A user-friendly, stand-alone application for the calculation of carbonate system parameters was developed by the U.S. Geological Survey Florida Shelf Ecosystems Response to Climate Change Project in response to its Ocean Acidification Task. The application, by Mark Hansen and Lisa Robbins, USGS St. Petersburg, FL, Joanie Kleypas, NCAR, Boulder, CO, and Stephan Meylan, Jacobs Technology, St. Petersburg, FL, is intended as a follow-on to CO2SYS, originally developed by Lewis and Wallace (1998) and later modified for Microsoft Excel? by Denis Pierrot (Pierrot and others, 2006). Besides eliminating the need for using Microsoft Excel on the host system, CO2calc offers several improvements on CO2SYS, including: An improved graphical user interface for data entry and results Additional calculations of air-sea CO2 fluxes (for surface water calculations) The ability to tag data with sample name, comments, date, time, and latitude/longitude The ability to use the system time and date and latitude/ longitude (automatic retrieval of latitude and longitude available on iPhone? 3, 3GS, 4, and Windows? hosts with an attached National Marine Electronics Association (NMEA)-enabled GPS) The ability to process multiple files in a batch processing mode An option to save sample information, data input, and calculated results as a comma-separated value (CSV) file for use with Microsoft Excel, ArcGIS,? or other applications An option to export points with geographic coordinates as a KMZ file for viewing and editing in Google EarthTM