This proposal seeks to develop small, economical, low-power sensors to be deployed in networks in coastal marine eco-systems to record levels of CO2, CO3H-, and pH. The sensors will use a hybrid of silicon-based, field-effect transistors and electroactive organic molecules/polymers. These organic materials are designed to have variable Fermi levels that change with pH and CO3H- concentrations. The new sensors can be used for persistent, distributed monitoring of coastal waters needed to understand the effects of river emissions and atmospheric perturbations on ocean ecology. Shallow regions are particularly sensitive to these chemical changes in the water; they are habitat to abundant shell fish populations and also provide a breeding ground for economically important fish species and other sea life. The sensors will allow for the collection of critical spatial-temporal data to be used in models that can explain the origins of chemical changes.