In Part 1 of The Estuary’s Natural Filtration System article, we discussed the major contributors to natural filtration inside of the estuary. These examples included oysters, marsh plants, and seagrasses. In Part 2, we will discuss the smaller filter-feeding organisms including tunicates, barnacles, clams, and anemones.
Tunicates
Pleated Sea Squirt – Photo Credit: Don Levitan, PH.D. FSU
Tunicates, also known as sea squirts, are very interesting marine invertebrates and can be easily confused for a sponge. There are many different types of tunicates in the estuaries and can be either solitary or colonial. You might’ve seen these at an aquarium attached to different substrates, and when removed from the water, their name sea squirt comes into play. Tunicates have a defense mechanism to shoot out the water inside their body in hopes of being released by any predator.
Tunicates are filter feeders and intake water through their inhalant siphons and expel waste and filtered water through their exhalant siphons. Tunicates can filter out phytoplankton, algae, detritus, and other suspended nutrients. The tunicate produces a mucus that catches these nutrients as it passes through, and the mucus is then conveyed to the intestine where it is digested and absorbed.
An invader to the Gulf of Mexico, the Pleated Sea Squirt (Styela plicata), hitched rides on the hulls of ships and found the Gulf of Mexico waters very favorable. You can sometimes spot these organisms on ropes that have been submerged for a long period of time in salty waters. Even though they are non-native, these sea squirts can filter, on average, 19 gallons of water per day.
Barnacles
Barnacles along the seashore is a common site for many. Photo: NOAA
One organism that seems ubiquitous worldwide is the barnacle (Genus Semibalanus and Genus Lepas). The Genus Semibalanus contains the common encrusting barnacle we are accustomed to seeing in our waterways along pilings, submerged rocks, and even other animals (turtles, whales, crabs, and oysters). The Genus Lepas contains Gooseneck Barnacles and can be seen attached to flotsam, floating organic debris, and other hard surfaces and have a stalk that attaches them to their substrate. Interesting fact, certain gooseneck barnacle species are eaten in different parts of the world.
This image from a textbook shows the internal structure of a barnacle. Notice the shrimplike animal on its back with extendable appendages (cirri) for feeding. Image: Robert Barnes Invertebrate Zoology.
Barnacles have over 2,100 species, are closely related to crabs and lobsters, and are a part of the subphylum Crustacea. At first glance, you might not think a barnacle is closely related to crabs, but when you remove the hard plates surrounding it, the body looks very similar to a crab. Barnacles also have life cycle stages that are similar to crabs; the nauplius and cyprid developmental stages. Inside of the hard plates is an organism with large feather-like appendages called cirri. When covered by water, the barnacles will extend their cirri into the water and trap microscopic particles like detritus, algae, and zooplankton. Barnacles are at the mercy of tides and currents, which makes quantifying their filtering ability difficult.
Hard Clams
Clams of North Florida – UF/IFAS Shellfish
Even though not as abundant in the Florida Panhandle as they were in the 1970’s – 1980’s, hard clams (Mercenaria mercenaria and M. campechiensis) can still be found in the sand along the shoreline and near seagrass beds. These clams are also known as Quahogs and are in the family Veneridae, commonly known as the Venus clam family, and contain over 500 living species. Most of the clams in the family Veneridae are edible and Quahogs are the types of clams you would see in a clam chowder or clam bake.
Being the only bivalve on this list does not make it any less important than the oyster or scallop on Part 1’s list. In fact, a full-grown adult Southern Quahog clam can filter upwards of 20 gallons of water per day and have a lifespan of up to 30 years. Clams also live a much different lifestyle than their oyster and scallop cousins. Clams spend the majority of their life under the sand. Their movement under the sand helps aerate and mix the soil, which can sometimes stimulate seagrass growth.
Right outside the Florida Panhandle and in the Big Bend area, Quahog clams are commercially farmed in Cedar Key. Southern Quahog clams are also being used for restoration work in South Florida. Clams are being bred in a hatchery and their “seed” are being released into Sarasota Bay to help tackle the Red Tide (Karenia brevis) issue. According to the project’s website, they have added over 2 million clams since 2016, and the clams are filtering over 20 million gallons of seawater daily.
Anemones
Tube-Dwelling Anemone Under Dissection Scope – UF/IFAS Shellfish
Anemones are beautiful Cnidarians resembling an upside-down, attached jellyfish, which couldn’t be closer to the truth. The phylum Cnidaria contains over 11,000 species of aquatic animals including corals, hydroids, sea anemones, and, you guessed it, jellyfish. Anemones come in many different shapes and sizes, but the common estuary anemones include the tube-dwelling anemone (Ceriantheopsis americana) and the tricolor anemone (Calliactis tricolor), also known as the hitchhiking anemone. If you have ever owned a saltwater aquarium, you might have run into the pest anemone Aiptasia (Aiptasia sp.).
Anemones filter feed with their tentacles by catching plankton, detritus, and other nutrients as the tide and current flows. The tentacles of the anemone are lined with cnidocytes that contain small amounts of poison that will stun or paralyze the prey. The cnidae are triggered to release when an organism touches the tentacles. If the anemone is successful in immobilizing the prey, the anemone will guide the prey to their mouth with the tentacles. Just like the barnacle, anemones are at the mercy of the tides and currents, and filtration rates are hard to calculate. However, if you ever see an anemone with food around, they move those tentacles to and from their mouths quickly and constantly!
In Parting
As you can see, there are many different natural filters in our estuary. Healthy, efficiently filtering estuaries are very important for the local community and the quality of the waters we love and enjoy. For more information on our watersheds and estuaries and how to protect them, visit Sea Grant’s Guide To Estuary-Friendly Living.
The University of Florida/IFAS Extension & Florida Sea Grant faculty are reintroducing their acclaimed “Panhandle Outdoors LIVE!” series on St. Joseph Bay. This ecosystem is home to some of the richest concentrations of flora and fauna on the Northern Gulf Coast. This area supports an amazing diversity of fish, aquatic invertebrates, turtles and other species of the marsh and pine flatwoods. Come learn about the important roles of ecosystem!
Registration fee is $40. You must pre-register to attend.
Recently I participated in a local festival to educate the public about the Rice’s Whale – the newly described species in the Gulf of Mexico that is now listed as critically endangered, possibly the most endangered whale in the world’s oceans. I honestly did not know enough about it to provide much education and chose to do terrapin conservation at my table instead (something I know more about) but have since learned much about this new member of the Gulf community.
One of the more frequent comments I heard during the event was “I did not know we even had whales in the Gulf”. This is understandable since we rarely see them – most of us have never seen one. When we think of whales we think of colder climates like Alaska, New England, and the colder waters off California. But many large whales must give birth to their smaller calves in warmer waters – so, they make the trek to tropical locations like Hawaii and Florida to do so. But there are also resident whales in the tropical seas.
You first must understand that the term “whale” does not only mean the large creatures of whale hunting fame, but any member of the mammalian order Cetacea. Cetaceans include both the large baleen whales – like the blue, gray, and right whales – but also the toothed whales – like the sperm, orca, and even the dolphins.
The Right whale is another critically endangered whale found in the Gulf of Mexico. Image: NOAA.
There are 28 cetaceans that have been reported from the Gulf, 21 of those routinely inhabit here. Most exist at and beyond the continental shelf – hence we do not see them. Only two frequent the waters over the shelf – the Atlantic Bottlenose Dolphin and the Atlantic Spotted Dolphin, and only one is routinely seen near shore – the Atlantic Bottlenose Dolphin.
This image shows the location of the continental shelf and thus the location of most of the whales found in the Gulf of Mexico. Image: NOAA.
But offshore, out at the edge of the continental shelf, exists several species of large and small cetaceans. The endangered Sperm, Sei, Fin, Blue, Humpback, and Northern Right whales have been seen. Of those only sperm whales are common. Others include several beaked whales (which resemble dolphins but are much larger), large pods of other species of dolphins, pygmy and dwarf sperm whales, pygmy and false killer whales (as well as the killer whale itself), and other baleen whales such as the Minke and Bryde’s whale.
The Bryde’s whale is one of interest to this story.
The Bryde’s whale (pronounced “brood-duss” – Balaenoptera edeni) is a medium sized baleen whale, reaching lengths of about 50 feet and weighing 30 tons. It is often confused with the larger sei whale. They are found in tropical oceans across the planet and are not thought to make the large migrations of many whales due to the fact it is already here in the tropics for birth, and its food source is here as well. They reside in the northeastern Gulf of Mexico extending from the DeSoto Canyon, off the coast of Pensacola, to the shelf edge near Tampa. They appear to travel alone or in small groups of 2-5 animals. They feed on small schooling fish, such as pilchards, anchovies, sardines, and herring. Their reproductive cycle in the Gulf is not well understood.
The Bryde’s whale was thought to be the only resident baleen whale in the Gulf of Mexico. Photo: NOAA.
Strandings have occurred – as of 2009, 33 have been logged. There are no records of mortality due to commercial fishing line entanglement, but vessel strikes have occurred. Due to their large population across the planet, they were not considered for listing under the Endangered Species Act, but that may change in the Gulf region due to human caused mortality. Between 2006-2010 it was estimated that 0.2 Bryde’s whales died annually due the vessel strikes.
In the 1960s Dr. Dale Rice described the Gulf of Mexico population as a possible subspecies. It is the only baleen whale that regularly inhabits the Gulf of Mexico. And ever since that time scientists examining stranded animals thought they may be dealing with a different species.
In the 1990s Dr. Keith Mullin began examining skull differentiation and genetic uniqueness from stranded animals of the Gulf population. Dr. Patricia Rosel and Lynsey Wilcox picked up the torch in 2008. In 2009 a stranded whale, that had died from a vessel strike, was found in Tampa Bay and provided Dr. Rosel more information. In 2019 a stranded whale, that had died from hard plastic in gut in the Everglades, was examined by Dr. Rosel and her team and, with data from this skull, along with past data, determined that it was in fact a different species. The new designation became official in 2019.
The newly described Rice’s whale only exists in the Gulf of Mexico. Photo: NOAA.
The new whale was named the Rice’s whale (Balaenoptera ricei) after Dr. Dale Rice who had first describe it as a subspecies in the 1960s. With this new designation everything changed for this whale. This new species only lives in the Gulf of Mexico, and it was believed there were only about 50 individuals left. Being a marine mammal, it was already protected by the Marine Mammal Protection Act, but with this small population it was listed as critically endangered and protected by the Endangered Species Act.
New reviews and publications began to come out about the biology and ecology of this new whale. Rice’s whales do exist alone or in small groups and currently move between the 100m and 400m depth line along the continental shelf from Pensacola to Tampa. Diet studies suggest that it may feed near the seafloor, unlike their Bryde’s whale cousins. They may have lived all across the Gulf of Mexico at the 100-400m line at one time. They prefer warmer waters and do not seem to conduct long migrations.
The area where the Rice’s whale currently exists. Image: NOAA.
Being listed under the Endangered Species Act, NOAA National Marine Fisheries (NMFS) was required to develop a recovery plan for the whale. NMFS conducted a series of five virtual workshops between October 18 and November 18 in 2021. Workshop participants included marine scientists, experts, stakeholders, and the public. There were challenges identified from the beginning. Much of the natural history of this new whale was not well understood. Current and historic abundance, current and historic distribution, population structure and dynamics, calving intervals and seasonality, diet and prey species, foraging behavior, essential habitat features, factors effecting health, and human mortality rates all needed more research.
At the end of the workshop the needs and recommendations fell into several categories.
Management recommendations
Create a protected area
Restrict commercial and recreational fishing in such – require ropeless gear
Require VMS system on all commercial and recreational vessels
Require reporting of lost gear and removal of ghost gear
Risk assessment for aquaculture, renewable energy, ship traffic, etc.
Prohibit aquaculture in core area and suspected areas
Reduce burning of fossil fuels
Prohibit wind farms in core area
Renewable energy mitigation – reduce sound, night travel, passive acoustic
Develop spatial tool for energy development and whale habitat use
Require aquaculture to monitor effluent release
Develop rapid response focused on water quality issues
Develop rapid response to stranding events
Reduce/cease new oil/gas leases
Reduce microplastics and stormwater waste discharge
Work with industry to use technologies to reduce noise
Reduce shipping and seismic sound within the core area
Restrict speed of vessels
Maintain 500m distance – require lookouts/observers while in core
Consider “areas to be avoided”
Monitoring recommendations
Long-term spatial monitoring
Long-term prey monitoring
Electronic monitoring of commercial fishing operations
Necropsies for pollution and contaminants
Outreach and Engagement are needed
Top Threats to Rice’s Whale from the workshop Include:
Small population size – vessel collisons
Noise
Environmental pollutants
Prey – Climate change – marine debris
Entanglement – disease – health
Offshore renewable energy development
The Endangered Species Act (ESA) requires the designation of critical habitat for listed species. In July 2023 NOAA proposed the area along the U.S. continental shelf between 100-400 meters depth as critical habitat. Comments on this designation were accepted through October 6, 2023.
The proposed protection zone for the Rice’s whale including the core area. Image: NOAA.
Vessel strikes are a top concern. It is understood that the most effective method of reducing them is to keep vessels and whales apart and reduce vessel speeds within the approved critical habitat.
On May 11, 2021, NOAA Fisheries received a petition submitted by five nongovernmental agencies and one public aquarium to establish a year-round 10-knot vessel speed limit in order the protect the Rice’s whale from vessel collisions. The petition included other vessel mitigation measures. On April 7, 2023, NOAA published a formal notice in the Federal Register initiating a 90-day comment period on this petition request. The comment period closed on July 6, 2023, and they received approximately 75,500 comments. After evaluating comments, and other information submitted, NOAA denied the petition on October 27, 2023.
NOAA concluded that fundamental conservation tasks, including finalizing the critical habitat designation, drafting a species recovery plan, and conducting a quantitative vessel risk assessment, are all needed before we consider vessel regulations. NOAA does support an education and outreach effort that would encourage voluntary protection measures before regulatory ones are developed.
On that note, the Bureau of Ocean Energy Management (BOEM) did issue voluntary precautionary measures the industry could adopt to help protect the Rice’s whale. These include:
Training observers to reduce vessel collisions.
Documenting and recording all transits for a three-year period.
All vessels engaged in oil and gas, regardless of size, maintain no more than 10 knots and avoid the core area after dusk and before dawn.
Maintain 500m (1700 feet) distance from all Rice’s whales.
Use automatic identification system on all vessels 65’ or larger engaged in oil and gas.
These suggestions would not apply if the crew/vessel are at safety risk.
So…
This is where the story is at the moment…
This is what is up with the Rice’s whale in the Gulf of Mexico.
2 Rosel, P.E., Mullin, K.D. Cetacean Species in the Gulf of Mexico. DWH NRDA Marine Mammal Technical Working Group Report. National Marine Fisheries Service. Southeast Fisheries Science Center.
7BOEM Issues Voluntary Precautionary Measures for Rice’s Whale in the Gulf of Mexico. 2023. U.S. Department of Interior. Bureau of Ocean Energy Management.
8NOAA Fisheries Denies Petition to Establish a Mandatory Speed Limit and Other Vessel Mitigation Measures to Protect Endangered Rice’s Whales in the Gulf of Mexico. NOAA Fisheries News. FB23-079. Gulf of Mexico Fishery Bulletin. October 27, 2023.
The Panhandle of Florida is home to many estuaries along the coast, from the Escambia Bay System in the west to the Apalachicola Bay System in the east. These estuaries are very important and are the intersection where rivers (fed from their respective watersheds) meet the Gulf of Mexico and contain many different organisms that help filter the waters before they reach the Gulf. These organisms include oysters, marsh plants, seagrasses, scallops, tunicates, and other invertebrates. In this two-part article, we will explore marsh plants, seagrasses, oysters, and scallops.
Marsh Plants
Marsh Plants is a broad term for a family of grasses that lines the shore and contain grasses like Smooth Cordgrass (Spartina alterniflora), Saltgrass (Distichlis spicata), and Gulf Cordgrass (Spartina spartinae). These plants help trap sediments before they enter the estuary and are excellent at erosion prevention. When the water encounters the plants, it slows the flow, and this allows for sediments to collect. Marsh Plants are a great tool for shoreline restoration and are a major part of the Living Shorelines Program. The roots of the plants are also very efficient at removing nutrient pollutants like excess nitrogen and phosphorus which are major influencers in eutrophication. Marsh Plants also absorb carbon dioxide from the atmosphere and have been tabbed as “superstars of CO2 capture and storage.” (CO2 and Marsh Plants)
Marsh Grass and Oyster Reef in Apalachicola, Florida – Thomas Derbes II
Seagrasses
Seagrasses are different than Marsh Grasses (seagrasses are ALWAYS submerged underwater), but they offer some of the same ecological services as Marsh Grasses. The term seagrasses include Turtle Grass (Thalassia testudinum), Shoal Grass (Halodule wrightii), Widgeon Grass (Ruppia maritima), and Manatee Grass (Syringodium filiforme) to name a few. Seagrasses help maintain water clarity by trapping suspended sediments and particles with their leaves and uptake excess nutrients in their roots. Seagrasses are very efficient at capturing carbon, capturing it at rates up to 35 times faster than tropical rainforests. (Carbon Capture and Seagrasses) They also provide habitat for crustaceans, fish, and shellfish (which can filter the water too) and food for other organisms like turtles and manatees.
Grassbeds are also full of life, albeit small creatures. Photo: Virginia Sea Grant
Oysters
Crassostrea virginica (or as we know them, the Eastern oyster) is a native species of oyster that is commonly found along the eastern coast of the USA, from the upper New England states all the way to the southernmost tip of Texas. Eastern oysters are prolific filter feeders and can filter between 30-50 gallons of water per day. As filter feeders, they trap nutrients like plankton and algae from the environment. In areas of high eutrophication, oysters can be very beneficial in clearing the waters by trapping and consuming the excess nutrients and sediments and depositing them on the bottom as pseudo-feces. With oyster farms popping up all over the Gulf Coast, the filtering potential of estuaries is on the rise. (Between the Hinge)
Oysters, The Powerful Filterers of the Estuary – Thomas Derbes II
Scallops
Bay Scallops (Agropecten irradians) were common along the whole Florida Gulf Coast, but their numbers have taken a recent decline and can only be found in abundance in the estuaries to the east of St. Andrews Bay in Panama City, Florida. Scallops make their home in seagrass beds and are filter feeders. While scallops do not contain the filtering potential of an oyster (scallops filter 3 gallons of water per day as an adult), they are still a key part of filtering the estuary. Just like oysters, scallops feed off of the suspended particles and plankton in the water column and deposit them as pseudo-feces on the bottom. The pseudo-feces also help provide nutrients to the seagrasses below.
Bay Scallop. Photo: FWC
I hope you enjoyed this first article on filterers in the estuary system. While oysters are known as the filterers of the estuary, I hope this has opened your eyes to the many different filterers that call our estuary home. Stay tuned for Part 2!
Organized and sponsored by Florida Sea Grant, the “Stem to Stern” workshop in November 2023 at the Emerald Coast Convention Center marked a significant gathering in marine conservation and management. This event drew together legal experts, representatives from the Florida Fish and Wildlife Conservation Commission (FWC), local marine resource coordinators, law enforcement, and industry stakeholders to tackle critical issues facing Florida’s marine environments. Through discussions that ranged from legal frameworks for boating and waterway access to environmental conservation strategies, the workshop facilitated a deep dive into the complexities of marine policy and stewardship. Discover new programs, insights, and collective expertise shared at “Stem to Stern.”
Florida Sea Grant Boating and Waterways Workshop
November 2, 2023 Emerald Coast Convention Center
1250 Miracle Strip Parkway SE – Ft. Walton Beach FL
9:00 – 9:25 WELCOME AND INTRODUCTIONS
Welcome
Rick O’Connor (Florida Sea Grant UF IFAS Extension)
Moderators –Mike Norberg and Jessica Valek (Okaloosa County)
3:15 – 3:45 WRAP UP – Robert Turpin (Escambia County Marine Resources)
PROGRAM SPONSORS
Acknowledgement
We extend our deepest gratitude to all who contributed to the success of the “Stem to Stern” workshop. To our esteemed speakers, whose expertise and insights into marine conservation and management have been invaluable, we offer our sincere thanks. Your presentations were not only informative but also inspirational, guiding us toward a more sustainable future for our waterways.
A special acknowledgment goes to the members of the planning and program committee. Your dedication and hard work in organizing this event did not go unnoticed. From the initial planning stages to the execution of the workshop, your efforts have been the backbone of this successful gathering.
We also want to thank the authors of the surveys that have provided us with essential data and perspectives. Your research and analysis contribute significantly to our understanding of the challenges and opportunities within Florida boating and waterways.
Lastly, we are incredibly grateful for the support from our sponsors. Your generosity and commitment to Florida Sea Grant and marine conservation have been crucial in bringing this workshop to life. Your support not only made this event possible but also highlights your dedication to safeguarding our marine ecosystems.
Together, we have taken an important step towards protecting and enhancing Florida’s waterways. Thank you for your contributions, commitment, and shared vision for a sustainable future.
Information edited and compiled by: L. Scott Jackson, Chantille Weber, and Amon Philyaw, UF/IFAS Extension Bay County
An Equal Opportunity Institution. UF/IFAS Extension, University of Florida, Institute of Food and Agricultural Sciences, Andra Johnson, Dean. Single copies of UF/IFAS Extension publications (excluding 4-H and youth publications) are available free to Florida residents from county UF/IFAS Extension offices.
The leatherback sea turtle is the largest of the five species that have been found in the northern Gulf of Mexico. With a carapace (top shell) length between 6-7 feet and weighing between 800-1000 pounds it is truly a magnificent creature. Any encounter with them is amazing.
Most encounters occur with fishermen or divers who are out searching for artificial reefs to fish or dive. Though very rare, they have been known to nest in this area. They feed exclusively on jellyfish and will follow them close to shore if need be. But what do leatherbacks do with most of their time? Do they hang offshore and follow jellyfish in? Do they circle the entire Gulf of Mexico and we see them as they pass? Based on past studies, many encounters with this turtle occur in the warmer months. They often become entangled in commercial fishing longlines set in the central Gulf of Mexico. But what do they do during the fall and winter? One of the tagging projects presented at a recent workshop tried to answer that question.
The project was led by Dr. Christopher Sasso of the National Oceanic and Atmospheric Administration. The tag chosen for this was a satellite tag. Since the leatherback must surface to breath air, and often is found near the surface following jellyfish, orbiting satellites would be able to follow them. As we mentioned in Part 1, catching the creature is step 1, and catching a six-foot 1000-pound sea turtle is no easy task.
The team used a spotter aircraft to locate the turtles. Once found, the pilot would radio the chase boat who would zip in with a large net. The net was connected to a large metal hoop and was designed to give way once it was around the turtle. Once in the net the turtle was hauled onto a small inflatable boat where the work of tagging could be done. They would measure the animal, take blood samples, place a PIT tag within them (similar to a microchip in your pet) and then attach the satellite tag by a tether to the tail end of the turtle before releasing it. The entire operation took less than 30 minutes.
Between 2015-2019 19 leatherbacks were tagged in the northern Gulf. 17 of these were females and 2 were males. Data obtained from these tags ranged between 63 and 247 days at liberty. The behavior the team noticed was divided into foraging behavior (feeding on jellyfish) and transiting behavior (direct swimming ignoring all).
The turtles foraged in this part of the Gulf until the fall season. At that point most of them moved south along the Florida shelf, past the western peninsula of the state, heading towards the Keys. A few chose to swim directly south against the Loop Current, and a small number remained in the area.
Those moving along the Florida shelf appeared to be foraging as they went. Those crossing the open Gulf may have foraged some but seemed to be focused on getting south to the nesting beaches. Almost all of the turtles entered the Caribbean on the east side of the Yucatan channel, following the currents, with their final destination being their nesting beaches. When they returned, they did so in the warmer months and used the western side of the channel – again following the currents – until they once again reached the northern Gulf and foraging began again. One interesting note from this study, the two males tagged did not leave the Gulf.
The tagging studies do show that leatherbacks use the Gulf of Mexico year-round. They usually head south to the Caribbean when it gets colder and use the currents to do so. It is during the warmer months we are most likely to see them here foraging on jellyfish. It is an amazing experience to encounter one of these large turtles. I hope you get to experience it one day.
Satellite tracks of leatherback movement in the GoM. Red (2015), Blue (2018), Black (2019).
Image: Sasso (et.al.) 2021.
Reference
Sasso, C.R., Richards, P.M., Benson, S.R., Judge, M., Putman, N.F., Snodgrass, D., Stacy, B.A. 2021. Leatherback Sea Turtles in the Eastern Gulf of Mexico: Foraging and Migration Behavior During the Autumn and Winter. Frontiers in Marine Science., Vol. 8., https://doi.org/10.3389/fmars.2021.660798.
