IRL Report Card: Central Indian River Lagoon

The Central Indian River Lagoon extends from south Brevard County south to the Indian River – St. Lucie County line. It includes two regions (Central IRL North and Central IRL South) that have different regulatory targets.

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The Central Indian River Lagoon has three major tributaries entering the North region (Crane Creek, Turkey Creek, and Goat Creek), and a main tributary entering the South region (the Sebastian River, which has four main segments).

Central Indian River Lagoon – North

The Central Indian River Lagoon – North region extends from about the Melbourne Causeway south to the Brevard-Indian River County line. It includes three tributaries (Crane Creek, Turkey Creek, and Goat Creek).

Water quality in the Central Indian River Lagoon North has been consistently below average, and has never met regulatory standards in the 23 years of scoring. Habitat Quality (seagrass) has been much better in the past, even exceeding the healthy targets in 2007 and 2008. After the first major algae “superbloom” of 2010, seagrasses in this region declined and never recovered. See the table below.

Central Indian River Lagoon – North
Water and Habitat Quality

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Central Indian River Lagoon – North Tributaries

The Central IRL – North has three tributaries that enter it (Crane Creek, Turkey Creek, and Goat Creek). Tributary targets were calculated based on the TMDL established in each tributary. See the Health Assessment Methodology Report for more information on targets.

The graph below shows how water quality in the Central Indian River Lagoon North relates to the three main tributaries that enter the Central IRL North. The gaps in the lines represent years where water quality data were not collected for tributary. Notice that neither the Central IRL North and nor its tributaries have ever met the regulatory targets and that Crane Creek water quality appears to fluctuate independent of the lagoon proper, whereas Turkey Creek and the lagoon proper go up and down together. Both the figure and table below show the water quality scores over time in the tributaries and the Central IRL North.

Central IRL North & Tributaries Water Quality

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2020-central-irl-north-and-tributaries-water-and-habitat-quality-scores

Central Indian River Lagoon – South

The Central Indian River Lagoon South includes the area of the lagoon within Indian River County. The main tributary that enters this region is the Sebastian River, which has four main segments.

The graph below shows that water quality in the Central IRL – South has exceeded regulatory standards several times and is consistently improving (the water quality trend line goes up). Seagrass however, continues to decline independent of water quality, suggesting something other than the four regulatory parameters (TN, TP, chlorophyll-a, and turbidity) are driving seagrass health in this region.

Looking more closely at water quality scores, it is evident that Total Nitrogen (TN) is good in this region, scoring consistently above average for over a decade. Phosphorus scores go up and down, swinging from well above average to well below average in a single year in 2015.

Central IRL South Water & Habitat Quality

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2020-central-irl-south-and-tributaries-water-and-habitat-quality-scores

Central Indian River Lagoon – South Tributary (Sebastian River)

The only tributary that enters the Central IRL South is the Sebastian River. The Sebastian River includes a brackish estuary, north and south prongs with variable salinity, and the C-54 drainage canal. Tributary targets were calculated based on the TMDL established in each tributary. See the Health Assessment Methodology Report for more information on targets.

The graph below shows that the Sebastian has worse water quality than the Central IRL – South, suggesting that it is a continuous source of pollution. The graph and the table demonstrate a lack of historic monitoring in the Sebastian North and South prongs as well as the C-54 which makes it difficult to evaluate relationships over time.

Central IRL South & Sebastian River
Water Quality

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