Beach sand oil spills select for generalist microbial populations

Abstract

The specialization-disturbance hypothesis predicts that, in the event of a disturbance, generalists are favored, while specialists are selected against. This hypothesis has not been rigorously tested in microbial systems and it remains unclear to what extent it could explain microbial community succession patterns following perturbations. Previous field observations of Pensacola Beach sands that were impacted by the Deepwater Horizon (DWH) oil spill provided evidence in support of the specialization-disturbance hypothesis. However, ecological drift as well as uncounted environmental fluctuations (e.g., storms) could not be ruled out as confounding factors driving these field results. In this study, the specialization-disturbance hypothesis was tested on beach sands, disturbed by DWH crude oil, ex situ in closed laboratory advective-flow chambers that mimic in situ conditions in saturated beach sediments. The chambers were inoculated with weathered DWH oil and unamended chambers served as controls. The time series of shotgun metagenomic and 16S rRNA gene amplicon sequence data from a two-month long incubation showed that functional diversity significantly increased while taxonomic diversity significantly declined, indicating a decrease in specialist taxa. Thus, results from this laboratory study corroborate field observations, providing verification that the specialization-disturbance hypothesis can explain microbial succession patterns in crude oil impacted beach sands.

Small but mighty: how overlooked small species maintain community structure through middle Eocene climate change

“…This fundamental principle is not obeyed in entropy measures such as Shannon's index. The replicable nature of Hill numbers makes them suitable for detecting diversity changes as a result of environmental perturbations whether they be anthropogenic such as oil spills (McClain et al 2019; Miller et al 2020; Heritier-Robbins et al 2021) or, as in the present study, geologically transient climatic events. The commonality of units at all levels of q means that inferences can be made regarding magnitudes of change (Jost 2007, 2010a; Chao et al 2014b) and sample and locality differences (Hill 1973; Chao et al 2014a) and enables the transformation to commonly used general entropy metrics such as Shannon's index and Simpson's index.…”

“…This fundamental principle is not obeyed in entropy measures such as Shannon's index. The replicable nature of Hill numbers makes them suitable for detecting diversity changes as a result of environmental perturbations whether they be anthropogenic such as oil spills (McClain et al 2019;Miller et al 2020;Heritier-Robbins et al 2021) or, as in the present study, geologically transient FIGURE 1. Schematic representation of Hill numbers and how q is related to D. The color gradient in the top panel represents the weight given to abundance, with greater weight given as you move to the right.…”

Microbial Response to Natural Disturbances: Rare Biosphere often plays a role

“…This estimation adjusts for missing species (here GO terms) and sample coverage. The exponential of the estimated Shannon entropy was used to covert the statistic to true diversity ( 1 D) with units of effective GO terms as described recently [39]. The fraction of the total proteome devoted to extracellular proteins for each MAG was predicted using psortb [40].…”