Graduation Date


Document Type

Honors Thesis

Degree Name

Bachelor of Science


Natural Sciences and Mathematics

Director of the Honors Program

Gigi Gokcek, PhD

First Reader

Diara Spain, PhD

Second Reader

Doreen Gurrola, MS


Ocean acidification has emerged as an issue for marine organisms, due to increased levels of CO2 in the atmosphere. In particular, invertebrates with calcium carbonate exoskeletons seem to be at risk. Our research investigates the potential effect of decreased pH on the weight of Hemigrapsus nudus, a species of intertidal crab found in Northern California. Over a 6 week period, crabs were maintained in individual containers with recirculating chilled seawater at 12.7°C. The control aquaria was maintained at 8.1 pH, while the experimental aquaria averaged a pH of 7.5. Crabs were weighed at two week intervals, preliminary information shows the control crabs increased in weight, while experimental crabs lost weight. Our results suggest that the decreased pH is possibly affecting a component of calcification needed for strong exoskeleton.


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