|Title||Experimental N and P additions alter stream macroinvertebrate community composition via taxon-level responses to shifts in detrital resource stoichiometry|
|Archive||All Files / Documents / Publications / Journal Articles|
1. Increases in nitrogen (N) and phosphorus (P) availability are changing animal communities,
partly by altering stoichiometric imbalances between consumers and
their food. Testing relationships between resource stoichiometry and consumer
assemblage structure requires ecosystem-level manipulations that have been
lacking to date.
2. We analysed patterns of macroinvertebrate community composition in five detritus-
based headwater streams subject to experimental whole-stream N and P additions
that spanned a steep gradient in dissolved N:P ratio (2:1, 8:1, 16:1, 32:1,
128:1) over 2 years, following a 1-year pre-treatment period.
3. We predicted that shifts in leaf litter stoichiometry would drive overall patterns of
community composition via greater responses of shredders to enrichment than
other taxa, as shredders dominate primary consumer biomass and experience
larger consumer–resource elemental imbalances than other functional groups in
stream ecosystems. Specifically, we expected litter C:P to be a significant predictor
of shredder biomass given the greater relative imbalances between shredder
and litter C:P than C:N. Finally, we tested whether shredder responses to enrichment
were related to other taxon-level traits, including body size and stoichiometry,
larval life span and growth rate.
4. Whole-community composition shifted similarly across the five streams after enrichment,
largely driven by increased shredder and predator biomass. These shifts
were limited to the autumn/winter seasons and related to decreased leaf litter C:P,
highlighting important links between the quality of seasonal litter subsidies and
5. Among 10 taxa that drove structural shifts, two declined while other taxa from
the same functional/taxonomic groups responded positively, suggesting that specific
life-history traits may determine sensitivity to enrichment.
6. Increases in total shredder biomass, and in biomass of several common shredders,
were associated with lower litter C:P. Body C:P did not predict shredder response
to enrichment. However, weak negative relationships between shredder response
and body size, and larval life span, suggest that small-bodied and short-lived taxa
may be more responsive to shifting resource stoichiometry.
|Contributors||Lee M. Demi, Jonathan P. Benstead, Amy D. Rosemond and John C. Maerz|
Demi, LM, Benstead, JP, Rosemond, AD, Maerz, JC. Experimental N and P additions alter stream macroinvertebrate community composition via taxon-level responses to shifts in detrital resource stoichiometry. Funct Ecol. 2019; 00: 1– 13. https://doi.org/10.1111/1365-2435.13289
|Key Words||community structure, detritus, ecological stoichiometry, nitrogen, phosphorus, stream|
view/download PDF file