I-54_Durham 2019 Midge Mentum Memo

May 23, 2019
To: Susan Gale
Water Quality Specialist
Stormwater & GIS Services Division
Public Works Department
City of Durham
From: Larry Eaton
Eaton Scientific
2105 Osprey Circle
Raleigh, NC 27615
Re Results of Chironomus deformity hunt and analysis 5/9-10/2019
On May 9th and IOth, I joined Christine Cailleret, Dave Milkreit and Victor Holland in a search
for midges at 5 sites in addition to the regular spring sampling. Searches were successful at all
primary sites. Below is a table summarizing the results of those collections. Only 3rd and 4th
instar midges were examined, even though some 2nd instars were collected, because these would
be older and more prone to develop deformities due to longer exposure.
Summary of midge deformities at Durham sites
Site ID
Stream
Name
Crossing
# Chiron
# Deform
%
Deform
Class
I*
Class
II*
Class
III*
Toxic
score
EL5.5GC
Goose Cr
Camden
Ave
30
0
0
3
0
0
10
EL8.5SEC
S Ellerbe Cr
Club Blvd
30
1
3.3
8
0
1
36.7
EL7.1EC
Ellerbe Cr
Acadia St
22
0
0
3
0
0
13.6
EL1.9EC
Ellerbe Cr
Glenn Rd
30
2
6.7
2
1
1
23.3
NH2.3MC
Mud Cr
Pickett Rd
27
2
7.4
2
2
0
22.2
*Class I are chipped teeth, not necessarily deformitities, Class II are broken or missing teeth, Class III are multiple
Class 11 on a single mentum.
South Ellerbe Creek at Club Blvd and Ellerbe Creek at Glenn Rd were the only streams with
Class III deformities and also had the highest Toxic Scores (36.7 and 23.3 respectively). Mud
Creek at Pickett Rd also had two midges with deformed menta. Curiously, both deformities
were broken menta where the 2nd, 3rd and 4th lateral teeth on the left side of the mentum were
missing. These appeared to be a single fracturing events that caused the loss of three teeth, so
they were counted as a single deformity (Class II), instead of multiple missing teeth (Class III),
which would have risen the Toxic Score to 29.6.