by Rick O'Connor | Jun 22, 2018
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.
by Rick O'Connor | Jun 8, 2018
We have been posting articles discussing some of the issues our estuaries are facing; this post will focus on one of the things you can do to help reduce the problem – a Florida Friendly Yard.
Florida Friendly Landscaping saves money and reduces our impact on the estuarine environment.
Photo: UF IFAS
The University of Florida IFAS developed the Florida Friendly Landscaping Program. It was developed to be included in the Florida Yards & Neighborhoods (FYN) program, HomeOwner and FYN Builder and Developer programs, and the Florida-Friendly Best Management Practices for Protection of Water Resources by the Green Industries (GI-BMP) Program in 2008.
A Florida Friendly Yard is based on nine principals that can both reduce your impact on local water quality but also save you money. Those nine principals are:
- Right Plant, Right Place – We recommend that you use native plants in the right location whenever possible. Native plants require little fertilizer, water, or pesticides to maintain them. This not only reduces the chance of these chemicals entering our waterways but also saves you money. The first step in this process is to have your soil tested at your local extension office. Once your soil chemistry is known, extension agents can do a better job recommending native plants for you.
- Water Efficiently – Many homeowners in the Florida panhandle have irrigation systems on timers. This makes sense from a management point of view but can lead to unnecessary runoff and higher water bills. We have all seen sprinkler systems operating during rain events – watering at that time certainly is not needed. FFY recommends you water only when your plants show signs of wilting, water during the cooler times of day to reduce evaporation of your resource, and check system for leaks periodically. Again, this helps our estuaries and saves you money.
- Fertilize Appropriately – No doubt, plants need fertilizer. Water, sunlight, and carbon dioxide produce the needed energy for plants to grow, but it does not provide all of the nutrients needed to create new cells – fertilizers provide needed those nutrients. However, plants – like all creatures – can only consume so much before the remainder is waste. This is the case with fertilizers. Fertilizer that is not taken up by the plant will wash away and eventually end up in a local waterway where it can contribute to eutrophication, hypoxia, and possible fish kills. Apply fertilizers according to UF/IFAS recommendations. Never fertilize before a heavy rain.
- Mulch – In a natural setting, leaf litter remains on the forest floor. The environment and microbes, recycling needed nutrients within the system, break down these leaves. They also reduce the evaporation of needed moisture in the soil. FFY recommends a 2-3” layer of mulch in your landscape.
- Attract Wildlife – Native plants provide habitat for a variety of local wildlife. Birds, butterflies, and other creatures benefit from a Florida Friendly Yard. Choose plants with fruits and berries to attract birds and pollinators. This not only helps maintain their populations but you will find enjoyment watching them in your yard.
- Manage Yard Pests Responsibly – This is a toughie. Once you have invested in your yard, you do not want insect, or fungal, pests to consume it. There is a program called the Integrated Pest Management Program (IPM) that is recommended to help protect your lawn. The flow of the program basically begins with the least toxic form of pest management and moves down the line. Hopefully, there will not be a need for strong toxic chemicals. Your local county extension office can assist you with implementing an IPM program.
- Recycle – Return valuable nutrients to the soil and reduce waste that can enter our waterways by composting your turfgrass clippings, raked leaves, and pruned plants.
- Reduce Stormwater Runoff – ‘All drains lead to the sea’ – this line from Finding Nemo is, for the most part, true. Any water leaving your property will most likely end in a local waterway, and eventually the estuary. Rain barrels can be connected to rain gutters to collect rainwater. This water can be used for irrigating your landscape. I know of one family who used it to wash their clothes. Rain barrels must be maintained properly to not produce swarms of mosquitos, and your local extension office can provide you tips on how to do this. More costly and labor intensive, but can actually enhance your yard, are rain gardens. Modifying your landscape so that the rainwater flows into low areas where water tolerant plants grow not only reduces runoff but also provides a chance to grow beautiful plants and enhance some local wildlife.
- Protect the Waterfront – For those who live on a waterway, a living shoreline is a great way to reduce your impact on poor water quality. Living shorelines reduce erosion, remove pollutants, and enhance fisheries – all good. A living shoreline is basically restoring your shoreline to a natural vegetative state. You can design this so that you still have water access but at the same time help reduce storm water runoff issues. Planting below the mean high tide line will require a permit from the Florida Department of Environmental Protection, since the state owns that land, and it could require a breakwater just offshore to help protect those plants while they are becoming established. If you have questions about what type of living shoreline you need, and how to navigate the permit process, contact your local county extension office.
Santa Rosa Sound
Photo: Dr. Matt Deitch
These nine principals of a Florida Friendly Yard, if used, will go a long way in reducing our communities’ impact on the water and soil quality in our local waterways. Read more at http://fyn.ifas.ufl.edu/about.htm.
by Rick O'Connor | May 31, 2018
It is now late May and in recent weeks I, and several volunteers, have been surveying the area for terrapins, horseshoe crabs, and monitoring local seagrass beds. We see many creatures when we are out and about; one that has been quite common all over the bay has been the “stingray”.
The cownose ray is often mistaken for the manta ray. It lacks the palps (“horns”) found on the manta.
Photo: Florida Sea Grant
These are intimidating creatures… everyone knows how they can inflict a painful wound using the spine in their tail, but may are not aware that not all “stingrays” can actually use a spine to drive you off – actually, not all “rays” are “stingrays”.
So what is a ray?
First, they are fish – but differ from most fish in that they lack a bony skeleton. Rather it is cartilaginous, which makes them close cousins of the sharks.
So what is the difference between a shark and a ray?
You would immediately jump on the fact that rays are flat disked-shape fish, and that sharks are more tube-shaped and fish like. This is probably true in most cases, but not all. The characteristics that separate the two groups are
- The five gill slits of a shark are on the side of the head – they are on the ventral side (underside) of a ray
- The pectoral fin begins behind the gill slits in sharks, in front of for the ray group
Not all rays have the whip-like tail that possess a sharp spine; some in fact have a tube-shaped body with a well-developed caudal fin for a tail.
There are eight families and 19 species of rays found in the Gulf of Mexico. Some are not common, but others are very much so.
Sawfish are large tube-shaped rays with a well-developed caudal fin. They are easily recognized by their large rostrum possessing “teeth” giving them their common name. Walking the halls of Sacred Heart Hospital in Pensacola, you will see photos of fishermen posing next to monsters they have captured. Sawfish can reach lengths of 18 feet… truly intimidating. However, they are very slow and lethargic fish. They spend their lives in estuaries, rarely going deeper than 30 feet. They were easy targets for fishermen who displayed them as if they caught a true monster. Today they are difficult to find and are protected. There are still sightings in southwest Florida, and reports from our area, but I have never seen one here. I sure hope to one day. There are two species in the Gulf of Mexico.
Guitarfish are tube-shaped rays that are very elongated. They appear to be sharks, albeit their heads are pretty flat. They more common in the Gulf than the bay and, at times, will congregate near our reefs and fishing piers to breed. They are often confused with the electric rays called torpedo rays, but guitarfish lack the organs needed to deliver an electric shock. They have rounded teeth and prefer crustaceans and mollusk to fish. There is only one species in the Gulf.
Torpedo rays can deliver an electric shock – about 35 volts of one. Though there are stories of these shocking folks to death, I am not aware of any fatalities. Nonetheless, the shock can be serious and beach goers are warned to be cautious. I once mistook one buried in the sand for a shell. Let us just say the jolt got my attention and I may have had a few words for this fish before I returned to the beach. We have two species of torpedo rays in the Gulf of Mexico.
Skates look JUST like stingrays – but they lack the whip-like tail and the venomous spine that goes with it. They are very common in the inshore waters of the Florida Panhandle and though they lack the terrifying spine we are all concerned about, they do possess a series of small thorn-like spine on the back that can be painful to the bare foot of a swimmer. Skates are famous for producing the black egg case folks call the “mermaids’ purse”. These are often found dried up along the shore of both the Gulf and they bay and popular items to take home after a fun day at the beach. There are four species of skates found in the Gulf of Mexico.
Stingrays… this is the one… this is the one we are concerned about. Stingrays can be found on both sides of our barrier islands and like to hide beneath the sand to ambush their prey. More often than not, when we approach they detect this and leave. However, sometimes they will remain in the sand hoping not to be detected. The swimmer then steps on their backs forcing them to whip their long tail over and drive the serrated spine into your foot. This usually makes you move off them – among other things. The piercing is painful and spine (which is actually a modified tooth) possesses glands that contain a toxic substance. It really is no fun to be stung by these guys. Many people will do what is called the “stingray shuffle” as they move through the water. This is basically sliding your feet across the sand reducing your chance of stepping on one. They are no stranger to folks who visit St. Joe Bay. The spines being modified teeth can be easily replaced after lodging in your foot. Actually, it is not uncommon to find one with two or three spines in their tails ready to go. Stingrays do not produce “mermaids’ purses” but rather give live birth. There are five species in the Gulf of Mexico.
The Atlantic Stingray is one of the common members of the ray group who does possess a venomous spine.
Photo: Florida Museum of Natural History
Butterfly ray is a strange looking fish and easy to recognize. The wide pectoral fins and small tail gives it the appearance of a butterfly. Despite the small tail, it does possess a spine. However, the small tail makes it difficult for the butterfly ray to pierce you with it. There is only one species in the Gulf, the smooth butterfly ray.
Eagle rays are one of the few groups of rays that actually in the middle of the water column instead of sitting on the ocean floor. They can get quite large and often mistaken for manta rays. Eagle rays lack the palps (“horns”) that the manta ray possesses. Rather they have a blunt shaped head and feed on mollusk. They do have venomous spines but, as with the butterfly ray, their tails are too short to extend and use it the way stingrays do. There are two species. The eagle ray is brown and has spots all over its back. The cownose ray is very common and almost every time I see one, I hear “there go manta rays”… again, they are not mantas. They have a habit of swimming in the surf and literally body surfing. Surfers, beachcombers, and fishermen frequently see them.
Last but not least is the very large Manta ray. This large beast can reach 22 feet from wingtip to wing tip. Like eagle rays, they swim through the ocean rather than sit on the bottom. They have to large “horns” (called palps) that help funnel plankton into their mouths. These horns give them one of their common names – the devilfish. Mantas, like eagle and butterfly rays, do have whip-like tails and a venomous spine, but like the above, their tails are much shorter and so effective placement of the spine in your foot is difficult.
Many are concerned when they see rays – thinking that all can inflict a painful spine into your foot – but they are actually really neat animals, and many are very excited to see them.
References
Hoese, H.D., R.H. Moore. 1977. Fishes of the Gulf of Mexico; Texas, Louisiana, and Adjacent Waters. Texas A&M. College Station, TX. pp. 327.
Shipp, R. L. 2012. Guide to Fishes of the Gulf of Mexico. KME Seabooks. Mobile AL. pp. 250.
by Rick O'Connor | May 25, 2018
In the mid 1990’s, the Bay Area Resource Council was created. This multi-county (Escambia and Santa Rosa) organization included local scientists and decision makers to help better understand the health of Pensacola Bay, develop a plan for restoration, and work collaboratively to acquire funding to do so. At the inaugural meeting, many different scientists spoke on a variety of topics. There were several take-home messages – one of them was that sediments of Pensacola Bay were in poorer health than the water within the water column above it.
Grabs are used by marine scientist to collect samples of sediments from the bottom of the bay.
Photo: Coastal Science NOAA
So, what is wrong with the sediments, and how has this changed since the mid ‘90’s?
Based on sediment sample analysis, some researchers consider the Pensacola Bay System the most polluted in the state of Florida… but not everyone. The three bayous (Chico, Texar, and Grande), Escambia Bay, and the downtown waterfront of Pensacola Bay had some of the poorest sediment samples within the system. Contaminants monitored include trace metals, mercury, non-nutrient organics, pesticides, and dioxins. These contaminants are dense and do not remain in the water column long. Instead, they sink into the sediments. At that time, some suggested that attempts to remove the contaminants could increase their levels within the water column and do more harm than good – thinking it would be better to leave the sediments as they are. Many of the compounds entered the estuary through run-off. In some cases in the past, they were discharged directly into a bay or river.
Chemicals found in Pensacola estuarine sediments include Arsenic, Zinc, and Copper. Mercury levels at some locations in the bay are higher than other estuaries around the northern Gulf region. Some non-nutrient organic compounds were not as high as other local estuaries however; bioaccumulation (the increase in contaminant concentrations via the food chain) has been occurring and should be monitored. Many chemical compounds banned in the 1970’s have long half-lives and are still detected in the sediments today. Chlorinated pesticides, such as dieldrin, chlordane, DDE, DDD, and DDT are still found in the bayous – and at higher concentrations than neighboring estuaries.
This all sounds bad, but are the levels high enough to be toxic to marine organisms?
Herbicides and pesticides can find their way into estuarine systems and contaminate the sediments.
Photo: UF IFAS Washington County Extension
One location, in upper Bayou Texar, seems to be quite toxic to the species of bacteria, invertebrates, fish, and plants tested. These toxic concentrations are partially from chemicals present in run-off, but there is also seepage coming from groundwater contaminated from a nearby Superfund site. Most of the test suggest that the lethal concentrations are more chronic in nature than acute.
So what can be done? What can we do?
Well… removing and treating these sediments is quite expensive and is not an option at this time. There are plans to dredge portions of Bayou Chico but the process has undergone extensive scrutiny and permitting. One thing we can do is reduce the amount that is still entering the bay. How do we do this?
- Consider re-landscaping your yard to be “Florida Friendly”. Using the suggestions given within this University of Florida program (http://fyn.ifas.ufl.edu/) you can reduce the amount of fertilizer, herbicide, and pesticides you use – thus reducing the amount entering the estuaries.
- Florida Friendly Landscaping practices can also reduce the amount of watering your lawn needs. This reduces the amount of run-off reaching the bay and always reduces the amount of money you spend on watering and lawn chemicals.
- The Florida Department of Environmental Protection’s Clean Boater program provides tips and suggestions that reduce the amount of hazardous chemicals that enter the bay from cleaning and maintaining vessels. https://floridadep.gov/fco/cva/content/clean-boater-program.
The sediments of the bay have suffered the abuse of the past. However, with better practices, we can reduce our impact in the future.
Florida Friendly Landscaping saves money and reduces our impact on the estuarine environment.
Photo: UF IFAS
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.
by Rick O'Connor | May 25, 2018
In recent weeks, volunteers and I have been surveying local estuaries counting terrapins, horseshoe crabs, and monitoring seagrass. One animal that has been very visible during these surveys is the relatively large snail known as the crown conch (Melongena corona). Its shell is often found with a striped hermit crab living within, but it is actually produced by a fleshy snail, who is a predator to those slow enough for it to catch.
The white spines along the whorl give this snail its common name – crown conch.
Photo: Rick O’Connor
The shell is familiar to most who venture to the estuary side of our beaches. Reaching around five inches in length, crown conch shells are spiral with a wide aperture (opening) and brown to purple to white in color. Each whorl ends with white spins giving it the appearance of a crown and – hence – it’s common name. They are typically seen cruising along the sediments near grassbeds, salt marshes and oyster reefs – their long black siphons extended drawing in seawater for oxygen, but also to detect scents that will lead them to food.
These snails breed from winter to early summer. Females, larger than males, will develop 15-500 eggs in capsules, which they attach to hard structures within the habitat; such as wood, seagrass blades, and shell material.
Crown conchs are subtropical species and have a low tolerance for cold water. They are common in the panhandle and may expand further north along the Atlantic coast if warming trends continue. They have a higher tolerance for changes in salinity and can tolerate salinity as low as 8 ppt. The salinities within Pensacola Bay can be as low as 10 ppt and Santa Rosa Sound / Big Lagoon are typically between 20-30 ppt. The developing young require higher salinities and thus breeding takes in the lower portions of our estuaries.
These are guys are snail predators – seeking prey slow enough for them to catch. Common targets include the bivalves such as oysters and clams, but they are known to seek out other snails – like whelks. Crown conchs are known to feed on dead organisms they encounter and may be cannibalistic. As with all creatures, they have their predators as well. The large thick shell protects them from most but other snails, such as whelks and murex, are known predators of the crown conch.
These conchs tend to stay closer to shallow water (less than 3 ft.) due the large number of predators at depth. They are common in seagrass meadows and salt marshes and – if in high numbers with few competitors – have been considered an indicator of poor water quality. There is no economic market for them but they are monitored due to the fact they affect the populations of commercially important oysters and clams.
The “snorkel” is called a siphon and is used by the snail to draw water into the mantle cavity. Here it can extract oxygen and detect the scent of prey.
Photo: Franklin County Extension
It is an interesting animal, a sort of “jaws” of the snail world, and a possible candidate for a citizen science water quality monitoring project. Enjoy exploring your coastal estuaries this summer and discover some of these interesting animals.
Reference
Masterson, J. 2008. Indian River Lagoon Species Inventory: Crown Conch Melongena corona. Smithsonian Marine Station at Ft. Pierce, Florida. http://www.sms.si.edu/irlspec/Melongena_corona.htm.
