Characteristics of Cladophora and coexisting filamentous algae in relation to environmental factors in freshwater ecosystems in Poland

Samples of filamentous green algae were collected in summer of 2012, 2013, 2014 in different ecosystems, such as 3 rivers, 2 ponds, 1 lake and 1 water reservoir in the Wielkopolska Province. Sites of the filamentous algae distribution were marked on the map of the Wielkopolska Province (Fig. 1). Macroscopic filamentousalgae withthe dominance of Cladophora glomerata were sampled in Oporzyńskie Lake (52°55’N, 17°9’E) and in the lowland rivers: Nielba (52°48’N, 17°12’E; near Wągrowiec, ca. 50 km from Poznań), Samica Stęszewska (52°16’N, 16°41’E; Stęszew) and Mogilnica (52°9’N, 16°31’E; near Kamieniec), C. rivularis in a pond located in the village of Konojad (52°10’N, 16°31’E), C. fracta in the Malta reservoir (52°24’N, 16°58’E) and in a small, artificial pond (52°27’N, 16°55’E; Poznań).

The color of thalli as well as the presence or absence and the type of branching were observed during the sampling. Purified thalli were stored in plastic containers and their small portions were preserved in 4% formalin solution. Morphometric measurements to identify the species were carried out on the living and preserved material. Microscopic observations of the collected material were performed using a light microscope (Zeiss Axioskop 2 MOT), measurements of the length and width of cells from the main axes of filamentous algae were taken at ×200 and ×400 magnification. To determine the number of pyrenoids, the samples were stained with Lugol’s solution. To determine the number of nuclei, the staining method with acetocarmine was used. The results were compared with morphometric data on filamentous algae from Poland included in the identification keys by Starmach (1972), Mrozińska (1984), Kadłubowska (1972), Pliński & Hindák (2012) and papers by Zulkifly et al. (2013), Malkin et al. (2008).

During the sampling, physicochemical parameters of water were measured: temperature (°C), pH, dissolved oxygen (DO%), electrolytic conductivity (EC µS cm^-1), and the Total Dissolved Solids (TDS mg l^-1) using a YSI Professional Plus multifunctional probe. For a detailed analysis of the chemical parameters, water samples (500 ml) were collected and preserved with chloroform (CHCl₃) and stored at -10°C for further analysis. Using a spectrophotometer HACH DR 2800, the color, the water turbidity and the concentration of orthophosphates, nitrates, ammonium nitrogen and sulfates were determined. Chlorophyll a (Chl a µg g^-1) concentration was determined by a spectrophotometer using ethanol as an extraction solvent. Water samples (1.5 l) for pigment analysis were filtered onto Whatman GF/F filters according to the ISO 10260 standard method.

Figure 1

Frequency of filamentous algae (belonging to 15 genera) was estimated as the number of observations on the basis of the total number of samples from own samplings and those from the literature data – 70 sites (Czerwik-Marcinkowska 1997; Maciejczak & Czerwik-Marcinkowska 2010; Czerwik-Marcinkowska & Ziętarski 2011; Czerwik- Marcinkowska & Vončina 2012; Chudyba 1968; Krzyk 2001; Szymańska et. al. 2015; Pieczyńska & Tarmanowska 1996; Starmach 1969; Endler et al. 2011; Pieczyńska 2008; Celewicz-Gołdyn & Kuczyńska-Kippen 2008; Celewicz-Gołdyn & Klimko 2008; Kuczyńska-Kippen et al. 2004; Messyasz & Rybak 2011; Messyasz et al. 2015a; Pikosz & Messyasz 2015; Jakubas et al. 2014; Ozimek 1990; 1992; Wołowski & Kowalska 2009; Żelazna- Wieczorek 2002; Jekatierynczuk-Rudczyk et al. 2012; Szoszkiewicz et al. 2010; Staniszewski et al. 2012; Grabowska 2006; Owsianny & Gąbka 2006; Hutorowicz 2006; Lenarczyk 2012; Dondajewska & Budzyńska 2009; Piątek & Piątek 2005).

All the statistical analyses were performed using the CANOCO ver. 4.5 software (ter Braak & Šmilauer 2002). The Canonical Correspondence Analysis (CCA) to determine the relations between the species distribution and environmental variables was used. The Monte Carlo permutation test shows that chlorides, orthophosphates, total dissolved solids, nitrates and chlorophyll a were statistically significant (P<0.05).

Based on the literature data (70 sites) and our own research (7 sites), the most frequently recorded filamentous algae in freshwater ecosystems of Poland belong to 15 genera: Cladophora, Rhizoclonium, Microspora, Oedogonium, Bulbochaete, Draparnaldia, Stigeoclonium, Hydrodictyon and Ulothrix classified into the phylum Chlorophyta, Spirogyra, Mougeotia, Zygnema, Sirogonium classified into the phylum Charophyta, Vaucheria and Tribonema classified into the phylum Ochrophyta. The dominant (>10% of all genera) genus was Cladophora – about 30%, followed by Spirogyra – 16% and Oedogonium – 11% (Fig. 2).

Based on the data, the most common habitats of filamentous algae were flowing (lotic) waters such as rivers and streams (50%), and standing (lentic) waters: ponds and lakes (Fig. 3). Only Cladophora occurred in all types of ecosystems. Cladophora and Ulothrix were usually found in lotic waters. Cladophora and Spirogyra were common in ponds and lakes.

Figure 2

Cladophora glomerata (L.) Kützing (Fig. 4) was observed in rivers with comparable water velocity (0.15-1.85 m s^-1) and a water depth ranging from 0.5 to 1.5 m. Long, dark green filaments of Cladophora glomerata occurred alone in the Samica Stęszewska river. Representatives of macroscopic filamentous algae belonging to the genera: Cladophora, Rhizloclonium, Oedogonium, Stigeoclonium and Vaucheria were observed in the Mogilnica river (Table 1). There were 2 types of substrate: sand and hard substrate. Up to 2 m long filaments of C. glomerata with a small number of branching occurred on the former, and less than 20 cm long filaments with numerous branches dominated on the latter. Single filaments of Stigeoclonium nanum (Dillwyn) Kützing, Rhizoclonium sp. Kütz. and Oedogonium sp. Kütz. ex Hirn occurred and tangled together. In the Nielba river, young filaments of C. glomerata were attached to the stones and mature filaments were free-floating on the water surface between macroscopic tubular forms of Ulva thalli. Cladophora glomerata occurred also in Oporzyńskie Lake, where it formed a dense, mostly monoalgal mat. Cladophora rivularis (L.) Hoek was often observed as filaments coexisting with Oedogonium capillare in a small agriculture pond. C. rivularis exhibits a great morphological variation due to the fact that cells of a varying width occur in the same filament (Fig. 5). Moreover, taxa from the genera Tribonema, Ulothrix, Microspora, Spirogyra and Mougeotia were observed, but only in early spring and only a few filaments. Cladophora fracta (Müller ex Vahl) Kütz. is the most characteristic taxon of the studied Cladophora species; its first, delicate and slender filaments are followed by yellow green filaments, which do not reach a significant dominance in a mat. Species from Zygnemataceae (Spirogyra sp., Zygnema sp., Mougeotia sp.) often occurred as accompanying algae in the examined water ecosystems – the artificial pond in Poznań and the Malta Reservoir.

Figure 3

The water temperature in the studied ecosystems was similar – about 20°C. Concentrations of ammonium nitrogen, nitrates and phosphates in the water at the studied sites reflect high levels of fertility (Table 2). The highest content of NH₄ ⁺ was determined in the Konojad pond and in the Nielba river, N-NO₃- – in the Mogilnica and Nielba rivers, and the content of P-PO₄ ^3- above 1 mg l^-1 was recorded in the Mogilnica river. At the other sites, the amount of orthophosphate was at a similar level. The lowest value of N-NO₃- was determined in the Samica Stęszewska river (0.16 mg l^-1). Filamentous algae were observed in a wide range of electrolytic conductivity (EC) and the Total Dissolved Solids (TDS) – from 387 to 946 (µS cm^-1) and 198-538 (mg l^-1), respectively. The pH of water in all ecosystems was alkaline (9>pH≥7.5).

Figure 4

Figure 5

The relationships between 16 environmental factors and the filamentous algae distribution in water ecosystems were investigated. The Monte Carlo permutation test was used with 999 permutations to reduce the number of ecological variables and revealed that the water depth and concentration of chlorides, orthophosphates, nitrates, total dissolved solids and chlorophyll a are independent environmental gradients, significantly related to the composition of filamentous algae assemblages (p<0.05, Table 3). The content of chlorophyll a, nitrates, orthophosphates, sulfates and water pH, dissolved oxygen, color and water turbidity were also correlated with the first CCA axis, while the second CCA axis was associated with the water depth, electrolytic conductivity, total dissolved solids and concentration of chlorides and sulfates (Table 4).

The occurrence of Cladophora glomerata, which was the most common species of all filamentous algae, and the accompanying taxa (Rhizoclonium sp., Vaucheria sp. and Stigeoclonium nanun) was strongly correlated with water fertility (high values of chlorophyll a, nitrates and orthophosphate). The occurrence of C. rivularis, Oedogonium capillare and Cladophora sp. was correlated with high concentrations of chlorides and sulfates in shallow water ecosystems. At the same time, the occurrence of Cladophora fracta and Zygmenataceae was associated with inconsiderable TDS and electrolytic conductivity (Fig. 6).

Figure 6

Our study and the review of the literature data relate to Cladophora species and the accompanying filamentous algae in Poland. According to Whitton (1970), Cladophora glomerata, C. rivularis and C. fracta are the most common species of the genus Cladophora occurring in eutrophic freshwater ecosystems. Our research confirms this finding, because we found all three species within a short distance between the studied sites in the Wielkopolska Province. Most of the aquatic ecosystems in Poland are characterized by moderate or highly trophic conditions (Gołdyn et al. 2013; Messyasz et al. 2015b) and therefore, they are potential habitats of filamentous algae. Additionally, small lakes (1-5 ha) dominate in Poland and account for 44% of the total number of lakes (Choiński 1991), where filamentous algae, i.e. Oedogoniales and Zygnematales occur and may form dense mats. As reported in the literature, however, the largest numbers of the taxon Oedogonium were observed in small water bodies, such as small ponds, pools, roadside ditches, marshes, oxbow lakes, lakes, reservoirs, rivers (Mrozińska-Weeb 1976; Burchardt 1977; Sieminiak 1979; Kuczyńska-Kippen 2009; Pikosz & Messyasz 2015). The large-scale occurrence of Cladophora was previously observed in the Great Lakes of North America (Erie, Michigan, Ontario) in the 1950s and 1980s (Higgins et al. 2008). The extensive development of C. glomerata was also observed in the lake surveyed during our research (Oporzyńskie Lake) – the species densely covered the water column (Messyasz et al. 2015c). The maximum development of Cladophora glomerata in the Skawa river was determined by a few factors, such as the type of substrate, temperature (optimum growth in 15-20°C) and in pH of water (optimum 8.8) (Chudyba 1968). We also noticed that Stigeoclonium nanum occurred in small numbers in the Mogilnica river – only a few filaments entangled with Cladophora glomerata. Similar observations were made in the Jalala river in spring, where S. nanum was found attached to other algae growing in slow flowing waters (Akhtar & Rehman 2009). Species belonging to the genus Stigeoclonium show a wide range of ecological tolerance and high morphological plasticity, and may be found in different ecosystems, e.g. rivers, lakes, canals and ponds (Francke 1982). Only free-floating forms of Spirogyra species were observed during our research, which confirms the previous studies that the genus is represented mostly by free-floating (rarely attached) filamentous algae (Chalotra et al. 2013).

Our study demonstrates that representatives of filamentous algae may occur in all types of water ecosystems, such as lakes or rivers, despite the fact that these habitats are significantly different in term of their physicochemical parameters. Their occurrence is, among others, a result of a high tolerance to changes in temperature and light conditions.

Numerous floristic data confirm the occurrence of filamentous algae in lowland lakes and rivers, but the studies usually do not take the structure of species and ecological characteristics into account (South & Whittick 1987; Pieczyńska 2008). Knowledge of filamentous algae from Poland, particularly of the genera Oedogonium, Spirogyra and Cladophora (most commonly recorded), comes from a few sources. The filamentous algae are an important component of the littoral communities in aquatic ecosystems, because they are one of the main primary oxygen producers. Nonetheless, studies of the vegetation in the littoral zone generally relate to macrophytes (Cambra & Aboal 1992). In Spain, the most common filamentous algae belonged to 7 genera, including the most frequent Oedogonium, Spirogyra and Mougeotia (Cambra & Aboal 1992). In Poland, Chudyba (1968) divided Cladophora glomerata from the Skawa river into two groups based on the morphological variation. Samples collected from the fast flowing water were referred to as C. glomerata rheobenthicum and from the slow flowing water – as C. glomerata limnobenthicum. We also observed intraspecific variability between C.glomerata from the surveyed rivers and from the lake. Thalli of C. glomerata in the lentic waters were fruticose and relatively short (up to 20 cm), while in the river waters – long and characterized by a small number of branches. Significant changes at the cellular level (length, width, the number of pyrenoids and cell nuclei) were observed in the filaments of C. glomerata collected from the lowland rivers (Nielba, Mogilnica, Samica Stęszewska). These changes could result mainly from hydrodynamic (diverse water flow) and thermal differences in the surveyed habitats. Morphological plasticity is characteristic of filamentous algae, which frequently causes problems during taxonomic identification (van den Hoek 1963; Starmach 1972). Even the degree of branching in each individual plant can affect the cell size (Ross 2006). Some information on the cell structure, morphological variation and biology of Cladophora genera are provided by van den Hoek (1963) and Whitton (1970).

According to van den Hoek (1963) and Robinson & Hawkes (1986), physiological requirements of most freshwater filamentous algal species restrict their distribution to eutrophic conditions (high nutrient concentrations and alkaline conditions). In addition, Cladophora species grow well at temperatures ranging from 15 and 25°C, in hard and alkaline waters (Wong et al. 1978, Whitton 1970). A similar trend was observed in the case of other filamentous green algae, i.e. Cladophora glomerata, C. rivularis and C. fracta – relatively high values of nutrients were determined in our study when analyzing the chemical composition of their habitats. Although all these species occurred in shallow waters, the optimum for Cladophora glomerata development was in the conditions of high concentrations of nitrate and orthophosphate and Cladophora rivularis requires a high content of chlorides and sulfates. There are other macroscopic green algae species such as representatives of Ulva, which occur mostly in eutrophic waters with high concentration of NaCl of anthropogenic origin (Messyasz & Rybak 2011; Messyasz et al. 2015a).

On the other hand, small values of TDS and electrolytic conductivity characteristic of slightly eutrophic waters (e.g. the pond in Poznań) were clearly favored by Cladophora fracta. Moreover, the accompanying Zygnemataceae taxa occur mainly in waters rich in dissolved oxygen and often form a filamentous mass overgrowing aquatic plants (Worobiec & Worobiec 2008). From environmental factors, both nitrogen depletion and light intensity have been regarded as key factors inducing the conjugation of Spirogyra (Zwirn et al. 2013). Additionally, the low level of nutrients determines the development and growth of Spirogyra filaments, rather than water temperature (Wongsawad & Peerapornpisal 2015). The obtained data show that individual species of filamentous algae occurred in specific environmental conditions.