Effects of water nutrient concentrations on stream macroinvertebrate community stoichiometry: a large-scale study
Résumé
Basal resources generally mirror environmental nutrient concentrations in the elemental
composition of their tissue, meaning that nutrient alterations can directly reach consumer
level. An increased nutrient content (e.g. phosphorus) in primary and detrital resources under
nutrient enriched conditions should favour taxa with a high demand for this nutrient.
With the nutrient demand of a taxon being correlated to the elemental composition of
its body tissue (e.g. phosphorus content), such above described species shifts likely alter
the overall community stoichiometry. However, studies addressing stoichiometry at community
level are rare and most often restricted to lacustrine planktonic systems, single
streams or limited experimental setups. Relying on a stoichiometric database for >200
taxa and >1300 standardized sampling events of macroinvertebrate assemblages from
the French national monitoring programme, we investigated the effect of water phosphorus
and nitrogen load on stream macroinvertebrate community stoichiometry. Community
stoichiometry was significantly affected by water phosphorus concentration and the effect
was strongest at low levels of nitrogen.While we could not confirm our hypothesis of
increasing community %P (and decreasing C:P, N:P) with increasing water phosphorus concentrations
for the overall community, it clearly followed this pattern for both Insecta and
Malacostraca. General differences in the elemental composition among major taxonomic
groups and a shift among these groups over the nutrient gradient probably explain the
response of community stoichiometry. Our results show that assumptions from Ecological
Stoichiometry Theory also hold at the community level, at least for two dominant taxa,
and on a large spatial scale, with likely consequences for nutrient cycling and ecosystem
function.
Domaines
Sciences de l'environnementOrigine | Fichiers éditeurs autorisés sur une archive ouverte |
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