@article {2832,
	title = {Permafrost Hydrology Drives the Assimilation of Old Carbon by Stream Food Webs in the Arctic},
	journal = {Ecosystems},
	volume = {23},
	year = {2020},
	month = {Jan-03-2020},
	pages = {435 - 453},
	abstract = {Permafrost thaw in the Arctic is mobilizing old carbon (C) from soils to aquatic ecosystems and the atmosphere. Little is known, however, about the assimilation of old C by aquatic food webs in Arctic watersheds. Here, we used C isotopes (δ13C, Δ14C) to quantify C assimilation by biota across 12 streams in arctic Alaska. Streams spanned watersheds with varying permafrost hydrology, from ice-poor bedrock to ice-rich loess (that is, yedoma). We measured isotopic content of (1) C sources including dissolved organic C (DOC), dissolved inorganic C (DIC), and soil C, and (2) stream biota, including benthic biofilm and macroinvertebrates, and resident fish species (Arctic Grayling (Thymallus arcticus) and Dolly Varden (Salvelinus malma)). Findings document the assimilation of old C by stream biota, with depleted Δ14C values observed at multiple trophic levels, including benthic biofilm (14C ages = 5255 to 265 years before present (y BP)), macroinvertebrates (4490 y BP to modern), and fish (3195 y BP to modern). Mixing model results indicate that DOC and DIC contribute to benthic biofilm composition, with relative contributions differing across streams draining ice-poor and ice-rich terrain. DOC originates primarily from old terrestrial C sources, including deep peat horizons (39{\textendash}47\%; 530 y BP) and near-surface permafrost (12{\textendash}19\%; 5490 y BP). DOC also accounts for approximately half of fish isotopic composition. Analyses suggest that as the contribution of old C to fish increases, fish growth and nutritional status decline. We anticipate increases in old DOC delivery to streams under projected warming, which may further alter food web function in Arctic watersheds.},
	issn = {1432-9840},
	doi = {10.1007/s10021-019-00413-6},
	url = {https://link.springer.com/article/10.1007\%2Fs10021-019-00413-6},
	author = {O{\textquoteright}Donnell, Jonathan A. and Carey, Michael P. and Koch, Joshua C. and Xu, Xiaomei and Poulin, Brett A. and Walker, Jennifer and Zimmerman, Christian E.}
}
@article {2761,
	title = {Implications of radiocarbon ages of organic and inorganic carbon in coastal lakes in Florida for establishing a reliable chronology for sediment-based paleoclimate reconstructionAbstract},
	journal = {Quaternary Research},
	volume = {91},
	year = {2019},
	month = {Jan-03-2019},
	pages = {638 - 649},
	abstract = {Coastal lake sediments are valuable paleoclimate archives provided that they can be accurately dated. Here, we report radiocarbon ages of bulk sediment organic matter (OM), plants, shells, particulate OM, and dissolved OM from coastal lakes in Florida. Bulk sediment OM yielded ages that are consistently older than contemporaneous plants and shells, indicating significant radiocarbon deficiencies in sedimentary OM in these lakes. The data show that the OM radiocarbon deficiency varies over time and with location, making it impossible to determine a proper correction factor for radiocarbon ages of bulk sediments from these lakes. As a result, we consider ages obtained from bulk sediment OM from these lakes unreliable. The age reversals in bulk sediment OM observed in the sediment cores are likely caused by rapid increases in erosion and sedimentation resulting from large storm events. The data also show that sedimentation rate can vary considerably within a given lake, implying that an age-depth model established for one core cannot be directly applied to other cores despite their close proximity. Analyses of shells from one of the lakes suggest that fresh/brackish-water shells may serve as a good substrate for radiocarbon dating owing to a small reservoir effect on inorganic carbon.},
	issn = {0033-5894},
	doi = {10.1017/qua.2018.96},
	url = {https://www.cambridge.org/core/product/identifier/S0033589418000960/type/journal_article},
	author = {Wang, Yang and Das, Oindrila and Xu, Xiaomei and Liu, Jin and Jahan, Shakura and Means, Guy H. and Donoghue, Joseph and Jiang, Shijun}
}
