Shifts in the Microbial Community Composition of Gulf Coast Beaches Following Beach Oiling

Abstract

Microorganisms associated with coastal sands serve as a natural biofilter, providing essential nutrient recycling in nearshore environments and acting to maintain coastal ecosystem health. Anthropogenic stressors often impact these ecosystems, but little is known about whether these disturbances can be identified through microbial community change. The blowout of the Macondo Prospect reservoir on April 20, 2010, which released oil hydrocarbons into the Gulf of Mexico, presented an opportunity to examine whether microbial community composition might provide a sensitive measure of ecosystem disturbance. Samples were collected on four occasions, beginning in mid-June, during initial beach oiling, until mid-November from surface sand and surf zone waters at seven beaches stretching from Bay St. Louis, MS to St. George Island, FL USA. Oil hydrocarbon measurements and NOAA shoreline assessments indicated little to no impact on the two most eastern beaches (controls). Sequence comparisons of bacterial ribosomal RNA gene hypervariable regions isolated from beach sands located to the east and west of Mobile Bay in Alabama demonstrated that regional drivers account for markedly different bacterial communities. Individual beaches had unique community signatures that persisted over time and exhibited spatial relationships, where community similarity decreased as horizontal distance between samples increased from one to hundreds of meters. In contrast, sequence analyses detected larger temporal and less spatial variation among the water samples. Superimposed upon these beach community distance and time relationships, was increased variability in bacterial community composition from oil hydrocarbon contaminated sands. The increased variability was observed among the core, resident, and transient community members, indicating the occurrence of community-wide impacts rather than solely an overprinting of oil hydrocarbon-degrading bacteria onto otherwise relatively stable sand population structures. Among sequences classified to genus, Alcanivorax , Alteromonas , Marinobacter , Winogradskyella , and Zeaxanthinibacter exhibited the largest relative abundance increases in oiled sands.

Diversity and Transport of Microorganisms in Intertidal Sands of the California Coast

“…Previous work has explored the diversity of microorganisms primarily in subtidal or submerged permeable marine sediment (10)(11)(12)(13)(14)(15)(16)(17), while little work has explored their diversity in intertidal sands (20)(21)(22)(23)(24). The present study uncovered extensive diversity in intertidal sands at 49 beaches spanning 1,350 km of the California coast using next-generation 454 sequencing of the V6-V4 hypervariable region of the 16S rRNA gene.…”

“…We used the V6-V4 region of the 16S rRNA gene since it has been recently used to study bacterial communities in intertidal beach sands (21). However, there are different regions of the 16S rRNA gene that have been targeted by investigators with the goal of improving community coverage and alleviating errors associated with primer biases (52)(53)(54)(55).…”

“…A unique 11-nucleotide multiplex identifier was included in each forward primer between the adapter sequence and the 16S-specific sequence. The 16S rRNA sequences used to target the V6-V4 region were 518F-CCAGCAGCYGCGGTAAN and 1064R-CGACRRCC ATGCANCACCT (21). PCR cycling parameters included an initial denaturation step at 94°C for 2 min, followed by 40 cycles of 94°C for 30 s, 57°C for 45 s, and 68°C for 1 min and a final extension at 68°C for 2 min.…”

Microbial community successional patterns in beach sands impacted by the Deepwater Horizon oil spill

“…Studies characterizing the taxonomic shifts between contaminated and noncontaminated beach sediments recognized that the oil input strongly affected the beach sand microbial communities, which responded with increased bacterial cell densities (Kostka et al, 2011), reduced taxonomic diversity, and a succession of microbial populations that paralleled the changes in abundance and composition of deposited hydrocarbons (Kostka et al, 2011;Bik et al, 2012;Lamendella et al, 2014). Consistent responses have been observed across study sites, although other factors such as site heterogeneity and seasonal fluctuations in environmental parameters have been shown to somewhat confound assessments of the oil impact in certain beaches (Newton et al, 2013), sometimes making them undetectable (Rö ling et al, 2004). In general, an initial increase in the relative representation of known oil degraders, mostly of the Gammaproteobacteria class (most notably Alcanivorax), was observed together with a temporal succession characterized by an increase in relative abundance of Bacillus, Microbacterium and members of the Alphaproteobacteria class at later stages, when recalcitrant oil hydrocarbons predominate (Kostka et al, 2011).…”

Lifestyles of rarity: understanding heterotrophic strategies to inform the ecology of the microbial rare biosphere

“…There is evidence that rare taxa are or can become active in their communities (Hunt et al 2013, Wilhelm et al 2014, Aanderud et al 2015, sometimes providing key functions (Pester et al 2010, Sauret et al 2014. Additionally, some rare taxa are sensitive to disturbances (Sjöstedt et al 2012, Coveley et al 2015, Vuono et al 2016, notably after the recent Deepwater Horizon oil spill (Newton et al 2013). Rare soil taxa that were below detection not only responded to pulses of precipitation by blooming but also contributed to increased carbon dioxide and methane production, demonstrating that rare taxa collectively can contribute to ecosystem function (Aanderud et al 2015).…”