After Deepwater Horizon oil reached the Florida coast, oil was buried in Pensacola Beach (PB) sands to ~ 70 cm depth, resulting in Total Petroleum Hydrocarbon (TPH) concentrations up to ~ 2 kg per meter of beach. This study followed the decomposition of the buried oil and the factors influencing its degradation. The abundance of bacteria in oiled sand increased by 2 orders of magnitude within one week after oil burial, while diversity decreased by ~ 50%. Half-lives of aliphatic and aromatic hydrocarbons reached 25 and 22 days, respectively. Aerobic microbial oil decomposition, promoted by tidal pumping, and human cleaning activities effectively removed oil from the beach. After one year, concentrations of GC-amenable hydrocarbons at PB were similar to those in the uncontaminated reference beach at St. George Island/FL, and microbial populations that disappeared after the oil contamination had reestablished. Yet, oxihydrocarbons can be found at PB to the present day.

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The oil from the Exxon Valdez incident is still observed in different Prince William Sound beaches over two decades. The persisting oil is slightly weathered and highly toxic to the environment. Several studies investigated the reasons for lingering oil. Different remediation techniques were tried and the results were not satisfactory. Recently, it was found that the oil is stranded in a low permeability layer. Detailed explorations showed that the exchange of the nutrients and oxygen is limited in this layer. The main objective of the present study is to explain the effect of oxygen and nutrients on the degradation phenomena in the Alaskan beaches. The general approach for this study is a combination of the field experiments and lab analysis. As it is important to eliminate any cross-layer contamination, a unique sampling method was developed. The applied method involves collecting samples from the oily layer (low permeability layer), measuring oxygen levels in the field and comparing them with the nutrient samples analyzed in the lab. The findings showed that the nutrients levels were low in the beach but the lack of effective electron acceptor is the major factor limiting the biodegradation of the oil. The seawater is responsible for delivering the oxygen and nutrients to the beach during the high tide while during low tide the landward freshwater discharges to the beach. The study of the sulfate and nitrate in the beach revealed that the levels of the alternative electron acceptors were not sufficient to support anaerobic biodegradation. Finally, for successful biodegradation of the Exxon Valdez oil, adequate levels of nutrients (nitrogen and phosphorous) and along with oxygen are required. / Civil Engineering

Cold-water corals are an important component of deep-sea ecosystems as they establish structurally complex habitats that support benthic biodiversity. These communities face imminent threats from increasing anthropogenic influences in the deep sea. Following the 2010 Deepwater Horizon blowout, several spill-impacted coral communities were discovered in the deep Gulf of Mexico, and subsequent mesophotic regions, although the exact source and extent of this impact is still under investigation, as is the recovery potential of these organisms. At a minimum, impacted octocorals were exposed to flocculant material containing oil and dispersant components, and were visibly stressed. Here the impacts of oil and dispersant exposure are assessed for the octocoral genus Paramuricea. A de novo reference assembly was created to perform gene expression analyses from high-throughput sequencing data. Robust assessments of these data for P. biscaya colonies revealed the underlying expression-level effects resulting from in situ floc exposure. Short-term toxicity studies, exposing the cold-water octocorals Paramuricea type B3 and Callogorgia delta to various fractions and concentrations of oil, dispersant and oil/dispersant mixtures, were also conducted to determine overall toxicity and tease apart the various components of the synergistic exposure effects. Finally, alterations in Paramuricea B3 gene expression profiles were inspected to characterize genome-wide changes induced by each treatment and putative genes under differential regulation. The experimental results provide evidence for a relatively high toxicity of chemical dispersants as compared to oil additions alone, elucidating the implications of applying oil dispersants to future oil spills. My findings revealed signatures of cellular stress in floc-exposed corals associated with xenobiotic metabolism, immune and inflammatory responses as well as transcriptional suppression of vital cellular components like ribosomal proteins. The data also suggests poor recovery potential in our coral samples exposed to floc. In addition, promising biomarker candidates were identified from the differential expression data for use in future spill-impact monitoring. / Biology