@article {4996,
	title = {Drifting along: Using diatoms to track the contribution of microbial mats to particulate organic matter transport in a glacial meltwater stream in the McMurdo Dry Valleys, Antarctica},
	journal = {Frontiers in Microbiology},
	volume = {15},
	year = {2024},
	month = {05/2024},
	abstract = {<p>Flow pulses mobilize particulate organic matter (POM) in streams from the surrounding landscape and streambed. This POM serves as a source of energy and nutrients, as well as a means for organismal dispersal, to downstream communities. In the barren terrestrial landscape of the McMurdo Dry Valleys (MDV) of Antarctica, benthic microbial mats occupying different in-stream habitat types are the dominant POM source in the many glacier-fed streams. Many of these streams experience daily flow peaks that mobilize POM, and diatoms recovered from underlying stream sediments suggest that mat-derived diatoms in the POM are retained there through hyporheic exchange. Yet, \&lsquo;how much\&rsquo; and \&lsquo;when\&rsquo; different in-stream habitat types contribute to POM diatom assemblages is unknown. To quantify the contribution of different in-stream habitat types to POM diatom assemblages, we collected time-integrated POM samples over four diel experiments, which spanned a gradient of flow conditions over three summers. Diatoms from POM samples were identified, quantified, and compared with dominant habitat types (i.e., benthic \&lsquo;orange\&rsquo; mats, marginal \&lsquo;black\&rsquo; mats, and bare sediments). Like bulk POM, diatom cell concentrations followed a clockwise hysteresis pattern with stream discharge over the daily flow cycles, indicating supply limitation. Diatom community analyses showed that different habitat types harbor distinct diatom communities, and mixing models revealed that a substantial proportion of POM diatoms originated from bare sediments during baseflow conditions. Meanwhile, orange and black mats contribute diatoms to POM primarily during daily flow peaks when both cell concentrations and discharge are highest, making mats the most important contributors to POM diatom assemblages at high flows. These observations may help explain the presence of mat-derived diatoms in hyporheic sediments. Our results thus indicate a varying importance of different in-stream habitats to POM generation and export on daily to seasonal timescales, with implications for biogeochemical cycling and the local diatom metacommunity.</p>},
	keywords = {LTER-MCM, cyanobacteria, diatom, flow regime, hydrology, microbial mat, Nostoc},
	doi = {10.3389/fmicb.2024.1352666},
	url = {https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2024.1352666/full},
	author = {Lee F. Stanish and Tyler J. Kohler and Darling, Joshua P. and Diane M. McKnight}
}
@article {4586,
	title = {Diatoms in hyporheic sediments trace organic matter retention and processing in the McMurdo Dry Valleys, Antarctica},
	journal = {Journal of Geophysical Research: Biogeosciences},
	volume = {126},
	year = {2021},
	month = {02/2021},
	pages = {e2020JG006097},
	abstract = {<p>In low-nutrient streams in cold and arid ecosystems, the spiraling of autochthonous particulate organic matter (POM) may provide important nutrient subsidies downstream. Because of its lability and the spatial heterogeneity of processing in hyporheic sediments, the downstream transport and fate of autochthonous POM can be difficult to trace. In Antarctic McMurdo Dry Valley (MDV) streams, any POM retained in the hyporheic zone is expected to be derived from surface microbial mats that contain diatoms with long-lasting silica frustules. We tested whether diatom frustules can be used to trace the retention of autochthonous POM in the hyporheic zone and whether certain geomorphic locations promote this process. The accumulation of diatom frustules in hyporheic sediments, measured as biogenic silica, was correlated with loss-on-ignition organic matter and sorbed ammonium, suggesting that diatoms can be used to identify locations where POM has been retained and processed over long timescales, regardless of whether the POM remains intact. In addition, by modeling the upstream sources of hyporheic diatom assemblages, we found that POM was predominantly derived from N-fixing microbial mats of the genus Nostoc. In terms of spatial variability, we conclude that the hyporheic sediments adjacent to the stream channel that are regularly inundated by daily flood pulses are where the most POM has been retained over long timescales. Autochthonous POM is retained in hyporheic zones of low-nutrient streams beyond the MDVs, and we suggest that biogenic silica and diatom composition can be used to identify locations where this transfer is most prevalent.</p>},
	keywords = {LTER-MCM, benthic processes, biogenic silica, biogeochemical cycles processes and modeling, carbon cycling, diatoms, groundwater/surface water interactions, hyporheic zone, McMurdo Dry Valleys, nitrogen cycling, particulate organic matter},
	doi = {10.1029/2020JG006097},
	url = {https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020JG006097},
	author = {Heindel, Ruth C and Darling, Joshua P. and Singley, Joel G. and Bergstrom, Anna J. and Diane M. McKnight and Lukkari, Braeden M. and Kathleen A. Welch and Michael N. Gooseff}
}
