Ecological research using stable
isotopes has progressed rapidly during the last
20 years and although more studies are including
the addition of isotopically labelled compounds
at tracer levels, the overwhelming majority rely
on measurements of natural abundance ratios.
Access to isotope ratio mass spectrometry has
increased, spurred on by awareness of the techniques
and increasing demand, and consequently
cost of sample analysis has dropped. Today stable
isotopes of carbon (13C/12C), nitrogen (15N/14N),
sulphur (34S/32S), oxygen (18O/16O), and hydrogen
(2H/1H) can be determined routinely. Perhaps one
of the most appealing attributes of isotopic signatures
is their potential use to find patterns and
determine mechanisms across a range of scales
from the molecular level through to characterising
whole food webs, reconstructing palaeoenvironments,
tracing nutrient fluxes between ecosystems
and identifying subsidies, or migrations
of organisms.
Ecologists from every discipline who are unlikely
to have been trained as isotope chemists
have added stable isotope analysis (SIA) to their
“toolbox”, but often increasing use leads to increasing
abuse. The usefulness of SIA arises from
predictable physical and enzymatic-based discrimination
between biological and non-biological
materials leading to different isotopic compositions.
Without some ecological understanding
of these, interpretation of isotope-derived data
can often be flawed. Here, I explore how SIA recently
has been used for research in aquatic ecology,
reviewing how some of these techniques have
allowed elucidation of key processes in aquatic
systems such as the contribution of allochthony
to lake food webs, and discuss the “state of the
art”. Included are some thoughts on where our
knowledge in aquatic ecology remains deficient
and how continued development and future application
of SIA and interdisciplinary methodologies
may be applied.