Project description:Increasing atmospheric CO2 concentrations are causing decreased pH over vast expanses of the ocean. This decreasing pH may alter biogeochemical cycling of carbon and nitrogen via the microbial process of nitrification, a key process that couples these cycles in the ocean, but which is often sensitive to acidic conditions. Recent reports indicate a decrease in oceanic nitrification rates under experimentally lowered pH. How composition and abundance of ammonia oxidizing bacteria (AOB) and archaea (AOA) assemblages respond to decreasing oceanic pH, however, is unknown. We sampled microbes from two different acidification experiments and used a combination of qPCR and functional gene microarrays for the ammonia monooxygenase gene (amoA) to assess how acidification alters the structure of ammonia oxidizer assemblages. We show that despite widely different experimental conditions, acidification consistently altered the community composition of AOB by increasing the relative abundance of taxa related to the Nitrosomonas ureae clade. In one experiment this increase was sufficient to cause an increase in the overall abundance of AOB. There were no systematic shifts in the community structure or abundance of AOA in either experiment. These different responses to acidification underscore the important role of microbial community structure in the resiliency of marine ecosystems. amoA gene diversity from two ocean acidification experiments, Monterey Bay experiment (two time points, ambient and acidified) and Vineyard Sound experiment (ambient and acifidied, with and without nutrients) examined with 2 two-color arrays (Cy3 and Cy5): the universal standard 20-mer oligo is printed to the slide with a 70-mer oligo (an archetype). Environmental DNA sequences (fluoresced with Cy3) within 15% of the 70-mer conjugated to a 20-mer oligo (fluoresced with Cy5) complementary to the universal standard will bind to the oligo probes on the array. Signal is the ratio of Cy3 to Cy5.
Project description:Increasing atmospheric CO2 concentrations are causing decreased pH over vast expanses of the ocean. This decreasing pH may alter biogeochemical cycling of carbon and nitrogen via the microbial process of nitrification, a key process that couples these cycles in the ocean, but which is often sensitive to acidic conditions. Recent reports indicate a decrease in oceanic nitrification rates under experimentally lowered pH. How composition and abundance of ammonia oxidizing bacteria (AOB) and archaea (AOA) assemblages respond to decreasing oceanic pH, however, is unknown. We sampled microbes from two different acidification experiments and used a combination of qPCR and functional gene microarrays for the ammonia monooxygenase gene (amoA) to assess how acidification alters the structure of ammonia oxidizer assemblages. We show that despite widely different experimental conditions, acidification consistently altered the community composition of AOB by increasing the relative abundance of taxa related to the Nitrosomonas ureae clade. In one experiment this increase was sufficient to cause an increase in the overall abundance of AOB. There were no systematic shifts in the community structure or abundance of AOA in either experiment. These different responses to acidification underscore the important role of microbial community structure in the resiliency of marine ecosystems. SUBMITTER_CITATION: Title: Acidification alters the composition of ammonia oxidizing microbial assemblages in marine mesocosms Journal: Marine Ecology Progress Series Issue: 492 Pages: 1-8 DOI: 10.3354/meps 10526 Authors: Jennifer L Bowen Patrick J Kearns Michael Holcomb Bess B Ward
Project description:Ammonia-oxidizing archaea (AOA) have been reported at high abundance in much of the global ocean, even in environments such as pelagic oxygen minimum zones (OMZs), where conditions seem unlikely to support aerobic ammonium oxidation. Due to the lack of information on any potential alternative metabolism of AOA, the AOA community composition might be expected to differ between oxic and anoxic environments, indicating some difference in ecology and/or physiology of the AOA assemblage. This hypothesis was tested by evaluating AOA community composition using a functional gene microarray that targets the ammonia monooxygenase gene subunit A (amoA). The relationship between environmental parameters and the biogeography of the Arabian Sea and the Eastern Tropical South Pacific (ETSP) AOA assemblages was investigated using principal component analysis (PCA) and redundancy analysis (RDA). In both the Arabian Sea and the ETSP, AOA communities within the core of the OMZ were not significantly different from those inhabiting the oxygenated surface waters above the OMZ. The AOA communities in the Arabian Sea were significantly different from those in the ETSP. In both oceans, the abundance of archaeal amoA gene in the core of the OMZ was higher than that in the surface waters. Our results indicate that AOA communities are distinguished by their geographic origin. RDA suggested that temperature was the main factor that correlated with the differences between the AOA communities from the Arabian Sea and those from the ETSP. Physicochemical properties that characterized the different environments of the OMZ and surface waters played a less important role than did geography in shaping the AOA community composition.
Project description:Ammonia oxidizer community structure were examined in a depth profile from 20 to 2000 m at the Bermuda Atlantic Time-series Study using a functional gene microarray to look at amoA diversity