<p> The Gulf of Alaska is a seasonally productive ecosystem surrounded by glaciated coastal mountains with high precipitation. With a combination of high biological production, inputs of suspended sediments from glacial runoff, and contrasting nutrient regimes in offshore and shelf environments, there is a great need to study particle cycling in this region. I measured the concentrations and size distributions of large marine particles (0.06-27 mm) during four cruises in 2014 and 2015 using the Underwater Vision Profiler (UVP). The UVP produces high resolution depth profiles of particle concentrations and size distributions throughout the water column, while generating individual images of objects >500 &mu;m including marine snow particles and mesozooplankton. </p><p> The objectives of this study were to 1) describe spatial variability in particle concentrations and size distributions, and 2) use that variability to identify driving processes. I hypothesized that UVP particle concentrations and size distributions would follow patterns in chlorophyll <i>a</i> concentrations. Results did not support this hypothesis. Instead, a major contrast between shelf and offshore particle concentrations and sizes was observed. Total concentrations of particles increased with proximity to glacial and fluvial inputs. Over the shelf, particle concentrations on the order of 1000-10,000/L were 1-2 orders of magnitude greater than offshore concentrations on the order of 100/L. Driving processes over the shelf included terrigenous inputs from land, resuspension of bottom sediments, and advective transport of those inputs along and across the shelf. Offshore, biological processes were drivers of spatial variability in particle concentration and size. High quantities of terrigenous sediments could have implications for enhanced particle flux due to ballasting effects and for offshore transport of particulate phase iron to the central iron-limited gyre. The dominance of resuspended material in shelf processes will inform the location of future studies of the biological pump in the coastal Gulf of Alaska. This work highlights the importance of continental margins in global biogeochemical processes.</p>

Mercury (Hg) in the environment has deleterious ecological and health affects for humans and wildlife and is primarily transferred to humans through the consumption of marine biota (USEPA, 2001). These ecological and health concerns are exacerbated by the production of methylmercury (CH3Hg+; MMHg) in aquatic ecosystems. Sulfur isotopes (δ34S) are an indicator of the strength of sulfate reduction associated with MMHg production. In chapter 1, we assessed the relationship between MMHg concentrations and reduced-sulfur stable isotope δ34S signals in four coastal consumer organisms (length = 26–75 mm) from Florida's Big Bend seagrass meadows: pinfish (Lagodon rhomboides); pigfish (Orthopristis chrysopter); black sea bass (Centropristis striata melana); and shrimp (Tozeuma carolinense and T. serratum). We found a significant correlation between depleted δ34S signatures in fauna tissue (R2 = 0.27; p < 0.001; total n = 179) with higher MMHg concentrations. A correlation was observed in lower δ34S isotopic signatures and higher MMHg concentrations of consumers from the southern region of the study area indicating a "hotspot" of net mercury methylation in the sediments near Tampa Bay, Florida. To better understand the sources of Hg to coastal pinfish and to assess the contribution of pinfish annual egress to offshore food webs, chapter 2 applies isotopic tracing (C, N, S) combined with mercury (Hg) concentrations and isotope ratios in sediments, juvenile pinfish, juvenile gag grouper (Mycteropera microlepis), and adult gag grouper and pinfish to assess exposure pathways of MMHg in the northeastern Gulf of Mexico. We found that pinfish from the northern and southern Big Bend regions had distinct Hg sources. Southern pinfish had enriched δ202Hg and, when combined with lower pinfish δ34S values and lower sediment δ202Hg values, suggested elevated microbial methylation/demethylation in the southern region. The southern, coastal pinfish exhibited similar Δ199Hg as offshore gag grouper suggesting pinfish from this region represent an important Hg source to offshore reef fish species and/or these two cohorts are exposed to the same Hg source. Results suggested that estuaries can be an important source of MMHg to adjacent, offshore commercially important reef species and confirmed the utility of Hg isotope analysis to identify multiple marine Hg sources and inform our understanding of the pathways of MMHg bioaccumulation in estuarine food webs. In the northern Gulf of Mexico (nGOM), the Hg cycle is further complicated by the influence of the Mississippi River (MR) and potentially confounded, since April 2010, by the Deepwater Horizon (DWH) oil spill. Approximately 3.0-4.9% of oil-derived carbon released during the Deepwater Horizon oil spill was deposited on the seafloor (Chanton et al., 2014; Valentine et al., 2014) causing local, but persistent, oxygen depletion (Kessler et al., 2011). In these low-oxygen environments, the formation of monomethylmercury (MMHg) is promoted and may have led to higher MMHg concentrations in commercially important reef fish species. Expanding our research to include the entire nGOM shelf, slope, and the far-reaches of the deep Gulf canyons, chapter 3 explores Hg cycling using benthic and pelagic fishes as indicator-samples. Fish in the western study region appeared to rely more on benthic feeding, as indicated by enriched δ13C values and depleted δ34S values. Fish species closer to the MR plume had enriched δ15N and depleted δ202Hg and Δ199Hg values suggesting the MR influenced the nutrient and Hg cycle in the northeastern GOM. Cutthroat eels (~1,000 m) had higher MIF signatures than slope snake eels (~250 M) and, when combined with decreasing δ13C values with depth, suggested the presence of near-surface derived Hg in the deep DeSoto Canyon. Our results highlighted the importance of the deposition of Hg associated upper water column OM such as the marine snow pelagic carbon. Chapter 4 investigates whether more reducing conditions cause by DWH led to higher levels of mercury in commercially important reef associated organisms. We compared pre-spill (collected 2007-09) and post-spill (collected 2012) fish species of similar length from hard-bottom reefs on the West Florida Shelf. Light stable isotope analyses of carbon, nitrogen, and sulfur was employed to assess feeding ecologies of those species exhibiting higher MMHg concentrations following the oil spill. Some species, like porgy, showed significant increase in Hg concentration. This increase may have been associated with a shift to a more pelagic, higher trophic feeding regime. The significance of this study is that it shows that the oil spill had an effect on the mercury cycling but that the effect is not uniform for each fish species. / A Dissertation submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the Doctor of Philosophy. / Spring Semester 2016. / January 11, 2016. / Bioaccumulation, Deepwater Horizon oil spill, Florida Big Bend, Isotope, Mercury, Pinfish / Includes bibliographical references. / Jeffery Chanton, Professor Co-Directing Dissertation; William Landing, Professor Co-Directing Dissertation; Xiaojun Yang, University Representative; Yang Wang, Committee Member; Dean Grubbs, 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.

Graduation date: 1986

After the Deepwater Horizon (DWH) blowout, MC252 crude oil was washed onto the shores of the northeastern Gulf of Mexico. Weathered oil was buried in sandy Florida beaches in the form of sands covered by oil films, small oil particles, large agglomerates and oiled sand layers. While oil films and oil particles were observed to degrade relatively quickly, larger buried sand and oil agglomerates (SOA) can persist in the dry beach sand, where they are protected from photodegradation and mechanical stress. To determine the degradation of such large agglomerates, a time series study was initiated that quantified the weight loss and compositional changes of MC252 standardized sand and oil agglomerates (sSOAs) buried at 5, 15, 25, 35, and 45 cm depths in dry beach sand at Pensacola Beach, Florida. Sets of 10 experimental, standardized SOAs were removed at 2 - 6 month intervals over a time period of 3 years. Analysis of the sSOAs revealed a total weight loss of 10.85% or 3.66 g per sSOA volume and a loss in petroleum hydrocarbons of 59% or 2.85 g per sSOA/ over the three-year burial period. Decay rate constants for saturated hydrocarbons (C15-C40) of the surface layer of the sSOAs averaged 0.0043 d-1 (SE = 0.0017) for initial 181-day period, and 0.0027 d-1 (SE = 0.0004) for the thee-year observation period (C15-C40). PAH initial decay was 0.022 d-1 (SE = 0.004) for the initial (181-day) decay and 0.005 d-1 (SE = 0.001) for three-year period for the compounds that could be detected in the sSOA surface layer (biphenyl, acenaphthylene, acenaphthene, fluorine, dibenzothiopene, phenanthrene, pyrene, benzo(c)phenanthrene, chrysene, 7,12-dimethylbenz(a)anthracene, benzo(b,j,k)fluoranthene, benzo(a)pyrene, and benzo(g,h,i)perylene) in the surface lay. The results indicate that buried larger SOAs persist in the dry beach sands for years despite access to oxygen in contrast to oil films on sand grains and buried small oil particles that at Pensacola Beach disappeared within a year. Causes for the slow degradation of larger SOAs in the beach include the lack of photodegradation, the protection from mechanical disintegration, as well as low nutrient and moisture concentrations in the sand. / 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. / Summer Semester 2018. / May 14, 2018. / BP Oil, degradation, oil decay, polycyclic aromatic hydrocarbons, saturated hydrocarbons, sediment / Includes bibliographical references. / Markus H. Huettel, Professor Directing Thesis; Ian R. MacDonald, Committee Member; Yang Wang, Committee Member; Olivia U. Mason, Committee Member.

After the Deepwater Horizon (DWH) blowout, MC252 crude oil was washed onto the shores of the northeastern Gulf of Mexico. Weathered oil was buried in sandy Florida beaches in the form of sands covered by oil films, small oil particles, large agglomerates and oiled sand layers. While oil films and oil particles were observed to degrade relatively quickly, larger buried sand and oil agglomerates (SOA) can persist in the dry beach sand, where they are protected from photodegradation and mechanical stress. To determine the degradation of such large agglomerates, a time series study was initiated that quantified the weight loss and compositional changes of MC252 standardized sand and oil agglomerates (sSOAs) buried at 5, 15, 25, 35, and 45 cm depths in dry beach sand at Pensacola Beach, Florida. Sets of 10 experimental, standardized SOAs were removed at 2 - 6 month intervals over a time period of 3 years. Analysis of the sSOAs revealed a total weight loss of 10.85% or 3.66 g per sSOA volume and a loss in petroleum hydrocarbons of 59% or 2.85 g per sSOA/ over the three-year burial period. Decay rate constants for saturated hydrocarbons (C15-C40) of the surface layer of the sSOAs averaged 0.0043 d-1 (SE = 0.0017) for initial 181-day period, and 0.0027 d-1 (SE = 0.0004) for the thee-year observation period (C15-C40). PAH initial decay was 0.022 d-1 (SE = 0.004) for the initial (181-day) decay and 0.005 d-1 (SE = 0.001) for three-year period for the compounds that could be detected in the sSOA surface layer (biphenyl, acenaphthylene, acenaphthene, fluorine, dibenzothiopene, phenanthrene, pyrene, benzo(c)phenanthrene, chrysene, 7,12-dimethylbenz(a)anthracene, benzo(b,j,k)fluoranthene, benzo(a)pyrene, and benzo(g,h,i)perylene) in the surface lay. The results indicate that buried larger SOAs persist in the dry beach sands for years despite access to oxygen in contrast to oil films on sand grains and buried small oil particles that at Pensacola Beach disappeared within a year. Causes for the slow degradation of larger SOAs in the beach include the lack of photodegradation, the protection from mechanical disintegration, as well as low nutrient and moisture concentrations in the sand. / 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. / Summer Semester 2018. / May 14, 2018. / BP Oil, degradation, oil decay, polycyclic aromatic hydrocarbons, saturated hydrocarbons, sediment / Includes bibliographical references. / Markus H. Huettel, Professor Directing Thesis; Ian R. MacDonald, Committee Member; Yang Wang, Committee Member; Olivia U. Mason, Committee Member.

Thesis (Ph. D.)--Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1983. / Includes bibliographical references (p. 268-279).

Thesis (M.S.)--University of North Carolina Wilmington, 2009. / Title from PDF title page (February 17, 2010) Includes bibliographical references (p. 54-58)

Thesis (Ph. D.)--Massachusetts Institute of Technology and Woods Hole Oceanographic Institution. / Includes bibliographical references (p. 260-271).

<p> Oceans are acidifying as atmospheric CO₂ is drawn down. This process, known as ocean acidification (OA), is well known and documented. Over the next 100 years, pH of the surface ocean is projected to decrease by up to 0.35 units. This CO₂ draw down has a direct effect on dissolved inorganic carbon (DIC) balance in the ocean. OA is expected to impact calcifying organisms that rely on constituencies of the DIC system, specifically carbonate ion [CO₃^2-]. It is clear that externally calcified structures, such as coral skeletons, bivalve shells, etc., will be significantly affected as pH, and consequently [CO₃^2&minus;], of the oceans decline. What is unclear, however, is how these changes will impact internally calcified structures, such as earstones (otoliths) of teleost fish. This dissertation examines the impacts of OA on otolith mineralization in larval reef fish (<i>Amphiprion clarkii</i>and <i>A. frenatus </i>). This research included the development of a laboratory controller system for control of experimental aquaria pH through pCO₂ dosing, exposure of larvae from hatch to settlement under various pCO2 treatments and evaluation of otolith structure and morphology across treatments within a single genus. </p><p> No standard method for pH-stat CO₂ dosing controllers existed prior to this study. Incorporating low-cost, flexible hardware allowed high precision and accuracy pH controllers to be designed and implemented. Following system stability studies, we found that our system performed at or beyond the level of control exhibited in the literature. </p><p> Two species of clownfish, <i>Amphiprion clarkii</i> and <i> A. frenatus,</i> were exposed to different pCO₂ conditions, reared to settlement and otoliths extracted and studied. I found that the sagittae (largest of the 3 otolith types) of both species exhibited circularity changes towards more oblong otoliths under increased pCO₂. For <i> A. clarkii,</i> I found a significant negative relation between pCO₂ and lapilli otolith circularity, indicating a shift toward more circular lapilli under increased pCO₂. Since lapilli are critical to gravisensing in teleosts these results explain my anecdotal observations that, at high pCO₂, larvae exhibited lethargic, uncoordinated swim patterns. The core development of otoliths (sagittae, lapilli, and asterisci) from both species was analyzed using SEM imagery. Otolith images were scored by 6 independent readers for core development (poorly developed to well-developed). Otolith scores were regressed against aragonite saturation state (&ohm;_Ar). Results showed significant and strong relations between &ohm;Ar and development score, indicating a shift toward protruding, unorganized crystal clusters within the core under high pH/low &ohm;_Ar. </p><p> This research is the first to comprehensively examine the impact of OA on the otolith system in larval fish. The research revealed direct impacts on otolith structure and morphology as well as mineralogy. These changes will directly impact survival of the larvae. It remains unknown whether the otolith system recovers post-settlement or whether the anecdotal observations on swimming behavior are directly related to otolith deformation. Future research will include exploration of these relations across genera as well as more deeply examine the recovery of the system and behavioral impacts of otolith deformation across life stages.</p>