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.
If green algae are difficult to find in the northern Gulf because most prefer freshwater, and rocky shorelines, brown are difficult because the group prefers colder water, as well as rocky shorelines – but we do have some here.
Brown algae get their color because the ratio of photosynthetic pigments in their cells favors the xanthophylls – which produces a yellow-brown color. Like most macroscopic algae, they attach to the hard bottom using a holdfast and then extend their stipe and blade into the water column to absorb light. One group of brown algae are the largest of all seaweeds, the giant kelp Macrocystis. In the nutrient rich waters off California this seaweed will grow up to one foot a day and can reach heights of up to 175 feet tall. Since seaweeds do not possess true stems, or any wood, what holds this giant seaweed up are air filled bladders called pneumatocysts – structures found on other brown algae and are unique to the group.
The largest, fastest growing seaweed – giant kelp. Photo: NOAA
Many species are popular with seafood dishes, such as Nori. Others produce a carbohydrate known as algin that is extracted and used as a food additive. You may have heard “ice cream has seaweed in it”. What it actually has is algin. This carbohydrate acts as a smoothing agent for products. Solids should be solid – like frozen ice cream – but, as you know, we do not want our ice cream solid. So, for a period of time, the algin keeps the ice cream smooth and creamy. Algin is used in toothpaste, lipstick, and icing on cakes for the same reason.
But along the northern Gulf coast, brown algae are not common. Despite preferring marine waters, they do prefer colder water and, like most seaweeds, need a hard substrate to attach their holdfast. But by exploring our local rock jetties and seawalls we do find some. One in particular is the common rock weed – Dictyota. This sessile seaweed branches out and resembles small trees. But the most common, and most recognized brown algae on our coast is Sargassum.
The brown algae Dictyota. Photo: NOAA
Sargassum has found a way to deal with an environment where little hard bottom is present. Using the characteristic air bladders allows it to float at the surface to absorb the much needed sunlight. Because of this ability to float, Sargassum can be found all across the oceans, and often form large mats that cover miles of open sea and extend several feet down. It actually creates a whole new ecosystem in the middle of the sea. The major ocean currents rotate like a hurricane and, like a hurricane, the center – the “eye” – is calm. Within this calm huge mats of Sargassum collect. The ancient sailors called the center of the Atlantic Ocean the “Sargasso Sea”. But as the large currents spin, sections of this large mat “spin off” and are pushed across the ocean. Much of it heads towards Florida, the Gulf, and eventually to the northern Gulf.
If you grab a mask and snorkel and swim within the Sargassum before it reaches the waves, you will encounter a whole community of creatures that live here. Sargassum crabs, Sargassum fish, and even seahorses live within it. There are shrimps, worms, and even mollusks. When baby sea turtles head offshore after hatching, many seek out these Sargassum mats to both hide in, and feed within. They will spend their youth here before returning back to shore for different prey.
However, once many of these creatures sense the waves breaking, and now the mat is about to wash ashore, they will move to mats further offshore. That said, picking through the Sargassum on the beach may still yield some interesting creatures.
Sargassum.
In recent years the amount of Sargassum washing ashore has increased and become problematic – particularly in southeast Florida and the Florida Keys. At times, mounds three feet high have been found. Those communities are working on methods to deal with the problem. But here locally, these mats are a new world to explore.
Members of the seaweed group Rhodophyta – the red algae – prefer warmer marine waters. Though the diversity and abundance of seaweeds in the northern Gulf is low due to unsuitable substrate for them to attach to, the red algae may be the most diverse group we have.
One publication produced by Florida Gulf Coast University1 lists 20 different species of seaweeds in our state; 13 (65%) are red algae. Most of them a thin bladed. Some are smooth and others have “hooks” along their blades. Some species are drift algae – drifting in the water and settling on seagrasses similar to how Spanish moss settles on oak trees. Most are found in south Florida, due to the hard limestone bottom found there, but there are species in our area attached to rock jetties and seawalls.
We also have drift algae here. Large clumps of red algae known as Gracilaria are found atop seagrasses. Though they provide suitable habitat for fish and invertebrates, but they are not so good for the seagrass. These drift algae cover the grass not allowing the much needed sunlight. They also compete with our seagrasses for available nutrients in the water column. Volunteers in our local seagrass citizen science monitoring project – Eyes on Seagrass – record whether drift algae are present when they are monitoring as well as noting whether it was abundant or not. We have noticed that it may be abundant in one season and not another. We have also noticed that when it is abundant in Santa Rosa Sound it may not be present in Big Lagoon – and vice versa.
Gracilaria is a common epiphytic red algae growing in our seagrass beds. Photo: Rick O’Connor
Though there is no commercial use for the red algae in our area, there are many species popular in the seafood industry. Nori is a popular seaweed used in Sushi dishes and Dulce is said to help with sea sickness.
Nori is a popular red algae in the seafood industry.
In the last three posts we have introduced you to the seaweeds of the northern Gulf. Though neither diverse nor abundant, they are present and do play an important role in the ecology of our area. I recently witnessed mallard ducks feeding off of red algae on a rock jetty on Pensacola Beach. In our next article we will turn our attention to the only group of true submerged marine plants in our area – the seagrasses.
