2 research outputs found
Temporal Variability of Nitrogen Stable Isotopes in Primary Uptake Compartments in Four Streams Differing in Human Impacts
8 páginas, 3 figuras, 1 tabla.Understanding the variability of the natural
abundance in nitrogen stable isotopes (expressed as δ15N) of
primary uptake compartments (PUCs; e.g., epilithon or macrophytes)
is important due to the multiple applications of stable
isotopes in freshwater research and can give insights into
environmental and anthropogenic factors controlling N dynamics
in streams. While previous research has shown how δ15N of PUCs
varies with δ15N of dissolved inorganic N (DIN) among streams,
less is known about how δ15N of PUCs varies over time. Here, we
examined monthly variation of δ15N of PUCs and of DIN species
(nitrate and ammonium) over a year, and compared it among
streams with contrasting human impacts and PUC types. Our
results showed no evidence of isotopic seasonal patterns.
Temporal variability in δ15N-PUCs increased with human impact, being the highest in the urban stream, probably influenced
by the high variability of δ15N-DIN. Among compartments, in-stream PUCs characterized by fast turnover rates, such as
filamentous algae, showed the highest temporal variability in δ15N values (from −3.6 to 23.2 ‰). Our study elucidates some of
the environmental and biological controls of temporal variability of δ15N in streams, which should be taken into account when
using stable isotopes as an ecological tool.This
research was supported by project ISONEF, funded by the
Spanish Ministry of Science and Innovation (ref CGL2008-
05504-C02-01), and by the European Union seventh Framework
Programme REFRESH project under contract 244121.
AP and MP were supported by a Formación de Personal
Investigador PhD fellowship from the Spanish Ministry of
Science and Innovation associated to the ISONEF project.Peer reviewe