9 results on '"Alan M. Piggot"'
Search Results
2. Environmental and Biological Controls on Sedimentary Bottom Types in the Puquios of the Salar de Llamara, Northern Chile
- Author
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Erica P. Suosaari, Amanda M. Oehlert, Ioan Lascu, Alan W. Decho, Alan M. Piggot, Alvaro T. Palma, Paul F. Machabee, and R. Pamela Reid
- Subjects
EPS ,Puquios ,microbe-mineral interactions ,polyextreme ,Salar de Llamara ,Geology ,QE1-996.5 - Abstract
The Puquios of the Salar de Llamara in the Atacama Desert, northern Chile, is a system of small lakes that is characterized by evaporitic mineral deposition and that commonly hosts microbial communities. This region is known for its extreme aridity, solar irradiance, and temperature fluctuations. The Puquios are a highly diverse ecosystem with a variety of sedimentary bottom types. Our previous results identified electrical conductivity (EC) as a first-order environmental control on bottom types. In the present paper, we extend our analysis to examine the effects of additional environmental parameters on bottom types and to consider reasons for the importance of EC as a control of sedimentology. Our results identify microbially produced extracellular polymeric substances (EPS) as a major player in the determination of bottom types. The relative amounts and properties of EPS are determined by EC. EPS, in turn, determines the consistency of bottom types, exchange of bottom substrate with the overlying water column, and mineral precipitation within the substrate. Low-EC ponds in the Puquios system have flocculent to semi-cohesive bottom types, with low-viscosity EPS that allows for high-exchange with the surrounding waters and mineral precipitation of granular gypsum, carbonate, and Mg–Si clay in close association with microbes. Ponds with elevated EC have bottom types that are laminated and highly cohesive with high-viscosity EPS that restricts the exchange between sediments and the surrounding waters; mineral precipitation in these high-EC ponds includes granular to laminated gypsum, carbonate and Mg–Si, which also form in close association with microbes. Bottom types in ponds with EC above the threshold for thriving benthic microbial communities have insufficient EPS accumulations to affect mineral precipitation, and the dominant mineral is gypsum (selenite). The variations in EPS production throughout the Puquios, associated with heterogeneity in environmental conditions, make the Puquios region an ideal location for understanding the controls of sedimentary bottom types in evaporative extreme environments that may be similar to those that existed on early Earth and beyond.
- Published
- 2022
- Full Text
- View/download PDF
3. Potential Impacts of PCBs on Sediment Microbiomes in a Tropical Marine Environment
- Author
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James S. Klaus, Vassiliki H. Kourafalou, Alan M. Piggot, Ad Reniers, HeeSook Kang, Naresh Kumar, Elsayed M. Zahran, Leonidas G. Bachas, Adolfo Fernandez, Piero Gardinali, Michal Toborek, Sylvia Daunert, Sapna Deo, and Helena M. Solo-Gabriele
- Subjects
polychlorinated biphenyls ,PCBs ,hydrodynamics ,transport ,marine sediments ,microbiome ,Naval architecture. Shipbuilding. Marine engineering ,VM1-989 ,Oceanography ,GC1-1581 - Abstract
Within the tropical marine study site of Guánica Bay, Puerto Rico, polychlorinated biphenyls (PCBs) are subjected to coastal and oceanic currents coupled with marine microbial and geochemical processes. To evaluate these processes a hydrodynamic model was developed to simulate the transport of PCBs within nearshore and offshore marine areas of Guánica Bay. Material transport and circulation information from the model were matched with measurements from samples collected from within the bay. These samples, consisting of both intertidal and submerged sediments, were analyzed for physical characteristics (organic carbon, grain size, and mineralogy), microbial characteristics (target bacteria levels and microbial community analyses), presence of PCBs, and PCB-degrading enzymes. Results show that the bay geometry and bathymetry limit the mixing of the extremely high levels of PCBs observed in the eastern portion of the bay. Bay bottom sediments showed the highest levels of PCBs and these sediments were characterized by high organic carbon content and finer grain size. Detectable levels of PCBs were also observed within sediments found along the shore. Microbes from the bay bottom sediments showed a greater relative abundance of microbes from the Chloroflexi, phylum with close phylogenetic associations with known anaerobic PCB-degrading organisms. Based on quantitative PCR measurement of the biphenyl dioxygenase gene, the intertidal sediments showed the greatest potential for aerobic PCB degradation. These results elucidate particular mechanisms of PCB’s fate and transport in coastal, tropical marine environments.
- Published
- 2016
- Full Text
- View/download PDF
4. Environmental controls on sedimentary deposits in saline lake environments
- Author
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Amanda M. Oehlert, Alan M. Piggot, Erica P. Suosaari, Alvaro T. Palma, Luis R. Daza, Tianshu Kong, Clément G.L. Pollier, Cecilia Demergasso, Guillermo Chong, and R. Pamela Reid
- Abstract
Saline lakes are known to be sensitive to changes in environmental conditions on a broad temporal scale. Therefore, variations in the mineralogical, geochemical, and sedimentological characteristics of these settings have often been interpreted to reflect oscillations in climatic conditions. However, recent work has shown that microbial communities can also influence the formation of carbonate and evaporite minerals in saline lake environments, especially in the salars of South America. Here, both abiotic and organomineralization pathways can be found to exist within the same salar environments, indicating a high degree of spatial heterogeneity of mineralization processes in such settings. Thus, the drivers of the resulting mineral assemblage can be complicated to disentangle through space and time. A process-level understanding of first-order controls on mineral assemblages can provide new insights into sedimentological dynamics of salar environments.Babel (2004) published a conceptual model based on marine-fed systems that established links between salinity and the style of gypsum mineral deposition. Based on field and laboratory analyses conducted on sediments in the Salar de Llamara, we adapted this model for a continental saline lake setting (Reid et al., 2021). In the present study, we aimed to test whether our salar-scale conceptual model was applicable more generally to continental saline lake environments. To accomplish this goal, we investigated a 15-year time series of electrical conductivity, a proxy for salinity, collected in five saline lake/wetland systems situated along the margin of the Salar de Atacama. Based on this dataset, we predicted the style and mineralogy of mineral deposition in each setting using our salar-scale conceptual model. Next, we compared our predictions with published field descriptions of the occurrences of biofilms, microbial mats, microbialites, and evaporite deposits in these lakes. Through a principal component analysis, we evaluated environmental characteristics such as electrical conductivity, pH, and dissolved oxygen as controls on mineral morphology and mineralogy.Results indicate that salinity is a first-order control on sedimentological expression in the lakes of the Salar de Atacama, although the transition between organomineralization pathways and physicochemical precipitation may occur at different salinity values than observed in other saline lake settings. Broadly in agreement with our model from the Salar de Llamara, granular precipitates of carbonate minerals formed within microbial mats were associated with environments characterized by low salinity, while microbial mats with laminated precipitates were found in settings with moderate salinity in the Salar de Atacama. High salinity environments contained crystalline bottom types characterized by selenitic morphology. Because some South American salars have been cited as living laboratories analogous to the ancient conditions that fostered the evolution of terrestrial and Martian life, these insights into mineralization are important. Improved constraints on the controls of carbonate and evaporite mineral deposition in saline lake environments will elucidate the definition of habitable environments, and provide a testing ground for the production and preservation of chemical and morphological biosignatures through time.
- Published
- 2023
- Full Text
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5. Sedimentological characterization of geological cores from marginal lakes in the Salar de Atacama
- Author
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Alan M. Piggot, R. Pamela Reid, and Amanda M. Oehlert
- Abstract
Although thought to be high-resolution archives of paleoenvironmental changes, subsurface sediments deposited in saline lakes situated in salar environments have rarely been studied. To address this knowledge gap, sediment cores of varying depths ranging from 0.42 to 2.2 meters were collected from four saline lakes along the eastern margin of the Salar de Atacama, Chile. Characterization included sedimentological descriptions of lithification, sedimentary structures (microbial mats and microbialites), and color, as well as discrete measurements of total organic carbon content. Radiocarbon analysis was conducted on organic matter in the sediments. The recovered subsurface lithologies were heterogenous in color, stratigraphic features, and age dates, especially when compared between the lakes. Intervals of coarser sediment in the Soncor system lakes Chaxa, Burros Muertos and Barros Negros, appeared to be crystalline and were likely precipitated during periods characterized by higher salinity lake waters. Sediment cores collected from the Soncor system were broadly characterized by low total organic carbon content and punctuated intervals of coarse grained material deeper in the core. In the core collected from Aguas de Quelana, variations in lithology and hardgrounds were commonly observed. In concert, these results suggest that the eastern periphery of the salar was impacted by changes in salinity and water depth as these wetland area experienced changes in extent as a result of changes in wet and dry periods. Radiocarbon dating conducted on organic matter sampled at 4 intervals from each core revealed ages that were significantly older than expected, possibly due to local reservoir effects and subsurface hydrological dynamics. There were five age reversals documented in the transect of cores suggesting that the sources of radiocarbon may have changed over time. Results indicate that the geologic records of saline lake environments are as heterogeneous through time as they are in space.
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- 2023
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6. Physical, chemical, and microbial feedbacks controlling brine geochemistry and lake morphology in polyextreme salar environments
- Author
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Amanda M. Oehlert, Erica P. Suosaari, Tianshu Kong, Alan M. Piggot, Daniela Maizel, Ioan Lascu, Cecilia Demergasso, Guillermo Chong Díaz, and R. Pamela Reid
- Subjects
Lakes ,Environmental Engineering ,Environmental Chemistry ,Humans ,Salts ,Pollution ,Waste Management and Disposal ,Ecosystem ,Feedback - Abstract
Despite the harsh environmental conditions in the world's oldest and driest desert, some salt flat or 'salar' environments in the Atacama Desert host standing bodies of water known as saline lakes. Evaporite minerals deposited within saline lakes result from the equilibrium of environmental, sedimentological, and biogeochemical processes that occur in the salar; consequently, these minerals are sensitive records of human activities and ecological, evolutionary, and geological changes. The objective of this study was to evaluate feedbacks between physical, chemical, and microbial processes that culminate in distinct trends in brine chemistry, saline lake morphology, and associated evaporite sediments. Using samples from the Puquios of the Salar de Llamara, Atacama Desert, northern Chile, an analysis of spatial gradients and vertical stratification of lake elemental chemistry and mineral saturation indices were integrated with a comprehensive analysis of lake morphology, including depth, slope gradient, substrate type, and mineralogy. Lake waters ranged from saline to hypersaline, and exhibited normal, well mixed and inverse stratification patterns, and results suggest a correlation with lake morphology in the Salar de Llamara. Saline to hypersaline lakes (150 mS/cm) with stratified brines tended to have crystalline substrate and deep (35 cm) and steep-sided lake morphologies, while unstratified lakes with lower electrical conductivity (90 mS/cm and microbial substrates had gentle slopes and characteristically shallow depths (30 cm). Differences in minor element chemistry (Mn and Sr) between saline lakes were observed on scales of meters to kilometers, and result in different accessory mineral assemblages. Quantification of the physical, chemical, and microbial feedbacks that produce the observed heterogeneity in these ecosystems provides key insight into the geochemical composition and lake morphology of saline lakes in extreme environments around the world.
- Published
- 2022
7. Species‐specific responses to climate change and community composition determine future calcification rates of Florida Keys reefs
- Author
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Andrew C. Baker, Chris Langdon, Ross Cunning, Ruben van Hooidonk, Remy Okazaki, Rivah N. Winter, Carolina Mor, Peter K. Swart, Erica K. Towle, James S. Klaus, and Alan M. Piggot
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0106 biological sciences ,010504 meteorology & atmospheric sciences ,Climate Change ,Population Dynamics ,Scleractinia ,Biology ,01 natural sciences ,Porites astreoides ,Siderastrea radians ,Animals ,Environmental Chemistry ,Seawater ,Reef ,0105 earth and related environmental sciences ,General Environmental Science ,Global and Planetary Change ,geography ,geography.geographical_feature_category ,Ecology ,Coral Reefs ,Resilience of coral reefs ,010604 marine biology & hydrobiology ,fungi ,Global warming ,Coral reef ,Anthozoa ,biology.organism_classification ,Oceanography ,Caribbean Region ,Florida ,geographic locations ,Siderastrea siderea - Abstract
Anthropogenic climate change compromises reef growth as a result of increasing temperatures and ocean acidification. Scleractinian corals vary in their sensitivity to these variables, suggesting species composition will influence how reef communities respond to future climate change. Because data are lacking for many species, most studies that model future reef growth rely on uniform scleractinian calcification sensitivities to temperature and ocean acidification. In order to address this knowledge gap, calcification of twelve common and understudied Caribbean coral species was measured for two months under crossed temperatures (27°C, 30.3°C) and CO2 partial pressures (pCO2) (400, 900, 1300 μatm). Mixed effects models of calcification for each species were then used to project community-level scleractinian calcification using Florida Keys reef composition data and IPCC AR5 ensemble climate model data. Three of the four most abundant species, Orbicella faveolata, Montastraea cavernosa, and Porites astreoides, had negative calcification responses to both elevated temperature and pCO2. In the business-as-usual CO2 emissions scenario, reefs with high abundances of these species had projected end-of-century declines in scleractinian calcification of >50% relative to present-day rates. Siderastrea siderea, the other most-common species, was insensitive to both temperature and pCO2 within the levels tested here. Reefs dominated by this species had the most stable end-of-century growth. Under more optimistic scenarios of reduced CO2 emissions, calcification rates throughout the Florida Keys declined
- Published
- 2016
- Full Text
- View/download PDF
8. Impacts of a Changing Earth on Microbial Dynamics and Human Health Risks in the Continuum between Beach Water and Sand
- Author
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Christopher D. Heaney, Zachery R. Staley, Alexandria B. Boehm, Luísa Jordão, Helena M. Solo-Gabriele, João Brandão, Christopher Staley, Warish Ahmed, Brian D. Badgley, Michael J. Sadowsky, Jean Pierre Nshimyimana, Jay M. Fleisher, Valerie J. Harwood, Laura J. Vogel, Lindsay Avolio, Asli Aslan, Clare Robinson, James S. Klaus, Erin M. Symonds, Julie L. Kinzelman, Kevan M. Yamahara, Päivi Meriläinen, Gregory T. Kleinheinz, Alan M. Piggot, Chelsea J. Weiskerger, Thomas A. Edge, Tarja Pitkänen, Mantha S. Phanikumar, and Richard L. Whitman
- Subjects
0106 biological sciences ,0208 environmental biotechnology ,02 engineering and technology ,010501 environmental sciences ,01 natural sciences ,Feces ,Sand ,Models ,Water Quality ,Waste Management and Disposal ,Water Science and Technology ,education.field_of_study ,Ecology ,Ecological Modeling ,Cumulative effects ,Pollution ,Água e Solo ,6. Clean water ,Habitat ,Pathogens ,Water Microbiology ,Swash ,Environmental Monitoring ,Environmental Engineering ,Climate Change ,Population ,Climate change ,Indicator bacteria ,Bathing Beaches ,Agentes Microbianos e Ambiente ,Extreme weather ,FIB ,Urbanization ,Humans ,Population growth ,Seawater ,Parasites ,14. Life underwater ,education ,0105 earth and related environmental sciences ,Civil and Structural Engineering ,010604 marine biology & hydrobiology ,Water Pollution ,fungi ,Fungi ,other ,Water ,Global change ,15. Life on land ,020801 environmental engineering ,13. Climate action ,Environmental science ,Water quality - Abstract
Humans may be exposed to microbial pathogens at recreational beaches via environmental sources, such as water, sand, and aerosols. Although infectious disease risk from exposure to waterborne pathogens has been an active area of research for decades, sand is a relatively unexplored reservoir of pathogens and fecal indicator bacteria (FIB). Beach sand and water habitats provide unique advantages and challenges to pathogen introduction, growth, and persistence, as well as continuous exchange between habitats. Models of FIB and pathogen fate and transport in sandy beach habitats can help predict the risk of infectious disease from recreational water use, but filling knowledge gaps such as decay rates and potential for microbial growth in beach habitats is necessary for accurate modeling. Climatic variability, whether natural or anthropogenically-induced, adds complexity to predictive modeling, but may increase human exposure to waterborne pathogens via extreme weather events, warming of water bodies and sea level rise in many regions. The popularity of human recreational beach activities, combined with predicted climate change scenarios, could amplify the risk of human exposure to pathogens and related illnesses. Other global change trends such as increased population growth and urbanization are expected to exacerbate contamination events and the predicted impacts of increasing levels of waterborne pathogens on human health. Such changes will alter microbial population dynamics in beach habitats, and will consequently affect the assumptions and relationships used in population models and quantitative microbial risk assessment (QMRA). Here, we discuss the literature on microbial population and transport dynamics in sand-water continuum habitats at beaches, how these dynamics can be modeled, and how climate change and other anthropogenic influences (e.g., land use, urbanization) should be considered when using and developing more holistic, beachshed-based models.
- Published
- 2019
9. Potential Impacts of PCBs on Sediment Microbiomes in a Tropical Marine Environment
- Author
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Hee Sook Kang, Elsayed M. Zahran, Ad Reniers, Naresh Kumar, Helena M. Solo-Gabriele, Adolfo Fernandez, Vassiliki H. Kourafalou, Sapna K. Deo, Leonidas G. Bachas, Sylvia Daunert, Michal Toborek, James S. Klaus, Piero R. Gardinali, and Alan M. Piggot
- Subjects
0301 basic medicine ,polychlorinated biphenyls ,microbiome ,Intertidal zone ,Ocean Engineering ,010501 environmental sciences ,01 natural sciences ,lcsh:Oceanography ,03 medical and health sciences ,lcsh:VM1-989 ,PCBs ,lcsh:GC1-1581 ,Relative species abundance ,0105 earth and related environmental sciences ,Water Science and Technology ,Civil and Structural Engineering ,Total organic carbon ,Shore ,geography ,geography.geographical_feature_category ,lcsh:Naval architecture. Shipbuilding. Marine engineering ,food and beverages ,Sediment ,hydrodynamics ,transport ,marine sediments ,030104 developmental biology ,Oceanography ,Microbial population biology ,Tropical marine climate ,Environmental science ,Bay - Abstract
Within the tropical marine study site of Guánica Bay, Puerto Rico, polychlorinated biphenyls (PCBs) are subjected to coastal and oceanic currents coupled with marine microbial and geochemical processes. To evaluate these processes a hydrodynamic model was developed to simulate the transport of PCBs within nearshore and offshore marine areas of Guánica Bay. Material transport and circulation information from the model were matched with measurements from samples collected from within the bay. These samples, consisting of both intertidal and submerged sediments, were analyzed for physical characteristics (organic carbon, grain size, and mineralogy), microbial characteristics (target bacteria levels and microbial community analyses), presence of PCBs, and PCB-degrading enzymes. Results show that the bay geometry and bathymetry limit the mixing of the extremely high levels of PCBs observed in the eastern portion of the bay. Bay bottom sediments showed the highest levels of PCBs and these sediments were characterized by high organic carbon content and finer grain size. Detectable levels of PCBs were also observed within sediments found along the shore. Microbes from the bay bottom sediments showed a greater relative abundance of microbes from the Chloroflexi, phylum with close phylogenetic associations with known anaerobic PCB-degrading organisms. Based on quantitative PCR measurement of the biphenyl dioxygenase gene, the intertidal sediments showed the greatest potential for aerobic PCB degradation. These results elucidate particular mechanisms of PCB’s fate and transport in coastal, tropical marine environments.
- Published
- 2016
- Full Text
- View/download PDF
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