The importance of sedimenting organic matter, relative to oxygen and temperature, in structuring lake profundal macroinvertebrate assemblages

摘要

We quantified the role of a main foodudresource, sedimenting organic matter (SOM), relativeudto oxygen (DO) and temperature (TEMP) in structuringudprofundal macroinvertebrate assemblages inudboreal lakes. SOM from 26 basins of 11 Finnish lakesudwas analysed for quantity (sedimentation rates),udquality (C:N:P stoichiometry) and origin (carbonudstable isotopes, d13C). Hypolimnetic oxygen andudtemperature were measured from each site duringudsummer stratification. Partial canonical correspondenceudanalysis (CCA) and partial regression analysesudwere used to quantify contributions of SOM, DO andudTEMP to community composition and three macroinvertebrateudmetrics. The results suggested a majorudcontribution of SOM in regulating the communityudcomposition and total biomass. Oxygen best explainedudthe Shannon diversity, whereas TEMP had largestudcontribution to the variation of Benthic Quality Index.udCommunity composition was most strongly related to d13C of SOM. Based on additional d13C and stoichiometricudanalyses of chironomid taxa, marked differencesudwere apparent in their utilization of SOM andudbody stoichiometry; taxa characteristic of oligotrophicudconditions exhibited higher C:N ratios and lower C:Pudand N:P ratios compared to the species typical ofudeutrophic lakes. The results highlight the role of SOMudin regulating benthic communities and the distributionsudof individual species, particularly in oligotrophicudsystems.