Mussel
Status (continued)
Mussels are considered to be good monitors of pesticides in freshwater environments. In 1971, Starrett examines 14 individual mussels for the presence of organochlorine pesticides. All specimens are found to contain residues of pesticides. The concentration of pesticides does not exceed 0.0585 ppm, and the average is 0.0331. These values are much lower than anticipated given the location of the Illinois River in the agricultural belt. The results of Starrett’s assessment can be found in Table 46.
Table 46. Organochlorine pesticides present in mussels collected from the Illinois River during August 1966 (Starrett 1971)
| Pesticides in Parts Per Million | ||||||
| Kind of Mussel | River Mile Where Mussel Was Taken |
DDT | DDE | Heptachlor Epoxide |
Dieldrin | Total |
| M. gigantea (Washboard) | 42.3 | ... | 0.0322 | 0.0135 | 0.0063 | 0.0520 |
| “ “ | 106.7 | ... | NMP* | NMP | NMP | NMP |
| A. plicata (Three-Ridge) | 42.3 | ... | 0.0107 | 0.0056 | ... | 0.0163 |
| “ “ | 106.7 | ... | 0.0143 | 0.0257 | 0.0143 | 0.0543 |
| “ “ | 171.8 | ... | 0.0275 | 0.0247 | 0.0063 | 0.0585 |
| “ “ | 174.1 | 0.0281 | 0.0056 | 0.0091 | 0.0094 | 0.0522 |
| Q. quadrula (Maple-Leaf) | 42.3 | ... | 0.0089 | 0.0056 | ... | 0.0145 |
| “ “ | 106.7 | ... | 0.0071 | 0.0097 | 0.0045 | 0.0213 |
| Q. pustulosa (Pimple-Back) | 42.3 | ... | 0.0054 | 0.0021 | ... | 0.0075 |
| A. g. corpulenta (Floater) | 106.7 | ... | 0.0179 | 0.0139 | ... | 0.0318 |
| “ “ | 174.1 | ... | 0.0303 | 0.0110 | 0.0073 | 0.0486 |
| “ “ | 196.1 | ... | 0.0066 | 0.0143 | 0.0052 | 0.0261 |
| L. Fragilis (Fragile Paper Shell) | 106.7 | ... | 0.0115 | 0.0111 | 0.0054 | 0.0280 |
| P. alata (Pink Heel-Splitter) | 196.1 | 0.0225 | 0.0066 | 0.0169 | 0.0063 | 0.0523 |
*NMP indicates no measurable peak
In 1996, 23 species are identified, four represented by one specimen and one by only two specimens, a continued decline from 1966; however, more recent mussel surveys demonstrate an improvement in water quality in the upper reaches of the Illinois River. For example, surveys conducted between 1994 and 1999 in the uppermost pool document the presence of twelve species, which is an improvement over the two species observed in 1912 and none in 1966 in the same stretch of river.
Figure 67 illustrates the change in the number of mussel species in the Illinois River from historic records to surveys in 1966 and again in 1993-95. In all stretches of the river, mussels decline precipitously from the historic records of 1874 to 1966, with a slight recovery occurring by 1993, particularly in the Upper Pool.
Figure 67: Number of Mussel Species Recorded in the Illinois River (Cummings 2001)
