Pyramid Lake Research Articles

A 1200 year record of hydrologic variability in the Sierra Nevada from sediments in Walker Lake, Nevada

Measurements of the oxygen isotopic composition (δ18O) of the total inorganic carbon (TIC) fraction from cored sediments of Walker Lake, Nevada, were conducted at an average resolution of ∼3 years per sample over the last 1200 years. On the basis of radiocarbon analysis on the total organic carbon (TOC) fraction, a δ18O time series was created to reconstruct changes in hydrologic conditions back to AD 800. The timings of variations in the TIC δ18O record are generally consistent with the tree ring‐based Sacramento River flow record spanning AD 869 to 1977, indicating that Walker Lake δ18O contains information about past changes in at least regional hydrologic conditions. Comparison with the δ18O record from Pyramid Lake sediments indicates that both basins have recorded five century‐scale oscillations in regional hydrologic conditions since AD 800. Several of these changes in hydrologic conditions appear synchronous with century‐scale California Current water temperature changes derived from analysis of sediment cores from the Santa Barbara Basin also attesting to the regional extent of these climatic fluctuations. Nearly synchronous oscillations in the Sierra wetness and the California Current suggest that regional changes in atmospheric circulation may have played an important role in century‐scale climate variability over the last millennium.

EVALUATING THE BENEFITS OF IMPLEMENTING WATERSHED MANAGEMENT ALTERNATIVES VERSUS WWTP STRUCTURAL ALTERNATIVES: WATER QUALITY TRADING ON THE TRUCKEE RIVER

EVALUATING THE BENEFITS OF IMPLEMENTING WATERSHED MANAGEMENT ALTERNATIVES VERSUS WWTP STRUCTURAL ALTERNATIVES: WATER QUALITY TRADING ON THE TRUCKEE RIVERThe Truckee River system, a highly adjudicated system, is an ecologically unique water resource that originates at the outlet of Lake Tahoe, California, and terminates at Pyramid Lake, Nevada. The river system, with a number of competing uses including domestic and municipal water supply, irrigation, watering of livestock, recreation, propagation of wildlife and propagation of aquatic life, is a...Author(s)Seema ChavanElisa GarveySteve McDonaldMahmood AzadSourceProceedings of the Water Environment FederationSubjectSession 28: Trading: TMDLs and BeyondDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2004ISSN1938-6478SICI1938-6478(20040101)2004:14L.652;1-DOI10.2175/193864704784137332Volume / Issue2004 / 14Content sourceWEFTECFirst / last page(s)652 - 653Copyright2004Word count114

Reconstruction of Holocene Climate Change Using Multiproxy Analysis of Sediments from Pyramid Lake, British Columbia, Canada

Sediment cores from Pyramid Lake, an alpine tarn in the Cassiar Mountains of northwestern British Columbia, were investigated for changes in pollen, plant macrofossils, charcoal, and clastic sediment, which are used to infer changes in climate throughout the Holocene. Radiometric dating has yielded a chronology of high-magnitude rainstorm events and timberline migration for the Pyramid Lake basin since deglaciation at about 10600 B.P. Fifteen distinct minerogenic layers represent material delivered to the lake by runoff events. The frequency of minerogenic layer deposition, and by analogy of storms, has changed throughout the Holocene. Four large-magnitude rainstorm events occurred between 4400 and 5100 B.P. During this period white spruce (Picea cf. glauca) was likely present near the lake, although a closed forest stand did not develop around the lake at any point during the Holocene. The macrofossil record indicates that subalpine fir (Abies lasiocarpa) has been present, likely as krummholz, above the elevation of the lake since at least 9400 B.P. Pollen of western hemlock (Tsuga heterophylla) is represented from ca. 1500 B.P. to the present and may be a consequence of changes in regional air-mass circulation patterns.

Response of North American Great Basin Lakes to Dansgaard–Oeschger oscillations

We correlate oscillations in the hydrologic and/or cryologic balances of four Great Basin surface-water systems with Dansgaard–Oeschger ( D–O) events 2–12. This correlation is relatively strong at the location of the magnetic signature used to link the lake records, but becomes less well constrained with distance/time from the signature. Comparison of proxy glacial and hydrologic records from Owens and Pyramid lakes indicates that Sierran glacial advances occurred during times of relative dryness. If our hypothesized correlation between the lake-based records and the GISP2 δ 18O record is correct, it suggests that North Atlantic D–O stades were associated with relatively cold and dry conditions and that interstades were associated with relatively warm and wet conditions throughout the Great Basin between 50,500 and 27,000 GISP2 yr B.P. The Great Basin lacustrine climate records reinforce the hypothesis that D–O events affected the climate throughout much of the Northern Hemisphere during marine isotope stages 2 and 3. However, the absolute phasing between lake-size and ice-core δ 18O records remains difficult to determine.

Geochemistry of Pyramid Lake sediments: influence of anthropogenic activities and climatic variations within the basin

In 1998, a 59-cm sediment box core (PLB98-2) was taken from the deepest part of Pyramid Lake (water depth =106 m), Nevada. Age control for PLB98-2 was provided using a variety of approaches. Dried sediment samples were leached with 10% ultra-pure nitric acid and analyzed for their elemental concentrations using standard ICP techniques. The variations in elemental concentrations can be divided into two periods: one prior to European settlement and one influenced by anthropogenic activities. The concentrations of K, Al, Na, Zn, and Mn all began to increase after pre-European manipulation of the watershed in ~1860, which indicates the increasing soil erosion in the watershed was due to deforestation and development. The highest concentrations of these elements and lithogenic elements such as P, Mg, Fe, Cu, Ba, and Si occurred during the flood event of the 1990s. The Pb enrichment times are similar to what has been observed in estuaries draining the western Sierra Nevada, but the Pb enrichments in Pyramid Lake are much less. The Ca, TOC, TIC, Sr, and Ba concentrations show a strong association that is closely related to drought–wet variations of climate and the construction of Derby Dam for water diversions in the early 1900s. Se concentrations vary with the δ18O of the carbonate in the sediments. Although the δ18O "leads" the other species and Truckee River discharge by a few years, it is an excellent indicator of the hydrological change of Pyramid Lake, which is related to climate changes and human activities. From ~1920, Mn and Mo vary inversely in the sediments. In general, the Mo concentrations varies directly with the organic carbon content of the sediments from 1910 to ~1980, suggesting enhanced removal of Mo during times of increased productivity in the lake, and anoxic conditions at the sediment/water interface. This coincides with low lake levels. The elemental composition of the sediments in Pyramid Lake clearly reflect the timing of important anthropogenic activities and climatic variations that have taken place within the watershed over the past 240 years.

Age of the Mono Lake excursion and associated tephra

The Mono Lake excursion (MLE) is an important time marker that has been found in lake and marine sediments across much of the Northern Hemisphere. Dating of this event at its type locality, the Mono Basin of California, has yielded controversial results with the most recent effort concluding that the MLE may actually be the Laschamp excursion (Earth Planet. Sci. Lett. 197 (2002) 151). We show that a volcanic tephra (Ash ♯15) that occurs near the midpoint of the MLE has a date (not corrected for reservoir effect) of 28,620±300 14C yr BP (∼32,400 GISP2 yr BP) in the Pyramid Lake Basin of Nevada. Given the location of Ash ♯15 and the duration of the MLE in the Mono Basin, the event occurred between 31,500 and 33,300 GISP2 yr BP, an age range consistent with the position and age of the uppermost of two paleointensity minima in the NAPIS-75 stack that has been associated with the MLE (Philos. Trans. R. Soc. London Ser. A 358 (2000) 1009). The lower paleointensity minimum in the NAPIS-75 stack is considered to be the Laschamp excursion (Philos. Trans. R. Soc. London Ser. A 358 (2000) 1009).

HIBAL: a hydrologic-isotopic-balance model for application to paleolake systems

A simple hydrologic-isotopic-balance (HIBAL) model for application to paleolake δ 18O records is presented. Inputs to the model include discharge, on-lake precipitation, evaporation, and the δ 18O values of these fluid fluxes. Monthly values of climatic parameters that govern the fractionation of 18O and 16O during evaporation have been extracted from historical data sets and held constant in the model. The ability of the model to simulate changes in the hydrologic balance and the δ 18O evolution of the mixed layer has been demonstrated using measured data from Pyramid Lake, Nevada. Simulations of the response in δ 18O to step- and periodic-function changes in fluid inputs indicate that the hydrologic balance and δ 18O values lag climate change. Input of reconstructed river discharges and their δ 18O values to Pyramid and Walker lakes indicates that minima and maxima in simulated δ 18O records correspond to minima and maxima in the reconstructed volume records and that the overall shape of the volume and δ 18O records is similar. The model was also used in a simulation of abrupt oscillations in the δ 18O values of paleo-Owens Lake, California.

Population Genetic Structure in Lahontan Cutthroat Trout

We used 10 microsatellite loci to examine the genetic population structure of cutthroat trout Oncorhynchus clarki within the Lahontan Basin complex. Genetic diversity was analyzed for trout from Nevada, California, and Utah representing three putative subspecies: Lahontan O. c. henshawi, Paiute O. c. seleniris, and Humboldt (an unnamed subspecies) cutthroat trout. We found significant differences in microsatellite diversity among the three putative subspecies found in this area. Analysis of molecular variance partitioned microsatellite variation as 9.8% among subspecies, 27.7% among populations, and 62.5% within populations of Lahontan Basin cutthroat trout. Genetic distance analyses (Cavalli-Sforza-Edwards and Fst) supported unique population structure in cutthroat trout from the Humboldt and Pilot Peak drainages. Pairwise Fst values for Lahontan cutthroat trout were not significantly correlated with geographic distance between population pairs (r2 = 0.008; P < 0.0001), suggesting that they are extremely isolated populations with small effective sizes that are vulnerable to extinction. Two extant hatchery strains of Lahontan cutthroat trout showed genetic associations with different geographic source populations. The Pyramid Lake hatchery strain was most closely associated genetically with fish from Summit Lake. The Pilot Peak hatchery strain was associated genetically with Pilot Peak wild trout (Utah) and Macklin Creek trout (California). The phylogeographic diversity depicted in this study supports unique population structure and suggests important evolutionary relationships needed to evaluate transplanted populations and hatchery supplementation within the basin.

The Changing Political Fortunes of the Truckee-Carson Irrigation District

in California and end in Nevada. The Truckee River originates at Lake Tahoe and is fed below the lake by Prosser Creek, Martis Creek, Independence Creek, and the Little Truckee River. After crossing the border into Nevada, the Truckee flows east through Reno and Sparks, then turns north and ends at Pyramid Lake, natural sink or basin, from which water can only leave by evaporation. The headwaters of the Carson River originate in east and west forks in Alpine County, California. As it flows eastward the Carson River is impounded by the Lahontan Reservoir, part of the Newlands Project. After it is used for irrigation purposes on the Newlands Project, the water terminates in the Carson's sink, a wetland which fluctuates in size depending on the extent of the winter's snow pack in the Sierra Nevada Mountains.1 This article examines the changing political fortunes of the Newlands Project irrigators and their governing entity, the Truckee-Carson Irrigation District (TCID). The TCID is controlled by an elected board of directors cho-

Holocene multidecadal and multicentennial droughts affecting Northern California and Nevada

Continuous, high-resolution δ 18O records from cored sediments of Pyramid Lake, Nevada, indicate that oscillations in the hydrologic balance occurred, on average, about every 150 years (yr) during the past 7630 calendar years (cal yr). The records are not stationary; during the past 2740 yr, drought durations ranged from 20 to 100 yr and intervals between droughts ranged from 80 to 230 yr. Comparison of tree-ring-based reconstructions of climate change for the past 1200 yr from the Sierra Nevada and the El Malpais region of northwest New Mexico indicates that severe droughts associated with Anasazi withdrawal from Chaco Canyon at 820 cal yr BP (calendar years before present) and final abandonment of Chaco Canyon, Mesa Verde, and the Kayenta area at 650 cal yr BP may have impacted much of the western United States.During the middle Holocene (informally defined in this paper as extending from 8000 to 3000 cal yr BP), magnetic susceptibility values of sediments deposited in Pyramid Lake's deep basin were much larger than late–Holocene (3000–0 cal yr BP) values, indicating the presence of a shallow lake. In addition, the mean δ 18O value of CaCO 3 precipitated between 6500 and 3430 cal yr BP was 1.6‰ less than the mean value of CaCO 3 precipitated after 2740 cal yr BP. Numerical calculations indicate that the shift in the δ 18O baseline probably resulted from a transition to a wetter (>30%) and cooler (3–5°C) climate. The existence of a relatively dry and warm middle-Holocene climate in the Truckee River–Pyramid Lake system is generally consistent with archeological, sedimentological, chemical, physical, and biological records from various sites within the Great Basin of the western United States. Two high-resolution Holocene-climate records are now available from the Pyramid and Owens lake basins which suggest that the Holocene was characterized by five climatic intervals. TIC and δ 18O records from Owens Lake indicate that the first interval in the early Holocene (11,600–10,000 cal yr BP) was characterized by a drying trend that was interrupted by a brief (200 yr) wet oscillation centered at 10,300 cal yr BP. This was followed by a second early-Holocene interval (10,000–8000 cal yr BP) during which relatively wet conditions prevailed. During the early part of the middle Holocene (8000–6500 cal yr BP), high-amplitude oscillations in TIC in Owens Lake and δ 18O in Pyramid Lake indicate the presence of shallow lakes in both basins. During the latter part of the middle Holocene (6500–3800 cal yr BP), drought conditions dominated, Owens Lake desiccated, and Lake Tahoe ceased spilling to the Truckee River, causing Pyramid Lake to decline. At the beginning of the late Holocene (∼3000 cal yr BP), Lake Tahoe rose to its sill level and Pyramid Lake increased in volume.

Separation of Site Effects and Structural Focusing in Santa Monica, California: A Study of High-Frequency Weak Motions from Earthquakes and Blasts Recorded during the Los Angeles Region Seismic Experiment

Near-surface site factors and the effects of deep structural focusing were estimated in the Santa Monica Mountains and Santa Monica, California, from a portable array of 75 seismic stations deployed during the Los Angeles Region Seismic Experiment, Phase II (LARSE II). The objective was to examine further the origin of seismic wave amplification in the region of intense damage south of the Santa Monica Fault from the Northridge earthquake. The analysis used normalized spectral amplitudes in the 4- to 8- and 8- to 12-Hz range in direct and coda waves from local earthquakes in Santa Paula, Northridge, Redlands, and Hector Mine. Coda waves indicated that site factor amplifications are larger south of the Santa Monica fault relative to the north. Spectral ratios of direct S waves, corrected for site effects, show additional amplification south of, and adjacent to, the Santa Monica fault, attributable to focusing by a deeper structure. Gao et al. (1996) concluded that localized focusing effects contributed to anomalous P - and S -wave amplification in the Santa Monica damage zone for Northridge aftershocks within a specified range of azimuths. In an attempt to reproduce the hypothesized focusing from the Northridge earthquake, two shots (4000 and 3750 lb.) were detonated, one at Pyramid Lake, a distance of about 69 km to the north-northwest of central Santa Monica, and the other near Fort Tejon, a distance of 91 km. The azimuth of the shots was chosen to be that expected to give anomalous amplification. At these distances steeply incident seismic energy from Pg/PmP waves are expected to pass through the underground focusing structure and be selectively amplified. After the local site factors are removed, the waveforms from the Fort Tejon shot exhibited localized amplification adjacent to and south of the fault, 2-3 times larger than that of the surrounding area. The effect is less for waves from the Pyramid Lake shot, which could be due to their higher angle of incidence. The observations lend support to the argument that deep structural focusing is an important factor in determining azimuth-dependent amplification of seismic waves along a basin edge. Manuscript received 21 May 2001.

MERCURY IN WATER AND SEDIMENT OF STEAMBOAT CREEK, NEVADA: IMPLICATIONS FOR STREAM RESTORATION1

ABSTRACT: The objective of this study was to characterize the sources, concentrations, and distribution of total and methylmer‐cury in water, and channel and bank sediments of Steamboat Creek, Nevada. This information was needed to begin to assess the potential impacts of stream restoration on mercury pollution in this tributary to the Truckee River. The Truckee River flows into Pyramid Lake, a terminal water body home to one endangered and one threatened fish species, where stable pollutants will accumulate over time. Mercury in Steamboat Creek was originally derived from its headwaters, Washoe Lake, where several gold and silver mills that utilized mercury were located. In the 100 plus years since ore processing occurred, mercury‐laden alluvium has been deposited in the stream channel and on streambanks where it is available for remobilization. Total mercury concentrations measured in unfiltered water from the creek ranged from 82 to 419 ng/L, with greater than 90 percent of this mercury being particle‐bound (&gt; 0.45 (m). Mercury in sediments ranged from 0.26 to 10.2 μg/g. Methylmercury concentrations in sediments of Steamboat Creek were highest in wetlands, lower in the stream channel, and still lower in streambank settings. Methylmercury concentrations in water were 0.63 to 1.4 ng/L. A streambank restoration plan, which includes alterations to channel geometry and wetland creation or expansion, has been initiated for the creek. Data developed indicate that streambank stabilization could reduce the mercury loading to the Creek and that wetland construction could exacerbate methylmercury production.

Rapid changes in Late Pleistocene precipitation and stream discharge determined from medium- and coarse-grained sediment in saline lakes

Sediment-trapping investigations in Pyramid Lake, Nevada show that medium- to coarse-grained clastic sediments suspended in streamflow after periods of low flow can be transported several kilometers in plumes of freshwater discharged over the surface of a saline lake. Analogous conditions are postulated to explain changes in the abundance of detrital quartz in lake clay near the center of Estancia Basin, New Mexico during the Late Pleistocene. Abrupt increases in the abundance of quartz grains mark the onset of lake freshening, and ostracode and trace-metal proxies for salinity indicate repeated, brief episodes of streamflow and lake freshening during the Last Glacial Maximum (LGM).

Strain partitioning in the northern Walker Lane, western Nevada and northeastern California

Paleomagnetic studies constrain both the kinematics and the timing of Neogene intracontinental strain in the Walker Lane of northwestern Nevada–northeastern California. The northwest-trending Walker Lane is a zone of complex faulting and dextral offset along the boundary between the Sierra Nevada and the Basin and Range. Here, an extensive Tertiary volcanic section provides a paleomagnetic test for vertical-axis rotation. The 25.1 Ma Nine Hill tuff covered the two structural domains of northern Walker Lane and parts of the adjacent provinces. In the northernmost domain, the Pyramid Lake domain, the Nine Hill tuff is unrotated or rotated slightly counter-clockwise. In contrast, Nine Hill tuff is rotated 35–44° clockwise in the northeastern part of the adjacent Carson domain. Usable exposures of the tuff are lacking elsewhere in the Carson domain, but 9–13 Ma basalts record 37°–51° clockwise vertical-axis rotation. These basalts were sampled at three sites encompassing the N–S length of the Carson domain. Younger basalts from the Carson domain show smaller clockwise rotations. The paleomagnetic studies show that the deformation in the northern Walker Lane is partitioned into domains dominated by translation, rotation and extension. Dextral slip along the Walker Lane is accommodated primarily by northwestward translation in the Pyramid Lake domain, and by clockwise vertical-axis rotation in the Carson domain. Some Neogene extension is also accommodated in the Walker Lane, but most of it is occurring to the west of the Walker Lane, along the edge of the Sierra Nevada.Comparison of paleomagnetic results from rocks of different ages constrains the timing of the present deformation regime in the Walker Lane. The similar rotations recorded in 25 Ma and 9–13 Ma rocks indicates that virtually all of the rotation in the Carson domain occurred after the eruption of the 9–13 Ma basalts. Smaller rotations recorded in younger rocks constrain rotation rate.

Oxyanion Concentrations in Eastern Sierra Nevada Rivers – 3. Boron, Molybdenum, Vanadium, and Tungsten

Water samples were collected from 10 locations along the Truckee River system, 14 locations along the Walker River system, and 12 locations along the Carson River, and analyzed for B, Mo, V, W, Na, Cl, and pH. Boron concentrations ranged from approximately 2 μmol/kg in the upper reaches of the Truckee River to almost 1,200 μmol/kg in Pyramid Lake. Molybdenum, V, and W had concentrations in the nanomolal range; Mo varied from a low of about 12 nmol/kg to a high of 3,200 nmol/kg (Walker Lake); V ranged from 9 nmol/kg to approximately 470 nmol/kg; and W varied from a low value around 0.8 nmol/kg (West Walker River) to 1,030 nmol/kg. The high concentrations of these oxyanion-forming trace elements in the rivers reflects (1) the relative stability of these oxyanions (e.g., MoO4 2-, HVO4 2-, WO4 2-, B(OH)3, and/or B(OH)4 -) in the alkaline, well oxygenated river and lake waters, (2) contributions of hydrothermal waters (especially for B), and (3) weathering of rocks/regolith with high concentrations of these elements. In the case of Mo, V, and W, each exhibited relatively conservative behavior in the upper, oxygenated reaches of all three rivers. During the study period the region experienced a prolonged drought such that the lower reaches of each river were typified by no flow or stagnant waters and probably low oxygen and/or anoxic conditions (although not measured). Reductive processes occurring in the low flow to stagnant reaches of each river could have led to removal of Mo, V, and W from solution as coprecipitates with Fe monosulfides, or via sorption to Fe oxides/oxyhydroxides and/or organic matter. Boron, however, exhibited essentially no or minor removal from these rivers, and instead was added to each river via B-rich hydrothermal waters (e.g., Steamboat Creek from Steamboat Hot Springs), or by B-rich groundwaters via base-flow during the extensive drought.

Report on the Sixty-Second Annual Meeting

REPORT ON THE SIXTY-SECOND ANNUAL MEETING Reno, Nevada September 29-October 2,1999 T he return of the APCG annual meeting to Reno after nearly 20 years offered the Department of Geography at the University of Nevada the opportunity to showcase northern Nevada as a unique and some­ times provocative setting for geographical studies both human and physical, not to mention its role as a venue for having a good time. Northern Nevada welcomed 198 attendees to this year's meeting. Following in the footsteps of last year's Flagstaff meeting, student participation remained high at 90, orjust over 45 percent. Geographi­ cally, California provided 105 attendees, followed by Arizona with 23, Nevada with 22, Oregon with 13, Washington with 12, Idaho with ligand Alaska with 2. We also were joined by geographers from as far away as Ohio, New Hampshire, Kentucky, Louisiana, and the winner for distance is—Hong Kong. Special note should be made of several schools whose students came en masse, including San Francisco State, Sonoma State, Arizona State, Western Wash­ ington, the University of Oregon, and the 11-person contingent from the University of Idaho. Congratulations to faculty advisers, home institutions, and the students themselves for such outstanding rep­ resentation. The Poolside Terrace at John Ascuagua's Nugget, host hotel for the meeting, provided the venue for Wednesday evening's opening plenary session, where it was not lost on a group of geographers that the Mayor of Reno was welcoming us while actually located in Sparks, once again reminding us that "Reno is so close to hell you can see Sparks." The 115 people who attended the opening plenary session heard artist Peter Goin, geographer Scott Mensing, and State Water Planner Naomi Duerr give three different approaches to un­ derstanding of the Truckee River, one of northern Nevada's natural treasures. A post-plenary session reception established the Great Basin Brewing Company, located within walking distance of the Nugget, as a favorite watering hole for the remainder of the meet­ ing. 158 Annual Meeting Report 159 Thursday was filled with 12 paper sessions and the presidential plenary session, where James Allen, Peter Groth, and Phillip Pryde offered insights into the importance of locality in an era of global­ ization. Thursday's activities ended with a reception and poster session in the Poolside Terrace. On Friday, meeting participants chose one of three all-day fieldtrips with John James to the Tahoe Basis, Bill Kersten and State Historic Preservation Officer Ron James to Virginia City, or Scott Mensing and Kate Berry to Pyramid Lake. Despite low visibility as a result of the intrusion of smoke from Cali­ fornia fires into the clean high desert air (surely a kind of symbolic statement on the relationship between the two states), participants returned tired but enthusiastically complimentary about their ex­ periences in the field. The demands of an all-day fieldtrip did not diminish enthusiastic APCG students from competing in this year's GeoBowl later that afternoon. Saturday's paper sessions brought the total number of papers presented to 86 over the course of the meet­ ing, of which 33 were student papers! The Women's Network luncheon was filled to capacity, and after the final paper session, AAG President Reginald Golledge spoke at the Business Meeting about current AAG issues of interest to the APCG. It has been contended that if John Ascuagua's can't do Basque, nobody can. Saturday's closing banquet proved this true. Ninetynine people enjoyed this northern Nevada dining experience. Incoming APCG President Tina Kennedy served as MC for the evening's program. As a special treat, University of Nevada Presi­ dent Joe Crowley entertained the crowd with stories and anecdotes about geography and life as explained to him by his kid brother, Bill. As always, Bill Crowley was a good sport after being spitted in the mini-roast. The evening concluded with outgoing APCG Presi­ dent Robin Datel's Presidential Address, in which she offered insights into past APCG and AAG presidential addresses. Now that the attendees have departed and the skies have cleared of California smoke, it is possible to stand back and appreciate what we believe was a challenging, yet worthwhile...

Calcification in cyanobacterial biofilms of alkaline salt lakes

Geomicrobiological analysis of calcifying biofilms of three alkaline salt lakes characterized by moderate to high carbonate alkalinity indicates that microbial carbonate rock formation is not directly linked to cyanobacterial carbon fixation. The present review summarizes results from two published case studies that have been carried out at Pyramid Lake, USA, and Lake Nuoertu, PR China. New observations and data are presented for a current project on Satonda Crater Lake, Indonesia, that revise previous conclusions concerning the relationship between cyanobacteria and biofilm calcification. Extracellular polymeric substances (EPS) in the investigated lakes are mostly produced by cyanobacteria; their properties are discussed as key factors in biofilm calcification. In particular, EPS are capable of binding divalent cations (e.g. Ca2+) from the liquid phase by their carboxylate and sulphate groups. Therefore, despite a high supersaturation of the lake water with respect to calcium carbonate minerals, precipitation does not take place immediately. A delayed onset of precipitation can be achieved by a continuous Ca2+ supply that exceeds the Ca2+-binding capacity of the EPS, and/or an exoenzymatic degradation (decarboxylation, cleavage) of mucous substances that reduces the binding capacity and causes secondary Ca2+ release. The resulting microcrystalline precipitates are randomly distributed within the EPS, usually away from any of the living cyanobacteria. This suggests that the effect of photosynthetic CO2 fixation in increasing supersaturation is of secondary importance at high alkalinities. In contrast to biofilm-covered surfaces, calcium carbonate minerals nucleate and grow rapidly at surfaces poor in EPS when the critical supersaturation level for non-enzymatically controlled carbonate precipitation is reached. Examples of such surfaces poor in EPS are dead, lysed green algal cells and thin, discontinuous biofilms in voids of microbial reef rocks. Calcium carbonate crystals directly linked to cyanobacterial cells or filaments have been observed only exceptionally, e.g. on Calothrix.

Calcification in cyanobacterial biofilms of alkaline salt lakes

Geomicrobiological analysis of calcifying biofilms of three alkaline salt lakes characterized by moderate to high carbonate alkalinity indicates that microbial carbonate rock formation is not directly linked to cyanobacterial carbon fixation. The present review summarizes results from two published case studies that have been carried out at Pyramid Lake, USA, and Lake Nuoertu, PR China. New observations and data are presented for a current project on Satonda Crater Lake, Indonesia, that revise previous conclusions concerning the relationship between cyanobacteria and biofilm calcification. Extracellular polymeric substances (EPS) in the investigated lakes are mostly produced by cyanobacteria; their properties are discussed as key factors in biofilm calcification. In particular, EPS are capable of binding divalent cations (e.g. Ca2+) from the liquid phase by their carboxylate and sulphate groups. Therefore, despite a high supersaturation of the lake water with respect to calcium carbonate minerals, precipitation does not take place immediately. A delayed onset of precipitation can be achieved by a continuous Ca2+ supply that exceeds the Ca2+-binding capacity of the EPS, and/or an exoenzymatic degradation (decarboxylation, cleavage) of mucous substances that reduces the binding capacity and causes secondary Ca2+ release. The resulting microcrystalline precipitates are randomly distributed within the EPS, usually away from any of the living cyanobacteria. This suggests that the effect of photosynthetic CO2 fixation in increasing supersaturation is of secondary importance at high alkalinities. In contrast to biofilm-covered surfaces, calcium carbonate minerals nucleate and grow rapidly at surfaces poor in EPS when the critical supersaturation level for non-enzymatically controlled carbonate precipitation is reached. Examples of such surfaces poor in EPS are dead, lysed green algal cells and thin, discontinuous biofilms in voids of microbial reef rocks. Calcium carbonate crystals directly linked to cyanobacterial cells or filaments have been observed only exceptionally, e.g. on Calothrix.

Biofilm exopolymers control microbialite formation at thermal springs discharging into the alkaline Pyramid Lake, Nevada, USA

Calcium carbonate precipitation and microbialite formation at highly supersaturated mixing zones of thermal spring waters and alkaline lake water have been investigated at Pyramid Lake, Nevada. Without precipitation, pure mixing should lead to a nearly 100-fold supersaturation at 40oC. Physicochemical precipitation is modified or even inhibited by the properties of biofilms, dependent on the extent of biofilm development and the current precipitation rate. Mucus substances (extracellular polymeric substances, EPS, e.g., of cyanobacteria) serve as effective Ca 2C -buffers, thus preventing seed crystal nucleation even in a highly supersaturated macroenvironment. Carbonate is then preferentially precipitated in mucus-free areas such as empty diatom tests or voids. After the buffer capacity of the EPS is surpassed, precipitation is observed at the margins of mucus areas. Hydrocarbon biomarkers extracted from (1) a calcifying Phormidium-biofilm, (2) the stromatolitic carbonate below, and (3) a fossil ‘tufa’ of the Pleistocene pinnacles, indicate that the cyanobacterial primary producers have been subject to significant temporal changes in their species distribution. Accordingly, the species composition of cyanobacterial biofilms does not appear to be relevant for the formation of microbial carbonates in Pyramid Lake. The results demonstrate the crucial influence of mucus substances on carbonate precipitation in highly supersaturated natural environments. © 1999 Elsevier Science B.V. All rights reserved.

INTEGRATED WATERSHED MANAGEMENT ON THE TRUCKEE RWER IN NEVADA1

ABSTRACT: The Truckee River is a vitally important water source for eastern California and western Nevada. It runs 100 miles from Lake Tahoe to Pyramid Lake in the Nevada desert and serves urban populations in greater Reno‐Sparks and agricultural users in three Nevada counties. In the 1980s and 1990s, a number of state and local groups initiated projects which, taken collectively, have accomplished much to improve watershed management on the Truckee River. However, the task of writing a management plan for the entire watershed has not yet been undertaken. Key players in state, federal and local government agencies have instead chosen to focus specific improvement efforts on more manageable, achievable goals. The projects currently underway include a new agreement on reservoir operation, restoration of high priority sub‐watersheds, public education and involvement, water conservation education, and water resource planning for the major urban population centers. The approach which has been adopted on the Truckee River continues to evolve as more and more people take an interest in the river's future. The many positive projects underway on the watershed are evaluated in terms of how well they meet the definition of the ambitious water resources strategy, “integrated watershed management.”