# Bioturbation by the Ghost Shrimp Lepidophthalmus louisianensis Increases Petroleum Hydrocarbon Degradation for Coastal Sediments in Mildly Oiled Mesocosms

## TL;DR

Ghost shrimp activity helps degrade petroleum hydrocarbons in coastal sediments affected by oil spills.

## Contribution

This study shows that bioturbation by ghost shrimp enhances hydrocarbon degradation in mildly oiled sediments.

## Key findings

- Oil augmentation increased PAH degradation potential in mesocosm sediments.
- Bioturbation further enhanced degradation when oil was present.
- Microbial community composition remained unchanged despite increased degradation activity.

## Abstract

Bioturbating animals move around large amounts of sediment, changing its physicochemical properties and biogeochemical processes. The present study assessed the role of the ghost shrimp Lepidophthalmus louisianensis, a major coastal bioturbator in the Northern Gulf of Mexico, in the fate of crude oil after the 2010 Deepwater Horizon blowout. Experiments were conducted in greenhouse mesocosms, with or without ghost shrimp and with or without added oil, reflecting mild surface or subsurface oiling in a beach environment. To evaluate the hydrocarbon-degradation potential of the sediment microbial community, a respirometric radiotracer assay was conducted with 14C naphthalene as a model polycyclic aromatic hydrocarbon (PAH) compound. Oil augmentation led to a substantial increase in the PAH degradation potential of mesocosm sediments, which was further enhanced by the presence of the bioturbator. However, bioturbation alone, without previous oil exposure, did not enhance naphthalene degradation. 16S rRNA gene analyses showed that there were no significant changes in the microbial community composition associated with either bioturbation, oil augmentation, or both. This study demonstrated bioturbation- and oil-exposure-related enhancement in hydrocarbon degradation in mildly oiled sediment, and indicated that this may be due to an increased expression of PAH degrading activities in the preexisting community of hydrocarbon-degrading bacteria rather than resulting from a shift in the microbial community composition.