McParland
Erin L.
McParland
Erin L.
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ArticleParameterizing the impact of seawater temperature and irradiance on dimethylsulfide (DMS) in the Great Barrier Reef and the contribution of coral reefs to the global sulfur cycle(American Geophysical Union, 2021-02-15) Jackson, Rebecca L. ; Gabric, Albert ; Matrai, Patricia A. ; Woodhouse, Matthew T. ; Cropp, Roger ; Jones, Graham B. ; Deschaseaux, Elisabeth S. M. ; Omori, Yuko ; McParland, Erin L. ; Swan, Hilton B. ; Tanimoto, HiroshiBiogenic emissions of dimethylsulfide (DMS) are an important source of sulfur to the atmosphere, with implications for aerosol formation and cloud albedo over the ocean. Natural aerosol sources constitute the largest uncertainty in estimates of aerosol radiative forcing and climate and thus, an improved understanding of DMS sources is needed. Coral reefs are strong point sources of DMS; however, this coral source of biogenic sulfur is not explicitly included in climatologies or in model simulations. Consequently, the role of coral reefs in local and regional climate remains uncertain. We aim to improve the representation of tropical coral reefs in DMS databases by calculating a climatology of seawater DMS concentration (DMSw) and sea-air flux in the Great Barrier Reef (GBR), Australia. DMSw is calculated from remotely sensed observations of sea surface temperature and photosynthetically active radiation using a multiple linear regression model derived from field observations of DMSw in the GBR. We estimate that coral reefs and lagoon waters in the GBR (∼347,000 km2) release 0.03–0.05 Tg yr−1 of DMS (0.02 Tg yr−1 of sulfur). Based on this estimate, global tropical coral reefs (∼600,000 km2) could emit 0.08 Tg yr−1 of DMS (0.04 Tg yr−1 of sulfur), with the potential to influence the local radiative balance.
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ArticleThe microbiological drivers of temporally dynamic Dimethylsulfoniopropionate cycling processes in Australian coastal shelf waters(Frontiers Media, 2022-06-15) O’Brien, James ; McParland, Erin L. ; Bramucci, Anna R. ; Ostrowski, Martin ; Siboni, Nachshon ; Ingleton, Timothy ; Brown, Mark V. ; Levine, Naomi M. ; Laverock, Bonnie ; Petrou, Katherina ; Seymour, JustinThe organic sulfur compounds dimethylsulfoniopropionate (DMSP) and dimethyl sulfoxide (DMSO) play major roles in the marine microbial food web and have substantial climatic importance as sources and sinks of dimethyl sulfide (DMS). Seasonal shifts in the abundance and diversity of the phytoplankton and bacteria that cycle DMSP are likely to impact marine DMS (O) (P) concentrations, but the dynamic nature of these microbial interactions is still poorly resolved. Here, we examined the relationships between microbial community dynamics with DMS (O) (P) concentrations during a 2-year oceanographic time series conducted on the east Australian coast. Heterogenous temporal patterns were apparent in chlorophyll a (chl a) and DMSP concentrations, but the relationship between these parameters varied over time, suggesting the phytoplankton and bacterial community composition were affecting the net DMSP concentrations through differential DMSP production and degradation. Significant increases in DMSP were regularly measured in spring blooms dominated by predicted high DMSP-producing lineages of phytoplankton (Heterocapsa, Prorocentrum, Alexandrium, and Micromonas), while spring blooms that were dominated by predicted low DMSP-producing phytoplankton (Thalassiosira) demonstrated negligible increases in DMSP concentrations. During elevated DMSP concentrations, a significant increase in the relative abundance of the key copiotrophic bacterial lineage Rhodobacterales was accompanied by a three-fold increase in the gene, encoding the first step of DMSP demethylation (dmdA). Significant temporal shifts in DMS concentrations were measured and were significantly correlated with both fractions (0.2–2 μm and >2 μm) of microbial DMSP lyase activity. Seasonal increases of the bacterial DMSP biosynthesis gene (dsyB) and the bacterial DMS oxidation gene (tmm) occurred during the spring-summer and coincided with peaks in DMSP and DMSO concentration, respectively. These findings, along with significant positive relationships between dsyB gene abundance and DMSP, and tmm gene abundance with DMSO, reinforce the significant role planktonic bacteria play in producing DMSP and DMSO in ocean surface waters. Our results highlight the highly dynamic nature and myriad of microbial interactions that govern sulfur cycling in coastal shelf waters and further underpin the importance of microbial ecology in mediating important marine biogeochemical processes.
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ArticleThe osmolyte ties that bind: genomic insights into synthesis and breakdown of organic osmolytes in marine microbes(Frontiers Media, 2021-07-14) McParland, Erin L. ; Alexander, Harriet ; Johnson, Winifred M.The production and consumption of organic matter by marine organisms plays a central role in the marine carbon cycle. Labile organic compounds (metabolites) are the major currency of energetic demands and organismal interaction, but these compounds remain elusive because of their rapid turnover and concomitant minuscule concentrations in the dissolved organic matter pool. Organic osmolytes are a group of small metabolites synthesized at high intracellular concentrations (mM) to regulate cellular osmolarity and have the potential to be released as abundant dissolved substrates. Osmolytes may represent an essential currency of exchange among heterotrophic prokaryotes and primary and secondary producers in marine food webs. For example, the well-known metabolite dimethylsulfoniopropionate (DMSP) is used as an osmolyte by some phytoplankton and can be subsequently metabolized by 60% of the marine bacterial community, supplying up to 13% of the bacterial carbon demand and 100% of the bacterial sulfur demand. While marine osmolytes have been studied for decades, our understanding of their cycling and significance within microbial communities is still far from comprehensive. Here, we surveyed the genes responsible for synthesis, breakdown, and transport of 14 key osmolytes. We systematically searched for these genes across marine bacterial genomes (n = 897) and protistan transcriptomes (n = 652) using homologous protein profiles to investigate the potential for osmolyte metabolisms. Using the pattern of gene presence and absence, we infer the metabolic potential of surveyed microbes to interact with each osmolyte. Specifically, we identify: (1) complete pathways for osmolyte synthesis in both prokaryotic and eukaryotic marine microbes, (2) microbes capable of transporting osmolytes but lacking complete synthesis and/or breakdown pathways, and (3) osmolytes whose synthesis and/or breakdown appears to be specialized and is limited to a subset of organisms. The analysis clearly demonstrates that the marine microbial loop has the genetic potential to actively recycle osmolytes and that this abundant group of small metabolites may function as a significant source of nutrients through exchange among diverse microbial groups that significantly contribute to the cycling of labile carbon.