As far as familiarity goes – everyone knows about worms. As far as seeing them – these are rarely, if ever seen by visitors to the northern Gulf. Most know worms as creatures that live beneath the sand – out of sight and doing what worms do. We imagine – scanning the landscape of the Gulf – millions of worms buried beneath the sediment. For some this may be quite unnerving. Worms are sometimes “gross” and associated with an unhealthy situation. You might say to your kids “don’t dig in the sand – you might get worms”. Or even “don’t drink the water – you might get worms”. But the reality of it all is that there are many kinds of worms in the northern Gulf, and many are very beneficial to the system. We will look at a few.
The common earthworm. Photo: University of Wisconsin Madison
Flatworms are the most primitive of the group. As the name implies, they are flat. There is a head end, often with small eyespots that can detect light, but the mouth is in the middle of the body and, like the jellyfish, is the only opening for eating and going to the restroom. There are numerous species of flatworms that crawl over the ocean floor feeding on decayed detritus, many are brightly colored to advertise the fact they are poisonous – or pretending to be poisonous. And then there are species that actually swim – undulating through the water in a pattern similar to what we do with our hand when we stick it out the window driving at high speed.
But there are parasitic flatworms as well. Worms such as the tapeworm and the flukes are more well known than the free-swimming flatworms just described. These are the worms people become concerned about when they hear “there are worms out there”. And yes – they do exist in the northern Gulf. But what some people may not realize is that these internal parasites are adapted for the internal environment of their selected host and cannot survive in other creatures. There are human tapeworms and flukes, but they are not found in the sands of the Gulf.
The human liver fluke. One of the trematode flatworms that are parasitic. Photo: University of Pennsylvania
As the name implies, roundworms are round – but they differ from earthworms in that their bodies are smooth and not segmented as earthworms are. One group of roundworms is well known in the agriculture and horticulture world – nematodes. Some nematodes are also known for being human parasites – again, creating some concern. These include the hookworm and pinworm. Roundworms can be found in the sediments by the thousands – sometimes in the millions. The abundance of some species are used as an indicator of the health of the system – the more of these particular type of roundworms, the more unhealthy the system – again, a cause of concern for some when they see any worm in the sand.
The round body of a microscopic nematode. Photo: University of Nebraska at Lincoln
We will end with the segmented worms – the annelids. This is the group in which the familiar earthworm belongs. Though earthworms do not exist in the northern Gulf, their cousins – the polychaetae worms – are very common. Polychaetas are much larger, easier to see, and differ from earthworms in that they have extended legs from each segment called parapodia. Some polychaetas produce tubes in which they live. They will extend their antenna out to collect food. Many of these tubeworms have their tubes beneath the sand and we only see them (rarely) when their tentacles are extended – or when they extend a gelatinous mass from their tubes to collect food. But there is a type of tubeworm – the sepurlid worms – that produce small skinny calcium carbonate tubes on the sides of rocks on rock jetties, pier pilings, and even marine debris left in the water. This is also the group that the leech belongs to. Though leeches are more associated with freshwater, there are marine leeches. These are rarely encountered and do not attach to humans as their freshwater cousins do.
Diopatra are segmented worms similar to earthworms who build tubes to live in. These tubes are often found washed up on the beach.
Though we may be “creeped-out” about the presence of worms in the northern Gulf of Mexico, they are none threatening to us and are an important member of the marine community cleaning decaying creatures and waste material from the environment. We know they are there, and glad they are there.
Spring is a time of change. Spring brings changes in our waters as well. Some of these changes are visible on top of the water and cause concern among water users and viewers. Let’s dispel some of these concerns associated with the spring season.
Sometimes, water users and viewers notice what appears to be oil floating on top of the water. Could this be oil? Potentially. Could this not be oil? Most likely. Plants perish, and decomposition occurs, typically during the spring and fall seasons of the year. Much of the decomposition that happens in spring is associated with the initial growth and development of plants. Bacteria living in the soils within and around the water break down the perished plants. These bacteria are decomposing the old plant material. The waste product produced from the bacteria’s decomposition of the old plant material is an oily substance. The oily sheen on the water is a waste product of bacteria. Frequently, the oil accumulates in portions of water where there is little to no water movement. As the decomposition process completes, the oily sheen should lessen over the next few days to weeks. This bacteria-produced oil from decomposition is a natural process.
Petroleum-based oil seen on water is not a natural process. Petroleum-based oil could enter water from various sources, such as but not limited to transportation spills, stormwater runoff, and improper disposal of products containing oil. Like the oily substances produced by bacteria during decomposition, petroleum-based oils will float on top of the water and accumulate where there is little to no water movement.
Here are some tips to identify the difference between oils in water:
Bacteria-produced Oil
Petroleum-based Oil
Appearance
Oily sheen on top of water with little to no difference in color throughout
Oily sheen on top of water with differences in color throughout (may even appear like a rainbow)
Touch
(use a stick)
When disturbed, the sheen breaks away easily with irregular patterns and does not reform. The oil will not adhere to the stick.
When disturbed, the sheen swirls, elongates, and does reform. The oil may adhere to the stick.
Odor
(not always present)
Strong organic, musty, or earthy smell.
Volatile organic compounds (VOCs) smelling like gasoline or diesel fuel.
Another sheen on our waters that is frequent during Florida’s springtime is pollen. Pine, tree, and weed pollen accumulate on top of water, especially in areas with little or no water movement. If the sheen on the water is yellow, orange, or sometimes white, this is most likely due to pollen. Think about how pollen shows on a car in Florida during spring…our waters can show the same to some extent.
Let’s give it a try! See if you can identify the sheens in water in each photo—answers at the bottom of the page.
Photo 1
Photo 2
Photo 3
Photo 4
Photo 5
Photo 6
Keep Scrolling For Answers!
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PHOTO ANSWERS: Photo 1: Bacteria-produced oil sheen. Photo 2: Pollen sheen. Photo 3: Petroleum-based oil sheen. Photo 4: Pollen sheen. Photo 5: Petroleum-based oil sheen. Photo 6: Mixture of bacteria-produced oil and pollen sheen. Note all photos were obtained from Adobe Stock Photos.
Many of the creatures we have written about in this series to this point are ones that very few people have ever heard of. But that is not the case with jellyfish. Everyone knows about jellyfish – and for the most part, we do not like them. These are the gelatinous blobs with trailing tentacles filled with stinging cells that cause pain and trigger the posting of the purple warning flags at the beach. They are creatures that many place in the same class as mosquitos and venomous snakes – why do such creatures even exist. But exist they do and there are plenty in the northern Gulf – more than you might be aware of.
Jellyfish are common on both sides of the island. This one has washed ashore on Santa Rosa Sound.
The ones we are familiar with are those that are gelatinous blobs with trailing tentacles – called medusa jellyfish. These include the common sea nettle (Chrysaora). Sea nettles have bells about 4-8 inches in diameter (though they are larger offshore). The bell has extended triangle markings that appear red and tentacles that can extend several feet beneath/behind the bell. The tentacles are armed with nematocyst – cells that contain a coiled “harpoon” which has a drop of venom at the tip. They use these nematocyst to kill their prey – which include small fish, zooplankton, and comb jellies. But they are also triggered when humans bump into them producing a painful sting. Their prey is digested in a sack-like stomach called the gastrovascular cavity and waste is expelled through their mouth, because they lack an anus. Though these animals can undulate their bells and swim, they are not strong enough to swim against currents and tides – and thus are more planktonic in nature.
Another familiar jellyfish is the moon jelly (Aurelia). These are the larger, saucer shaped jellyfish that resemble a pizza with a clover leaf looking structure in the middle. They can reach 24 inches in diameter across the bell which is often seen undulating trying to swim against the current and tide. Their tentacles are very short – extending from the rim of the bell – but there are four large oral arms that are quite noticeable. The oral arms also possess nematocyst for killing prey. Their prey includes mostly zooplankton and other jellyfish. Like their cousins the sea nettles, moon jellies are planktonic in nature and are often found washed ashore during high energy days. Some say the pain from this jellyfish is minimal, others feel a lot of pain.
The remnants of moon jellyfish near a ghost crab hole. Photo: Rick O’Connor
Though there are many others, our final familiar jellyfish would be the Portuguese man-of-war (Physalia). If you have never seen one, you most likely have heard of them. These are easy to identify. They produce a bluish colored gas filled balloon like sack that floats on the surface and extends above water to act as a “sail”. This gas filled sack is called a pneumatophore and helps move the animal across the Gulf. Extending down from this pneumatophore are numerous purple to blue to clear colored tentacles. You would think the pneumatophore would be the bell of the jellyfish and the tentacles of similar design as to the ones we mentioned above – but that would be incorrect. The tentacles are actually a colony of small polyp jellyfish connected together – it is not a true jellyfish (as we think of them). The stomachs of these individual polyps are connected and as one kills and feeds, the food passes throughout the colony to nourish all. In order to feed the whole colony, you need larger prey. To kill larger prey, you need a more toxic venom, and PMOW do have a very strong toxin. The sting from this animal is quite painful – though rare, it has even killed people. This jellyfish should be avoided. As with other jellyfish, they often wash ashore, and their stinging cells can still be triggered. Do not pick them up.
There is another form of jellyfish found here that is not as well known. They may be known by name, but not as jellyfish. They are called polyp jellyfish and instead of having an undulating bell with tentacles drifting behind, they are attached to the seafloor (or some other structure) and extend their tentacles upward. They look more like flowers and do not move much. Examples of such jellyfish include the tiny hydra, sea anemones, and corals. As with their medusa cousins, they do have nematocysts in their tentacles and can provide a painful sting, though some produce a mild toxin, and the sting is not as painful as other jellyfish. Many of these polyp jellyfish are associated with coral reefs. Though coral reefs are common in tropical waters, they do occur to a lesser extent in the northern Gulf.
The polyp known as Hydra. Photo: Harvard University.
We will complete this article with a group of jellyfish that do not have nematocysts and, thus, do not sting – the comb jellies. Though many species of comb jellies have trailing tentacles, the local species do not. When I was young, we called them “football jellyfish” because of their shape – and the fact that you could pick them up and throw them to your friends. I have also heard them called “sea walnuts” because of their shape. A close look at this jellyfish you will see eight grooves running down its body. These grooves are filled with a row of cilia, small hairlike structures that can be moved to generate swimming. The cilia move in a way that they resemble the bristles of a comb we use for combing our hair. You have probably taken your thumb and run it down your comb to see the bristles bend down and back into position – sort of like watching the New York Rockettes high kick from one end of their line to the other – this is what the cilia look like when they are moving within these grooves – and give the animal its common name “comb jelly”. Since they do not have nematocysts, they are in a different phylum than the common jellyfish. They feed on plankton and each other and can produce light – bioluminescence – at night.
Though not loved by swimmers in the northern Gulf, jellyfish are interesting creatures and beautiful to watch in public aquaria. They have their bright side.
Comb jellies do not sting and they produce a beautiful light show at night.
Everyone has heard of sponges, and many know they grow in the ocean. But fewer are aware that sponges are actually animals. When we think of animals, we think of something that crawls around seeking food and laying eggs periodically. Sponges are not like that. They are “blob” looking creatures sitting on the ocean floor. At first glance you might call them fungi, or maybe some weird form of algae – but they are animals, the simplest form of animal life on the planet.
A vase sponge. Florida Sea Grant
What makes them animals is the lack of cell walls and chlorophyll. Fungi also lack chlorophyll, but they do possess cell walls – so, are classified differently. Because animals lack chlorophyll they cannot produce their own food – and must consume creatures in order to obtain their needed sugars. So, what do sponges “hunt”? They feed on plankton in the water column – many of the microscopic creatures we have already written about in this series.
The sponge body is basically a colony of individual ameboid and flagellated cells. These small cells attach to the substrate and begin to reproduce sexually and asexually to form the colony. As they grow, they form a series of pores found on the exterior of the mass. The flagellated cells – called collar cells – move their flagella to generate a current. This current draws in seawater – along with its plankton – where the colony, both the flagellated and ameboid cells, feed. As the colony grows the exterior pores lead to channels and canals where the cells live and eventually empty into a larger cavity known as the atrium. Here the water moves upward and exits the sponge through an opening called the osculum. Waste from feeding exits the sponge through the osculum as well.
The anatomy of a sponge. Flickr
As the colony grows it is supported by a series of tiny spike-like structures called spicules. Spicules are made of different materials and are one method of separating and classifying the different sponges. One group of sponges are known as the calcareous sponges – their spicules are made of calcium carbonate and are rough to the touch. Another group are known as the “glass” sponges – their spicules are made of silica and are sharp-prickly to the touch. A third group are known as the bath sponges – their spicules are made of a softer material called spongin. It is this third group that was used for centuries for both bathing and washing.
Glass sponges are beautiful. Photo: NOAA
These simple creatures play an important role in the ecology of marine systems. As filter feeders, they remove material from the water column improving water clarity and quality. They remove excess nitrogen and play a role in the carbon cycle. They provide habitat for numerous small marine creatures where they can hide from predators and find food.
Sponges need a hard substrate to grow on and thus are more abundant in the coral reefs of south Florida. Locally I have only found them in the seagrass beds. But there they do play the same ecological role you would find them doing on coral reefs. They are one of the less encountered creatures of the northern Gulf.
Striped burrfish are fascinating to watch in the wild and in aquariums. Photo credit: Carrie Stevenson, UF IFAS Extension
I have a vivid memory of snorkeling the seagrass beds around Port St. Joe when I was an undergraduate marine biology student. Our field research lab involved completing a visual fish survey, using waterproof dive slates and pencils to record the number and species of any fish that swam past us. I was conducting my survey fairly rigorously until a 6” long striped burrfish (Chilomycterus schoepfi) moved into my field of vision. It hovered in front of me, looking over with its gigantic puppy-like eyes, and proceeded to gently nibble on everything in sight. There are very few fish one might characterize as “cute,” but this charismatic little guy was adorable. Completely abandoning the task at hand, I stopped counting other fish and proceeded to slowly swim behind this little burrfish as it fed and swam throughout the grass bed. It was completely unfazed by my presence—I stopped to watch while it ate, then used my flippers to slowly navigate behind when it started moving again. I must have followed this fish for 30 minutes, simply observing its behavior. I could have sworn it looked back and me and signaled, “come on!” with a fin every time it moved to another location. I’ve snorkeled countless times since then, but bonding with this little fish was such a singular experience that I can visualize it clearly almost 30 years later.
A Southern puffer (left) and striped burrfish (right) in side-by-side comparison. Photo credit: Carrie Stevenson, UF IFAS Extension
Hence, I’ve always had a soft spot for the striped burrfish. We occasionally pull juveniles up in a seine when taking groups out in the field, and they often puff up in response to the shock of being temporarily captured. Frequently misidentified as their Tetradont relatives, the Southern puffer (Spheroides nephelus), the burrfish is similar in size and habitat. However, they are fairly easy to differentiate by their dorsal color patterns. As the name implies, striped burrfish have brown stripes, while puffers have more of a mottled pattern. Both species have bright white countershading on their bellies (aka “ventral” side), helping them blend in with the sky above when viewed from below by potential predators. They also utilize similar defense mechanisms, filling their bodies with air or water when threatened so they physically expand, appearing bigger and more difficult to fit into a larger fish’s mouth. Burrfish also have rigid spines that point out from their bodies when in self-defense mode. This adaptation makes them more complicated to digest for a would-be attacker. Many members of this Order of fishes produce a dangerous neurotoxin, further deterring predatory attacks.
Striped burrfish expand their bodies to twice normal size when threatened. Photo credit: NOAA
To the human observer, it’s anything but intimidating to see a fish transform into a ping pong ball with fins, but the strategy must work because there are around 120 species of puffers and porcupinefish in the Order Tetraodontiformes that use this technique.
As young burrfish mature, their front teeth fuse into a tough “beak,” which they use to break through the shells of their prey. As I experienced while snorkeling, burrfish are slow swimmers, using their wide terminal mouths and large jaws to nibble on shellfish, sea urchins, and barnacles. Their characteristic body shape is boxy, built not for speed but to cruise reefs and grassbeds. Armored with spikes, poison, and the element of surprise, striped burrfish can afford to take their time and relax in the water.
As we mentioned when we began writing about seaweed, seaweed and seagrass are very different. Seagrasses are true plants in the sense that they have an internal vascular system that runs water and other material throughout the plant. Like the artery and veins of animals – they are called xylem and phloem. Water in the soil is diffused through the tissue of the roots into the xylem, which moves the water up through the stem to the leave where it is used in photosynthesis. The sugars produced by photosynthesis are moved through back down into the plant by traveling through the phloem. Seagrasses produce small flowers that are pollinated by dispersing the pollen in the currents and by small invertebrates, such as amphipods and polychaetae worms. Seagrasses are true plants.
Grassbeds are also full of life, albeit small creatures. Photo: Virginia Sea Grant
Believed to have originated as land plants, today there are about 72 species of seagrasses found around the world; seven are found in Florida; five found in the Pensacola Bay system. Though found in some open ocean systems, most seagrass beds are found in the protected waters of the estuary. They thrive in areas with low wave energy and clear water. They help stabilize the shoreline and remove pollutants from the water column. There is an abundance of marine creatures who use the seagrass beds as either a source of food, or habitat. It has been determined that at least 80% of the commercially important finfish and shellfish use seagrass beds for at least part of their life cycle.
Three of the five local species can be found in Santa Rosa Sound. Shoal grass (Halodule) has a flat blade but is very thin, between 2-3mm wide. Because it is so narrow, less surface area, it can tolerate waves better than turtle grass, and thus lives closer to the shoreline. Within the shoal grass you can find a variety of small baitfish feeding, as well as blue crabs and hermit crabs scavenging. But it does not provide the hiding spaces that the wider blade turtle grass does.
Shoal grass. One of the common seagrasses in Florida. Photo: Leroy Creswell
Turtle grass (Thalassia) have blades that are 10mm wide. These wider blades do not handle the waves as well and thus turtle grass grows in deeper waters further off the beach. How deep they can grow is a function of the amount of sunlight reaching the bottom. In the Florida Keys turtle grass has been found at depths of 30 feet. Locally maximum depths are more likely near 10 feet. The wide blades of this grass provide surface area for a variety of small algae and invertebrates to attach. These epiphytes and epizoids are a major player in the food web of seagrass beds. Numerous invertebrates and fish feed on this “scum layer” found on the grass blades. The grazers attract low level predators such as pinfish, puffers, and sea horses. These in turn attract larger predators such as rays, speckled trout, and flounder. Manatees and sea turtles can be found here as well as sharks and the occasional bottled nose dolphin.
The wide blades of turtle grass provide habitat for a variety of epibiota. Photo: UF IFAS
Manatee grass (Syringodium) resembles shoal grass, but the blade is round instead of flat. It can be found forming its own patches or dispersed within the other species. The abundance of this species seems to be increasing in local waters.
Gracilaria is a common epiphytic red algae growing in our seagrass beds. Photo: Rick O’Connor
Widgeon grass (Ruppia) is a common seagrass found in the upper portions of our estuary. Though it can live in the higher salinities near Pensacola Beach, it can also tolerate the lower salinities of the upper bays and thus, with less competition, does very well here. It also resembles shoal grass but differs in that the blade branches as it grows. Like all seagrass beds, widgeon grass can support a lot of marine creatures and increase the overall biodiversity of the bay.
The branched leaves of the widgeon grass.
Since the 1950s the northern Gulf coast has witnessed a decline in seagrass acreage. The decline was caused by a combination of factors. One, increased sedimentation with stormwater and development. In some cases, the seagrass was literally buried and in others the sediment decreased water clarity which decreased needed sunlight. Two, shrimp trawls. At one time shrimpers could pull their trawls through the grass to catch shrimp. This ripped and destroyed much of the habitat and the state closed shrimping in all grassbeds. Three, seawalls. Waves reflecting off the seawalls increased the wave energy within the Sound to a point that seagrass could not tolerate it. The landward edge of many grassbeds began to retreat from these seawalls reducing the overall acreage of the seagrass bed. Four, prop scars. Boats running through the grassbeds will cut deep scars in the grass that reach the sand beneath. It can take up to 10 years for the system to restore itself. And, with more boats out there, there are more scars. Five, the increase in the mass of drift algae settling on the grasses. These drift algae populations increase with increased nutrients being discharged into the Sound from land-based run-off. Drift algae cover the grasses decreasing their ability to absorb much needed sunlight.
Monitoring in recent years has shown that our seagrasses are trying to restore themselves and some beds have increased in size during the last couple of decades. Monitoring continues.
