This study investigated the speciation, uptake, and toxicity of uranium in Atlantic salmon (Salmo salar). 800 juvenile salmon were exposed to varying concentrations of depleted uranium over 96 hours. Uranium was found to be predominantly present as low molecular mass species less than 10 kDa. Uranium accumulated in the fish gills in a concentration-dependent manner, influenced by water pH and uranium species. Higher uranium levels in gills were correlated with increased uranium in the liver, causing ion regulation issues and stress as reflected by reduced blood plasma chloride and increased blood glucose. Mortality increased above 0.34 micromoles of uranium per gram of gill dry weight. The LC50 value ranged from

1. www.star-radioecology.org
Supported by the European Commission, contract number: Fission-2010-3.5.1-269672,
and the Research Council of Norway, contract numbers: 209101 and 209102.
www.radioecology-exchange.org
Uranium speciation, uptake and toxicty in
Atlantic salmon (Salmo salar)
Hans-Christian Teien1, Turid Hertel-Aas1, Håvard Thørring2, Lindis Skipperud1,
Louise Kiel Jensen2, Brice N. Sone1, Deborah H. Oughton1, Brit Salbu1
1Centre for Environmental Radioactivity (CERAD), Norwegian University of Life Sciences. P.O. Box 5003, 1432
Ås, Norway. 2Norwegian Radiation Protection Authority (NRPA), P.O. Box 55, N-1332 Østerås, Norway.
Introduction
To obtain information of bioavailability and toxicity of uranium (U) towards fish,
and the influence of competing cations, U toxicity experiments were conducted
with Atlantic Salmon (Salmo salar L.) juvenile parr.
Method: 800 fish were exposed (96h) to depleted uranium (DU) at 5-7
nominal concentrations in range 2 to 100µM for acute toxicity tests (OECD,
1992). Speciation (size fractionation), tissue accumulation (gill, liver) and
induced toxicity of U as a function of varying water concentrations of H+, Ca2+,
Mg2+, Na+ and K+ as well as U were studied. The effects end points were
mortality, blood plasma ions and blood glucose, and gene expression.
Pictures 1: Each exposure unit
(100 L of very soft EPA water,
8.9±0.4 0C ) contain 7 fish
(13.6±5.5 g).
Pictures 2: Collection of
different fish tissues such
as gills, liver and kidney
according to protocol
(Rosseland et al. 2001)
Figure 1. Relationship between A) U in unfiltered water and size fractions
(membrane and ultrafiltration) B) U in unfiltered water and accumulation in
gills, C) U-gill concentration and mortality, D) U-gill concentration and blood
plasma Cl, E) U-gill concentration and blood glucose, F) U-gill and U-liver
Results:
• U was predominantly present as low
molecular mass species, <10 kDa
• U accumulated in fish gills, increasing
with U concentration in the water, was
highly dependent upon pH and U species.
• U-gill concentration correlated with U-liver
level, inducing ion regulation problems
and stress response > 0.21 µmol U/g dw
gill (reflected by reduced plasma Cl
concentration and increased blood
glucose) and mortality >0,34 µmol U/g dw
gill.
• LC50 value increased exponentially from
4.2 to 108 µM from pH 5.2 to 7.8,
respectively.
• Thus, U toxicity is highly dependent upon
pH and U speciation. U species
accumulated in gills is transferred with
blood to the liver, and subsequently
severe biological effects can be induced.
0
5
10
15
20
0 1 2 3
U-Liver(nmol/gdw)
U-Gill (µmol/g dw)
F)
0
20
40
60
80
0 20 40 60 80
U-waterfractions(µmol/L)
U-water (µmol/L)
A) <0.45µm <10kDa <3kDa
0
1
2
3
4
0 40 80 120
U-gill(µmol/gdw)
U-water (µmol/L)
B) pH 5.5-6.0 pH 6.8 pH 7.3 pH 7.8
0
20
40
60
80
100
0 1 2 3
Mortality(%)
U-Gill (µmol/g dw)
C)
70
90
110
130
150
0 1 2 3
BloodplasmaCl(mM)
U-Gill (µmol/g dw)
D)
0
10
20
30
40
0 1 2 3
Bloodglucose(mM)
U-Gill (µmol/g dw)
E)
References:
OECD 1992. Test no. 210. Fish, Early Life Stage Toxicity Test. Guideline for
the testing of chemicals.
Rosseland, B.O., et al., 2001. EMERGE Fish Sampling Manual for Live Fish.
< http://www.mountain-lakes.org/emerge/methods/29.pdf>
Supported by the European Commission, Contract number: Fission-2010-3.5.1-269672,
and the Research Council of Norway, Contract number: 209101, 209102 and 223268/F50.