Freshwater mussel shells chronicle changes over the past ...
24
Freshwater mussel shells chronicle changes over the past 1000 years Andrea Fritts INHS INHS
Transcript of Freshwater mussel shells chronicle changes over the past ...
Freshwater mussel shells chronicle changes over the past 1000 years
Andrea Fritts
INHS INHS
•Historical ecology▫ Age & growth
▫ Stable isotopes
▫ Legacy contaminants
Historic INHS researchers
R. Kanter
INHS Mollusk Collection
• >430,000 specimens
• 1861-present
INHS Mollusk Collection
• >430,000 specimens
• 1861-present
• Archeological specimens (1000 years old)▫ Illinois State Archeological Survey
▫ Illinois State Museum
Chicago Ship & Sanitation Canal:
1900 Fish and mussel kills: 1920s
Clean Water Act: 1972
A look into the past…
Haag & Commens-Carson 2008
Silent archives
Sclerochronology• Study of accreted hard structures•Mussels collected in 1894 – present▫ Illinois River at Havana; 2 mussel species▫ Archeological specimens; 1000 years old
Threeridge (A. plicata)
• 1897 specimen▫ 24 yrs old
(Same scale)
• 2013 specimen▫ 5 yrs old
1897
2013
Threeridge (A. plicata) Growth Curve
0
20
40
60
80
0 5 10 15 20 25
Len
gth
(m
m)
Age (yr)
2013
1897 (k = 0.090, Linf 65 mm)
(k = 0.133, Linf 84 mm)
Threeridge (A. plicata) Growth Curve
0
20
40
60
80
0 5 10 15 20 25
Len
gth
(m
m)
Age (yr)
20131966191218971000 A.D.
Mapleleaf (Q. quadrula) Growth Curve
0
20
40
60
80
0 5 10 15 20 25
Len
gth
(m
m)
Age (yr)
2013199419121894
Threeridge Standardized Growth Index
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
1860 1880 1900 1920 1940 1960 1980 2000 2020
Stan
dar
diz
ed G
row
th In
dex
Year
1897
1912
1966
2013
A
BB C
C
Mapleleaf Standardized Growth Index
0.0
0.5
1.0
1.5
2.0
2.5
3.0
1860 1880 1900 1920 1940 1960 1980 2000 2020
Stan
dar
diz
ed G
row
th In
dex
Year
1897191219942013
A
A B
B
B
Potential explanations1.
Potential explanations
1.
2.
Stable isotope signatures• Evaluate nutrient sources from 1890s- present
• Pulverize and process for δ13C & δ15N
Stable isotope results
Chicago Shipping and
Sanitary Canal: 1900
Clean Water
Act: 1973
Isotope discussion
• Enriched nitrogen after 1900 ▫ Indicative of increased sewage & fertilizer input
• Shifting carbon sources
▫ Enrichment indicates Lake Michigan water input
▫ Sewage inputs also enriched in C13
•N15 and C13 indicate shift towards historic conditions in 2013
Legacy Contaminants•Detectable: As, Cd, Co, Cu, Fe, Mn, Ni & Zn
•Undetectable: Al, Cr, Hg, Pb, Se, U, V
Historic & archeological collections = time travel
