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.
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.
It sounds like one of those Sci-Fi thrillers where there is a giant asteroid heading to Earth and we need a special team led by Bruce Willis to save the planet. But in this case it is not a large rock, but a large mass of seaweed. And the threat is not a huge impact that would form tidal waves and atmospheric black out but large masses of seaweed covering the beaches up to a foot or more. Once on the beach, the mass of seaweed would begin to break down releasing odors and attracting insects that would not be popular with tourists – just as we get into the peak of tourist season around the state.
Mats of Sargassum on a south Florida Beach.
Photo: University of Florida
It is not something new, this has been a problem in south Florida for a few years now, but this year scientists can see the massive blob of seaweed heading this way and it is larger than before. They are expecting some beaches in Florida to be heavily impacted.
The seaweed in this floating mass is a brown algae known as Sargassum (Gulfweed). Like many brown algae’s, it is yellowish-brown in color and possesses small air bladders called pneumatocysts. These pneumatocysts allow large brown algae, like kelp, to stand tall like a tree in the water column – or, like Sargassum, to float on the surface where they can reach the much-needed sunlight.
Sargassum has small air bladders called pneumatocysts to help them remain afloat on the surface.
Photo: Florida Sea Grant
There are two species of Sargassum that are found in the South Atlantic: Sargassum natans and S. fluitans. They are not easily distinguished so most just say “sargassum”. These seaweeds form large floating mats that drift in the ocean currents. The clockwise rotation of the North Atlantic gyre creates a central point around which the currents spin that is calm – similar to the eye of a hurricane. Here, the sargassum collects in large masses and was noted in the logs of Christopher Columbus as the “Sargasso Sea” – a place to avoid for colonial sailors due to the fact there is little wind or current here.
The Sargasso Sea
Image: University of Florida
Mats of this algae creates an ecosystem drifting across the sea housing transient and residential species that have been the study of marine biologists for decades. The seaweed will get caught in currents that bring it close to shore where fishermen seek it out fishing for jacks or mahi-mahi. Baby sea turtles will use it as refuge until they are large enough to return to the shores of the continents and islands. It will at times get caught in currents that bring it ashore where beach combers sift through to see what they can find. As we mentioned, once on dry ground the seaweed begins to die releasing the odors of decaying sea life and attracting an assortment of insects. When this happens coastal communities will use tractors to drag and remove the smelly mats and deposit them in the local landfill.
In recent years, in south Florida, the amount of this seaweed has increased. The seaweed has formed large mounds on the beaches making beach combing an ordeal and the smell unbearable in many communities. Some of the Sargassum finds its way into the canals of the Florida Keys where it sits and decays, decreasing dissolved oxygen and causing a decline in abundance of some local marine communities. They have responded by removing the Sargassum to the local landfill but are experimenting with composting the material for fertilizing other plants.
Several researchers have experimented with the composting idea with some encouraging results. Some have found a use for it as mulch for coastal mangrove shoots that have lost much of their natural fertilizers due to coastal urbanization. There are problems with using this in some plant settings. 1) It could be too salty for some landscape plants. 2) There is the concern of the amount of arsenic present. Studies continue.
The recent large masses of Sargassum coming ashore began in 2011. What is causing this recent increase in Sargassum on the beaches? Researchers are finding the source of this material is not mats rotating off of the Sargasso Sea but forming in the belt of moving water between the North Equatorial Current in the south Atlantic and the equator itself. The exact cause of this increase growth is uncertain but could be linked to an increase of nutrients from regional rivers, like the Amazon, and from increased ocean temperatures due to climate change – both of these are exactly what seaweeds like.
This year the mass of seaweed seen from satellites is particularly large – over 5,000 miles. It is drifting in the currents heading for the Caribbean and Florida. It will most likely impact south Florida, but researchers do not believe the impact will be as large along Florida panhandle beaches. They will continue to monitor and report on the movement of this mass of seaweed over the course of the summer.
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.
It seems odd that we would be talking about maintaining your sewer system; that was a selling point to convert from septic. But there are things we do that can cause clogs in the lines that initiate what we call Sanitary Sewage Overflows (SSOs). These overflows can overflow into your home and into the street, entering the stormwater systems leading to our coastal waterways.
How you can prevent this is pretty simple – watch what you pour down your drain. After visiting one sewage treatment facility in Georgia, we were told by the plant manager “If you tell the public one thing… tell them to quit pouring bacon grease down the drain”. He then held up a pipe from their system that was 80% clogged with bacon grease. All fats, oils, and grease poured down the drain eventually solidify and form clogs. Recently they have found that milk solidifies as well. You should avoid pouring all of these products down the drain.
So, what do we do with it them?
In Escambia County, the local utility provides a free service to deal with this they call the FOG Program (FOG – Fats, Oils, Grease). They provide large metal cabinets outside locations around the community. Inside, there are 1-gallon plastic containers. You take one home. Fill with your fat, oil, and grease. Return it and get a new one. They take these oils back and covert them into biofuels. It is very similar to the propane system for your BBQ grill – and often found at the same place – but the difference is that there is no charge. If you live in Escambia County, you can find the FOG dispensary cabinet closest to you at ECUA FOG. If your county does not offer this service, encourage them to do so.
The FOG gallon containers are found in these metal cabinets placed around the county.
Photo: Rick O’Connor
Another issue that has caused SSOs is the flushing of “flushable wipes” and similar products. They are “flushable” but not “degradable”. There was one report from London of a ball of flushable wipes equivalent in size to one of their buses found in the city sewer system. I have seen signs in public restrooms that say “flush nothing but toilet paper” – and that is good advice.
1-gallon container provided free to dispose of your oil and grease.
Photo: Rick O’Connor
And there is one other thing that you, the property owner, can do to help reduce the chance of leaking sewage into our waterways – maintaining your laterals.
Laterals are the pipes extending from you house to the sewer system under the street. Maintaining these are the responsibility of the homeowner, and most do not – or may not know it is their responsibility. Newer developments should have laterals in good shape, older ones should be inspected. I live on an older community in Pensacola. Many of the houses in our neighborhood were built in the 1930s, some in the 1920s. The laterals were made of terracotta, or something similar. They have cracked and filled with roots and dirt over time. There is certainly leakage ongoing, and the homeowner may not even know it.
This past summer we had a sewage backup. We called a plumber who first recommended scoping the laterals. This involved sending a television camera scope down the line. We found that half way between our house and the street it was relatively new PVC line. From the halfway point to the sewer line in the street, it was old terracotta. The sad part of this was we had paid a contractor to replace the terracotta to the street – they only did half. You would say this fell on the contractor to fix, but that contractor was no longer in business – if fell on us. We paid to have the rest of the lateral converting to PVC, we are now good.
The point of this story is two things… (a) many have never had their lateral surveyed, you should to make sure all is good. This is not only good for the environment, but also will save costly repair bills down the road. (b) Just because you paid to have to have it repaired does not mean it was. I recommend you use a certified, well known plumber to check and, if needed, replace/repair your line.
If the property owner will consider, and act on, one of the following three this can reduce the health advisories issued in our coastal waters significantly. We encourage you to do so and educate your neighbor and friends to do the same.
If on septic, develop and enact a septic tank maintenance plan.
Convert from a septic system to a sewer system.
If on sewer, have your laterals inspected, do not pour fats, oils, grease, or milk down the drain, and do not flush flushable wipes or similar products.
If you have further questions, do not hesitate to contact your county extension office.
