Algae blooms received a lot of press the summer of 2014 thanks to the massive cyanobacterial blooms in Lake Erie, one of which resulted in the city of Toledo having to stop providing water to the city. In Lake Austin, where the city of Austin derives its drinking water, algae blooms and associated taste and odor problems are closely monitored. The summer of 2014 we saw a larger than normal diatom algae bloom (Fig. 1). However, diatoms are typically harmless and generally do not adversely impact drinking water supply. As with previous years (Fig. 2), in late summer and through the fall we saw the biomass of cyanobacteria increase in lower Lake Austin (Fig. 1). As of January 2015, scientists are analyzing the species composition of the cyanobacteria assemblage to determine if organisms capable of producing toxins are present. But, the bloom was nowhere near the magnitude experienced by the coastal communities of Lake Erie in 2014, and was less than 60% as large as the bloom experienced in the Lake Austin Reservoir in 2013 (Fig. 2). Of interest though was the fact that the cyanobacterial bloom lasted longer in the summer and fall of 2014 than in previous years.
Figure 1. Total algal and Diatom biomass (cells/mL; left axis) and Cyanobacterial biomass (cells/mL; right axis) for the period June 28 through January 11th, 2014 (more data will be added). Austin Water Utility recognizes and monitors a phytoplankton bloom when the total cell count is > 10,000 org/mL (solid horizontal line) and a cyanobacterial bloom is triggered at a count > 300 org/mL (dashed horizontal line).
Figure 2. Algal biomass (cells/mL) based on total cell counts (A); diatoms (B); and cyanobacteria (C) for the summers from 2009 to 2014.
As Central Texas emerged from drought conditions late in 2015 into 2016, the 2017 summer has seen a return of large discharges through the Highland Lakes similar to the pre-drought period (i.e., pre-2009). The Highland Lakes were nearly at 100% capacity late in 2015 due to major rain events. Through most of the mid-to-late summer period, discharges were generally low, enabling a long duration (~4 month), large magnitude (~35,000 org/mL), cyanobacteria bloom to develop (Fig 3).
With the Highland Lakes full into 2016, large hydrological pulses to meet downriver agriculture demands occurred throughout the spring and early summer, influencing cyanobacteria bloom dynamics. A large bloom developed earlier than normal as discharges through Lake Austin declined, but the bloom rapidly peaked and crashed, and the total number of bloom days was only 106 days (Fig.4)
In 2017, we have seen large discharges from Lake Travis for most of the summer, until Hurricane Harvey moved into the region. As such, in Lake Austin, as of early November (typically past the peak date of cyanobacteria bloom conditions), less than 30 days have been in a bloom condition, consistent with predictions based on persistent large early- and mid- summer discharges from Lake Travis through Lake Austin.
Visit the Austin Lakes Index webpage.
The logs you see on the shoreline are made of “Coir” and have been placed with plantings for erosion control and lakeshore habitat.
Coir is the natural fiber found in ripe coconut husks, and it has been used for centuries to make ship ropes due to its durability and resistance to water damage. One of the modern uses for coir includes mats or logs of coir fiber bound by coir ropes for erosion control. Coir is anchored in areas with loose soils that need stabilization including stream banks, wetlands and construction sites. The advantage of using coir logs for erosion control (rather than rocks or bulkheads) is that the coir allows vegetation to grow within it as it slowly biodegrades becoming part of the matrix of the soil. When the coir has finally biodegraded (years later), the roots of the vegetation then provide the long-term stability of the soil which provides natural and beneficial integrity to the land and water.
Although appealing in its low cost, durability and ability to biodegrade, it was unclear if coir logs would be successful in stabilizing the shoreline of Lake Austin due to the intense wave energy from recreational boating. A pilot study to test this method in Lake Austin was initiated in Summer 2009. After 5 years of observation, it was determined that coir logs and plants can be successful (under certain circumstances) in stabilizing and restoring a shoreline to a more natural state. Most coir logs deteriorated slowly and the remaining fiber has roots and stems growing throughout. The pilot study provided valuable information regarding placement, location, timing and plant species.
The Watershed Protection Department has recently installed an additional ~2,000 feet of coir logs and plantings along shorelines managed by the City and County. The sites are currently greatly impacted by erosion and the effort may slow down erosion long enough to develop a resilient vegetation community benefiting both stability, habitat and water quality.
Coir logs and plantings 4 years after installment
Ecosystem services, stated simply, are the benefits humans derive from the environment. Food, clean air and water, fiber for clothes….these are obvious and significant examples of supplies upon which we are dependent. What keeps the water and air clean? How can the land keep providing food to feed billions of people? Why am I happier when out in ‘nature’? Is my home worth more because of its proximity to a resource (e.g., lake, river, park, forest)?
Turns out, the environment is providing more for us then we tend to think about. The myriad processes that occur ‘outside’ give rise to the services we need and desire. Scientists have grouped the activities and products of nature into four categories: First, Provisioning Services. These are the services we are most familiar with (and grateful for) such as food, potable water, wood and fiber, and fuel. Then, we have the Regulating Services. These occur on a scale that may be imperceptible, when things are good, but relate to services very important to us including flood regulation, water purification and quantity, and disease regulation (think Ebola). Those services are still pretty tangible (and relatively easy to monetize). Services for which we have an innate desire are the Cultural Services. These include having a spiritual connection to nature, enjoying the aesthetic quality of the environment, and of course recreational activities (boating, hiking, camping, etc). Probably the most overlooked but important of all the Ecosystem Services provided by nature are what are known as the Supporting Services. The supporting services are the processes and functions of nature that give rise to all the other services listed above. We desire breathable air, plentiful food, and fiber, so we plant trees and shrubs that take up carbon dioxide and provide raw materials and fruits for consumption. Nutrient cycling mediated by plants and microbes help keep our water clean, our food nutritious (high in nutrients and other compounds), and slow climate change. A diverse, species rich landscape full of animals and plants gives us a sense of peace and fulfillment. Without nature and the environment doing what it does through the Supporting Services, we would not have the other services of interest. It is for the protection and sustainability of the environment that the Supporting services are so often studied by scientists and at heart, our regulations and protections are in place (e.g., minimizing nutrient pollution, deforestation, impervious cover). As human populations increase, our footprint on the landscape grows, and our need for ‘natural capital’ becomes greater to support mankind, it will be the protection, regulation, and protection of the Supporting Services that will ensure sustainability of all Ecosystem Services required and desired for the wellbeing of mankind.
The City of Austin Watershed Protection Department sincerely appreciates concerns about the fishing resources of Lake Austin. City of Austin staff are coordinating directly with Texas Parks and Wildlife (TPWD) biologists to address concerns relating to the status of the fishery in Lake Austin. The City of Austin and TPWD are actively monitoring conditions in Lake Austin. Both the City of Austin and TPWD believe through combined natural recruitment, mortality of sterile grass carp, and enhancements that may be possible as a result of on-going City research efforts, the vegetation and bass fishery will recover.
Unfortunately, Lake Austin has experienced a fast decline in aquatic vegetation habitat. We were hoping for a more controlled decline, but other factors combined with the sterile triploid grass carp stocking led to the current low level of aquatic vegetation in the lake. Grass carp management has been studied for many years. The approach applied to Lake Austin was a replication of published scientific studies. For a decade we used a conservative incremental stocking rate which combined with a scientifically reported mortality rate avoided overstocking, allowing for continued fish habitat persistence. When extreme drought effects led to the rapid expansion of Hydrilla to more than 600 acres, the rate of fish stocking was increased to ensure the primary functionality of Lake Austin – water supply and flood protection – was not compromised. Our objective remains finding a medium where all lake use interests are met, including the anglers. The Lake Austin fishery is not doomed, and will recover.
For many years Lake Austin has provided excellent conditions to support a quality bass fishery with high trophy potential. Water temperatures, aquatic habitat, Florida largemouth bass stockings and responsible anglers are the reason for the success of this fishery. However, creating a trophy fishery takes more than just Hydrilla. It takes regulation, outreach, genetic stockings, habitat management, and the help of Mother Nature. The interests of anglers, boaters, skiers, swimmers, home owners, consumptive water rights, and operating infrastructure must be all considered equally.
While the explosion of Hydrilla temporarily amplified the great fishing at Lake Austin, it hindered other interests. For example, the last time Lake Austin had a heavy biomass of Hydrilla during a flood event the lake could not serve its purpose of flood control properly and millions of dollars in damage were caused to shoreline properties and the Tom Miller Dam. Excessive Hydrilla also causes safety concerns related to boating and swimming.
Aquatic vegetation challenges have existed in Lake Austin since the 1950’s, with Hydrilla being the most recent concern beginning in 2002. A partnership between TPWD, LCRA, City of Austin, and the Lake Austin home owners was developed to address this issue. The bass anglers at that time were asked to organize and delegate a representative to partner, but no one was
Control measures were put into effect to prevent potential detriment impacts caused by excessive Hydrilla growth. It was determined that Hydrilla was to be controlled through Triploid Grass Carp stocking to protect multiple user interests. TPWD is the agency responsible for permitting and regulating the stocking rates for Grass Carp in Lake Austin. As the Hydrilla aggressively expanded and impacted primary reservoir functionality and safety, we were forced to slowly increase stocking rates to 54 fish/acre of Hydrilla before we were able to see control. That resulted in the highest number of Grass Carp ever in Lake Austin. Chemical treatment for this type of coverage was not an option and mechanical harvesters could not keep up with growth and can exacerbate spread of Hydrilla.
The increased stocking rate did result in unintended significant fish habitat reduction in 2014. Additionally, untimely scouring, cool temperatures this past winter, continued drought, and altered hydrology have all resulted in a shift within this artificially created and highly regulated system to an alternative state dominated by planktonic algae rather than submersed vegetation. Throughout this summer and fall, short heavy rains have exacerbated the turbidity of Lake Austin through inputs from overland flow and tributaries. However, the current turbid condition of Lake Austin is temporary. There are still numerous propagating sources for native vegetation, protected by cages managed by the City of Austin. As the grass carp population is reduced through natural mortality, vegetation will re-colonize the lake and once again produce clear water conditions.
As published mortality rates of grass carp are estimated at 33% mortality per year, no organized grass carp harvesting effort is necessary or would be the most effective use of City resources. As the Grass Carp population shrinks and native vegetation and Milfoil expands, we should see the fishery recover. Should Hydrilla return in excess amounts in the future, it will be necessary to utilize grass carp again as a control agent. Thus, the stocking permit should not be eliminated especially given the difficult and lengthy process involved in procuring the permit initially.
Given our interest in the recreational as well as municipal use needs of Lake Austin, below is a brief list of efforts TPWD and the City of Austin are utilizing to understand the impacts of Grass Carp on this unique system and work towards system recovery.
- We will continue to monitor aquatic vegetation habitat quarterly to see what changes occur.
- We are studying trophic changes in the fishery food web as it relates to the changes in the plant community.
- TPWD will continue to stock Florida largemouth bass as needed to keep the growth potential strong at the lake.
- TPWD will continue to perform annual electrofishing surveys to monitor fish populations in relation to habitat changes.
- We will continue to support efforts to establish native aquatic vegetation in the lake with the use of cages.
- We will work closely with the water management authorities to advise on best management practices that would also consider the interests of our anglers.
- We will keep the public informed of our progress on these and other topics.
We urge anglers to organize groups to represent their interests at meetings. The group can even become a chapter of Friends of Reservoirs (www.waterhabitatlife.org) and help us enhance fisheries habitat at Lake Austin and other area lakes. TPWD has done so with other groups on Canyon, Buchanan, LBJ, Inks, Granger, and Georgetown lakes. Please share this message with the anglers at Lake Austin.
Please contact Dr. Brent Bellinger (email), 512-974-2717) with the City of Austin if you would like to discuss this further. Thank you for sharing your concern, and for your support to protect Lake Austin.
The Austin reservoirs are in a constant state of flux. Natural and anthropogenic forces influencing the chemical, biological, and physical characteristics of Lake Austin and Lady Bird Lake include: altered flow regimes dictated by water availability, increased development, and introductions and control of species. Each reservoir is cherished for their aesthetic, recreational, commercial, and municipal benefits. In order to balance the needs of such different users while sustaining an ecologically desirable ecosystem, it is essential to understand the relationship between water chemistry and biological structure of the reservoirs.
One of the most important aspects of reservoir ecosystems influenced by the chemical and biological composition of the system is the flow of energy from primary producers to top consumers. Knowledge of the components of the food web (sources; e.g., aquatic vegetation, phytoplankton) supporting species of interest (consumers; e.g., largemouth bass) is necessary in order to make predictions of potential shifts in community structure that may result from environmental changes and for the implementation of adaptive management strategies ensuring sustainability of desired biological communities. This project aims to collect water and a myriad of potential sources and terminal consumers for measurement of 13C and 15N isotopic signatures.
Stable isotopes are a widely used tool for tracing the flow of nutrients and energy through aquatic ecosystems (Middelburg 2014). Data derived in this study should elucidate the linkages (i.e., source-consumer) and complexity (e.g., trophic levels, number of resources utilized) of the food web, as well as the importance of internal relative to external energy and nutrient inputs to the reservoirs of Austin. Mixing models will be developed to give frequency distributions (i.e., relative contributions) of lower trophic level components in a consumer’s diet (Phillips and Gregg 2003; Phillips et al. 2005). This study will serve to not only describe in quantified detail the current food web structure of the reservoirs, heretofore unknown, but will also serve as a baseline for comparison as the structure of the reservoir’s change under as yet unknown pressures or public desires (e.g., increased vegetation in Lake Austin; increased flows reducing vegetation in Lady Bird Lake).
Visit the Hydrilla web page for more information.
Plants in aquatic systems are often overlooked as critical components of healthy ecosystems. Aquatic and riparian plants can provide valuable invertebrate, fish and wildlife food and cover, improve water clarity and quality, reduce shoreline erosion and sediment re-suspension, and help prevent spread of nuisance exotic plants. These qualities contribute significantly to ecosystem health and function, which in turn improves the value of the lake as a natural resource.
Inland water bodies in the U.S. include reservoirs, large and small lakes, permanently inundated wetlands, ponds, and riverine systems. Waterbodies exhibiting poor ecosystem health often exist in one of three conditions interrelated to aquatic plants: 1) they completely lack native aquatic plants, 2) they support native plant communities that are insufficient to provide system-wide benefits, or 3) they are infested with nuisance species that cause both environmental and water project use problems.
Because larger aquatic systems (generally greater than 100 acres) are logistically difficult to apply full-scale plantings, the US Army Corps of Engineers – Engineer Research and Development Center ERDC has developed an approach for accelerating the natural process of aquatic plant establishment and spread by utilizing founder colonies. Founder colonies are typically comprised of moderately small (usually less than one acre) plantings made at strategic locations within the waterbody. The principle function of a founder colony is to overcome one of the major impediments to aquatic vegetation establishment: availability of propagules for natural spread. Continual provision of propagules (seeds, fragments, etc.) from founder colonies ensures that they are present when conditions are suitable for natural spread to other areas of a lake. Once established, founder colonies spread in two manners, including vegetative growth from the founder colony itself (e.g., along stolons or rhizomes) and formation of new colonies from fragments, seeds, etc. In addition to supplying propagules, founder colonies provide immediate small-scale (up to 25 acres benefit from each acre of founder colony) habitat improvement in large and intermediate systems. In addition to protecting plants, the structure of enclosures themselves serve as refugia for aquatic organisms such as small fish in waterbodies prone to periodic disturbances (drought, floods, etc.) even when they do not support plants.
In 2016 and 2017, City staff expanded our herbivore exclusion pen installations, putting in large (20' x 50') pens, connecting neighboring pens, and extending pen boundaries to the shoreline. At two sites in Lake Austin we have effectively created vegetation plots each exceeding 4,500 sq ft in size.
From the approx. 36 one gallon plants originally planted in each pen, we have seen over the past two years a completely expansion and filling-in of the pens with desired, native vegetation. In 2017 we installed a new vegetation pen in Lady Bird Lake. With the return of large discharges through Lady Bird Lake, the native aquatic plant cabomba, which had been prolific in Lady Bird Lake the previous three years, was effectively washed out of the reservoir. In order to re-establish some aquatic vegetation, we installed a new 20' x 50' herbivore exclosure pen just downriver of MoPac. The pen was planted in July and by October was completely filled in with vegetation creating a complex canopy of leaves submersed, floating, and emergent of the water surface.
Pen was planted in July 2017.
Pen full of vegetation in October 2017.