Septic system waste pervasive throughout Florida's Indian River lagoon


Date:
December 2, 2021
Source:
Florida Atlantic University
Summary:
There are more than 300,000 septic systems permitted in six counties
adjacent to the 156-mile-long Indian River Lagoon (IRL) in Florida.

Researchers assessed water quality and measured stable nitrogen
isotopes in groundwater, surface water, and macrophyte tissue
to identify nitrogen sources impacting the lagoon. Sucralose,
an artificial sweetener that is not completely broken down by
septic systems or wastewater treatment plants, was used as a human
wastewater tracer, and fecal indicator bacteria density was used
as an indicator of wastewater pollution.

Results showed that nitrogen enrichment of all sub-drainage basins
in this study supports that even 'properly functioning' septic
systems contribute nitrogen to surficial (shallow) groundwater.



FULL STORY ==========================================================================
For more than a decade, fertilizer leaching and associated stormwater
runoff were thought to be the major drivers of harmful algal blooms
in Florida's Indian River Lagoon. Despite the numerous residential
fertilizer ordinances passed since 2011, water quality, harmful algal
blooms, and seagrass loss, which has resulted in mass deaths of the
threatened Florida manatee, have continued to worsen.


========================================================================== There are more than 300,000 septic systems permitted in six counties
adjacent to the 156-mile-long Indian River Lagoon, which makes up 40
percent of Florida's eastern coast, and in Indian River and Martin
counties, septic systems represent more than 50 percent of wastewater
disposal. Five inlets allow the lagoon's waters to drain into the ocean, potentially impacting another important Florida ecosystem.

To determine if septic systems in Indian River County contribute to
nutrient enrichment of groundwaters and surface waters that discharge
into the central Indian River Lagoon, researchers from Florida Atlantic University's Harbor Branch Oceanographic Institute assessed water quality
at 20 sites in four Indian River County sub-drainage basins.

For the study, published in the journal Marine Pollution Bulletin,
they measured stable nitrogen isotopes in groundwater, surface water,
and macrophyte tissue to identify nitrogen sources impacting the Indian
River Lagoon.

Sucralose, an artificial sweetener that is not completely broken down
by septic systems or wastewater treatment plants, was used as a human wastewater tracer, and fecal indicator bacteria density was used as an indicator of wastewater pollution.

Results reveal that nitrogen enrichment of all sub-drainage basins in
this study supports that even "properly functioning" septic systems
contribute nitrogen to surficial (shallow) groundwater. Furthermore,
shallow ecosystems without a significant source of flushing and dilution,
such as the central Indian River Lagoon are more susceptible to inputs
from contaminated groundwater. Evidence shows that this issue is likely widespread in the Indian River Lagoon, including its canals, tributaries
and rivers.

Groundwater had significantly higher dissolved nutrient concentrations, nutrient ratios and more enriched stable nitrate isotopes than surface
waters, indicating septic system-enriched groundwater as a nitrogen
source to adjacent surface waters. This finding has implications for
nutrient loading and pollution, as submarine groundwater discharge is a
primary mechanism for nutrient and microbial transport to coastal waters.



========================================================================== Researchers found that enterococci and fecal coliform counts were
similar between all the drainage basins, indicating that bacterial
pollution is pervasive throughout the surface waters of the central
Indian River Lagoon.

Sucralose was found in surface waters throughout the study area
corroborating the elevated nitrogen concentrations, enriched stable
nitrogen isotope values and high surface water fecal indicator
bacteria, demonstrating that drainage systems in Indian River County
are contaminated by septic system waste.

"Humans are increasing nitrogen loading at unprecedented rates that
now exceed sustainability of the Earth's vital ecosystems," said Brian Lapointe, Ph.D., senior author and research professor, FAU Harbor
Branch. "Our study illustrates that implementing advanced wastewater
treatment or distributed wastewater (DWT) technologies in key locations
may allow for decreased nutrient loading and improved estuarine water
quality and seagrass health in the Indian River Lagoon and elsewhere
with similar conditions. Moreover, as sea level rise is expected to
further confound these issues in addition to more extreme and frequent
tropical storms and hurricanes, a better understanding of these dynamics
will be essential for sustainable management of coastal resources."
Findings from the study also support that Florida's sediments, such as
sandy soils and porous limestone, are not suitable for nutrient removal
by conventional septic systems, particularly in low-lying elevations
with seasonally high water tables.

"High seasonal water tables have been observed to reduce septic system functionality in many locations, including North Fort Myers, Jupiter,
and St.

George Island in Florida, southern Rhode Island and Ontario, Canada, reinforcing the geographical scope of these issues," said Rachel Brewton, corresponding author and research scientist, FAU Harbor Branch. "Florida
has both unsuitable soil types and high groundwater tables that combined
can result in septic system waste continuously flowing into groundwater, contaminating it with high levels of nutrients and fecal indicator
bacteria. This contamination ultimately discharges into surface waters
such as canals, rivers and estuaries contributing to water quality
degradation and harmful algal blooms." Researchers observed seasonal differences during the study. Generally, dissolved nutrient concentrations
in both groundwater and surface waters were higher in the wet season. This
is likely the result of increased infiltration, groundwater flow and
stormwater runoff in the wet season. Groundwater was less variable by
season than was surface water. The effects of septic systems on surface
waters in the four drainage basins, and ultimately the receiving waters
of the Indian River Lagoon, are exacerbated by eastward flow of the
surficial aquifer.

"Given the recent unprecedented harmful algal blooms and catastrophic
seagrass losses observed in this estuary, identifying specific
nutrient drivers is essential to inform restoration policies," said
Lapointe. "Importantly, our research supports similar findings in more temperate watersheds, confirming that septic systems near sensitive
aquatic ecosystems can promote increased harmful algal blooms through
nitrogen enrichment." Study co-authors are Laura Herren, a biological scientist, FAU Harbor Branch; Lynn Wilking, lab chemistry coordinator,
FAU Harbor Branch; Marie Tarnowski; and Margaret Vogel, Ph.D., a postdoc
at the University of Vienna.

This work was supported by the Save Our Seas specialty license plate fund administered through Harbor Branch Oceanographic Institute Foundation
(HBOIF) and the Florida Center for Coastal and Human Health, which was developed by and receives on-going support from grants provided by HBOIF.

========================================================================== Story Source: Materials provided by Florida_Atlantic_University. Original written by Gisele Galoustian. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. L.W. Herren, R.A. Brewton, L.E. Wilking, M.E. Tarnowski, M.A. Vogel,
B.E.

Lapointe. Septic systems drive nutrient enrichment of
groundwaters and eutrophication in the urbanized Indian River
Lagoon, Florida. Marine Pollution Bulletin, 2021; 172: 112928 DOI:
10.1016/ j.marpolbul.2021.112928 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/12/211202092944.htm

--- up 3 weeks, 2 hours, 55 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)