Citing concerns from neighbors, the city will delay a project to create a nature trail through the marsh in the city’s south end, Mayor Jay Gillian said in a message to residents.Plans called for the Crook Horn Creek Nature Trail to run from the end of 51st Street to the Intracoastal Waterway at Crook Horn Creek, along what is now a deeply rutted gravel and dirt road. The proposal was to grade and pave the road to improve access to walkers and bike riders.