skawinka mouth
Tyniec
Czernichów
Kraków
Skawinka mouth
km from the sources
150
158
140
96
150
+++
++
+
++
++
++
A total of eight alien species were identified among the oligochaetous clitellates (Table 4), but the number of recorded species at specific sampling localities was significantly smaller – from one to a maximum of three species (Dumnicka, Kownacki 1988; Dumnicka 2002, present study). The most common was
In the 1960s–1980s, only native
Among Gastropoda,
At the same sampling locality, a rare species –
In the mid-20th century, the benthic fauna of the Upper Vistula was exposed to strong stress, especially due to high water pollution and high salinity, which substantially affected its composition, especially in the stretch downstream of the Przemsza River and the city of Kraków (Zięba, Zaćwilichowska 1966). Since then, the water quality has gradually improved, which was followed by an increase in the richness of fauna in the 1980s. The absence of caddisflies and mayflies, sensitive to salinity levels (Piscart et al. 2006), shows that chloride concentrations, still high in the Upper Vistula at that time, may be a factor limiting their presence.
During our study in 2014, families characteristic of moderately polluted (Kownacki, Soszka 2004) and slightly saline or non-saline waters (Wolf et al. 2009) occurred, such as Baetidae, Hydropsychidae and Caenidae, while taxa characteristic of strongly polluted waters were not found. In the course of our current study, the number of identified families was similar or a slightly smaller than that reported in the 1980s (Dumnicka, Kownacki 1988), probably due to the clearly smaller number of samples collected during only two field campaigns. In 2014, Chironomidae were more numerous than Oligochaeta, which confirmed the improvement of water quality (Starmach et al. 1976).
Despite the still high water salinity level, only three benthic species typical of brackish waters (
The ways of migration and the rates of dispersion of various alien species in the Upper Vistula have not been thoroughly explored and sometimes they are difficult to define. The invasion of alien amphipods is considered to be relatively fast and they continue to spread in Polish waters (Bącela et al. 2008; Grabowski et al. 2007; 2009).
The distribution of alien species belonging to the above-mentioned groups has changed over time. The gastropod
For many years, the composition of benthic fauna communities in the Upper Vistula has been affected by some stress factors such as pollution, salinity, invasion of alien species and hydrotechnical constructions. Nevertheless, the gradual improvement of water quality has led to an increase in the number of species, while the impact of alien species has only been observed with regard to the species composition of the gammarid fauna.
Rare species such as
The composition of benthic fauna as well as other communities in the Upper Vistula should be monitored, as in other big rivers (Fruget et al. 2015), in order to determine further directions and the rate of changes taking place.