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Proportions of manatees in the Atlantic Coast and Southwest Florida subpopulations at power plants, natural springs, thermal basins, and other sites during synoptic surveys from 1999 to 2011. (Bars indicate the number of manatees counted each year over the 13-year study period; no survey was conducted in 2008.) doi:10.1371/journal.pone.0058978.g005
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To survive cold winter periods most, if not all, Florida manatees rely on warm-water refuges in the southern two-thirds of the Florida peninsula. Most refuges are either warm-water discharges from power plant and natural springs, or passive thermal basins that temporarily trap relatively warm water for a week or more. Strong fidelity to one or more...
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To survive cold winter periods most, if not all, Florida manatees rely on warm-water refuges in the southern two-thirds of the Florida peninsula. Most refuges are either warm-water discharges from power plant and natural springs, or passive thermal basins that temporarily trap relatively warm water for a week or more. Strong fidelity to one or more...
Most Florida manatees depend on localized warm-water refuges in the southern two-thirds of Florida to survive winter; about 60% use outfalls from 10 power plants, whereas 15% use 4 natural warm-water springs. Future availability of these refuges is in doubt; most of these power plants may be retired within the next 20 years and groundwater withdraw...
To survive cold winters, Florida manatees (Trichechus manatus latirostris) depend on artificial (i.e., power plants) and natural warm water sources such as springs and passive thermal basins. Passive thermal basins can provide critical habitat for manatees for short or extended periods of time. The Henry D. King Powerplant in Fort Pierce, Florida d...
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... The flow along such heterogeneities that intersect the land surface is expressed as hillslope and riparian springs. Groundwater springs supplying stable baseflow to streams in areas of permeable bedrock have long been recognised as an important source of water supply, temperature refuge for aquatic species (Laist et al. 2013), and as a foundation for diverse ecological habitats (Springer and Stevens 2009). These discrete groundwater discharge zones create focused recharge to stream baseflow that becomes particularly dominant under low-flow conditions. ...
The dynamic storage of aquifers is the portion of groundwater that can potentially drain to any given point along a stream to create baseflow. Baseflow typically occurs year‐round in perennial streams, though the characteristics and stability of dynamic storage are often most important to instream processes during extended dry periods (without precipitation and snowmelt) when runoff and quickflows are minimised. The term ‘baseflow resilience’ is defined for this review as the tendency of baseflow in streams to maintain a consistent volume and water quality year to year while under stress from climate variability and extremes, along with anthropogenic stressors such as water withdrawals, land use change, and water quality degradation. ‘Baseflow resilience’ has, in part, a user‐defined meaning spanning water supply and water quality variables of primary interest. Watershed characteristics that directly impact resilience can often produce non‐intuitive feedbacks that enhance some attributes of baseflow while simultaneously impairing others. For example, permeable stream corridor geology creates strong stream‐groundwater hydrologic connectivity, yet fast groundwater drainage via preferential high‐permeability flowpaths can lead to streamflow not being sustained during extended dry periods. Also, shallow groundwater sources are generally more immediately vulnerable to extreme events, warming, salinization, transpiration, and precipitation drought, compared to deeper groundwater. Yet baseflow drought in streams influenced by deeper groundwater can lag precipitation drought by years, and contaminant legacies may propagate through deep groundwater flowpaths to receiving waters for decades to centuries. Finally, irrigation withdrawals can intercept groundwater that would have drained to streams, and the application of irrigation may leach contaminants from the soil zone by unnaturally raising water tables, yet irrigation return flows can sustain baseflow and groundwater‐dependent habitats in semiarid areas. This review covers the concept of hydrologic resilience in the context of stream baseflow processes and summarises the common hydrogeological controls on, and multiscale stressors of, dynamic groundwater storage. Further, we present several quantitative metrics to assess a range of water supply to water quality baseflow characteristics using both broadly available and boutique data types, a subset of which are demonstrated using data from the Delaware River Basin, USA.
... Thermal pollution is a mixed bag. In Florida, approximately 50% of manatees winter in the thermal outflow of coastal power plants (Laist et al., 2013). Conversely, discharge from two nuclear power plants increased water temperatures by up to 1.5°C with effects, albeit very small ones, still detectable up to 6 km downstream (Zoran et al., 2012). ...
Question: How can nuclear power and nuclear inclusive environmentalism maintain and return land to the preservation of biodiversity? Premises: (1) It's all about energy in terms of us (humans) and nature. (2) We have absconded with most of the available sunlight via land conversion, crops, lumber, pets, livestock, and harvest of non-domesticated species. (3) We will continue to use more, not less, energy. (4) We must channel more, not less, sunlight toward preserving and enhancing biodiversity. (5) Fossil fuels use "fossil" sunlight rather than current sunlight, but present harsh externalities for humans and biodiversity. (6) Renewable energy (hydro, wind, and solar) reduce carbon emissions, yet impose negative externalities for biodiversity. (7) Nuclear power may not always be the best option for humanity independent of preserving biodiversity. (8) Nuclear waste and disasters have spawned a fallacy regarding externalities insofar as externalities for nature are primarily positive. Conclusions: Nuclear power provides the best option for preserving biodiversity. Nuclear power imposes the smallest land footprint (c. 2-3 km 2 /TWh/year) when compared to fossil fuels (c. 10-45 km 2 /TWh/year), renewables (c. 35-70 km 2 /TWh/year), and biofuels (250-900 km 2 /TWh/ year). If the price for nuclear power drops 50-75%, then it becomes economical to artificially synthesize rather than grow carbohydrates. Using nuclear power along coastlines for water desalination could restore rivers, wetlands, and return massive amounts of fresh water toward promoting biodiversity. Finally, there is an inversion of externalities. While nuclear accidents, leakages, and waste can and have caused demonstrable harm to humans, the easements and exclusion zones created for safety from actual or potential hazards permit space for rewilding. Judicious coordination of nuclear power expansion and biodiversity easements offer our best chance of ending the biodiversity crisis by returning space, water, and sunlight to non-human-dominated nature.
... Manatees in subtropical latitudes need warm water to regulate their body temperature and avoid cold-induced stress and mortality. When temperatures decrease in Florida, manatees typically migrate to warm water sources at power plants (warm water outputs used to cool power generation sources), passive thermal basins, and natural artesian springs (Laist et al., 2013;Sattelberger et al., 2017). The presence of power plants along the Florida coastline has allowed manatees to expand their range further north, but animals have become dependent upon such warm water sources during cooler winter months (Laist & Reynolds, 2005;Laist et al., 2013). ...
... When temperatures decrease in Florida, manatees typically migrate to warm water sources at power plants (warm water outputs used to cool power generation sources), passive thermal basins, and natural artesian springs (Laist et al., 2013;Sattelberger et al., 2017). The presence of power plants along the Florida coastline has allowed manatees to expand their range further north, but animals have become dependent upon such warm water sources during cooler winter months (Laist & Reynolds, 2005;Laist et al., 2013). Power plants supply thermal refuges for significant numbers of manatees when water temperatures decrease and lessen the potential for manatee mortalities related to cold-stress syndrome (Laist & Reynolds, 2005;Laist et al., 2013). ...
... The presence of power plants along the Florida coastline has allowed manatees to expand their range further north, but animals have become dependent upon such warm water sources during cooler winter months (Laist & Reynolds, 2005;Laist et al., 2013). Power plants supply thermal refuges for significant numbers of manatees when water temperatures decrease and lessen the potential for manatee mortalities related to cold-stress syndrome (Laist & Reynolds, 2005;Laist et al., 2013). A study found that 48.5% of manatees counted across Florida during winter months depend on power plant outputs for warmth, with manatees in the Southwest Florida and Atlantic Coast subpopulations relying on power plants more heavily than others (Laist et al., 2013). ...
Sirenians are experiencing unprecedented anthropogenic threats around the globe due to habitat destruction, interaction with fisheries, collisions with watercrafts, and climate change. Although the West Indian manatee (Trichechus manatus) has been protected by law for the past five decades, significant threats persist in the United States. In 2017, the US Fish and Wildlife Service (USFWS) downlisted the West Indian manatee from Endangered to Threatened under the Endangered Species Act of 1973 (ESA). Here, we provide an overview of the current conservation status of manatees in US waters, particularly in Florida and Puerto Rico. In recent years, there has been a marked increase in manatee mortalities in the US. The sources of these mortalities are relatively well known, particularly collisions with watercrafts. However, other sources have recently emerged and constitute threats of increasing concern, particularly resource depletion due to seagrass loss and emerging diseases. Recommendations for future research are proposed to improve our understanding of the magnitude of the threats affecting manatees in the US, and support management decisions and conservation actions.
... The Florida manatee is highly susceptible to various anthropogenic threats, including those stemming from boat traffic (Bassett et al., 2020;Edwards et al., 2016) and tourism (Sorice et al., 2003). They are drawn to the warm water refuges provided by power plants and natural springs during winter months when temperatures drop below their tolerance threshold of 20 C (Laist et al., 2013;Laist & Reynolds, 2005 (Buckingham et al., 1999;Slone et al., 2023) and used protected (no-entry) sanctuaries more frequently (King & Heinen, 2004) when the number of boats and swimmers increased. Additionally, manatees in this area face the risk of harassment, as visitors may try to touch and chase them in an attempt to interact with the animals (Sorice et al., 2003). ...
Wildlife tourism often focuses on marine mammals, and the growing frequency of human interactions raises concerns about the sustainability of these activities and their impact on aquatic species. Tourists have the opportunity to view the Florida manatee ( Trichechus manatus latirostris ) in various locations; however, the level of tourist activity in some areas and their effects on manatees are unknown. Preliminary studies are essential to assess whether these areas warrant additional regulatory and mitigation strategies based on tourism impact.
Here, we investigated tourism activity on a site often visited by small aggregations of Florida manatees. From 2022 to 2023, interviews, citizen science, and trail cameras were used to assess watercraft activity, tourist knowledge, and the educational practices offered by watercraft rental businesses at Portosueno Park, Florida, USA.
Both trail cameras and citizen science revealed that boats were the most common visitors to the park, averaging 23 watercraft visits per week. Interviews indicated that the majority of the public did not observe the posted signs addressing manatee harassment and were unaware of the prohibition against chasing manatees, the most frequently observed form of harassment at the park.
The methods used complemented each other to elucidate tourism activity and has the potential to inform outreach efforts and mitigation strategies.
... Warm water refuges for Florida manatees include natural springs, warm-water discharge sites from power plants, and passive thermal basins (PTB) [10,11]. The majority of manatees seek shelter in power plant effluents or artesian springs where water temperatures consistently remain between 20-22˚C [12]. ...
... Passive thermal basins are waters where cooling processes are slow and temporarily retain pockets of relatively warm water [13]. PTB are dynamic in their ability to retain warm water temperatures due to changes in the environment (i.e., solar radiation, convection, groundwater seeps, weather conditions) [11,14]. In turn, these sites can provide thermal shelter for manatees during short or extended periods of cold weather [14,15]. ...
... For example, Ten Thousand Islands is a critical PTB which was thought to be effective in preventing mass mortality from cold stress for manatees in southwestern Florida during the severe winter of 2009-2010 [12]. Additionally, several other habitats inhabited by manatees like canals, stormwater drainage ditches, dredged basins, sewage outfalls, and creeks are slightly warmer than surrounding waters and may serve similar functions to PTB [10,11]. ...
To survive cold winters, Florida manatees (Trichechus manatus latirostris) depend on artificial (i.e., power plants) and natural warm water sources such as springs and passive thermal basins. Passive thermal basins can provide critical habitat for manatees for short or extended periods of time. The Henry D. King Powerplant in Fort Pierce, Florida discharged warm water into Moore’s Creek until it went offline in 1995. However, it is unknown to what degree manatees continue to occupy this area and how environmental factors influence their occurrence in the creek. To explore this, we examined the habitat use of Florida manatees in Moore’s Creek after the shutdown from November 1997 to March 2020 from daily counts of manatees. In addition, we correlated local environmental data (ambient air, temperature, salinity) to assess if Moore’s Creek had properties indicative of a passive thermal basin. Results indicated there was not an increase or decrease in habitat use over twenty years in the Creek. The consistent use of Moore’s Creek over the study period suggests that this habitat possesses thermal and freshwater resources to support manatee occurrence long-term. These findings provide robust support for the importance of this habitat and passive thermal basins for Florida manatees.
... One example of this is the Limon River, which provide an important input of freshwater to the system. Manatees are mainly found in warm water areas (> 20 °C, Bossart et al., 2003), due to their incapacity to withstand low temperatures (Laist et al., 2013). Therefore, the temperature values of the study area fell within the range of ideal water temperature for the species. ...
In Venezuela, Antillean manatees (Trichechus manatus manatus) have declined mainly due to habitat loss and degradation, but other
threats to the species persist. The objective of this work was to investigate the manatee distribution and conservation issues in
Maracaibo Lake, Venezuela. Aiming to collect evidence on manatee presence, we conducted 404.14 hours of boat-based surveys and
observations from the shore during 2003, 2004, 2009, and 2010. Environmental parameters were collected in areas where manatees
were observed including pH, temperature, dissolved oxygen, salinity, transparency, and depth. Also, we recorded plants or algae
that could serve as potential food for manatees. We developed 96 informal and opportunistic talks with local fishermen, to gather
information about manatee occurrence, boat traffic, and people’s perception of the species. Finally, we reviewed published and
unpublished documents containing information on manatees in Maracaibo Lake. The resulting database contains information on 39
sightings and 13 reports of dead manatees. The known causes of death were poaching, vandalism, boat collision, and entanglement
in fishing nets. The Maracaibo Lake offers many suitable habitats for manatees, but also faces a wide array of conservation problems
that represent critical threats to this endangered subspecies. Long-term monitoring of this population and potential sources of
mortality is highly needed.
... For management purposes, such thermal microrefugia are categorized as primary sites, which are well-established to have high manatee use and water temperatures consistently > 20°C, or secondary sites, which have low or unpredictable manatee use and inconsistent water temperatures, especially during severe cold events (Valade et al., 2020). Types of thermal microrefugia typically used by manatees in peninsular Florida include warm water discharges created by industrial facilities, primarily power plants, or natural springs and passive thermal basins that retain heat without a constant inflow of warm water (Laist and Reynolds, 2005a, b;Laist et al., 2013;Valade et al., 2020). During warmer months, manatees disperse from winter refuge sites to access food and other resources throughout their range (Deutsch et al., 2003;Cummings et al., 2014;Hieb et al., 2017;Cloyed et al., 2021). ...
... Sighting seasons are represented as single years based on first sighting dates; however, in some seasons, last sightings occurred during Jan or Feb of the following year. use warm water discharges from power plants or natural springs as primary refugia (Laist and Reynolds, 2005a;Laist and Reynolds, 2005b;Laist et al., 2013;Valade et al., 2020). In Alabama, a power plant and two natural springs were identified as warm water anomalies, with manatee use documented at the spring sites but not the power plant outfall, during the study period. ...
... Potential passive thermal basins identified in Alabama included multiple freshwater inflow or run-off sites and dredged channels. Two of these freshwater inflow sites observed in Alabama were documented as cool water microhabitats during summer surveys but may conversely be warmer than surrounding waters during colder months as is the case for some thermal microrefugia in Florida that maintain constant temperature year-round (Laist et al., 2013). In peninsular Florida, passive thermal basins with the highest manatee use are dredged canals where lighter, freshwater flows over heavier, saline water, creating a strong vertical halocline that effectively traps warm water on the bottom (Stith et al., 2011;Stith et al., 2012). ...
Changing climate conditions are well documented to affect species distribution patterns and migratory phenology, especially for thermally constrained species. Climate induced changes and other natural and anthropogenic factors may affect habitats heterogeneously, altering microhabitats that act as refugia. Here, we used a thermally constrained marine mammal, the West Indian manatee (Trichechus manatus), as a model species to examine how the availability of thermal microrefugia combined with climate driven increases in regional water temperatures may affect the timing and duration of occurrence at the northern margins of the species’ range. We used aerial, thermographic imaging to identify potential thermal anomalies that could act as thermal microrefugia for manatees during unfavorable cold temperatures and assessed manatee occurrence at these sites using citizen-sourced manatee sightings and stranding response data. To further understand how regional and longer-term water temperatures may affect the use of thermal microrefugia and phenology of migration, we compared spatial and temporal distributions of manatee sightings to air and sea surface temperatures on a decadal scale. Thermal anomalies were detected at various sources, and documented manatee sightings at or near these sites support use as thermal microrefugia during cold periods. Cold season manatee sightings at a known western migratory endpoint (Alabama waters) have increased during the last decade, primarily through increased sightings during the late fall and early winter (Nov–Jan) that correspond to increased regional temperatures during the same period. Manatees may use thermal microrefugia to remain at northern latitudes longer, delaying seasonal migrations or overwintering as conditions allow. Climate change is likely to have further effects on the species’ distribution and migration patterns, potentially facilitating modern range expansion that has implications for management and recovery actions for manatees across their range. Our study provides novel insight for manatees but may also be used as a model to understand how other thermally constrained species may expand their ranges into higher latitudes.
... For example, the Florida manatee Trichechus manatus latirostris is an herbivorous aquatic mammal of conservation concern that thermoregulates by using thermal refuges. Due to their herbivorous diet and low metabolic rate, manatees become coldstressed at water temperatures below 20°C and seek thermal refuges in the form of inland natural springs, warm-water outflows from power plants, or passive thermal basins (Laist et al. 2013). Often, habitats used for thermal refuge lack adequate forage resources (Rettie & Messier 2000), resulting in clear, directed movements between thermal and forage habitats when transitioning between thermoregulatory and foraging behaviors (Terrien et al. 2011, Mabille et al. 2012. ...
Thermal refuges are habitats used by species for behavioral thermoregulation. These habitats can be highly dynamic and are often influenced by fluctuations in local climate. When protected species require thermal refuges, it is necessary to identify stable and high-quality areas by evaluating species use in response to variation in thermal refuge quality. Here, we assessed behavioral thermoregulation in the Florida manatee Trichechus manatus latirostris , a cold-intolerant marine mammal. Using metrics from ectotherm physiology, we evaluated thermal quality of 2 refuge types (passive thermal basins, natural springs) in 2 areas of their distribution. Thermal refuge quality was assessed with respect to the lower critical threshold of the manatee (20°C) and the surrounding ambient temperatures and compared between refuge types. We used GPS locations of manatees to quantify visits to refuges and calculated total visit duration in each refuge by individual manatees. At natural springs, we found a negative correlation between visit duration and ambient temperature during cold weather; visit duration also increased with the temperature differential between the spring and the lower critical thermal threshold. Visit duration at passive thermal basins was negatively correlated with the thermal differential between the refuge and the lower critical thermal threshold. The relationship between thermal refuge quality and time-use metrics sheds light on the potential implications of habitat degradation on animal energetics and behavior. Given these results, focusing on potential key refuges in each system may inform targeted management and habitat restoration efforts to maintain adequate thermal refuge environments for this listed species.
... For many tropical species in the southeastern United States, thermal refugia play a critical role to enable organisms to survive extreme cold winter temperatures (Osland et al. 2021). For example, coastal fishes (Stevens et al. 2018), sea turtles (Lamont et al. 2018), amphibians (Meshaka 1996, reptiles (Mazzotti et al. 2016), and manatees (Laist et al. 2013) seek thermal refugia to survive extreme cold events. Similarly, thermal refugia can reduce damage and mortality to mangroves during extreme freeze events (Ross et al. 2009;Osland et al. 2019b), which means that near northern range limits, mangroves are more abundant and taller near microclimates that provide a thermal buffer during extreme freeze events (Osland et al. 2020b). ...
Warming winters due to climate change can facilitate the range expansion of invasive non-native species. In the southeastern United States, the frequency and intensity of extreme winter temperatures determines the northern range limits of many tropical organisms including many species of invasive non-native plants. However, the effects of winter climate change on invasive species’ range limits have been understudied. Here, we used temperature and species occurrence data to examine the sensitivity of invasive tropical plant species to freezing temperatures. We also examined the potential for northward range expansion of these species due to winter climate change. From an initial group of 81 invasive plant species selected due to their ability to transform native plant communities, our analyses identify and quantify species-specific temperature thresholds for 40 tropical, cold sensitive species. Future winter warming scenarios indicate that these tropical invasive plant species have the potential for northward range expansion across the southeastern United States in response to small changes in the severity of winter cold temperature extremes. The potential for range expansion is greatest in coastal areas, which typically have warmer temperatures than inland counterparts. Thus, coastal regions are likely to serve as biological invasion hotspots from which invasive species expand into inland areas. The state of Florida has become a global hotspot for biological invasions, with tens of millions of dollars (US) spent annually to control the ecological and societal impacts of invasive plants on publicly held conservation lands. Collectively, our results underscore the need to better anticipate and prepare for the northward range expansion of invasive plants from Florida into the southeastern United States in response to winter climate change.
... The seasonal difference between autumn and spring likely results from the timing of seasonal migration relative to temperature. Our data suggest manatees departed gradually as temperature declined, remaining in the area during autumn until air temperatures were sufficiently low to force manatees to migrate to seek warm water refuge sites (Laist & Reynolds 2005, Laist et al. 2013. Human behavior may have biased these results if people were outside more on warm days, but these patterns are supported by both sighting and tagged data, suggesting that any bias is minimal. ...
Habitat selection and abundances at range margins during geographic expansion may influence movement into new areas, shaping the trajectory of climate-driven changes in species distribution. The West Indian manatee is an ideal species to study how habitat selection influences range expansion because its presence has rapidly increased during the past 2 decades in the northern Gulf of Mexico (nGoM), a region outside its historical range. We estimated the habitat selection and abundances of manatees in coastal Alabama waters along the nGoM coast using resource selection functions and N-mixture models, respectively. Warm season (May-Nov) manatee abundances were estimated at 25 and 34 manatees at any given time in coastal Alabama waters in 2010 and 2019, respectively. Manatees primarily used the Mobile-Tensaw River Delta and Dog River areas, selecting nearshore shallow water habitats proximate to submerged aquatic vegetation. Distance to boat ramps and human population density had stronger effects on opportunistic sighting data but remained important for tagged data, indicating that manatee habitat selection overlapped with humans. Temperature strongly predicted manatee sightings; most sightings occurred when temperatures were >20°C. Our data indicate that the key interacting factors likely to moderate manatee range expansion, and therefore be important to management and conservation of this species, include increased sea temperature, availability of nearshore habitat with submerged aquatic vegetation, and regional manatee population dynamics. As environmental conditions at the range margins continue to become more favorable to manatees and areas within the range core decline in quality, areas at the range margins may become increasingly important.
