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White sturgeon (Acipenser transmontanus) in the Columbia River have been experiencing poor recruitment for over three decades. There are many possible causes for this phenomenon, including pollution and/or altered substrata due to anthropogenic activities. In particular, a metallurgical facility in
Trail, B.C. Canada, historically released slag, a partially vitreous by-product of the metal refining process, into the Columbia River. There are concerns that slag may be toxic (e.g. leaching of metals), and/or could cause mechanical damage (e.g. fine particle size and sharp edges) to early life-stages of white sturgeon.
In addition, little is known about the preferred substratum and its appropriate grain and cobble size for successful rearing of early life-stages of white sturgeon (often due to altered habitats as a result of river damming).
The purpose of this pilot study was to gain insight into the effects of slag containing sediments as well as to determine the suitability and preference of various substrata found in the river system. Substrata upstream and downstream of the metallurgical facility were initially investigated by means of an underwater video camera and later retrieved using a sediment grab sampler. Two sites were chosen upstream of the facility near Birchbank B.C., a potential spawning site, and two sites were chosen downstream of the facility near Waneta B.C., a known spawning site of A. transmontanus.
Substratum preference study
• Two eight foot circular tanks were divided into four quadrants (Fig 3). The first quadrant contained BB sediment (Fig 4), the second contained BB sediment with cobbles ranging from ~ 10mm-30mm (Fig 5), the third quadrant contained W sediment (Fig 6), and the last quadrant contained no sediment
• A cross-like separator was fabricated and placed in the tank during times of counting so that fish would remain in their quadrants. Counting was performed 3 times a day, once in the morning and evening (when sturgeon tend to be most active), and once during the day
The substratum at the downstream sites contained varying degrees of slag whereas the upstream sites contained no slag at all.
Two pilot experiments were conducted in the laboratory using riverine and artificial substrata to test for substratum suitability and preference. For the substratum suitability study, seven different substrata compositions from the river were formed using varying degrees of slag, sediment and cobble.
Two control chambers were used; one with an artificial laboratory substratum composition and a second with no substratum.
Endpoints included mortality and morphological alterations, as well as observational changes in behavior. Results indicate that there was no difference in mortalities between substrata containing slag versus the controls. Substratum containing cobble tended to have slightly greater survival rates. Morphological alterations to the physical effects of slag are still being assessed.
For determination of the substratum preferred, large circular tanks were divided into four quadrants. Two quadrants contained sediment from upstream of the metallurgical facility; one with cobble and the other without. The third quadrant contained sediment with slag from downstream of the metallurgical facility. A fourth quadrant with no sediment was used as a control. Early life-stages of white sturgeon were observed and recorded for substratum preference in the morning and at night, when they tend to be most active, and once during the day. Results indicate that yolk-sac sturgeon greatly preferred the upstream sediment with cobble (p < 0.001). There was no significant avoidance of the slag containing sediment versus the upstream sediment of similar grain size or the control. Once the larva matured and switched to exogenous feed, however, no substratum preference was demonstrated. Valuable insight was gathered from both pilot studies that will help to enable successful Columbia River sediment characterization studies in 2010.
Substratum suitability Figure 4. Birchbank Ssediment
Figure 5. Birchbank with cobble sediment
Figure 6. Waneta sediment Figure 3. Substratum preference tank with four sediments
• No significant differences in mortality were observed between slag-containing sediments and control sediments
• Sediments containing cobbles had slightly lesser mortality compared to their counterparts without
• Yolk-sac sturgeon exposed to sediments composed of finer grain sand-like material would sometimes burrow into the substratum as opposed to those exposed to the slag
• Yolk-sac sturgeon exposed to sediment groups with cobbles tended to burrow beneath the cobbles compared to yolk-sac sturgeon exposed to non-cobble-containing sediments that would often congregate head first in the corners of the exposure chambers
• Preliminary measurements of copper (Cu) indicate no significant differences in overlying water from sediments upstream or downstream of the metallurgical facility (table 1).
• Cu analysis on digested sediments indicate significantly greater concentrations in sediments from Waneta and
Beaver Creek compared to Birchbank (Table 1).
•
Substratum preference
Yolk-sac sturgeon displayed a strong preference for
Table 1. Mean Cu concentrations of overlying water (OV) and digested sediment
(DS) for control sediment (Ctrl), Birchbank sediment (BB), Beaver Creek sediment
(BC) and Waneta sediment (W). Waneta sediment collected from the river during
September 2009 (WRS) was analyzed without being used in exposures.
Birchbank sediment with cobble (p < 0.001) Metal Matrix
• There was no significant avoidance of the slagcontaining sediment versus the upstream sediment of similar grain size or the quadrant without sediment
• No substratum preference was demonstrated by juvenile sturgeon (> 30 days post hatch) Cu (µg/L)
OW
0.8
Ctrl
DS
1.1
OW
1.7
BB
DS OW
3.1
1.9
BC
DS
193
OW
2.3
W
DS
WRS
DS
774 940
• White sturgeon eggs were obtained from the Kootenay Trout Hatchery,
B.C., Canada
• Sediments were collected from the Columbia River near Birchbank (BB),
Beaver Creek (BC) and Waneta (W) dam (Fig 1)
• Exposure sediments were categorized into four groups:
BB = ~ 0.5mm-1.0mm grain size, sand like composition
BC = ~ 0.5mm -1.0mm grain size, sand slag mixture
W = ~ 1.0-2.0mm grain size, primarily slag composition
Ctrl = ~ 0.5mm grain size, fine sand composition
Substratum suitability study
• Flow through exposure chambers were covered with a 1 inch layer of sediment from each group, replicated 4 times (Fig 2)
Figure 1. Map of sediment sampling sites near Birchbank, Beaver Creek and
Waneta along the Columbia River
• Slag-containing sediment from Waneta in the Columbia River, Canada, does not appear to affect mortality of sturgeon in a flow through sub-chronic exposure, however, physical impacts of slag on fish morphology has yet to be assessed
• Yolk-sac sturgeon appear to burrow head first into sediment and attempts to do the same in slag may cause damage to the larva, due to the mechanical characteristics of slag (e.g. sharp edges)
• Sediments collected downstream from the metallurgical facility contain relatively high concentrations of Cu in digested sediments
• Pore water appear to have elevated Cu concentrations, although further analysis is still required
• White sturgeon are benthic scavengers who prey on sediment dwelling invertebrates, raising the question about possible bioaccumulation of contaminants
• Yolk-sac sturgeon displayed a strong preference for cobble substrate (> 80%), mostly likely an innate behavior to avoid predation during endogenous feeding
• Habitat alteration, damming and sedimentation due to anthropogenic activities may play an integral role in the recruitment failure of white sturgeon
• Cobbles ranging from ~ 5mm-15mm were added to 2 out of the
4 replicates from each sediment group to test if the presence of cobbles affects behavior and mortality
• 2 control exposure chambers contained no sediment
• Sturgeon were exposed from hatch for 60 days
• Full sediment characterization study in 2010
• Possible investigations into bioaccumulation of metals
• The effects of pore water versus overlying water
• Overlying water, pore water and digested sediment are currently being analyzed for metals
Figure 2. Exposure chambers with sediment
Acknowledgments: Funding for this project was provided by an unrestricted grant from Teck American Incorporated to the Univ. Saskatchewan. 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.