Assessing Fracture Connectivity using Stable and Clumped Isotope Geochemistry of Calcite Cements

Understanding flow path connectivity within a geothermal reservoir is a critical component for efficiently producing sustained flow rates of hot fluids from the subsurface. I present a new approach for characterizing subsurface fracture connectivity that combines petrographic and cold cathodoluminescence (CL) microscopy with stable isotope analysis (δ18O and δ13C) and clumped isotope (Δ47) thermometry of fracture-filling calcite cements from a geothermal reservoir in northern Nevada. Calcite cement samples were derived from both drill cuttings and core samples taken at various depths from wells within the geothermal field. CL microscopy of some fracture filling cements shows banding parallel to the fracture walls as well as brecciation, indicating that the cements are related to fracture opening and fault slip. Variations in trace element composition indicated by the luminescence patterns reflect variations in the composition and source of fluids moving through the fractures as they opened episodically. Calcite δ13C and δ18O results also show significant variation among the sampled cements, reflecting multiple generations of fluids and fracture connectivity. Clumped isotope analyses performed on a subset of the cements analyzed for conventional δ18O and δ13C mostly show calcite growth temperatures around 150°C—above the current ambient rock temperature, which indicates a common temperature trend for the geothermal reservoir. However, calcite cements sampled along faults located within the well field showed both cold (18.7°C) and hot (226.1°C) temperatures. The anomalously cool temperature found along the fault, using estimates from clumped isotope thermometry, suggests a possible connection to surface waters for the geothermal source fluids for this system. This information may indicate that some of the faults within the well field are transporting meteoric water from the surface to be heated at depth, which then is circulated through a complex network of fractures and other faults.

Observed oxygen concentrations and a possible implication behind the Muchalat inlet subsurface oxygen maximum

Senior thesis written for Oceanography 445

Behavior analysis of oithona in hypoxic/anoxic conditions

Senior thesis written for Oceanography 445

Occurrence and elimination of cyanobacterial toxins in two Australian drinking water treatment plants

In Australian freshwaters, Anabaena circinalis, Microcystis spp. and Cylindrospermopsis raciborskii are the dominant toxic cyanobacteria. Many of these Surface waters are used as drinking water resources. Therefore, the National Health and Medical Research Council of Australia set a guideline for MC-LR toxicity equivalents of 1.3 mug/l drinking, water. However, due to lack of adequate data, no guideline values for paralytic shellfish poisons (PSPs) (e.g. saxitoxins) or cylindrospermopsin (CYN) have been set. In this spot check. the concentration of microcystins (MCs), PSPs and CYN were determined by ADDA-ELISA, cPPA, HPLC-DAD and/or HPLC-MS/MS, respectively, in two water treatment plants in Queensland/Australia and compared to phytoplankton data collected by Queensland Health, Brisbane. Depending on the predominant cyanobacterial species in a bloom, concentrations of up to 8.0, 17.0 and 1.3 mug/l were found for MCs, PSPs and CYN, respectively. However, only traces (< 1.0 mug/l) of these toxins were detected in final water (final product of the drinking water treatment plant) and tap water (household sample). Despite the low concentrations of toxins detected in drinking water, a further reduction of cyanobacterial toxins is recommended to guarantee public safety. (C) 2004 Elsevier Ltd. All rights reserved.

Application of a novel phytotoxicity assay for the detection of herbicides in Hervey Bay and the Great Sandy Straits

A novel phytotoxicity assay was incorporated into an environmental assessment of Hervey Bay and the Great Sandy Straits, to investigate the role of run-off associated herbicides in the deteriorated health of intertidal seagrass meadows. Dose response curves of common herbicides were performed and their toxicity equivalents elucidated to assist in analysis. The results of the assay were reproducible and corresponded strongly with results of chemical analyses. The incorporation of the assay into the assessment of surface waters added an important aspect to the study by allowing investigation of the toxicity of cumulative herbicide concentrations and yielding biologically relevant data. The highest herbicide concentration detected during the study was equivalent to 0.23 mu g 1(-1) diuron; a concentration known to inhibit photosynthetic efficiency of the assay biomaterial by approximately 3%. (c) 2004 Elsevier Ltd. All rights reserved.

Herbicide contamination and the potential impact to seagrass meadows in Hervey Bay, Queensland, Australia

Low concentrations of herbicides (up to 70 ng 1(-1)), chiefly diuron (up to 50 ng 1 (-1)) were detected in surface waters associated with inter-tidal seagrass meadows of Zostera muelleri in Hervey Bay, south-cast Queensland, Australia. Diuron and atrazine (up to 1. 1 ng g(-1) dry weight of sediment) were detected in the sediments of these seagrass meadows. Concentration of the herbicides diuron, simazine and atrazine increased in surface waters associated with seagrass meadows during moderate river flow events indicating herbicides were washed from the catchment to the marine environment. Maximum herbicide concentration (sum of eight herbicides) in the Mary River during a moderate river flow event was 4260 ng 1(-1). No photosynthetic stress was detected in seagrass in this study during low river flow. However, with moderate river flow events, nearshore seagrasses are at risk of being exposed to concentrations of herbicides that are known to inhibit photosynthesis. (c) 2004 Elsevier Ltd. All rights reserved.

Nitrogen, phosphorus, silica, and carbon in Moreton Bay, Queensland, Australia: Differential limitation of phytoplankton biomass and production

Subtropical estuaries have received comparatively little attention in the study of nutrient loading and subsequent nutrient processing relative to temperate estuaries. Australian estuaries are particularly susceptible to increased nutrient loading and eutrophication, as 75% of the population resides within 200 km of the coastline. We assessed the factors potentially limiting both biomass and production in one Australian estuary, Moreton Bay, through stoichiometric comparisons of nitrogen (N), phosphorus (P), silicon (Si), and carbon (C) concentrations, particulate compositions, and rates of uptake. Samples were collected over 3 seasons in 1997-1998 at stations located throughout the bay system, including one riverine endmember site. Concentrations of all dissolved nutrients, as well as particulate nutrients and chlorophyll, declined 10-fold to 100-fold from the impacted western embayments to the eastern, more oceanic-influenced regions of the bay during all seasons. For all seasons and all regions, both the dissolved nutrients and particulate biomass yielded N : P ratios < 6 and N : Si ratios < 1. Both relationships suggest strong limitation of biomass by N throughout the bay. Limitation of rates of nutrient uptake and productivity were more complex. Low C : N and C : P uptake ratios at the riverine site suggested light limitation at all seasons, low N : P ratios suggested some degree of N limitation and high N : Si uptake ratios in austral winter suggested Si limitation of uptake during that season only. No evidence of P limitation of biomass or productivity was evident.

Valutazione del rischio ecologico e sviluppo di strategie innovative per il monitoraggio della qualita’ dei corpi idrici: applicazione di un nuovo approccio integrato in un bacino pilota.

Freshwater is extremely precious; but even more precious than freshwater is clean freshwater. From the time that 2/3 of our planet is covered in water, we have contaminated our globe with chemicals that have been used by industrial activities over the last century in a unprecedented way causing harm to humans and wildlife. We have to adopt a new scientific mindset in order to face this problem so to protect this important resource. The Water Framework Directive (European Parliament and the Council, 2000) is a milestone legislative document that transformed the way that water quality monitoring is undertaken across all Member States by introducing the Ecological and Chemical Status. A “good or higher” Ecological Status is expected to be achieved for all waterbodies in Europe by 2015. Yet, most of the European waterbodies, which are determined to be at risk, or of moderate to bad quality, further information will be required so that adequate remediation strategies can be implemented. To date, water quality evaluation is based on five biological components (phytoplankton, macrophytes and benthic algae, macroinvertebrates and fishes) and various hydromorphological and physicochemical elements. The evaluation of the chemical status is principally based on 33 priority substances and on 12 xenobiotics, considered as dangerous for the environment. This approach takes into account only a part of the numerous xenobiotics that can be present in surface waters and could not evidence all the possible causes of ecotoxicological stress that can act in a water section. The mixtures of toxic chemicals may constitute an ecological risk not predictable on the basis of the single component concentration. To improve water quality, sources of contamination and causes of ecological alterations need to be identified. On the other hand, the analysis of the community structure, which is the result of multiple processes, including hydrological constrains and physico-chemical stress, give back only a “photograph” of the actual status of a site without revealing causes and sources of the perturbation. A multidisciplinary approach, able to integrate the information obtained by different methods, such as community structure analysis and eco-genotoxicological studies, could help overcome some of the difficulties in properly identifying the different causes of stress in risk assessment. In synthesis, the river ecological status is the result of a combination of multiple pressures that, for management purposes and quality improvement, have to be disentangled from each other. To reduce actual uncertainty in risk assessment, methods that establish quantitative links between levels of contamination and community alterations are needed. The analysis of macrobenthic invertebrate community structure has been widely used to identify sites subjected to perturbation. Trait-based descriptors of community structure constitute a useful method in ecological risk assessment. The diagnostic capacity of freshwater biomonitoring could be improved by chronic sublethal toxicity testing of water and sediment samples. Requiring an exposure time that covers most of the species’ life cycle, chronic toxicity tests are able to reveal negative effects on life-history traits at contaminant concentrations well below the acute toxicity level. Furthermore, the responses of high-level endpoints (growth, fecundity, mortality) can be integrated in order to evaluate the impact on population’s dynamics, a highly relevant endpoint from the ecological point of view. To gain more accurate information about potential causes and consequences of environmental contamination, the evaluation of adverse effects at physiological, biochemical and genetic level is also needed. The use of different biomarkers and toxicity tests can give information about the sub-lethal and toxic load of environmental compartments. Biomarkers give essential information about the exposure to toxicants, such as endocrine disruptor compounds and genotoxic substances whose negative effects cannot be evidenced by using only high-level toxicological endpoints. The increasing presence of genotoxic pollutants in the environment has caused concern regarding the potential harmful effects of xenobiotics on human health, and interest on the development of new and more sensitive methods for the assessment of mutagenic and cancerogenic risk. Within the WFD, biomarkers and bioassays are regarded as important tools to gain lines of evidence for cause-effect relationship in ecological quality assessment. Despite the scientific community clearly addresses the advantages and necessity of an ecotoxicological approach within the ecological quality assessment, a recent review reports that, more than one decade after the publication of the WFD, only few studies have attempted to integrate ecological water status assessment and biological methods (namely biomarkers or bioassays). None of the fifteen reviewed studies included both biomarkers and bioassays. The integrated approach developed in this PhD Thesis comprises a set of laboratory bioassays (Daphnia magna acute and chronic toxicity tests, Comet Assay and FPG-Comet) newly-developed, modified tacking a cue from standardized existing protocols or applied for freshwater quality testing (ecotoxicological, genotoxicological and toxicogenomic assays), coupled with field investigations on macrobenthic community structures (SPEAR and EBI indexes). Together with the development of new bioassays with Daphnia magna, the feasibility of eco-genotoxicological testing of freshwater and sediment quality with Heterocypris incongruens was evaluated (Comet Assay and a protocol for chronic toxicity). However, the Comet Assay, although standardized, was not applied to freshwater samples due to the lack of sensitivity of this species observed after 24h of exposure to relatively high (and not environmentally relevant) concentrations of reference genotoxicants. Furthermore, this species demonstrated to be unsuitable also for chronic toxicity testing due to the difficult evaluation of fecundity as sub-lethal endpoint of exposure and complications due to its biology and behaviour. The study was applied to a pilot hydrographic sub-Basin, by selecting section subjected to different levels of anthropogenic pressure: this allowed us to establish the reference conditions, to select the most significant endpoints and to evaluate the coherence of the responses of the different lines of evidence (alteration of community structure, eco-genotoxicological responses, alteration of gene expression profiles) and, finally, the diagnostic capacity of the monitoring strategy. Significant correlations were found between the genotoxicological parameter Tail Intensity % (TI%) and macrobenthic community descriptors SPEAR (p<0.001) and EBI (p<0.05), between the genotoxicological parameter describing DNA oxidative stress (ΔTI%) and mean levels of nitrates (p<0.01) and between reproductive impairment (Failed Development % from D. magna chronic bioassays) and TI% (p<0.001) as well as EBI (p<0.001). While correlation among parameters demonstrates a general coherence in the response to increasing impacts, the concomitant ability of each single endpoint to be responsive to specific sources of stress is at the basis of the diagnostic capacity of the integrated approach as demonstrated by stations presenting a mismatch among the different lines of evidence. The chosen set of bioassays, as well as the selected endpoints, are not providing redundant indications on the water quality status but, on the contrary, are contributing with complementary pieces of information about the several stressors that insist simultaneously on a waterbody section providing this monitoring strategy with a solid diagnostic capacity. Our approach should provide opportunities for the integration of biological effects into monitoring programmes for surface water, especially in investigative monitoring. Moreover, it should provide a more realistic assessment of impact and exposure of aquatic organisms to contaminants. Finally this approach should provide an evaluation of drivers of change in biodiversity and its causalities on ecosystem function/services provision, that is the direct and indirect contributions to human well-being.

Occurrence and environmental fate of Irgarol 1051, a new antifouling agent

The purpose of this study is to characterize the degradation products of Irgarol 1051(2-methylthio-4-tertbutylamino-6-cyclopropylamino- s-triazine), a compound recently developed for use as an antifouling agent on boat hulls. The photolytic fate of this compound in different natural waters will be used in the development of a monitoring program designed to survey the occurrence of this compound and its degradation products in South Florida marinas, the Miami River and surrounding coastal areas. ^ The transformation of Irgarol 1051 and degradation rate constants were characterized in a photo-reactor under simulated natural conditions. The degradation pathway in the UVB-UVA region (300nm to 350nm) closely resembled the transformations under natural conditions in the pond, showing that both direct photolysis and the presence of natural sensitizers play an important role in the abiotic transformation of this compound. Irgarol 1051 has an average environmental half-life of 10 days in surface waters. Average concentrations from samples around Biscayne Bay and the Miami River increased from 1–5 ng/L during 1999 and increased to between 28 and 38 ng/L in 2001, respectively. Irgarol concentrations showed a strong correlation with concentrations of its major transformation product, M1, from samples collected as part of the study ([M1]/[Irgarol] = 0.247, R2 = 0.9165, n = 125). ^

Assessing the sources, quantities, and trends on human waste contamination along protected south Florida ecosystem: A chemical tracer based study

The common occurrence of human derived contaminants like pharmaceuticals, steroids and hormones in surface waters has raised the awareness of the role played by the release of treated or untreated sewage in the water quality along sensitive coastal ecosystems. South Florida is home to many important protected environments ranging from wetlands to coral reefs which are in close proximity to large metropolitan cities. Since large portions of South Florida and most of the Florida Keys population are not served by modern sewage treatment plants and rely heavily on the use of inefficient septic systems; a comprehensive survey of selected human waste contamination markers is needed in these areas to assess water quality with respect to non-traditional micro-constituents. ^ This study reports the development and application of new sensitive and selective analytical methods for the fast screening of multiple wastewater tracers, classified as Emergent Pollutants of Concern (EPOC). Novel methods for the trace analysis of non-traditional markers of human-specific contamination such as aminopropanone were developed and used to assess the potential of non-traditional markers as wastewater tracers. ^ During our investigation, surface water samples collected from near shore environments along the South Florida were analyzed for fifteen hormones and steroids, and five commonly detected pharmaceuticals. The compounds most frequently detected were: coprostanol, cholesterol, estrone, β-estradiol, caffeine, triclosan and DEET. Concentrations of caffeine, bisphenol A and DEET were usually higher and more prevalent than the hormonal steroids. In general, it was found that common pharmaceuticals and steroids are widely present in major coastal environments in South Florida. It is also evident that aquatic bodies in heavily urbanized sectors such as the Miami River and Key Largo Harbor contain higher concentrations of several compounds while relatively open bay waters and agricultural areas show reduced chemical signatures. Concentrations of hormones in the Little Venice area of Marathon Key were above the Lowest Observable Effect Levels (LOELs) for several species, indicating that biological resources in this area are at risk. Water quality issues in some of these coastal water environments go beyond eutrophication, thus EPOC should be the target goal for future mitigation projects. ^

Biogeochemical effects of iron availability on primary producers in a shallow marine carbonate environment

We completed a synoptic survey of iron, phosphorus, and sulfur concentrations in shallow marine carbonate sediments from south Florida. Total extracted iron concentrations typically were 50 μmol g-1 dry weight (DW) and tended to decrease away from the Florida mainland, whereas total extracted phosphorus concentrations mostly were 10 μmol g-1 DW and tended to decrease from west to east across Florida Bay. Concentrations of reduced sulfur compounds, up to 40 μmol g-1 DW, tended to covary with sediment iron concentrations, suggesting that sulfide mineral formation was iron-limited. An index of iron availability derived from sediment data was negatively correlated with chlorophyll a concentrations in surface waters, demonstrating the close coupling of sediment-water column processes. Eight months after applying a surface layer of iron oxide granules to experimental plots, sediment iron, phosphorus, and sulfur were elevated to a depth of 10 cm relative to control plots. Biomass of the seagrass Thalassia testudinum was not different between control and iron addition plots, but individual shoot growth rates were significantly higher in experimental plots after 8 months. Although the iron content of leaf tissues was significantly higher from iron addition plots, no difference in phosphorus content of T. testudinum leaves was observed. Iron addition altered plant exposure to free sulfide, documented by a significantly higher δ34S of leaf tissue from experimental plots relative to controls. Iron as a buffer to toxic sulfides may promote individual shoot growth, but phosphorus availability to plants still appears to limit production in carbonate sediments.

Spatial, geomorphological, and seasonal variability of CDOM in estuaries of the Florida Coastal Everglades

This paper demonstrates the usefulness of fluorescence techniques for long-term monitoring and assessment of the dynamics (sources, transport and fate) of chromophoric dissolved organic matter (CDOM) in highly compartmentalized estuarine regions with non-point water sources. Water samples were collected monthly from a total of 73 sampling stations in the Florida Coastal Everglades (FCE) estuaries during 2001 and 2002. Spatial and seasonal variability of CDOM characteristics were investigated for geomorphologically distinct sub-regions within Florida Bay (FB), the Ten Thousand Islands (TTI), and Whitewater Bay (WWB). These variations were observed in both quantity and quality of CDOM. TOC concentrations in the FCE estuaries were generally higher during the wet season (June–October), reflecting high freshwater loadings from the Everglades in TTI, and a high primary productivity of marine biomass in FB. Fluorescence parameters suggested that the CDOM in FB is mainly of marine/microbial origin, while for TTI and WWB a terrestrial origin from Everglades marsh plants and mangroves was evident. Variations in CDOM quality seemed mainly controlled by tidal exchange/mixing of Everglades freshwater with Florida Shelf waters, tidally controlled releases of CDOM from fringe mangroves, primary productivity of marine vegetation in FB and diagenetic processes such as photodegradation (particularly for WWB). The source and dynamics of CDOM in these subtropical estuaries is complex and found to be influenced by many factors including hydrology, geomorphology, vegetation cover, landuse and biogeochemical processes. Simple, easy to measure, high sample throughput fluorescence parameters for surface waters can add valuable information on CDOM dynamics to long-term water quality studies which can not be obtained from quantitative determinations alone.

Regional climate gradients in precipitation and temperature in response to climate teleconnections in the Greater Everglades ecosystem of South Florida

Precipitation and temperature in Florida responds to climate teleconnections from both the Pacific and Atlantic regions. In this region south of Lake Okeechobee, encompassing NWS Climate Divisions 5, 6, and 7, modern movement of surface waters are managed by the South Florida Water Management District and the US Army Corps of Engineers for flood control, water supply, and Everglades restoration within the constraints of the climatic variability of precipitation and evaporation. Despite relatively narrow, low-relief, but multi-purposed land separating the Atlantic Ocean from the Gulf of Mexico, South Florida has patterns of precipitation and temperature that vary substantially on spatial scales of 101–102 km. Here we explore statistically significant linkages to precipitation and temperature that vary seasonally and over small spatial scales with El Niño-Southern Oscillation (ENSO), the Atlantic Multidecadal Oscillation (AMO), and the Pacific Decadal Oscillation (PDO). Over the period from 1952 to 2005, ENSO teleconnections exhibited the strongest influence on seasonal precipitation. The Multivariate ENSO Index was positively correlated with winter (dry season) precipitation and explained up to 34 % of dry season precipitation variability along the southwest Florida coast. The AMO was the most influential of these teleconnections during the summer (wet season), with significant positive correlations to South Florida precipitation. These relationships with modern climate parameters have implications for paleoclimatological and paleoecological reconstructions, and future climate predictions from the Greater Everglades system.

Phosphorus budgets in Everglades wetland ecosystems: the effects of hydrology and nutrient enrichment

The Florida Everglades is a naturally oligotrophic hydroscape that has experienced large changes in ecosystem structure and function as the result of increased anthropogenic phosphorus (P) loading and hydrologic changes. We present whole-ecosystem models of P cycling for Everglades wetlands with differing hydrology and P enrichment with the goal of synthesizing existing information into ecosystem P budgets. Budgets were developed for deeper water oligotrophic wet prairie/slough (‘Slough’), shallower water oligotrophic Cladium jamaicense (‘Cladium’), partially enriched C. jamaicense/Typha spp. mixture (‘Cladium/Typha’), and enriched Typha spp. (‘Typha’) marshes. The majority of ecosystem P was stored in the soil in all four ecosystem types, with the flocculent detrital organic matter (floc) layer at the bottom of the water column storing the next largest proportion of ecosystem P pools. However, most P cycling involved ecosystem components in the water column (periphyton, floc, and consumers) in deeper water, oligotrophic Slough marsh. Fluxes of P associated with macrophytes were more important in the shallower water, oligotrophic Cladium marsh. The two oligotrophic ecosystem types had similar total ecosystem P stocks and cycling rates, and low rates of P cycling associated with soils. Phosphorus flux rates cannot be estimated for ecosystem components residing in the water column in Cladium/Typha or Typha marshes due to insufficient data. Enrichment caused a large increase in the importance of macrophytes to P cycling in Everglades wetlands. The flux of P from soil to the water column, via roots to live aboveground tissues to macrophyte detritus, increased from 0.03 and 0.2 g P m−2 yr−1 in oligotrophic Slough and Cladium marsh, respectively, to 1.1 g P m−2 yr−1 in partially enriched Cladium/Typha, and 1.6 g P m−2 yr−1 in enriched Typha marsh. This macrophyte translocation P flux represents a large source of internal eutrophication to surface waters in P-enriched areas of the Everglades.

Origin of salinity variations in Florida Bay

This note presents a method of distinguishing the source of freshwater that causes reductions in salinity in the coastal environment of South Florida. This technique, which uses the 18O and D of the water, allows for differentiation of the freshwater derived from precipitation as opposed to runoff, because surface waters in the Everglades have been highly evaporated and therefore have elevated 18O and dD values relative to precipitation. A time series of monthly 18O and D values of surface waters, collected from stations in Florida Bay between 1993 and 1999, has shown that, during this time, the major source of freshwaters causing depressions in the salinity in the western portion of Florida Bay was derived from precipitation rather than from the runoff of water from the Everglades. In the eastern portion of Florida Bay, close to the boundary between peninsular Florida and the Bay, the proportion of freshwater derived from precipitation drops steadily, reaching <10%. This method not only allows differentiation between the sources of freshwater but can, in a temporal sense, ascertain the effectiveness of water management practices on the salinity of the estuarine ecosystems of South Florida.