Water Quality Threatens Endangered Salamanders
By: Christopher Garza
The Austin Blind Salamander (Eurycea waterlooensis) is one of the few species of salamander that are native to Texas waterways. This particular salamander species belongs to the Plethodontidae family and is an endemic species that is only known to exist within Austin's Barton Springs. Although it may not be around much longer. This is due to the recent increase in construction and pollutants that have found their way into Barton Springs from local waterways, runoffs, and shear negligence by local swimmers. Salamanders within the Eurycea genus all have a very high sensitivity to any abnormal changes in their environment. The Austin Blind Salamander stands at the forefront of a local environment movement in Austin. Its strange name comes from exactly what you would think. They do not possess image forming eyes which has been a result of its adaptations to their natural habitat within the dark underground caves of the Edwards Aquifer. And since they primarily live in these caves that feed into Barton Springs, some of which are too dangerous for researchers to explore, their exact population numbers can't be fully accounted for. There are three endemic blind species of Salamander living within Austin. The Austin blind salamander, the San Marcos blind salamander, and the Texas blind salamander. All of which, are under stress due to the environmental impact that the city of Austin's growth has put on local aquifers. According to austintexas.gov "Very little is known about these subterranean salamanders since their main habitat is not readily accessible by humans, and they are only occasionally observed in the springs." The graph to the right shows a trend of how a water quality test is performed within the surrounding water sources of Barton Springs. The result of the blue line is the square footage of the area surveyed, and the red line represents the depth they surveyed. This method seemed to survey two purposes. The first was to test the quality of water and how much was being discharged into each spring. And the second being to uncover any one of the three salamanders that reside in any of the Edwards Aquifer springs and capture them for further study. Every researcher tackles their portion of the spring by an assigned area of square footage. When they determine their dig site, they then lightly sift through the top layer of sediment. Taking quality measurements for chemicals, nutrients, ph balance, and the different water temperatures of each area. This process sometimes uncovers salamanders, but that is usually a very rare event. Since they mainly dwell in the dark recesses deep down in the caves of the aquifer. They are completely aquatic and never need to surface for air unlike some of their other more well-known terrestrial relatives. The only time they are usually seen is when they are tossed out of spring outflows which can be attributed to low discharge and water flow (usually juveniles who have been washed out accidentally). However, while the majority may tend to live in the spring caves, some juveniles and adults who have been tossed out may reside in the Benthic Cover (The sediment surface and sub-surface layers of lakes or oceans). Which is where most people, albeit a rare opportunity, may come across them. Source: www.amphibiaweb.org/species/5870
Construction Runoff Responsible For Salamanders Decline
By: Christopher Garza
Barton Springs houses a very delicate ecosystem. And in a not so distant past Austin had neglected to take any notice of the harm they inflicted. It wasn’t until the 1980s that the city of Austin began to take active recourse against the decades of negligent abuse the city had placed on the springs and pools natural habitats. Barton Springs consists of four natural springs located at Zilker park. All of which receive their water directly from the Edwards Aquifer. The largest spring is the Barton Spring (also known as Parthenia, "the Mother spring"), which supplies water to the main pool along with the three other smaller springs associated with it. The smaller springs are the Eliza, Old Mill, and Upper Barton Spring. All of them are significantly smaller than their mother, but on a good day, they each discharge about 3 million gallons of water per day according to the United States Geological Society. So how do the springs play into the Austin, San Marcos, and Dallas blind salamanders decline? Well, for starters, the Barton springs pool is the only one that maintains a consistent volume year round. The other three have the tendency to dry out or shift in temperature during the dryer parts of the season. Which can be detrimental for any living organisms who aren't able to move across land in search of a more habitable water source. This is where the endemic salamanders have an issue. While they mostly reside in the caverns of the Edwards Aquifer they will sometimes get pushed into spring outflows by accident. This usually happens when there is a change in flow pressure, and if the water source becomes cut off the salamander has no way of returning back to the caverns. You may be thinking: why doesn't it just walk to another water source that is more habitable? Well, these particular species of salamander belong to the plethodontids Eurycea genus. Meaning that they are fully aquatic and don’t develop lungs in their adult stage, but instead breathe through a set of bright red gills. Which either contracts or swells in size. Depending on the amount of oxygen that is in the water. The average yearly temperature of Barton Springs has a strong relationship on whether or not the pools are habitable for the already struggling species. Although the water typically stays around a cool 20°C when it's full. This temperature may fluctuate during the hotter months. If one of the salamanders is unlucky and gets washed into one of the smaller pools they may run the risk of drying up with the pool (typically occurs more with juveniles). However, these species aren’t known to typically spend too much time swimming in the water columns, and will instead walk along the substrate. But not a lot of research of them in their natural habitats has been achieved. Due to the difficulty and danger of exploring the underwater caverns. This may be why these particular species are only known to be native within the Austin area. They are able to use the underground water systems in order to maintain their survival. But are currently endangered and run the risk of dying out due to harmful pollutants and urban construction poisoning the underground springs.
Rain Can Do More Harm Than Good
By: Christopher Garza
Rain may do more harm than good when it comes to the balance of the salamander’s environment. The rain is crucial when it comes to the stabilization of Barton Creek, and naturally it would be nothing more than a positive thing. But due to Austin’s growth there has been a considerable amount of runoff and pollutants that have been getting washed into the springs. Now to humans that might not have a huge impact, but to the local flora and fauna it may mean the difference between life and extinction. Recent studies have shown that the decrease in ecological plant life may be one of the leading causes as to why the local salamander populations may have become endangered. Polluted water can easily disrupt the natural balance that the Edwards Aquifer would otherwise maintain in Barton Springs. Some of the pollutants can easily kill off local plant life. Which in turn would kill off the smaller organisms that eat the plant life and in turn kill off the salamanders that eat the smaller organisms. These species of salamander are very sensitive to their surroundings. They need a constant supply of clean water with a relatively high flow. The pollution, over use of water, and yearly fluctuation of water flow has a huge impact on the well-being of these species. Austin has tried to reduce the effects that urbanization has had on surrounding habitats, but the road to recovery can be a long one. For example, back in the 1980s Austin had to undo years of previous damage to the Barton Springs pools. Which was caused by the use of bleach in order to clean and maintain the pools, and for over 70 years’ no one realized the harmful impact that it had on the local ecosystems. This blunder had a tremendous impact on the viability of the springs, but has now since been in the process of being reversed. Now, compound this damage with the amount of runoff that gets washed into the springs or absorbed by the ground. The city of Austin is doing what it can, but every time it rains it fights an uphill battle against all the foreign pollutants. No one truly knows why the ecology is so sensitive around Austin, but research and conservation efforts are constantly being improved in order to accommodate the environments use for future generations of humans and salamanders alike.
Austin Blind Salamander Anatomy
By: Christopher Garza
This particular species of salamander evolved to be paedomorphic. Which means that it does not go through a metamorphose to enter adulthood and to develop the attributes that make it possible to live on land like most of its relatives. So it spends the entirety of its life under water. But in order to live in water this species needs a constant flow of water and a consistent temperature of 70 degrees Fahrenheit in order to live comfortably. They are extremely sensitive to any changes in their environment. Which might be why they prefer to stay in the dark caverns beneath Barton Springs. Their body structure has a translucent surface and three pairs of red external gills that surround the neck. They have 4 toes on their front feet and 5 toes on their back feet, and can be any size from a ½-inch to 3-inches depending on what stage of their life cycle they are in. Their color ranges from a pearly-white to a dark lavender color which can be speckled with blue and black dots. They possess a square shaped snout with eye-spots positioned directly above it. But they do not possess image-forming eyes. Hence the name, Blind Salamander. As for their reproduction, no eggs have every been viewed in the wild, but researchers have been able to successfully breed them in captivity in order to gain a better understanding of their reproductive nature. The eggs hatch in 3-4 weeks. Hatchlings are a 1/2-inch in total length (snout to tip of tail), often without fully formed limbs. Juvenile salamanders become sexually mature at about 11 months and grow to about 3 inches as adults. Salamanders can continue to reproduce to an age of at least eight years. As for their diet, they mostly eat aquatic macro invertebrates and may sometimes turn cannibalistic. They have been known to eat juvenile salamanders and salamander eggs. Since they don't have eyes and live in total darkness. The way they hunt their prey is by sensing any changes of vibrations in the water and then striking with their jaws. Source: http://www.austintexas.gov/content/1361/FAQ/2422
San Marcos Blind Salamander
By: Christopher Garza
The San Marcos salamander (Eurycea nana) is one of three endangered species that lives within the San Marcos pool which is a local water source that is fed by the Edwards Aquifer. It is a native species to Texas and is endemic to Spring Lake. Which is an adjacent downstream portion of the upper San Marcos River. Unlike the Austin blind salamander who thrives in the deep caverns, and sometimes benthic layer of Barton springs, this particular species likes to dwell closer to the surface. Hiding in small patches of moss and algae which provide it excellent cover against its natural predators. However, the moss and algae serves a dual purpose as the salamander's hunting grounds. Their diet consists of mostly tiny aquatic crustaceans, aquatic insects, and snails. This species can only be found in the San Marcos river. So one of the greatest threats to its survival is a reduced flow of water from the springs that feed into it. But this doesn't just affect the salamanders. It also has a huge impact on the other plants and animals that are dependent on the springs. The growth of surrounding cities has led to a higher water usage as well as increased water pollution and silt accumulation. And since this species can only be found in the San Marcos river, one of the greatest threats to its survival is greater water usage by the local residents.
San Marcos Salamander Anatomy
The San Marcos salamander, Eurycea nana is an endangered lungless salamander that averages about 2 inches long, but may reach up to lengths as big as 3.25 inches. It is one of the smallest species of the genus Eurycea. These salamanders have 5 toes on their rear feet and 4 on the front. They possess gill fringes behind their heads which have 16 to 17 coastal grooves. Their back is a light brown, flecked with random spots of pink, and peppered with yellowish spots all throughout its body. It possesses distinctive large eyes that are encased by a dark ring around the lens. Males have more poorly defined mental and caudal hedonic glands than females. Their developed, pigmented gills are maintained throughout adulthood, but gases are exchanged almost entirely through cutaneous respiration. Which is a form of respiration in which gas exchange occurs across the skin of an organism rather than through the gills or lungs. The vents of males are lined with papillae, contrasting with the smooth folds in females. This species is voiceless and earless. The San Marcos salamander is typically active in surface vegetation except in extreme winter weather where it stays beneath underwater logs and boulders. It is often found sitting stationary in algal vegetation waiting for prey, which it then quickly grabs with its jaws and crushes to consume. Its predation threats mostly come from local fish. The primary being sunfish, but bullhead catfish and largemouth bass have also been known to be potential threats. (Mitchell 1990, Petranka 1998, Bartlett and Bartlett 1999, Tupa and Davis 1976, Herbeck and Larson 1998) Source: http://animaldiversity.org/accounts/Eurycea_nana/ Image Source: https://www.jstor.org/stable/pdf/1444041.pdf?seq=1#page_scan_tab_contents
San Marcos Salamander Reproduction
Males are sexually mature at 19 to 23.5 mm and females when they are longer than 21 mm. There is only vague information on the reproduction of Eurycea nana, and reproduction has never been viewed in their natural habitats. Strongly acyclic oviposition and the presence of gravid females and very small larvae during every month of the year suggests that breeding occurs year round. There is not a pronounced peak in breeding. As has been observed in artificial habitats, the average egg clutch is 20 and the jelly-covered eggs are usually laid in standing pools with thick vegetation. After a 24-day period in the eggs, larvae-like tadpoles emerge. (Mitchell 1990, Petranka 1998, Tupa and Davis 1976) (Mitchell, 1990; Petranka, 1998; Tupa and Davis, 1976) Source: Source: http://animaldiversity.org/accounts/Eurycea_nana/
Dallas Blind Salamander
The Dallas Blind salamander (Eurycea rathbuni) is the third endangered species that dwells within the sub-terranean caverns of the Edwards Aquifer. The Texas Blind Salamander faces much of the same issues as its cousins. The overall adult population does not have a definitive number due to their main environment being deep within the caverns of the Edwards Aquifer. Which is currently still too dangerous for human exploration. They can be found within the range of the San Marcos Pools. This salamander is more commonly known as the Texas Blind Salamander, and unlike the Austin and San Marcos salamanders this species isn't as illusive from the public eye. While it is paedomorphic. It does not go through a metamorphose to develop air breathing lungs. And yet It has been observed climbing rock faces and swimming in open water. But even though it may be able to tolerate different environments better than its cousins. It is still highly susceptible to water quality changes, flow changes, and the groundwater pollutants that have been plaguing the several endemic salamander species. Which has been increasing over the years due to increased pumping and water usage to support residential and commercial developments (Matthews and Moseley 1990). Source: http://www.iucnredlist.org/details/full/39262/0
Dallas Blind Salamander Anatomy
The Dallas blind salamanders are adapted to living their lives in complete and total darkness inside the San Marcos pool deep within the caves beneath the Edwards Aquifer. While their main habitat may be scarce in light these organisms that live there make up for it with their unique adaptations. The Dallas salamanders possess pigment less skin and the adults have non-functioning eyes that are replaced with tiny black dots. Their head is wide and flattens out to the tip of their snouts. Its neck is surrounded by red gills that are adapted for only aquatic life. Not much is known about how they behave in the wild, but efforts have been made by researchers to study these creatures in captivity. These salamanders are quite a bit larger than their cousins. They can reach anywhere from 3.5 inches to 5.5 inches long, and possess thin wispy legs, and a long fin-like tail to help them move throughout the water and hunt their prey. Their diet usually consists of aquatic invertebrates such as snails, and small shrimp or crayfish that wander the bottoms of the San Marcos pool. It senses its prey by monitoring the slightest changes in water pressure. So even though it can't see it doesn’t have a problem gathering food. Source: https://www.nwf.org/Wildlife/Wildlife-Library/Amphibians-Reptiles-and-Fish/Texas-Blind-Salamander.aspx
Dallas Blind Salamander Reproduction
In captivity these salamanders are at the top of the food chain, but not much else is really known about how they behave in their natural habitat. Some studies believe that these salamanders have to worry about sunfish, largemouth bass, and bullhead catfish. It's not certain if these are real threats to the salamander, but they are suspected to pose a potential risk to the population. These predators may also play a pivotal role in the viability of their reproduction. Their eggs might possibly be in danger of being eaten by these larger predators. However, in captive studies, these salamanders are believed to reproduce year round. But large fish aren't the largest threat to these animals. Like their cousins, they are highly sensitive to changes in water quality, water flow, and groundwater pollutants due to increased urbanization.