March 9, 2004
Factors Affecting the Shoreline Distribution of Asiatic Clams, Corbicula fluminea (Müller), in the Hanford Reach,
Columbia River
Behr Turner, Battelle PNNLBrett Tiller, Battelle PNNL
Dr. Allan Scholz, EWU
March 9, 2004
Acknowledgements
• Battelle Staff:– Corey Duberstein– Dr. Janelle Downs– Dr. Bill Rickard– Ted Poston– Craig McKinstry– Bob Mueller– Ian Welch– Mickey Chamness– Donald Mendoza– Brad Fritz– Kate Deters
• PNNL OFP and Research Fellows:– Rochelle Shipley– Joe Zelinski– Kyle Larson– James Bernhard
• Eastern Washington University Staff:– Dr. Bruce Lang– Dr. Nancy Birch– Holly McLellan
• Conducted for the U.S. Department of Energy by Pacific Northwest National Laboratory under contract DE-AC06-76RLO 1830
• EWU Biology Department Graduate Research Grant
• EWU Alumni Graduate Research Grant
March 9, 2004
Introduction to Asiatic Clam
• Exotic– From South-central Asia– Believed to have been introduced in the 1920’s (McMahon 1983)
- Chinese immigrants- Voyage food source
– In 1938, this species was first identified in U.S. (Burch 1944)– No records of Asiatic clams in Hanford Reach of the Columbia River
during 1960’s and 1970’s
• 3-year life span• Established in Hanford Reach• Shoreline distribution affected by dewatering (Junk 1975;
McMahon 1979; Mouthon 2001; White 1979; White and White 1977)
March 9, 2004
Study Impetus
• Sentinel for monitoring Hanford-related metals and radionuclides in the environment– 47 years of plutonium production on the Hanford Site– Groundwater
- Current route of contaminant introduction to river
• River fluctuations complicate interpretation of sampling results and affect species distributions – River/Groundwater interaction affects contaminant uptake– Dewatering events affect condition and survival
• Need to describe shoreline distribution of A. clams along the Hanford Reach of the Columbia River
March 9, 2004
Hanford Reach of the Columbia R. and Study Area
March 9, 2004
Introduction
• Hanford Reach of the Columbia River– Last free-flowing stretch in
U.S. above Bonneville Dam– Great fluctuations in river
elevation- Due to hydraulic
operations at Priest Rapids Dam
- Flows greatly altered from natural state
March 9, 2004
Historic Versus Recall Flow Patterns
FCRPS 2001; Columbia River DART 2002
0
2000
4000
6000
8000
10000
12000
O N D J F M A M J J A S
Water Year
Flow
(m3 ·s-1
)
Historic
2001-2002
March 9, 2004
Site Conditions
• Study Area– 15-km stretch of the Hanford Reach– Characterized by swift currents and cobble substrate – Variable flows during sample seasons
0
2000
4000
6000
2002
Flow
(m3 •
s-1)
March 9, 2004
The Percentage of Time Shoreline Submerged on an Annual Basis
• Bathymetry transects– USGS and Grant County Public Utility District
• Hourly Priest Rapids Dam flow data– 1994-2001– 10 increments – a flow frequency distribution
• One-dimensional modular aquatic simulation system coupled with GIS– MASS1 (Richmond et al., 2000)– Generated GIS positions of known amounts of shoreline
submergence
March 9, 2004
Established Time Percentages of Shoreline Submergence and Corresponding Flows from 1994-2001 Priest Rapids Dam Hourly
Flows
1,35395.001,63090.001,83785.001,97080.002,13975.002,42570.002,72065.002,98360.003,23855.00
3,46350.00m3·s-1Percentage of time shoreline submerged
March 9, 2004
114
116
118
120
122
124
126
128
1300
100
200
300
400
500
600
700
800
Distance (m)
Elev
ation (m
abo
ve se
alev
el)
Bathymetry
50% Submerged
55% Submerged60% Submerged
65% Submerged
70% Submerged
75% Submerged
80% Submerged
85% Submerged90% Submerged
95% Submerged
Depiction of MASS1 Flow Levels and River Bathymetry
March 9, 2004
Distribution Data Collection
• Data collected August 30-September 29, 2002
• Two methods used to locate sample sites:– 1) Navigate to reference GIS position
- Trimble GeoExplorer® 3 handheld GPS mapping and GIS data collection/maintenance system
– 2) Average position of 50 percent submerge rate and transect bearing- Sample equidistant along transect to a depth of 1.5 m
• GIS point recorded at each location– Average of 100 positions logged at a rate of 1 position per
second - Precision less than 3 m
March 9, 2004
Distribution Data Collection
• Asiatic clam presence/absence:– Two 0.1-m2 plots randomly placed within 1-m2 plot
March 9, 2004
26 Shoreline Sites of Distribution Data Collection
March 9, 2004
Distribution Data Analysis
• Chi-Square Tests of Homogeneity– Based on presence and absence– Tested 11 shoreline submergence durations
• Pairwise comparisons– (Marascuilo and McSweeney 1977)
March 9, 2004
Asiatic Clam Distribution For Shoreline Submergence Intervals
Χ2>101.56, d.f.=10, p<0.05
0%
20%
40%
60%
80%
100%
<50
50-5
5
55-6
0
60-6
5
65-7
0
70-7
5
75-8
0
80-8
5
85-9
0
90-9
5
>95
Freq
uenc
y of
occ
urre
nce
March 9, 2004
Discussion
• Asiatic clam distribution– Intolerant to aerial exposure
– In other bodies of water, clams not found in dewatered shorelineareas (Junk 1975; McMahon 1979)- 50 % mortality after 4 days exposure (White and White 1977)- 98 % mortality after 12 days exposure (White 1979)
– Some shoreline areas experienced several consecutive days of dewatering at air temperatures exceeding 35 oC- A. clams were present in such areas
March 9, 2004
Discussion
• Asiatic clam distribution mechanism– Mucous thread creates buoyancy– Clams 14 mm in shell length could maintain buoyancy in
0.1 m·s-1 current (Prezant and Chalerwat 1984)– Deposited during flow fluctuations
March 9, 2004
Asiatic Clam Size Class Distribution between Three Functional Shoreline Zones in the Hanford Reach
0%20%40%60%80%
100%
Vascular vegetation Non-vegetated substrate Periphyton
(n=27) (n=1082) (n=986)
Perc
ent o
ccur
renc
e 5-11 mm
11-22 mm
>22 mm
Non-vegetated substrate Periphyton
Shoreline vascular vegetation
March 9, 2004
Conclusions
• Clams were consistently found in shoreline areas submerged > 90 percent of the time on an annual basis
• Dewatering is a environmental stressor
• Future aquatic biota exposure and impact studies on the Hanford Reach of the Columbia River (and other regulated river systems) should be performed at or below the low-water level