Temporal variability of microbial response to crude oil exposure in the northern Gulf of Mexico

Oil spills are common occurrences in the United States and can result in extensive ecological damage. The 2010 Deepwater Horizon oil spill in the Gulf of Mexico was the largest accidental spill recorded. Many studies were performed in deep water habitats to understand the microbial response to the released crude oil. However, much less is known about how planktonic coastal communities respond to oil spills and whether that response might vary over the course of the year. Understanding this temporal variability would lend additional insight into how coastal Florida habitats may have responded to the Deepwater Horizon oil spill. To assess this, the temporal response of planktonic coastal microbial communities to acute crude oil exposure was examined from September 2015 to September 2016 using seawater samples collected from Pensacola Beach, Florida, at 2-week intervals. A standard oil exposure protocol was performed using water accommodated fractions made from MC252 surrogate oil under photo-oxidizing conditions. Dose response curves for bacterial production and primary production were constructed from 3H-leucine incorporation and 14C-bicarbonate fixation, respectively. To assess drivers of temporal patterns in inhibition, a suite of biological and environmental parameters was measured including bacterial counts, chlorophyll a, temperature, salinity, and nutrients. Additionally, 16S rRNA sequencing was performed on unamended seawater to determine if temporal variation in the in situ bacterial community contributed to differences in inhibition. We observed that there is temporal variation in the inhibition of primary and bacterial production due to acute crude oil exposure. We also identified significant relationships of inhibition with environmental and biological parameters that quantitatively demonstrated that exposure to water-soluble crude oil constituents was most detrimental to planktonic microbial communities when temperature was high, when there were low inputs of total Kjeldahl nitrogen, and when there was low bacterial diversity or low phytoplankton biomass

Acute inhibition of bacterial growth in coastal seawater amended with crude oils with varied photoreactivities

The increased potential for contamination of seawater by crude oils requires studies of bacterial biodegradation potential, but little is known of the differential negative impacts of oils on bacterial growth. No two wells generate chemically identical oils; and importantly, solar exposure of crude oil may differentially affect the bacterial response. Elucidating the role that sunlight plays on the potential toxicity of spilled crude oils is imperative to understanding how oil spills might affect microbes in the tropical and subtropical waters of Florida. This study examined light exposure of six different crude oils, and subsequent microbial responses to altered oils. Marine bacterioplankton heterotrophic activities were measured via3H-leucine incorporation after the addition of oils’ water accommodated fractions (WAFs) that were created under varied solar conditions. Inhibition of production increased with higher concentrations of WAFs, but dose-response trends varied among the oils. Increased solar exposure during WAF preparation generally led to more inhibition, but trends varied among oils. WAFs were also prepared under different parts of the solar spectrum. Solar-irradiated WAFs resulted in significant but variable acute toxicity vs. dark counterparts. Solar-induced toxicity was primarily a result of visible and not ultraviolet light exposure. Results indicate responses to oil spills are highly dependent on the source of the oil and solar conditions at the time and location of the spill. The data presented here demonstrate the importance of photochemical changes and oil source in modulating microbial activity and bioremediation potential

Can We Make Money with Fifth-order Autocorrelation in Japanese Stock Prices?

We first report that one-minute returns on TOPIX have exhibited significant autocorrelation at five-minute intervals since 1997/98, which implies there is an arbitrage opportunity. Special quotes that are issued whenever there is a price jump in excess of a predetermined band seem to be the source of this autocorrelation, since these have been updated at five-minute intervals since August 1998. Individual stock returns also exhibit fifth-order autocorrelation, but this disappears when the data with special quotes are excluded from the sample. The arbitrage opportunities, however, turn out to be spurious since trading is suspended whenever a special quote is issued

Management of Hazardous Waste and Contaminated Land

Regulation of hazardous waste and cleanup of contaminated sites are two major components of modern public policy for environmental protection. We review the literature on these related areas, with emphasis on empirical analyses. Researchers have identified many behavioral responses to regulation of hazardous waste, including changes in the location of economic activity. However, the drivers behind compliance with these costly regulations remain a puzzle, as most research suggests a limited role for conventional enforcement. Increasingly sophisticated research examines the benefits of cleanup of contaminated sites, yet controversy remains about whether the benefits of cleanup in the U.S. exceed its costs. Finally, research focusing on the imposition of legal liability for damages from hazardous waste finds advantages and disadvantages of the U.S. reliance on legal liability to pay for cleanup, as opposed to the government-financed approaches more common in Europe

Heterogeneity and Strategic Choices: The Case of Stock Repurchases

Strategic decisions are fundamentally tough choices. Theory suggests that managers are likely to display bounded rationality. Empirics on the other hand assume rationality in choice behavior. Recognizing this inherent disconnect between theory and empirics, we try to account for behavioral biases using a theoretically consistent choice model. The traditional approach to modeling strategic choice has been to use discrete choice models and make inference on the conditional mean effects. We argue that the conditional mean effect does not capture behavioral biases. The focus should be on the conditional variance. Explicitly modeling the conditional variance (in the discrete choice framework) provides us with valuable information on individual level variation in decision-making. We demonstrate the effect of ignoring the role of variance in choice modeling in the context of firm’s decisions to conduct open market repurchases. We show that when taking into account the heterogeneity in choices, manager’s choices of conducting open market repurchases displays considerable heterogeneity and that not accounting for such heterogeneity might lead to wrong conclusions on the mean effects

Institutional Herding in Financial Markets: New Evidence Through the Lens of a Simulated Model

Due to data limitations and the absence of testable, model-based predictions, theory and evidence on herd behavior are only loosely connected. This paper contributes towards closing this gap in the herding literature. We use numerical simulations of a herd model to derive new, theory-based predictions for aggregate herding intensity. Using high-frequency, investor-specific trading data we confirm the predicted impact of information risk on herding. In contrast, the increase in buy herding measured for the financial crisis period cannot be explained by the herd model