A Sea of Grass; Part 5 – Worms

A Sea of Grass; Part 5 – Worms

When most hear the word worm unpleasant things come to mind.  “Gross”, “dirty”, “decaying”, “disease”, “rotten”, are a few.  And then there is the whole parasite thing.  But then there are those who like them.  Gardeners, kids, and fishermen find earthworms in particular pretty cool.  They are not the typical creature we look for on a hike, or search for on a TV documentary, and they are certain not at the top of creatures you would be looking for while exploring a seagrass bed – but they are there. 

According to the 4th Edition of Robert Barnes’s Invertebrate Zoology (1980) there are at least 11 phyla of worms, and he mentions no fewer than six classes.  It is an extremely diverse group of creatures, and many are the bridge between the simple animals and the more complex.  In this article we will focus on four phyla of the more common worms, or least the ones most commonly known. 

These phyla are divided by body shape and internal complexity.  The simplest are the flatworms (flukes and tapeworms), the more complex are the annelids (earthworms and leeches).  The vast majority of these animals are very small (less than one centimeter) and not seen by the casual snorkeler.  Some of the nemerteans (a phyla of flatworm) and the segmented polychaetes (related to earthworms) are quitter large and are easily seen by us. 

The polychaetes may be the most familiar to us.  These are segmented worms in the phylum Annelida.  They are segmented like their cousins the earthworm but differ in that (a) each segment has a small leg-like structure (parapodia) and (b) they like marine conditions. 

Neredia are one of the more common polychaete worms. Photo: University of California Berkley

They resemble centipedes crawling in and amongst the seagrass blades and are often found within seashells we pick up and explore.  They are basically harmless, and many species are the “garbage feeders” doing an excellent job keeping the system clean.  We often see their “volcano” like burrows in the sandy areas within a seagrass meadows and many species produce glob-like gelatinous egg sacs that seagrass explorers confuse with jellyfish.  There are also those that produce tubes.  Some of these tubes are paper-like with bits of shell and other debris embedded in them.  They produce these using mucous from their bodies to cement them together, place the tube within the sediment in a vertical position, and then live in them.  Other tubeworms will produce their tubes out of shell material (calcium carbonate) forming snake-like structures on the surface of shells and discarded beer cans.  And then there are a few called bristle worms.  These are large and crawl across the surface of the substrate but have thin spines that extend off their bodies like cactus.  Many of these do have venom and can be quite painful. 

Polychaetes are the most advanced of the marine worms in the seagrass beds.  Possessing a brain that is connected to sensory organs that can detect light and chemicals in the water, they can both find prey, and avoid predators.  Prey varies between species.  Most polychaetes can invert their pharynx (rather quickly) to grab prey using tooth like jaws.  The carnivorous ones feed on small invertebrates (including other polychaetes).  Others will use these jaws to scrap algae from shells and grass blades and are scavengers.  Most reproduce sexually where there are both males and females and they possess a complete digestive tract (including a mouth and an anus) – as you will see… not worms do.  In 1980 there were about 5300 species of them worldwide. 

Nemertean worms are another large marine worm, but one few people have seen.  This is because they are more nocturnal by habit.  They are not segmented but rather are flat and gelatinous.  They possess a proboscis that can be “launched” by the worm, that has a stylet (spear) at the tip – like a pole-spear gun.  They use this to hunt invertebrates and find them by using their sense of smell.  They also reproduce sexually, and there are separate males and females, but many will fragment into smaller worms when irritated.  There are two classes and four orders of these worms worldwide. 

Most of the remaining worms are either so tiny you will not find them or are endoparasites living within some vertebrate or invertebrate host within the seagrass community.  The more famous group are the flatworms.  These include the parasitic flukes and tapeworms.  However, there is a class of free-swimming flatworms that crawl (or swim) around the “seagrass forest”. 

The swimming ones are known as tubellarians.  Most are clear or opaque, but in the coral reef community some are very colorful.  Flatworms are the more basic members of the worm group.  They lack a complete digestive system and must both eat and expel waste through the same opening (the mouth).  Some tubellarians feed on small invertebrates which they capture and engulf without using teeth.  Others feed on dead and decaying creatures, again – cleaning the environment.  There are some that live commensally with mollusk and crustaceans.  There is one that is rather large and can be seen on the gills of horseshoe crabs.  They do have a simple brain and sense the world by detecting light, a sense of touch, and smell.  In 1980 they reported about 3000 species worldwide. 

This colorful worm is a marine turbellarian. Photo: University of Alberta

The parasitic flatworms include the famous flukes and tapeworms.  These live within the bodies of their hosts feeding on mucous, cells, tissue, and blood (yep – here is the “gross” “disgusting” thoughts we mentioned at the beginning).  They possess tough skin to protect them from the digestive enzymes of their host.  Most reproduce sexually but are hermaphroditic (each worm being able to produce both sperm and egg).  Most require secondary hosts to complete their life cycle.  For example, they may live in the gut of a spotted seatrout but will need to complete their larval stage in the gut of a mollusk.  So, the eggs are released with the feces of the trout, the larva find a mollusk and enter, develop, and then expelled again via feces to once again find a trout.  It’s a wonder they can do this – but they do. 

The human liver fluke. One of the trematode flatworms that are parasitic. Photo: University of Pennsylvania

The tapeworms cycle differs in that their head is round and has a series of hooks they use to embed into the intestinal tract of their host.  The rest of their body is flat and segmented (each segment called a proglottid).  These proglottids are released into the environment to find another host. 

You may now be afraid of becoming infested with parasitic worms if snorkeling in seagrass beds.  Fear not… these animals are VERY specific about the host they can survive with – and you are not one of them.  Most seagrass explorers do not think of worms when they visit this community, and probably will not see any, but they are there and play an important role in keeping the system healthy. 

A Sea of Grass; Part 4 Jellyfish

A Sea of Grass; Part 4 Jellyfish

The word “jellyfish” tends to initiate a similar response in most people – “scream”, “run”, “this is going to hurt”.  Being stung by a jellyfish is not pleasant and is something most would prefer to avoid.  Our beaches warn us when they are out by flying a purple flag. 

When exploring the seagrasses, this is not the first animal people thing they will encounter.  Few associate jellyfish with the seagrass community.  But within any community there are those we call residents (they reside here) and those we call transients (just passing through).  It is the second group that we can place most jellyfish, at least the ones we are concerned about. 

The sea nettle. Photo: University of California at Berkley.

Jellyfish are animals, but not your typical ones.  They are obviously invertebrates but differ from most others by having radial symmetry (having a distinct top and bottom, but no head nor tail).  They possess ectoderm and endoderm (so, they have a skin layer and some internal organs) but they lack the mesoderm that generates systems such as the skeletal, circulatory, and endocrine.  Though they do not have a brain, they do have a simple nervous system made up of basic neurons and some packets of nerve cells called ganglia.  They seem to know when they are not in the upright position and know when they have stung something – which initiates the feeding behavior.  But they are pretty basic creatures. 

When you view a jellyfish the first thing you see is the “bell” and the tentacles – we always see the tentacles.  The bell is usually round (radial), could be bell-shaped, or could be flat.  It is made of a flexible plastic-like jelly material called mesoglea.  Most of the mesoglea is actually water.  When you place most jellyfish on the dock and come back in a few hours there may be nothing but a “stain” of where it was.  It completely evaporated.  There are some exceptions to this, like the moon jelly and the cannonball jelly, who leave thick masses of mesoglea for long periods of time.   

Image: Wikipedia.

If you look closer at the “bell” you will see shapes within the mesoglea.  Some are stripes, and may have color to them, others look like a clover leaf.  These are the gonads of the animal.  Jellyfish are hermaphroditic (the gonads can produce both sperm and egg), and they reproduce by releasing their gametes into the water column when triggered by some environmental clue to do so. 

Around the edge of the “bell” many have a thin piece of tissue called the velum that can undulate back and forth and allow the jellyfish to swim.  Swimming can involve moving up or down in the water column, or turning around, but the swimming action is not very strong and the tide and current actually plays a larger role in where the animals go – like pushing them through a seagrass bed. 

Under the “bell” is a single opening, the mouth, that leads into a simple gut (the gastrovascular cavity).  This serves as the stomach of the creature.  But there is no anus, when the jellyfish has digested its food, the waste is expelled through the same opening – the mouth.  This is called an incomplete digestive system

Jellyfish are predators and hunt small creatures such as baitfish.  Though they know whether they are upside down or not, and may be able to detect light, most have no true eyes and cannot see their prey.  Some species may be able to detect scent in the water and undulate their velum to try and move towards potential food, but most drift in the water and hope the tide carries them to dinner.  To kill their prey, they extend tentacles into the water.  These tentacles are armed with stinging cells known as nematocysts.  Each nematocyst holds a coiled harpoon with a drop of venom at the tip.  They are encased in a cell membrane and are triggered when an object, hopefully food, bumps an external trigger hair that will fire the harpoon.  This will then trigger the release of many nematocysts and the potential prey will be “stung” by many drops of venom.  The venom can either kill or paralyze the prey at which time the tentacles bring it to the mouth.  Many jellyfish have venom that is painful to humans, like the sea nettle and moon jelly, others have a mild venom that we do not even notice.  Some have a very strong venom and can be quite painful, like the Portuguese man-of-war which has put some in the hospital.  The famous box jelly of Australia has actually killed humans.  We do have box jellies in the Gulf of Mexico, but they are not the same species. 

This box jellyfish was found near NAS Pensacola in November of 2015. Photo: Brad Peterman

As the tide pushes these transients through the seagrass meadows, their tentacles are extended and small baitfish like juvenile pinfish, croakers, and snapper become prey.  But there are resident jellyfish as well. 

With the Phylum Cnidaria (the stinging jellyfish) there are three classes.  Class Scyphozoa includes the bell-like jellyfish that drift in the water column with extended tentacles – what are referred to as medusa jellyfish.  But there are two other classes that include benthic (bottom dwelling) jellyfish called polyps

Polyp jellyfish resemble flowers.  The “bell” part is a stalk that is stuck to a rock, pier, or seagrass blade.  Their tentacles extend upwards into the water column giving the creature the look of a flower.  Instead of drifting and dragging their tentacles, they hope to attract prey by looking like a hiding place or other habitat.  The sea anemone is a famous one, and a good example of the polyp form.  But it also includes corals and small polyps known as Hydra.  Hydra are tiny polyps that are usually colorless and can easily attach to a blade of turtle grass.  Here they extend their tentacles into the water column trying to paralyze small invertebrates that are swimming by or grazing on the epiphytes found on the grass blades. 

The polyp known as Hydra. Photo: Harvard University.

Another jellyfish that drifts in the current is Beroe, what some call the “football jellyfish” or “sea walnut”.  This a relatively small blob of jelly that lacks tentacles but rather has eight rows of cilia/hair (ctenes) along its side that move quickly and move this animal through the water.  But like their medusa cousins, not against the tide or current.  These jellyfish do not sting, they lack nematocysts, and hence are in a different phylum known as Ctenophora.  Kids often find and play with them when they are present, and they are luminescent at night.  These stingless jellyfish feed on small plankton and each other and are another transient in the seagrass community. 

The non stinging comb jelly. Florida Sea Grant

There are certainly species of jellyfish to be aware of and avoid.  But as you look deeper into this group there are harmless and fascinating members as well.  Most of these Hydra are very small and hard to see while snorkeling, but they are there.  Another creature to try and find while you are exploring and play “seagrass species bingo”.  Have fun and stay safe. 

A Sea of Grass; Part 3 – The Sponges

A Sea of Grass; Part 3 – The Sponges

Many who visit a seagrass bed for fishing or snorkeling, see many forms of marine life while there.  There are numerous small silver fish darting in and out of the grass, an occasional stingray half buried in the sand waiting to ambush prey, and sometimes a horseshoe crab crawling along looking for a meal.  One seagrass community creature they are not aware of, even if they are in front of them, are the sponges. 

Those who are not familiar with the creature we call the sponge may think of the synthetic ones purchased at grocery stores and made in a factory somewhere.  They are usually colored to match your kitchen or bathroom.  Those who are familiar with them associate them more with reefs.  Some reef sponges can become quite large and often they are quite numerous out there.  But they do not register as a member of the seagrass community with most people.  But they are out there. 

A vase sponge. Florida Sea Grant

From a taxonomic point of view sponges are interesting.  What is a sponge?

Is plant? animal? fungi?

Well, to classify it using the characteristics of each, we can rule out plants.  Plants have cell walls and organelles within some cells to conduct photosynthesis.  This is not the case for sponges. 

We can also rule out fungi.  Though fungi do not photosynthesize, they do have cell walls, and sponges do not. 

This leaves animals.  Yep… they are animals. 

Once you classify it as an animal the next step is to declare it either a vertebrate or invertebrate.  Based on the definition of each, this would be an invertebrate – there is no backbone. 

Invertebrates can be further broken down based on their symmetry and which germ layers they possess in the early stages of development – the larval stages. 

Most invertebrates are categorized as either having radial or bilateral symmetry.  Radial invertebrates have a top and bottom (dorsal and ventral) side, but no head or tail (anterior, posterior).  Bilateral invertebrates will have all four.  For some sponges, you can find radial symmetry, for others there is no symmetry at all – those would be asymmetrical. 

Bilateral creatures have a distinct “head” end (anterior) and a “tail” end (posterior).

With germ layers you can have ectoderm (the outside cell layer), endoderm (the inside), and mesoderm (the middle layer).  Each germ layer develops different structures as the larva grows.  If the creature is does not have a specific germ layer, they will not develop those specific structures.  Sponges have no germ layers.  They do not have true skin, no internal organs, no circulatory, musculature, or nervous system.  That is a sponge… the simplest form of animal life on the planet. 

The three germ layers of animal development.

When you look at a sponge you do see structure.  There are different forms (species) of them and they can be distinguished from each other and named – like “vase sponge”, or “barrel sponge”.  But when you look inside of them many have a lot of tissue with canals and channels running all through them.  Like what an ant colony would look like underground. 

A closer look shows that the exterior wall is very porous (giving them their phylum name Porifera).  The water enters these pores and moves all through the massive highways of channels running through the creature.  Eventually the water exits the sponge at the top through large pores (or one large pore) called the osculum.  The currents that drive this water movement are generated by the flagella of small cells called choanocytes (collar cells).  They line the channels by the thousands.  Rotating their flagella, they create water movement the way a rotating fan causes air movement.  The movement is from the environment into the sponge.  Here they collect food from the water (small microscopic creatures and other forms of organic debris), and oxygen. 

The anatomy of a sponge. Flickr

There are other cells within the lining of the channels called amoebocytes who assist with reproduction.  They can encase genetic material (cells) within a hard matrix called a gemmule and “toss it” into the currents where it will exit through the osculum, drift in the ocean currents, and form a new sponge elsewhere.  Being simple creatures, they can certainly reproduce asexual by simple cell division.  Fragments of sponge will also generate new sponges. 

The skeleton that holds these cells into the form we see is a series of hard structures called spicules.  Spicules come in different shapes and under the microscope appear to look like thorns, are the “jacks” of a common game played by baby-boomers when they were kids.  Some are solid, others a little more flexible, and the material used to make these spicules are used to divide sponges into different classes. 

Sponge spicules. Image: NOAA

Spicules made from calcium carbonate are hard and scratchy, they are in the Class Calcarea.  These are often sold as “luffa’s”.  Those made of the more flexible-spongin are in the Class Demospongia and is the largest class of sponges.  These are often sold as “bath sponges” and are softer.  And then there is the Class Hexactinellida – the “glass sponges”.  Their spicules are made of clear silica and they look like they are made of glass.  They are more common in the deeper part of the ocean and are beautiful. 

Glass sponges are beautiful. Photo: NOAA

In the seagrass beds of the panhandle, you will find sponges from the “bath sponge” group.  One common one sold at the Gulf Specimens Lab in Panacea is called “Green Finger Sponge”.  As you move through the grasses you will encounter these anchored near the base of the grass.  They are usually dark in color, often a dark green almost black, and when opened appear yellow or orange on the inside. 

They are full of creatures.  Sponge channels provide excellent hiding places for the small creatures who graze on the epiphytes found on the grass blades.  All sorts of small crustaceans and worms can be found here.  It is like a microhabitat within the grassbed system itself. 

Green finger sponge common in panhandle grassbeds. Photo: Gulf Specimens Lab

The relationship between sponge and grass is complicated.  Sponges filter the water, improving water clarity which seagrasses need.  However, seagrasses are excellent at trapping and holding sediment, which also improves water clarity but these same sediments can plug the pores of sponges which they need to feed.  It is sort of a love/hate relationship between them. 

The purpose of this series is to educate you on some of the members of the seagrass community.  Sponges are one such creature and most people do not notice them.  But they are interesting creatures if you take a look. 

Sea of Grass; Part 2 – The Epibiota

Sea of Grass; Part 2 – The Epibiota

The open grasslands of the American west support huge herds of grazing herbivores such as bison, antelope, and deer.  These large herds again support populations of hunters such as wolves, coyotes, and – historically – bears.  The huge acres of wetland grasses we call marshes are productive as well, with all sorts of grazing creatures that feed on the grass like snails and insects, which in turn support populations of first order carnivores like birds, crabs, and turtles, who then feed larger predators like alligators, otters, and raccoons. 

The salt marsh is full of life, if you look close enough. Photo: Rick O’Connor

One would think that the submerged seagrass meadows would work in the same way.  But there are no large herds of bison like creatures that graze on the grasses.  True, manatees and sea turtles do graze on these, but not in the numbers we see with bison and antelope.  There are numerous species of snails and crustaceans that live in seagrass, but it is not the grass they are interested in… it is the epibiota.  These epibiota are the key to vast diversity of creatures living in seagrasses.  If you snorkel or seine through a submerged grassbed you will notice the majority of creatures are small.  This place is a nursery for the estuarine and marine environments.  These grasses provide excellent hiding places and the epibiota provide the food they need to grow. 

Grassbeds are also full of life, albeit small creatures. Photo: Virginia Sea Grant

So, what are these epibiota?

The term epibiota means “creatures that live on other creatures”.  They can be further broken down into epiphytes (plants that growth on other creatures), and epizoids (animals that grow on other creatures).  Spanish moss is a familiar example of an epiphyte most people know.  Barnacles growing on a turtle shell, or a whale could be an epizoid you are familiar with.  Many epibiota are small, even microscopic.  You can see the algae growing on the shells of turtles, or the fur of the sloth.  There are also numerous epizoids that are microscopic, and no one sees.  It is a whole field of microbiology – the study of the natural history and diversity of this tiny world that, certainly in the case of seagrasses, makes the whole thing work. 

The wide blades of turtle grass provide habitat for a variety of epibiota. Photo: UF IFAS

With the seagrasses you will not always see the epibiota we are talking about.  At times, there are mats of algae growing on the grass like Spanish moss on oak trees.  We typically see these epibiotic macroalgae growing on seagrasses in the spring and summer.  Most of these algal mats are red algae.  Studies have shown that they support juvenile animals as hiding habitat and can increase the overall biomass of seagrass meadows.  But, like with all things, too much of a good thing can have a negative effect on seagrass meadows as well.  The seaweed can smother the grasses, reducing needed sunlight, and enhance the decline of seagrasses in some areas. 

Gracilaria is a common epiphytic red algae growing in our seagrass beds. Photo: Rick O’Connor

Most of the epibiota feeding the growing populations of shellfish and finfish using these nurseries are microscopic plants and animals that appear to us as “scum” on the blades of the grass.  As you might expect, the wider the blade (in this case turtle grass) can support a higher diversity and abundance of growing grazers than the thinner shoal grass. 

A study conducted in 1964 listed 113 species of microscopic algae existing on the blades of seagrasses in Florida.  They include such creatures as diatoms, cynobacteria, and bryozoans.  We will focus on these.

Diatoms are quite abundant on seagrass blades and provide for microscopic grazers. Photo: University of New Hampshire

Diatoms are single celled plant-like algae that are encased in a clear silica shell.  They are one of the most abundant forms of oxygen producing plant-like creatures found in the sea.  Many species drift with the phytoplankton layers of the open ocean.  Others are benthic, living on the bottom upon rocks, seawalls, turtle shells, and seagrasses.  It has been stated that 50% of the oxygen produced on our plant comes from the diatoms and the dinoflagellates (another microscopic plankton). 

Cells of a species of cyanobacteria. Photo: Florida Atlantic University.

Cyanobacteria are what many call blue-green algae.  They produce a darker colored green with their photosynthetic pigments – thus the name blue-green algae – but were not initially identified as a bacteria – which they are now because they lack an organized nucleus.  Many have heard of the recent cyanobacteria blooms in central and south Florida in freshwater systems.  Some species are toxic and have caused fish kills and even made pets, who drank from water with cynaobacteria, very sick.  There hundreds of different species found in marine systems.  Like diatoms, some live in the water column, others are attached to an object on the bottom – like seagrasses. 

This beautiful matrix was built by a group of microscopic animals known as bryozoans.

Bryozoans are microscopic colonial animals.  They act and behave similar to corals, though they are much smaller.  Some species appear as a “cast net” over the shell of a snail or clam, and can be seen on blades of turtle grass as well.  There are many other species of these colonial creatures that call seagrass home. 

We are highlighting these three groups but there are many other forms of epiphytes and epizoids growing on these grass blades.  And it is these that the small grazers, like tiny crustaceans, feed upon, which in turn are what the millions of small silver juvenile finfish and crabs are feeding on.  The seagrass meadow biodiversity and productivity is dependent on them and most Panhandle folks do not know they are there.  Dr. Edward O. Wilson made a comment in his book Half Earth, that we have been focused on conservation of wildlife and habitat for many years now – but we fully do not understand what it is we are trying to conserve.  We focus on blue crab and manatee conservation and do not realize that conservation of these micro-communities is essential for conservation, or restoration, success.  The first step in conserving such communities is knowing they exist and how they support the system.  You now have a little more knowledge of them, but there is SO much more to learn. 

A Sea of Grass; Part 1 – The Grasses

A Sea of Grass; Part 1 – The Grasses

Many in the Florida panhandle are aware of the importance of seagrasses to estuarine ecology.  They have heard this many times before and have heard how important it is to protect them.  Some are aware that they are important as a nursery for many commercial important fin and shellfish.  But fewer are aware of the diversity of life that exists in these “fields of grass”.  Much of the life there is small and unnoticeable until you don a mask and explore.  Even then, you need to slow down and look closely. 

In this series on “Sea of Grass” we will be looking at some of the species that reside in these massive meadows expanding the Florida panhandle.  We begin with the grasses themselves. 

Seagrasses are just that – grasses that grow “under the sea”.  They are similar in many ways to the grasses that grow in your yards.  Their blades extend above the sediment and are usually all one sees as they are exploring the meadows.  Being true plants, they do have stems – but these stems run horizontally beneath the sediments and are called rhizomes.  Rhizomes are like “runners” and extend the plants across the landscape.  Many have discovered rhizomes in their yards when pulling weeds.  You begin to pull and a the runner exposes itself like pulling a thread from a sweater.  From these rhizomes extend the small roots.  Like lawn grass, seagrass use the roots to help anchor them in place and remove water and nutrients from the environment.  But they are immersed in water and, like many marine creatures, have the ability to desalinate it so they have a source of freshwater. 

Like all plants, seagrasses require sunlight for photosynthesis.  Thus, they must grow in shallow water.  In the western panhandle they are limited by the availability of light and are usually found in the estuaries where the water depth is not more than 10 feet.  As you move into the eastern panhandle, particularly close to where the Big Bend begins, there are fewer large rivers depositing muddy water, more expanses of salt marsh to remove sediments from runoff, here seagrasses can grow deeper.  Here they can expand into the open Gulf of Mexico itself producing hundreds of thousands of acres of these grass meadows. 

Seagrass beds have declined over the last half century. Photo: Rick O’Connor

They are not fond of high energy systems.  Large waves can rip seagrasses from the bottom and deposit them onshore.  In the western panhandle the Gulf generates larger waves and thus the grasses are found in the protection of the lagoons, sounds, and bayous.  Near the Big Bend natural wave energy is low enough to support them in the open Gulf.  It has been estimated that Florida has between 2.2 and 2.5 million acres of seagrass.  Most of this is along the west coast of the peninsula running from the Florida Keys to the Big Bend1.

There are seven known species of seagrass in the state.  Three of these are common in the panhandle and an additional one, Manatee grass (Syringodium filiforme), is beginning to expand its range into our area. 

An amazing meadow of turtle grass. Photo: Virginia Sea Grant

Two of our common species prefer more saline water – water with a salinity at least 20 parts per thousand (ppt).  Those are Turtle grass (Thalassia testudinum) and Shoal grass (Halodule wrightii).  These grasses both have flat blades but differ in blade width.  Turtle grass is wider (4-12mm) and resembles St. Augustine grass from our lawns.  Because of the wider blade, they grow in deeper water (not being able to tolerate the break waves and whitecaps near the surface).  Shoal grass is very thin (<4mm) and feels more like human hair when you run your toes and fingers through it.  Manatee grass resembles shoal grass in size but has a round blade instead of a flat one.  In the Pensacola area we are beginning to find patches of it growing in Big Lagoon and Santa Rosa Sound. 

Shoal Grass Photo: Florida Department of Environmental Protection

Widgeon grass (Ruppia martimia) can tolerate the higher salinities of the lower estuary but can also tolerate the lower salinities of the upper estuary.  It dominates the lagoons and bayous of the upper Pensacola Bay system.  It has a thin flat blade like shoal grass but differs in that it branches as it grows instead of a single blade extending about the surface. 

Widgeon Grass

These meadows of seagrass provide food and habitat for a myriad of marine creatures, who we will meet in other posts in this series.  In Part 2 we will begin with one that is very important but very few know is even there – the epiphytes. 


1 Florida Seagrasses. Florida Department of Environmental Protection.  https://floridadep.gov/rcp/seagrass.

North Florida’s Springs

North Florida’s Springs

Morrison Springs in Walton County is a natural spring ideal for paddling, snorkeling, and diving. Photo credit: Carrie Stevenson, UF IFAS Extensio

There is just SO much water in Florida. Besides the tremendous amount of rain and 1,350 miles of coastline and beachfront, there are endless bays, bayous, creeks, rivers, and streams. In this state, it is extraordinarily difficult to live more than a few miles from a body of water. Among the the coolest (literally) types of water bodies in Florida, though, are our springs.  Like brilliant gemstones, the state’s 700+ springs dot the Florida landscape like a strand of sapphires.

While we have springs bubbling up all over northwest Florida in areas where the underground water table meets the surface, larger springs are more common as you move east and south. Some parts of north Florida and most of the peninsula are built on a limestone platform, known by the geological term “karst.” Limestone is composed of calcium carbonate, which has a porous and easily degradable chemical structure. When this barrier is breached, it allows the cold groundwater an opening directly to the surface water—hence a spring. (Fun fact—there are surface water streams that actually disappear into a spring—these are called swallets, operating as the reverse version of a spring!)

The striking blue-green water in Three Sisters Spring is only accessible by kayak or swimming. Photo credit: Carrie Stevenson, UF IFAS Extension

A few of the largest springs in northwest Florida are Vortex, Ponce de Leon, and Morrison Springs, found in Holmes and Walton County. Vortex is a privately operated water park and scuba diving/training facility. It is where the red and white “diver down” flag was invented and has a complex underwater cavern system. Ponce de Leon and Morrison Springs are state and county-run parks with a more natural feel, surrounded by woods and basic infrastructure for access. Morrison will especially wow visitors with its tremendous turquoise coloring.

Crystal clear water in Morrison Springs. Photo credit: Carrie Stevenson, UF IFAS Extension

Before a meeting in Crystal River last week, I paddled and snorkeled through the famous Three Sisters Spring. As part of Crystal River National Wildlife Refuge, it is a popular but highly protected area. Three Sisters is well-known as a manatee gathering place, especially in winter, but during my visit was mostly unoccupied. The color was striking, though. Why do so many of these springs have such brilliant blue and turquoise coloring? The phenomenon is essentially the same as the blue-green Gulf waters in the Panhandle. The reflection of the sky on a sunny day with the backdrop of that pure white sand causes the water to reflect a color that inspired the nickname “The Emerald Coast.” In springs, the white calcium carbonate in limestone breaks down into tiny crystals, mixing with the water and reflecting the vivid shades of blue.

Alexander Springs Creek in Ocala National Forest is overrun with algae. Photo credit: Matt Cohen, UF IFAS

Besides their beauty, clarity, recreational, and wildlife value, springs pump 8 billion gallons of fresh water a day of into Florida ecosystems. Seagrass meadows in many of these springs are lush. Because they are literal windows into the underground aquifer, they are extremely vulnerable to pollution. While many springs have been protected for decades, others were seen as places to dump trash and make it “disappear.” Many have been affected by urban stormwater and agricultural pollution, losing their clarity, reducing dissolved oxygen levels, and prompting massive cleanup and buffer protection zones.

On one of these hot summer days in Florida, take the time to visit our incredible springs. While it may not be the literal “Fountain of Youth,” swimming in a spring is a unique and invigorating experience, and a beautiful way to get off the beaten path. A comprehensive guide to Florida springs, research, and statewide protection initiatives can be found at the Florida Department of Environmental Protection’s springs website.