Comprehensive Plan for Resolving Marco Canal Water Quality Issues

In his 2021 report to city council, Dr. Harper recommended “Take care of thereuse water (nutrients) first, wait one year and see what happens.” Strip the nutrients out of the reuse water stream to stop the algal blooms that are plaguing the canals. This is the first step – remove the root-source of the canal water quality issues. 

Water quality evidence from 2020 shows that this single step will resolve the low oxygen levels in the canals. When the phosphorus in the reuse water dropped to almost zero in early 2020as a result of COVID, the oxygen in the canals popped back up to healthy levels within weeks. There is significant tidal flushing in the Marco canals. 

The next step would be to focus on restoration of the canal ecosystem after decades of damage. A restoration plan by a qualified environmental school would be in order, perhaps the FGCU Water School. A survey of the canals would show the extent of the damage in the form of algal benthic mats. This survey would inform subsequent restoration activities: surgical dredging, if needed, then oyster restoration, and seagrass restoration. 

An aquatic life baseline would tell the residents the status of the fishery. Like surveys now completed in Naples Bay, this could be repeated on an annual basis to track restoration impact. Of course, monthly water quality monitoring would continueto track the reduction of canal pollutants and the oxygen recovery.  

The restoration plan would need to determine if further nutrient reduction on Marco is required. The second source of nutrients after the sewage reuse water is the drinking (potable) water, 75% of which is used for lawn irrigation. Florida-friendly landscaping might be in order. A 100% fertilizer ban would help to reduce the “nutrient footprint” on Marco Island. Current evidence suggests that these steps would not be needed. After the ecosystemhas recovered, water quality sampling could be dropped back to quarterly, thus saving city funds. 

At a Marco Island presentation on September 18, 2025, Ed Sherwood, Executive Director of the Tampa Bay Estuary Restoration Program, estimated that after the root source ofpollution is eliminated, the Marco canals would cleanup naturally within three to five years.