Item L2C ounty of M onroe
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BOARD OF COUNTY COMMISSIONERS
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Mayor David Rice, District 4
The FlOnda Key
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Mayor Pro Tem Sylvia J. Murphy, District 5
Danny L. Kolhage, District 1
George Neugent, District 2
Heather Carruthers, District 3
County Commission Meeting
July 18, 2018
Agenda Item Number: L.2
Agenda Item Summary #4454
BULK ITEM: No DEPARTMENT: BOCC District 2
TIME APPROXIMATE: STAFF CONTACT: Terri Colonna (305) 292 -4512
10:30 A.M.
AGENDA ITEM WORDING: Presentation and discussion with Dr. Steve Davis or Dr. Tom Van
Lent concerning canals that are exhibiting signs of reduced dissolved Oxygen due to debris from
Hurricane Irma. It appears to be causing horrific effects to canal and near -shore water quality.
ITEM BACKGROUND:
PREVIOUS RELEVANT BOCC ACTION:
CONTRACT /AGREEMENT CHANGES:
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STAFF RECOMMENDATION:
DOCUMENTATION:
6 -25 -18 Memo to Commissioner George Nugent
FINANCIAL IMPACT:
Effective Date:
Expiration Date:
Total Dollar Value of Contract:
Total Cost to County:
Current Year Portion:
Budgeted:
Source of Funds:
CPI:
Indirect Costs:
Estimated Ongoing Costs Not Included in above dollar amounts:
Revenue Producing:
Grant:
County Match:
Insurance Required:
Additional Details:
If yes, amount:
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REVIEWED BY:
Kathy Peters Completed 07/03/2018 3:31 PM
Board of County Commissioners Pending 07/18/2018 9:00 AM
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MEMORANDUM
TO: Commissioner George Neugent, Monroe County, Florida
FROM: Eric Eikenberg, CEO
SUBJECT: Florida Keys canal water quality concern
DATE: June 25, 2018
In September 2017, Hurricane Irma battered the Florida Keys and left behind enormous piles of
debris, including houses, boats, appliances and vegetation. While more than 2 million cubic yards
of this has been collected from land and hauled away, a substantial amount of material remains at
the bottom of the numerous canals throughout the Keys. Much of this debris is likely organic (i.e.,
wood /timber, leaves etc.) that is in varying states of decay. As we move into the warmer summer
months and this material continues to decompose under increasingly anaerobic conditions, a
potential health threat exists to aquatic organisms as well as residents along these waterways.
Our scientists have heard recent accounts of fish kills and degraded water quality in multiple
canals along the middle and upper Florida Keys. The former is not abnormal, especially in warm
summer months when small topwater fish are vulnerable to hypoxic conditions (i.e., a lack of
oxygen), as warmer saline water loses its capacity to hold oxygen. However, with the impact of
Hurricane Irma last summer in generating a substantial amount of debris that was deposited into
the canals, recent accounts of changes in the smell and color of water in some canals is cause for
concern and warrant rapid monitoring of conditions that may affect human health. The water
quality parameter of primary concern is hydrogen sulfide, a smelly, highly toxic gas that is
produced through anaerobic respiration in the presence of sulfate.
A property owner along an oceanside canal between mile marker 87 and 89, shared the photo
below (taken June 22, 2018) with one of our scientists and described the following condition:
"Any idea why we are having a fish kill Oceanside mm87 -89? I saw it yesterday. Rancid.
Smelly. Toxic. Also purple -like grassy substance all over the shoreline. Took some photos
but not sure they fully show extent of the nasty. Please don't tell me it's hot weather a low
current or lack of oxygen. Folks around here who've been here forever don't recall ever
witnessing this."
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Without having visited the scene firsthand, our scientists believe that the "grassy" substance this
resident is describing could be Beggiatoa, a filamentous sulfide oxidizing bacteria.
Beggiatoa grows in extreme marine /coastal habitats where there is an abundance of hydrogen
sulfide, as do purple - sulfur bacteria, which also thrive on sulfide (as an energy source) and may
account for the colors observed in the water ranging from purple to brown /orange.
Knowing that Hurricane Irma deposited a huge amount of organic debris in Florida Keys canals,
this is likely the cause of the recent and noticeable change in water quality in this canal and likely
many others along the Keys. As many of these canals are poorly - flushed by tides, dredging and
debris removal in addition to aeration may help to mitigate these impacts in the long -term.
However, in the short -term, dredging in the warm summer month may exacerbate the timing and
nature of this kind of water quality change in canals, although every canal is different and the
amount of organic matter deposited into each likely varied. This is where monitoring information
will help.
To understand exactly what is likely happening in these canals, it may help to recall what
happened in Florida Bay with the seagrass die -off in the summer of 2015 and the algal blooms that
have plagued the bay since. Similar to that seagrass die -off and the immediate amount of dead
biomass it created, Irma produced a substantial volume of organic matter that was introduced into
the canals and has been slowly decaying, consuming oxygen and releasing nutrients since last
summer.
In the presence of saltwater, which is high in sulfate, organic matter decaying in ever - warming
water can tip the balance of the canal environment towards an anaerobic system dominated by
sulfate reduction. This often occurs overnight when photosynthesis is not contributing to oxygen
production in canal water. An end - product of sulfate reduction is hydrogen sulfide, which
produces the rotten egg smell that many people are familiar with in coastal wetlands. Perhaps, in
the case of the canal in the attached photo, there is such an abundance of hydrogen sulfide that
has accumulated in the canals (i.e., that can't be flushed out easily) that it is creating a new
environment for sulfide - loving organisms to thrive.
This is potentially hazardous to residents, pets and aquatic organisms ranging from manatees to
recreationally important fish species. As a safety precaution, people SHOULD NOT get in the water
of canals such as this in the attached photo until there is an understanding of whether the
hydrogen sulfide levels are safe enough for exposure. We suspect that other canals along the Keys
will be showing these same state changes and perhaps turning color as the summer progresses. If
Irma - generated debris has not yet been sufficiently cleared, conditions in these canals may get
worse in the traditionally hotter months of July and August.
Everglades Foundation scientists are happy to provide expertise and advice should Monroe County
officials have any questions or requests for more information.
Dr. Tom Van Lent tvanlenteverladesfoundation .org 305 - 304 -9906 (mobile)
Dr. Stephen Davis sdaviseverladesfoundation . org 979 - 571 -4739 (mobile)
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