1. The effects of phosphate on energy reserves in Chironomus tepperi
Molly Hoak
PhD Student
CAPIM Research Summit, August 2016

2. Background: Phosphorus
Essential nutrient for plants and animals
Important component of ATP
Occurs naturally as phosphate (PO4)
Image: Peter Woodward

3. Background: Why Phosphate?
Enters waterways through agricultural and urban runoff, sewage effluent, and leaking septic systems
Causes algal blooms
More important than other nutrients as a contributor to eutrophication
Photo: Lori Volkart

4. Background: Why Phosphate?

5. Aim
To determine how different levels of phosphate affect the development and energy use of Chironomus tepperi

6. Chironomids Exposed to contaminants in sediment and pore-water
One of the families recorded in site bioassessments
Easy to culture in laboratory

7. Effects of Phosphate: Prior experiments
Water-only chronic exposure (to emergence)
Chironomus tepperi 2nd instar larvae
0, Control (0.5), 5, 10, 20, 40, 80 mg/L
Early emergence in 10 mg/L
p ≤ 0.05

8. Methods Sediment exposure Laboratory culture of chironomids
Overlying water dosed with KH2PO4
Concentrations of 0, Control (0.5), 5, 10, 20, 40 mg/L
8 replicates, 4 sacrificed after 96 hrs
Laboratory culture of chironomids
Exposed from 2nd Instar (5 days old)
4 replicates sacrificed at 96 hrs for growth, protein, lipid, and glycogen tests
4 replicates exposed until emergence

9. Results: Emergence

10. Results: Emergence

11. Results: Growth

12. Results: Protein

13. Results: Lipid

14. Results: Glycogen

15. Results: Summary
The effect on emergence is much less pronounced in sediment tests than in water-only tests
There is still high variability in the 10 mg/L concentration
Glycogen and lipid concentrations trend lower in the 5 and 10 mg/L concentrations
Protein concentration trends lower at high levels of phosphate

16. Conclusions Sediment makes it more complicated
Energy reserves of C. tepperi seem to be lower at 5 and 10 mg/L of phosphate
However, does not necessarily translate to developmental effects
Lower energy reserves in combination with other stressors could have developmental effects

17. Questions?