Patterns of Aquatic Macrophyte Species Composition and Distribution in Bulgarian Rivers
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Turkish Journal of Botany Turk J Bot (2013) 37: 99-110 http://journals.tubitak.gov.tr/botany/ © TÜBİTAK Research Article doi:10.3906/bot-1112-35 Patterns of aquatic macrophyte species composition and distribution in Bulgarian rivers 1, 2 3 Gana GECHEVA *, Lilyana YURUKOVA , Svetoslav CHESHMEDJIEV 1 Faculty of Biology, University of Plovdiv, Plovdiv, Bulgaria 2 Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, Sofia, Bulgaria 3 SI Eco Consult Ltd., Sofia, Bulgaria Received: 29.12.2011 Accepted: 12.08.2012 Published Online: 26.12.2012 Printed: 22.01.2013 Abstract: The composition of aquatic bryophyte and vascular plant assemblages, and 4 environmental variables (water velocity, shading, mean depth, and substrate type), together with altitude, ecological status, and river type were monitored at 223 sites along 204 rivers during 2009 in the Pontic Province and Eastern Balkan Ecoregions, Bulgaria. The relationships between macrophytes themselves and the parameters studied were tested. Forty-nine bryophytes and 86 vascular plants were identified. Canonical correspondence analysis (CCA) showed that aquatic bryophytes and vascular plants are in inverse correlation. Bryophytes occurred mainly in conditions of higher altitude and ecological status; at the same time vascular plants were found in lowland river types defined by lower status and altitude. CCA also established that flow velocity was of prime importance for bryophyte distribution, while the substrate type had no significant correlation. In contrast, most vascular plants depended considerably on substrate and prefer finer types. The data also showed that shading explained the major part of vascular species variance. This study represents an important contribution to environmental monitoring and biodiversity conservation programmes. For the first time relationships between 135 macrophyte taxa and 7 environmental variables were tested. Abiotic factors were highlighted with major influence on river bryophyte and vascular plant communities. Key words: Aquatic macrophytes, river, environmental variables, canonical correspondence analysis 1. Introduction Water Framework Directive (WFD) 2000/60/EC Aquatic macrophytes are considered photosynthetic (European Union, 2000) they are an obligatory element organisms of freshwater habitats, easily seen with the in the monitoring of ecological river quality. Macrophytes naked eye, that are normally found growing in or were included in assessment methods: French Indice on the surface of water, or where soils are flooded or Biologique Macrophytique en Riviere, German Reference saturated long enough. These plants have evolved some Index, British Mean Trophic Rank, and Dutch Macrophyte specialised adaptations to an anaerobic environment. Score (Birk et al., 2006). While high ecological status is They are represented in 7 plant divisions: Cyanobacteria, determined via dominance of reference species in type- Chlorophyta, Rhodophyta, Xanthophyta, Bryophyta, specific vegetation density, it is very important to determine Pteridophyta, and Spermatophyta (Chambers et al., 2008). whether patterns of aquatic macrophyte composition and Macrophytes may be floating, floating-leaved, submerged, distribution including cases of depopulation are a result of or emergent (Sculthorpe, 1967), and may complete their anthropogenic pressure or natural habitat variables. life cycle in water (still and flowing) or on hydric soils Local habitat characteristics determine river (inundated and noninundated). macrophyte communities, particularly light availability, Aquatic communities reflect anthropogenic influence current velocity, sediment patterns, and nutrient supply and are very useful for detecting and assessing human (Birk & Willby, 2010). Both hydrologic dynamics and impacts (Solak et al., 2012). Aquatic macrophytes as human impact expressed as land-use types are found to primary producers and habitat providers are important be responsible for the variability of aquatic macrophyte component of river ecosystems. Their compositional assemblages along the Danube corridor in Slovakia patterns are sensitive to a number of factors such as (Otahelová et al., 2007). Light condition is another water flow velocity and level, eutrophication, pollution, important factor determining macrophyte species and additional pressures. As stipulated by the European composition (Hrivnák et al., 2006). Substrate type also * Correspondence: [email protected] 99 GECHEVA et al. / Turk J Bot directly affects macrophyte development. Rocks and plants of Bulgaria (Kozhuharov, 1992). Bryophyte samples hard, immobile substrates are associated with bryophytes were stored in collecting packets, observed under the light (Janauer & Dokulil, 2006). Data indicate that coarse microscope in the laboratory, and determined according substrate and variable flow regime contributed both to to Petrov (1975) and Smith (1980, 2004). The nomenclature the success of bryophytes and the exclusion of vascular described in Grolle and Long (2000) for liverworts and in hydrophytes (Scarlett & O’Hare, 2006). Bryophytes are Hill et al. (2006) for mosses was followed. The taxonomy of a dominant component in lotic ecosystems, especially vascular plants followed Flora Europaea (Tutin et al., 1964– in undisturbed conditions, and their relations with 1980, 1993). The abundance of each species was estimated environmental factors were studied (Glime & Vitt, 1987; according to a 5-degree scale (1 = very rare, 2 = infrequent, Suren, 1996; Duncan et al., 1999; Suren & Duncan, 1999; 3 = common, 4 = frequent, 5 = abundant, predominant) Suren et al., 2000; Scarlett & O’Hare, 2006; etc.). The according to Kohler (1978). Macrophyte relative abundances combined influence of underlying geology, water physico- were quantified based on percent frequency of occurrence chemistry, current velocity, and substrate morphology at 223 sampling sites. on 17 bryophyte species was investigated in 3 minimally Four main characteristics of each site were recorded: impacted high-latitude headwater streams in Scotland speed of the water flow, substrate type, shading, and mean (Lang & Murphy, 2012). Aquatic bryophytes have also been depth. Shading was noted based on the 5-degree scale (1 studied and used to rank contaminated sites (Samecka- = completely sunny, 2 = sunny, 3 = partly overcast, 4 = Cymerman et al., 2002; Cesa et al., 2006, 2010; Vieira et half-shaded, 5 = completely shaded) of Wörlein (1992). al., 2009; etc.). The other 3 parameters were determined according to A basic study of aquatic vegetation in Bulgaria was Schaumburg et al. (2004, 2006) in a semiquantitative way accomplished 30 years ago by Kochev and Jordanov (1981). using class scales, to enable a fast and easy field application. In recent years in Bulgaria, separate studies have focused Velocity of flow was recorded via a 6-point scale: I = not on aquatic macrophyte composition itself in single rivers visible, II = barely visible, III = slowly running, IV = or river sections (Yurukova, 2002; Yurukova & Gecheva, rapidly running (current with moderate turbulences), V = 2004; Papp et al., 2006; Valchev et al., 2006; Valchev & rapidly running (turbulently running), VI = torrential. The Stoeva, 2010). Studies on aquatic plants’ relations with substratum conditions at the sampling site are classified in ecological variables are still scarce (Yurukova & Kochev, 5% steps according to an 8-point scale: % mud, % clay/ 1993, 1994; Yurukova, 2004; Janauer et al., 2006; Gecheva loam (<0.063 mm), % sand (0.063–2.0 mm), % fine/ et al., 2010, 2011). medium gravel (2.0–6.3/6.3–20 mm), % coarse gravel (20– The present study aimed to enhance our knowledge 63 mm), % stones (63–200 mm), % boulders (>200 mm), of the relationships between environmental variables and % organic/peat. Mean depth was noted on a 3-degree (water velocity, shading, mean depth, and substrate type), scale (I = 0–30 cm, II = 30–100 cm, III >100 cm). together with altitude, ecological status, and river type, and In situ measurements of acidity (pH) and electrical aquatic macrophyte species’ composition and distribution conductivity (C, µS cm-1) of river water were made using a in Bulgarian rivers. Multiline P3 (WTW, Germany). Integrated ecological status (ES) is based on assessed 2. Materials and methods biological, physico-chemical, and hydromorphological 2.1. Study objects and area quality elements of the studied rivers as required by the For the purposes of the research, we studied bryophytes Water Framework Directive (European Union, 2000). (Bryophyta) and vascular plants (Pteridophyta and Assessment results, expressed as the ‘Ecological Quality Spermatophyta) and included them in 3 groups: Ratio’ (EQR), followed Cheshmedjiev et al. (2010) and hydrophytes, amphiphytes (species capable of growing on were applied to express the overall anthropogenic impact. land or in water), and helophytes (emergent plants, rooted The EQR uses a numerical scale between 0 and 1, where 1 under water). Aquatic macrophytes were monitored in represents (type-specific) reference conditions and values the period June–September 2009 at 223 sampling sites in close to 0 indicate bad ecological status. Bulgaria (Figure 1), representative of various river types. 2.3. Data analysis 2.2. Sampling Initially, we elaborated a floristic list of higher plants and All vascular plants and bryophytes were recorded at each additional list of sites, indicating the presence/absence site with length varying between 50 and 100 m. Structural