Health of Walker River and Lake 
This project will evaluate and establish a benchmark for the environmental and ecological health of Walker Lake and Walker River. Decision tools will be developed to analyze the efficacy of different water acquisitions for improving future ecological integrity of Walker Lake and Walker River.
From DRI: Don Sada (PI), Division of Hydrologic Sciences (DHS); Kumud Acharya (Co-PI), DHS; Chris Fritsen (Co-PI), Division of Earth and Ecosystem Sciences (DEES); Alan Heyvaert (Co-PI), DHS; Ron Hershey (Co-PI), DHS; Duane Moser (Co-PI), DHS; Saxon Sharpe (Co-PI), DEES; and Mark Stone (Co-PI), DHS
From UNR:Sudeep Chandra, (PI), Department of Natural Resources and Environmental Science (NRES); Peter Weisberg (Co-PI), NRES
Continued processing samples for water quality, microbiology, inverterbate, fish, and periphyton work. The cultures obtained from Walker Lake have yielded numerous alkaliphilic (or at the very least alkatolerant) isolates capable of growth both aerobically and anaerobically on defined sulfur media and aerobically on heterotrophic media.
Analysis of phosphorous from the Sept '07 macro-invertebrate samples from Walker River is a quarter complete with full completion expected shortly. C:N stoichiometric analysis of the macro-invertebrates is fifty percent complete, with completion expected shortly. The set of zooplankton collected at Walker Lake on December 5 have not been analyzed. Techniques for the measurement on C, N, and P are still being tested in order to segregate the two dominant species of zooplankton. Only the copepod species have been successfully prepared for phosphorus analysis. No other samples have been received after December '07.
Highlight of the month
Microorganisms which produce toxic hydrogen sulfide from elemental sulfur were found to be abundant in Walker Lake. This result suggests a previously unappreciated role for sulfur cycle intermediates as drivers of water column carbon and energy flow
Walker Lake sampling for water quality occurred on February 18, 2008. Continued processing samples for water quality, microbiology, invertebrate, fish, and periphyton work.
DNA sequencing of select microbial isolates from the Walker Lake water column suggests a diverse community capable of surviving in the alkaline, relatively saline waters of Walker Lake. Additionally, a complimentary cell counting method (flow cytometry) confirmed earlier microscopic estimates of microbial cell density.
The cultures obtained from Walker Lake has yielded numerous alkaliphilic (or at the very least, alkatolerant) isolates capable of growth both aerobically and anaerobically on defined sulfur media and aerobically on heterotrophic media.
Analysis of phosphorous on the September 2007 macro-invertebrate samples from Walker River is now complete. C:N stoichiometric analysis of the macro-invertebrates is fifty percent complete, with completion expected shortly. The set of zooplankton collected at Walker Lake on December 5 are also being analyzed. The two dominant species of zooplankton have been separated for analysis. Only the copepod species has been analyzed so far. No other samples have been received since December 2007.
Work continues on development of the ecological model. The lake hydrodynamic model has been parameterized through December 2007 and will be calibrated using the first two lake sampling events later this month. Development of the ecological component continues to progress as lake limnological data continues to become available. The ecological component will be fully parameterized by the end of April with calibration beginning thereafter.
- Walker Lake and River food web study is progressing well.
- Microbial isolates from Walker Lake were determined by DNA sequence analysis to be most closely related to microbes from other alkaline and/or saline environments.
The carbon to nitrogen analysis of invertebrates used as an indicator for aquatic health has been completed for the river samplings from 2007. We are actively working to finish the analysis on samples from 2008. The next steps are to analyze for other important nutrients such as phosphorus.
A preliminary analysis of lake energetic contributions to the fishery has been completed. Similar to the samples collected with the Nevada Department of Wildlife in 2003, the data from 2007 indicate that most of the fishery is support by bottom production.
Using molecular techniques, DNA was extracted and purified from Walker Lake water samples. Careful analysis of individual DNA sequences isolated from these samples confirmed the presence of diverse microbial communities within the lake, with different groups of microbes present at different depths. Given the alkaline conditions of the lake (pH 9.4), it can be assumed that identified sequences are from alkaliphilic/alkalitolerant microbes and may be representative of new species.
One of our research staff was highlighted on the UNR website for his tireless efforts to sample Walker Lake and the river.
Isolates selected for sequencing were most closely related to other microbes found in other alkaline and/or saline environment.
The beta version of the database, which includes compiling information from historic studies and aspects of its functionality, continues to be modified based on suggestions and feedback from collaborators. We continue to obtain and add recent monitoring data collected by principal investigators at Walker Lake. Walker River data is in review for potential addition to the database.
At this time, we are working with Dr. Mark Stone to review monitoring data needs for his ecosystem model and sensitivity analysis. Several meetings were conducted during the last week of April to address these issues. Once these tasks are completed we will begin drafting preliminary recommendations for long-term monitoring at Walker Lake.
Walker Lake food web studies are progressing during laboratory work.
The spring 2008 Walker River sampling of fish, periphyton, water chemistry, benthic macroinvertebrates, and physical habitat was conducted during the week of April 14th. In the past month, we continued to process macroinvertebrate, periphyton, and fish stomach samples collected in August and September, 2007.
River and lake ecosystem stoichiometry. The detritus and invertebrate samples collected in April 2008 are currently being analyzed for C:H:N (carbon, hydrogen, and nitrogen ratios) and phosphorus. For phosphorus analysis, the preparation is halfway completed and chemical analysis will proceed shortly. For C:H:N analysis, a quarter of the samples have already been prepared and analyzed. All the image cataloging is complete. We have not received any new Walker River samples since April 2008 nor any Walker Lake samples since December 2007.
Phytoplankton and periphyton.
Figure 1. Image of Nodularia sp. from Walker lake, collecteed during cyanobacterial bloom, may 1, 2008. Image taken with DIC (A) and Epifluorescence (B) by Clint Davis.
A sampling trip to Walker Lake was completed from 5/1 to 5/2 in response to the large cyanobacterial bloom observed by C. Fritsen on 4/25. A profile from station WL3 was collected for water quality and biomass analysis. YSI sonde depth profiles at the beginning and end of a diurnal study were completed. Various measurements were taken over a 24 hour period at WL3 at ~5 meter depth using a YSI 6600V2 sonde. Temp., Sp. Cond., DO, and pH/ORP were logged overnight near the Sportsman’s Beach dock using a YSI 600xlm.
Completed chlorophyll a and ash free dry mass analysis for all samples collected from the river to date. Continuation of microscopic analysis of samples from Walker Lake and River.
Sulfide production. The microbial community of two distinct depths in Walker Lake was examined using molecular cloning techniques. The depths examined represented two distinct lake habitats, namely an oxygenated, mixed surface sample (0m) and a remnant of the lake’s oxygen deprived bottom water (24m). It appeared that while numerous types of microbes were present in both samples, there were unique microbial populations at the individual depths. Because the seasonal mixing of the surface and bottom water occurred at the time of sampling, it is impossible to say whether the cosmopolitan species were naturally present throughout the lake, although the water sample collected from 24m was chemically distinct from the rest of the lake suggesting it had yet to mix.
Ecological model. The Walker Lake Ecological model is undergoing refinement as additional data becomes available from lake monitoring activities along with compilation of other data sources in the Walker Lake database. We are continuing to calibrate the hydrodynamic component of the model using recently acquired temperature data collected by Dr. Sudeep Chandra’s research team. Refinement of the ecological model will continue this month based on dissolved oxygen profiles, chlorophyll-a samples, and zooplankton data. We anticipate having the model fully calibrated by mid-July.
All about algae! There was a large blue green algae bloom in early May at Walker Lake. These blooms can cover the whole lake and last only for a short period of time. They are important since they can bring nitrogen, a limiting nutrient, to the lake. Our team led by Chris Fritsen and Sudeep Chandra responded quickly to study the impact of the bloom on the lake.
Microbes! Microbes! Microbes! The alkaline, moderately saline waters of Walker Lake appear to support populations of microbes specific to the chemically distinct regions of the lake.
Internal Salt Lake Conference in Salt Lake City, Utah! The fisheries and food web team presented some preliminary information collected from this project at the International Salt Lake Conference in Salt Lake City, Utah at the end of May. The presentation was well received by the community of international scientists.
Figure 2. Graph of Walker Lake site WL3 chlorophll a profiles for all SMEL sampling dates. Note the higher chlorophyll a concentrations encountered during the cyanobacterial blooms sampled May 1, 2008.
Data analysis and distribution to project database are ongoing, as is microscopic analysis of Walker River samples.
Microscopic analysis of Walker River samples is ongoing, and the project database is being populated with results from both lake and river analyses.
Based on biomass profiles and the particulate CN and P measures, estimates are being made of the masses of carbon, nitrogen and phosphorous in the lake at different times during the season that exist in phytoplankton and suspended particulate matter. Initial estimates have the nitrogen content in the lake's phytoplankton being on the order of 100 metric tons of N during peak bloom conditions. The accuracy and refinement of these estimates are being analyzed based on spatial uncertainties as well as more measures of the elemental composition of the lake's suspended particulates that are being generated in the lab.
There are no updates this month.
All invertebrates received from September ‘08 sampling have been catalogued using microscopic imagery. One third of all samples have been prepared for P and CHN experimental analysis, which is scheduled for completion in October. All previous samples which have been analyzed for P and CHN are now ready for trend analysis. Some trends with regard to seasonal and site-specific variations are evident.
The water column of Walker Lake was comprehensively sampled on September 18, 2008, by a team from DRI. On-site measurements of lake conditions (temperature, dissolved oxygen, etc.) indicated that the lake was under summer stratification (e.g., with a warm, mixed, oxygenated upper layer and a cold, oxygen-depleted, sulfidic lower layer). Guided by real-time water column data, samples were collected spanning the upper and lower regions as well as the transition zone between them. Collected samples are being analyzed for water, trace metal and dissolved gas chemistries. To assess its role in lake ecology and nutrient cycling, the microbial and microalgal community is being explored using a variety of traditional and molecular-based methods. Initial data DNA observations indicated that distinct microbial communities were characteristic of both upper and lower portions of the water column and that conditions in the lower portions were not suitable for fish.
The processing of benthic macroinvertebrate samples is proceeding as planned and will be completed in mid-November. Data analysis will begin immediately following processing. Analysis of biomass samples related to the project has been completed. Data analysis and distribution to project database are ongoing.
Details of the ecological model continue to be refined. This month we focused on nutrient components of the model, including a sensitivity analysis on the associated empirical parameters. The sensitivity analysis and associated adjustments to the parameters has improved agreement with measured data.
All currently available Walker Lake data have been entered into the database, which has been developed in support of the Walker Lake Ecological Model. An annotated bibliography on Walker Lake research and monitoring has been appended to the database. At this time, we continue working with Dr. Mark Stone to provide the monitoring data he needs. Based on the results and data evaluations of the ecosystem model and sensitivity analysis recommendations for monitoring longer-term lake water quality benefits and ecological effects from water rights acquisitions will be developed. Parameters that have proven particularly important to modeling results are given special attention. These evaluations and recommendations are summarized in the draft final report, which is being written as an integrated assessment of contemporary limnology in Walker Lake.
All currently available Walker Lake data have been entered into the database, which has been developed in support of the Walker Lake Ecological Model. An annotated bibliography on Walker Lake research and monitoring has been appended to the database. At this time, we continue working to provide the monitoring data needed for the ecosystem model and sensitivity analysis. Based on these modeling results and the data evaluations we are developing recommendations for monitoring longer-term lake water quality benefits and ecological effects from water rights acquisitions. Parameters that have proven particularly important to modeling results are being given special attention. These evaluations and recommendations have been summarized in the draft final report, which is to be completed next month as an integrated assessment of contemporary limnology in Walker Lake.
Samples obtained from Walker Lake on September 18, 2008, continue to be analyzed using culture-based and molecular methods. Enumeration analysis has further indicated a biomass increase within the anoxic portion of the lake including a community of pigmented photosynthetic organisms. On-site observations had previously suggested the presence of this community (filters obtained from anoxic depths were pink). DNA has successfully been obtained from all surveyed lake depths as well as sediments and molecular methods have been employed to amplify and purify this DNA for future molecular characterization and subsequent microbial community analyses.
An enumeration of autofluorescent (light emitting) cells in Walker Lake's water column confirms the presence of a substantial community of photosynthetic microbes present in the deep, anoxic portion of the lake.
Experimental analysis of P and CHN for all September 2008 invertebrates has been completed. Currently statistical analysis is underway for all data. Diatom mounts for river samples have also been completed, and microscopic analysis of 42 permanent and wet mounts, respectively, were completed. The processing of benthic macroinvertebrate samples is complete and data are being analyzed.