Macrophyte diversity and composition in relation to substratum characteristics in regulated and unregulated Danish streams

Abstract

1. The objective of the present study was to examine how the physical stream environment in regulated and unregulated lowland streams affects the diversity and distribution of macrophyte communities. We analysed the abundance, distribution and composition of macrophytes, together with physical parameters, in seven regulated and seven unregulated unshaded Danish stream reaches. 2. Total macrophyte coverage was similar in the regulated and unregulated streams, but species richness and Shannon diversity were higher in the unregulated streams. Overall, we found fifty‐two different species in the regulated stream reaches and sixty‐two in the unregulated stream reaches. The spatial distribution of macrophytes on the stream bottom was more heterogeneous in the unregulated streams. 3. We found positive correlations between the coverage and diversity of macrophytes and the coverage of coarse‐textured substratum types on the stream bottom, as well as between macrophyte coverage and diversity and substratum heterogeneity. We also found that the macrophytes were more heterogeneously distributed where substratum heterogeneity was greater. 4. The species growing both submerged and emergent were more abundant in the regulated streams, whereas species growing only submerged were more abundant in the unregulated streams. Species growing submerged, species growing both submerged and emergent, and species only growing emergent segregated differently in a canonical correspondence analysis ordination. The submerged species were primarily associated with coarser‐textured substrata, whereas species growing both submerged and emergent, and species growing only emergent were associated with finer‐textured substrata. 5. The most abundant species in the regulated streams, Sparganium emersum, accounting for almost one‐third of the total macrophyte coverage, was primarily associated with clay and sandy bottom substrata, whereas the most abundant species in the unregulated streams, Batrachium peltatum, was primarily associated with gravel and stony substrata.

Environmental effects on species richness of macrophytes in Slovak streams

“…It is likely that, sufficient amount of light and appropriate hydrological conditions for macrophytes are partially responsible for a positive correlation between species richness of macrophytes and portion of artificial banks. The other ecological variables such as the distance from stream source, ammonium content in water, depth of water, water conductivity, flexuosity, portion of natural land cover in stream contact zone and flow velocity class were shown to influence both species composition and richness of macrophytes in streams by earlier studies [5,8,15,27], demonstrating a comprehensive effect of several ecological variables on species richness of macrophytes in streams.…”

“…Several studies have paid attention to macrophyte changes over time [12,13] or to seasonal dynamics in relation to environmental influences [14]. On the other hand, studies focusing on the relationship between species richness and environmental conditions in streams are relatively rare [15]. The lack of information about species richnesshabitat relationship in streams was the incentive for the study of this relationship in Slovak streams.…”

Vplivi obremenitev na združbe makrofitov in njihov pomen pri upravljanju z rečnimi ekosistemi / Impacts of stressors on macrophyte communities and their importance in river ecosystem management

“…Pogoste motnje zaradi upravljavskih aktivnosti bodo vzdrževale združbo na nižjih sukcesijskih ravneh in zmanjšale možnost, da bo sestava makrofitske združbe posledica medvrstnih odnosov (Sand-Jensen in sod. 1989, Baattrup-Pedersen & Riis 1999.…”

“…regulacij ali odvzemov vode velik vpliv na makrofite (Petts 1984). Pokritost z makrofiti v reguliranih in nereguliranih vodotokih je lahko podobna, a je raznolikost vrst in njihova številčnost večja ter razporejenost makrofitov po dnu struge bolj heterogena v nereguliranih vodotokih (Baattrup-Pedersen & Riis 1999). Makrofiti tudi sami vplivajo na hitrost toka in povzročajo bistveno drugačne razmere v primerjavi z neporaslimi odseki (Stephan & Wychera 2000, Green 2005 …”

“…Spremembe pretočnega režima zaradi gradnje hidroelektrarn lahko povzročajo izpiranje substrata ob povečanju pretoka oziroma nalaganje substrata ob njegovem zmanjšanju. Ker različne vrste makrofitov uspevajo na različnih substratih, tovrstne antropogene spremembe v kakovosti in količini substrata povzročajo premike v vrstni sestavi makrofitov in posledično tudi višjih trofičnih nivojev (Lacoul & Freedman 2006). 6 VPLIVI ODSTRANJEVANJA MAKROFITOV -KOŠNJE V več raziskavah so ugotavljali vpliv košnje makrofitov na vrstno sestavo združb (Baattrup- Pedersen & Riis 1999, baattrup-Pedersen in sod. 2003, 2004, Pedersen in sod.…”