CitationCharacterization of marine isoprene-degrading communities. 2009, 11 (12) In contrast to specialist methane-oxidising bacteria, cultivated isoprene degraders were nutritionally versatile, and nearly all of them were able to use n-alkanes as a source of carbon and energy. We therefore tested and showed that the ubiquitous marine hydrocarbon-degrader, Alcanivorax borkumensis, could also degrade isoprene. A mixture of the isolates consumed isoprene emitted from algal cultures, confirming that isoprene can be metabolized at low, environmentally-relevant concentrations, and suggesting that, in the absence of spilled petroleum hydrocarbons, algal production of isoprene could maintain viable populations of hydrocarbon-degrading microbes. This discovery of a missing marine sink for isoprene is the first step in obtaining more robust predictions of its flux, and suggests that algal-derived isoprene provides an additional source of carbon for diverse microbes in the oceans.Acuña Alvarez et al.

ABSTRACTMudflats and salt marshes are habitats at the interface of aquatic and terrestrial systems that provide valuable services to ecosystems. Therefore, it is important to determine how catastrophic incidents, such as oil spills, influence the microbial communities in sediment that are pivotal to the function of the ecosystem and to identify the oil-degrading microbes that mitigate damage to the ecosystem. In this study, an oil spill was simulated by use of a tidal chamber containing intact diatom-dominated sediment cores from a temperate mudflat. Changes in the composition of bacteria and diatoms from both the sediment and tidal biofilms that had detached from the sediment surface were monitored as a function of hydrocarbon removal. The hydrocarbon concentration in the upper 1.5 cm of sediments decreased by 78% over 21 days, with at least 60% being attributed to biodegradation. Most phylotypes were minimally perturbed by the addition of oil, but at day 21, there was a 10-fold increase in the amount of cyanobacteria in the oiled sediment. Throughout the experiment, phylotypes associated with the aerobic degradation of hydrocarbons, including polycyclic aromatic hydrocarbons (PAHs) (Cycloclasticus) and alkanes (Alcanivorax,Oleibacter, andOceanospirillalesstrain ME113), substantively increased in oiled mesocosms, collectively representing 2% of the pyrosequences in the oiled sediments at day 21. Tidal biofilms from oiled cores at day 22, however, consisted mostly of phylotypes related toAlcanivorax borkumensis(49% of clones),Oceanospirillalesstrain ME113 (11% of clones), and diatoms (14% of clones). Thus, aerobic hydrocarbon biodegradation is most likely to be the main mechanism of attenuation of crude oil in the early weeks of an oil spill, with tidal biofilms representing zones of high hydrocarbon-degrading activity.

Coastal and estuarine ecosystems are highly susceptible to crude oil pollution. Therefore, in order to examine the resilience of benthic phototrophs that are pivotal to coastal ecosystem functioning, we simulated an oil spill in tidal mesocosms consisting of intact sediment cores from a mudflat at the mouth of the Colne Estuary, UK. At day 21, fluorescence imaging revealed a bloom of cyanobacteria on the surface of oiled sediment cores, and the upper 1.5 cm thick sediment had 7.2 times more cyanobacterial and 1.7 times more diatom rRNA sequences when treated with oil. Photosystem II operating efficiency (Fq'/Fm') was significantly reduced in oiled sediments at day 7, implying that the initial diatom-dominated community was negatively affected by oil, but this was no longer apparent by day 21. Oil addition significantly reduced numbers of the key deposit feeders, and the decreased grazing pressure is likely to be a major factor in the increased abundance of both diatoms and cyanobacteria. By day 5 concentrations of dissolved inorganic nitrogen were significantly lower in oiled mesocosms, likely resulting in the observed increase in nifH-containing, and therefore potentially dinitrogen-fixing, cyanobacteria. Thus, indirect effects of oil, rather than direct inhibition, are primarily responsible for altering the microphytobenthos.

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