Sounds like a Public Assembly (for the US) which would be 100 psf live load (non-reducable). However, for such a unique situation, it would be good to contact the local building department or relevent officials to get their take on it as well.
Is the pier subject to vehicular traffic? May also have to consider if a fire truck will ever have to access the wharf. This could influence the design. If the answer to the above questions is no, I would use the 100 psf also.
