If ROMS 2.1 is built with BIO_FASHAM defined and CARBON undefined, the compiler stops with "undefined variable" messages in mod_ncparam.F. This is because the CARBON-related variables are not wrapped in an #ifdef CARBON ... #endif block.
The diffs are as follows:
856d855
< # ifdef CARBON
865d863
< # endif
922d919
< # ifdef CARBON
955d951
< # endif