Occurrence of five non-native and invasive taxa on natural and artificial reefs within the Florida Keys National Marine Sanctuary

Florida's subtropical climate and diverse coastal habitats support an exceptionally high level of biological diversity. Hosting an already diverse array of native taxa, South Florida's waters also have one of the highest EAS (established alien species) richness values in the world (Dawson et al., 2017). Alien species may be categorized as non-native or invasive, depending on their ecological impacts (Colautti and Maclsaac, 2004;Mooney and Cleland, 2001;National Park Service, n.d.;Schlaepfer et al., 2011). Colautti and Maclsaac (2004) argue that alien species are only considered to be "invasive" if they have spread beyond the point of introduction and have documented negative ecological or socioeconomic impacts. Colautti and Maclsaac (2004) further state that a species' invasion effect should be evaluated at the population level, rather than assigning a label to the entire species. Here, "non-native" species are defined as those species that are able to coexist within foreign ecosystems without causing a negative impact (National Park Service, n.d.) and may even provide conservation benefits, such as providing habitat or food for native species or contributing to ecosystem services no longer provided by extinct species (Schlaepfer et al., 2011). "Invasive species", on the other hand, are defined here as those populations of species that are known to play a deleterious role in the ecosystems they occupy by outcompeting native species, and possibly fueling native species' displacement (Colautti and Maclsaac, 2004;Mooney and Cleland, 2001).To date, over 4,450 artificial reefs have been deployed off Florida's coast since 1944 (Florida Fish and Wildlife Conservation Commission, n.d.), many of them being decommissioned U.S. Coast Guard, U.S. Navy, or civilian tanker vessels. When these ships are first submerged, they are quickly colonized by alien species (Paxton et al., 2024), which tend not to have natural predators and/or prefer unoccupied ecological niches and habitats. According to Soares et al. (2020), shipwrecks may act as protection for hard-to-remove non-native species, like Tubastraea spp. (described further below), and unintentionally allow them to reproduce and expand their range.The Florida Keys National Marine Sanctuary (FKNMS) was established in 1990 and is one of the largest and most economically important marine protected areas (MPAs) in the U.S., currently encompassing over 4,500 square miles of coastal and offshore waters and supporting billions of dollars in tourism from the use of thousands of residents and millions of visitors annually (Department of Commerce, National Oceanic and Atmospheric Administration, 2025). Ecologically, the FKNMS provides habitat for more than 6,000 species of fish, invertebrates, and plants (Department of Commerce, National Oceanic and Atmospheric Administration, 2025), as well as several species of seabirds, marine mammals, and reptiles. Natural habitats in the FKNMS include coral reefs, seagrass meadows, and mangrove forests (Department of Commerce, National Oceanic and Atmospheric Administration, 2025), as well as various types of artificial ecosystems, including hundreds of shipwrecks (NOAA Florida Keys National Marine Sanctuary, n.d.(b)) and three underwater habitats deployed, which allow for the sustained human presence underwater: Aquarius Reef Base, Jules' Undersea Lab, and the Vanguard Underwater Habitat.Globally, the FKNMS has been further recognized as one of the most well-known and unique MPAs in the world due to supporting formal marine science (Brittsan et al., 2023;O'Donnell et al., 2017;Toth et al., 2025), space analog training (Chamberland & Carpenter, 1996;Henke et al., 2025;Miller & Cooper, 2000;Todd & Raegan, 2003;Vannini & Vannini, 2025), high biological diversity, vast cultural richness, and a substantial economic value (Department of Commerce, National Oceanic and Atmospheric Administration, 2025). Research and updated data reports on non-native and invasive species and their specific populations in FKNMS are important to better understand their impacts and interactions with native species and ecosystems, and to assist with sanctuary management.One of the most iconic examples of invasive taxa in the FKNMS are the lionfishes (Pterois spp.), which originate from the tropical waters of the Indo-Pacific. Pterois spp. were first reported off the coast of Florida in 1985, and their spread has been one of the most documented cases of an invasive marine genus in history (Schofield, 2010;Côté and Smith, 2018). The leading theory for the source of their invasion is attributed to either intentional or unintentional aquarium releases of this genus (Semmens et al., 2004). Lionfish are generalist carnivores that prey upon smaller reef fish, invertebrates, and juveniles of larger bony fish species, including groupers (Peake et al., 2018;Albins and Hixon, 2008). Their predation on lower trophic levels and juveniles of native reef predators has been documented to negatively affect local reef ecosystems (Côté et al., 2013). Additionally, their prolific reproductive rates and lack of native predators have allowed these fishes to thrive in the Western Atlantic ecosystems (Willard, 2024;Blakeway et al., 2022). In the FKNMS, two lionfish species, P. miles and P. volitans, are documented to be established (Huge et al., 2014;Ruttenberg et al., 2012). While meristic differences have been noted, these two species are difficult to distinguish visually in the field (Schultz, 1986).To date, two species of non-native stony coral, Tubastraea coccinea and T. tagusensis, have also been documented in the FKNMS. Tubastraea is a genus of ahermatypic corals that originate in the Indo-Pacific and have spread into the Western Atlantic through introduction into Puerto Rican waters via ship ballast (Lages et al., 2011). Tubastraea are azooxanthellate and rely on feeding on particulate matter carried by water currents (Luz et al., 2020). Most research on this genus has been conducted off Brazil, focusing on the same two species (Ohanna et al., 2025;Riul et al., 2013;Creed et al., 2021). A third species, T. faulkneri, has also been identified within southwestern Atlantic waters and is meristically similar to T. coccinea, but as of 2026 is not yet documented in the FKNMS. Tubastraea was first introduced into the Atlantic in 1943, where it was found in Puerto Rico, before moving throughout the Western Atlantic and onto natural substrates (especially rockyintertidal zones) by 2004 (Riul et al., 2013). Tubastraea was first recorded in the FKNMS in 1999 on the wreck of the USCGC Duane (Fenner and Banks, 2004). The many artificial reefs in South Florida's waters could potentially be acting as vectors for Tubastraea to begin recruiting onto natural substrates (Precht et al., 2014), but this has yet to be investigated or documented. In the Flower Garden Banks National Marine Sanctuary, isolated communities of Tubastraea were removed from natural substrates but were observed repopulating the area post-removal (Precht et al., 2014). To date, the U.S. has not experienced the same mass habitat expansion of Tubastraea that has been observed off Brazil (Precht et al., 2014). Since Tubastraea is believed to prefer areas with lower coral cover (Wood, 1983), the recent mass Scleractinia coral die-off events in the FKNMS could have potentially created more favorable, shallower, organic habitats for Tubastraea to occupy; however, additional research is needed to investigate this hypothesis. Additionally, while Tubastraea has been found to outcompete native species and significantly modify the benthic communities in the other parts of the Atlantic and Caribbean where they have recruited (Hennessy and Sammarco, 2014;Lages et al., 2011;Ohanna et al., 2025), these adverse impacts or effects have not yet been observed or recorded in FKNMS. Therefore, from the definitions presented above, the Tubastraea populations in FKNMS would be defined as "non-native" as opposed to "invasive".Other alien taxa which have been documented in the greater Tropical Western Atlantic Region include the genus Unomia, also known as "pulsing corals", and the family Xeniidae. Unomia stolonifera is thought to have been first introduced into the Western Atlantic off the coast of Venezuela through the aquarium trade between 2000and 2005(Ruiz-Allais et al., 2014). This octocoral is characterized by its "pulsing" or active polyps, which remain open to feed. Xeniids are thought to be opportunistic colonizers of degraded reefs (Tilot et al., 2008), which have become increasingly common given the devastating bleaching events over the last couple of decades, and are known to overgrow and outcompete important native Scleractinia species, including Orbicella annularis and Montastraea cavernosa (Ruiz-Allais et al., 2014). Since U. stolonifera's original introduction off Venezuela, U. stolonifera has invaded reefs and covered 30-80% of the substrate (Ruiz-Allais et al., 2021). Similarly, in 2023, the species Xenia umbellata was recently identified on a shallow reef off Puerto Rico (Toledo-Rodriguez et al., 2024). X. umbellata is similar to U. stolonifera in its ability to dominate reefs, outcompete native species, and survive extreme conditions (Toledo-Rodriguez et al., 2024). While neither species has yet to be identified within the FKNMS, their invasive nature and spread throughout the Atlantic over the past two decades pose a grave threat to the already depleted and degraded reefs within the Florida Keys.Halophila stipulacea was recently identified just north of the FKNMS' boundary in Biscayne National Park at the end of 2024. This seagrass is native to the Red Sea and can survive a number of rapidly changing conditions (Campbell et al., 2024). Native seagrass meadows form the basis of the food webs, provide shelter for juveniles, and serve as feeding grounds for Endangered Species Act (ESA)-listed megafauna, including sea turtles and the West Indian manatee (Trichechus manatus latirostris), which makes the potential introduction of H. stipulacea to these ecosystems a concern.Here, the presence or absence of the five (5) non-native and potentially invasive marine taxa described above in the FKNMS was documented. These specific taxa were selected because they are either already known to be present within the FKNMS, have been recently identified in nearby waters, or because they may pose threats to native species. Thus, a better understanding of their presence at sites within the FKNMS is needed to help inform future response, control, and removal plans.Data were collected opportunistically from commonly visited dive sites of commercial dive operators over a 13-month period (July 2025 through August 2026). All sites visited were on the Atlantic coast of Florida and were comprised of similar depths and habitat profiles (i.e., artificial and natural). Survey methods entailed SCUBA diving or snorkeling during daylight hours, utilizing the roving diver method (Schmitt et al., 2002) and by following either a linear out and back or expanding circle search pattern. Dive surveys at any given site ranged from 39 to 55 minutes, covering the greatest practical spatial extent within standard recreational diving safety limits. Private boats were utilized to survey sites within the Conch Reef and Tennessee Reef Special Use [Research Only] Areas, the Tennessee Reef Light, and the Thunderbolt wreck, due to the difficulty of reaching these sites or permit restrictions. Deep (≥18m) and artificial reef sites were specifically chosen and visited based on the availability of divers and dive shops. A priority was placed on visiting as many deep, artificial sites within the Atlantic coast of the FKNMS as possible, as they are known to act as vectors which aid in the spread of alien species populations (Soares et al., 2020). Sites at the northern and southern extremes of the FKNMS boundary (i.e., north of Carysfort Reef or south and west of the Marquesas or Dry Tortugas regions) were not surveyed, as few to no commercial dive operators regularly visit these areas.For each site visited, date, site name, and GPS coordinates were recorded, as well as the: (a) presence of any target genera, (b) identity of the target organism to the genus level, and (c) the maximum depth of the site. Photo-documentation and depth of target genera presence were also collected. Sites were later categorized by type, as either natural or artificial, and binned by maximum depth (shallow <18m; deep ≥18m).The dataset contains the date surveyed, site name, and the GPS coordinates of a total of 62 unique sites within the FKNMS that were visited, as well as the presence or absence of the target taxa, and other site-specific information including substrate type and maximum depth surveyed. The dataset further categorizes each site as natural (n = 46) or artificial (n = 16), and shallow ("s", n = 46) or deep ("d", n = 16) sites. The spatial distribution and presence of target taxa at the sites are presented in Figure 1, Image A.At least 1 target taxon was recorded during 22 surveys (35.5%). Pterois spp. (Figure 1, [Image B]) observations occurred during 18 surveys (29.0%), and Tubastraea spp. (Figure 1, [Image C & D]) were observed during 9 surveys (14.5%). No Xeniids or H. stipulacea were documented at any site. At least 1 target taxon was present at 10 of 40 natural-shallow sites, 2 of 6 natural-deep sites, 0 of the 6 artificial-shallow sites, and all 10 artificial-deep sites. These descriptive summaries are provided to illustrate the structure and potential analytical uses of the dataset rather than to test specific ecological hypotheses. Counts and occurrence percentages by site type and depth category are provided in Table 1.It is important to note that the Vanguard Underwater Habitat was surveyed approximately 1 month after its deployment (DEEP, 2026;Page, 2026), which was insufficient time for target sessile species recruitment.Utilizing commercial dive operators to access the sanctuary and complete this dataset maximized the data collected and provided randomization and variability in site selection, as commercial dive operators regularly visit the sanctuary's designated Sanctuary Preservation Areas (SPAs) and popular shipwreck sites. It should be noted that SPAs in FKNMS have been statutorily designated to promote sustainable access and use of these ecologically important and sensitive areas to the public while simultaneously providing these identified sites with the highest level of protection and conservation. Therefore, to produce as many data points and create the largest spatial distribution possible, all sites visited aboard commercial diver operations were included in this dataset.This data report has utility in that it provides sanctuary managers with a snapshot of target taxa distribution throughout much of the FKNMS. Knowledge of the geolocation and substrate types utilized by invasive and non-native species studied may inform models that predict their potential spread. Additionally, this dataset may be useful to the FKNMS resource protection managers when developing invasive species risk assessments, control or containment plans, and removal intervention plans. More broadly, other uses of this dataset can be extended into coral reef restoration applications, which are commonly practiced throughout the FKNMS, and other user groups (i.e., spearfishermen interested in hunting for lionfish).This dataset is the first scientific documentation of Tubastraea spp. occurring on shipwrecks or other types of artificial reef sites within FKNMS since the first report of the genus within the sanctuary on the USCGC Duane in 1999 and the Aquarius Reef Base in 2014 (Fenner & Banks, 2004;NOAA FKNMS, n.d.(a); Precht et al., 2014). Despite its presence within the FKNMS for decades, Tubastraea and its impacts on native species and habitats remain understudied. These data may assist in understanding how Tubastraea has spread and the potential abiotic factors which limit its further expansion onto natural and shallow sites within the FKNMS.The taxa not documented during this survey (Halophila stipulacea, Unomia stolonifera, and Xenia umbellata) were originally considered because they were known to occur in nearby waters, but were not yet known to be present within the FKNMS. Vigilance for these taxa in the FKNMS is recommended as they are known to rapidly overtake benthic habitats and outcompete native species (Campbell et al., 2024;Ruiz-Allais et al., 2014).The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. 8 Tables Table 1. Invaded sites by depth and site type.