TY  - JOUR
A1  - Mehner, Thomas
A1  - Lischke, Betty
A1  - Scharnweber, Inga Kristin
A1  - Attermeyer, Katrin
A1  - Brothers, Soren
A1  - Gaedke, Ursula
A1  - Hilt, Sabine
A1  - Brucet, Sandra
T1  - Empirical correspondence between trophic transfer efficiency in freshwater food webs and the slope of their size spectra
T2  - Ecology : a publication of the Ecological Society of America
N2  - The density of organisms declines with size, because larger organisms need more energy than smaller ones and energetic losses occur when larger organisms feed on smaller ones. A potential expression of density-size distributions are Normalized Biomass Size Spectra (NBSS), which plot the logarithm of biomass independent of taxonomy within bins of logarithmic organismal size, divided by the bin width. Theoretically, the NBSS slope of multi-trophic communities is exactly - 1.0 if the trophic transfer efficiency (TTE, ratio of production rates between adjacent trophic levels) is 10% and the predator-prey mass ratio (PPMR) is fixed at 10(4). Here we provide evidence from four multi-trophic lake food webs that empirically estimated TTEs correspond to empirically estimated slopes of the respective community NBSS. Each of the NBSS considered pelagic and benthic organisms spanning size ranges from bacteria to fish, all sampled over three seasons in 1 yr. The four NBSS slopes were significantly steeper than -1.0 (range -1.14 to -1.19, with 95% CIs excluding -1). The corresponding average TTEs were substantially lower than 10% in each of the four food webs (range 1.0% to 3.6%, mean 1.85%). The overall slope merging all biomass-size data pairs from the four systems (-1.17) was almost identical to the slope predicted from the arithmetic mean TTE of the four food webs (-1.18) assuming a constant PPMR of 10(4). Accordingly, our empirical data confirm the theoretically predicted quantitative relationship between TTE and the slope of the biomass-size distribution. Furthermore, we show that benthic and pelagic organisms can be merged into a community NBSS, but future studies have yet to explore potential differences in habitat-specific TTEs and PPMRs. We suggest that community NBSS may provide valuable information on the structure of food webs and their energetic pathways, and can result in improved accuracy of TTE-estimates.
KW  - energetic equivalence rule
KW  - metabolic theory of ecology
KW  - multi-trophic communities
KW  - normalized biomass size spectra
KW  - pelagic and benthic lake habitats
KW  - size of organisms
Y1  - 2018
UR  - https://publishup.uni-potsdam.de/frontdoor/index/index/docId/52851
SN  - 0012-9658
SN  - 1939-9170
VL  - 99
IS  - 6
SP  - 1463
EP  - 1472
PB  - Wiley
CY  - Hoboken
ER  -