24.3.2014: Forschung CH

Eutrophierung: Effekt für Kleinstgewässer im Flachland nicht immer negativ

Eutrophisation: effet pas toujours négatif pour les étangs et petits lacs de plaine


Véronique Rosset et al.

In grossen Seen hat die Überdüngung einen starken negativen Einfluss auf die Biodiversität. In kleineren stehenden Gewässern (z.B. Weiher) ist dieser Einfluss weniger ausgeprägt. Auf lokaler Ebene eines Teiches führt die Eutrophierung nicht unbedingt zu einer Verschlechterung und ihr Einfluss variert je nach Organismus. Auch nährstoffreiche Weiher tragen zur Biodiversität auf regionaler Ebene bei. Für die Biodiversität ist ein Mosaik aus unterschiedlich nährstoffreichen Kleinstgewässern optimal. Der Stickstoffeintrag führt jedoch weiterhin zu einer Erhöhung des Eutrophierungsgrad und so zu einer Abnahme der regionalen Biodiversität.

L’eutrophisation des grands lacs à des effets très négatifs sur la biodiversité. Cet effet est moins marqué pour les petites surfaces d’eau stagnante (p. ex. étangs). A l'échelle locale d'un étang, l'eutrophisation n'est pas nécessairement une dégradation majeure et son impact varie selon les organismes considérés. A l’échelle régionale, même les étangs riches en teneur nutritive peuvent contribuer à la biodiversité. Une mosaïque d'étangs avec des teneurs variées en éléments nutritifs est optimale pour la biodiversité. Cependant, l'eutrophisation reste une pression importante entraînant une augmentation des niveaux trophiques et ainsi une perte de biodiversité régionale.


Eutrophication remains a major stress for freshwater biodiversity. Its deleterious consequences on biodiversity are well documented for large waterbodies. However, the impact of eutrophication may differ in smaller waterbodies, such as ponds and small lakes, which generally support naturally high levels of nutrients in lowlands. Furthermore, this response could depend on the scale considered, from local (individual waterbody, alpha diversity) to regional (the network of waterbodies, gamma diversity). It is also unclear whether the richness of threatened species responds in the same way as the richness of the whole assemblage.
The present study investigates local‐ and regional‐scale consequences of eutrophication on taxonomic richness (all taxa) and conservation value (threatened taxa) in temperate lowland small waterbodies. Five taxonomic groups were investigated: macrophytes, gastropods, water beetles, adult dragonflies and amphibians, in a set of natural waterbodies and a set of enriched waterbodies covering a large nutrient gradient from mesotrophic to hypertrophic conditions.
Globally, our study did not reveal consistent, systematic responses to eutrophication. For macrophytes, the richness and conservation value suffered from eutrophication at both local and regional scales. In contrast, for amphibians and gastropods, eutrophication did not impair biodiversity at the local nor the regional scale. Dragonflies and water beetles showed intermediate situations, with an impairment by eutrophication varying according to the type of waterbodies considered. At the regional scale, each trophic status, even the nutrient richest, brought an original contribution to biodiversity.
Synthesis and applications. The management of eutrophication for small lowland waterbodies has to be considered differently than for lakes. For an individual waterbody (the local scale), nutrient enrichment is not necessarily a major impairment and its impact depends on the taxonomic group considered. Conversely, at the landscape scale, eutrophication is a major pressure on small waterbody biodiversity, especially because nutrient‐rich small waterbodies are dominant in the landscape. Therefore, conservation efforts should integrate the notion of pond regional networks or ‘pondscapes’, where the regional biodiversity is supported by a mosaic of trophic conditions, and promote the presence of less rich waterbodies.

Source: Rosset V. et al. 2014. Is eutrophication really a major impairment for small waterbody biodiversity? Journal of Applied Ecology, DOI: 10.1111/1365-2664.12201

Keywords:
eutrophisation, petits plans d'eau, diversité des espèces, espèces menacées

Art der Publikation:
Fachpublikation

Literatur:
Rosset V. et al. (2014) : Is eutrophication really a major impairment for small waterbody biodiversity? Journal of Applied Ecology, DOI: 10.1111/1365-2664.12201
http://onlinelibrary.wiley.com/doi/10.1111/1365-2664.12201/abstract

Kontaktadresse:
Véronique Rosset
Irstea
5, rue de la Doua
CS70077
F-69626 VILLEURBANNE Cedex

veronique@rosset.org
Tel: +33 (0)472201085


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