Species Status Assessment Report for the Woodville Karst Cave Crayfish (Procambarus orcinus) Version 1.1
Woodville Karst cave crayfish (Procambarus orcinus) observed at Gopher Hole Sink, Apalachicola National Forest (credit: Peter Maholland, U.S. Fish and Wildlife Service)
May 2017
U.S. Fish and Wildlife Service Region 4 Atlanta, GA
Woodville Karst Cave Crayfish SSA Report Page ii May 2017
This document was prepared by Peter Maholland (USFWS – Athens, GA Field Office) with assistance from Dr. Sean Blomquist (USFWS – Panama City, FL Field Office) and Patricia Kelly (USFWS – Panama City, FL Field Office).
Valuable peer reviews of a draft of this document were provided by Chester Figiel (USFWS – Warm Springs Fish Technology Center), and Paul Moler (Florida Fish & Wildlife Conservation Commission).
We appreciate the time and effort of those dedicated to learning and implementing the SSA Framework, which resulted in a more robust assessment and final report.
Suggested reference:
U.S. Fish and Wildlife Service. 2017. Species status assessment report for the Woodville Karst Cave Crayfish (Procambarus orcinus). Version 1.1. May, 2017. Atlanta, GA.
Woodville Karst Cave Crayfish SSA Report Page iii May 2017
Species Status Assessment Report For Woodville Karst Cave Crayfish (Procambarus orcinus)
Prepared by the U.S. Fish and Wildlife Service
EXECUTIVE SUMMARY
This species status assessment (SSA) reports the results of the comprehensive status review for the Woodville Karst cave crayfish (Procambarus orcinus), documenting the species’ historical condition and providing estimates of current and future condition under a range of different scenarios. The Woodville Karst cave crayfish is a hypogean species of crayfish endemic to a number of freshwater spring and sinkhole caves within the panhandle of Florida. The Woodville Karst cave crayfish has been collected from aquatic caves and limestone springs and sinks associated with the Woodville Karst Plain near and below the Cody Scarp, paralleling riverine karst areas of the Wakulla-St. Marks Rivers. The principal habitat feature supporting this species appears to be a freshwater, subterranean environment.
The SSA process can be categorized into three sequential stages. During the first stage, we used the conservation biology principles of resilience, redundancy, and representation (together, the 3Rs) to evaluate individual Woodville Karst cave crayfish life history needs. The next stage involved an assessment of the historical and current condition of species’ demographics and habitat characteristics, including an explanation of how the species arrived at its current condition. The final stage of the SSA involved making predictions about the species’ response to positive and negative environmental and anthropogenic influences. This process used the best available information to characterize viability as the ability of a species to sustain populations in the wild over time.
To evaluate the current and future viability of the Woodville Karst cave crayfish, we assessed a range of conditions to allow us to consider the species’ resiliency, representation, and redundancy. For the purposes of this assessment, populations were delineated using the eighteen springs that Woodville Karst cave crayfish has historically occupied. Limited access to aquatic cave habitat prohibits confirmation, but it is presumed that the species is actually found throughout the karst conduits of the aquifer, and that these sites are merely “windows” where Woodville Karst cave crayfish can observed.
Woodville Karst Cave Crayfish SSA Report Page iv May 2017
Resilience, assessed at the population level, describes the ability of a population to withstand stochastic disturbance events. A species needs multiple resilient populations distributed across its range to persist into the future and avoid extinction. These factors include (1) adequate fresh water availability (water quantity), (2) sufficient water quality, and (3) appropriate habitat (Figure 3.3.1). If spring and sink ecosystems provide adequate fresh water, suitable water quality, and adequate habitat, we anticipate Woodville Karst cave crayfish will survive and thrive in abundance. Each of these factors is discussed here (Table ES-1). As we consider the future viability of the species, more populations with high resiliency distributed across the known range of the species are associated with higher overall species viability.
Redundancy describes the ability of the species to withstand catastrophic disturbance events. Redundancy is about spreading the risk and can be measured through the duplication and distribution of populations across the range of the species. The greater the number of populations a species has distributed over a larger landscape, the better it can withstand catastrophic events. For the Woodville Karst cave crayfish, we considered whether the distribution of resilient populations was sufficient for minimizing the potential loss of the species from such an event.
Representation characterizes a species’ adaptive potential by assessing geographic, genetic, ecological, and niche variability. Representation can be measured through the genetic diversity within and among populations and the ecological diversity of populations across the species’ range. The more representation a species has, the more it is capable of adapting to changes in its environment. In the absence of species-specific genetic and ecological diversity information, we evaluate representation based on the extent and variability of habitat characteristics within the geographical range. The Woodville Karst cave crayfish historic range was limited to eighteen springs and sinks in Florida’s panhandle. Maintaining those populations provides redundancy, and the species is currently represented across most of the known geographic extent of the species. We have assessed the Woodville Karst cave crayfish’s levels of resiliency, redundancy, and representation currently and into the future by ranking the condition of each population, as delineated for this assessment.
Together, the 3Rs comprise the key characteristics that contribute to a species’ ability to sustain multiple distinct populations in the wild over time (i.e., viability). Using the principles of resiliency, redundancy, and representation, we characterized both the species’ current viability and forecasted its future viability over a range of plausible future scenarios. To this end, we ranked the condition of each population by assessing the relative condition of occupied sites using the best available scientific information. Rankings are a qualitative assessment of the relative condition of spring/sink ecosystems based on the knowledge and expertise of U.S. Fish
Woodville Karst Cave Crayfish SSA Report Page v May 2017 and Wildlife Service and Florida Fish and Wildlife Conservation Commission staff, and recent spring/sink condition reports.
The most significant stressor to Woodville Karst cave crayfish is the future loss of spring and sink ecosystems that individuals and populations need to complete their life history. The primary source of potential future habitat loss is groundwater depletion resulting in reduced or eliminated available fresh water in subterranean caves. Groundwater withdrawal is not anticipated to influence spring flow dramatically in the Woodville Karst Plain region due to the large areas of public ownership, changes to surface water flow and stormwater management, and sea level rise causing more freshwater to remain in the karst system instead of discharging into the Gulf of Mexico.
The viability of the Woodville Karst cave crayfish depends on maintaining multiple resilient populations over time. Given our uncertainty regarding if or when springs and sinks occupied by Woodville Karst cave crayfish will experience a reduction or elimination of available fresh water in the future, we have forecasted what the Woodville Karst cave crayfish may have in terms of resiliency, redundancy, and representation under three future plausible scenarios:
(1) All or most springs and sinks occupied by Woodville Karst cave crayfish experience no measureable drop in fresh water availability; (2) Available fresh water in springs and sinks occupied by Woodville Karst cave crayfish is reduced but not eliminated; and (3) All or most springs occupied by Woodville Karst cave crayfish experience an extreme reduction or elimination of available fresh water.
We used the best available information to forecast the likely future condition of the Woodville Karst cave crayfish. Our goal was to describe the viability of the species in a manner that will address the needs of the species in terms of the 3R’s. We considered a range of potential scenarios that may be important influences on the status of the species, and our results describe this range of possible conditions in terms how many and where Woodville Karst cave crayfish populations are likely to persist into the future (Table ES-1).
Woodville Karst Cave Crayfish SSA Report Page vi May 2017
Table ES-1. Summary results of the Woodville Karst cave crayfish Species Status Assessment. 3Rs Needs Current Condition Future Condition (Viability) Projections based on cave freshwater availability Adequate scenarios: Resiliency availability of fresh No change: All populations are likely to remain (Large water extant into the future All populations across populations able Sufficient water Fresh water is reduced: Most populations are range have high to withstand quality expected to experience some level of decline in resiliency stochastic Quality habitat resiliency events) Fresh water is extremely reduced or eliminated: All populations experience a large decline in resiliency, with some extirpated. Projections based on cave freshwater availability scenarios: No change: All populations are likely to remain Redundancy No known Compared to historical extant into the future, maintaining current (Number and ecological distribution, two genetic variation distribution of variation populations still have Fresh water is reduced: Populations populations to observations, 15 would be vulnerable to extirpation, withstand population sites potentially reducing genetic representation catastrophic assumed extant Fresh water is extremely reduced or events) eliminated: Most populations would be vulnerable to extirpation, severely limiting genetic variation
Woodville Karst Cave Crayfish SSA Report Page vii May 2017
Projections based on cave freshwater availability Representation Multiple scenarios: Compared to historical (Genetic and populations No change: All populations are likely to remain distribution, two ecological throughout the extant into the future populations have been diversity to range of the species Fresh water is reduced: Current populations observed, 15 maintain would have moderate resiliency population sites adaptive Fresh water is extremely reduced or assumed extant potential) eliminated: Populations would be vulnerable to extirpation
Woodville Karst Cave Crayfish SSA Report Page viii May 2017
Table of Contents
EXECUTIVE SUMMARY ...... iv CHAPTER 1 - INTRODUCTION ...... 1 CHAPTER 2 – INDIVIDUAL NEEDS: LIFE HISTORY AND BIOLOGY ...... 3 2.1 Taxonomy ...... 3 2.2 Morphological Description ...... 4 2.3 Life History...... 5 2.4 Habitat ...... 5 CHAPTER 3 – POPULATION AND SPECIES NEEDS AND CURRENT CONDITION ...... 7 3.1 Historical Range and Distribution ...... 7 3.2 Current Range and Distribution ...... 7 3.2.2 Land Ownership ...... 8 3.3 Needs of the Woodville Karst Cave Crayfish ...... 11 3.3.1 Species Resiliency ...... 11 3.3.2 Species Redundancy and Representation ...... 13 3.4 Current Conditions ...... 14 3.4.1 Current Resiliency ...... 15 3.4.2 Current Representation ...... 16 3.4.3 Current Redundancy ...... 17 3.5 Summary of Needs ...... 17 CHAPTER 4 – FACTORS INFLUENCING VIABILITY ...... 21 4.1 Habitat Loss, Destruction, or Modification ...... 22 4.2 Regulatory Mechanisms ...... 24 4.2.1 Land and Water Development Permitting ...... 24 4.2.2 State Listing Status ...... 25 4.2.3 Protection of Springs and Aquifers ...... 25 4.3 Climate Change ...... 25 4.3.1 Sea Level Rise and Seawater Intrusion ...... 26 4.4 Overutilization ...... 28 4.5 Disease and Predation ...... 29 4.6 Summary ...... 29
Woodville Karst Cave Crayfish SSA Report Page ix May 2017
CHAPTER 5 – SPECIES VIABILITY...... 30 5.1 Introduction ...... 30 5.2 Resiliency ...... 31 5.3 Redundancy ...... 34 5.4 Representation ...... 37 5.5 Status Assessment Summary ...... 38 LITERATURE CITED ...... 40
Woodville Karst Cave Crayfish SSA Report Page x May 2017
CHAPTER 1 - INTRODUCTION
The Woodville Karst cave crayfish (Procamburus orcinus) is a troglobitic crayfish with a white or colorless body and unfaceted eyes (Hobbs et al. 1977, p. 126) that is known from 18 aquatic cave sites in northern Florida. It is believed to be closely related to another cave-dwelling species, the Big Blue Spring cave crayfish (P. horsti), that is also associated with St. Marks Formation limestone (Franz and Lee 1982, p. 67). The species was petitioned for federal listing under the Endangered Species Act of 1973, as amended (Act), as a part of the 2010 Petition to List 404 Aquatic, Riparian and Wetland Species from the Southeastern United States by the Center for Biological Diversity (CBD 2010).
The Species Status Assessment (SSA) framework (USFWS 2016) is intended to be an in-depth review of the species’ biology and threats, an evaluation of its biological status, and an assessment of the resources and conditions needed to maintain long-term viability. The intent is for the SSA Report to be easily updated as new information becomes available and to support all functions of the Endangered Species Program from Candidate Assessment, Listing, Consultations and Recovery. As such, the SSA Report will be a living document that may be used to inform Act decision making, such as listing, recovery, Section 7, Section 10, and reclassification decisions (the former four decision types are only relevant should the species warrant listing under the Act).
Because the Woodville Karst cave crayfish SSA has been prepared at the Candidate Assessment phase, it is intended to provide the biological support for the decision on whether to propose to list the species as threatened or endangered and, if so, to determine whether it is prudent to designate critical habitat in certain areas. Importantly, the SSA Report is not a decisional document by the U.S. Fish and Wildlife Service (Service); rather it provides a review of available information strictly related to the biological status of the Woodville Karst cave crayfish. The listing decision will be made by the Service after reviewing this document and all relevant laws, regulations, and policies, and the results of a proposed decision will be announced in the Federal Register, with appropriate opportunities for public input.
For the purpose of this assessment, we define viability as the ability of the species to sustain resilient populations in freshwater spring and sink ecosystems for at least 50 years. We chose 50 years because it is within the range of the available hydrological and climate change model forecast (e.g., IPCC 2012, entire), and encompasses approximately 10 generations of the Woodville Karst cave crayfish. Using the SSA framework, we consider what the species needs to maintain viability by characterizing the status of the species in terms of its resiliency, redundancy, and representation (USFWS 2016; Wolf et al. 2015). Woodville Karst Cave Crayfish SSA Report Page 1 May 2017
Resiliency is assessed at the level of populations and reflects a species’ ability to withstand stochastic events (events arising from random factors). Demographic measures that reflect population health, such as fecundity, survival, and population size, are the metrics used to evaluate resiliency. Resilient populations are better able to withstand disturbances such as random fluctuations in birth rates (demographic stochasticity), variations in rainfall (environmental stochasticity), and the effects of anthropogenic activities.
Redundancy is also assessed at the level of the species and reflects a species’ ability to withstand catastrophic events (such as a rare destructive natural event or episode involving many populations). Redundancy is about spreading the risk of such an event across multiple, resilient populations. As such, redundancy can be measured by the number and distribution of resilient populations across the range of the species.
Representation is assessed at the species’ level and characterizes the ability of a species to adapt to changing environmental conditions. Metrics that speak to a species’ adaptive potential, such as genetic and ecological variability, can be used to assess representation. Representation is directly correlated to a species’ ability to adapt to changes (natural or human-caused) in its environment.
To evaluate the current and future viability of the Woodville Karst cave crayfish, we assessed a range of conditions to characterize the species’ resiliency, redundancy, and representation (together, the 3Rs). This SSA Report provides a thorough account of known biology and natural history and assesses the risk of threats and limiting factors affecting the future viability of the species.
This SSA Report includes: (1) a description of Woodville Karst cave crayfish resource needs at both individual and population levels (Chapter 2); (2) a characterization of the historic and current distribution of populations across the species’ range (Chapter 3); (3) an assessment of the factors that contributed to the current and future status of the species and the degree to which various factors influenced viability (Chapter 4); and (4) a synopsis of the factors characterized in earlier chapters as a means of examining the future biological status of the species (Chapter 5). This document is a compilation of the best available scientific information (and associated uncertainties regarding that information) used to assess the viability of the Woodville Karst cave crayfish.
Woodville Karst Cave Crayfish SSA Report Page 2 May 2017
CHAPTER 2 – INDIVIDUAL NEEDS: LIFE HISTORY AND BIOLOGY
In this section, we provide basic biological information about the Woodville Karst cave crayfish, including its physical environment, taxonomic history and relationships, morphological description, and other life history traits. We then outline the resource needs of individuals and populations. Here we report those aspects of the life histories that are important to our analyses. For further information about the Woodville Karst cave crayfish, refer to Hobbs and Means (1972).
2.1 Taxonomy
With 170 described species and 16 taxa listed as subspecies, the genus Procambarus contains the largest number of species of any genus of freshwater crayfish worldwide. The genus is currently divided into 15 different subgenera that include: Acucada, Austrocambarus, Capillicambarus, Girardiella, Hagenides, Leconticambarus, Lonnbergius, Mexicambarus, Ortmannicus, Paracambarus, Pennides, Procambarus, Scapulicambarus, Tennicambarus, and Villalobosus. The distinguishing feature of the genus Procambarus is the presence of four terminal elements of the male gonopod. Representatives of the genus are found throughout much of the eastern portion of North America, ranging along the eastern seaboard and the coastal regions of the Gulf of Mexico, up the Mississippi River drainage as far as southern Wisconsin, and south through Texas and Mexico to Honduras (Longshaw and Stebbing 2016, p. 206).
The Woodville Karst cave crayfish (assigned to the subgenus Ortmannicus) was first described from specimens collected from Woodville Karst in Leon and Wakulla counties in Florida (Hobbs and Means 1972). The species is considered to be valid (e.g., Taylor et al. 1996, 2007) and meets the Endangered Species Act definition of a species.
The currently accepted classification is (Integrated Taxonomic Information System 2016): Phylum: Arthropoda Class: Crustacea Order: Decapoda Family: Cambaridae Genus: Procambarus Species: Procambarus orcinus
Woodville Karst Cave Crayfish SSA Report Page 3 May 2017
2.2 Morphological Description
Information regarding the Woodville Karst cave crayfish is limited. The species was first described by Hobbs and Means (1972). The carapace in adults is approximately 25 millimeters (mm) (1.0 inches [in]) in length and the postorbital carapace is approximately 19 mm (0.75 in) in length (Hobbs et al. 1977). This crayfish is white or colorless, often with semitransparent cuticle revealing pinkish orange subcuticular tissue, reduced unfaceted eyes but with small red pigment spot, and a rostrum with converging margins ending in small spines (Figure 2.2.1).
Figure 2.2.1. Procambarus orcinus. Hobbs and Means (1972): a. Lateral view of carapace of holotype; b. Epistome of paratypic male, form I; c. Mesial view of first pleopod of holotype; d. Mesial view of first pleopod of morphotype; e. Annulus ventralis of allotype; f. Lateral view of first pleopod of morphotype; g. Lateral view of first pleopod of holotype; h. Dorsal view of carapace of holotype; i. Antennal scale of holotype; j. Caudal view of first pleopods of holotype; k. Basal podomeres of third, fourth and fifth pereiopods of holotype; l. Dorsal view of distal podomeres of cheliped of holotype.
Woodville Karst Cave Crayfish SSA Report Page 4 May 2017
2.3 Life History
The life history of crayfishes, particularly in the family Cambaridae, is influenced by a continuous series of molts (Taylor et al. 1996, p. 27). Males alternate between reproductively mature forms (form I) and nonreproductive forms (form II). Generally in the southern United States, crayfish mate in the spring and eggs are extruded during the fall and then carried under the female's abdomen for several days to weeks before hatching. Subterranean species may live several decades (Taylor et al. 1996, p. 27). Though little is known for specific species, the average estimate life span for cave crayfish in general is approximately 20 years, based on a five- year mark-recapture study of 3,800 crayfish species inhabiting 3 cave systems (Longshaw and Stebbing 2016, p. 68). Since very little specific information is known regarding its life history, a conceptualized life cycle diagram for Woodville Karst cave crayfish is provided in Figure 2.3.1.
Procamburus orcinus has been observed in shallow water at the mouth of sink holes, to as deep as 91 m (300 feet) (Franz et al. 1994, Moler 2016). It is postulated that Big Blue Spring cave crayfish developed more efficient metabolisms relative to surface-dwelling crayfish species to adapt to life in subterranean aquatic habitats, where detritus inputs are low (Franz and Lee 1982, pp. 74-75). As part of a physiological and behavioral study, Caine (1978, p. 323) noted P. orcinus is found in more extensive cave systems with much greater predator pressure, particularly from American eel (Anguilla rostrata). As a result, the Woodville Karst cave crayfish exhibits significantly less aggressive behavior than the similar P. horsti, which is found in higher energy springs (Hobbs and Means 1972, p. 401; Caine 1978, pp. 323, 325). Where P. orcinus are found, consumption of troglobitic isopods and predation of other crayfish may occur, as was observed in field containers (Hobbs and Means 1972, p. 406).
2.4 Habitat
The Woodville Karst cave crayfish has been collected from aquatic caves and limestone springs and sinks associated with the Woodville Karst Plain near and below the Cody Scarp, within the lower-energy and interconnected Wakulla Springs system. The principal habitat feature supporting this species appears to be a flowing, fresh water, subterranean environment (Caine 1974, p. 490). Water quality requirements for the species are currently unknown.
Woodville Karst Cave Crayfish SSA Report Page 5 May 2017
Figure 2.3.1. Conceptualized life history diagram for cave crayfish, based on limited information from other crayfish species (e.g., Jegla 1966).
Woodville Karst Cave Crayfish SSA Report Page 6 May 2017
CHAPTER 3 – POPULATION AND SPECIES NEEDS AND CURRENT CONDITION
In this chapter we consider the Woodville Karst cave crayfish historical distribution, its current distribution, and the factors that contributed to the species’ current condition. We first review the historical information on the range and distribution of the species. Next, we evaluate species’ requisites to consider their relative influence to Woodville Karst cave crayfish resiliency, redundancy, and representation. Through the lens of the 3Rs, we then estimate the current condition of Woodville Karst cave crayfish populations.
3.1 Historical Range and Distribution
Woodville Karst cave crayfish was originally known from only four localities in Leon and Wakulla counties, Florida: Gopher Sink, Osgood Sink, and Culley's Cave, Leon County; and Wakulla Springs, Wakulla County (Hobbs and Means 1972, p. 39). The springs and sinks are located within the extensive Woodville Karst Plain, which is bounded to the north by the Cody Scarp, to the west roughly by the western edge of the Apalachicola National Forest, and to the south by the Gulf of Mexico. The Woodville Karst Plain is characterized by underground drainage systems with sinkholes and caves formed by unconsolidated and porous Pleistocene sands overlying Eocene, Oligocene, and Miocene limestone (Xu et al. 2016, p. 2). Franz and Lee (1982, p. 67) hypothesized that erosion of the region by the Wacissa River has resulted in differentiation of two closely related species, P. orcinus and P. horsti. This suggests that their common ancestor may have been widespread throughout the Wakulla River karst cave system historically.
3.2 Current Range and Distribution
The Woodville Karst cave crayfish is currently known from 18 aquatic cave sites (Figure 3.2.1, Table 3.4.1), all of which are within an area of approximately 100 square miles: Bird Sink, Culley’s Cave, Falcon’s Nest, Gopher Hole Sink, Gopher Sink, Little Dismal Sink, Osgood Sink, Sullivan’s Tunnel, and Trog Sink in Leon County; and Clay Sink, Emerald Sink, Indian Springs, McBride Spring, Sally Ward Spring, River Sinks, Wakulla Spring, an unnamed cave 3 miles south of Woodville, Florida, and an unnamed sinkhole southeast of the junction State Route 61 and County Line Road in Wakulla County. For the purposes of this assessment, populations were delineated using the three sites that Big Blue Springs cave crayfish has historically occupied. Limited access to aquatic cave habitat prohibits confirmation, but it is presumed that the species is actually found throughout the karst conduits of the aquifer, and that these sites are merely “windows” where Woodville Karst cave crayfish can observed. Woodville Karst Cave Crayfish SSA Report Page 7 May 2017
Current population or demographic data are limited for the Woodville Karst cave crayfish throughout its range. Given the low levels of energy inputs into the aquatic cave systems this species inhabits (Franz and Lee 1982, p. 69), it is likely that populations are typically low (Hobbs and Franz 1986, p. 518).
On December 21, 2016, two sinks were visited with historic observations of Woodville Karst cave crayfish. These sites included Gopher Hole Sink (Figure 3.2.2) and Trog Sink. Approximately 14 Woodville Karst cave crayfish individuals were observed at the entrance of Gopher Hole Sink, and 11 individuals were observed within Trog Sink. Individuals were counted that were visible from the edge of each sink, but the sinks were not surveyed extensively (i.e., habitat was not disturbed and no underwater surveys were conducted).
3.2.2 Land Ownership
Springs and sinks that provide habitat for Woodville Karst cave crayfish are primarily located on public lands. Public ownerships where springs and sinks are inhabited by Woodville Karst cave crayfish include: Apalachicola National Forest (ANF), Wakulla State Forest, and Edward Ball Wakulla Springs State Park. Public lands provide protection and improvement for springs and sinks, as described in management plans for these areas. Included in the stated goals and objectives for Edward Ball Wakulla Springs State Park are to protect, restore and maintain water quality conditions, and acquisitions for the park have focused on protecting the Wakulla spring system by acquiring land above the underground conduits that feed them (FDEP 2007, pp. 4 and 7). Wakulla State Forest was acquired with the specific purpose to preserve the quality of ground water leading to Wakulla Springs (DOF, p. 8). Management on the ANF is guided by the Land and Resource Management Plan, which includes the objective to locate and perpetuate seepage bogs, spring runs, sinkhole edges (FNF 1999, p. 3-18).
Woodville Karst Cave Crayfish SSA Report Page 8 May 2017
Figure 3.2.1. Distribution of Woodville Karst cave crayfish, with mapped portion of the karst conduit system (orange).
Woodville Karst Cave Crayfish SSA Report Page 9 May 2017
Figure 3.2.2. Entrance to Gopher Hole Sink, Apalachicola National Forest. Fourteen Woodville Karst cave crayfish were observed near areas of high nutrient input during the December 2016 site visit (credit: Peter Maholland, U. S. Fish and Wildlife Service).
Woodville Karst Cave Crayfish SSA Report Page 10 May 2017
3.3 Needs of the Woodville Karst Cave Crayfish
As discussed in Chapter 1, for the purpose of this assessment, we define viability as the ability of the species to sustain populations in the wild over time (in this case, 50 years). Using the SSA framework, we describe the species’ viability by characterizing the status of the species in terms of its resiliency, redundancy, and representation (the 3Rs). Resiliency is measured at the population level, representation is measured at the species and, and possibly, population level, and redundancy is measured at the species level (USFWS 2016). Using various time frames and the current and future characterization of the 3Rs, we thereby describe the species’ level of viability over time.
3.3.1 Species Resiliency
Resiliency (measured at the population level) is the foundational building block of the SSA Framework; thus, for the Woodville Karst cave crayfish to be viable, some proportion of its range must be resilient enough to withstand stochastic events. Stochastic events that have the potential to affect cave crayfish populations include extreme weather events, spring and sink habitat modification, shifts in water quality, and changes in available fresh water. Resilient Woodville Karst cave crayfish populations occupy habitats of sufficient size to sustain reproducing populations. We have limited information regarding population demographics; however, early observations by Hobbs and Means (1972) and subsequent surveys suggest that Woodville Karst cave crayfish can be locally numerous.
Population Factors that Influence Resiliency
Freshwater springs and sinks provide protection from desiccation, predation, and temperature extremes. A number of factors influence whether cave crayfish populations will grow to maximize habitat occupancy, which increases the resiliency of a population to stochastic events. These factors include (1) adequate fresh water availability (water quantity), (2) sufficient water quality, and (3) appropriate habitat (Figure 3.3.1). If spring and sink ecosystems provide adequate fresh water, suitable water quality, and adequate habitat, we anticipate Woodville Karst cave crayfish will survive and thrive in abundance. Each of these factors is discussed here.
Adequate Fresh Water Availability (Water Quantity)
Springs and sinks inhabited by Woodville Karst cave crayfish are sustained by groundwater discharged from a regional aquifer (and to a lesser degree, precipitation), and this groundwater must occur in perpetuity for the springs and sinkholes to persist. If groundwater levels in sinks or Woodville Karst Cave Crayfish SSA Report Page 11 May 2017 springs are curtailed or eliminated, Woodville Karst cave crayfish populations could lose resiliency or be extirpated.
Sufficient Water Quality
Water quality must be sufficient to sustain cave crayfish populations. Degradation of spring and sink water quality from increased nutrient inputs and contaminants from stormwater runoff can result in biochemical changes that negatively impact aquatic cave dwelling species (Walsh 2001, pp. 83-84). Declines in water quality have been documented in most Florida springs since the 1970s, particularly due to increases in nutrient loading (FDEP 2006, p. 6).
We considered water quality to be functioning at a high level if water conditions appear to provide appropriate conditions for cave crayfish occupation; at a moderate level if water conditions appear to provide marginal conditions for cave crayfish occupation; and at a low level if water conditions appear unable to support cave crayfish occupation. Because there is very little information known about water quality parameters necessary to fully protect cave crayfish, it is difficult to determine what water quality conditions are appropriate for the species. Therefore, we define appropriate water quality as not exhibiting excessive nutrient, bacteriological, metals, or other contaminants.
Appropriate Habitat Quality
Deyrup and Franz (1994) state that similar to other troglobitic species, Woodville Karst cave crayfish are dependent on organic detritus from the surface for food. Hobbs and Franz (1986, p. 518) suggest input levels are generally low for springs and sinks associated with Woodville Karst cave crayfish. Land management activities, such as development or logging, may result in the removal of vegetation that provides detrital inputs to springs and sinks.
We considered habitat quality to be sufficient (high) if vegetation providing detritus directly to the system via sinks is present, land management practices maintain vegetation, and karst windows (sinks and springs) are strongly connected via aquatic conduits; moderate if there is limited vegetation, land management practices maintain minimal vegetation, and aquatic connectivity through the aquifer conduits between karst windows is adequate; and low if vegetation is not present, land management practices do not maintain vegetation, and aquatic connectivity through the aquifer conduits between karst windows is diminished.
Woodville Karst Cave Crayfish SSA Report Page 12 May 2017
Figure 3.3.1. Factors influencing the current conditions of Woodville Karst cave crayfish populations.
3.3.2 Species Redundancy and Representation
Redundancy reduces the risk that a large portion of the species’ range will be negatively affected by a natural or anthropogenic catastrophic event at a given point in time. Species that have resilient populations spread throughout their historical range are less susceptible to extinction (Carroll et al. 2010, entire; Redford et al. 2011, entire).
Widespread groundwater depletion that diminishes or eliminates the supply of water to the spring/sink ecosystems supporting the species would have large effects on redundancy and representation. The presence of several springs and sinks serves as an indicator that sufficient groundwater is available throughout the karst conduit system to buffer the species from impacts from catastrophic events by providing the redundancy required by the species to withstand localized loss of habitat.
Woodville Karst Cave Crayfish SSA Report Page 13 May 2017
Information on the genetic diversity among populations of Woodville Karst cave crayfish is extremely limited. Recent genetic testing included testing of only two individual P. orcinus from one locality, which indicated the species is part of the Pallidus group, along with the Pallid cave crayfish (P. pallidus) and P. horsti (Moler 2016). Further genetic testing is needed to corroborate the morphological evidence distinguishing the Woodville Karst cave crayfish as a separate species from P. pallidus and/or P. horsti.
Exchange of genetic material between populations of Woodville Karst cave crayfish that do not share underground aquatic connection is probably a rare event. However, given the highly interconnected nature of the Wakulla karst system, it is likely that genetic material is shared between many of the Woodville Karst cave crayfish populations, and there is no reason to believe that any populations are isolated. Given that the springs and sinks where the species has been observed represent small windows into the overall network of karst conduit habitat throughout which Woodville Karst cave crayfish is found, it is appropriate to consider the occupied system as one large population with regards to representation. “Populations” at sinks and springs, therefore, merely provide a means by which we can evaluate species representation. The collection and analysis of additional genetic material across the species’ range will help to better define its genetic population structure in the future.
Since our knowledge of the level of genetic diversity is limited, and presence of populations in other springs and sinkholes that have not been surveyed is unknown, it is possible other populations exhibit some natural variation in genetic diversity. As such, maintaining representation in the form of genetic or ecological diversity may be important to the capacity of the Woodville Karst cave crayfish to adapt to future environmental change. To measure representation and redundancy, we looked at the number and distribution of Woodville Karst cave crayfish populations, as represented by observable karst windows, now and in the future (see Chapter 5, Viability for more information).
3.4 Current Conditions
The available literature indicates that the Woodville Karst cave crayfish is currently present in 18 known population sites (Table 3.4.1); however, no systematic surveys have been completed to confirm the continued presence of the species at each site. During the December 2016 site visits, individuals were observed at two sites where they had previously been observed. The sites visited included Gopher Hole Sink and Trog Sink. The remaining known occurrence sites were not visited and therefore presence or absence of the species at those sites is unknown, but presence is assumed, based on historic data.
Woodville Karst Cave Crayfish SSA Report Page 14 May 2017
Table 3.4.1. Observed population sites for Woodville Karst cave crayfish. Site Last Observation Source Bird Sink 1993 Smithsonian, USNM 260308, 260311-12 1971 Smithsonian, USNM 132039-40; Leon Sinks Culley’s cave Geological Area Falcons Nest 1993 Smithsonian, USNM 260315 Gopher Sink 1971 Smithsonian, USNM 131462, 131281, 132031-38, Gopher Hole Sink 2016 Paul Moler, December 2016 site visit. Little Dismal Sink 1982 Smithsonian, USNM 219479 1994 Species reported as present in Franz et al. (1994), Osgood Sink but no specific data available. Sullivan’s Tunnel 1982 Smithsonian, USNM 219445 Trog Sink 2016 Paul Moler, December 2016 site visit. Cave 3 mi S of Woodville 1962 Smithsonian, USNM 133337 1965 Smithsonian, USNM 116108;Reported as Leon Co Clay Sink but likely Wakulla per Al Kraus Emerald Sink 1985 Smithsonian, USNM 219385 Indian Springs 1985 Smithsonian, USNM 219446 1994 Species reported as present in Franz et al. (1994), McBride Spring but no specific data available. 1994 Species reported as present in Franz et al. (1994), Sally Ward Spring but no specific data available. 1994 Species reported as present in Franz et al. (1994), River Sinks but no specific data available. 1994 Species reported as present in Franz et al. (1994), Wakulla Spring but no specific data available. Sinkhole SE Junction Hwy Unknown Keith Crandall, BYU 61 and County Line Road
3.4.1 Current Resiliency
Overall, the extant populations occur in areas of good habitat and water quality. Information on water quality parameters and spring discharge is generally lacking for nearly all of the springs, with the exception of Wakulla Spring. Because the springs and sinks occupied by Woodville Karst cave crayfish are highly connected via a series of karst conduits, we can infer the relative resiliency of the springs and sinks based upon the condition of Wakulla Spring.
Some degradation of the water quality of Wakulla Spring has been documented over the past 30 years, primarily due to wastewater treatment and septic system practices, although improvement has been observed in recent years, including improvements to wastewater treatment by the City of Tallahassee and land acquisitions for the protection of the watershed (Table 3.4.2). General qualitative descriptions from state investigations (e.g., FGS 2004, FDEP 2006) and field observations indicate that water quality and discharge can vary substantially with precipitation. Woodville Karst Cave Crayfish SSA Report Page 15 May 2017
All spring and sink ecosystems appear to be free-flowing and include suitable vegetation that provides detrital input (either directly or via sinkholes and other karst windows). Some areas along the Wakulla River spring runs exhibit undesirable levels of the invasive exotic plant, Hydrilla (Hydrilla verticillata). These spring runs are outside of sections of the cave system occupied by Woodville Karst cave crayfish.
Table 3.4.2. Wakulla Spring water quality analysis (modified from FGS 2004). A=Average value; U=Compound not detected, value shown is the method detection limit; J=Estimated value Analytes 1924 1946 1972 2001 Unfilter Filter Field Measures Temperature - 22.8 20.5 21.2 - DO - - 3.2 2.39 - pH - 7.9 7.3 7.2 - Lab Analytes BOD - - 0.4 0.2AU AU Alkalinity - - 130 146 148 TDS - - - 183 - TSS - - - 4U - Cl 8 5.1 3.4 7.8 7.8 SO4 11 9.3 17 9.4 9.5 Nutrients TOC - - 0 1U - NO3 + NO2 - - 0.25 0.99J 0.96 NH3 + NH4 - - - 0.01U 0.01U TKN - - - 0.06U 0.06U P - - 0.04 0.032 0.03A PO4 - - 0.03 0.03 - Metals Ca 39 38 39 44.5A 45.1 K - 0.5 0.3 0.58A 0.61 Na 5.7 4 3.7 4.99A 5.01 Mg 9.6 9.5 8.7 10.4A 10.6
3.4.2 Current Representation
We consider the Woodville Karst cave crayfish to have representation in the form of genetic diversity in at least two sinks (Gopher Hole Sink and Trog Sink), and there is likely representation in the other 16 previously documented springs and sinks, particularly given the Woodville Karst Cave Crayfish SSA Report Page 16 May 2017 high level of karst conduit connectivity within in the Wakulla River hydrogeologic system. Although very little genetic information has been collected for this species, a comparative study by Buhay and Crandall (2005) of genetic diversity in two surface-dwelling crayfish and three cave dwelling species (including 2 subspecies) ranging from eastern Kentucky south to northern Alabama suggests genetic diversity in cave crayfish may be high. The study reported that estimates of genetic diversity were moderate to high and geographic range is not reflective of genetic diversity for the cave-dwelling crayfish species. They hypothesize that the stable underground environment may provide enough suitable habitat pockets and refugia to buffer the subterranean species from impacts experienced by surface-dwelling crayfish (Buhay and Crandall 2005, pp. 4263-4264, 4271). As discussed in Section 3.3.2, it is likely the species is represented throughout the karst conduit network and acts as a single population.
3.4.3 Current Redundancy
Observational surveys completed in 2016 of two sinks with previous known observations of Woodville Karst cave crayfish indicated they are currently occupied (Table 3.4.2).
Table 3.4.3. Current population estimates by sink location from December 2016 presence/absence survey. Sink Location Survey Date Individuals Observed Gopher Hole Sink December 21, 2016 14 Trog Sink December 21, 2016 11
Many of these sites are located on public lands that are currently relatively intact and protected, and contribute to redundancy by providing suitable habitat for populations throughout the range of the species.
3.5 Summary of Needs
The most important needs of Woodville Karst cave crayfish individuals and populations are listed below and summarized in Table 3.5.1.
Individuals permanent subterranean fresh water unpolluted water detrital inputs
Woodville Karst Cave Crayfish SSA Report Page 17 May 2017
Populations stable or positive trends in relative abundance intact spring-sink ecosystems sufficient abundance Rangewide sufficient groundwater to support adequate water levels within the system
Table 3.5.1 shows current conditions of Woodville Karst cave crayfish localities. Rankings are a qualitative assessment of the relative condition of spring/sink ecosystems based on the knowledge and expertise of Service and Florida Fish and Wildlife Conservation Commission staff, and recent spring condition reports (see Table 3.5.2 for more information).
High: spring/sink ecosystem is functioning near an optimum level for this resource need and there is little room for improvement. Moderate: spring/sink ecosystem is functioning somewhat well for this resource need and there is room for improvement. Low: spring/sink ecosystem is functioning at a well below optimal level for this resource need and there is significant room for improvement.
Overall condition was determined based on an average of the other factors. The factor “Adequate fresh water availability” was given twice as much weight as the other factors due to its level of importance.
Woodville Karst Cave Crayfish SSA Report Page 18 May 2017
Table 3.5.1. Current conditions of Woodville Karst cave crayfish populations.
Spring/Sink Population Adequate Sufficient Suitable Current Fresh Water Water Quality Detrital Overall Availability Input Condition Bird Sink High High High High Culley’s Cave High High High High Falcon’s Nest High High High High Gopher Hole Sink High High High High Gopher Sink High High High High Little Dismal Sink High High High High Osgood Sink High High High High Sullivan’s Tunnel High High High High Trog Sink High High High High Clay Sink High High High High Emerald Sink High High High High Indian Springs High High High High McBride Spring High High High High Sally Ward Spring High High High High River Sinks High High High High Wakulla Spring High High High High Unnamed Cave (3 miles High High High High south of Woodville, FL) Unnamed Sink (SE of High High High High SR 61/Cnty Ln Rd)
Woodville Karst Cave Crayfish SSA Report Page 19 May 2017
Table 3.5.2. Relative condition of factors used to determine Woodville Karst cave crayfish population resiliency. Population High Moderate Low Resiliency Factor Adequate Fresh Water groundwater maintains groundwater maintains groundwater maintains Availability normal annual spring/sink between minimum and well below normal annual water levels normal annual spring/sink spring/sink water levels water levels Sufficient Water Quality water appears to water appears to water appears unable, provide appropriate provide marginal or nearly unable, to conditions for conditions for support crayfish crayfish occupation crayfish occupation occupation Suitable Detrital Input vegetation provides vegetation provides vegetation is absent and/or detritus directly to the limited detritus directly to land management spring and land the spring and/or land practices do not maintain management practices management practices vegetation maintain vegetation maintains limited vegetation
Woodville Karst Cave Crayfish SSA Report Page 20 May 2017
CHAPTER 4 – FACTORS INFLUENCING VIABILITY
In this chapter, we evaluate the past, current, and future factors that are affecting what the Woodville Karst cave crayfish needs for long term viability. Aquatic cave systems face a multitude of natural and anthropogenic threats and stressors. Generally, these factors can be categorized as either environmental stressors (e.g., development, agriculture practices, forest management, or regulatory frameworks) or systematic changes (e.g., climate change, invasive species, barriers, or conservation management practices) (Figure 4.1). Current and potential future effects, along with current distribution and abundance help inform viability and, therefore, vulnerability to extinction.
Figure 4.1. Influence diagram illustrating how environmental stressors and systematic changes influence habitat factors which in turn influence Woodville Karst cave crayfish population size and resiliency.
Woodville Karst Cave Crayfish SSA Report Page 21 May 2017
4.1 Habitat Loss, Destruction, or Modification
In general, crayfish species are threatened by the present or threatened destruction, modification, or curtailment of their habitat or range by extensive degradation of aquatic and riparian habitats in the Southeast due to direct alterations of waterways such as impoundment, diversion, dredging and channelization, and draining of wetlands, and by land-use activities such as development, agriculture, logging, and mining (Benz and Collins 1997 and Shute et al. 1997). However, information is limited as to whether these activities represent actual or active threats to the Woodville Karst cave crayfish. Populations are prone to potential pollution and detrital change, and there is concern that the aquifer system may be receiving pollutants from the Tallahassee area.
According to the United States Census, the human population in the southeastern US has grown at an average annual rate of 37.9% since 2000 (US Census 2017, pp. 1-4), by far the most rapidly growing region in the country. This rapid growth has resulted in expanding urbanization, sometimes referred to as “urban sprawl.” Urban sprawl increases the connectivity of urban habitats while simultaneously fragmenting non-urban habitats such as forests and grasslands (Terando et al. 2014, p.1). In turn, species and ecosystems are impacted by the increased sprawl, including impacts to water pollution, local climate conditions, and disturbance dynamics (Terando et al. 2014, p.1). Table 4.1.1 shows the population projections for counties currently included in the range of Woodville Karst cave crayfish. Population projections for Leon County include the potential for growth and groundwater impacts associated with the city of Tallahassee.
Direct alterations of waterways (including impoundment, diversion, dredging, and channelization), draining of wetlands, dewatering of groundwater systems, and instream gravel mining threatens rare species of crayfish in the Southeast (Walsh 2001, p. 83). We contacted Northwest Florida Water Management District’s (NWFWMD) Bureau of Water Resource Evaluation, which is responsible for the establishment of minimum flows and water levels for major springs and rivers. The NWFWMD indicated that groundwater pumping was not an issue in the watershed, based on observed increases in discharge that could be related to water contributions from swallets and sinks to the regional karst system from due to improvements in stormwater management and stream flows, and sea level rise causing more fresh water staying in the system (Coates 2017). The NWFWMD is also currently working on minimum flow requirements for Wakulla and Sally Ward Springs and plan to have those completed by 2020. As part of the process, NWFWMD takes into consideration the biological needs of protected species, such as cave crayfish. We have been unable to find any information showing that the Woodville Karst cave crayfish is being affected by direct alterations of waterways, draining of wetlands, groundwater dewatering, or instream gravel mining. Woodville Karst Cave Crayfish SSA Report Page 22 May 2017
Very narrowly endemic crayfish are susceptible to extinction from even relatively minor habitat losses (Herrig and Shute 2002, p. 538). Anthropogenic activities on the surrounding landscape that affect aquatic cave habitat for the Woodville Karst cave crayfish (e.g., logging, agriculture, and development) have been occurring throughout the narrow range of these species for more than a century. Similar to other troglobitic species, P. orcinus is dependent on organic detritus from the surface for food (Deyrup and Franz 1994), the input levels of which Hobbs and Franz (1986, p. 518) suggest are low for springs. However, the aquatic cave habitats with which the species is associated remains intact, and there is no evidence of a reduction of range or a decline in population size.
There are several likely reasons for the apparent rarity of the Woodville Karst cave crayfish. The species is relatively small and difficult to recognize when collected, is not utilized for food or bait, and inhabits aquatic cave systems that are generally inaccessible to collectors without specialized equipment. Further, there have been few and limited efforts to define the range of the crayfish, and no efforts to determine their true population size. Therefore, there is no available information on known or suspected population declines of this cave crayfish species due to local habitat modification actions.
The Woodville Karst cave crayfish is potentially susceptible to habitat damage or destruction from pollution of groundwater or aquifer (Dickson and Franz 1980, Walsh 2001, p. 83). The city of Tallahassee and urbanized portions of Leon County are located just north of the Wakulla springs karst system. Despite previous studies indicating that contamination of groundwater from nitrification is not a significant problem in the Southeast (Spalding and Exner 1993, p. 395), there is documented degradation of the water quality of Wakulla Spring over the past 30 years, primarily due to wastewater treatment and septic system practices, although improvement has been observed in recent years. From 1970 to 1990, nitrate-nitrogen concentrations have risen from approximately 0.3 mg/L to 1.0 mg/L at Wakulla Spring. The most recent (2006) nitrate- nitrogen concentrations are between 0.6 mg/L and 0.8 mg/L (FDEP 2006, p.30). Degradation of spring water quality from increased nutrient inputs can result in biochemical changes that negatively impact aquatic cave dwelling species (Walsh 2001, pp. 83-84). Elevated nutrient concentrations are considered to have contributed to the proliferation of the invasive exotic plant, Hydrilla (Hydrilla verticillata), which is a major problem for Wakulla Springs State Park and has degraded habitat quality in the spring and its run FDEP (2006, p. 30), but do not have a direct effect on stygobitic organisms living in the aquifer.
As of 2006, a number of efforts have been undertaken to protect the Wakulla Spring system, including the acquisition of 7,367 acres by the State of Florida in Wakulla County for water Woodville Karst Cave Crayfish SSA Report Page 23 May 2017 quality protection (includes the 4,200-acre Wakulla State Forest adjacent to the state park); relocation of the state park’s wastewater treatment facility; discontinuance of fertilizer application by the Florida Department of Transportation (FDOT) on 195 miles of state roads in the springshed; and restricted vehicle access to connected sinkholes on some larger private ownership. Additional stormwater improvements have also been implemented by Leon County and the City of Tallahassee (FDEP 2006, pp. 32-33), totaling over $300 million (Florida Springs Institute 2014, p. 4). Reduction of nutrient inputs into the spring system is likely to result in corresponding improvements in water quality, given the correlation between nitrate source inputs and concentration in similar Florida karst springs in Suwannee and Lafayette counties (Katz et al. 1999, p. 49).
Table 4.1.1. Population projection by select county based on 2015 estimates (FEDR 2015). % Change County 2015 2020 2025 2030 2035 2040 2045 2015-2045 Wakulla 31,283 33,524 35,586 37,427 39,131 40,726 42,190 34.9 Leon 284,443 301,530 316,486 328,887 339,682 350,151 360,007 26.6
4.2 Regulatory Mechanisms
4.2.1 Land and Water Development Permitting
Surface water flow provides recharge to aquifers and springsheds, and alterations to surface water flow can result in impacts to spring flow and available fresh water. Permits to fill wetlands and to fill, culvert, bridge, or re-align streams or water features are issued by the U.S. Army Corps of Engineers under Nationwide, Regional General Permits, or Individual Permits.
Nationwide Permits are for “minor” impacts to streams and wetlands, and do not require an intense review process. These impacts usually include stream impacts under 150 feet, and wetland fill projects up to 0.50 acres. Mitigation is usually provided for the same type of wetland or stream impacted, and is usually at a 2:1 ratio to offset losses and make the “no net loss” closer to reality. Regional General Permits are for specific types of impacts that are common to a particular region; these permits will vary based on location in a certain region/state. Individual permits are for the larger, higher impact, and more complex projects. These require a complex permit process with multi-agency input and involvement. Projects requiring these types of permits are reviewed individually and the compensatory mitigation chosen may vary depending on project and types of impacts.
Woodville Karst Cave Crayfish SSA Report Page 24 May 2017
Environmental Resource Permits (ERP) are required by the NWFWMD for most types of land development, most types of land disturbance, and/or construction of ponds, structures, ditches, and impoundments at residential, commercial, and industrial developments. The NWFWMD Bureau of Water Resource Evaluation is also responsible for the establishment of minimum flows and water levels for major springs and rivers. As part of those responsibilities, the Bureau considers the habitat requirements of listed aquatic species in their evaluations (K. Coates, pers. comm.).
4.2.2 State Listing Status
The Florida Fish and Wildlife Conservation Commission’s 2012 State Wildlife Action Plan lists P. orcinus as a Species of Greatest Conservation Need (FWCC 2012, p.79). This ranking is based on two criteria for the species: rarity (fewer than 10,000 individuals range-wide) and being considered biologically vulnerable (which includes being designated on the IUCN list as “near threatened” or above) (FWCC 2012, p. 44). State recognition and tracking of the known populations of the Woodville Karst cave crayfish help ensure its consideration under existing State and Federal regulatory mechanisms.
4.2.3 Protection of Springs and Aquifers
In addition to water quality protections mentioned above, site protection is afforded to the species where its karst window access points occur on public lands, as described in section 3.2.2. For P. orcinus, these include springs and sinks located in the Apalachicola National Forest, Wakulla State Forest, and Edward Ball Wakulla Springs State Park. Wakulla and Leon counties have established Spring Protection Zones for significant portions of the springshed, and a major private landowner (St. Joe Corporation) has implemented measures to prevent damage to sinks located on their properties (Florida Springs Institute 2014, pp. 3-4). Therefore, we have found no information that regulatory mechanisms are currently inadequate for the protection of known populations and habitats of P. orcinus.
4.3 Climate Change
Our analyses under the Act include consideration of ongoing and projected changes in climate. The terms "climate" and "climate change" are defined by the Intergovernmental Panel on Climate Change (IPCC). "Climate" refers to the mean and variability of different types of weather conditions over time, with 30 years being a typical period for such measurements, although shorter or longer periods also may be used (IPCC 2012, p. 557). The term "climate Woodville Karst Cave Crayfish SSA Report Page 25 May 2017 change" thus refers to a change in the mean or variability of one or more measures of climate (e.g., temperature or precipitation) that persists for an extended period, typically decades or longer, whether the change is due to natural variability, human activity, or both (IPCC 2012, p. 557). Various types of changes in climate can have direct or indirect effects on species. These effects may be positive, neutral, or negative and they may change over time, depending on the species and other relevant considerations, such as the effects of interactions of climate with other variables (e.g., habitat fragmentation). In our analyses, we use our expert judgment to weigh relevant information, including uncertainty, in our consideration of various aspects of climate change.
Most climate change models predict increased extreme weather events, such as floods and droughts (e.g., Lubchenco and Karl 2012, p. 36). The Woodville Karst cave crayfish inhabits aquatic caves, which can exhibit fluctuating groundwater levels during extreme seasonal hydrographic cycles. Caine (1978, p. 322) noted that this species is not capable of successfully surviving desiccation. However, Woodville Karst cave crayfish are highly mobile and have been found at significant depths within aquatic cave systems. Therefore, we find no direct evidence that the Woodville Karst cave crayfish will be vulnerable to increased frequency of extreme weather events.
4.3.1 Sea Level Rise and Seawater Intrusion
Climate change may also be accompanied by sea level rise. Annual rates of sea level rise at Apalachicola, FL (southwest of areas inhabited by Woodville Karst cave crayfish) have averaged approximately 1.96 mm (0.08 in) over the period of record (Figure 4.3.1)(NOAA 2017). Projected sea level rise for coastal Wakulla County in year 2080 is 0.32 m (1.05 feet) (Harrington and Walton 2008, p. 12). Sea level rise may result in an increase in salt water intrusion into the karst freshwater aquifer system as a result of associated increases in hydraulic pressure on the aquifer; however, the mechanics of the coastal aquifer system are complex and dynamic. Generally, seawater is kept out of the conduit system by freshwater hydraulic pressure resisting against seawater intrusion (Werner and Simmons 2009, pp. 197-198). However, Xu et al. (2016) documented seawater intrusion into the Woodville Karst Plain conduit network during periods of low precipitation. Their analysis of precipitation and electrical conductivity data indicates that seawater intrusion into the karst system does occur, traveling 11 miles against the prevailing regional hydraulic gradient to Wakulla Spring (Xu et al. 2016, p. 2). This increase in seawater intrusion into the karst conduit system may be contributing to increased freshwater discharge rates periodically observed in some springs (e.g., Wakulla Springs) in recent years.
Woodville Karst Cave Crayfish SSA Report Page 26 May 2017
Dye trace studies indicate that water entering the conduit system at Lost Creek Swallet, located down gradient from Wakulla Spring, flows southward when freshwater is discharging from the aquifer via the Spring Creek Spring Complex (SCSC), which is the conduit system’s outlet to the Gulf of Mexico. However, freshwater entering Lost Creek Swallet is transmitted northward to Wakulla Spring during periods of extended low precipitation when the SCSC is not discharging freshwater at the coast. This indicates that under extended low rainfall conditions, the potentiometric gradient in conduits southwest of Wakulla Spring reverses and runs against the prevailing regional gradient. (Xu et al. 2016, p. 4). Coupled with electrical conductivity data, Xu et al. (2016) were able use these observations to show that the salt water – freshwater interface in the conduit system moves inland when the balance between the freshwater and seawater hydraulic pressures is reduced.
Sea level rise would result in increased hydraulic pressure and therefore the potential for increased salt water intrusion into the conduit system. However, we are unable to conclude that the current predicted rates of sea level rise are will significantly affect the viability of the species over the next 50 years for several reasons by reducing the availability of freshwater habitat. First, the species is able to move vertically within spring and sink systems and can quickly adapt to changes in the availability of freshwater within the conduit system (Moler 2016). Salt water is also denser than freshwater and therefore descends as it intrudes inland through the aquifer (Zhang et al. 2002, p. 233), reducing the likelihood that it will reduce the availability of freshwater in the conduit system as distance from the ocean increases. Finally, habitats occupied by the Woodville Karst cave crayfish are located 3 to 43 km (2 to 27 miles) from the coast, at elevations of 1.5 to 15 m (5 to 50 feet) above sea level, though many occupied habitats within the conduit system are significantly below sea level. Although seawater intrusion and transport in karst aquifers can occur over extremely long distances, increases in conductivity noted at the vent of Wakulla Spring, which is the southern-most site occupied by Woodville Karst cave crayfish, are small in an absolute sense (Xu et al. 2016, p. 9).
Woodville Karst Cave Crayfish SSA Report Page 27 May 2017
Figure 4.3.1. Average annual rates of sea level rise for Apalachicola, FL.
4.4 Overutilization
There is a potential threat of overutilization to imperiled species. In particular, the threat to crayfish species from overutilization is from the collection of individuals for bait or food. Due to its existence in difficult to access aquatic cave habitats, it is not surprising that there is no information that this species is being utilized for food or bait.
The species and its habitats are not known to be targeted for significant scientific or educational collections. The species and its habitats are not known to be targeted for significant scientific or educational collections. Florida State Code 68A-9.002 authorizes the Director of the Florida Fish and Wildlife Conservation Commission to issue permits to collect any wildlife species for scientific or conservation purposes, which are required for activities that are otherwise prohibited. Based on the limited number of specimens (27) located at the U.S. National Museum, and the difficulty in accessing aquatic cave habitat, collection has been minimal. The Florida Division of Recreation and Parks also requires a Scientific Research and Collection Permit to collect any wildlife species for scientific purposes on State Park land under Florida Statute Chapter 258.008 and Chapter 62D-2 of the Florida Administrative Code. Florida Statute Chapter 810.13 makes it unlawful to remove, kill, harm, or otherwise disturb any naturally occurring organism within a cave (including springs and sinkholes), except for safety or health reasons. There is no information indicating that this species is sought for the pet trade.
Woodville Karst Cave Crayfish SSA Report Page 28 May 2017
The Edward Ball Wakulla Springs State Park Unit Management Plan (FDEP 2007, p. 56) states that blind crayfish are vulnerable to over collecting, and stress that the protection of troglodytic fauna is a goal of park staff. This is evidenced by the fact that no specimen collections of any troglodytic fauna have been authorized since the U.S. Deep Caving Team’s 1987 diving project.
4.5 Disease and Predation
Disease agents and pests identified for freshwater crayfish include viruses, bacteria, rickettsia- like organisms, fungi, protists, and metazoans (Evans et al. 2002, p.1). However, detailed information on most disease agents, disease conditions, and symbiont associations is lacking (Evans et al. 2002, p. 3), and there is no reported information on the presence of disease or parasites in the Woodville Karst cave crayfish. Natural predators are found in the Wakulla karst cave system occupied by P. orcinus, including the American eel. While predation by naturally occurring predators is a normal aspect of the population dynamics of a species, it is not known to be a threat. In addition, nothing indicates that predation by non-native predators is currently affecting the Woodville Karst cave crayfish.
4.6 Summary
We were unable to find any direct link between landscape level threats due to direct alterations of waterways (including impoundment, diversion, dredging, and channelization), draining of wetlands, dewatering of groundwater systems, instream gravel mining, or by land-use activities such as development, agriculture, logging, and mining, and the conservation status of the Woodville Karst cave crayfish.
Information acquired during our review indicated that Woodville Karst cave crayfish continue to persist throughout their limited historical range. In addition, the species is difficult to collect and identify, and populations are likely underestimated.
Our review of the best available scientific and commercial information revealed that the Woodville Karst cave crayfish is poorly known and additional research is needed to define range, abundance, and population trends. However, during our status review, we did not document any specific significant threats to the species or its habitat throughout the currently known range, or within a significant portion of the range. We found no evidence that the species has experienced curtailment of range or habitat, or is affected by disease or predation, commercial or recreational harvest, the inadequacy of existing regulatory mechanisms, or any other natural or manmade factor.
Woodville Karst Cave Crayfish SSA Report Page 29 May 2017
CHAPTER 5 – SPECIES VIABILITY
5.1 Introduction
We have considered what the Woodville Karst cave crayfish needs for viability and the current condition of those needs (Chapters 2 and 3), and we reviewed the risk factors that are driving the historical, current, and future conditions of the species (Chapter 4). We now consider what the species’ future conditions are likely to be. We apply our future forecasts to the concepts of resiliency, redundancy, and representation to describe the future viability of the Woodville Karst cave crayfish.
The Woodville Karst cave crayfish was historically known from 18 springs and sinks and has recently been observed at 2 of those locations. Current surveys should be completed for this species to confirm their presence. The extant populations currently are assumed to have primarily high habitat quantity and quality, as described in Chapter 3.3, and most of the populations are not at risk due to potential habitat modification from land management activities. Due to the site protections afforded to the existing population sites of Woodville Karst cave crayfish that are located on public lands, future impacts from habitat modification are not expected to directly impact these populations. However, the risk of regional groundwater pumping and drought resulting in lowered aquifer levels and a concomitant reduction in available fresh water in the cave system is of concern.
Wakulla Spring, one of the largest springs in the highly-connected Woodville Karst Plain system, has been increasing in spring flow over the past few years. Though it is not clear why this occurring, there are a number of swallets and sinkholes north of the city of Tallahassee that may be contributing increased recharge to the groundwater aquifer as a result of changes in stormwater management and stream flows. The regional spring system also has a connection to the Gulf of Mexico via underwater spring vents that typically discharge freshwater to the ocean, but with sea level rise, freshwater flow may be reduced, resulting in more freshwater staying in the system (K. Coates, pers. comm.; Xu et al. 2016, pp. 3-4).
The viability of Woodville Karst cave crayfish depends on maintaining multiple resilient populations over time. Given our uncertainty regarding if and when springs and sinks occupied by Woodville Karst cave crayfish will experience a reduction or elimination of available fresh water in the future, we have forecasted what the Woodville Karst cave crayfish may have in terms of resiliency, redundancy, and representation under three plausible future (over the next 50 years) scenarios:
Woodville Karst Cave Crayfish SSA Report Page 30 May 2017
(1) All or most springs/sinks occupied by Woodville Karst cave crayfish experience no measureable drop in available fresh water; (2) Available fresh water in springs/sinks occupied by Woodville Karst cave crayfish is reduced but not eliminated; and (3) Springs/sinks occupied by Woodville Karst cave crayfish experience an extreme reduction or elimination of available fresh water.
Because we are not certain of how groundwater decline will specifically affect available fresh water in springs and sinks, examining how the Woodville Karst cave crayfish populations will respond under these three fresh water availability scenarios allows us to consider the range of future effects of spring/sink freshwater availability decline on Woodville Karst cave crayfish populations.
5.2 Resiliency
As mentioned above, resiliency describes the characteristics of a species that allow it to recover from periodic disturbance, such as annual environmental variation and stochastic events. In general, Woodville Karst cave crayfish are adapted to the conditions of aquifer ecosystems. With not be expected to result in eventual population elimination.
The most important factor that may affect Woodville Karst cave crayfish resiliency is groundwater decline. We expect that groundwater levels may decline over time, but there is significant uncertainty over how that will affect fresh water availability. If fresh water availability is reduced due to lower aquifer levels caused by groundwater pumping or prolonged drought, we expect populations would likely be minimally impacted since the species has been found at significant spring depths and can move as groundwater levels decrease (Moler 2016). Because we are not able to predict the extent or location of fresh water availability reductions, we discuss how population resiliency would vary under each of the three potential fresh water availability scenarios:
Scenario 1: No measurable drop in fresh water availability
If expected future groundwater decline does not result in a measureable loss of fresh water availability over the next 50 years, most Woodville Karst cave crayfish populations are expected to maintain their current levels of resiliency. The populations would be likely to retain or improve their overall condition, as presented in Table 3.5.1, with 18 populations in good condition and therefore with high resiliency. Populations may experience short term reductions
Woodville Karst Cave Crayfish SSA Report Page 31 May 2017 in numbers and density, but given the natural range of variability in environmental conditions, they would be expected to rebound and remain secure.
Scenario 2: Available fresh water is reduced but not eliminated
If groundwater decline over the next 50 years leads to a minor reduction of fresh water availability, populations that experience reduced fresh water availability will have less resiliency than they currently do. We expect that because the springs and sinks currently occupied by Woodville Karst cave crayfish are connected through the karst conduit system, loss or reduction of fresh water availability would be relatively uniform across all springs and sinks and would result in a loss of population resiliency at all locations. Springs may experience somewhat less loss of resiliency due to changes in the hydraulic gradient such that some additional fresh water that typically discharges to the Gulf of Mexico is siphoned off to the springs. Currently, 18 populations are considered to be in good condition (= high resiliency). Some reduction in fresh water availability would change the resiliency of populations, so that 14 populations would have moderate resiliency and 4 would retain high resiliency (Table 5.2.1).
Scenario 3: Available fresh water is extremely reduced or eliminated
Elimination of fresh water availability would be catastrophic and likely result in the extirpation of affected populations. If groundwater level reduction translated to a loss of fresh water availability to this degree, we would expect all sink populations to be extirpated, and any remaining spring populations would be in poor or low condition (Table 5.2.1).
Table 5.2.1. Future conditions of Woodville Karst cave crayfish populations under scenario 2. Spring/Sink Adequate Fresh Sufficient Water Suitable Detrital Overall Condition Population Water Availability Quality Input Bird Sink Moderate Moderate High Moderate Culley’s Cave Moderate Moderate High Moderate Falcon’s Nest Moderate Moderate High Moderate Gopher Hole Sink Moderate Moderate High Moderate Gopher Sink Moderate Moderate High Moderate Little Dismal Sink Moderate Moderate High Moderate Osgood Sink Moderate Moderate High Moderate Sullivan’s Tunnel Moderate Moderate High Moderate Trog Sink Moderate Moderate High Moderate Clay Sink Moderate Moderate High Moderate Woodville Karst Cave Crayfish SSA Report Page 32 May 2017
Emerald Sink Moderate Moderate High Moderate Indian Springs High Moderate High High McBride Spring High Moderate High High Sally Ward Spring High Moderate High High River Sinks Moderate Moderate High Moderate Wakulla Spring High Moderate High High Unnamed Cave (3 miles Moderate Moderate High Moderate south of Woodville, FL) Unnamed Sink (SE of Moderate Moderate High Moderate SR 61/Cnty Ln Rd)
Table 5.2.2. Future conditions of Woodville Karst cave crayfish populations under scenario 3. Spring/Sink Adequate Fresh Sufficient Water Suitable Detrital Overall Condition Population Water Availability Quality Input Bird Sink N/A N/A Moderate Extirpated Culley’s Cave N/A N/A Moderate Extirpated Falcon’s Nest N/A N/A Moderate Extirpated Gopher Hole Sink N/A N/A Moderate Extirpated Gopher Sink N/A N/A Moderate Extirpated Little Dismal Sink N/A N/A Moderate Extirpated Osgood Sink N/A N/A Moderate Extirpated Sullivan’s Tunnel N/A N/A Moderate Extirpated Trog Sink N/A N/A Moderate Extirpated Clay Sink N/A N/A Moderate Extirpated Emerald Sink N/A N/A Moderate Extirpated Indian Springs Low Low Moderate Low McBride Spring Low Low Moderate Low Sally Ward Spring Low Low Moderate Low River Sinks N/A N/A Moderate Extirpated Wakulla Spring Low Low Moderate Low Unnamed Cave (3 miles N/A N/A Moderate Extirpated south of Woodville, FL) Unnamed Sink (SE of N/A N/A Moderate Extirpated SR 61/Cnty Ln Rd)
Woodville Karst Cave Crayfish SSA Report Page 33 May 2017
5.3 Redundancy
Redundancy means having sufficient numbers of populations for the species to withstand catastrophic events. A catastrophic event is defined here as a rare destructive event or episode involving many populations. The most likely catastrophic event for the Woodville Karst cave crayfish would be the loss of fresh water availability to occupied habitats. Drought and/or an increase in groundwater pumping of the aquifer could lead to fresh water availability decline or loss. As an endemic organism, the range of the Woodville Karst cave crayfish is naturally restricted, so it is not possible for this species to exhibit redundancy over a relatively large geographic area, which would provide some protection from local fresh water availability decline.
We evaluated redundancy under the same potential fresh water availability scenarios:
Woodville Karst Cave Crayfish SSA Report Page 34 May 2017
Scenario 1: No measurable drop in spring/sink fresh water availability
Under this scenario, fresh water availability would not decline in response to the projected levels of groundwater depletion, and we would expect most, if not all, populations to persist.
Figure 5.3.1. Current conditions of Woodville Karst cave crayfish populations rangewide.
Woodville Karst Cave Crayfish SSA Report Page 35 May 2017
Scenario 2: Fresh water availability is reduced but not eliminated
Under this scenario, we assume that all populations would exhibit some drop in resiliency.
Figure 5.3.2. Future conditions of Woodville Karst cave crayfish populations rangewide, under spring flow scenario 2.
Woodville Karst Cave Crayfish SSA Report Page 36 May 2017
Scenario 3: Fresh water availability is extremely reduced or eliminated
Under this scenario, the overall condition of most populations is expected to be low, and redundancy would be expected to be significantly reduced if fresh water availability results in population extirpations. Any Woodville Karst cave crayfish populations that persist in locations that retain some level of fresh water availability will likely have low resiliency and be extremely vulnerable to extirpation.
Figure 5.3.3. Future conditions of Woodville Karst cave crayfish populations rangewide, under spring flow scenario 3.
5.4 Representation
Representation means having the breadth of genetic and ecological diversity of the species to adapt to changing environmental conditions. Knowledge regarding genetic diversity in this
Woodville Karst Cave Crayfish SSA Report Page 37 May 2017 species is lacking, but genetic material was collected from Gopher Hole Sink on March 5, 2017 for testing in the future. Although we are not aware of any specific ecological diversity across the species’ range that might be important for future adaptation, it would be prudent to maintain as much geographic extent of the species’ range as possible to maintain any potential, but undetected, ecological diversity. To ensure adequate representation, it may be important to retain populations across the Woodville Karst cave crayfish’s current range to maintain the species’ overall potential genetic and life history attributes, buffering the species’ response to environmental changes over time.
We evaluated representation under the same potential fresh water availability scenarios.
Scenario 1: No measurable drop in fresh water availability
Under this scenario, fresh water availability would be maintained throughout the Woodville Karst cave crayfish range over the next 50 years. Representation across the range would be maintained at current levels providing for the preservation of the current level of representation.
Scenario 2: Fresh water availability is reduced but not eliminated
Under this scenario, we assume that one or more populations would exhibit a drop in resiliency over the next 50 years, such that springs or sinks that currently have high resiliency would have moderate resiliency. While these springs and sinks would experience a drop in resiliency, they are expected to persist. The Woodville Karst cave crayfish could experience some loss of representation but it would not eliminate the species entirely from a substantial geographical portion of the overall range.
Scenario 3: Fresh water availability is extremely reduced or eliminated
Under this scenario, we expect that over the next 50 years most, if not all, Woodville Karst cave crayfish populations would be extirpated, with perhaps only one or two populations with low resiliency remaining. We are unable to predict where any populations would persist.
5.5 Status Assessment Summary
We used the best available information to forecast the likely future condition of the Woodville Karst cave crayfish. Our goal was to describe the viability of the species in a manner that will address the needs of the species in terms of resiliency, redundancy, and representation. We considered the possible future condition of the species. We considered a range of potential Woodville Karst Cave Crayfish SSA Report Page 38 May 2017 scenarios that we think are important influences on the status of the species. Our results describe a range of possible conditions in terms of how many and where Woodville Karst cave crayfish populations are likely to persist into the future.
Several factors influence the future viability of the Woodville Karst cave crayfish. Loss or reduction of habitat due to development or land management activities is not expected to impact populations due to their location on protected public lands. Fresh water availability is the largest factor affecting future persistence of the Woodville Karst cave crayfish.
Under scenario 1, we would expect the Woodville Karst cave crayfish’s viability to be characterized by the same level of resiliency, redundancy, and representation that it exhibits under the current condition. We anticipate that current populations will persist, and to potentially identify additional populations during surveys of other sites within the current range of the species.
Under scenario 2, it is projected that in 50 years populations currently exhibiting high condition will exhibit moderate condition, and exhibit adequate levels of resiliency to continue to persist because suitable habitats will continue to be available. Although redundancy will be reduced, members of the genus Procambarus are historically characterized by a few isolated populations that continue to persist, perhaps because the genus is evolutionarily adapted to geographic isolation over geologic time. Although representation may be reduced, it is expected that most populations will continue to persist. Given the high connectivity of the Wakulla karst system, we would expect that genetic material would still be exchanged between populations. As such, we expect in 50 years, under scenario 2, the Woodville Karst cave crayfish’s viability will be characterized by many of the current populations.
Under scenario 3 we would expect the species viability to be characterized by catastrophic losses of resiliency, redundancy, and representation. Most, if not all springs and sinks would be expected to entirely lose flowing water, resulting in widespread extirpation of populations.
Woodville Karst Cave Crayfish SSA Report Page 39 May 2017
LITERATURE CITED
Benz, G.W. and D.E. Collins (editors). 1997. Aquatic Fauna in Peril: The Southeastern Perspective. Southeast Aquatic Research Institute Special Publication 1, Lenz Design and Communications, Decatur, GA. 553 pp.
Buhay, J.E. and K.A. Crandall. 2005. Subterranean phylogeography of freshwater crayfishes shows extensive gene flow and surprisingly large population sizes. Molecular Ecology, 14(14):4259-4273.
Caine, E.A. 1974. Zoogeography of the Floridian troglobitic crayfishes, genus Procambarus. American Midland Naturalist 92:2(487-492).
Caine, E.A. 1978. Comparative ecology of epigean and hypogean crayfish (Crustacea:Cambaridae) from northwestern Florida. American Midland Naturalist 99:2(315- 329).
Carroll, C., J.A. Vucetich, M.P. Nelson, D.J. Rohlf, and M.K. Phillips. 2010. Geography and recovery under the U.S. Endangered Species Act. Conservation Biology 24: 395-403.
Center for Biological Diversity (CBD). 2010. Petition to list 404 aquatic, riparian and wetland species from the southeastern United States as threatened or endangered under the Endangered Species Act. 1,145 pp. Available online at http://www.fisheries.noaa.gov/pr/species/petitions/alabama_shad_petition2010.pdf
Coates, K., Northwest Florida Water Management District, Bureau of Water Resource Evaluation. 2017. Phone conversation with USFWS regarding Big Blue Springs and Woodville Karst cave crayfish, groundwater withdrawal and spring minimum flows. February 28, 2017.
Deyrup, M., and R. Franz, eds. 1994. Rare and endangered biota of Florida: Vol. IV Invertebrates, University Press of Florida, Gainesville. 175 pp.
Dickson, G.W., and R. Franz. 1980. Respiration rates, ATP turnover and adenylate energy charge in excised gills of surface and cave crayfish. Comparative Biochemistry and Physiology Part A: Physiology 65(4):375-379.
Woodville Karst Cave Crayfish SSA Report Page 40 May 2017
Evans, L., A., B.F. Edgerton, F.J. Stephens, and R.M. Overstreet. 2002. Review of freshwater crayfish diseases and commensal organisms. AQUIS Review of Freshwater Crayfish Diseases, Pests, and Commodities. 140 pp.
Florida Department of Agriculture and Consumer Services, Division of Forestry (DOF). 2005. Wakulla State Forest Ten Year Resource Management Plan. Tallahassee, FL. 39 pp.
Florida Department of Environmental Protection (FDEP). 2006. Florida’s springs: strategies for protections & restorations. Tallahassee, FL. 177 pp.
Florida Department of Environmental Protection (FDEP). 2007. Edward Ball Wakulla Springs State Park Unit Management Plan. Available online at http://www.dep.state.fl.us/parks/planning/parkplans/EdwardBallWakullaSpringsStatePark.pdf
Florida Fish and Wildlife Conservation Commission (FWCC). 2012. Florida’s Wildlife Legacy Initiative: Florida’s State Wildlife Action Plan. Tallahassee, FL. 665 pp.
Florida Geological Survey (FGS). 2004. Springs of Florida. Tallahassee, FL. 658 pp.
Florida National Forests. 1999. Revised Land and Resource Management Plan for National Forests in Florida. Tallahassee: USDA Forest Service.
Florida Office of Economic and Demographic Research (FEDR). 2015. Medium projections of Florida population by county, 2020-2045. http://edr.state.fl.us/Content/population- demographics/data (accessed: 04/17/2017).
Florida Springs Institute. 2014. Wakulla Spring Restoration Plan. High Springs, FL. 131 pp.
Franz, R., J. Bauer, and T. Morris. 1994. Review of biologically significant caves and their faunas in Florida and South Georgia. Brimleyana, (20):1-109.
Franz, R., and D.S. Lee. 1982. Distribution and evolution of Florida's troglobitic crayfishes, Bulletin of the Florida State Museum, Biological Science, 28(3):53-78.
Harrington, J. and T.L. Walton. 2008. Climate change in coastal areas in Florida: Sea level rise estimation and economic analysis to year 2080. Florida State University report.
Woodville Karst Cave Crayfish SSA Report Page 41 May 2017
Herrig, J., and P. Shute. 2002. Chapter 23: Aquatic animals and their habitats. Southern Region, USDA Forest Service and Tennessee Valley Authority. 45pp. In: Wear, D. N. and J. G. Greis, eds. 2002. Southern Forest Resource Assessment – Technical Report. Gen. Tech. Rep. SRS-53. Asheville, NC. U.S. Department of Agriculture, Forest Service, Southern Research Station. 635pp. Available online at http://www.srs.fs.usda.gov/pubs/gtr/gtr_srs053.pdf
Hobbs, H.H., Jr., and R. Franz. 1986. New troglobitic crayfish with comments on its relationship to epigean and other hypogean crayfishes of Florida. J. Crust. Biol. 6(3):509-519.
Hobbs, H.H., Jr., H.H. Hobbs III, and M.A. Daniel. 1977. A review of the troglobitic decapod crustaceans of the Americas (No. 244). Smithsonian Institution Press.
Hobbs, H.H., Jr., and D. B. Means. 1972. Two new troglobitic crayfishes (Decapoda, Astacidae) from Florida. Proceedings of the Biological Society of Washington 84(46):393-410.
Intergovernmental Panel on Climate Change (IPCC). 2012. Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation. A Special Report of Working Groups I and II of the Intergovernmental Panel on Climate Change [Field, C.B., V. Barros, T.F. Stocker, D. Qin, D.J. Dokken, K.L. Ebi, M.D. Mastrandrea, K.J. Mach, G.-K. Plattner, S.K. Allen, M. Tignor, and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, UK, and New York, NY, USA, 582 pp.
Jegla, T.C., 1966. Reproductive and molting cycles in cave crayfish. The Biological Bulletin, 130(3):345-358.
Katz, B.G., H.D. Hornsby, J.F. Bohlke, and M.F. Mokray. 1999. Sources and chronology of nitrate contamination in spring waters, Suwannee River basin, Florida (No. 99-4252). US Dept. of the Interior, US Geological Survey; Branch of Information Services [distributor].
Longshaw, M., and P. Stebbing (eds). 2016. Biology and ecology of crayfish. Boca Raton, FL. 375 pp.
Lubchenco, J., and T.R. Karl. 2012. Predicting and managing extreme weather events. Phys. Today 65(3):31-37.
Moler, P., Florida Fish and Wildlife Conservation Commission. 2016. Discussion regarding Big Blue Spring and Woodville Karst cave crayfish during site visits to several springs in the Wakulla system. December 21, 2016. Woodville Karst Cave Crayfish SSA Report Page 42 May 2017
National Oceanographic and Atmospheric Administration (NOAA). 2017. Linear mean sea level (MSL) trends and 95% confidence intervals in feet/century. https://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?stnid=8728690.
Redford, K.H., G. Amoto, J. Baillie, P. Beldomenico, E.L. Bennett, N. Clum, R. Cook, G. Fonseca, S. Hedges, F. Launay, S. Lieberman, G. M. Mace, A. Murayama, A. Putnam, J.G. Robinson, H. Rosenbaum, E.W. Sanderson, S.N. Stuart, P. Thomas, and J. Thorbjarnarson. 2011. What does it mean to successfully conserve a (vertebrate) species? Bioscience 61:39–48.
Shute, P.W., R.G. Biggins, and R.S. Butler. 1997. Management and conservation of rare aquatic resources: A historical perspective and recommendations for incorporating ecosystem management. p. 445-466 In: Benz, G.W. and D.E. Collins (editors). 1997. Aquatic Fauna in Peril: The Southeastern Perspective. Southeast Aquatic Research Institute Special Publication 1, Lenz Design and Communications, Decatur, GA. 553 pp.
Spalding, R.F., and M.E. Exner. 1993. Occurrence of nitrate in groundwater—a review. Journal of Environmental Quality 22(3):392-402.
Taylor, C.A., M.L. Warren Jr. , J.F. Fitzpatrick Jr. , H.H. Hobbs III , R.F. Jezerinac , W.L. Pflieger, and H.W. Robison. 1996. Conservation status of crayfishes of the United States and Canada, Fisheries 21(4): 25-38.
Taylor, C.A., G.A. Schuster, J.E. Cooper, R.J. DiStefano, A.G. Eversole, P. Hamr, H.H. Hobbs, III., H.W. Robinson, C.E. Skelton & R.F. Thomas. 2007. A reassessment of the conservation status of crayfishes of the United States and Canada after 10+ years of increased awareness. Fisheries 22(8):372-387.
Terando, A.J., J. Costanza, C. Belyea, R.R. Dunn, A. McKerrow, and J.A. Collazo. 2014. The southern megalopolis: Using the past to predict the future of urban sprawl in the Southeast U.S. PLoS ONE 9(7): e102261. doi:10.1371/journal.pone.0102261
U.S. Census. 2017. United States population growth by region. https://www.census.gov/popclock/data_tables.php?component=growth (accessed: 4/17/2017).
U.S. Fish and Wildlife Service (USFWS). 2016. USFWS species status assessment framework: an integrated analytical framework for conservation. Version 3.4.8, dated August 2016. Available online at
Woodville Karst Cave Crayfish SSA Report Page 43 May 2017 https://www.fws.gov/endangered/improving_ESA/pdf/SSA%20Framework%20v3.4- 8_10_2016.pdf
Walsh, S.J. 2001. Freshwater macrofauna of Florida karst habitats. Pages 78-88 In: E. Kuniansky (ed.). U.S. Geological Survey Karst Interest Group Proceedings, St. Petersburg, Florida, February 13-16, 2001, USGS Water-Resources Investigations Report 01-4011.
Werner, A.D. and C.T. Simmons. 2009. Impact of sea‐level rise on sea water intrusion in coastal aquifers. Ground Water, 47(2):197-204.
Wolf, S., B. Hartl, C, Carroll, M.C. Neel, and D.N. Greenwald. 2015. Beyond PVA: why recovery under the Endangered Species Act is more than population viability. BioScience 65:200-207.
Xu, Z., S.W. Bassett, B. Hu, and S.B. Dyer. 2016. Long distance seawater intrusion through a karst conduit network in the Woodville Karst Plain, Florida. Scientific reports, 6.
Zhang, Q., R.E. Volker, and D.A. Lockington. 2002. Experimental investigation of contaminant transport in coastal groundwater. Advances in Environmental Research, 6(3):229-237.
Woodville Karst Cave Crayfish SSA Report Page 44 May 2017