Maintaining Dissolved Oxygen Levels in Your Pond to Reduce Fish Kills

Maintaining Dissolved Oxygen Levels in Your Pond to Reduce Fish Kills

A father and his son fishing in a pond. Fishing, outdoor recreation. June 2010 IFAS Extension Calendar Image. UF/IFAS Photo by Tyler Jones.

Farm ponds are used in a number of different ways, including fishing, irrigation, water control, and wildlife viewing. UF/IFAS Photo by Tyler Jones.

Farm ponds of all shapes and sizes are common in rural Northwest Florida.  They are built for a number of reasons such as irrigation, water management, boating, fishing, wildlife viewing, livestock watering, and food production.  Each of these uses guides the way the pond is managed to maintain its function, as well as its ecological beauty, but a factor that is important to all uses is having enough oxygen!

As you have probably observed, your pond is a dynamic system, which is influenced literally from the ground up!  Much of the water’s basic chemical and physical characteristics reflect those of underlying soils (sand, clay, organic, etc.) and major sources of water (ground water, rainfall, runoff, etc.).  The pond’s characteristics also influence how much oxygen is available for use by the plants and animals that live in it.

Why is Dissolved Oxygen and Aeration so Important?


Fish kills are often the result of low dissolved oxygen levels and occur in both natural waters and man-made ponds. Photo by Vic Ramey.

The idea of oxygen being dissolved in water is a little counter-intuitive.  Especially to us, as air-breathing humans!  Think of your pond as a giant living, breathing organism.  Its atmosphere is the water itself, and it contains dissolved oxygen gas for the fish, aquatic plants, insects, and zooplankton to “breathe.”   Even bacteria need to breathe, and one of their fundamental roles in your pond is the decomposition of organic wastes like un-eaten fish food, and dead plant and animal materials.

Having enough dissolved oxygen in the water is one of the driving forces sustaining the health of your pond.  Oxygen is dissolved into water directly from the atmosphere, wind and wave action, and by plant photosynthesis.   Because warm water “holds” less dissolved oxygen than cold water, your pond’s dissolved oxygen levels can be lower in the summer than in the winter, especially in the early morning hours before plants begin to photosynthesize and produce oxygen.  While longer days and warmer temperatures mean more sunlight for plants to photosynthesize and produce oxygen, the demand or need for oxygen by fish, bacteria, and other aquatic organisms is also increased.  Periods of rainy, overcast days during the summer can greatly reduce oxygen production by plant photosynthesis.  Combined that with the increased oxygen demand by other organisms, and dissolved oxygen levels can drop fast.  These drops in dissolved oxygen levels often result in fish kills.  Productive, nutrient-rich ponds with high levels of organic materials, and a high fish density are at a greater risk of the devastating effects of low dissolved oxygen levels.

What Can You Do to Insure Your Pond Has Enough Oxygen? 

Do not be tempted to overfeed your fish. Feed them floating fish food so you can see how much they will consume in 10 to 15 minutes at each feeding.  Consider feeding them every other day.  In addition, as recommended in Managing Florida Ponds for Fishing do not feed them when the water temperature is below 60° F, or, above 95° F. Fish do not actively feed at these times.”   Use fish feeding behavior as your guide.  Uneaten food will only add excess organic matter to the pond.  The decomposition of this excess organic matter by bacteria increases the oxygen demand and likewise increases the chances of low oxygen levels and a fish kill.

Reduce nutrient inputs from runoff, livestock waste, excess fertilizer, and uneaten foods as described above, to help reduce the demand for oxygen in the system.  Additionally, remove as much excess debris as possible that may have been blown into your pond as a result of October’s Hurricane Michael that affected much of Florida’s panhandle.  Excess nutrients from these sources are freely available for use by hungry algae and other plants, which can then proliferate and, in turn, cause demand for more oxygen.  This increased demand for oxygen can cause fish kills due to low oxygen levels as described above.

If you have an aerator, keep it operative especially during extended periods of cloudy and rainy weather. Watch your fish for signs of oxygen stress (not eating, remaining near and gulping at the surface) and aerate accordingly.  Oxygen levels naturally fluctuate, and the lowest levels occur in the late evening through early morning hours when plants are not photosynthesizing and replenishing oxygen.  Therefore, most important time to routinely operate the aerator is the late overnight hours into early morning.

If you don’t have an aerator, consider purchasing one, especially as your pond ages and grows more fish, plants, and algae. It is certainly less costly in the end to be proactive when it comes to maintaining adequate dissolved oxygen in your pond.

Recreation and fishing are important uses of many rural farm ponds. Photo by UF/IFAS Tyler Jones.

What kind of Aerator should I get?

There are a few basic aerator types.  There are surface water agitators or fountains, and there are bottom air diffusers.  They can be powered by electricity, wind, or solar power.

Diffuser aerators can help achieve a uniform oxygen distribution in your pond from top to bottom.  This is especially important in deeper ponds (greater than 6-10 feet average depth) where temperature and oxygen stratification can occur.  Diffuser aerators pump surface air through the base sitting on the bottom of the pond causing bubbles of air to rise to the surface.  Diffusers also increase circulation and keep the deeper parts of your pond from becoming oxygen depleted.  In a new pond, or one with flocculent sediments, a diffuser may cause turbidity due to the physical action of the diffuser base sitting on the pond bottom circulating oxygen from the bottom to the surface.

Other aerator options are the fountain sprays or surface agitators that aerate surface water.  At a bare minimum, this can be a hose shooting water out over the water surface.  Surface fountains and agitators work well in small shallow ponds, but are generally not recommended for larger more productive ponds that need more oxygen.  In some commercial or farm ponds, paddle wheel agitators powered by a tractor’s pto are used during periods of low oxygen as an emergency measure when a fish kill is just beginning to occur.

Where Can I Purchase One?

The type or types of aerators you need for your pond will depend on the pond’s size, depth, level of productivity (nutrient level, number of fish), use, and water quality.  There are a number of shopping options online for pond aerators.  Try searching using the term “pond aerators Florida.”  Also, some local Panhandle fingerling fish farms sell these products too.  Here is a list of fish farms from the Florida Fish and Wildlife Conservation Commission: FWC Freshwater Fish Stocking List.   Additionally, there are dissolved oxygen meters you can purchase which accurately read the amount of oxygen in your ponds.  This is yet another tool to use in the overall management of your pond.

Simple surface agitators can be used to aerate small shallow ponds, but are generally not recommended for larger more productive ponds that need more oxygen. Photo by Judy Biss

More information about pond management can be found in the following references used for this article:
Overview of Florida Waters – Dissolved Oxygen
Clemson Cooperative Extension: Aeration, Circulation, and Fountains
Southern Regional Aquaculture Center: Pond Aeration
Managing Florida Ponds for Fishing
The Role of Aeration in Pond Management

Florida’s Water Quality Woes

Florida’s Water Quality Woes

Being in the panhandle of Florida you may, or may not, have heard about the water quality issues hindering the southern part of the state. Water discharged from Lake Okeechobee is full of nutrients.  These nutrients are coming from agriculture, unmaintained septic tanks, and developed landscaping – among other things.  The discharges that head east lead to the Indian River Lagoon and other Intracoastal Waterways.  Those heading west, head towards the estuaries of Sarasota Bay and Charlotte Harbor.

 

A large bloom of blue-green algae (cyanobacteria) in south Florida waters.
Photo: NOAA

Those heading east have created large algal blooms of blue-green algae (cyanobacteria). The blooms are so thick the water has become a slime green color and, in some locations, difficult to wade.  Some of developed skin rashes from contacting this water.  These algal blooms block needed sunlight for seagrasses, slow water movement, and in the evenings – decrease needed dissolved oxygen.  When the algae die, they begin to decompose – thus lower the dissolved oxygen and triggering fish kills.  It is a mess – both environmentally and economically.

 

On the west coast, there are red tides. These naturally occurring events happen most years in southwest Florida.  They form offshore and vary in intensity from year to year.  Some years beachcombers and fishermen barely notice them, other years it is difficult for people to walk the beaches.  This year is one of the worst in recent memories.  The increase in intensity is believed to be triggered by the increase in nutrient-filled waters being discharged towards their area.

Dead fish line the beaches of Panama City during a red tide event in the past.
Photo: Randy Robinson

On both coasts, the economic impact has been huge and the quality of life for local residents has diminished. Many are pointing the finger at the federal government who, through the Army Corp of Engineers, controls flow in the lake.  Others are pointing the finger at shortsighted state government, who have not done enough to provide a reserve to discharge this water, not enforced nutrient loads being discharged by those entities mentioned above.  Either way, it is a big problem that has been coming for some time.

 

As bad as all of this is, how does this impact us here in the Florida panhandle?

 

Though we are not seeing the impacts central and south Florida are currently experiencing, we are not without our nutrient discharge issues. Most of Florida’s world-class springs are in our part of the state.  In recent years, the water within these springs have seen an increase in nutrients.  This clouds the water, changing the ecology of these systems and has already affected glass bottom boat tours at some of the classic springs.  There has also been a decline in water entering the springs due to excessive withdrawals from neighboring communities.  The increase in nutrients are generally from the same sources as those affecting south Florida.

 

Florida’s springs are world famous. They attracted native Americans and settlers; as well as tourists and locals today.
Photo: Erik Lovestrand

Though we are not seeing large algal blooms in our local estuaries, there are some problems. St. Joe Bay has experienced some algal blooms, and a red tide event, in recent years that has forced the state to shorten the scallop season there – this obviously hurts the local economy.  Due to stormwater runoff issues and septic tanks maintenance problems, health advisories are being issued due to high fecal bacteria loads in the water.  Some locations in the Pensacola area have levels high enough that advisories must be issued 30% of the time they are sampled – some as often as 40%.  Health advisories obviously keep tourists out of those waterways and hurt neighboring businesses as well as lower the quality of life for those living there.

 

Then of course, there is the Apalachicola River issue. Here, water that normally flows from Georgia into the river, and eventually to the bay, has been held back for water needs in Georgia.  This has changed flow and salinity within the bay, which has altered the ecology of the system, and has negatively impacted one of the more successful seafood industries in the state.  The entire community of Apalachicola has felt the impact from the decision to hold the water back.  Though the impacts may not be as dramatic as those of our cousins in south Florida, we do have our problems.

Bay Scallop Argopecten iradians
http://myfwc.com/fishing/saltwater/recreational/bay-scallops/

What can we do about it?

 

The quick answer is reduce our nutrient input.

 

The state has adopted Best Management Practices (BMPs) for farmers and ranchers to help them reduce their impact on ground water and surface water contamination from their lands. Many panhandle farmers and ranchers are already implementing these BMPs and others can.  We encourage them to participate.  Read more at Florida’s Rangeland Agriculture and the Environment: A Natural Partnership http://nwdistrict.ifas.ufl.edu/nat/2015/07/18/floridas-rangeland-agriculture-and-the-environment-a-natural-partnership/.  

 

As development continues to increase across the state, and in the panhandle, sewage infrastructure is having trouble keeping up. This forces developments to use septic tanks.  Many of these septic systems are placed in low-lying areas or in soils where they should not be.  Others still are not being maintained property.  All of this leads to septic leaks and nutrients entering local waterways.  We would encourage local communities to work with new developments to be on municipal sewer lines, and the conversion of septic to sewer in as many existing septic systems as possible.  Read more at Maintaining Your Septic Tank http://nwdistrict.ifas.ufl.edu/nat/2017/04/29/maintain-your-septic-system-to-save-money-and-reduce-water-pollution/.

 

And then there are the lawns. We all enjoy nice looking lawns.  However, many of the landscaping plans include designs that encourage plants that need to be watered and fertilized frequently as well as elevations that encourage runoff from our properties.  Following the BMPs of the Florida Friendly Landscaping ProgramTM can help reduce the impact your lawn has on the nutrient loads of neighboring waterways.  Read more at Florida Friendly Yards – http://nwdistrict.ifas.ufl.edu/nat/2018/06/08/restoring-the-health-of-pensacola-bay-what-can-you-do-to-help-a-florida-friendly-yard/.

 

For those who have boats, there is the Clean Boater Program. This program gives advice on how boaters can reduce their impacts on local waterways.  Read more at Clean Boaterhttps://floridadep.gov/fco/cva/content/clean-boater-program.

 

One last snippet, those who live along the waterways themselves. There is a living shoreline program.  The idea is return your shoreline to a more natural state (similar to the concept of Florida Friendly LandscapingTM).  Doing so will reduce erosion of your property, enhance local fisheries, as well as reduce the amount of nutrients reaching the waterways from surrounding land.  Installing a living shoreline will take some help from your local extension office.  The state actually owns the land below the mean high tide line and, thus, you will need permission (a permit) to do so.  Like the principals of a Florida Friendly Yard, there are specific plants you should use and they should be planted in a specific zone.  Again, your county extension office can help with this.  Read more at The Benefits of a Living Shoreline http://nwdistrict.ifas.ufl.edu/nat/2017/10/06/the-benefits-of-a-living-shoreline/.

 

Though we may not be experiencing the dramatic problems that our friends in south Florida are currently experiencing, we do have our own problems here in the panhandle – and there is plenty we can do to keep the problems from getting worse. Please consider some of them.  You can always contact your local county extension office for more information.

Restoring the Health of Pensacola Bay, What Can You Do to Help?  – Fecal Bacteria

Restoring the Health of Pensacola Bay, What Can You Do to Help? – Fecal Bacteria

Of all the issues facing our local estuaries, high levels of fecal bacteria is the one that hinders commercial and recreational use the most. When bacteria levels increase and health advisories are issued, people become leery of swimming, paddling, or consuming seafood from these waterways.

Closed due to bacteria.
Photo: Rick O’Connor

I have been following the fecal bacteria situation in the Pensacola Bay system for several decades. Cheryl Bunch (Florida Department of Environmental Protection) has done an excellent job monitoring and reporting the bacteria levels, along with other parameters, for years – she has been fantastic.

 

The organisms used for monitoring have changed, so comparing numbers now and 30 years ago is somewhat difficult – but those changes came with good reason.

 

Fecal bacteria are organisms found in the large intestine of birds and mammals. They assist with digestion and are not a real threat to our health.  Understanding that both birds and mammals in and near our estuaries must defecate, it is understandable that some levels of these bacteria are in the waterways.  However, when levels are high there is a concern there are high levels of waste in the water.  This waste can carry other organisms that can cause health problems for humans – such as hepatitis and cholera.  So fecal bacteria monitoring is used as a proxy for other potential harmful organisms.  No one wants to swim in sewage.

E. coli is a classic proxy for this type of monitoring and has been used for years. Recently it was found that saline water could kill some of the fecal bacteria – giving monitors’ low readings in estuarine systems – suggesting that there is little sewage in the water – when in fact there may be high levels of sewage undetected. They have found Enterococcus a better proxy for marine waters, particularly Enterococcus faecalis. Researchers have determined that a single sample of bay water should have more than 35 colonies of Enterococcus (ENT).  If they find 35 or more colonies – a second sample is taken.  If the counts are again high – a health advisory will be issued.

 

Over the last 30 years of monitoring FDEP’s reports on the Pensacola Bay area – there have been patterns. Most of the “hot spots” have been bayous and locations where rivers are discharging into an estuary.  In addition, the periods of high fecal counts correspond well with periods of high rainfall.  Locally, in the Pensacola Bay area, sampling has been reduced due to budget issues and some bodies of water are not sampled as often as others.  Today both FDEP and the Florida Department of Health (FDOH) monitor and post their data via the Healthy Beaches Program.  In this program, the sample stations are commonly used swimming areas – meaning some other locations are rarely, if ever, sampled. Based on these data, 30-40% of the samples from local bayous annually require a health advisory to be issued.

 

Health advisories can reduce interest in human related recreation activities, such as wakeboarding, paddling, or even fishing – and certainly impacts interest in swimming. Decades ago, swimming and skiing were very popular in local bayous.  Today it is rare to see anyone doing so – most are motoring through heading to open bodies of water to spend their day.  It may also be effecting property purchases.  I have been contacted more than once with the question “would you buy on a house on XXX Bayou?”

 

Several local waterways are listed as impaired, and one is a BMAP area, due to high levels of bacteria. A BMAP (Basin Management Action Plan – read more at the link below) is a state designated body of water that is impaired (for some reason) and is required to make annual improvements to reduce the problem.

The spherical cells of the “coccus” bacteria Enterococcus.
Photo: National Institute of Health

 

So What Can We Do to Reduce This Problem?

 

In the Pensacola area, both the city and county have made efforts to modify and improve stormwater problems. Baffle boxes in east Pensacola have helped to reduce the amount of runoff entering the bayous and bays, thus reducing the frequency health advisories are being issued.  That said, during heavy events the counts still increase – and rainfall seems to be increasing in the area in recent years.  We will continue to monitor the frequency of advisories and post these on Sea Grant Notes through the Escambia County extension office each week.

 

From our side of the story (you and me) – anything you can do to reduce runoff will certainly help. Florida Friendly Landscaping techniques are a good start (see article on FFL posted below).  Clean up after your pet, both in your yard and after walks – most people do… but not all.  Septic systems have been a point of concern.  If you have a septic system, maintain it (see article below on how).  If the opportunity presents itself, you can move from septic to a sewer system.  At many public places along the waterfront have signs asking everyone not to feed the birds.  Congregating birds equals congregating bird feces and this can be a health issue.

 

Local and state governments are working to reduce the stormwater impacts on our local estuaries – which trigger other problems as well as high bacteria counts. Local residents and businesses can do the same.

 

 

References

 

Lewis, M.J., J.T. Kirschenfeld, T. Goodhart. 2016. Environmental Quality of the Pensacola Bay System: Retrospective Review for Future Resource Management and Rehabilitation. U.S. Environmental Protection Agency.  Gulf Breeze FL. EPA/600/R-16/169.

 

BMAP

https://floridadep.gov/dear/water-quality-restoration/content/basin-management-action-plans-bmaps.

 

Florida Friendly Landscaping

Restoring the Health of Pensacola Bay, What You Can Do to Help? – Florida Friendly Landscaping

http://blogs.ifas.ufl.edu/escambiaco/2018/06/08/restoring-the-health-of-pensacola-bay-what-can-you-do-to-help-a-florida-friendly-yard/.

 

Septic Systems

Maintain Your Septic Tank System to Save Money and Reduce Water Pollution

http://nwdistrict.ifas.ufl.edu/nat/2017/04/29/maintain-your-septic-system-to-save-money-and-reduce-water-pollution/.

 

Septic Tanks: What You Should Do When a Flood Occurs

http://nwdistrict.ifas.ufl.edu/nat/2018/05/04/septic-systems-what-should-you-do-when-a-flood-occurs/.

Restoring the Health of Pensacola Bay, What Can You Do to Help?  – Mercury and Public Health

Restoring the Health of Pensacola Bay, What Can You Do to Help? – Mercury and Public Health

Shrimp, oysters, blue crab and fish have been harvested from the Pensacola Bay System (PBS) for decades, although there has been a decline in all in recent years. Annual landings (in pounds) have ranged from

  • Fish                        66,000 – 4,600,000   (most are scaienids)
  • Brown shrimp    43,000 – 906,000
  • Oysters                0 – 492,000
  • Blue crab             400 – 137,000

There is a concern about the safety of seafood harvested from our estuary… sort of. Many local residents and visitors ask frequently about the safety of these products.  However, when programs are held to provide this information they are not well attended, and when articles are posted – few view them.  I think there is a concern for the safety of seafood products, particularly those from our estuaries – so I cannot explain the lack of interest in the presentations and articles.

Commercial seafood in Pensacola has a long history.
Photo: Rick O’Connor

One contaminant that gets a lot of press is mercury. The toxic form of mercury is methylmercury.  This form of mercury impairs brain development of fetuses – hearing, vision, and muscle function in adults.  Studies suggests that the primary source of mercury in the waters of the PBS is the atmosphere.  Advisories have been issued for Escambia, Blackwater, and Yellow Rivers.  There have also been advisories for local largemouth and king mackerel.  This is one of the metals whose concentrations within the PBS is higher than neighboring estuaries – especially in our bayous (see https://blogs.ifas.ufl.edu/escambiaco/2018/06/13/restoring-the-health-of-pensacola-bay-what-can-you-do-to-help-bioaccumulation-of-toxins/.) Florida Department of Environmental Protection (FDEP) has issued Total Maximum Daily Loads (TDMLs) for mercury in the PBS.

 

So How Much is Too Much?

 

For monitoring purposes, total mercury (THg) is easier and less expensive to than the toxic form methylmercury (MHg). Many believe the amount of THg is equivalent to the concentration of MHg, and so it is used as a proxy for MHg.

 

Both the U.S. EPA and the FDEP recommend concentrations of THg not be higher than 0.3 ppm, and 0.1 ppm for pregnant women (or women planning a pregnancy).

 

Fish

Since 2000, four studies have been conducted on six species of fish in the PBS. Concentrations of THg ranged from 0.02 – 0.88 ppm and averaged between 0.2 – 0.4 ppm.

 

Blue Crab

Two studies have been conducted since 2007 found mercury concentrations ranged from 0.07 – 1.1 ppm.

 

Oysters

30 years ago, studies were finding concentrations of THg in oysters around 0.02 ppm. Repeated studies between 1986 and 1996 found an increase to 0.3 ppm.

 

Overall

Studies suggest that shrimp and oysters have lower concentrations of THg than blue crab and fish.

 

Seafood has a long history along Florida’s panhandle.
Photo: Betsy Walker

How often have samples exceeded the safe levels suggested by EPA, FDEP, and FDA?

 

Group Recommended highest level % of times samples from PBS exceeded this limit
Subsistence Fishermen 0.049 ppm 50-90%

(89% for blue crab and oysters)

Pregnant females 0.1 ppm 50-90%

(88% for blue crab)

General public 0.3 ppm 5-20%

(12% for blue crabs)

(27% for fish)

Food and Drug Administration recommendation 1.0 ppm 0%

 

The concern for mercury in local seafood has led to a reduction of consuming all seafood by pregnant women – period. Recent studies have shown this can have negative effects on the developing baby as well.  The recommendation is to avoid fish that have been tested high in THg.  Most of these are high on the food chain – such as king mackerel, shark, and swordfish.  You can find the latest on seafood safety and advisories at https://myescambia.com/our-services/natural-resources-management/marine-resources/seafood-safety. Another piece of this story is the belief, by many, that selenium can lower the toxicity of MHg.  Many believe that molar ratios of selenium and mercury greater than 1.0 can reduce the toxicity.  However, there have been no studies on molar ratios of these elements in the PBS.

 

The bottom line on this issue is to be selective on the seafood products you consume.

The most popular seafood species – shrimp.

 

Reference

 

Lewis, M.J., J.T. Kirschenfeld, T. Goodhart. 2016. Environmental Quality of the Pensacola Bay System: Retrospective Review for Future Resource Management and Rehabilitation. U.S. Environmental Protection Agency.  Gulf Breeze FL. EPA/600/R-16/169.

Restoring the Health of Pensacola Bay, What Can You Do to Help?  – Bioaccumulation of Toxins

Restoring the Health of Pensacola Bay, What Can You Do to Help? – Bioaccumulation of Toxins

What is bioaccumulation of toxins?

 

Our bodies come in contact, and produce, toxins every day. The production of toxins can result during simple metabolism of food.  However, our bodies are designed with a system to rid us of these toxins.  Toxins are processed by our immune system and removed via our kidneys.  Some chemical compounds are structured in a way that they are not as easily removed, thus they accumulate in our bodies over time, often in fatty tissues, and sometimes they are toxic – this is bioaccumulation.

A view of Pensacola Bay from Santa Rosa Island.
Photo: Rick O’Connor

Biomagnification takes it a step further. In many cases, the concentrations of bioaccumulating toxic substances in the water may be in low enough concentrations to have little effect on human health.  They are ingested by small organisms in the environment, such as plankton or juvenile marine fish, and – again are at low concentrations.  However, they are accumulated in their tissues and as the next level of the food chain begin to consume them – they too accumulate the toxic compounds in their tissues.  Small fish consume large amounts of plankton and thus, large amounts of the toxins they have accumulated – increasing the concentration within their own tissues.  This continues up the food chain to a point where, in the larger predators, the concentrations of these toxins have increased enough that they now pose a threat to human health – this is biomagnification.

 

The presence, and amount, of any one bioaccumulating compound varies with species, their size, their age, their gender, their life stage, whether they are mobile or not, their diet, and whether the sample included the skin (which is lipid heavy and a common location for accumulated toxins). In the Pensacola Bay System, about 30 species of marine plants and animals have been analyzed for the presence of these accumulating compounds.

 

Species collected from Pensacola Bay that were analyzed for contaminants

Plants 3 species of seagrass

1 species of seaweed

Colonized algal periphyton

Invertebrates 4 species of freshwater mussels

Eastern oyster

1 species of brackish water clams

1 species of barnacle

Several species of shrimp

Blue crab

Oyster drill (snail)

Vertebrates 2 species of catfish

5 species of scaienids (drums, croakers, trout)

Bluegill

Bluefish

Several species of flounder

2 species of jacks

Largemouth bass

Sheepshead

Striped mullet

 

Trace Metal Accumulation

Much of what has been studied in terms of metal accumulation has come from shellfish – particularly eastern oysters. Ten different metals have been found in oysters with zinc being in the highest concentration and lead the lowest.  A 2005 study found that levels of arsenic, lead, and nickel collected from mussels collected at selected locations in the PBS were regionally high (meaning higher than other estuaries in the region).  Another study (2003) found that levels of 16 different metals in shellfish were three times higher in Bayou Chico than samples from East Bay.  A 1993 study found that organisms attached to pieces of treated wood in Santa Rosa Sound had elevated levels of metals.  However, another study (2008) found low concentrations of metals in five species of fish collected in Escambia Bay near the I-10 Bridge.

 

The bioaccumulation potential within plants is less understood than animals. That said – concentrations within seagrass were relatively low when compared to the sediments they were growing in and periphytic algae attached to them.

 

Total Mercury Concentrations (ng/g – dry weight) for Local Marine Organisms

Lewis and Chaney (2008)

Range (ng/g) Species
0-200 Sediments, seagrass, oysters
200 – 400 Periphytic algae
400 – 600 Mussels
600 – 800 Brackish clams, blue crabs
800 and higher Fish

 

The above table shows biomagnification.

 

Comparing trace metal concentrations between Pensacola Bay and other Regional Estuaries

(USEPA unpublished data)

Pensacola Bay, Escambia Bay, Escambia River, Bayou Texar, Bayou Chico, Bayou Grande, Santa Rosa Sound Grand Lagoon (Bay Co.), Mississippi Sound, Old River, Suwannee River, Withlacoochee River, Bay La Launch
Cadmium Higher in PBS; highest in Bayou’s Grande and Texar
Chromium Similar to other estuaries
Copper Slightly elevated in Bayou Chico and Escambia River; highest in Withlacoochee
Total Mercury Much higher in PBS; particularly in the bayous
Nickel Lower in PBS
Lead Higher in PBS; particularly in the bayous
Zinc Higher in PBS; particularly in the bayous

 

There are higher concentrations of trace metals in PBS and particularly in the bayous.

 

One of 39 stormwater drains into Bayou Texar.
Photo: Rick O’Connor

Non-Nutrient Organic Chemicals

These are compounds such as PCBs, DDT, and PAHs; many are actually families of multiple forms of compounds. Information on the bioaccumulation of these compounds in PBS is less common than those of trace metals.  However, this information is important since they have long half-lives and magnify within the food web.

 

That said – there are studies on these compounds that go back to the 1970’s. They looked at DDT, pesticides, and PAHs in oysters and croakers.  One study (1986-96) found DDT concentrations in oysters at 60 ppb or less.  A follow up study (2004-05) at those same locations found concentrations between 8-20 ppb.  One study (2008) found the order of accumulating non-nutrient organic compounds with PAHs as the highest and dieldrin at the lowest.  Downward trends were reported (2004-05) for many of these compounds including PAHs and PCBs.

 

Some of these compounds have entered the PBS via unlined ponds associated with on-land Superfund sites. Creosote and pentachlorophenol were stored for years in such ponds and have leached into area waters such as Bayou Chico and portions of upper Pensacola Bay.  A study (1987-88) found oyster drills sampled in these areas had concentrations 10x higher than reference sites in other parts of the PBS.

 

So what can we do about this?

 

The compounds that are there – are there. Many of these trace metals are heavy and sink into the sediments.  There occurrence within the food web has decreased over time and some have suggested the safest thing to do is to leave them where they are.  No doubt, any project requiring sediment movement requires much review and permitting.

To try to remove these compounds would be extremely expensive – hence the Superfund Program. So if we cannot clean the sediments without a lot of labor and money, can we reduce the amount that enters the bay today?

Many of these compounds come from industrial processing of products we really want or need. Reduction of the production of some will be difficult, but there is much industry can do to reduce the chance of those compounds reaching our estuaries – and they are doing this.  Point source pollution (direct discharge from an industry) has reduced significantly since the 1970’s.  Non-point sources (indirect discharge from you and I) is still a problem.  We can choose products that contain less (or none) of the compounds we discussed.  Following an IPM program for dealing with household and lawn pests (see article on Florida Friendly Yards – https://blogs.ifas.ufl.edu/escambiaco/2018/06/08/restoring-the-health-of-pensacola-bay-what-can-you-do-to-help-a-florida-friendly-yard/) can help a lot.  As can practices that reduce the amount of run-off reaching our bays.  Reducing your use of lawn watering, using rain barrels, or rain gardens, and planting living shorelines (all mentioned in the FFY article) can certainly help.

 

Reference

 

Lewis, M.J., J.T. Kirschenfeld, T. Goodhart. 2016. Environmental Quality of the Pensacola Bay System: Retrospective Review for Future Resource Management and Rehabilitation. U.S. Environmental Protection Agency.  Gulf Breeze FL. EPA/600/R-16/169.

Hurricanes and floods: Meeting the resource needs of private well owners

Flooding along the South Prong of the Black Creek River in Clay County on September 13, 2017. Photo credit: Tim Donovan, Florida Fish and Wildlife Conservation Commission (FWC).

As hurricane season is upon us again, I wanted to share the results of work that UF/IFAS Extension staff did with collaborators from Virginia Tech and Texas A&M University to help private well owners impacted by Hurricanes Irma and Harvey last year. This work highlights just how important it is to be prepared for this year’s hurricane season and to make sure that if flooding does occur, those that depend on private wells for household use take the proper precautions to ensure the safety of their drinking water.

About 2.5 million Floridians (approximately 12% of the population) rely on private wells for home consumption. While public water systems are regulated by the U.S. Environmental Protection Agency to ensure safe drinking water, private wells are not regulated. Private well users are responsible for ensuring the safety of their own water.

Hurricanes Irma and Harvey

In response to widespread damage and flooding caused by Hurricane Harvey in Texas and Irma in Florida in August and September 2017, Virginia Polytechnic Institute and State University (VT) received a Rapid Research Response Grant from the National Science Foundation to offer free well water testing to homeowners impacted by flooding.

They partnered with Texas A&M AgriLife Extension’s Well Owner Network (run by Diane Boellstorff and Drew Gholson) and us, at UF/IFAS Extension to provide this service. The effort at VT was led by members of Marc Edward’s lab in the Civil Engineering Department: Kelsey Pieper, Kristine Mapili, William Rhoads, and Greg House.

VT made 1,200 sampling kits available in Texas and 500 in Florida, and offered free analysis for total coliform bacteria and E. coli as well as other parameters, including nitrate, lead, arsenic, iron, chloride, sodium, manganese, copper, fluoride, sulfate, and hardness (calcium and magnesium). Homeowners were also asked to complete a needs assessment questionnaire regarding their well system characteristics, knowledge of proper maintenance and testing, perceptions of the safety of their water and how to best engage them in future outreach and education efforts.

Response in the aftermath of Irma

Although the sampling kits were available, a major challenge in the wake of Irma was getting the word out as counties were just beginning to assess damage and many areas were without power. We coordinated the sampling effort out of Quincy, Florida, where I am based, and spread the word to extension agents in the rest of the state primarily through a group texting app, by telephone and by word of mouth. Extension agents in 6 affected counties (Lee, Pasco, Sarasota, Marion, Clay and Putnam) responded with a need for sample kits, and they in turn advertised sampling to their residents through press releases.

Residents picked up sampling kits and returned water samples and surveys on specified days and the samples were shipped overnight and analyzed at VT, in Blacksburg, VA. Anyone from nearby counties was welcome to submit samples as well. This effort complemented free well water sampling offered by multiple county health departments throughout the state.

In all, 179 water samples from Florida were analyzed at VT and results of the bacterial analysis are shown in the table below. Of 154 valid samples, 58 (38%) tested positive for total coliform bacteria, and 3 (2%) tested positive for E. coli. Results of the inorganic parameters and the needs assessment questionnaire are still being analyzed.

Table 1. Bacterial analysis of private wells in Florida after Hurricane Irma.

County Number of samples (n) Positive for total coliform (n) Positive total coliform (%) Positive for E. coli (n) Positive for E. coli (%)
Citrus 1 0 0% 0 0%
Clay 13 5 38% 0 0%
Hernando 2 1 50% 0 0%
Hillsborough 1 1 100% 0 0%
Marion 19 5 26% 1 5%
Monroe 1 0 0% 0 0%
Pasco 40 19 48% 1 3%
Putnam 61 19 31% 0 0%
Sarasota 16 8 50% 1 6%
Overall 154 58 38% 3 2%

Of 630 samples analyzed in Texas over the course of 7 weeks post-Hurricane Harvey, 293 samples (47% of wells) tested positive for total coliform bacteria and 75 samples (2%) tested positive for E. coli.

What to do if pathogens are found

Following Florida Department of Health (FDOH) guidelines, we recommended well disinfection to residents whose samples tested positive for total coliform bacteria, or both total coliform and E. coli. This is generally done through shock chlorination by either hiring a well operator or by doing it yourself. The FDOH website provides information on potential contaminants, how to shock chlorinate a well and how to maintain your well to ensure the quality of your well water (http://www.floridahealth.gov/environmental-health/private-well-testing/index.html).

UF/IFAS extension agents that led the sampling efforts in their respective counties were: Roy Beckford – Lee County; Brad Burbaugh – Clay County; Whitney Elmore – Pasco County; Sharon Treen – Putnam and Flagler Counties; Abbey Tyrna – Sarasota County and Yilin Zhuang – Marion County.

We at IFAS Extension are working on using results from this sampling effort and the needs assessment questionnaire filled out by residents to develop the UF/IFAS Florida Well Owner Network. Our goal is to provide residents with educational materials and classes to address gaps in knowledge regarding well maintenance, the importance of testing and recommended treatments when pathogens and other contaminants are present.

Remember: Get your well water tested if flooding occurs

It’s important to remember that if any flooding occurs on your property that affects your well and/or septic system, you should have your well water tested in a certified laboratory for pathogens (total coliform bacteria and E. coli) and any other parameters your local health department may recommend.

Most county health departments accept samples for water testing. You can also submit samples to a certified commercial lab near you. Contact your county health department for information about what to have your water tested for and how to take and submit the sample.

Contact information for county health departments can be found online at: http://www.floridahealth.gov/programs-and-services/county-health-departments/find-a-county-health-department/index.html

You can search for laboratories near you certified by FDOH here: https://fldeploc.dep.state.fl.us/aams/loc_search.asp This includes county health department labs as well as commercial labs, university labs and others.

You should also have your well water tested at any time when:

  • The color, taste or odor of your well water changes or if you suspect that someone became sick after drinking your well water
  • A new well is drilled or if you have had maintenance done on your existing well

Testing well water once a year is good practice to ensure the safety of your household’s drinking water.