Sensitivity of Early Life-Stages of White Sturgeon (Acipenser transmontanus) to Selected Metals
David Vardy1, Johanna Oellers2, Amber Tompsett1, John Doering1, Marcie Allen1, Karsten Liber1, John P. Giesy1,3, Markus Hecker1,4
1Dept,
Veterinary Biomedical Sciences & Toxicology Centre, University of Saskatchewan, Saskatoon, SK, Canada.
2RWTH University, Aachen, Germany.
3City University of Hong Kong, Hong Kong, China.
4ENTRIX Inc., Saskatoon, SK, Canada.
Abstract
Results/Discussion
White sturgeon (Acipenser transmontanus) have been experiencing poor recruitment in a number of rivers
located within the Pacific Northwest (e.g. Columbia and Kootenai Rivers) for over three decades. There are
many possible causes for this phenomenon, including pollution (e.g. metals), habitat alterations and
predation by introduced species. In general, little is known about the potential toxicity of metals such as
Copper (Cu), Cadmium (Cd), Zinc (Zn) and Lead (Pb) to white sturgeon. However, preliminary studies have
indicated that white sturgeon might be amongst the more sensitive fish species. The purpose of this study
was to establish threshold tolerances for early life-stages of white sturgeon to selected metals, Cu, Cd, Zn
and Pb, in static renewal, 96 hr lethality tests. In addition, two test species that are commonly used in
bioassays, the rainbow trout (Oncorhynchus mykiss) and fathead minnow (Pimephales promelas), were
tested in parallel for sensitivity to Cu and Pb during the yolk-sac life-stage. Rainbow trout was also tested in
parallel to white sturgeon during the juvenile life-stage. The results suggest that white sturgeon are relatively
sensitive to Cu, Cd, Zn and Pb compared to other aquatic species. In this study in particular, white sturgeon
appear to be the most sensitive of the three species tested to Cu and Pb during the yolk-sac life-stage, but
more tolerant to Pb at a juvenile life-stage compared to rainbow trout. These acute toxicity tests may help to
develop species-specific toxicity reference values that can be used in risk assessments.
• Concentrations of Cu, Cd, Zn and Pb at which 50% mortality (LC50s) occurred were compared to the hardnessadjusted quality criteria (HAQC) (Table 1). Experiments were conducted in the lab as well as in situ on the Upper
Columbia River, Canada, in the summer of 2008 and 2009.
Introduction
Sturgeon populations (Acipenseridae) are threatened throughout the world and have been in drastic decline
over the past century in Northern Europe, Asia and North America. In part this is due to over-harvesting,
habitat alteration and possibly contamination.
In North America, the white sturgeon (Acipenser
transmontanus), the largest of its species, has been listed as endangered in parts of the United States and
Canada as a result of reduced population abundances. Unfortunately, many white sturgeon populations
present in the Columbia, Fraser, and Sacramento-San Joaquin river systems frequently experience annual
recruitment failures. Many possible hypotheses for these recruitment failures have been suggested. These
include: habitat alteration, varying flow regime, decreased water quality (e.g. temperature, turbidity, total
dissolved gases, etc.), poor nutrition, genetic bottlenecks or inbreeding depression, predation by introduced
species such as walleye, inter-specific competition, pathogens, disease, and pollution. In particular, little is
known about the potential toxicity of metals, such as Copper (Cu), Cadmium (Cd), Zinc (Zn) and Lead (Pb), to
white sturgeon, or the sensitivity of white sturgeon in comparison to other fish species. Species-specific
dose-response relationships are needed to establish metal toxicity threshold values for white sturgeon.
Methods
• During the yolk-sac life-stage (~8 dph), white sturgeon are most sensitive to Cu and Pb, followed by rainbow trout
and fathead minnow (Fig 2). During the juvenile life-stage (~40 dph), white sturgeon are more sensitive to Cu yet
more tolerant to Pb compared to rainbow trout. During the later juvenile life-stage (~100 dph) white sturgeon are
most tolerant of Cu.
• White sturgeon, rainbow trout and fathead minnow are more sensitive to Cu than to Pb. Adverse effects of Cu have
been observed mainly during the first 48h of the experiment, those of Pb during the last 24h.
Table 1. LC50s for Cu, Cd, Zn and Pb for white sturgeon (A. transmontanus), rainbow
trout (O. mykiss) and fathead minnow (P. promelas) at various life-stages (dph)
compared to the HAQC. All values normalized to a hardness of 50 µg/L.
Year
White sturgeon
2008
2009
2009
2009
Rainbow trout
2009
2009
Fathead minnow
2009
Life-stage
Copper
Lab
In situ
30
22
15
27
8
18
44
8 dph
8 dph
40 dph
100 dph
8 dph
40 dph
96-h LC50 (µg/L)
Cadmium
Zinc
Lab
In situ Lab
In situ
10
40
100
459
108
407
35
18
8 dph
Lab
Lead
In situ
> 403*
1744
87
HAQC (µg/L)
7
* No adverse effect seen at this concentration
1
65
SSD Freshwater Aquatic Life - Cadmium
100%
90%
90%
80%
80%
HAQC
70%
60%
O. mykiss
60%
50%
P. promelas (UofS)
40%
P. promelas
30%
A. transmontanuus (UofS)
Percentile
O. mykiss (UofS)
1
10
40%
S.platorynchus
20%
A. brevirostrum
10%
100
A. transmontanus (UofS)
O. mykiss
Fathead minnow
1000
0%
10000
0.1
1
100%
90%
90%
80%
80%
HAQC
Percentile
Percentile
70%
60%
50%
40%
HAQC
60%
50%
40%
A. transmontanus (UofS)
30%
A. transmontanus (UofS)
O. mykiss
O. mykiss
20%
Fathead minnow
10%
Fathead minnow
0%
O. mykiss (UofS)
0%
100
1000
10000
100000
10
1/2 x SMAV Zinc [ug/L]
Rainbow trout:
13.0 °C
Fathead minnow:
22.0 °C
100
1000
10000
100000
1/2 x SMAV Lead [ug/L]
Figure 3. Species sensitivity distribution (SSD) for aquatic life. Relative acute sensitivity of white sturgeon
for Cu, Cd, Zn and Pb. Acute LC50 values are divided by two for comparison to ambient water quality
criterion and normalised to a hardness of 50µg/L.
• Different water temperatures for each
species:
15.0 °C
10000
SSD Freshwater Aquatic Life - Lead
100%
10%
1000
1/2 x SMAV Cadmium [ug/L]
SSD Freshwater Aquatic Life - Zinc
10
White sturgeon:
100
10
1/2 x SMAV Copper [ug/L]
20%
30 µg/L — 1950 µg/L
50%
0%
70%
Pb
HAQC
30%
A. oxyrinchus
20%
30%
Cd 2 µg/L — 500 µg/L
*
30
100%
70%
• Metal analysis and total and dissolved organic carbon (TOC, DOC) were measured at the initiation
and termination of the experiments.
20 µg/L — 5000 µg/L
*
• White sturgeon are relatively sensitive to Cu, Cd, Zn and Pb compared to other aquatic species (Fig 3).
• The HAQC is designed to be protective of most aquatic species in a given environment, and for the most part white
sturgeon sensitivity appears to be greater than the HAQC for Cu, Cd and Pb. For Zn, however, white sturgeon
sensitivity is slightly less than the HAQC (Fig 3).
• Regulatory decisions are often based upon the most sensitive species within an ecosystem and the present study
helps to characterize white sturgeon sensitivity to metals.
• Dissolved oxygen, pH, temperature and conductivity were measured daily. Ammonia, nitrates, nitrites,
hardness, alkalinity and chlorine were measured at the initiation and termination of the experiments.
Zn
*
Figure 2. 96h dose response of white sturgeon, rainbow trout and
fathead minnow for Cu and Pb at yolk-sac life-stage (8dph)
> 423*
10%
• Concentrations:
Cu 1 µg/L — 400 µg/L
**
* *
* *
* = significant difference to control (p < 0.001)
Percentile
• Loading density remained below the recommended 0.5g/L, as defined by the American Society for Testing
and Materials (ASTM) guidelines.
*
*
217
80
SSD Freshwater Aquatic Life - Copper
• 96h static renewal lethality tests. During the yolk-sac life-stage, ~8 days post hatch (dph), fish were exposed
in 0.5 L, high density polyethylene (HDPE) test containers to increasing concentrations of the specific
metal. Identical but larger 5L test containers were used during older life-stage toxicity tests.
*
*
HAQC = hardness adjusted quality criteria, UofS = University of Saskatchewan
• Species sensitivity was assessed for the metals in comparison to the data for aquatic organisms published in USEPA’s ECOTOX database (http://cfpub.epa.gov/ecotox/)
• 50% renewal of the test solutions every 12h
• Water: hardness ~ 60 mg/L CaCO3
Figure 1. Experimental set-up for lethality test
• Age: all species were tested during life-stage specific time periods
Days post hatch (dph)
–white sturgeon: 8 dph, 40 dph, 100 dph
Future and upcoming work
• Upper Columbia River sediment characterization study
• Plasma and tissue analysis on 10 adult white sturgeon sampled during the
summer of 2009
–rainbow trout: 10 dph, 40 dph
–fathead minnow: 5 dph
Acknowledgments: Funding for this project was provided by Teck American Incorporated. Thanks to the Kootenay Trout Hatchery, the UofS undergraduate team, the US-EPA and the UCR RI/FS technical advisory team for their advise and support during the planning stage of the studies.