<p> Sediment bioturbators play an important ecological role and may both be affected by contaminants in the sediment and affect the fate and distribution of these contaminants. This is especially important for the many contaminants, like lead, for which sediments serve as a sink upon the contaminants&rsquo; release into the environment. In this study, I investigated the toxicity of sediment Pb to a freshwater bioturbator, the effect of bioturbation on the environmental distribution of the Pb, the effect of sediment characteristics on the bioturbation-mediated transfer of Pb from the sediment to the water column, and this transfer&rsquo;s toxicological consequences for planktonic organisms. Experiments were conducted in microcosms with control sediment or Pb-spiked sediment, the freshwater oligochaete Lumbriculus variegatus served as the model bioturbator, and the water flea Daphnia magna served as the model planktonic organism. The rate of bioturbation of the oligochaete was quantified using luminophores. </p><p> The bioturbation resulted in the transfer of Pb from the sediment to the water column. However, it did not affect Pb levels in the worm tissue or in the sediment. The environmental distribution of Pb among water column, biota, and sediment in the presence of the bioturbator was dependent on sediment characteristic like organic content, silt/clay content, and the pH of the sediment. Bioturbation by L. variegatus increased bioaccumulation of Pb in D. magna; however, this Pb had no toxic effect on survival, reproduction, and biomass of D. magna under the specific conditions used here. Quantification of the bioturbation rates of L. variegatus showed that the intensity of the bioturbation was enhanced at higher densities of the oligochaete but reduced at high sedimentary Pb concentrations. Overall this study demonstrated that bioturbation by L. variegatus can transfer Pb from the sediment to the water column, and that this transfer is dependent on sediment characteristics. The Pb transferred as a result of the bioturbation can enhance Pb availability to organisms in the water column, and potentially cause toxic effects in these organisms.</p>

A project report submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in partial fulfillment of the requirements for the degree Masters of Science Resource Conservation Biology. / An understanding of the biogeochemistry of carbon and nitrogen in ecosystems is necessary for the sustainability of system function. Transformations, including different land uses, disrupt the natural input:output of soil organic matter and often result in changes in the cycling of carbon and nitrogen. Consequently it is imperative to know how different land uses are likely to alter the pool sizes, flux rates and turnover of carbon and nitrogen in the soil. The savanna and grassland biomes of South Africa include large areas which have been transformed by man and are the main sites of primary and secondary production. Sites in these biomes along a vegetation and soil type gradient have been investigated. Soil samples from a conserved area, a cultivated area and a livestock area have been sampled. A range of soil properties including the potential rate of nitrogen mineralization, total soil carbon and nitrogen, microbial carbon and nitrogen, soil texture, bulk density. pH and standing dead herbaceous biomass have been quantified. These along with values reported in the literature have been used to validate the CENTURY model, which simulates the turnover of ecosystem attributes on the basis of soil organic matter inputs and outputs. Results show that the soil organic matter pool sizes for the sites and land uses were positively correlated with the percentage fines (silt-plus-clay) and site aridity. Sites which were moist and had a percentage of fines greater than 45% tended to have 3 times more C and N. Land use, especially cultivation, reduced the amount of SOM at sites by 50% mainly because of the effects on the light fraction mass. The potential rate of N mineralization was not significantly different between sites but the cultivated land use led to the immobilization of N. Possible reasons for this included the negative impact that cultivation has on soil macroaggregates, the lower <1.0 glkg) input of light fraction, and the low <10%) percentage fines at these sites. Simulations of the SOM fractions using the CENTURY model for six functional types indicate that similar trends emerged but the model greatly overestimated absolute amounts of SOM. In conclusion, the absolute quantities of soil carbon and nitrogen are influenced by climate, soil texture, and land use; but the proportion of soil organic matter fractions do not appear to differ per biome or per land use indicating similar turnover times. / AC 2018

The Greenland Ice Sheet (GrIS) is melting at an alarming rate. Supraglacial melt water flows into moulins that drain to the base of the ice sheet, and enhances basal flow. Ultimately, large quantities of melt water are expelled into the ocean contributing to rising sea level, as well as nutrient fertilization of the North Atlantic Ocean. The presence of residual melt water in a warm-based polythermal glacier creates conditions for chemical weathering of the subglacial till which is expected to lead to a higher dissolved load in the basal melt water. Supraglacial melt arriving during the start of the melting season flushes out the basal melt water. Despite this important window, little work has been done to measure trace element concentrations in the early melt season. To examine the effect of supraglacial melt water input on the chemistry of basal melt waters, we performed a time series of supraglacial and proglacial sampling collected daily for four weeks at the start of the melt season in 2016 in southwest Greenland following GEOTRACES trace element-clean protocols. Briefly, glacial melt water samples were vacuum-filtered through 0.45 um acid-washed Supor filters under Class-10 HEPA-filtered laminar air flow and analyzed for major and trace element concentrations by High Resolution Inductively Coupled Plasma Mass Spectrometry (HR-ICP-MS). The daily sampling regime captured trace element concentrations throughout the first seasonal pulse of melt water discharge. Concentrations of a variety of trace elements, including Ba, Mg, Mn, and Sr, closely followed the melt water discharge pulse, increasing in concentration during the main pulse event (which lasted <5 days). The abundances of REEs and Fe exhibited no discernable temporal relationship, however Fe concentrations fell between 15-120 ppb, below a recent study implying that the melting GrIS is a significant source of bioavailable Fe. Also notable is that toxic metals never exceeded EPA primary and secondary drinking water quality standards, even during the pulse peak, demonstrating the potential of seasonal glacial melt waters as viable sources of drinking water. / A Thesis submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the Master of Science. / Summer Semester 2017. / July 19, 2017. / Chemistry, Greenland, Pulse, Seasonal, Water, Weathering / Includes bibliographical references. / Munir Humayun, Professor Co-Directing Thesis; Peter Morton, Professor Co-Directing Thesis; Vincent Salters, Committee Member; Robert Spencer, Committee Member.

Globally, karst ecosystems are experiencing anthropogenic impacts due to their high hydrologic connectivity, leading to issues including increasing color (browning) as noted in recent decades at the largest freshwater spring on Earth (Wakulla Springs, Florida, USA). Wakulla Springs is located within a karst landscape, characterized by numerous sinkholes connecting surface and groundwaters. Surface waters and associated dissolved organic matter (DOM) from both natural sources (e.g. Apalachicola National Forest) and anthropogenic sources (e.g. municipal wastewater facility, sprayfield farm and diffuse inputs from the city of Tallahassee) are transported through these features and discharged at Wakulla Springs’ vent. In this study we assess dissolved organic matter (DOM) composition via absorbance and fluorescence spectroscopy and Fourier Transform ion cyclotron mass spectrometry (FT-ICR MS) to evaluate seasonal changes in DOM composition and dissolved organic carbon (DOC) concentration. Samples were collected between August 2015 and August 2016, bi-weekly, at three wells and two fluvial sites throughout Wakulla Springs State Park. These wells represent conduits feeding from different locations in the springshed, encompassing the major inputs and sources of DOM to the Spring vent and downstream Wakulla River. Sample sites separated into distinct groups based on DOC concentration and optical and FT-ICR MS parameters indicative of autochthonous (clear groundwater) versus allochthonous (terrestrial) DOM. Seasonal trends in DOM composition at Wakulla Springs vent are apparent and predominantly driven by high precipitation events and associated inputs of DOM from the Apalachicola National Forest with increased color, DOC, and terrestrially sourced molecular signatures. Principle component analysis highlights the ability of optical parameters to show the dominance of sample sites draining from the southwest (i.e. Apalachicola National Forest) as responsible for the color rich water at the vent, whereas water draining from the north was comparatively clear. Multivariate analyses demonstrates how FT-ICR MS can clearly distinguish the molecular signatures of clear groundwaters and afforested blackwater inputs, and emphasize the dominance of conduits draining from afforested sites as controlling the DOM signature and associated color at the vent. Despite the hydrologic complexity of the aquifer, FT-ICR MS allowed for clear discrimination between the different DOM sources and so these methodologies may be applied to aquifers around the world to trace inputs and evolved signatures. Increasing colored rich waters at the vent suggests that either input from conduits draining from the southwest have increased, or the relative dilution with clear groundwater has decreased in the conduit system prior to discharge from the vent. Sea-level rise impacts in the region have been suggested to result in more blackwaters delivered to the vent, and ongoing extraction of clear groundwater reduces the dilution capacity on color rich waters. Thus, anthropogenic impacts in the region need to be addressed if the trend of increased colored inputs at Wakulla Springs is to be reversed. / A Thesis submitted to the Department of Earth, Ocean and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science. / Spring Semester 2018. / March 28, 2018. / Absorbance, Biogeochemistry, Dissolved Organic Matter, Fluorescence, Fourier Transform ion cyclotron resonance mass spectrometry, Freshwater Springs / Includes bibliographical references. / Robert Spencer, Professor Directing Thesis; Jeffrey Chanton, Committee Member; Mariana M. P. B. Fuentes, Committee Member.

Karenia brevis is a marine dinoflagellate commonly found in the Gulf of Mexico and important both ecologically and economically due to its production of the neurotoxin brevetoxin, which can cause respiratory illness in humans and widespread death of marine animals. K. brevis strains have previously shown to be sensitive to changes in CO2, both in terms of growth as well as toxin production. Our study aimed to understand this sensitivity by measuring underlying mechanisms, such as photosynthesis, carbon acquisition, and photophysiology. K. brevis (CCFWC-126) did not show a significant response in growth, cellular composition of carbon and nitrogen, nor in photosynthetic rates between pCO2 concentrations of 150, 400 or 780 µatm. However, a strong response in its acquisition of inorganic carbon was found. Half saturation values for CO2 increased from 1.5 to 3.3 µM, inorganic carbon preference switched from HCO3- to CO2 (14% to 56% CO2 usage), and external carbonic anhydrase activity was downregulated by 23% when comparing low and high pCO2. We conclude that K. brevis must employ an efficient and regulated carbon concentration mechanism (CCM) to maintain constant carbon fixation and growth across pCO2 levels. A positive correlation with pCO2, although not statistically significant, in cellular brevetoxin content was found. This study is the first explaining how this socioeconomically important species is able to efficiently supply inorganic carbon for photosynthesis which can potentially prolong bloom situations. This study also highlights that enhanced CO2, as projected for a future ocean, can affect underlying physiological processes of K. brevis, some of which could lead to increases in cellular brevetoxin production and therefore increased impacts on coastal ecosystems and economies. / A Thesis submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science. / Fall Semester 2018. / September 17, 2018. / Brevetoxins, Carbon Concentrating Mechanism, Climate Change, Ocean Acidification, Photosynthesis, Red Tides / Includes bibliographical references. / Sven Kranz, Professor Directing Thesis; Angela Knapp, Committee Member; Olivia Mason, Committee Member; Michael Stukel, Committee Member; Janie Wulff, Committee Member.

The aeolian transport of aerosols (mineral dust from desert areas, smoke and ash from biomass burning, and from anthropogenic emissions) is an important process for introducing bioactive trace elements to the surface ocean and can have a large impact on marine primary production. All material that enters the ocean from the atmosphere must pass through the air-sea interface, or sea surface microlayer. The microlayer is the physical link between the sea surface and lower atmosphere and is therefore tied to the global biogeochemical cycling of trace elements. The microlayer (50 – 200 µm thickness) is a unique environment with different physical, chemical, and biological properties compared to the underlying water column. The microlayer is dynamic in nature due to numerous non-equilibrium processes such as temperature fluctuations, salinity gradients, irradiance, and wind and wave actions that influence its biogeochemical properties. However, the microlayer is mechanically more stable than the underlying water column due to the higher concentration of surface-active organic compounds; creating a more rigid film-like layer over the surface of the ocean. It is an important, yet often ignored component in the biogeochemical cycling of trace elements in the marine environment due to the lack of trace element clean sampling and analysis methods. A novel technique, a hollow cylinder of ultra-pure SiO₂ (quartz glass) with a plastic handle, was developed to sample the microlayer for trace elements. This research also developed and optimized clean trace element techniques to accurately measure nine trace metals (Al, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb) in the dissolved and particulate fractions of the microlayer and underlying water column. Initially, our research focused on the behavior of dissolved and particulate Al, Mn, Fe, Co, Cu, Zn, Cd, and Pb in the microlayer in a controlled tank experiment using a Saharan dust source. The residence times of the dissolved trace elements ranged from 1.8 hours for Fe to 15 hours for Cd. The residence times for the particulate trace elements ranged from 1.0 minutes for Al and Fe to 1.4 minutes for Mn. There was an initial release of dissolved trace elements to the microlayer from the Saharan dust. However, the reactive fraction of the suspended particles increased over time, indicative of scavenging. Based on the artificial dust deposition experiment, aerosols should be retained in the sea surface microlayer long enough to undergo chemical and physical alteration that affects the bioavailability of trace elements. Opportunistic bacteria (example: Vibrio spp.) have been shown to experience rapid growth during dust deposition events. Aerosols and microlayer samples were collected in the Florida Keys over the course of two years for analysis of dissolved and particulate Al, Mn, Fe, Co, Ni, Cu, Zn, and Pb. Trace element concentrations increased by factors of 2 to 5 in the microlayer during significant Saharan dust events. Residence times of dissolved trace elements ranged from 0.12 hours for Mn to 2.4 hours for Cu. Residence times of particulate trace elements ranged from 1.1 minutes for Co to 2.4 minutes for Mn. The particulate residence times were comparable between the artificial deposition experiment and the natural deposition event observed in the Florida Keys. The relatively short residence times for dissolved trace elements compared to the artificial deposition event suggest external forces, such as wind and wave actions, mixed the dissolved metals faster than by simple molecular diffusion. Despite the short residence times, Vibrio spp. in the microlayer increased by factors of 2 to 10 after the passage of a Saharan dust event, which suggests that there was an initial pulse of bioavailable trace elements and other nutrients to the system. These findings demonstrate the dynamic nature of the sea surface microlayer and the large role atmospheric deposition can play when introducing trace elements to the surface oceans. It also sheds light on the need for more interdisciplinary research to deconvolute and quantify the processes occurring in the microlayer. / A Dissertation submitted to the Department of Earth, Ocean and Atmospheric Science in partial fulfillment of the Doctor of Philosophy. / Fall Semester 2016. / December 9, 2016. / atmospheric deposition, sea surface microlayer, trace elements / Includes bibliographical references. / William M. Landing, Professor Directing Dissertation; Albert E. Stiegman, University Representative; Angela N. Knapp, Committee Member; Sven A. Kranz, Committee Member; Vincent J. M. Salters, Committee Member.

The solution speciation and solid-phase suspended particulate fractionation of the trace metals Al, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb were investigated in the Black Sea, the world's largest anoxic basin. Sequential filtration/ion-exchange and selective leaching techniques were developed for the determination of dissolved and solid-phase trace metal fractionation. Field measurements were compared with the results of a thermodynamic equilibrium model. The transition metals (Mn, Fe, and Co) were controlled by changes in redox state across the oxic/suboxic/anoxic boundary and by metal-sulfide precipitation in the anoxic deep waters. Dissolved transition metal concentrations were low in the surface waters, increased to maxima in the upper anoxic zone, then decreased again into the deep waters. Dissolved Mn and Fe approached saturation with respect to MnS$\sb2$ (haurite) and to FeS (mackinawite) or Fe$\sb3$S$\sb4$ (greigite) in the deep waters. Dissolved Co was best explained in terms of a scavenging/regeneration cycle with Mn-oxyhydroxides across the sulfide interface and coprecipitation of Co with Fe-sulfides in the deep waters. Dissolved Ni was nearly constant with depth. / The Class B metals (Cu, Zn, Cd, and Pb) were high in the surface waters and decreased rapidly across the sulfide interface, consistent with metal-sulfide precipitation below the interface. The dissolved metal fractionation was dominated in the oxic zone by "free" metal species, shifting to dissolved metal-sulfide complexes below the interface. / With the exceptions of Al and Fe, the suspended matter trace metal fractionation was dominated by weak-acid soluble forms. Strong-acid leachable forms, probably metal-sulfide phases, were important in the deep waters for Mn, Fe, and Co. / Source: Dissertation Abstracts International, Volume: 52-02, Section: B, page: 0705. / Major Professor: William M. Landing. / Thesis (Ph.D.)--The Florida State University, 1990.

Understanding the processes that govern terrestrial carbon fluxes and sequestration are fundamental to improving our understanding of climate feedbacks and ecosystem biogeochemistry. Biotic disturbances such as pest or pathogen attacks can have a large impact on forest carbon storage yet our knowledge of how these perturbations impact forest carbon cycling is limited. The goals of this dissertation were to gain insights into the processes governing soil respiration at Black Rock Forest (southeastern NY, USA) by quantifying the relative contributions of autotrophic and heterotrophic activity to soil respiration, to assess the short-term impact of mimicking a pathogen attack on soil carbon pools and fluxes, and to develop the first soil carbon budget for Black Rock Forest. These goals were addressed by utilizing a large-scale manipulative experiment, which induced tree mortality through girdling. Trees on twelve plots (75m by 75m) were girdled according to four treatments: girdling all oaks, girdling half of the oaks, girdling all non-oaks, and a control. Additionally, one circular plot was created where all trees were girdled. Soil respiration was measured before the girdling and for three years afterwards. Forest floor litter and soil organic carbon at five depth intervals were measured on all plots two years after girdling. The results from the first year of the experiment provided an initial estimate of 50% for the autotrophic component of soil respiration but continued declines in soil respiration rate into the second year provided a more accurate estimate of 58 %. Rapid declines in soil CO2 flux from the fully girdled plot (37%) and from the oaks girdled treatment (33%) within two weeks following girdling demonstrate a fast turnover of recently fixed carbon. The three-year time series of respiration measurements provided insights into the short-term impact of mimicking a pathogen attack on soil carbon fluxes. Respiratory rates on plots where all oaks, half of the oaks, and all trees were girdled declined for two years following treatment before attaining a full recovery of belowground activity in the third year. Soil respiration from the non-oak girdled treatment was similar to control for the duration of the study. The short-lived respiratory response on plots where all oaks, half of the oaks, and all trees were girdled suggests that belowground activity is highly resilient to disturbance. It also aligns with reported recovery patterns of net ecosystem production after a pest or pathogen attack. Overall, the reduction in soil respiration was not proportional to the degree of canopy loss, the magnitude of the respiratory response varied interannually, and was specific to the plant taxon impacted. No changes across treatments in soil organic carbon storage were observed two years after the mimicked attack. These findings do not support a recent hypothesis that suggests disturbance should reduce soil carbon pools (Peltzer et al. 2010). Instead, it is proposed that shifts in the composition of carbon substrates within the belowground carbon pool occurred and that the changes may offset each other. This could result in a similar quantity of soil carbon storage between the disturbed and undisturbed forest stands. The first estimate for soil carbon storage (to 30cm depth) at Black Rock Forest is 3.0 ± 0.5 kg C m-2, which is 32% of the aboveground carbon storage. Together, the findings from this dissertation contribute to the limited knowledge of respiratory partitioning and of short-term impacts on soil carbon storage and fluxes following a partial stand disturbance in northeastern deciduous forests.

<p> Nitrogen (N) fixing trees are commonly used to promote forest restoration in disturbed areas because they can quickly recreate forest canopy structure. That structure in turn is hypothesized to attract animal seed dispersers and create enough shade to reduce undesirable species (particularly grasses). Yet N-fixers tend to increase soil N availability, which could facilitate the spread of nitrophilous invasive species. This dissertation evaluates the long-term consequences for understory community composition of establishing three N-fixing tree species (<i>Acacia koa, Sophora chrysophylla</i>, and <i>Morella faya</i>) after exotic grass-fueled fire in the seasonally dry subtropical woodland in Hawaii. To understand the restoration potential of these species, I compared discrete single-species stands of N-fixing trees in burned areas to both an intact native woodland and burned, open sites with no tree cover. Although N-fixing species are often assumed to be ecologically similar, trait variation among N-fixing trees in this system was strong enough to differentiate understory communities among stands of the three N-fixer species. To understand the mechanisms driving differences in understory composition among site types, particularly among N-fixing trees, I characterized the abiotic environment created by these species in terms of light and N availability, both of which were important drivers of understory community composition. High light and N availability were associated with greater exotic species cover and unique exotic species. Surprisingly, N availability was highest and N cycled fastest beneath the relatively slow-growing <i>S. chrysophylla </i> despite having much lower litter-N inputs than the faster-growing <i> A. koa</i> and <i>M. faya</i>. In this study, fast N-cycling was associated with high specific leaf area, high foliar N content and low foliar lignin:N. These traits are consistent with fast leaf economic spectrum traits in the general ecological literature, but this approach has not previously been applied to distinguish among N-fixing trees. Native Hawaiian dry forest understory recovery, particularly that of woody species, was limited throughout the burned area regardless of canopy cover. To determine what limits native shrub recovery, I sampled the seed bank and recorded natural seedling germination. I also planted native seedlings into the understory of all site types and either removed or left intact the invasive grass grasses present in the understory. I found that native shrubs were limited by both seed availability and competition with exotic grasses. Although outplant survival did not vary by N-fixer species identity, differences in the mechanisms by which each N-fixing species limited native seedling survival likely play a role in understory community assembly long-term. When restoration occurs in the context of secondary succession, prioritizing the creation of forest structure using N-fixing trees, particularly open-canopied fast-cycling species, such as <i>S. chrysophylla</i>, could make full community recovery more difficult by promoting rather than suppressing exotic grasses.</p><p>

Sediments and pore waters from two urban estuaries ranging in sediment mixing energy were studied to evaluate the potential release of contaminants from particles during sediment diagenesis. Two sites in Elizabeth River, VA and two tributaries in the Hudson River Watershed were sampled for polycyclic aromatic hydrocarbons (PAHs). Sediment age, total sediment organic carbon (TOC), carbon to nitrogen (C/N) ratios, and particle surface area (SA) were also sampled at these sites. In the Elizabeth River, both sites sampled (Site 1 and Site 2) have been non-depositional for the past 70 y or are comprised of old dredge spoil. PAH K&\sp\prime\sb{lcub}\rm OC{rcub}&s were significantly higher at Site 2 than Site 1 indicating a different type of particle-PAH association at each site independent of the amount of TOC. Decreasing down-core K&\sp\prime\sb{lcub}\rm OC{rcub}&s at Site 1 coincided with down-core change in TOC accessible for PAH binding. at Site 2 in the Elizabeth River, high and uniform K&\sp\prime\sb{lcub}\rm OC{rcub}&s may have resulted from particles with PAHs entrapped by an organic coating. Deposition rates in the East River and Newark Bay were calculated to be &\sim&27 cm/y and &\sim&2 cm/y, respectively. Sediment PAH concentrations were significantly higher in the East River than Newark Bay, coincident with the higher amounts of TOC and SA in East River sediments. Low molecular weight PAHs were not detectable in East River sediments and PAHs were not detectable in East River pore waters. The East River seems to be a site of intense physical mixing where pore water PAHs possibly bound to DOC may be continuously mobilized out of the seabed. In contrast, PAHs in Newark Bay sediments are able to attain equilibrium due to lower intensity of physical mixing. Aspects of sediment geochemistry such as the occlusion of TOC for PAH binding, particle porosity, and amount of pore water DOC may affect PAH distributions in areas where the physical energy of mixing is infrequent or low. PAH distributions in areas that are subject to high energy physical disturbances, may be controlled by the physical energy affecting the system rather than compositional aspects of particulate or pore water dissolved organic matter.