Number of words in:
Abstract: 145
Main text: 3625
Number of references: 45
Number of figures: 3
Number of tables: 2
Corresponding author: Justin Pomeranz, jfpomeranz@gmail.com,
cell: 720.212.9517, Mailing address: University of South
Dakota, Department of Biology, 401 East Clark St, Vermillion, SD, USA
57069
Author contributions: JP designed the study, collected the
data, performed the modelling work, made the figures and wrote the first
draft of the manuscript, JW performed modelling work, made the figures,
and all authors contributed substantially to revisions.
Data accessibility: Upon article acceptance, all data and code
used in the present study will be archived in Data Dryad and Zenodo,
respectively.
Abstract
The distribution of abundance and biomass within ecological communities
is related to trophic transfer efficiency from prey to predators. While
it is considered to be one of the few consistent patterns in ecology,
spatiotemporal variation of this relationship across continental-scale
environmental gradients is unknown. Using a database of stream
communities collected across North America (18-68° N latitude, -4 to
25°C mean annual temperature) over 3 years, we constructed 162
mass-abundance relationships (i.e. size spectra). Size-spectra slopes
declined (became steeper) with increasing temperature. However, the
magnitude of change was relatively small, with median slopes changing
from -1.2 to -1.3 across a 29°C range in mean annual temperature. In
contrast, total community biomass increased 3-fold over the temperature
gradient. Our study suggests strong conservation of abundance
size-spectra in streams across broad natural environmental gradients.
This supports the emerging use of size-spectra deviations as indicators
of ecosystem health.