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Review of the Edwards Aquifer Habitat Conservation Plan: Report 2 (2017)

Chapter: 5 Applied Research Program

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Suggested Citation:"5 Applied Research Program." National Academies of Sciences, Engineering, and Medicine. 2017. Review of the Edwards Aquifer Habitat Conservation Plan: Report 2. Washington, DC: The National Academies Press. doi: 10.17226/23685.
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5

Applied Research Program

EAA RESPONSE TO COMMITTEE’S FIRST REPORT

In NRC (2015) a number of broad recommendations and conclusions were made about the Applied Research Program that covered three general areas: improving the process used to solicit, review, and manage the Applied Research Program; adopting and implementing a data management system; and increasing understanding of the Comal Springs riffle beetle. The Committee was pleased to learn that, in general, the Edwards Aquifer Authority (EAA) responded by implementing most of its recommendations in these areas, as discussed below.

Improvements to the Applied Research Program Process

The Committee recommended that the process of identifying, soliciting, reviewing, and selection of projects be more transparent by soliciting additional proposals from new proposers and asking for more input from the Science Committee on the key elements to be included in the requests for proposals as well as on the technical merits of resulting proposals. The EAA responded by appointing an Applied Research Working Group and modifying their procedures for soliciting, reviewing, and awarding research projects (EAA, 2015). These new procedures were in place for the selection of the 2016 Applied Research projects.

In addition, the EAA also took steps to try to increase the number of outside experts submitting proposals to the Applied Research Program by broadly advertising the research solicitations. In addition, the EAA used lit-

Suggested Citation:"5 Applied Research Program." National Academies of Sciences, Engineering, and Medicine. 2017. Review of the Edwards Aquifer Habitat Conservation Plan: Report 2. Washington, DC: The National Academies Press. doi: 10.17226/23685.
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erature and web searches to identify scientists whose interests and expertise aligned with the subject areas of the 2016 request for proposals and made sure these potential applicants were aware of the research opportunities. It is unclear whether these efforts led to additional involvement of outside experts in the Applied Research Program. The EAA is encouraged to persist in these efforts to attract interested experts who are currently not involved in the various Habitat Conservation Plan (HCP) efforts by looking for ways to remove conditions that might overly restrict the pool of potential applicants. For example, the Committee noted that the time period from release of the request for proposals to the deadline for proposal receipt for the 2017 program was relatively short, making it difficult for experts not familiar with the EAA to respond to the requests for proposals.

Finally, the Committee recommended that a process be implemented to allow Applied Research projects to have a duration of more than one year if needed to meet the goals of the study. The EAA and the Applied Research Working Group are working to implement this recommendation, with one current project on the Comal Springs riffle beetle (CSRB) life history currently having a two-year duration.

Implement a Database Management System

Through the Applied Research Program and the monitoring program the EAA has collected a large of amount of data covering a wide variety of physical, chemical, biological, and hydrologic variables. In NRC (2015) the Committee recommended that these data be organized, stored, and curated in a database management system to ensure that all data are available in a well-documented manner to both internal and external parties. The EAA has responded positively to this recommendation. They hired a new database manager and are now using an off-the-shelf database management system called Aquatic Informatics–Aquarius Samples. The data management staff is currently working to populate this system with the accumulated data. The Committee applauds this action as it will make data analyses and modeling calibration and validation efforts more efficient and streamlined going into the future. This system will also serve as a long-term data repository and archival mechanism. The Committee continues to encourage the EAA to use the data management system being implemented to allow greater data discovery and access by the outside scientific community and the public. Access to the core monitoring data can lead to greater involvement of stakeholder groups, encourage participation by a broader group of experts, and result in a better overall program.

Suggested Citation:"5 Applied Research Program." National Academies of Sciences, Engineering, and Medicine. 2017. Review of the Edwards Aquifer Habitat Conservation Plan: Report 2. Washington, DC: The National Academies Press. doi: 10.17226/23685.
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Recommendations for Additional CSRB Studies

The EAA has made considerable effort to implement the Committee recommendations for additional Applied Research studies regarding the biology of the CSRB, with most/all of the 2016 projects focused on understanding the CSRB. The three 2016 proposals include studies on the CSRB functional group classification, tolerances to high temperatures and low oxygen conditions, and life history:

  1. Evaluation of the Trophic Status and Functional Feeding Group Status of the Comal Springs Riffle Beetle prepared by Weston Nowlin and Dittmar Hahn of Texas State University (EAHCP Proposal # 148-15-HCP).
  2. Evaluation of Long-Term Elevated Temperature and Low Dissolved Oxygen Tolerances of the Comal Springs Riffle Beetle prepared by Weston Nowlin and Benjamin Schwartz of Texas State University (EAHCP Proposal # 146-15-HCP).
  3. Evaluation of the Life History of the Comal Springs Riffle Beetle prepared by BIO-WEST Project Team (EAHCP Proposal # 147-15-HCP).

The first project, which would evaluate the trophic and functional feeding group status of the CSRB, may contribute to a better understanding of the habitat breadth of the species. The proposal argues that the CSRB populations are largely restricted to areas adjacent to spring outflows, areas of the benthic habitat that also collect substantial amounts of coarse organic matter in the form of leaves and small branches, and that these food resources also serve as habitat. If this is indeed the case, the proposed project has the potential to reveal an alternative sampling approach for the CSRB that could be a reasonable reflection of population densities. Using stable isotopes the proposed research would identify the primary food resources of the CSRB, and if linked to the primary habitat of larvae and adults would reveal a habitat that could be sampled quantitatively. This proposed research project is one of the first to take a novel approach to identifying the food resources and habitat of the beetle with potentially transformative results that could lead to quantitative population estimates important for monitoring and ecological models.

The second project listed above was not directly related to the recommendations put forth by the Committee in NRC (2015), namely the project evaluating temperature and oxygen requirements of the CSRB. Understanding the tolerance values of the CSRB has merit for future estimates of how the species will respond to changes in abiotic conditions; however, without an objective and quantitative method for estimating the population size, models that incorporate these variables will not provide additional informa-

Suggested Citation:"5 Applied Research Program." National Academies of Sciences, Engineering, and Medicine. 2017. Review of the Edwards Aquifer Habitat Conservation Plan: Report 2. Washington, DC: The National Academies Press. doi: 10.17226/23685.
×

tion for better population predictions. The proposed project would provide new data on how individual beetles respond to increased water temperature and associated decreased dissolved oxygen in a series of laboratory studies. The project would also evaluate the tolerances of surrogate species for the CSRB. There are three potential concerns for this study. As described in NRC (2015), there are potentially significant biological differences among Elmidae species, so that the use of surrogate species may not adequately represent the CSRB. Similarly, the results from laboratory studies do not always represent how a species will respond in the natural environment, an issue likely important for the CSRB given that it is considered a subterranean organism that comes to the benthic surfaces for some feeding. The last concern is that the laboratory facilities that were proposed have suffered large mortalities of the CSRB adults, with water quality changes the suspected cause for these deaths. At the time of this writing, the cause has not been definitively identified and the issue remains unresolved.

The third proposed research project is on CSRB life history, which is an important effort for understanding how the populations of the CSRB change naturally as part of the life cycle and also how they may respond to changing environmental conditions. Also, understanding the life history and life cycle characteristics will allow scientists to evaluate the results from previous and ongoing efforts to measure, and eventually predict, the population abundances of the CSRB. It should be noted that the proposed project on CSRB life history characteristics will be conducted at the same laboratory facility as that of the temperature and oxygen study, and may suffer from the same potential issues as described above.

A major recommendation for the Applied Research Program from NRC (2015) was to better (1) quantify the CSRB population densities and/or (2) calibrate the cotton-lure method of sampling so that it could potentially be an efficient and reliable way to estimate populations. The inability to calibrate the cotton-lure method of sampling with any real densities of the CSRB in the system is a considerable weakness, making the representativeness of this sampling approach for estimating population densities unknown and making monitoring for CSRB population estimates difficult if not impossible to achieve. If the species population cannot be estimated with some degree of certainty and account for responses to flow variability, its status as an indicator species for other endangered or threatened species in the ecosystem should be re-addressed.

Recognizing the weaknesses of the CSRB sampling, the Applied Research Work Group created a fourth 2016 Applied Research study on CSRB sampling (EAHCP ARWG, 2015), although no proposal was written. To fulfill this project, a regional workgroup was created to establish a Standard Operation Procedure (SOP) for how to deploy, retrieve, and score cotton lures when collecting CSRBs. The main goal was to standardize data col-

Suggested Citation:"5 Applied Research Program." National Academies of Sciences, Engineering, and Medicine. 2017. Review of the Edwards Aquifer Habitat Conservation Plan: Report 2. Washington, DC: The National Academies Press. doi: 10.17226/23685.
×

lected by all entities, for entry into a newly created database. This work group, called the cotton-lure SOP workgroup, was attended by all in the region that collect CSRBs, including HCP contractors and staff, and it is not a work group of the HCP. The main deliverable was an SOP and field data sheet that all entities agreed to use.

The goals of developing a standard operating procedure for using the cotton lure sampling approach for the CSRB and the creation of an associated long-term database are to be commended. The plan consists of construction and materials used for the cotton lures, the arrangement of the cotton lure within a wire cage that is used for deployment, and data collection protocols for the deployment, monitoring, and collection. Although the procedure is complete and takes into account most of the information important for a long-term database, including a standardized data sheet, the following concerns are noted. First, there should be a method to provide standardized data that accounts for the amount of time that the cotton lure has been deployed. For example, some lures will be placed for the recommended four weeks, but it is possible that others will be placed for other time periods (e.g., three weeks). One hundred CSRB specimens captured over four weeks is not equivalent to 100 specimens collected in only three weeks. By stating data as the number of CSRB specimens per day or week, the data derived from this sampling approach would be better standardized. Second, the findings from the 2015 CSRB Connectivity Study (see subsequent section) should be utilized, which suggest that terrestrially derived leaf and wood organic matter is important to the CSRB populations. Thus, it would be useful to identify the type, and estimate the relative amount, of organic matter near or at the cotton lure placement locations. The SOP data collection sheet already requires that the presence of different organic matter types (e.g., wood debris, leaves, roots, macrophytes) be recorded. This could be modified to include an estimated surface area covered by each organic matter type.

RECENTLY COMPLETED APPLIED RESEARCH

For completeness, Tables 5-1, 5-2, 5-3, and 5-4 list all studies that have been part of the Applied Research Program or have been special studies critical to the ecological model or the implementation of minimization and mitigation measures. Those studies that were completed in late 2014/2015 are discussed in greater detail below. Discussion of the 2013 and 2014 studies can be found in NRC (2015).

Suggested Citation:"5 Applied Research Program." National Academies of Sciences, Engineering, and Medicine. 2017. Review of the Edwards Aquifer Habitat Conservation Plan: Report 2. Washington, DC: The National Academies Press. doi: 10.17226/23685.
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TABLE 5-1 Fountain Darter Applied Research Projects

Study Title Year Objective
1. Fountain Darter Food Source Study to Determine the Critical Thermal Maximum of Hyalella azteca 2013 To determine the critical thermal maximum of Hyalella azteca, a supposed fountain darter food source. Final report completed (BIO-WEST and Baylor University, 2013).
2. Effects of Vegetation Decay and Water Quality Deterioration on Fountain Darter Movement 2014 To describe fountain darter movement as a function of water quality and vegetation decay using fluorescent tags. Final report completed (BIO-WEST, 2014a).
3. Effects of Low-Flow on Fountain Darter Fecundity 2014 To determine if changes in physical habitats, especially low-growing and dense vegetation, will reduce the reproductive readiness and success of the fountain darter. Final report completed (Texas State University and BIO-WEST, 2014a).
4. Effects of Predation on Fountain Darter Population Size at Various Flow Rates 2014 To determine if flow conditions may cause different relationships between predator and prey and habitat utilization. Final report completed (Texas State University and BIO-WEST, 2014b).

TABLE 5-2 Submersed Aquatic Vegetation (SAV) and Texas Wild Rice Applied Research Projects

Study Title Year Objective
1. Field vs. Laboratory Study—Comparison of the Responses of Three SAV 2013 Preliminary study to compare aquatic vegetation (Ludwigia, Cabomba, and Sagittaria) growth over time when conducted simultaneously in laboratory and in-situ experiments held at similar flow and water quality conditions. Final report available (BIO-WEST and Baylor University, 2013).
2. Vegetation Tolerance Studies A and B 2013 To evaluate the effects of elevated water temperatures in combination with low CO2 and minimal flow on Ludwigia, Cabomba, Vallisneria, and Riccia in the lab and in ponds. Final report available (BIO-WEST and Baylor University, 2013).
3. pH Drift Study—Effects of image utilization by select SAV 2013 To determine which of the major SAV species of the Comal River are capable of utilizing image as a carbon source for photosynthesis. Final report available (BIO-WEST and Baylor University, 2013).
Suggested Citation:"5 Applied Research Program." National Academies of Sciences, Engineering, and Medicine. 2017. Review of the Edwards Aquifer Habitat Conservation Plan: Report 2. Washington, DC: The National Academies Press. doi: 10.17226/23685.
×
Study Title Year Objective
4. Converting SAV Biomass to Percent Areal Cover 2014 To develop an empirical relationship between vegetation percent cover and biomass for use in the ecological model. This will provide a realistic way to convert percent cover maps to levels of biomass present within the system. Final report available (Doyle et al., 2014).
5. Ludwigia Interference Plant Competition Study 2015 To evaluate Ludwigia repens growth competition and interference by Hygrophila sp. and Hydrilla sp. To better understand dispersal of Ludwigia and refine biological objectives. Final report completed (Center for Reservoir and Aquatic and Systems Research and BIO-WEST, 2015).

TABLE 5-3 Comal Springs Riffle Beetle Applied Research Projects

Study Title Year Objective
1. Extended Low-Flow Period Effects on Comal Springs Riffle Beetle 2014 To study CSRB survivorship inside of the springs during periods of low flow and flow cessation, including associated physical (i.e., temperature) and chemical (i.e., DO, pH, conductivity) changes. They designed “aquaria” that allow replicate samples and manipulation of flows to simulate up-welling, middle-welling, and top-welling. Final report completed (BIO-WEST, 2014b).
2. Determination of Limitations of Comal Springs Riffle Beetle Plastron Use during Low Flow 2014 Adult riffle beetles have fine hairs (plastron) that trap air next to their body, acting as a gill to breath underwater. Plastrons require clean, cool water to function. Determination of the limitations of the plastron to reduced dissolved oxygen levels and elevated temperatures would be useful in habitat management and modeling for the conservation of the CSRB. Final report completed (Gibson et al., 2013).
3. Estimate Comal Springs Riffle Beetle Population in Comal Springs/Landa Lake 2014 Sample a random distribution of previously sampled and unsampled springs for CSRB within Comal Springs/Landa Lake to estimate the CSRB population. Final report completed (Zara Environmental, 2015).
Suggested Citation:"5 Applied Research Program." National Academies of Sciences, Engineering, and Medicine. 2017. Review of the Edwards Aquifer Habitat Conservation Plan: Report 2. Washington, DC: The National Academies Press. doi: 10.17226/23685.
×
Study Title Year Objective
4. Comal Springs Riffle Beetle Habitat Connectivity 2015 Evaluate the importance of the surface, riparian, and submerged food sources to the ecology of the CSRB at the springs. Final report completed (BIO-WEST and Texas State, 2015).
5. Evaluation of the Long-Term, Elevated Temperature and Low Dissolved Oxygen Tolerances of the Comal Springs Riffle Beetle 2016 Examine the individual and combined roles of relatively long term increases in temperatures and declines in DO concentrations on CSRB and potentially several other riffle beetle species in an experimental laboratory-based setting. Proposal available (Nowlin and Schwartz, 2015).
6. Evaluation of the Life History of the Comal Springs Riffle Beetle 2016 Things to be studied in laboratory environment include eggs, mating, larvae, larval completion, pupation, adult lifespan, and fecundity. Proposal available (Bio-WEST, 2016).
7. Evaluation of the Trophic Status and Functional Feeding Group Status of the Comal Springs Riffle Beetle 2016 Utilize a stable isotope approach to determine the feeding ecology of the CSRB and other invertebrates found in the upper Comal system. Also, characterize the microbial communities associated with biofilms in the Comal and compare them to the communities found within the guts of CSRB and the biofilms found in different microhabitats within Comal Springs. Proposal available (Nowlin and Hahn, 2015).
8. CSRB Quantitative Sampling Techniques 2016 Determine efficacy of different sampling techniques. No proposal available, but a standard operation procedure was created that satisfies as the deliverable for this project.

DO = dissolved oxygen

TABLE 5-4 Other Applied Research Projects or Special Studies

Study Title Year Objective
1. Algae Dynamics and Dissolved Oxygen Depletion Study 2015 To better understand the cause and effects of excessive algal blooms on bryophytes in the Upper Spring Run and Landa Lake sections of the Comal River. Final report completed (BIO-WEST, Center for Reservoir and Aquatic Systems Research, and Aqua Strategies, 2015).
2. Preliminary Tests of an Aeration System in Landa Lake 2015 The final report Supplemental Dissolved Oxygen Evaluation in Landa Lake (BIO-WEST, 2015).
Suggested Citation:"5 Applied Research Program." National Academies of Sciences, Engineering, and Medicine. 2017. Review of the Edwards Aquifer Habitat Conservation Plan: Report 2. Washington, DC: The National Academies Press. doi: 10.17226/23685.
×
Study Title Year Objective
3. Suspended Sediment impacts on TWR (and Other SAV) and Macroinvertebrates 2015 To evaluate the timing and duration of suspended sediments in the San Marcos River, to evaluate suspended sediment impact on aquatic plant communities and on the aquatic macroinvertebrate community, and to produce information that will be useful for any eventual TWR model. Final report completed (Texas State University, 2016).
4. Database Creation and Management 2016 Database creation and management, including compiling and formatting data, creating standard data templates, and normalizing data for all EAHCP applied research conducted to date. They are using an off-the-shelf product: Aquatic Infomatics – Aquarius Samples

EAHCP = Edwards Aquifer Habitat Conservation Plan

TWR = Texas wild rice

Ludwigia repens Competition Study

Submersed aquatic vegetation (SAV) in the San Marcos and Comal systems varies in terms of morphology, life history, and reproduction, and different species have been associated with varying densities of fountain darters. For this reason, a primary goal for the HCP has been seeking to establish or maintain vegetation that optimizes protected species’ populations. For this study, a plant targeted for restoration—Ludwigia repens—was evaluated in terms of competition with non-native species. Ludwigia is associated with higher densities of fountain darter than two important non-native plants; Hygrophila polysperma (found in both river systems) and Hydrilla verticillata (identified only in the San Marcos). The objective of this project was to determine whether competition between Ludwigia and each of the non-native species was of importance in the early establishment period when new sprigs are planted in a cleared location. A second phase of the study continued to evaluate whether the plants were more or less vulnerable to competition after a period of established growth in the absence of the competing species.

While an earlier study had carried out initial, similar investigations in buckets (Doyle et al. 2003), the methods in this study better reflected the river systems by carrying out experiments under ambient conditions. Multiple locations were selected for the study to provide experimental replication. These locations represented different environmental conditions,

Suggested Citation:"5 Applied Research Program." National Academies of Sciences, Engineering, and Medicine. 2017. Review of the Edwards Aquifer Habitat Conservation Plan: Report 2. Washington, DC: The National Academies Press. doi: 10.17226/23685.
×

such as high or low light and variable flow. Plants were grown in pots placed in the river and included control conditions for each species in addition to pots containing competing species with Ludwigia. The final report for this study provides greater details on the experimental design (Center for Reservoir and Aquatic Systems Research and BIO-WEST, Inc., 2015). Environmental conditions including depth, velocity, temperature, dissolved oxygen, pH, and photosynthetically active radiation were monitored along with response variables of maximum stem length, stem counts, and measurements of above- and below-ground biomass.

Across the experimental locations in pots without competition, Ludwigia exhibited strong growth, although Hygrophila and Hydrilla had the capacity to grow longer stems under some conditions. For the Hygrophila competition experiments in the early establishment phase of colonization, Ludwigia appeared capable of robust growth with only one site where competition was significant. It is possible that light availability is a key factor as the highest growth for Ludwigia appeared under high light conditions. The study’s authors mention that the experimental locations generally had higher light conditions, so this leaves open a question as to whether the Hygrophila will have a competitive advantage under low light conditions. Contrasting with results from the earlier Doyle et al. (2003) study, the competitive experiments evaluating the impact of invasion by Hygrophila on established plants indicated that Ludwigia is not negatively impacted. Instead, Hygrophila appears to be negatively impacted by Ludwigia. These results support renewed interest in Ludwigia as a species for restoration, especially in areas where Hygrophila is of concern. Insuring that this competitive advantage is communicated to the SAV modelers and incorporated into their efforts is also recommended. In fact, this study should be highlighted as one where experimental results may be directly useful to the ecological modelers.

The Hydrilla experiments seem to have suffered from poor overall growth of this species, with declining biomass and evidence of mortality through the experiment, making the results difficult to interpret. The final report provides results indicating negative effects of Hydrilla on Ludwigia in this context, but it is not clear if the mortality events could impact Ludwigia grown in the same pots. Additional consideration of the interactions between Hydrilla and Ludwigia is needed before conclusions are made or further application of this research occurs.

A primary conclusion of this study is that Ludwigia can be planted successfully into unvegetated areas and is a good candidate for restoration. The results support this conclusion and the low competition with Hygrophila is particularly encouraging. Additional interpretation of the effect of experimental replicate location on growth suggest that environmental conditions are likely important factors to consider for restoration efforts, and may merit additional garden-style experiments investigating the

Suggested Citation:"5 Applied Research Program." National Academies of Sciences, Engineering, and Medicine. 2017. Review of the Edwards Aquifer Habitat Conservation Plan: Report 2. Washington, DC: The National Academies Press. doi: 10.17226/23685.
×

relationship between light and flow on Ludwigia growth and colonization. The suggestions for further study listed at the conclusion of the final report are reasonable and would add to the knowledge available for improving restoration successes for this species. Given the potential for Ludwigia to outcompete at least one of the non-native species, serious consideration should be given to using this species in the San Marcos system. Although there has been mixed success with restoration of Ludwigia in the San Marcos system in the past, the results of this study suggest that this SAV species may be particularly valuable because it sustains both high fountain darter densities and a competitive advantage against non-native species that have been targeted for removal.

Comal Springs Riffle Beetle Population Occupancy Modeling

The objective of this study (Zara Environmental, 2015) was to develop a system-wide estimate of the population size of Heterelmis comalensis that would serve as a baseline population estimate for this endangered species. The study took a random survey site selection approach of 95 spring outlets for monitoring H. comalensis populations in October 2014, a period of extremely low flow. This approach identified all spring outlets in the entire system (300 sites) and then randomly selected a set for monitoring, avoiding issues of biased estimates related to site selection based on pre-existing knowledge about the potential state of occupancy. Monitoring relied on the established cotton-cloth lure approach from previous surveys. Each sampling event was separated by 72 hours to maintain independence among sampling periods. Using occupancy modeling approaches, significant combinations of covariates were used as predictors of population occupancy and then a N-mixture repeated count model was used to make system-wide estimates of beetle population abundance based on available habitat.

The beetle was detected in 22 of 95 spring outlets over three sampling time periods, with 101 adults and 36 larvae counted. Using the two modeling approaches, an estimate of a total of 741 beetles (90% CI 471-1284) was made for the entire system at the time of the survey. This is a very low population estimate for the entire Comal Springs system.

This project was a substantial effort, and it greatly expanded earlier modeling efforts that simply used wetted area to estimate riffle beetle population abundance in the Comal system. However, because the sampling period was during an extremely low flow period, an unknown number of additional spring outlets that had been previously identified by Norris and Gibson (2013) were either not flowing or had very reduced flow that prevented monitoring. When these springs are not flowing it is impossible to estimate beetle abundance, and there are no definitive data to suggest that when the springs dry up the beetles survive in the springs. Earlier accounts

Suggested Citation:"5 Applied Research Program." National Academies of Sciences, Engineering, and Medicine. 2017. Review of the Edwards Aquifer Habitat Conservation Plan: Report 2. Washington, DC: The National Academies Press. doi: 10.17226/23685.
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suggest that the beetles move deeper into the springs via wetted interstitial spaces; however, it is unknown whether beetles found in springs that begin to flow after a dry period are from the spring itself or have emigrated from other sources in the system. The dry springs of previously known populations could be one reason for the very low population estimate determined in the report. Additionally, this was not a mark and recapture study, and so it is unknown if the beetles counted during subsequent sampling events were repeat counts, new counts, or a mixture of recounts and new counts. Thus, while this study was an effort at a snap-shot estimate of the H. comalensis population in Comal Springs, the survey provides no information on the life history characteristics (e.g., synchrony, number of generations, growth rates) and how the population abundance changes over time and in response to flow: this is a critical aspect of the HCP. Importantly, because the cotton-lure method of sampling has not been calibrated to estimate densities, the estimates presented here may not accurately reflect true population densities at the surveyed spring outlets. This could be another explanation for the overall detection rate of only 51 percent in occupied sites. New and innovative Applied Research projects should determine a reliable and defendable collection method for H. comalensis. Furthermore, a validation study that encompasses repeated sampling from the same and new spring outlets to account for potential life history and flow effects on the population estimates is highly recommended.

This occupancy model was the most directed research effort to date for estimating the population abundance of the CSRB in the entire Comal Springs system. However, as indicated by the authors, there were several serious flaws to the study design, including the sampling approach. The occupancy report at best provides very limited information on the variation in CSRB among springs and seeps and, at worst, suggests that the CSRB populations are incredibly low and perhaps not being managed appropriately by the HCP. Fortunately, the issue of an appropriate sampling approach has become a focus of a 2016 Applied Research project (as discussed above).

Comal Springs Riffle Beetle Habitat Connectivity Study

The goals of this Applied Research project were threefold: (1) to examine water quality conditions and survival of the CSRB at two experimental facilities (USFWS San Marcos Aquatic Resource Center [SMARC] and the Texas State University Freeman Aquatic Building [FAB]); (2) to evaluate the potential of riffle beetle surrogate species; and (3) to test and describe components of upwelling and lateral habitat connectivity for the CSRB. As part of the last goal, the importance of organic material to CSRB behavior and movement was evaluated in laboratory experiments, as well as a field

Suggested Citation:"5 Applied Research Program." National Academies of Sciences, Engineering, and Medicine. 2017. Review of the Edwards Aquifer Habitat Conservation Plan: Report 2. Washington, DC: The National Academies Press. doi: 10.17226/23685.
×

study using stable isotopes to determine CSRB food resources and to test two alternative sampling approaches to the cotton lure.

This project identified several important aspects of the CSRB biology, namely that surrogate species are unlikely to be useful for understanding the CSRB environmental tolerances and habitat occupancy, that passive sampling using pit traps and pumping are not viable alternative sampling strategies, and that both leaf and wood organic matter is important to the habitat and biology of the CSRB. The latter finding suggests an alternative sampling approach as well as identifying important habitat characteristics that could be used in future modeling efforts. That is, if terrestrial-derived organic materials are important to the CSRB as a food source and as habitat, then the riparian plant community could play a role in affecting CSRB habitat and population structure. Additional studies will be required to vigorously test these potential impacts to modeling CSRB populations; it is evident from the 2016 Applied Research projects that this study has provided a foundation for future studies. The Committee commends this effort to fund new projects to build upon these informative results.

An interesting finding from this study was that the Pecks’s Cave amphipod (Stygobromus pecki) could be a predator of other invertebrates in these interstitial habitats. If this finding can be confirmed and S. pecki is determined to be a predator (or facultative predator) of the CSRB, new studies on the importance of predation on CSRB populations would be warranted.

The first goal of the project highlighted issues of using laboratory experiments to make broad inferences about field conditions. While the few water quality variables that were measured (temperature, conductivity, dissolved oxygen) at each facility were the same, there was nearly 100 percent mortality of the CSRB at the FAB facility, for reasons that remain unknown. This finding reveals that there are significant dimensions of CSRB biology that are not yet understood that may be critical to the survivorship of this endangered species. This finding also suggests that past, current, and future experiments using these laboratory chambers may not represent how the species responds to environmental change in nature, creating a degree of uncertainty as to how these data can be used in monitoring and modeling the CSRB. The Committee recommends that additional studies be conducted to identify the source of mortality at the FAB facility, since doing so would likely reveal important factors that are necessary for structuring and maintaining CSRB populations. A second recommendation would be to validate key laboratory experiments like the one in this connectivity study using creative field studies where variables can be manipulated.

Suggested Citation:"5 Applied Research Program." National Academies of Sciences, Engineering, and Medicine. 2017. Review of the Edwards Aquifer Habitat Conservation Plan: Report 2. Washington, DC: The National Academies Press. doi: 10.17226/23685.
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Algae and Dissolved Oxygen Dynamics of Landa Lake and the Upper Spring Run

The goal of this Applied Research project was to characterize the composition, spatial and temporal distribution, and ecological consequences of benthic algae turf mats and floating vegetation mats in Landa Lake and Upper Spring Run (BIO-WEST, Center for Reservoir and Aquatic Systems Research, and Aqua Strategies, 2015). The impetus for this study was the observation that the turf and floating vegetation mats were abundant in Landa Lake and Upper Spring Run during 2013 and 2014 (which were years of low flow) and there was concern that these mats could affect the distribution and abundance of fountain darter habitat through the mats’ effects on SAV and dissolved oxygen concentration.

The development of benthic algal mats was monitored during the summer of 2015 in a series of permanent transects established throughout Landa Lake and Upper Spring. In addition, an experiment to assess the effects of benthic algal mats on other aquatic vegetation was attempted by planting Ludwigia and bryophytes in areas with and without benthic algal mats. To assess the effects of floating vegetation mats on dissolved oxygen concentrations, miniDOT oxygen sensors were placed in areas with and without floating mats and at different depths in the water column. Finally, a model was developed to assess the relative importance of reaeration, water column algae and macrophytes on dissolved oxygen concentration and dynamics.

Due to heavy spring rain events, the summer of 2015 had slightly larger than average flows. Perhaps because of the higher flow rates, both the benthic turf mats and the floating vegetation were not as prominent as in the prior two years of low flow. Therefore, although the study was originally planned to assess the development and effects of these mats during low flow years, the study actually characterized mat development during normal flow conditions. Nevertheless, the study provided useful baseline information on the relative importance and ecological effects of benthic and floating mats.

Benthic algal mats, which were largely made up of Spirogyra and Cladophora, rarely co-occurred with bryophyte mats. The transplant experiment to test whether the benthic mats caused reductions in bryophytes and other macrophytes was not definitive due to the difficulty of establishing an area of persistent benthic algal mat occurrence, but suggested there might be a negative effect between benthic algal mat abundance on other aquatic vegetation. The floating vegetation mats appeared to have only minor effects on dissolved oxygen, but the modeling results suggested that if the floating mats cover more than 25 percent of the lake surface area the mats could reduce dissolved oxygen in the water column by reducing

Suggested Citation:"5 Applied Research Program." National Academies of Sciences, Engineering, and Medicine. 2017. Review of the Edwards Aquifer Habitat Conservation Plan: Report 2. Washington, DC: The National Academies Press. doi: 10.17226/23685.
×

reaeration rates. Not surprisingly, diurnal dissolved oxygen concentrations at the benthic surface had greater amplitude than those higher in the water column. The only evidence of minimum dissolved oxygen levels below 4 mg/L were in stagnant areas and within bryophyte mats, which fountain darters could likely avoid.

In general this study was well conceived, but the higher than average flows limited its usefulness to understand how benthic algal and floating vegetation/debris mats influence fountain darter habitat through effects on macrophytes and dissolved oxygen during low flow conditions. MiniDOTs oxygen sensors give great flexibility in monitoring spatial patterns in dissolved oxygen concentrations and should be integrated into the water quality and biological monitoring plans.

Dissolved Oxygen Management in Landa Lake

Ensuring adequate levels of dissolved oxygen in habitats important to fountain darter and other species of concern is important to meeting the goals of the HCP. Because sonde measurements of dissolved oxygen in Landa Lake have occasionally showed dissolved oxygen below the somewhat arbitrary regulatory threshold of 4 mg/L, a mitigation measure of aerating Landa Lake to increase dissolved oxygen concentrations and/or removing floating vegetation/debris mats is being considered.

Preliminary tests of an aeration system occurred in the summer and fall of 2015. The report Supplemental Dissolved Oxygen Evaluation in Landa Lake (BIO-WEST, 2015) was produced to report on aeration tests conducted in September 2015. As described above, an additional study on the effects of floating vegetation/debris mats on dissolved oxygen concentrations in Landa Lake was completed in 2015 as part of the Applied Research Program.

In September 2015 an overnight aeration test was done in Bleiders Creek, up flow from Landa Lake. This area was selected because relatively stagnant, low-flow conditions were present, mimicking the conditions that might occur in areas of Landa Lake during low spring flow conditions. Two aeration diffusers were operated over the course of one night, and numerous dissolved oxygen measurements were made using handheld sensors and sondes at multiple points surrounding the diffusers. Results showed relatively little effect of the diffusers on dissolved oxygen concentrations, raising dissolved oxygen concentrations by approximately 0.5 mg/L. These results were then used in model calculations of the potential effectiveness of aeration on the larger Landa Lake. Results of these calculations showed that it would take about 160 diffusers spaced 30 feet apart to increase the ambient dissolved oxygen concentration by 1 mg/L. The limited effectiveness of the diffusers is largely due to the shallow depth of the lake.

Suggested Citation:"5 Applied Research Program." National Academies of Sciences, Engineering, and Medicine. 2017. Review of the Edwards Aquifer Habitat Conservation Plan: Report 2. Washington, DC: The National Academies Press. doi: 10.17226/23685.
×

The EAA deployed multiple miniDOT oxygen sensors in Landa Lake and Upper Spring Run during the summer of 2015 to monitor spatial and temporal changes in dissolved oxygen concentrations. This is a relatively low cost and effective way to monitor oxygen levels, and this monitoring should be continued as part of a routine integrated water quality and biological monitoring program. The EAA can use the knowledge gained during 2015 to identify the key locations in Landa Lake that will serve as indicators for the entire lake system.

Results of the 2015 and previous studies suggest that low concentrations of dissolved oxygen are not a widespread problem in Landa Lake and Upper Spring Run except for a few isolated locations during stagnant periods of low flow. It is likely that fountain darters and other species of concern can move to avoid these areas of low oxygen concentration. Furthermore, the 2015 study on effects of aeration on dissolved oxygen concentrations (BIO-WEST, 2015) showed that aeration had only minimal effects, raising dissolved oxygen concentrations less than 1 mg/L. Therefore, the Committee recommends that aeration not be used routinely as a mitigation measure. In an emergency situation, if dangerously low levels of dissolved oxygen persist even in the deepest areas of Landa Lake, then using aerators in a small area of Landa Lake to create a small refuge of higher dissolved oxygen water should be considered. If floating mats cover more than 25 percent of the surface of Landa Lake and dissolved oxygen concentrations decrease, then manual breaking up and removal of the floating mats should be considered as a mitigation measure. The Committee further recommends that monitoring the dissolved oxygen concentrations using the miniDOTs in selected areas of Landa Lake and Upper Spring Run be incorporated into an integrated water quality and biological monitoring program.

FUTURE OF THE APPLIED RESEARCH PROGRAM

The Applied Research Work Group was formed in 2015 subsequent to the release of NRC (2015). The charge to this work group was two-fold: (1) determine if additional Applied Research studies are needed, and (2) develop a research plan that prioritizes the numerous studies that have been recommended by the National Academies’ Committee, the Science Committee, the Implementing Committee, and independent subject matter experts.

One of the activities of the Applied Research Work Group was to identify categories of research. This was accomplished and led to the following five categories:

  1. Conservation Measures: Assessing the holistic practical benefits of HCP conservation measures to the species, and the effectiveness
Suggested Citation:"5 Applied Research Program." National Academies of Sciences, Engineering, and Medicine. 2017. Review of the Edwards Aquifer Habitat Conservation Plan: Report 2. Washington, DC: The National Academies Press. doi: 10.17226/23685.
×
  1. of the conservation measures in achieving biological objectives and goals.

  2. Standard Sampling Methods: Establishing reliable sampling methods for the species to ensure they permit evaluation of trends over time, including standardization as an important goal; and that they are consistent with biological objectives and goals.
  3. Habitat Quality, Quantity, and Requirements: Evaluating the habitat requirements of the species, including the assessment of whether habitat is of sufficient quality and quantity, and validating HCP assumptions related to habitat, consistent with biological objectives and goals.
  4. System Memory/Disturbance Ecology: Measuring the effects of disturbance (e.g., drought, scouring floods, etc.) on the system, and the response (i.e., resilience and/or resistance) of the system post-disturbance as it relates to biological objectives and goals.
  5. Data: Data management considerations relevant to existing and future data to be collected, as well as applications for analysis of existing data relevant to biological objectives and goals.

The future projects that the Applied Research Work Group decided would fill out the remainder of the program’s time are listed in Table 5-5.

In general, the Committee is supportive of the Work Group’s efforts to identify priority areas for the Applied Research Program and to plan projects through 2019. The 2017 project to establish better relationships between the fountain darter and the different species and coverages of SAV (including Ludwigia) in both systems is critically important. This will be essential information to have when removing non-native species to insure that take is minimized. Research to better understand the life history of listed species and identifying effective sampling techniques rightfully deserves high priority. This knowledge underpins efforts to assess the ecological status and trends of the Comal Springs riffle beetle, Comal Springs dryopid beetle, and Peck’s Cave amphipod. This research is needed but will be difficult and may require multiple years to be successful. The EAA should be prepared to invest in additional research projects in this area that span multiple years, if necessary.

Starting in 2018, the EAA appears to be using the Applied Research Program as a mechanism to assess the effectiveness of minimization and mitigation measures such as removal of exotic species, SAV restoration, and sediment control. While monitoring the effectiveness of these measures is critical, it is not clear that this monitoring should be part of the Applied Research Program. Ecological effects resulting from these minimization and mitigation measures are likely to play out over the long term rather than in a single year. Therefore, monitoring to assess the effectiveness of

Suggested Citation:"5 Applied Research Program." National Academies of Sciences, Engineering, and Medicine. 2017. Review of the Edwards Aquifer Habitat Conservation Plan: Report 2. Washington, DC: The National Academies Press. doi: 10.17226/23685.
×

TABLE 5-5 Projects for the Applied Research Program 2017-2019

Project Title Year Committee Comments
Continuation of CSRB life history study 2017 Continuation of the study begun in 2016.
SAV as FD habitat (shelter, prey habitat) 2017 This is a key metric worthy of continued efforts. Quantifying the relationship between a given SAV species and coverage with FD will serve to inform M&M measures and will help in estimates of FD density based on vegetative cover.
Effects of sedimentation on SAV, FD and CSRB* 2017 The RFP focuses specifically on the CSRB.
Comal Springs dryopid beetle quantitative sampling techniques 2017 Previously unsampled organism.
Statistical analysis of data × 2* 2017 Two projects will develop additional study questions to further explore biological objectives and statistically analyze existing EAHCP data concerning system memory/ disturbance ecology and species-specific questions.
Peck’s Cave amphipod quantitative sampling techniques 2018 Previously unsampled organism.
Evaluate success of SAV restoration and TWR enhancement (coincides with 5-yr SAV mapping) 2018 Performance monitoring of an M&M. Future efforts need to also be mindful of evaluating success as normalized to effort and potential available habitat.
Confirm species-specific Tables 4-1, 4-21 in the HCP 2018 Performance monitoring of an M&M. Tables 4-1 and 4-21 list the numbers of FD found in an area of SAV, for Comal and San Marcos, respectively. Could be similar to 2017 study.
Evaluate success of flow-split management 2018 Performance monitoring of an M&M
Contingency slot 2018
Evaluate success of removal of invasive animal species and reduction of introduction 2019 Performance monitoring of an M&M
Evaluate success of Sessom Creek sand bar removal and sediment removal efforts 2019 Performance monitoring of an M&M
Contingency slot 2019

*The Committee’s reading of these RFPs finds it will be very hard for those unfamiliar with the system to respond to this RFP, for a number of reasons.

SOURCE: EAHCP ARWG (2015).

Suggested Citation:"5 Applied Research Program." National Academies of Sciences, Engineering, and Medicine. 2017. Review of the Edwards Aquifer Habitat Conservation Plan: Report 2. Washington, DC: The National Academies Press. doi: 10.17226/23685.
×

the minimization and mitigation measures needs to be ongoing through the lifetime of the HCP. As discussed in Chapter 4, the Committee recommends that such monitoring should be integrated into the biological and water quality monitoring programs rather than done in one-year studies through the Applied Research Program.

CONCLUSIONS AND RECOMMENDATIONS

The Committee applauds the changes made by the EAA regarding the procedures to identify, solicit, and review the projects in the Applied Research Program. The program as modified should be continued and could be expanded to facilitate additional multi-year studies in the future. It has the potential to provide data and understanding of basic processes that will help inform implementation of the mitigation and minimization measures as well as the development of the ecological models. To encourage more involvement of more outside experts, the EAA should look for ways to ease barriers to participation in the Applied Research Program.

The Committee is supportive of EAA’s attempts to develop an effective database management system that will provide data storage, curation, and access into the future. Resources for ongoing data management activities will need to be allocated throughout the lifetime of the HCP.

Monitoring the effectiveness of minimization and mitigation measures such as removal of exotic species, sediment control, and riparian conservation should be done through integration into the existing biological and water quality monitoring programs, rather than through one-off studies conducted through the Applied Research Program.

Modeling efforts should become more integral to consideration of future Applied Research projects. Projects in the Applied Research program can provide data and information to help design model scenarios, to improve parameter estimation and model formulation, and to enable model calibration and validation. For example, the NRC (2015) and NASEM (2016) recommendation that nutrients be considered in the ecological submodel of SAV would be easier to implement with nutrient data collection and more explicit consideration of nutrients in Applied Research projects related to SAV.

REFERENCES

BIO-WEST. 2014a. Fountain Darter Movement under Low flow Conditions in the Comal Springs/River Ecosystem. Final Report. October 30, 2014.

BIO-WEST. 2014b. Effect of Low-Flow on Riffle Beetle Survival in Laboratory Conditions. Final Report. November 14, 2014.

BIO-WEST. 2015. Final report. Supplemental Dissolved Oxygen Evaluation in Landa Lake.

Suggested Citation:"5 Applied Research Program." National Academies of Sciences, Engineering, and Medicine. 2017. Review of the Edwards Aquifer Habitat Conservation Plan: Report 2. Washington, DC: The National Academies Press. doi: 10.17226/23685.
×

BIO-WEST. 2016. Evaluation of the Life History of the Comal Springs Riffle Beetle. EAHCP Proposal NO. 147-15-HCP.

BIO-WEST and Baylor University. 2013. Edwards Aquifer Habitat Conservation Plan 2013 Applied Research. Final Version. November 2013.

BIO-WEST and Texas State. 2015. Comal Springs Riffle Beetle Habitat Connectivity Study. December 14, 2015.

BIO-WEST, Center for Reservoir and Aquatic Systems Research, and Aqua Strategies. 2015. Algae and Dissolved Oxygen Dynamics of Landa Lake and the Upper Spring Run.

Center for Reservoir and Aquatic Systems Research and BIO-WEST, Inc. 2015. Final Report for Ludwigia repens Competition Study. Edwards Aquifer Authority Contract #14-727L

Doyle, R. D., M. D. Francis, and R. M. Smart. 2003. Interference competition between Ludwigia repens and Hygrophila polysperma: two morphologically similar aquatic plant species. Aquatic Botany 77:223-234.

Doyle, R., S. Hester, and C. Williams. 2014. Edwards Aquifer Authority 2014 Ecomodeling: Vegetation Percent Cover to Biomass. Report of Research Activities. November 25, 2014.

EAA. 2015. Applied Research Selection Process.

EAHCP ARWG. 2015. Report of the 2015 Applied Research Work Group. October 16, 2015. Edwards Aquifer Habitat Conservation Plan Applied Research Work Group.

Gibson, R., C. Norris, and P. Diaz. 2013. Determination of Limitations of Comal Springs Riffle Beetle Plastron Use during Low-Flow Study. Proposal #124-13-HCP. August 28, 2013.

NASEM (The National Academies of Sciences, Engineering, and Medicine). 2016. Evaluation of the Predictive Ecological Model for the Edwards Aquifer Habitat Conservation Plan: An Interim Report as Part of Phase 2. Washington, DC: The National Academies Press.

NRC (National Research Council). 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press.

Norris, C., and R. Gibson. 2013. Distribution, Abundance and Characterization of Freshwater Springs Forming the Comal Springs System, New Braunfels, Texas. Report prepared for Texas Parks and Wildlife Department.

Nowlin, W., and D. Hahn. 2015. Evaluation of the Trophic Status and Functional Feeding Group Status of the Comal Springs Riffle Beetle. EAHCP Proposal NO. 148-15-HCP.

Nowlin, W., and B. Schwartz. 2015. Evaluation of Long-Term Elevated Temperature and Low Dissolved Oxygen Tolerances of the Comal Springs Riffle Beetle. EAHCP Proposal NO. 146-15-HCP.

Texas State University. 2016. Suspended Sediment Impacts on Texas Wild Rice and other Aquatic Plant Growth Characteristics and Aquatic Macroinvertebrates. September 2016.

Texas State University and BIO-WEST. 2014a. Effects of Low Flow on Fountain Darter Reproductive Effort. Final Report. October 2014.

Texas State University and BIO-WEST. 2014b. Effects of Predation on Fountain Darters Study. Final Report. October 2014.

Zara Environmental. 2015. Comal Springs Riffle Beetle Occupancy Modeling and Population Estimate within the Comal Springs System, New Braunfels, Texas. Prepared by Zara Environmental LLC and submitted on 23 March 2015.

Suggested Citation:"5 Applied Research Program." National Academies of Sciences, Engineering, and Medicine. 2017. Review of the Edwards Aquifer Habitat Conservation Plan: Report 2. Washington, DC: The National Academies Press. doi: 10.17226/23685.
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The Edwards Aquifer in south-central Texas is the primary source of water for one of the fastest growing cities in the United States, San Antonio, and it also supplies irrigation water to thousands of farmers and livestock operators. It is also is the source water for several springs and rivers, including the two largest freshwater springs in Texas that form the San Marcos and Comal Rivers. The unique habitat afforded by these spring-fed rivers has led to the development of species that are found in no other locations on Earth. Due to the potential for variations in spring flow caused by both human and natural causes, these species are continuously at risk and have been recognized as endangered under the federal Endangered Species Act(ESA). In an effort to manage the river systems and the aquifer that controls them, the Edwards Aquifer Authority and stakeholders have developed a Habitat Conservation Plan (HCP). The HCP seeks to effectively manage the river-aquifer system to ensure the viability of the ESA-listed species in the face of drought, population growth, and other threats to the aquifer. The National Research Council was asked to assist in this process by reviewing the activities around implementing the HCP.

Review of the Edwards Aquifer Habitat Conservation Plan: Report 2 reviews the progress in implementing the recommendations from the Committee's first report, seeking to clarify and provide additional support for implementation efforts where appropriate. The current report also reviews selected Applied Research projects and minimization and mitigation measures to help ensure their effectiveness in benefiting the listed species.

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