Fennel model nutrients accumulate in lower minimum depth

[ttliu]

Hi all,
I'm new in modeling and have a problem about minimum depth.
My group has a model in a shallow bay using Fennel biology model.
It ran well when we use 3m as the minimum depth. But now for some reason we need the depth shallower, so we use new grd file in which we change the min depth to 1.5m.
Now in coastal area NH4 and NO3 accumulate fast and lead to Chl bloom, then NH4 and NO3 decrease sharply, then accumulate again.
Not sure which cause this, I tried to decrease the bottom flux of NH4 and decrease river input, but no use.
Figures are time series of surface value of two GRD result in the same location close to an estuary.

Please help me.
Thanks!

[kfennel]

Looks to me like the change in your grid file affected the circulation in your shallow bay with longer flushing time leading to more trapping of nutrients. Note that your salinity has changed as well.