FDEP: Stormwater Unlikely Cause of Indian River Lagoon Superbloom

BREVARD COUNTY, Florida -- The Florida Department of Environmental Protection (FDEP) said that it "does not believe the nutrient loads from specific stormwater and wastewater discharges were the culprit for the Super Bloom" in the Indian River Lagoon.

This statement from FDEP comes after a Brevard Times inquiry into a seeming conflict with government research and publications regarding the cause of nutrient loads in the Indian River Lagoon, the algal Superbloom of 2011-12, and seagrass loss.

An excerpt from FDEP's 2013 BASIN MANAGEMENT ACTION PLAN  stated:

"The median depth limits for seagrass coverage in the BRL subbasin decreased over the years due to changes in water quality conditions resulting from anthropogenic influences. As polluted runoff reached the lagoon, it created conditions that prevented the seagrass from growing in deeper water."

But according to the Saint John's River Management District's  (SJRWMD) Indian River Lagoon 2011 Superbloom Investigation, stormwater and wastewater discharges were unlikely causes for the algal Superbloom that caused large-scale seagrass loss:
"It was more surprising that the event even happened at all given the long-term drought conditions during the 2009 – 2011 period [and the] decreasing trend in treated wastewater discharges... drought means comparatively little rainfall-runoff...The other major external sources – atmospheric and groundwater – are similarly affected by rainfall and would be diminished during the same period. Therefore; notwithstanding some unreported nutrient-laden discharge, an internal flux of nutrients may be the primary mechanism that fueled the bloom. " (Emphasis added).

FDEP explained in an email to Brevard Times the reason for the seeming conflict:

"While the Basin Management Action Plan for the Indian River Lagoon Basin Banana River Lagoon was published in 2013, the excerpt provided is referencing a long-term trend used to establish total maximum daily load (TMDL) standards in 2009. The excerpt does not reference and is not in reference to the Super Bloom." (Emphasis added).

"The SJRWMD excerpt is referencing a specific trend from 2009 – 2011. It is also commenting on stormwater and wastewater discharges and noting that they as specific discharge events are not believed to be the triggers directly causing the Super Bloom.   (Emphasis added).

Stating that anthropogenic influences impact water quality is not at odds with stating that stormwater and wastewater discharges are unlikely causes for the specified algal Super Bloom.  The Indian River Lagoon has been impacted by anthropogenic actions and sources of nutrients for many decades.  A part of the load of these nutrients is stored within the Lagoon as a legacy source of nutrients." 

"The St. Johns River Water Management District (SJRWMD) created an IRL 2011 Consortium to conduct a comprehensive data analyses to examine the possible causes," FDEP added.  "So far, no consensus has been reached among scientists on the exact causes.  The results of investigations will probably not be fully known till 2016 or 2017."

Nutrients Produced by Manatees in the IRL

FDEP also addressed the effect of the increased manatee population on the nutrient load in the Indian River Lagoon which many Brevard County waterfront property owners, boaters, and anglers blame for the Lagoon's plight.

Graphic Credit: SJRMD.  Tropical Storm Fay, Florida Fish and Wildlife Manatee Count, Coldest Winter,  and Superbloom added by Brevard Times

As the above graphic shows, the manatee count on Florida's East Coast has nearly doubled since 2007 (the Florida Fish and Wildlife Commission cautions that the published manatee survey count provides a minimum count of manatees, but it does not provide an accurate population estimate).

"At the time the seagrass TMDLs were developed [in 2009], manatees were not considered as major nutrient contributors to the Indian River Lagoon because not all the data needed to quantify the manatee nutrient contribution were available.  It is worth noting that manatees have been part of the Indian River Lagoon ecosystem for a long time," FDEP stated.

"Based on the Department’s Nutrient and Dissolved Oxygen TMDLs for the Indian River Lagoon and Banana River Lagoon report (FDEP, 2009), the long-term annual average TN [Total Nitrogen] and TP [Total Phosphorous] loads entering the Indian River Lagoon system are about 1511 tons and 216 tons, respectively.  The 25 to 109 tons of TN and 2 to 7 tons of TP contributed by manatees only account for about 1.7% to 6.7% of TN loads and 0.7% to 3.0% of TP loads entering the Indian River Lagoon system."

"We have at least got [FDEP's] attention to the subject," Citizens for Florida's Waterways President Bob Atkins said of FDEP's analysis of the manatee's nutrient impact on the Indian River Lagoon.  "My conclusion is that seagrass loss is worse [from manatee consumption] than I have calculated and free nutrients are not as bad."


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