1. Downeast Maine Rivers Chronically Low pH and High Organic Aluminum
Experimental (Pilot) Clam Shell Addition Project
Assessing shell degradation rates over a range of stream influences
Discarded clam shells
at shucking facility
Free Calcium
to increase stream pH!
5kg aliquots
5kg bags
of clam shells
Stream
Variables:
Water Temp pH
Velocity
High Velocity site
Weighing bags

2. Sample Locations in Machias (7) and East Machias Rivers (1)
* Inferred from Robinson et al. 2003

3. How “Big” are They? Dry Weight Density Kg/m3 ½ shell Composition;
88-92% CaCO3
Dry Weight Density
How “Big” are They?
Kg/m3
½ shell

4. In Vitro Analysis
Bucket with g of shells- no flow!
Ambient pH pH
Just after
Filling Bucket
“pH”
24 hours after
Filling Bucket?
No Agitation
End Weight g
8.50
6.59
6.58

5. In Situ Methods Placed 5 (5 kg) bags of clam shells per stream
Duration Sept 2nd through November 21st (80 days)
Sampled weekly through Oct 21st
Recorded
-Visual Shell Loss
-Insect Colonization (very few observed)
-pH
-Water Temp
-Water Velocity
Transformed Shell Loss data to “Normalize Distribution”
Log (238+ g/day shell loss)

6. Log (238+ g/day shell loss)
Omit these from
further analysis
Log (238+ g/day shell loss)
Nominal Variables:
0 No visible loss
1 Small particle loss
2 Medium particle loss
3 Large particle loss

7. After removing all data where shell loss was observed
Assessed Degradation with 3 Independent Nominal Variables
Stream Velocity pH
Time-Temperature

8. statistically significant
Summary:
Statisticians have not yet resolved the high degree of variability within the data set- The jury is still out on these interactions!
Degradation ~22 g/day (0.5%/day)
~193 days to “Disappear”
Although not
statistically significant
Stream Velocity, pH
&
Date-Temp
may effect degradation rates

9. Air Temps and Discharge
Old Stream USGS Gage

10. Maine DEP Sonde “pH” Data
Data courtesy Mark Whiting