by Rick O'Connor | Jul 6, 2018
The manatee may be one of the more iconic animals in the state of Florida. In Wyoming, we think of bison and bears. In Florida, we think of alligators and manatees. However, encountering this marine mammal in the Florida panhandle is a relatively rare occurrence… until recently.
Manatee swimming in Big Lagoon near Pensacola.
Photo: Marsha Stanton
For several years now, visitors to Wakulla Springs – in the eastern panhandle – have had the pleasure of viewing manatees on a regular basis. It is believed about 40 individuals frequent the river. Last year there were eight individuals that frequent the Perdido Key area, and a couple more were seen more than once near Gulf Breeze. This is not normal for us, but already this year one manatee has been spotted in the Big Lagoon area – so we may be seeing more as the summer goes on.
So what exactly is a manatee?
It is listed as a marine mammal, but frequents both fresh and saltwater habitats. Being mammals, they are warm blooded (endothermic). Maintaining your body temperature internally allows you to live in a variety of cold temperature habitats but water can really draw the heat quickly from anyone’s body. Marine mammals counter this problem by having a thick layer of fat within the skin – insulation called blubber. However, the manatees blubber layer is not very thick. So they are restricted to the tropical parts of the world and, in Florida, spend the winter near warm water springs. Many have learned the trick of hanging out near warm water discharges near power plants. In the warmer months, they venture out to find lush seagrass meadows in which to graze.
They are herbivores. Possessing flat-ridged molars for grinding plant material, they are more closely related to deer and cattle than the seal and walrus they look like. They lack canines and incisors, which deer and cattle use to cut the grass blades, but have large extending lips that grab and tear grasses with – very similar to the trunk of an elephant, which is their closest relative. Like many mammalian herbivores, they grow to a large size. Manatees can reach 15 feet in length and over 1000 pounds. They have two forearms that are paddle shaped and used for steering. The tail is a large circular disk called a fluke, which propels them through the water and is often seen breaking the surface. They are generally slow moving animals but can startle you when they decide to kick into “fourth gear” and burst across the river.
They are generally solitary animals, gathering in the wintertime around the warm springs. Males usually leave the females after breeding and do not form family units, or herds. Females are pregnant for 13 months and typically give birth to one calf, which stays with mom for two years. Like all mammals, the young feed on milk from mammary glands, but these glands are close to the armpits on the manatee. This makes it much easier for the calf to feed while both are swimming. This is not the case with dolphins and whales, where the mother must roll sideways to feed her young.
Manatees hanging out in Wakulla Springs.
Photo provided by Scott Jackson
There are three species of manatees in the world today. The Amazonian Manatee (Trichechus inunguis), the West African Manatee (Trichechus senegalensis) and the West Indie Manatee (Trichechus manatus). The Florida Manatee is a subspecies of the West Indian (Trichechus manatus latirostris). In the 1970’s it was estimated there were about 1000 West Indian manatees left in the word. Today, with the help of numerous nonprofits and state agencies, there is an estimated 6600 in Florida. Due to this increase, the manatee has moved from the federal endangered species list to threatened species. That said, human caused mortality still occurs and boaters should be aware of their presence. Since 2012, an average of 500 manatees die in Florida waters. Most of these are prenatal or undetermined, but about 20% are from boat strikes. Manatees tend stay out of the deeper channels, so boats leaving the ICW for a favorite beach or their dock should keep an eye out. Most of the time they are just below the surface and only their nostrils break for a breath of air. They usually breathe every 3-5 minutes when swimming but can remain below for up to 20 minutes when they are resting. Approaching a manatee is still illegal. Though their status has changed from endangered to threatened, they are still protected by state and federal law.
FWC suggest the following practices for boaters, and PWC, near manatees
- Abide by any speed limit signs – no wake zones
- Wear polarized sunglasses to aid in seeing through the water
- Stay in deeper water and channels as much as possible
- Stay out of seagrass beds – there is are numerous reasons why this is important, not just manatees
- If a manatee is seen, keep your boat/PWC at least 50 feet from the animal.
- Please do not discard your hooks and monofilament into the water – again, numerous reasons why this is a bad practice.
So Why are There More Encounters in the Florida Panhandle?
Good question…
Their original range included the entire northern Gulf coast. When their numbers declined in the 1960’s and 70’s there were fewer animals to venture this far north. Manatee sightings at that time did occur, but were very rare. Today, with increasing numbers, encounters are becoming more common. There is actually a Manatee Watch Program for the Mobile Bay area (https://manatee.disl.org/) and they have been seen as far west as Louisiana.
They are truly neat animals and to see one in our area is a real treat. Remember to view and photo, but do not approach. I hope that many of you will get to meet what maybe new summer neighbors.
Manatee swimming by a pier near Pensacola.
Photo: Marsha Stanton
References
2017 Manatee Mortality Data. Florida Fish and Wildlife Conservation Commission. http://myfwc.com/media/4132460/preliminary.pdf.
Florida Manatee Facts and Information. Florida Fish and Wildlife Conservation Commission. http://myfwc.com/education/wildlife/manatee/facts-and-information/.
Manatee Information for Boaters and PWC. Florida Fish and Wildlife Conservation Commission. http://myfwc.com/education/wildlife/manatee/for-boaters/.
Manatee Sighting Network. https://manatee.disl.org/.
West Indian Manatee. Wikipedia. https://en.wikipedia.org/wiki/West_Indian_manatee.
by Rick O'Connor | Jul 6, 2018
This week’s article is a bit different… it is about nature we hope you DO NOT see – but hope you let us know if you do. Most of you know that Florida, along with many other states, continually battle invasive species. From Burmese pythons, to lionfish, to monitor lizards, we have problems with them all. Many of our invasive species are plants, which grow aggressively and take over habitats. They have few, if any, predators to control their populations and can cause environmental or economic problems for us.
The pretty, but invasive, beach vitex. Photo: Rick O’Connor
The best way to tackle an invasive species is to detect it when it first arrives and remove it as quickly as possible – this provides you the best chance of actually eradicating it from an area at the lowest cost. One such invasive plant that has recently invaded Escambia and Santa Rosa county beaches is Beach Vitex (Vitex rotundifolia).
Beach vitex is a vine that grows along the surface of sandy areas, like dunes. It has a main taproot from which the runners (stolons) extend in a radiating pattern, like a skinny-legged starfish. The stolons will develop secondary roots, which can form smaller deep root systems, and the entire maze of vines grows very quickly in the summer. The leaves are ovate, more round than elongated, and have a grayish-blue-green color to them – they tend to stand out from other plants. The plant can grow vertically to about three feet, giving it a bush appearance.
Another key characteristic for identification are the lavender flowers it produces, few other plants in our dunes do – so this is a good thing to look for. The flowers appear in late spring and summer. They are actually quite pretty. In the fall, the flowers are replaced by numerous large seeds, which form in clusters where the flowers were. These seeds are problematic in that they can remain viable for up to six months if they fall into the water – increasing their chance for dispersal.
So what is the problem?
In the Carolina’s this species was planted intentionally. They quickly learned of its aggressive nature and have had a state task force to battle it. The plant is allopathic – it can release toxins that kill neighboring plants allowing them to move into that space – this includes sea oats. Beach vitex has a taproot system, unlike the fibrous one of the sea oat, and cannot stabilize a dune as well – which is a problem during storms. In the Carolina’s there are numerous beach fronts where this is the only plant growing, a problem waiting to happen. Though there are no reports of it happening, it also has the potential to affect sea turtle nesting.
Beach Vitex Blossom. Photo credit: Rick O’Connor
So what do I do if I see it?
Contact us… You can contact me at roc1@ufl.edu, or call (850) 475-5230. Try to give us the best description of where the location is as you can. Many phones now come with an app that has a compass. This app also gives you your latitude and longitude. If your phone does not have this, again, give us the best description of the location you can. If you can include a photograph, that would be great. There are numerous other invasive species roaming our area, and you are welcome to report any you find to us. We hope to stay on top of these early arrivals and keep them under control.
by Rick O'Connor | Jul 6, 2018
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.
by Rick O'Connor | Jun 22, 2018
Just a decade ago, few people would have known what a gopher tortoise was and would have hard time finding one. But today, because of the protection they have been afforded by the state, they are becoming more common. This is certainly an animal you might see visiting one of our state parks.
This gopher tortoise was found in the dune fields on a barrier island – an area where they were once found.
Photo: DJ Zemenick
The gopher tortoise is one of only two true land dwelling turtles in our area and is in a family all to its own. They are miners, digging large burrows that can extend up to a depth of 7 feet and a length of 15 feet underground. However, tortoises are not very good at digging up towards the surface, so there is only the one entrance in and out of the burrow. The burrow of the tortoise can be distinguished from other burrowing animals, such as armadillos, in that the bottom line of the opening is flat – a straight line – and the top is domed or arched shaped; mammalian burrows are typically round – circular. Tortoise burrows also possess a layer of dirt tossed in a delta-shaped fan out away from the entrance (called an apron). Many times the soil is from deeper in the ground and has a different color than the soil at the surface. The general rule is one burrow equals one tortoise, though this is not always true. Some burrows are, at times, shared by more than one and some may not be occupied at all. Many field biologists will multiple the number of burrows by 0.6 to get an estimate of how many tortoises there are in the area.
The tortoise itself is rather large, shell lengths reaching 15 inches. They can be distinguished from the other land dwelling turtle, the box turtle, by having a more flattened dome to the shell and large elephant like legs. The forelimbs are more muscular than the hind and possess large claws for digging the burrow. They are much larger than box turtles and do not have hinged plastrons (the shell covering the chest area) and cannot close themselves up within the shell as box turtles can. Tortoises prefer dry sandy soils in areas where it is more open and there are plenty of young plants to eat; box turtles are fans of more dense brush and wooded areas.
Tortoises spend most of the day within their burrows – which remain in the 70°F range. Usually when it is cooler, early morning or late afternoon, or during a rain event – the tortoises will emerge and feed on young plants. You can see the paths they take from their burrows on foraging trips. They feed on different types of plants during different type times of the year to obtain the specific nutrients. There are few predators who can get through the tough shell, but they do have some and so do not remain out for very long. Most people find their burrows, and not the tortoise. You can tell if the burrow has an active tortoise within by the tracks and scrap marks at the entrance. Active burrows are “clean” and not overgrown with weeds and debris. Many times, you can see the face of the tortoise at the entrance, but once they detect you – they will retreat further down. Many times a photo shot within a burrow will reveal the face of a tortoise in the picture. There is a warning here though. Over 370 species of creatures use this burrow to get out of the weather along with the tortoise – one of them is the diamondback rattlesnake. So do not stick your hand or your face into the entrance seeking a tortoise.
Most of the creatures sharing the burrow are insects but there are others such as the gopher frog and the gopher mouse. One interesting member of the burrow family is the Eastern Indigo Snake. This is the largest native snake to North America, reaching a length of eight feet, and is a beautiful iridescent black color. It is often confused with the Southern Black Racer. However, the black racer is not as long, not as large around (girth), and possess a white lower jaw instead of the red-orange colored one of the indigo. The indigo is not dangerous at all, actually it feeds on venomous snakes and it is a good one to have around.
Federal and state laws protect the indigo, as with the gopher frog and mouse. All of these animals have declined in number over the past few decades. This is primarily due to loss of the needed gopher burrows, which have declined because the tortoises have declined, and this is due to habitat loss and harvesting. Again, tortoises like dry sandy soils for digging burrows. They prefer wooded areas that are more open and allow the sun to reach the forest floor where young grasses and flowers can grow. The longleaf pine forest is historically the place to find them but they are found in coastal areas where such open wooded areas exist. The lack of prescribe burning has been a problem for them. Florida is the number one state for lightning strikes. Historically, lightning strikes would occasionally start fires, which would burn the underbrush and allow grasses to grow. In recent years, humans have suppressed such fires, for obvious reasons, and the tortoise community has suffered because of it. Therefore, we now have prescribe fire programs on most public lands in the area. This has helped to increase the number of tortoises in the area and your chance of seeing one.
All of the members of the tortoise community are still protected by state, and – in the case of the indigo snake – federal law, so you must not disturb them if seen. Photos are great and you should feel lucky to have viewed one. Though they could be found anywhere where it is high, dry, and somewhat open – the state and national parks are good places to look.
Reference
Meylan, P.A. (Ed.). 2006. Biology and Conservation of Florida Turtles. Chelonian Research Monographs No. 3, 376 pp.
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.
