Benthic nitrogen metabolism in a macrophyte meadow (Vallisneria spiralis L.) under increasing sedimentary organic matter loads

Research output: Contribution to journalArticle


Organic enrichment may deeply affect benthic nitrogen (N) cycling in macrophyte meadows, either promoting N loss or its recycling. This depends upon the plasticity of plants and of the associated microbial communities, as those surrounding the rhizosphere. Rates of denitrification, dissolved inorganic N fluxes and N uptake were measured in sediments vegetated by the submerged macrophyte Vallisneria spiralis L. under increasing organic matter loads. The aim was to investigate how the combined N assimilation and denitrification, which subtract N via temporary retention and permanent removal, respectively, do vary along the gradient. Results showed that V. spiralis meadows act as regulators of benthic N cycling even in organic enriched sediments, with negative feedbacks for eutrophication. A moderate organic load stimulates N uptake and denitrification coupled to nitrification in the rhizosphere. This is due to a combination of weakened competition between macrophytes and N cycling bacteria and enhanced radial oxygen loss by roots. An elevated organic enrichment affects N uptake due to hostile conditions in pore water and plant stress and impairs N mineralisation and its removal via denitrification coupled to nitrification. However, the loss of plant performance is almost completely compensated by increased denitrification of water column nitrate, resulting in a shift between the relative relevance of temporary and permanent N removal processes.


  • Elisa Soana
  • Mariachiara Naldi
  • Stefano Bonaglia
  • Erica Racchetti
  • Giuseppe Castaldelli
  • Volker Bruchert
  • Pierluigi Viaroli
  • Marco Bartoli
External organisations
  • Stockholm University
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Geochemistry


  • N fluxes, Radial oxygen loss, Vallisneria spiralis, Organic enrichment, N uptake, Denitrification
Original languageEnglish
Pages (from-to)387-404
Issue number1-3
Publication statusPublished - 2015
Publication categoryResearch
Externally publishedYes