Lake size and fish diversity
determine trophic niche of
Arctic charr in subarctic lakes
Antti Eloranta
Norwegian Institute for Nature Research
Coauthors: Kimmo K. Kahilainen, Per-Arne Amundsen,
Rune Knudsen, Chris Harrod & Roger I. Jones
What affects
energy flow to
top consumers
in subarctic
lakes?
Importance of
littoral benthic
production?
Eloranta = Littoral zone
How lake abiotic and biotic characteristics
affect charr trophic niche?
5‐15 %
5‐15 %
H1: Charr shift to a more pelagic diet
with increasing lake size
H2: Charr shift to a higher trophic position
with increasing fish diversity
δ13C = Predominant energy flow pathway
δ15N = Food chain length
Study area
Tromsø
Area: 0.5‒1084 km2
Pulmankijärvi
Other explanatory variables:
NORWAYShoreline development
Altitude: 12‒679 m a.s.l.
Fish
species: n = 2‒13
Josefvatn
Gæsjavri
Sagelvvatn
Fjellfrøsvatn
Saanajärvi
Secchi and relative depth
Biggijavri
Total phosphorus and nitrogen
V. Spielgajavri
Muddusjärvi
Datkujavri
Kilpisjärvi
L. Rostavatn
Takvatn
Tuulisjärvi
Inarijärvi
Rahajärvi
SWEDEN
FINLAND
Ukonjärvi
Littoral reliance decreases
with lake area
Littoral reliance
1.0
0.8
0.6
0.4
0.2
0.0
-5
-3
-1
1
3
5
ln Lake area (km2)
Karlsson & Byström (2005) Limnol. Oceanogr. 50: 538-543.
7
ln Trophic position
Trophic position increases
with fish richness
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1.0
0.0
0.5
1.0
1.5
2.0
ln Fish richness
2.5
Stomachs support isotopes
Impacts on function and structure
of subarctic lake food webs
Size and
growth
OK, but
so what?
Parasites
Ecosystem
stability
Heavy
metals
Carbon &
nutrient
cycling
Reproduction
Species
composition
For more details…
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See: http://www.cedren.no/Projects/HydroBalance