On occasion I've relieved myself in the lake. #1 only but sometimes crossing open water, you got to go.
Considering all the thousands of critters that use the waterways as toilets, a paddler occasionally peeing is hardly going to upset the "balance".

Urine is sterile and IF your wife or you ave ever had a "perm" back in the day's of big hair, one of the active ingredients is Urea which is found naturally in urine.
Ever smell someone's hair whiles their getting a perm? Yup, smells like my cats litter box pre-cleaning. ;) :P