Data from: Resource supply and organismal dominance are associated with high secondary production in temperate agricultural streams

Agricultural land use affects the environmental and biological
characteristics of stream ecosystems through multiple pathways including
nutrient and pesticide contamination, riparian clear-cutting, and
hydromorphological degradation. These changes in the abiotic environment
can have a direct effect on the productivity of macroinvertebrate
communities through environmental filtering and via altered resource
conditions encompassing a shift from allochthonous to autochthonous
primary production and changes in elemental stoichiometry and food
quality. Additionally, macroinvertebrate productivity can be affected
indirectly via biological mechanisms, such as changes in species
interactions, richness, competition, and predation. We studied the effects
of agriculture on structural and functional descriptors of
macroinvertebrate communities by assessing environmental characteristics
and macroinvertebrate secondary production (MSP), biomass, and density in
two forested and two agricultural streams and investigated underlying
biotic mechanisms. On average, MSP was 1.6–3.6, biomass 2.8–6.2, and
density 5–13 times higher in agricultural than in forested streams. This
pattern was associated with higher nutrient concentrations, standing crops
of riparian herbaceous vegetation, suspended particulate organic carbon,
quantity and quality of epilithic biofilms, and chlorophyll-a
concentrations in seston and biofilm of the agricultural streams. Species
richness and evenness were significantly lower in agricultural than in
forested streams. A negative relationship between MSP and species richness
and evenness indicated that density compensation and trait dominance were
the prevalent mechanisms facilitating higher MSP in agricultural streams.
Our findings suggest that the loss of riparian canopy and excess nutrient
conditions are the major environmental drivers contributing to
homogenization of ecological niches and dominance of highly productive
non-insect generalist species. This study highlights the importance of an
ecosystem approach to understanding how complex aggregate stressors affect
the regulation of consumer-resource interactions. There is an urgent need
to preserve or restore natural riparian vegetation, fostering habitat and
resource diversity and limiting nutrient contamination to stream
ecosystems.