Department Chair

Daniel L. Potts, Ph.D.

Date of Award


Access Control

Open Access

Degree Name

Biology, M.A.


Biology Department


Alicia Pérez-Fuentetaja, Ph.D.

Department Home page

First Reader

Alicia Pérez-Fuentetaja, Ph.D.

Second Reader

Christopher Pennuto, Ph.D.

Third Reader

Randal Snyder, Ph.D.


The water calcium concentration of northern softwater lakes has declined to critically low levels due to numerous anthropogenic stressors, and the availability of calcium is expected to decline further. To assess the impact that critically low water calcium has on aquatic snail shell calcification and growth, juvenile Planorbella trivolvis were raised for 60 days in one of four treatments, each containing a different amount of dissolved calcium (0.64, 1.3, 2.5, and 5.1 mg/L). There was no difference in tissue weight or shell size among treatments, suggesting low water calcium concentrations do not impact adult body mass or size. However, snails had reduced shell calcium when reared in water containing less than 2.5 mg/L calcium, with larger snails being more deficient. For snails in the highest calcium treatment (5.1 mg/L Ca), the amount of shell calcium relative to total dry weight increased during the experimental period; however, for snails in the two lowest calcium treatments (0.64 and 1.3 mg/L Ca), percent calcium decreased until day 30, after which it increased but to a lesser extent than snails in the two highest calcium treatments (2.5 and 5.1 mg/L Ca). Interestingly, smaller snails had shells with more calcium relative to total dry weight than larger snails and required less water calcium to biomineralize their shell. These results indicate that adult size and body mass are not affected by low water calcium, but shell calcification is negatively affected by declining water calcium concentration with the effects being greater for larger snails within a species.