Geology topics

Mark A. Johnson

Publications and source records attributed to Mark A. Johnson.

2 recordsLinked to original sources

USGS2011

Demographics and run timing of adult Lost River ( Deltistes luxatus ) and short nose ( Chasmistes brevirostris ) suckers in Upper Klamath Lake, Oregon, 2009

Data from a long-term capture-recapture program were used to assess the status and dynamics of populations of two long-lived, federally endangered catostomids in Upper Klamath Lake, Oregon. Lost River suckers ( Deltistes luxatus ) and shortnose suckers ( Chasmistes brevirostris ) have been captured and tagged with passive integrated transponder (PIT) tags during their spawning migrations in each year since 1995. In addition, beginning in 2005, individuals that had been previously PIT-tagged were reencountered on remote underwater antennas deployed throughout the spawning areas. Captures and remote encounters during spring 2009 were used to describe the spawning migrations in that year and also were incorporated into capture-recapture analyses of population dynamics over the last decade. Cormack-Jolly-Seber (CJS) open population capture-recapture models were used to estimate annual survival probabilities, and a reverse-time analog of the CJS model was used to estimate recruitment of new individuals into the spawning populations. In addition, data on the size composition of captured fish was examined for any additional evidence of recruitment. Survival and recruitment estimates were combined to estimate changes in population size over time and to determine the status of the populations through 2007. Separate analyses were conducted for each species and also for each subpopulation of Lost River suckers (LRS). One subpopulation of LRS migrates into tributaries to spawn, similar to shortnose suckers (SNS), whereas the other subpopulation spawns at upwelling areas along the eastern shoreline of the lake. In 2009, we captured and tagged 781 LRS at four shoreline areas and recaptured an additional 638 individuals that had been tagged in previous years. Across all four areas, the remote antennas detected 6,056 individual LRS during the spawning season. Spawning activity peaked in April and most individuals were encountered at Sucker Springs and Cinder Flats. In the Williamson River, we captured and tagged 3,008 LRS and 287 SNS, and recaptured 271 LRS and 81 SNS that had been tagged in previous years. Remote antennas that spanned the river downstream of the tributary spawning areas detected a total of 12,509 LRS and 5,023 SNS. Most LRS passed upstream in mid-April when water temperatures were rising and near or greater than 10°C. In contrast, peaks in upstream passage of SNS occurred in late April and early May when water temperatures were rising and near or greater than 12°C. Finally, an additional 1,569 LRS and 1,794 SNS were captured in trammel net sampling at prespawn staging areas in the northeastern portion of the lake. Of these, 209 of the LRS and 452 of the SNS had been PIT-tagged in previous years. For LRS, encounter histories showed that nearly all of the fish captured at the staging areas were members of the subpopulation that spawns in the tributaries. Capture-recapture analyses for the LRS subpopulation that spawns at the shoreline areas included encounter histories for more than 9,000 individuals, and analyses for the subpopulation that spawns in the tributaries included more than 14,000 encounter histories. With a few exceptions, the survival of males and females in both subpopulations was high (>0.9) between 1999 and 2007. Notably lower survival occurred for both sexes from the tributaries in 2000, for males from the shoreline areas in 2002, and for males from the tributaries in 2006. Recruitment of new individuals into either spawning population was trivial in all years between 2002 and 2007. Over that period, the abundance of males in the lakeshore spawning subpopulation declined by 44–53 percent and the abundance of females declined by 25–38 percent. Similarly, the abundance of males in the tributary spawning subpopulation declined by as much as 39 percent and the abundance of females declined by as much as 33 percent. Capture-recapture analyses for SNS included encounter histories for more than 12,000 individuals. The majority of annual survival estimates between 2001 and 2007 were high (>0.8), but SNS experienced more years of low survival than either LRS subpopulation. The survival of both sexes was particularly low in both 2001 and 2004, and male survival also was somewhat low in 2002 and 2006. Similar to LRS, recruitment of new individuals into the spawning population was trivial in all years between 2001 and 2007. Over that period, the abundance of male SNS declined by 58–80 percent and the abundance of females declined by 52–73 percent. Despite relatively high survival in most years, both species have experienced substantial declines in the abundance of spawning fish because losses from mortality have not been balanced by recruitment of new individuals. Indeed, all populations appear to be largely comprised of fish that were present in the late 1990s and early 2000s. As a result, the status of the endangered sucker populations in Upper Klamath Lake remains worrisome, and the situation is most dire for shortnose suckers. Survival analyses show that the two species do not necessarily experience poor survival in the same years and that poor survival on an annual scale is not predictable from fish die-offs observed in the summer and fall. Future analyses will explore the connections between annual sucker survival and environmental factors of interest, such as water quality and disease. Our monitoring program provides a robust platform for estimating vital population parameters, evaluating the status of the populations, and assessing the effectiveness of conservation and recovery efforts.

Oregon↗

USGS1997

Natural attenuation of chlorinated volatile organic compounds in a freshwater tidal wetland, Aberdeen Proving Ground, Maryland

Ground-water contaminant plumes that are flowing toward or currently discharging to wetland areas present unique remediation problems because of the hydrologic connections between ground water and surface water and the sensitive habitats in wetlands. Because wetlands typically have a large diversity of microorganisms and redox conditions that could enhance biodegradation, they are ideal environments for natural attenuation of organic contaminants, which is a treatment method that would leave the ecosystem largely undisturbed and be cost effective. During 1992-97, the U.S. Geological Survey investigated the natural attenuation of chlorinated volatile organic compounds (VOC's) in a contaminant plume that discharges from a sand aquifer to a freshwater tidal wetland along the West Branch Canal Creek at Aberdeen Proving Ground, Maryland. Characterization of the hydrogeology and geochemistry along flowpaths in the wetland area and determination of the occurrence and rates of biodegradation and sorption show that natural attenuation could be a feasible remediation method for the contaminant plume that extends along the West Branch Canal Creek. The aquifer, which received contaminants in the past from sources that were located upgradient of the current eastern boundary of the wetland, is about 40 to 45 feet thick in the study area. The overlying wetland sediments consist of two distinct layers that have a combined thickness of about 6 to 12 feet--an upper unit of peat and a lower unit of silty to sandy clay or clayey sand. Head distributions show strong vertical gradients, and flow directions are predominantly upward through the wetland sediments. Tidal fluctuations, however, cause some reversals in ground-water-flow directions and changes in discharge locations, which affect the distribution and transport of contaminants. The average linear velocity of ground water is estimated to be about 2 to 3 feet per year along vertical flow lines in the wetland area, and the total ground-water discharge along a 1-foot-wide strip of the wetland extending from the eastern wetland boundary to the creek is in the range of 0.13 to 0.25 feet squared per day. The major parent contaminants in the aquifer were trichloroethylene (TCE); 1,1,2,2-tetrachloroethane (PCA); carbon tetrachloride (CT); and chloroform (CF). The aquifer was typically aerobic, but ground water in the wetland sediments became increasingly anaerobic along the upward flow direction. Iron-reducing conditions were predominant in the lower wetland sediment unit composed of clayey sand and silt, and methanogenesis was predominant in an upper unit composed of peat. Total concentrations of VOC's and the relative proportions of parent compounds to anaerobic daughter products changed substantially as the contaminants were transported upward through these changing redox environments. Concentrations of the parent compounds TCE and PCA ranged from about 100 to 2,000 micrograms per liter in the aquifer beneath the wetland, whereas concentrations of daughter products were low or undetectable. In contrast, the parent compounds commonly were not detected in ground water in the wetland sediments, but the daughter compounds 1,2- dichloro-ethylene (12DCE), vinyl chloride (VC), 1,1,2-trichloroethane (112TCA), and 1,2-dichloroethane (12DCA) were observed. 12DCE and VC were the dominant daughter products in the wetland sediments, even where PCA was the primary parent contaminant discharging to the wetland. The presence of these daughter products in water in the wetland sediments indicates that TCE and PCA are degraded by reductive dechlorination reactions in the naturally anaerobic wetland sediments. Although production of daughter products was observed, total concentrations of the VOC's decreased upward through the 6- to 12-feet-thick wetland sediments and were less than 5 micrograms per liter near the surface. The daughter products are apparently further degraded by these anaerobic processes to non-chlorinated, non-toxic endproducts, or are removed by other attenuation processes such as aerobic degradation or volatilization. Several sets of anaerobic microcosms, some amended with TCE concentrations of 400 or 990 micrograms per liter (3.0 or 7.5 micromoles per liter) and one amended with PCA concentration of 480 micrograms per liter (2.9 micromoles per liter), were constructed in the laboratory using wetland sediment and ground water from the study area. These microcosm experiments confirmed field observations that 12DCE and VC are the dominant daughter products from anaerobic biodegradation of both TCE and PCA. Production of 112TCA and 12DCA also was observed in the PCA-amended microcosms, but concentrations were lower than those of 12DCE and VC. These results indicate that degradation of PCA occurs through both hydrogenolysis and dichloroelimination pathways under anaerobic conditions. Daughter products were not observed in sterile controls, except for relatively low concentrations of 12DCE in the PCA-amended controls, suggesting that the reactions were predominantly microbially mediated. Parent and daughter concentrations in the microcosms decreased to less than 5 micrograms per liter in less than 34 days under methanogenic conditions, thus showing extremely rapid biodegradation rates in these organic-rich wetland sediments. Maximum potential rate constants for biodegradation of TCE and PCA, which were calculated from the microcosm exper-iments assuming first-order degradation rates, ranged from 0.10 to 0.31 per day under methanogenic conditions, corresponding to half-lives of 2 to 7 days. The rate constant for TCE biodegradation under sulfate-reducing conditions was 0.045 West Branch, Aberdeen Proving Ground, Maryland 3 per day (half-life of 15 days), which is lower than under methanogenic conditions. These estimated rate constants for the wetland sediments are two to three orders of magnitude higher than those reported in the literature for TCE biodegradation in microcosms constructed with sandy aquifer sediments. Aerobic biodegradation rates for cis-12DCE, trans-12DCE, and VC were in the same range as those measured for TCE and PCA under anaerobic conditions in microcosm experiments. Thus, production of these daughter products by anaerobic biodegradation of TCE and PCA could be balanced by their consumption where oxygen is available in the wetland sediment, such as near roots and land surface. In the aerobic microcosm experiments, biodegradation of cis-12DCE, trans-12DCE, and VC occurred only if methane consumption occurred, indicating that methanotrophs were involved in the process. Aerobic biodegradation was fastest for vinyl chloride and slowest for TCE in the microcosm experiments. These results agree with other laboratory and field studies that have shown faster degradation by methane-utilizing cultures when the compounds are less halogenated. Equilibrium sorption isotherms were measured in 24-hour batch tests and used to estimate distribution coefficients ( K d 's) to describe the ratios of sorbed to aqueous concentrations of PCA and the daughter products cis-12DCE, trans-12DCE, and VC. The estimated K d's for PCA, cis-12DCE, trans-12DCE, and VC were about 2.3, 1.8, 2.4, and 1.3 liters per kilogram of sediment, respectively. Sorbed concentrations of PCA, cis-12DCE, and trans-12DCE in the wetland sediments, therefore, would be expected to be about twice the concentration measured in the water, whereas sorbed concentrations of VC would not be much greater than the aqueous concentrations. Coefficients of retardation, which were calculated using the K d 's and an advective flow velocity of about 2 feet per year, indicate that sorption alone would cause the movement of the contaminants in the wetland sediments to be 6 to 10 times slower than the advective ground-water flow. Biodegradation and sorption, therefore, are significant natural attenuation mechanisms for chlorinated hydrocarbons in these wetland sediments. The relatively thin layers of wetland sediments are critical in reducing contaminant concentrations and toxicity of the ground water before it discharges to the wetland surface and the creek, and natural attenuation in the wetland sediments could be an effective remediation method for the ground-water contaminants.

Maryland↗