High mountain water bodies are ecosystems that are highly sensitive to global change, due to their remoteness and distance to human activities. The Pyrenean limnological district holds hundreds of water bodies, with a substantial amount harboring shallow aquatic macrophytic assemblages. Previous studies indicated that Pyrenean aquatic macrophytic flora maintained their biodiversity and richness throughout the 20th century, even though acidification and regional eutrophication were severely threatening these assemblages from Center and Northern Europe. Nevertheless, signs of eutrophication and biodiversity decline have become apparent in recent times. Here we conduct a regional assessment of macrophyte flora inventories of 30 Pyrenean shallow water bodies and compare submersed vegetation inventories across a 30+ year period to directly assess vegetation shifts and possible changes in water column environmental parameters related to regional and/or local eutrophication. We use semi-quantitative data for a total of 33 taxa and a set of environmental data, starting before 1990 and revisiting after 2018, with the aim to analyze trends in aquatic plant abundance and depth distribution, water body richness and biodiversity changes occurring over more than three decades. Preliminary results indicate that most of the taxa studied remain stable, without significant changes. However, Potamogeton berchtoldii and Myriophyllum alterniflorum are expanding by the colonization of new lakes, while Isoetes creussensis and I. echinospora tend to slightly expand within systems. On the contrary, Sphagnum spp. and Subularia aquatica seem to be less frequent. We have not been able to find significant trends between the observed changes and the environmental factors considered.

Primary Presenter: Esperança Gacia, CSIC (espimartijin@hotmail.com)

Authors:

Esperança Gacia, CEAB-CSIC  (gacia@ceab.csic.es)

Eric Baqué, University of Barcelona  (ebaquedi54@alumnes.ub.edu)

Joan Lluis Riera, University of Barcelona  (jlriera@ub.edu)

Lluis Camarero, CEAB-CSIC  (camarero@ceab.csic.es)

Enric Ballesteros, CEAB-CSIC  (kike@ceab.csic.es)