This error may have been identified before, but I did not see anything in the ecosystem discussion. Depending on how folks develop other ecosystem models, this error might have migrated to other ecosystem codes.
At the end of the sinking code in fennel.h, there are statements to remineralize phytoplankton nitrogen from cells that hit the bottom. The code is given below.
! add code from Fennel.h to account for phyto reaching the bottom
! based on remineralization of phyto nitrogen
if (ibio.eq. iPhyN) THEN
The problem is in the references to the Bio array which should be i,1 not i,i so that the the bottom concentrations are changed. Depending on the tiling and the number of vertical levels, this could do interesting damage to a calculation.
The correct lines are