Report Date - January 15th to January 21st, 2024

Prepared By: Summer Manestar & Andrew Kamerosky

For the week of January 15th, 2024, the estimated median Chlorophyll A (ChlA) increased across most of the Indian River Lagoon (IRL). As there was only one viable S3 scene this week, the statistics from the January 10th, 2024, scene will be referred to (Table 1).

The Southern Banana River Lagoon (S-BRL) was observed to have the only decrease in ChlA from 17.8 to 13.9 µg/L on January 20th. The Southern Mosquito Lagoon (SML), Central-North IRL (C-NIRL), Central Banana River Lagoon (C-BRL), Southern-North IRL (S-NIRL), and Northern-Central IRL (N-CIRL) had median ChlA concentrations in the mid-level bloom range between 20 to 80 µg/L. The remaining segments of the IRL were all in the low-level bloom range between 6 to 20 µg/L.

There was one (1) usable Sentinel-2 scene and one (1) usable Sentinel-3 scene during this period.

There was one (1) partial scene from Sentinel-2 that was usable for the detection of bloom activity the week of January 15th (Figure 1). Of note in this scene is the presence of medium bloom activity in the N-BRL and N-CIRL.

Figure 1 - Processed Sentinel-2 imagery for January 20, 2024

Sentinel 3

There was 1 scene from Sentinel 3 that was usable for detection of bloom activity the week of January 15th, therefore imagery from the week prior was used for comparison (Figure 2, Figure 3). The following analysis focuses on scenes from January 10th to 20th (Figure 4, Figure 5). 

Figure 2 - Processed Sentinel-3 imagery for January 10, 2024

Figure 3 - Processed Sentinel-3 imagery for January 20, 2024

Figure 4 - Sentinel 3 estimated Chlorophyll A (ChlA) Levels in Micrograms/Liter (µg/L) for January 10th and 20th, 2024, over sections of the Southern Mosquito Lagoon (SML) and North Indian River Lagoon (NIRL). The box plots represent the range of estimated ChlA values for each Basin, with the boxes showing the second quartile, median, and third quartile, and the whiskers representing the first and fourth quartiles.

Figure 5 - Sentinel 3 estimated Chlorophyll A (ChlA) Levels in Micrograms/Liter (µg/L) for January 10th and 20th, 2024, over sections of the Banana River Lagoon (BRL) and Central Indian River Lagoon (CIRL). The box plots represent the range of estimated ChlA values for each Basin, with the boxes showing the second quartile, median, and third quartile, and the whiskers representing the first and fourth quartiles.

Table 1 - Sentinel-3 estimated median ChlA in µg/L and percent change between January 5th and 10th, 2024, by IRL Basin.

SJRWMD IRL Continuous Monitoring Stations

The St. Johns River Water Management District (SJRWMD) Continuous Monitoring (CM) stations measured Chlorophyll Reflective Fluorescence Units (RFU). (Figure 5, Table 2). It should be noted that there was no data (ND) reported at IRLM02 from January 15th to the 21st.

Current and historical data are added to the SJRWMD’s database continuously; subsequent visits may reflect such additions or revisions. SJRWMD provides no warranty as to the accuracy, reliability, or completeness of these data.

Figure 6 – St. Johns River Water Management District (SJRWMD) Indian River Lagoon (IRL) Continuous Monitoring Station Relative Chlorophyll A (ChlA) readings for the week of January 15th, 2024.

Below are the estimated ChlA levels measured by SJRWMD continuous monitoring stations for the week of January 1st, 2024 (Table 2). The Continuous Monitoring Station data is reported hourly by SJRWMD, and this report provides the 95th percentile of RFU for a given day. IRLML02 continues to be non-responsive.

Table 2 – St. Johns River Water Management District (SJRWMD) Indian River Lagoon (IRL) Continuous Monitoring Station Average Relative Chlorophyll A (ChlA) 95th percentile levels for the week of January 15th, 2024.

The availability and usability of satellite imagery is contingent upon both the satellite being overhead and low cloud cover. The orbits of the Sentinel satellites will sometimes cover a portion versus all of the Indian River Lagoon. Cloud cover can also result in only portions of the Indian River Lagoon (IRL) being visible. Table 3 below lists the availability of Sentinel imagery and its usability for Harmful Algal Bloom (HAB) analysis.

Table 3 - Sentinel 2 and 3 imagery availability for the week of January 15th, 2024.

N - Imagery Not Available

Y - C - Imagery Available, Cannot Use Due to Cloud Cover

Y - P - Imagery Available, Only Partial Imagery of IRL

Y - G - Imagery Available, No Issues Over the IRL

Methods

HAB’s observed by this project are defined as over 80 Micrograms/Liter (µg/L) Chlorophyll A (ChlA) (as estimated by a calibrated Normalized Difference Chlorophyll Index (NDCI)) and persistent across the week in review. The algorithms that transform the NDCI index value to estimated ChlA concentrations were developed using a second-order polynomial equation. The Sentinel 2 (S2) equation has a Root Square (R2) of 0.81 with a Root Mean Square Error (RMSE) of 14.14 ug/L of ChlA. The Sentinel 3 (S3) equation has an R2 of 0.92 and an RMSE of 9.92 ug/L ChlA. The RMSE is a measure of the accuracy of a model in estimating values, ChlA in this instance, where a lower value is indicative of higher accuracy. It does not identify if the model consistently over or underestimates the modeled values. The equations are below:

• S2 Estimated ChlA = 297.36(NDCI)2 + 313.98(NDCI) + 36.152

• S3 Estimated ChlA = 437.07(NDCI)2 + 348.98(NDCI) + 33.928

   Figure 7 - SJRWMD Continuous Monitoring stations and IRL Basins used for S2 and S3 analysis. 

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