by Rick O'Connor | May 12, 2018
Records of the variety of aquatic life in Pensacola Bay go back to the 18th century. According to these reports, over 1400 species of plants and animals call Pensacola Bay home. Many of them depend on seagrass, oyster reefs, or marshes to complete their life cycle. The greatest diversity and abundance are found on the oyster reefs. Finfish and shellfish in the bay have sustained humans as a food source for centuries. However, we know that the alligator, turtles, and a variety of birds and mammals have also been important. In this article, we will focus on the aquatic species.
Red Drum – photo credit Florida Fish and Wildlife
When people think of aquatic life in the bay, they first think of fish. About 200 species call Pensacola Bay home. The most abundant are the true estuarine fish, such as croakers, sardines, and minnows. There are a variety of marine transient fish that can be found such as jacks, mackerels, and some species of sharks. Spot and Atlantic Croaker are the most abundant members of the croaker family, and are still an important target fish for locals. Anyone who has snorkeled or cast a line with cut bait knows how common pinfish can be, and those who have pulled bait nets are very familiar with the silverside minnows and anchovies.
I have pulled many a seine net over the years assessing the diversity and abundance of the nearshore fish populations and logged 101 species. In addition to those listed above, killifish (also locally known as “bull minnows”) are a common capture. For a few years, we were involved in trawling in deeper waters where we collected a variety of flounder, silver perch, grunts and snapper. Sea robins are an interesting member of our community and gag grouper were captured occasionally. The number and variety of fish found varies with seasons and is greatest in June. The diversity and abundance of estuarine fishes in our bay is very similar to neighboring estuaries.
The second thing people think of when they think of aquatic life in the bay are shellfish. These would include the crabs, shrimp, and oysters. However, the most abundant macro-invertebrates in our bay are those that can tolerate environmental stress and live in the surface layers of the sediments – these are the worms and crustaceans. There are numerous varieties of segmented polychaete worms, who are famous for building tunnels with “volcano” openings. They are also common within oyster reefs, feeding on all sorts of organic debris. Blue crab are common throughout the bay and provided both a commercial and recreational fishery for years. Brown and white shrimp are both found and have been the most popular seafood with locals for years.
The famous blue crab.
Photo: FWC
During my lifetime, the only marine mammal commonly seen has been the Atlantic Bottlenose Dolphin, and these are found in many parts of the bay. Years back, I heard accounts of harbor porpoise, but never actually saw one. An historic occurring marine mammal, who seems to be making a comeback, is the Florida Manatee. Sightings of this animal have been reported in a variety of locations in recent years.
Snakes, turtles, and alligators are all found in the bay area. There is really only one saline snake and this is the gulf coast salt marsh snake. However, nontraditional estuarine snakes, such as the cottonmouth, are becoming more common in and near the bay. Though we have a great variety of turtles in our rivers, only one true estuarine turtle exist in the country, the diamondback terrapin – and this turtle can be found in parts of our bay. Sea turtles do venture into the bay searching for food, particularly the green turtle who is fond of seagrasses.
Many forget the small planktonic animals that drift in the water column, but they are there – about 100 species of them. Copepods are small roach looking crustaceans that are by far the most abundant member of the zooplankton, particularly the species known as Acartia tonsa – which makes up 82% of the abundance in our bay. These small animals are an important link in the food chain of almost every other member of the bay community. The zooplankton variety in Pensacola Bay is very similar to those of neighboring estuaries.
And then there are the plants…
By far, the most diverse group of organisms in the bay are the microscopic plants known as phytoplankton – with over 400 species reported. Much of the bay is too deep to support traditional forms of plants and so these become a key producer of food for many species. The diversity and abundance is greatest in the spring and fall. 70% of the phytoplankton are from a group called dinoflagellates, small plants that have two hair-like flagella to orient, and even propel, themselves. Some of them produce the bioluminescence we sometimes see and others produce what we call red tide. During the summer, the populations change and the more abundant forms are diatoms. These lack the flagella of the dinoflagellates, but they do produce beautiful shells of silica.
There are at least 400 species of periphytic algae (attaching). Green algae are the most abundant and are most common in the local bayous. Cyanobacteria, which were once thought to be algae, are the most abundant in the marshes and periphytic diatoms dominate in the Sound.
And last, are the submergent and emergent grasses.
Submergent grasses are known as seagrasses. We have three species that like the higher saline waters. These are turtle, shoal, and widgeon grass. Turtle and shoal grass need the water to be at least 25 parts per thousand and are the dominate species in the lower portions of the bay. Widgeon grass can tolerate waters as low as 10 ppt and are found in the bayous and the upper portions of the bay system. Tapegrass only survives in freshwater and are found in the lower reaches of the rivers where they meet the bay.
Emergent grasses are what we call marsh grasses. Two species, Black Needlerush and Smooth Cordgrass dominate these. There are pockets of salt marshes found all over the bay system.
So how is the health of our aquatic life?
As you might expect, the diversity and abundance have declined over time, particularly since the 1950’s. One firsthand account of the change, describe a bayou that was clear, full of grass, and harbored shrimp the size of your hand. Then they were gone. He remembered the first change being water clarity. As development along our waterfront increased, the clarity decreased and the aquatic life declined. This has happened all over the bay system. Increase in run-off not only brought sand and sediment lowering water clarity, it also brought chemicals that both the plants and animals could not tolerate. Much of the point source pollution has been controlled but non-point pollution is still problematic. Fertilizers, pesticides and herbicides, oils and grease, and sediment have all been problematic. These can be reduced. Following recommendations from the Florida Friendly Landscaping website, (http://www.deactivated_site/.) property owners can alter how they are currently managing their landscape to reduce their impact on the aquatic life on the bay. Clean Marina (https://floridadep.gov/fco/clean-marina ) and Clean Boater (https://floridadep.gov/fco/cva/content/clean-boater-program ) recommendations can help reduce the impact from the boating community. Sustainable fishing practices, such as safe catch and release methods for unwanted fish and removing all monofilament are good practices. In 2019, Sea Grant will begin a program training local citizens how to monitor the diversity and abundance of aquatic species. If interested in volunteering, stay tuned.
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 | Apr 14, 2018
In my job, I get many calls about snakes. Most people want to know how to tell a venomous from a nonvenomous one and how to keep them out of the yard. I was recently reading a new book out by Dr. Sean Graham entitled American Snakes and in the chapter on snake defenses, he provided a long litany of local creatures who consumed snakes – some surprised me. Check this out…
The “cottonmouth” gape of this venomous snakes is a warning. Notice the banded coloration of this individual.
Photo: UF IFAS Wildlife
First, most who do only consume smaller species of snakes – but the list is still surprising. Spiders… spiders were on the list. He specifically called out the black widow – who probably could kill a small snake, but indicated there were others. Scorpions, centipedes, fire ants, carpenter ants, giant water bugs, crayfish, and crabs made the list as well. Some of these may consume snakes only after they are dead – but some can kill small ones.
From the vertebrate world he mentions the larger salamanders (such as the hellbender), and other snakes (such as the short-tailed snake and the coral snake). There are several mammals including shrews, moles, and even the rodents themselves are consumers of snakes! He describes how hoofed mammals (such deer, goat, and horses) do not consume snakes, but can completely destroy one by raising and stopping on them – leaving only small segments remaining. They have found the remains of snakes in the stomachs of all predatory mammals but the snake’s greatest threat are birds… by a long shot. Species from passerines to raptors have been known to kill and consume snakes.
What about venomous snakes – who consumes rattlesnakes and cottonmouths?
There are surprises here as well…
Bullfrogs… bullfrogs basically consume what they can get into their mouths but this includes snakes – and venomous ones as well (though they would be small ones). From the fish world, both the gar and largemouth bass are known to consume venomous snakes.
A coyote moving on Pensacola Beach near dawn.
Photo provided by Shelley Johnson.
Opossums are known to consume at least 12 species of snakes, including venomous ones. They also consume ticks, fire ants, and have a very low occurrence of rabies – a cool animal to have around.
Other mammal consumers of venomous snakes include raccoons, otters, fox, bobcats, coyotes, and black bears. It is understood they must take smaller members of the venomous snake population – but a snake control is snake control.
Most wading birds in our marshes consume snakes, including venomous ones, but it is the red-tailed hawk and the great horned owl that are the masters. Red-tailed hawks are known to consume at least 35 species of snakes, including venomous ones, and – unlike other snake predators – are a larger part of their diet, they seek them out. Great Horned Owls consume at least 13 species, and venomous ones are on the menu.
From the reptile world we begin with the alligator, who has little problem consuming large specimens of both the rattlesnake and the cottonmouth. However, many are snakes… yes, snakes eat snakes and some consume venomous ones. Coral snakes, coachwhips, and cottonmouths have been known to consume other snakes. However, it is the Eastern Indigo and the Kingsnakes who actively seek out venomous species. It is known that kingsnakes have a protein in their blood that makes them immune to the viper’s venoms – and it appears the vipers know this and avoid them. It is not known whether the indigo is immune, but it is known they will seek out venomous snakes and consume. Both of these snakes can take relatively large venomous species.
Of these two, it is the Kingsnake who is the “king” – consuming at least 40 species of snakes. However, both the kingsnakes and the indigo are on the declined. The eastern indigo is currently federally listed as endangered – there has not been a verified record of one in the Florida panhandle since 1997. However, there are anecdotal reports and we encourage anyone who has seen one to send us a photograph. There is an active indigo restoration program going on in Alabama and in the Apalachicola River area. These are the largest native snakes in the U.S. (about 8 feet) and, along with the six-foot kingsnakes, are frequently killed. There is evidence that as the eastern kingsnake populations decline copperhead populations increase, and Vis versa. Some areas near Atlanta are currently experiencing a copperhead “boom”. Clearly, we should reconsider killing both the indigo and kingsnakes. We also understand that habitat loss is another cause of their decline, particularly in the case of the indigo.
When looking at this list of snake consumers we see species that cause other problems – alligators, raccoons, coyotes, and bears have all have had their negative issues. But many we just do not like, such as the opossum, really cause us no harm and control snake populations. Everything has its place in the local environment and not one species seeks out humans for the purpose of harming us – this would include snakes. The negative encounters are for other reasons. But for those who have a deep fear, or are currently experiencing high snake numbers, seeing one of the animals on this in the neighborhood could be a relief.
References
Graham, S. 2018. American Snakes. John Hopkins University Press. Baltimore MD. Pp 293.
O’Connor, M. 2018. Personal communication.
by Rick O'Connor | Feb 16, 2018
As a young boy growing up here in the panhandle, I had heard of this thing called a manatee – but had never seen one. They came more into the light when I was a teenager and becoming interested in marine biology. I was the president of the high school marine biology club and one of our goals was to raise money for a trip to Crystal River to snorkel with them. The Save the Manatee Club originated in that time trying to bring more awareness to the plight of this endangered Floridian and at one point, Jimmy Buffett had led the way.
I had learned a lot about them, found out their original range was from North Carolina south to the Caribbean and the entire Gulf of Mexico, but were now down to about 1000 animals and those were found in Florida. Eventually I did get to see manatees, and have snorkeled with them many times, but still thought of them as a south Florida animal – rarely found in the panhandle.
Manatee swimming in Big Lagoon near Pensacola.
Photo: Marsha Stanton
Then the recent news report – two dead manatees in the last two weeks. One washed ashore in Okaloosa county and the other in Escambia. Probably victims of the recent cold fronts. It is not unheard of finding manatees in the panhandle in recent years. I recall since the 1990’s a manatee seen in Bayou Texar in Pensacola. In another year, one was seen near Ft. Pickens. My son worked at a local marina and saw at least one a year there. There have been so many seen in the Mobile Bay area that Dauphin Island Sea Lab now has a Manatee Watch program. There are about 40 individuals that now visit Wakulla Springs. In addition, this summer there were two separate groups living in the Pensacola area. One group was residing near Gulf Breeze and a second group of about eight animals was frequently seen near Perdido Key. These once rare animals in the panhandle are now being found each year, and sometimes in groups.
What is going on?
Why are manatees beginning to visit our area?
Your first hunch would be climate change. Manatees are marine mammals but unlike their dolphin cousins their blubber layer is not as thick and they must seek warm water refuge during the winter months. When water temperatures drop below 67°F, they locate the warm water springs found in central Florida – or move south Florida where the water remains comfortable year round. If they are remaining here, could the average water temperatures have warmed enough for them to make this move?
Along this same line, mangroves are now being found in the panhandle. Both red and black mangroves have been found growing in local estuaries. In the Apalachicola area there have been quite a few located. In the western panhandle there a few individuals here and there. Further west they are found on the islands of Mississippi and have been in the Chandeleurs for many years now. Later this spring Florida Sea Grant will be conducting surveys in each county to see where these tropical trees may be growing.
A small red mangrove growing in Big Lagoon near Pensacola FL
Photo: Rick O’Connor
And most recently are sightings of snook, a south Florida fish that have, though rare, been seen in the northern Gulf of Mexico. No doubt this Januarys hard freezes probably killed the mangroves that were here, and probably the two manatees washed ashore recently, but it will be an interesting time to see what other tropical species begin their slow migration northward. If it does happen, what will that mean? How will these changes impact local ecosystems? At this point, I am not sure if it will happen or, if it does, how fast – but it will be interesting.
by Rick O'Connor | Feb 2, 2018
Man what a winter!
Between multiple days below freezing, tough traveling, and the flu it has been a brutal winter season so far.
Dead Kemps Ridley Sea Turtle washed ashore in Little Sabine near Pensacola Beach. This turtle died of ingesting monofilament fishing line.
Photo: Betsy Walker
It is not that different for some of our marine wildlife friends. The low temperatures have driven marine water temperatures down as well, particularly in the shallow areas. There have been many reports of cold stunned sea turtles up and down the Florida panhandle – over 900 of them. There have been reports of cold stunned iguanas falling from trees and the loss of pythons in south Florida. The question sometimes comes up – “how do they deal with this apparent return from the dead?”
One has to remember we are dealing with reptiles – cold-blooded creatures. Actually, the more correct term is poikilothermic. It really does not pertain to the temperature of their blood but their core body temperature in general. Some animals, like humans, can maintain a constant body temperature, like 98.6°F, no matter what the environmental temperatures are – these are referred to as homotherms. Heterotherms can allow their body temperatures fluctuate within a range – but are in control of their body temperatures. The poikilotherms cannot control their body temperature and are thus at the mercy of the environment – the classic “cold blood”. Some of these poikilotherms have been known to actually freeze and thaw – with no observable problems, not so much for our “warm blooded” friends.
So what’s up with the cold-stunned situation?
Well… even with the “cold bloods”, extreme temperature changes can be very stressful. Some respond by changing their behavior, others their physiology, others both. They will alter their feeding – basically stop. In some, the pH and ion balance within their blood becomes unbalanced, which can trigger the feeding reduction response and increase ion exchange within the lungs. The partial pressure within the venous blood can decrease and this, along with the chemical imbalance and feeding reduction, can trigger a “lethargic” response and even a “floating” response in the marine turtles.
Locally, it seems to be the sea turtles who are having the most problems. In south Florida, scientists have noticed the American Crocodile and the invasive pythons struggle with these cold temperatures but the wider ranged American Alligator and numerous species of native snakes do not. The “locals” seem to alter their behavior to adjust for these extreme temperature drops – a method that the tropical species are not practicing. It is known that certain native freshwater turtles over winter in frozen ponds, and diamondback terrapins are known to “hunker down” in muddy bottoms of salt marsh creeks when water temperatures drop below 59°F.
With sea turtles, the larger migratory individuals offshore are still moving at 43°F but is the smaller inshore juveniles that are the subject of stunning events. The water temperatures change more rapidly in shallower water and at 43°F, these smaller sea turtles become lethargic and float – which increases their chance of predation. Data suggest that Green Sea Turtles begin to slow activity and Kemps Ridleys become more agitated when water temperatures drop below 68°F, both become dormant, reduce feeding and breathing when they drop below 59°F. It is believed the real problems from being cold stunned are from the reduction of food as much, if not more than, the actual temperature itself. The “cold bloods” bask to increase their body temperatures so that they can actually digest their food.
It is a problem frequently encountered along the American east coast but not as much in Florida. However, this year has been different. The staff and volunteers from government agencies and local aquaria have done a champion job rescuing and rehabilitating many of these animals.
References
Mazzotti, F. J., M. S. Cherkiss, M. Parry, J. Beauchamp, M. Rochford, B. Smith, K. Hart, and L. A. Brandt. 2016. Large reptiles and cold temperatures: do extreme cold spells set distributional limits for tropical reptiles in Florida? Ecosphere 7(8):e01439. 10.1002/ecs2.1439
Moon D.Y., D.S. MacKenzie, D.W. Owens. 1997. Simulated Hibernation of Sea Turtles in the Laboratory: I. Feeding, Breathing Frequency, Blood PH, and Blood Gases. The Journal of Experimental Zoology. 278: pp. 362-380.
Milton, S.A., P.L. Lutz. 2003. The Biology of Sea Turtles, Volume II. Edited P.L. Lutz, J.A. Musick, J. Wyneken. CRC Press. Pp. 510.
by Rick O'Connor | Jan 19, 2018
In the last article, we discussed what phytoplankton are, what their needs were, and their importance to marine life throughout the Gulf and coastal estuaries. In this article, we will discuss the different types of phytoplankton found in our waters.
The spherical shape of the centric diatom.
Image: Florida International University
Marine scientists interested in the diversity and abundance of phytoplankton will typically sample using a plankton net. There are a variety of different shapes and sizes of these nets, but the basic design would be funnel shaped with a sample jar attached at the small end of the funnel. The plankton net would be towed behind the research vessel at varying depths for a set period of time. All plankton collected would be analyzed via a microscope. According to the text Identifying Marine Phytoplankton (1997) there are at least 14,000 species of phytoplankton and some suggest as many as 120,000. Most of these, 12,000-100,000, are diatoms, one of five classes of marine phytoplankton. The majority of the phytoplankton fall into one of two class, the diatoms and the dinoflagellates.
Diatoms are typically single celled algae encased in a clear silica shell called a frustule. The frustule can come in a variety of shapes, with or without spines, and many resemble snowflakes – their quite beautiful. They are found in the bay and Gulf in great numbers, as many as 40,000,000 cells / cup of seawater. They are the dominate phytoplankton in colder waters and are most abundant near upwellings. These are the “grasses of the sea” and the base of many marine food webs. When diatoms die, their silica shells sink to the seafloor forming layers of diatomaceous earth, which is used in filters for aquariums and oxygen mask in hospitals.
Dinoflagellates differ from diatoms in that they produce two flagella, small hair-like projections from the algae that are used for generating water currents and movement. Their shells are not silica but layers of membranes and are called thecas. Some membranes are empty and others contain different types of polysaccharides. Dinoflagellates are more abundant than diatoms in warmer waters. There are about 2000 species of them. One type, Noctiluca, are responsible for what locals call “phosphorus” or bioluminescence. These dinoflagellates produce a blue-ish light when disturbed. Many see this when walking the beach at night. Their footprints glow for a few seconds. At night, boaters can see this as their prop wash turns the dinoflagellates in the water column. The bioluminescence is more pronounced in the warm summer months and is believed to be defense against predation. The light is referred to as “cool” light in that the majority of the energy is used in producing light, not lost as heat as with typical incandescent bulbs – hence the birth of the LED light industry.
The dinoflagellate Karenia brevis.
Photo: Smithsonian Marine Station-Ft. Pierce FL
Several dinoflagellates produce toxins as a defense. Some generate what we call red tides. In the Gulf of Mexico, Karenia brevis is the species most responsible for red tide. Red tides typical form offshore and are blown into coastal areas via wind and currents. They are common off the coast of southwest Florida but occur occasionally in the panhandle. Many local red tides are actually formed in southwest Florida and pushed northward via currents. Red tides are known to kill marine mammals and fish, as well as closing areas for shellfish harvesting.
Like true plants, phytoplankton conduct photosynthesis. Between the diatoms and dinoflagellates, 50% of the planet’s oxygen is produced. These are truly important players in the ecology of both the open Gulf and local bays.
References
Annett, A.L., D.S. Carson, X. Crosta, A. Clarke, R.S. Ganeshram. 2010. Seasonal Progression of Diatom
Assemblages in Surface Waters of Ryder Bay, Antarctica. Polar Biology vol 33. Pp. 13-29.
Hasle, G.R., E.E. Syvertsen. 1997. Identifying Marine Phytoplankton. Academic Press Harcourt Brace and
Company. San Diego CA. edited by C.R. Tomas. Pp. 858.
Steidinger, K.A., K. Tangen. 1997. Identifying Marine Phytoplankton. Academic Press Harcourt Brace and
Company. San Diego CA. edited by C.R. Tomas. Pp. 858.
by Carrie Stevenson | Nov 3, 2017
Red mangrove growing among black needlerush in Perdido Key. Photo credit: Carrie Stevenson, UF IFAS Extension
Discovering something new is possibly the most exciting thing a field biologist can do. As students, budding biologists imagine coming across something no one else has ever noticed before, maybe even getting the opportunity to name a new bird, fish, or plant after themselves.
Well, here in Pensacola, we are discovering something that, while already named and common in other places, is extraordinarily rare for us. What we have found are red mangroves. Mangroves are small to medium-sized trees that grow in brackish coastal marshes. There are three common kinds of mangroves, black (Avicennia germinans), white (Laguncularia racemosa), and red (Rhizophora mangle).
Black mangroves are typically the northernmost dwelling species, as they can tolerate occasional freezes. They have maintained a large population in south Louisiana’s Chandeleur Islands for many years. White and red mangroves, however, typically thrive in climates that are warmer year-round—think of a latitude near Cedar Key and south. The unique prop roots of a red mangrove (often called a “walking tree”) jut out of the water, forming a thick mat of difficult-to-walk-through habitat for coastal fish, birds, and mammals. In tropical and semi-tropical locations, they form a highly productive ecosystem for estuarine fish and invertebrates, including sea urchins, oysters, mangrove and mud crabs, snapper, snook, and shrimp.
Interestingly, botanists and ecologists have been observing an expansion in range for all mangroves in the past few years. A study published 3 years ago (Cavanaugh, 2014) documented mangroves moving north along a stretch of coastline near St. Augustine. There, the mangrove population doubled between 1984-2011. The working theory behind this expansion (observed worldwide) is not necessarily warming average temperatures, but fewer hard freezes in the winter. The handful of red mangroves we have identified in the Perdido Key area have been living among the needlerush and cordgrass-dominated salt marsh quite happily for at least a full year.
Key deer thrive in mangrove forests in south Florida. Photo credit: Carrie Stevenson, UF IFAS Extension
Two researchers from Dauphin Island Sea Lab are planning to expand a study published in 2014 to determine the extent of mangrove expansion in the northern Gulf Coast. After observing black mangroves growing on barrier islands in Mississippi and Alabama, we are working with them to start a citizen science initiative that may help locate more mangroves in the Florida panhandle.
So what does all of this mean? Are mangroves taking over our salt marshes? Where did they come from? Are they going to outcompete our salt marshes by shading them out, as they have elsewhere? Will this change the food web within the marshes? Will we start getting roseate spoonbills and frigate birds nesting in north Florida? Is this a fluke due to a single warm winter, and they will die off when we get a freeze below 25° F in January? These are the questions we, and our fellow ecologists, will be asking and researching. What we do know is that red mangrove propagules (seed pods) have been floating up to north Florida for many years, but never had the right conditions to take root and thrive. Mangroves are native, beneficial plants that stabilize and protect coastlines from storms and erosion and provide valuable food and habitat for wildlife. Only time will tell if they will become commonplace in our area.
If you are curious about mangroves or interested in volunteering as an observer for the upcoming study, please contact me at ctsteven@ufl.edu. We enjoy hearing from our readers.
