When snorkeling the grassbeds of the Florida panhandle encountering a reptile has a low probability, but it is not zero. Of all the reptiles that call this part of the state home, few enter marine waters and most of those are very mobile, moving up and down the coast heading from one habitat to another. In fact, there are no marine reptiles that would be considered residents of our seagrasses, only transients.
The one species that you might encounter is the green sea turtle (Chelonia mydas). This is the largest of the “shelled” sea turtles and has a vegetarian diet. With a serrated lower jaw, they can be found grazing in the seagrass beds feeding on both the grasses and the species of algae found there. The carapace length of these large reptiles can reach four feet and they can weigh up to 400 pounds. Their coloration is similar to that of the loggerhead sea turtle (Caretta caretta) but their heads are smaller and there are only two large scutes between the eyes rather than the four found in the loggerheads. The colors of the skin and shell have shades of brown, yellow, orange, and some black and can be quite beautiful. The name “green” sea turtle comes from the color of their internal fatty tissue. Feeding on a diet of seagrasses, it becomes green in color, and this was discovered by early fishermen who hunted and consumed this species. It is the one used most often in what is called turtle soup and is actually farmed for this dish in other countries.
Like all sea turtle species, they are born on the Gulf side of our barrier islands. If they successfully hatch, they work their way to the open water and spend their early years in the open sea. Some have been associated with the mats of Sargassum weed floating offshore, feeding on the variety of small invertebrates that live out there. They will also nip at the Sargassum itself. As juveniles they will move back into the coastal estuaries where they begin their vegetarian lifestyle. As adults they will switch time between the open sea and the grass filled bays. Once unfortunate side effect of feeding in our grassbeds is the frequency of boat strikes. There are tens of thousands of motored vessels speeding through our grassbeds and the turtles surfacing for air can be targets for them. Our hope is that more mariners are aware of this problem and will be more vigilant when recreating there.
Another turtle who IS a resident of the estuary is the much smaller diamondback terrapin. Though terrapins much prefer salt marshes they will enter seagrass beds, and some spend quite a bit of time there. Terrapins prefer to feed on shellfish so, moving through the grassbeds it is the snails and bivalves they seek. Because of their size they feed on the smaller mollusk. A typical terrapin will have a carapace length of about 10 inches and may weigh two pounds. They will take small crabs and shrimps when the opportunity is there, and they are known to swim into submerged crab traps seeking the bait. Unfortunately, being air breathing reptiles, they will drown after becoming entrapped. It is now required that all recreational crab traps in Florida have bycatch reduction devices (BRDs) on each of the funnel openings to reduce this problem. Many studies, both here in Florida and elsewhere, have shown these BRDs do not significantly reduce crab catch and so you can still enjoy crabbing – just not while catching terrapins. Encountering one snorkeling would be a very rare event, but – particularly in the eastern panhandle – has happened.
A third reptile that has been seen in our grassbeds is the American alligator (Alligator mississippiensis). Preferring freshwater systems, encounters with alligators in an open seagrass bed are rare, but do happen. There are plenty of freshwater ponds on some of our barrier islands that the alligators will use. They have been seen swimming out into the seagrass beds and often will cross the bay, or Intracoastal Waterway, to mainland side. They have also been seen swimming near shore in the Gulf of Mexico. Though they can tolerate saltwater, they have a low tolerance for it and do not spend much time there.
Alligators are top level carnivores feeding on a variety of wildlife. Like most predators, they tend to seek and capture the easiest prey. Most often these are fish, reptiles, or small mammals. But they will take on large birds or deer if the opportunity presents itself. Despite their natural fear of humans, they have taken pets and also have attacked humans.
Having only canines in their mouths, they must grab the prey and swallow it. Lacking molars, they cannot chew. So, more often than not, they select prey they can swallow whole. If they do grab a larger animal, they are known to drown the creature in what has been termed the “death role” and cache it beneath the water under a log (or some structure) where it will soften to a point where they can cut small pieces and swallow it. All of the alligators I have seen in our grassbeds were definitely heading somewhere. They were not spending time there. After heavy rains the salinity may drop enough to where they can tolerate being out there longer and encounters could increase. But they are still rare.
I will mention here that there are several species of snakes that, like the alligator, are swimming from one suitable habitat to another – crossing the seagrass in route. All snakes can swim and encounters in brackish water are not unheard of. I have several photos of diamondback rattlesnakes (Crotalus adamanteus) swimming across the Intracoastal Waterway between the mainland and the islands.
Encounters with reptiles are rare in our seagrass beds but pretty exciting when they do occur. There is certainly no need to fear swimming or snorkeling in our bay because they are so rare. But maybe one day you will be one of the lucky ones who does see one.
When visiting and exploring seagrass beds, most are hoping, and expecting, to see fish. As we have seen in this series, there are a lot of creatures that can be found living within a seagrass meadow, but it is the fish that get our attention and what we talk most about afterwards.
According to Hoese and Moore’s Fishes of the Gulf of Mexico; Texas, Louisiana, and Adjacent Waters, there are 497 species of fish found in the Gulf of Mexico. In my surveys of Pensacola Bay over the years, I have logged 101 of those in the estuary. I am sure there are more, but I can confirm there are at least those. Many spend all or part of their time in our seagrasses. As you seine or snorkel in the grassbeds you will notice most of them are very small. Much of this is due to the fact that the seagrasses are nursery areas for many species, and it is the young that we find here. But many are also small as adults, and the grass provides food and shelter for them. There are far too many to mention in an article like this, but let’s look at some of them.
Sardines and Anchovies
As you snorkel through the grass, or even look at it from a boat or dock, you see numerous silver colored baitfish flashing as they dart in and out of the grass. There are all sorts of silver baitfish in the seagrasses with sardines and anchovies being two of them. In my experience seining for fish, they appear to be seasonal. I did not capture them all year but when I did, I would capture a lot. These species are famous for being the ones in small tins that people consume, though there is no fishery for them here locally. Anchovies have also been considered an indicator species; their presence suggests good water quality.
Also known as silversides and glass minnows, these are one of the most common fish collected in seine nets. They are abundant year-round and are an important food source for many of the larger predators living here. Small and transparent, you do not see them while snorkeling. Their huge presence is only discovered when you pull a seine net through the grass. There are several species of them, but they are not easily identified and more often are just logged as “silversides”. They are an important member of the seagrass community.
Seahorses and Pipefish
These two fish are highly specialized for living in seagrasses. They look like grass and move very little making them hard to detect. Like silverside minnows, it is rare to see them while snorkeling but make their presence known when seining. Their bodies are covered in armor-like scales, and they have tubed mouths for “vacuuming” small invertebrates from the water column. They are very slow swimmers and have to avoid detection by blending in with the environment. And yes, it is the males that carry the eggs in their brood pouches. These are amazing fish and always bring excitement when they are captured in the net. There are two species of seahorses and seven species of pipefish found in our waters.
Often called “bull minnows” by anglers, these small fish are, at times, very abundant. There are seven species of killifish in our bays but the Gulf Killifish, Longnose Killifish, and the Bayou Killifish are the ones we most often collected.
These are common, frequently seen, fish swimming at the surface of the water. Long and needle-shaped, these fish have long snouts full of sharp teeth indicating they are one of the predators of this system. There are four species of them, and they are not easy to tell apart. They are harmless to humans unless you capture them in your net at which time they will try to bite.
Another very common fish found year-round here. This species are the ones famous for jumping while you are fishing, paddling, or just watching from the beach. Those who do not visit the Gulf coast often always ask “I just saw a fish jump!” and the reply from a local (without even looking up to see what it was) will reply “It’s a mullet”. These schooling fish can get pretty large (average length is 30 inches) and it is common to see fishermen out with their cast nets trying to catch a few. It is a popular food fish for those along the Gulf coast. Mullet fries, with beans and grits, are a way of life here. The fish are easily seen swimming and darting over the grass as you paddle by, and their young are found seasonally in seine nets. They are bottom feeders, feeding mostly on algae from the grass blades. There are actually two species, the white and the striped mullet. The striped mullet, also known as the black mullet, is the one most often sold in the seafood markets.
Drums and Croakers
With 18 species within this family, this is the largest family of inshore fish in the Gulf. Growing up along the panhandle people learn quickly about croakers. Back in the day when gill nets were used to harvest mullet, croakers were a common catch as well, and often consumed. Today they are still sought by some shore-based anglers and juveniles are common in seine nets. The species I most often captured were the spot and Atlantic croaker. Spot croakers were common year-round, Atlantic croakers were more seasonal.
Drums are larger members of this family. There are several species more associated with sandy bottoms and the shoreline of the Gulf, many of these are called whiting, but the red drum (redfish) and black drum can be found in the grassbeds. Redfish are particularly common here and one of the reasons many anglers get out of bed in the morning. They are very popular sportfish across the region. Black drums are not found as often, and like being around pilings and structures that offer certain foods they prefer. Both species can get quite large. Redfish average 5 feet while black drums can reach an average of 3 feet.
All of the fish in this family are famous for their “croaking” “drum” sounds they make using their swim bladder, and it is rare not to capture at least one kind in a seine net.
Spotted Seatrout; Speckled Trout; “Specks”
There is no “trout family” in the fish world. Most freshwater trout are members of the salmon family while the marine versions are members of the drum/croaker family. This is the case with the famous speckled trout – or speck. There are white trout and silver seatrout in this family, and all are sought after by anglers, but it is the speckled trout that is most associated with seagrasses, most sought after by anglers, and is one of the top predators in this system. They reach an average length of 4 feet.
Pinfish and Sheepshead
From my experience both snorkeling and seining the grasses, I would say – hands down – that pinfish is the most common species found in our grasses. For many young anglers this is the first fish they ever catch. You can see them easily while snorkeling and they are the most numerous species in the nets throughout the year. Their huge numbers play an important role in the food web of this system. Feeding on a variety of small invertebrates in and around the grass blades, pinfish are a large part of the diet of the larger sportfish we target. Throwing cast nets and dropping pinfish traps is popular with anglers to collect this abundant baitfish for their life bait fishing efforts. They are called pinfish because of the sharp spines in their dorsal fins. These are also the fish that nip at your ankles while you are standing still in the water.
Sheepsheads are larger members of the porgy family (the ones these two species belong to). As adults sheepsheads prefer hard structure where they can use their incisors to chip away at barnacles and other shellfish, but they are sometimes found roaming the grassbeds and their young will spend their growing years hiding and feeding in the grass.
When first captured in the seine net, pigfish are often confused with pinfish – they look very similar. But a closer look at the striping/spotted pattern on their sides, and the position of their mouth, you realize you have something different. Being members of the grunt family, they also “croak” like croakers and drums – hence their common name “pigfish” – due to the grunting sounds. This helps with identifying which fish you have. Though common in the grasses, I did not catch these as frequently as pinfish and they were not as abundant.
This is a common silver baitfish that resembles the pinfish and is frequently collected in our seine nets. The mojarra is in a different family than pinfish. They lack sharp spines and incisor teeth, rather they have a sort of “vacuum” like mouth which they use to suck small invertebrates from the sand.
This is a popular sport and commercial fish from the wrecks and reefs of the Gulf of Mexico. But gags begin their lives in the seagrass beds, and we have collected medium sized individuals in our seine nets. This underscores the importance of these grassbeds to the fisheries so many love. We need to protect these systems from our activity both on land and in the water.
Another popular group with anglers, many species of jacks use these grasses as their nurseries. We most often collected juvenile lookdowns, pompano, and crevalle in our nets. At times we caught a small member of the family called a leatherjacket. These were seasonal and associated with breeding. Once again, underscoring the importance of having healthy seagrasses.
One of the creeper looking fish in the seagrass community is the Gulf toadfish (also known as the oyster dog). This monstrous looking bottom fish lives in burrows scattered around the grassbeds where they lie in wait to ambush prey. Their large mouths and sharp teeth can grab a variety of creatures, including the human finger. At times small toadfish will move into an empty can or bottle discarded by people instead of a burrow where they grow to a size they can no longer escape. It is said there may be a mild venom associated with their bite. Though no one has ever died, or been sent to the hospital, due their bite, it is painful and should be avoided.
Yes, barracuda can be found in seagrasses. But in our case, these have all been juveniles. There are three species of them, and they are not easy to tell apart. They also appeared to be seasonal in our collections. We never found them high numbers, usually one or two in a seine. But they are present.
This is another medium sized, sharp toothed, bottom dwelling predator of the grassbed community. There are seven species of them, and all have that “snake” “lizard” look to them having many sharp canine teeth. They spend their time buried in the sand waiting to ambush potential prey. Snorkelers may see them as they dart away tossing up sand when we get too close. I rarely see them snorkeling but occasionally capture them in the seine net to the delight of the students assisting.
Blennies and Gobies
These are very small fish that are almost impossible to find while snorkeling but are often collected in the seine net. They resemble the freshwater darters and, lacking a swim bladder, spend their time on the bottom. There are many species associated with rocks and artificial reefs but there are some who call the seagrasses home. They use their incisor teeth to feed on small invertebrates in and on the grasses. Being territorial, they can give a little nip to your hand. Gobies differ from blennies in that their two pelvic fins are fused together to form a sort of “cup” or “sucker disk”.
Another one of the more popular fish with students who help me seine. Everyone loves to see them inflate with either water or air into a “balloon” to make it very difficult for predators to consume them. There are eight species of puffers in the Gulf of Mexico, five of them have been captured in our seines. Most are small with little “bumps” on their bodies instead of spines. But there is the Burrfish, who is a member of a different family that is medium sized, has spines, and is very common in the grassbeds.
Our grassbeds are full of a small cousin to the triggerfish – the planehead filefish. Like triggerfish, filefish have a thick sharp spine that is found at the front of the dorsal fin – called a “trigger” on the triggerfish. The planehead filefish is a small species (nine inches average length), green to brown in color, and very common in the grassbeds; though you will probably not see one unless you catch it in a net.
Flounders and Soles
A favorite food fish for many locals, flounders spend a lot of time buried in the sand near grassbeds to ambush prey. Born with a typical fish design, early in development one of their eyes will move to the other side of the head, giving them two eyes on one side. By doing this, they have increased their binocular vision, improving their ability to judge accurate distance of the prey, and making hunting easier. They lose color on the side where the eye has left and have chromatophores (cells) on the side where the eyes are that, like octopus and squid, allow them to change colors and blend in. In our part of the Gulf, if the eyes move to the left side of the head, they are called flounders. If they move to the right, they are called soles. Soles in our part of the Gulf of small not of much interest to anglers. One small species is often collected by shrimpers who feed them to hogs. This sole can “cup” their body in defense making like a suction cup and they do this in the throat of the hogs sometimes killing them. They are called “hogchokers”. Flounders on the other hand are very popular with anglers. Some fish for them using rod and reel, others prefer gigging them at night using lanterns. There are 17 species of flounder, some reaching lengths of three feet.
Tonguefish are small flat fish with eyes on one side of their heads like flounder. They differ than that their tails come to a point and there is no caudal fin present, as there is in flounders. As mentioned, they are small – ranging from 3 to 8 inches in length. The Blackcheek tonguefish is particularly common in our grassbeds. But like so many, you will not see it unless you catch it in a net.
This is a very popular gamefish from south Florida associated with several habitats including grassbeds. Due to a process some call “tropicalization” – the movement of tropical species north due to climate change – snook are now, albeit in small numbers, reported in the Florida panhandle. This is a new species you may see while exploring or fishing out there.
There are many more species of fish found in our grassbeds we could talk about, but we will end it here. As we mentioned in the beginning, this is a group of animals that many come to the beach to find. Whether for fun or for food, finding fish makes for a good day. See how many different species you can find.
As I write this article it is mid spring, and the rays are bedding on the edges of our seagrass beds. The most common species seen is the Atlantic Stingray (Dasyatis sabina). They are often found in the sandy areas near the grass where they bury in the sand to ambush potential prey. This time of year, their numbers increase as the females are preparing to releasee their young in summer. Mating occurs in early spring and the females will deliver live young1.
According to Hoese and Moore2, there are eight families and 18 species of rays and skates found in the Gulf of Mexico. These are cartilaginous fish found in the same class as sharks but differ in that their gills slits are on the ventral side (bottom) of the body and their pectoral fins begin before the gill slits do on the side of the head. Most are depressed (top to bottom) and appear like pancakes, but not all of them. Sawfish and guitarfish appear more like sharks than rays.
Of the 18 species listed, seven can be found in the estuaries and may be associated with nearby seagrass beds. Two are species of sawfish, which are rare in our bays these days.
There are two members of the eagle ray family, the cownose ray and the eagle ray, which can be found in our bays. These resemble manta rays but differ in that they lack the characteristic “horns” of the manta (often called the Devil Ray because of them) and they do possess a bard on their tail, which manta’s do not. These are more pelagic rays spending their time swimming in the water column and hunting for buried food.
The butterfly ray does resemble butterflies in shape having wide “wing-like” fins and a very small tail. It behaves similar to stingrays burying in the sand and ambushing smaller prey.
Two of the more familiar stingrays are found in our grassbeds, the Atlantic Stingray and the Southern Stingray. The Atlantic Stingray’s disk is more round in shape while the Southern Stingray’s is more angular shaped. The Southern Stingray is larger (disk width about five feet, Atlantic disk width is about two feet) and prefers estuaries with higher salinity. The Atlantic Stingray is very common and can tolerate freshwater, thus is common throughout the bay.
Stingrays are notorious for their venomous bards and painful stings. They actually try to avoid humans and are frequently spooked by our activity fleeing as soon as they can. However, there are times when people accidentally step on one buried in the sand, or hiding in the grass at which time they will flip their whip-like tail up and over to drive their barb into your foot forcing you to move it – and you do move it – while you yell and scream. The ray then will swim away and can regrow a new barb.
The bard is a modified tooth. It is serrated on each side and there is a thin sac of venom along the flat side of the barb. When it penetrates your foot there is pain enough there. But the natural reaction of your body to an open wound is to close it, this reaction can pop the venom sac and release the toxin. The chemistry of the toxin is not life threatening to humans but is very painful. This experience is something you do want to avoid.
Like their shark cousins, rays do have rows of small teeth which they use to crush small invertebrates including shelled mollusks. They lie in the sand to ambush prey moving in and out of the seagrass beds. They possess two spiracles on the top of their heads which provide water to the gills when they are lying on the seafloor or buried in it.
Like sharks, males can be identified by the two claspers associated with the anal fin and the females usually have two uteri where the young develop. In skates, and some other rays, the young are deposited into the environment within a hardened egg case often called a “mermaids purse”. We see these washed ashore in the beach wrack. Young stingrays usually develop within the female and are born “live” in summer.
Though there is fear of this animal from some seagrass explorers they are a small threat unless you step on one. To avoid this, when in and around the sandy areas of a grassbed, move your feet in what we call the “stingray shuffle”. This is sliding your feet across the surface of the sand instead of stepping. The pressure generated from this movement can be detected by the ray several feet away and they will immediately move away.
Despite the fear, they are amazing creatures and play an important role in the overall health of the grassbed community.
1 Snelson, F.F., Williams-Hooper, S.E., Schmid, T.H. 1988. Reproduction and Ecology of the Atlantic Stingray, Dasyatis sabina, in Florida Coastal Lagoons. Copeia. Vol. 1988, No. 3 (Aug 1988). Pp. 729-739.
2 Hoese, H.D., Moore, R.H. 1977. Fishes of the Gulf of Mexico; Texas, Louisiana, and Adjacent Waters. Texas A&M University Presse. College Station TX. Pp. 327.
Sea urchins are one of the more commonly encountered creatures when snorkeling in our seagrass beds. At times these little pin cushions can be found in great numbers. In some locations there have been too many and community events have been developed to remove some. In the western panhandle they have all but disappeared. But for many parts of the panhandle, they are a noticeable member of the seagrass community.
Sea urchins belong to the phylum Echinodermata. The term echinoderm means “spiny skin” and is a good name for this creature. This group also includes the sand dollars, sea cucumbers, and the most famous member, the sea stars. Echinoderms are considered advanced and primitive at the same time. Advanced in the sense of organ development, sensory perception, and food gathering. Primitive in the sense that they have radial symmetry, like many of the more primitive invertebrate groups; bilateral symmetry is considered more advanced. The entire phylum is marine, they have no freshwater, nor terrestrial members, and they do like the water salty – at least 20 parts per thousand, and some need it higher than that.
As mentioned, the sea stars are the “star” of the group. They usually have five arms that radiate from a central disk region. On top there are usually small knobs or bumps which are the remnants of their “spiny skin”. Some species, though none in our area, have elongated spines. Beneath the arms is a radial canal which houses a series of gelatinous suckers called tube feet. The sea star can fill these with water using a unique system called the water vascular system. The tips of the tube feet or concave and, when full of water, can create a suction cup that is used for pulling themselves along the bottom and for grabbing food. These canals all meet within the central disk in what is called a ring canal and the water that fills them is sucked in by the sea star through a screen-like structure on the top of the central disk called a madreporite (“screen sieve”). The central disk is where the mouth is located, and it is located on the bottom. Food is worked into the mouth, digested, and excreted through an anus on the top of the central disk. Most species have some form of eye at the end of each arm and have a good sense of smell and taste.
Sea stars are predators, collecting small organisms they are fast enough to catch (which is not many really). But they can also take on larger slow prey, like shellfish. When they approach an oyster, which is sessile and cannot run away, they will grab each of the valves (shells) of the oyster with one of their arms. They will draw water into their water vascular system creating suction on the tube feet and “stick” onto the shells. They will then force the oyster open. Once open they will invert their digestive tract out of their body in a process called evisceration, consume the oyster, then retract the digestive tract leaving two empty shells on the seagrass bed floor. These empty shells are often found by snorkelers – though there are other predators of bivalves.
Sea urchins differ from their sea star cousins in the way their body is laid out. Imagine you had a five-armed sea star laying on the ocean floor. Imagine taking each of the five arms and rolling them upwards so that the tips of each touch above the central disk. Can you imagine this looking like a ball? A sphere? Now cover the now exposed underside of the arms with long spines (quills) and the tube feet extend between the quills. You have a sea urchin.
Another difference would be the mouth. At the terminus of each arm near the mouth is a single tooth. With five arms, there would be five teeth. Scientists call this set of five teeth Aristotle’s lantern and the urchin uses this to scrap algae from rocks, shells, and grass blades. They are herbivores, moving along feeding on a variety of seaweed and seagrasses in the system.
There is concern with many snorkelers that the quills (spines) of the sea urchin are venomous. That is the case with some species around the world, but not in our area. That said, they are sharp, and the purple urchin (more common in our rock jetties and artificial reefs) hurts. Their quills are sharp and often break off in the skin causing discomfort, much like a splinter. You do not want to handle them, but if you do – handle them with care.
Sand dollars are close cousins of the sea urchin and are in the same class (Echinoidea). If you can imagine taking a round sea urchin and squashing it flat like a pancake, you have a sand dollar. There are also echinoderms in this group that are not as round as sea urchins, but not as flat as sand dollars and are called heart urchins, or sea biscuits. These can be found in grassbeds at the eastern end of the panhandle, but are more common in south Florida.
The sea cucumber is an echinoderm more often found in rocky or coral reef communities, but there are some found in the seagrass beds. To see the relationship between them and their cousins, imagine taking a round sea urchin, lie it on its side, and extended the body so that it is no longer a round ball but an elongated worm-looking creature… sea cucumber. These are primarily scavengers and deposit feeders within the community.
Being a resident of the western panhandle, we have noticed a mass decline of echinoderms in our grassbeds. As a kid in the 60s and 70s we never saw large numbers, as they do in the eastern panhandle, but we did see them. Now they are gone. One suggestion as to why has been salinity. Our bay system over here has more river discharge than those further east and the lower salinity may not support larger populations. The increased development of the years, and the methods of dealing with stormwater, may have created a system that echinoderms do not like. Whatever the reason, finding sea stars and sea urchins in our grassbeds is rare.
The eastern panhandle still has them. And, at times, too many. In recent years there has been an increase in sea urchin populations in St. Joe Bay that has led to overgrazing of the turtle grass. This could lead to a decline in suitable habitat for bay scallops, which the community depends on economically. The state currently sponsors a “Sea Urchin Round Up” event using humans to help control the overabundance of sea urchins.
Echinoderms are a visible, and interesting, part of our seagrass community.
In terms of diversity and abundance, the Phylum Arthropoda is the most successful in the Animal Kingdom. Between them all, there are over one million species. They can be found in all habitats, from the deepest part of the ocean to the highest places in the mountains, from the polar region to the most extreme deserts. Most are insects, but there are also arachnids, centipedes, millipedes, and the ones most common to the marine environment – the crustaceans. With the numerous species within this group, and new ones being discovered all the time, the classification of arthropods is constantly changing. Currently Crustacea is considered a subphylum and there are about 30,000 species within.
There are several keys to the success of arthropods. Number one, their shell. It was seen with the mollusk that having a hardshell to protect your soft body was a winner. However, mollusk make their shells from heavy calcium carbonate. Though this provides excellent protection against most predators, it did slow them down considerably making it much easier for predators to catch them. It is understood that in the world of defense, speed is important. The arthropods make their shells from a strong, but much lighter material called chitin. This material is strong but serves as the creatures’ exoskeleton and must be shed periodically as the animal grows.
Number two, their legs. The name “arthropod” means jointed foot and one glance at the legs of any of these, you will see why scientists call them this. To increase speed animals, need to break contact with the surface of the ground. Birds are the best, lifting off and flying – the fastest form of location there is. The slug-like mollusks have their entire bodies in contact with the sediment, as the “slug” along the bottom of the sea. Many creatures have developed legs and walk, this is the case of the arthropods. Some hop great distances, like the flea. Others can actually swim, like blue crabs. And many of the insects have wings and can fly. But these jointed legs, along with a lighter shell, have been very effective defense for these creatures.
Number three, their sense organs and brain. Though not as intelligent as octopus and squid, arthropods are very aware of their environment and very quick to respond to trouble or a food source. Drop a piece of cheese during a picnic and see just how fast the ants find it. Heck don’t drop the piece of cheese and see how quickly they find it! These animals have a series of hairs, bristles, and setae connected to their shell that can detect movement and pressure changes in the environment. There are canals, slits, pits, or other openings in the shell that can detect odors. And then they have their compound eyes. Compound in the sense there are more than one lens. Each lens does provide an image of the target (in other words, they do not see 100 images of you) but rather each provides a level of light intensity sort of like individual pixels in a computer image, or the image we see when the camera displays “squares” of light so that you cannot read someone’s license plate, or the logo on their t-shirt – we see this on TV news and shows often. Compound eyes do not produce as clear an image as our eyes, but they are MUCH better at detecting motion, and there is an advantage to this. Try stomping on a cockroach, or swatting a fly, and you will see what I mean.
And number four, a high reproductive rate. You see this in many of the “prey” type species. Most arthropods are dioecious (males and females) and can produce millions of offspring at rates that you could never consume them all. So, they survive and can quickly support gene flow and adaptation. These are well designed animals.
In the crustacean world we find several groups. They differ from their arthropod cousins in that they have 10 jointed legs, and two sets of antenna (one set long, the other short). They include at least 30,000 species including the shrimplike cephalocarids, the shrimplike branchipods, the shrimplike ostracods (common in the deep sea), the roachlike copepod (part of the plankton we spoke about in another article in this series), the mystacocards, branchiurans, the familiar barnacles, krill, the roachlike isopods, flea like amphipods, and the most familiar of the group – the decapods – which includes the crabs, shrimps, and lobsters. It is this last group we will focus on.
There are three basic body parts to an arthropod. The head, thorax, and abdomen. In crustaceans the head and thorax are fused into one segment called the cephalothorax (the head of a shrimp or crawfish). The abdomen is what most call the shrimp and crawfish tail (the part we usually eat).
Crabs are the ones we most often encounter when exploring the seagrass beds. Not that the others are not abundant, they are, they are just not seen. They differ in that their abdomen is curled beneath their cephalothorax. The most commonly encountered is the famous blue crab (Callinectes sapidus). Most crabs have modified two of their 10 legs into chelipeds (claws) and most folks seeking crabs for dinner are aware of these claws. The blue crab belongs to a group called the protunid crabs which have modified two additional legs into swimming paddles – they can swim. They are often found crawling around the edges, and within, the seagrass searching for food. When detected over sand, they quickly bury themselves and sometimes people step on them not knowing they are there. When spooked they often will emerge with chelipeds extended and when the time is right, will scurry off running sideways with one cheliped pointed at you. They can get quite large and are a popular fishing target for both recreational and commercial fishermen. The males (the ones with the long then telson on their curled tailed) are more common in the upper estuaries. The females (the ones with the more round telson) frequent the lower bay. During breeding season, the males will move to the lower estuary to find a female. Once found he will crawl on her back and “ride” for a couple of days in what commercial fishermen call “doublers”. At some point the male will provide a tube filled with sperm called a spermatophore to the female. He then moves on. The female will store the spermatophore until she feels it is time to fertilize the eggs, then does so. The eggs begin to develop beneath her abdomen in a spongy looking mass. Early in development the mass is an orange color. Closure to hatching it is brown. Females carrying this spongy mass are called gravid and are illegal to harvest in Florida. The larva will be released in the millions as tiny plankton and go through several life stages before becoming young crabs and starting the whole story again. These popular crabs live for about five years.
Another crab found in the grassbeds is the spider crab (Libinia dubia). This crab does resemble a spider, is slow moving, and very hard to see. It has small chelipeds and feeds on debris and organic material collected by the grasses. They too can get quite large and resemble the king crabs harvested in Alaska.
Stone crabs (Menippe mercenaria) are more often associated with rocky bottoms, or artificial reefs, but they have been found in burrows and crevices within grassbeds. The have wide-stocky chelipeds, which is a favorite with some seafood lovers. Those in the grassbeds do not get as large as those found around the reefs of south Florida, where they support a large commercial and recreational fishery.
The hermit crab is a common resident of grassbeds. The most frequently encountered is the striped hermit (Clibanarius vittatus). Like all hermit crabs, they lack an external shell covering their abdomen and must cover their tail with an empty mollusk shell. Their curled abdomen can grab and wrap around the columella within the mollusk shell and carry around their new home. These hermits have been found in a variety of mollusk shells and are found roaming the beaches at low tide feeding on organic debris and cleaning the grassbeds.
One crab that is often associated with seagrasses is not actually a crab at all. The horseshoe crab (Limulus polyphemus) lacks antenna and is more closely related to the arachnids. This ancient mariner has been plowing the bottoms of estuaries for over 400 million years. They resemble stingrays with their elongated telson and feed on a variety of small invertebrates both in the grassbeds, and in other estuarine habitats. They are quite common in the eastern panhandle and seem to be making a recovery in the western end.
Though rarely seen, shrimp are very prolific in our seagrass beds. Pulling a seine or dip net through the grass will expose their presence, usually in high numbers. The most commonly collected species are those known as grass shrimp (Palaemonetes sp.). There are a few species, and all are small and mostly translucent, though one is a brilliant green. Feeding on organic debris within the grassbed these little guys are an important food source for the larger members of the community.
The more famous of the shrimp group are the brown and white shrimp. These are the species we find on our dinner plates and are one of the most popular commercial species in the country. Brown shrimp (Farfantepenaeus aztectus) are also known as bay shrimp and “brownie”. They are a darker brown than the white shrimp and their uropod (the fan on the tail of the shrimp) is lined in a red color. They do not get as large as the whites and are very popular for fried and steamed dishes. The white shrimp (Litopenaeus setiferus) is a larger shrimp, is lighter in color (“white”), and their uropod is lined with a neon green color. Both of these commercially important species spend their juvenile and young adult days in the grassbeds of our estuaries. Later in the fall the adults move into the nearshore waters of the Gulf where they spawn and die. The planktonic larva drift back into the estuary with the incoming tide, finding the grassbeds and the cycle begins again.
The large diversity of crustaceans within the grassbeds speaks to the importance of this habitat to all marine life. Many are commercially important to the local economy and depend on a healthy ecosystem to survive. All the more reason to protect our grassbeds.
Most of us in the Florida panhandle realize how important seagrasses are to the ecology of our estuaries. Not only do they provide habitat for commercially important finfish and shellfish, but they also help trap sediments, remove nitrogen from the system, and slow coastal erosion. But seagrasses throughout Florida have suffered over the last 50-60 years from environmental stressors created by humans. There has been a large effort by local municipalities to reduce these stressors, and surveys indicate that these have been successful in many locations, but there is more to do – and there are things you can do to help.
Reduce Stormwater Run-off
Stormwater run-off may be the number one problem our seagrass beds are facing. With the increased development along the panhandle, there is a need to move stormwater off properties and roads to reduce flooding of such. Older communities may still have historic drain systems where rainwater is directed into gutters, which lead to drainpipes that discharge directly into the estuary. This rainwater is freshwater and can lower the salinity in seagrass beds near the discharge to levels the seagrasses cannot tolerate, thus killing them. This stormwater also includes sediments from the neighborhood and businesses that can bury grass near the discharge site and cloud the water over much of the system to levels where needed sunlight cannot reach the grasses. Again, killing the grass.
Most would say that this is an issue for the county or city to address. They should be redesigning their stormwater drainage to reduce this problem. And many municipalities have, but there are things the private homeowner or business can do as well.
One thing is to modify your property so that the majority of the rainwater falling on it remains there and does not run off. Much of the rainwater falling on your property falls on impervious surfaces and “stands” creating flooding issues. You can choose to use pervious surfaces instead. For larger businesses, you might consider a green roof. These are roofs that literally grow plants and the rainwater will irrigate these systems with less running into the street. There is a green roof at the Escambia County Central Office Complex building in Pensacola. To learn more about this project, or visit it, contact Carrie Stevenson at the Escambia County Extension Office.
For those buildings that cannot support a green roof, you can install gutters and a rain barrel system. This moves rainwater into a barrel (or series of barrels) which can then lead to an irrigation system for your lawn or garden. All of which reduces the amount entering the streets.
Finally, you can use pervious materials for your sidewalks, driveways, and patios. There are a number of different products that provide strength for your use but allow much of the rainwater to percolate into the groundwater, thus recharging the groundwater (our source of drinking water) and reducing what reaches the street.
Plant Living Shorelines
Coastal erosion is an issue for many who live along our waterfronts. The historic method of dealing with it is to build a seawall, or some other hardened structure. These structures enhance the wave energy near the shoreline by refracting waves back towards open water where they meet incoming waves increasing the net energy of the system. Something seagrasses do not like. There are many studies showing that when seawalls are built, the nearby seagrass begins to retreat. This increased energy also begins to undermine the wall, which eventually begins to lean seaward and collapse. Placement and maintenance of these hardened structures can be expensive.
Another option is a softer structure – plants. The shorelines of many of our estuaries once held large areas of salt marsh which provide habitat for fish and wildlife, reduce erosion, and actually remove sediments (and now pollutants) from upland run-off. But when humans moved to the shorelines, these were replaced by turf lawns and, eventually, seawalls. Returning these to living shorelines can help reduce erosion and the negative impacts of seawalls on seagrasses. Actually, several living shoreline projects enhanced seagrasses in the areas near the projects. Not all shorelines along our estuaries historically supported salt marshes, and your location may not either. It is recommended that you have your shoreline assessed by a consultant, or a county extension agent, to determine whether a living shoreline will work for you. But if it works, we encourage you to consider planting one. In some cases, they can be planted in front of existing seawalls as well.
Avoid Prop Scarring While Boating
Seagrasses are true grasses and posses the same things our lawn grasses have – roots, stems, leaves, and even small flowers – but they exist underwater. Like many forms of lawn grass, the roots and stems are below ground forming what we call “runners” extending horizontally across the landscape. If a boat propeller cuts through them form a trench it causes a real problem. The stems and roots only grow horizontally and, if there is a trench, they cannot grow across – not until the trench fills in with sediment, which could be a decade in some cases. Thus “prop scars” can be detrimental to seagrass meadows creating fragmentation and reducing the area in which the grasses exist. Aerial photos show that the prop scarring issue is a real problem in many parts of Florida, including the panhandle.
When heading towards shore and shallow water, raise your motor. If you need to reach the beach you can drift, pole, or paddle to do so. This not only protects the grass, it protects your propeller – and new ones can be quite expensive.
If Florida residents (and boating visitors) adopt some of these management practices, we can help protect the seagrasses we have and maybe, increase the area of coverage naturally. All will be good.
If you have any questions concerning local seagrasses, contact your local Extension Office.