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Southeast Volusia Audubon Society, P.O. Box 46, New Smyrna Beach, FL 32170;   president@SEVolusiaAudubon.org


April 2016 Conservation Notes


IRL: Fish Kills and Root Causes

1)  Everything comes from somewhere.

2)  Everything has to go somewhere.

3)  There is no such thing as a free lunch.

    -Biology Professor, first day of class


fish kill and dumpsterMuck, aka “fine-grained, organic-rich sediments”, now covers much of the bottom of the 156 miles of the Indian River Lagoon (IRL). This muck, which in some navigational channels is up to 13-feet deep, is the color and consistency of “black mayonnaise” and is saturated with organo-phosphates and nitrogen compounds.  Heavy metals such as lead, zinc, copper, chromium and cadmium are often mixed in with this layer of sediment.  The muck has been built up by decades of runoff and overflow from human activities along the watershed of the IRL.   Core samples from the IRL show a pristine mix of sand and low-levels of organic silts until around the mid-1960s. Then, the muck begins to accumulate, aiding the establishment of those oxygen-robbing (anoxic) effects which create so much death in marine eco-systems that are dependent upon the stability of the normally-oxygenated waters of the IRL. The increase in water turbidity caused by muck that is unsettled by weather and water and human activities is also very injurious to marine life, especially the sea grasses.


A recent study, “Muck Thickness and Distribution in the Indian River Lagoon 2014” (Christopher Hoey) under the auspices of Florida Tech’s  Department of Marine and Environmental Systems, noted some of the key effects of muck and its continuing accumulation:

"Muck accumulation causes the depletion of sea grass directly through anoxia and smothering, and indirectly by fueling harmful algal blooms. Smothering and blooms shade grasses and prevent them from receiving sufficient light for photosynthesis. 49 percent of the [70] stations surveyed exhibited muck. Comparing muck thickness in navigation channels from 2008 to 2014 showed an average increase of 0.5 feet."

Several muck removal projects have been completed over the years, or are in-progress.  However, the present estimate of the amount of muck in the IRL is 135,000,000 cubic feet, the equivalent of a cube approximately 513 feet on each side.  Or, for a comparison, this is about 5.5 million cubic feet larger than the volume of the iconic Vehicle Assembly Building at the Kennedy Space Center, one of the largest buildings on Earth.

The 2014 muck study by Christopher Hoey also included a summation of the factors in the decline in the quality of the waters of the IRL:

"...The IRL exhibits a muddy to sandy benthos and is home to vegetation such as sea grass. In recent years the health of the lagoon has declined due to pollution, over fishing, invasive species, harmful algal blooms, and muck accumulation. Muck is mostly fine clay sediments with a high organic content. It accumulates in the IRL as a result of excess nutrients (nitrogen and phosphorus) runoff, and organic matter input. Muck is easily suspended in the water column, increasing turbidity. Settled muck rapidly goes anoxic and most benthic life cannot survive in muck impacted areas. Finally, muck can contribute excess nutrients to the water column and promote harmful algal blooms."


The March 2016 large-scale die-off of fish and other marine life along a 50-mile stretch of IRL shoreline  from Titusville southward was a direct result of a bloom of brown algae which was nourished by the  increased temperatures, existing layers of muck,  and  El Nino-related nutrient-rich January rains that were  three times normal.  The source of much of the added nutrients is fertilizer runoff from lawns and agricultural lands, and in equal measure, septic tanks.  This creates conditions in which the water of the IRL becomes a petri dish optimized for an algal bloom. 


These brown fogs of algae rob the water of oxygen, killing fish and marine invertebrates and killing or stressing seabed grasses.  These die-offs and reductions in food sources also affect manatees and birdlife.  As a result, these living beings also suffer reductions in reproductive success if not direct die-offs as a result of algal blooms.

Human-caused changes to the waters of the IRL are the root of this damage to the lifeforms that comprise the eco-systems of the Indian River Lagoon.  The overflow and leakage from 600,000 septic tanks (up from 300,000 in 2008) in the IRL watershed and the fertilizer from residential, commercial and agricultural uses in this watershed directly create these zones of death.  There is no other source.


The knowledge of the deleterious effects of septic systems and nutrient/sediment runoff in the IRL is not new.  Scientific studies that warned of human-caused quality issues in the waters and dependent eco-systems of the Indian River Lagoon have been the subject of many university and public symposia since the early 1980s.  Now is the time to apply solutions based in science rather than upon  political expediency and political ideologies that refuse the knowledge created through science. 


As a direct result of the recent massive fish kill, the political will to meet these problems is stirring in Brevard County.  There is a proposed County initiative to dredge the muck from IRL waters.  The cost of this effort is estimated at $200 million.  This money will only be well spent if plans truly address the root causes.  In addition to direct dredging of the accumulated muck, these plans and regulations could begin with a moratorium on any new septic systems and a buildout of existing sewage treatment systems (including artificial wetlands) to replace the huge number of septic systems in the IRL watershed.


We just need to recall the wisdom in this saying from the Cumberland Plateau:  “If a man made it, a man can fix it.” 


Lamont Ingalls

Conservation Chair