Rule 62-303.350. Assessments of Numeric Interpretation of Narrative Nutrient Criteria

(1) The numeric interpretations of the narrative nutrient criterion in Rules 62-302.531 and 62-302.532, F.A.C., and the nutrient impairment thresholds identified in Rules 62-303.351 through 62-303.354, F.A.C., shall be the primary means for assessing whether a water should be assessed further for nutrient impairment. Other information indicating an imbalance in flora or fauna due to nutrient enrichment, such as algal blooms or mats, excessive nuisance macrophyte growth, decrease in the distribution (either in density or areal coverage) of seagrasses or other submerged aquatic vegetation, adverse changes in algal species composition, excessive diel oxygen swings, shall also be considered for placing waters on the Planning List.

(2) To be used to determine whether a waterbody should be assessed further for nutrient enrichment, data must meet the requirements of subsections and paragraphs (2), (3), (4)(a), (4)(c)-(e), (8), (9), (12) and (13), in Rule 62-303.320, F.A.C.

(3) To calculate an annual geometric or arithmetic mean for TN, TP, NO3-NO2, or chlorophyll a, there shall be at least four temporally-independent samples per year with at least one sample collected between May 1 and September 30 and at least one sample collected during the other months of the calendar year. To be treated as temporally-independent, samples must be collected at least one week apart.

(4) To assess nutrient criteria expressed as a long-term average of annual means, annual medians, or annual geometric means for TN, TP, NO3-NO2, or chlorophyll a, the long-term average of annual means, annual medians, or annual geometric means shall be based on data from at least 3 years meeting the minimum data requirements of subsection 62-303.350(3), F.A.C.

(5) To assess nutrient criteria expressed as a long-term average for TN, TP, NO3-NO2, or chlorophyll a, the long-term average for nutrients shall be based on a minimum of 10 data points over at least 3 years, with at least two temporally independent samples per year, with at least one sample collected between May 1 and September 30 and at least one sample collected during the other months of the calendar year.

(6) The assessment of nutrient criteria expressed as a salinity or specific conductance dependent equation shall be based on salinity or specific conductance measurements taken at the same station and time as the applicable nutrient concentration samples.

(7) To assess nitrate-nitrite criteria expressed as monthly averages, the monthly average nitrate-nitrite shall be calculated using a minimum of one sample collected within the month.

(8) To be assessed under this chapter, except for data used to establish historical chlorophyll a levels and estuary-specific numeric interpretations of the narrative nutrient criterion for estuaries in subparagraphs 62-302.532(1)(b)1.-7., F.A.C., chlorophyll a data shall be determined using Department-approved methods as measured according to the requirements as set forth in Chapter 62-160, F.A.C. Rulemaking Authority 403.061, 403.067 FS. Law Implemented 403.062, 403.067 FS. History–New 6-10-02, Amended 12-11-06, 7-2-12, 2-17-16, 11-25-25.