According to the Turrell Hall & Associates report of February 2019, “Looking at the locations that were sampled to establish the NNC for the Estuary Nutrient Region (ENR), it is interesting to note that only one data point falls within WBID 3278O and that is in the center of the intracoastal waterway at the Jolly Bridge.” WBID 3278O is Marco Island.
Data Collection Locations Used to Help Establish Numeric Nutrient Criteria
NNC stands for “Narrative Nutrient Criterion” established by the Florida Department of Environmental Protection (FDEP). Interpretation of the water quality criterion is stated in terms of Total Phosphorus (TP), Total Nitrogen (TN) and Chlorophyll-a limits. State Surface and Ground Water Standards, Section 62-302.532, shows the allowed limits for the combined Rookery Bay/Marco Island Estuary are: TP = 0.046 mg/L; TN = 0.30 mg/L, and Chlor-a = 4.9 microgram/L.
The only Marco water sampling location in these standard calculations is in the Marco River which flows into the ocean. Actually, NO water samples within Marco Island were included in the calculation for water quality standards for the combined Rookery Bay/Marco Island waters. As a result of this technical oversight, the Marco Island waters have not actually had a base-line study completed in order to set appropriate standards for water quality. We have been “piggybacking” on Rookery Bay for years now.
Marco Island and the Rookery Bay Estuarine System are vastly different water bodies. Per the Rookery Bay website, “Rookery Bay National Estuarine Research Reserve (NERR) stretches across 110,000 acres of pristine mangrove forest…” Contrast this to Marco Island, which is a densely populated community.
Marco Island waters are more comparable to Naples Bay. Marco waters are currently considered “impaired” for a TN measurement of 0.65 mg/L (2018). Good news, over the last 3 months of 2020, the TN levels in our waters have dropped to 0.38 mg/L! The Naples Bay water quality standard for Total Nitrogen (TN) is 0.57 mg/L, twice as high as Marco’s TN standard of 0.3 mg/L
Implications? If the TN standard within Marco waterways remains artificially low, the permitted nitrogen loads for the city, called Total Maximum Daily Load (TMDL), will be low, and many millions of dollars in taxpayer money will be wasted trying to reach a standard that is only appropriate for pristine areas.
Marco Island, Florida