Spatial and temporal patterns of microbial mats and associated invertebrates along an Antarctic stream
Microbial biofilms are biological hotspots in many alpine and polar ecosystems, but the controls on and functional significance of their fauna are little known. We studied cyanobacterial mats and the underlying sediment in a glacial meltwater stream in the McMurdo Dry valleys, Antarctica. We investigated mat biomass (total and phototrophic), diatoms, and micro-meiofauna (nematodes, rotifers, and tardigrades) at nine sites along a 1670 m stream reach in a cold, low-flow growing season, and in a warmer growing season in which peak flows (above 100 L s−1) scoured the mats. Diatom and invertebrate communities were not related, but mat biomass in the low-flow year was negatively related to nematode abundance, including that of the omnivore Eudorylaimus. In the high flow year that followed, invertebrate abundance was reduced in the mats, diatom community structure was altered, and mat biomass was higher. The difference in invertebrate abundance between years was greater in mats in upstream reaches, where the greatest increases in flow velocity may have occurred, and was negligible in mats in downstream reaches as well as in the sediment beneath the mats. Integrating our results with previous findings, we generate two predictive hypotheses to be tested in glacial meltwater streams: (1) under peak flows invertebrates decline in the microbial mats, while (2) the sediment beneath the mats is a refuge from the flow disturbance. Our results also suggest that, under stable flow conditions, microinvertebrate grazers could exert top-down control on microbial mat biomass.
KeywordsDiatoms Disturbance Dry valleys Epilithon Microfauna Streamflow
We thank Uffe Nielsen, Karen Seaver and Tracy Smith for helping with sampling and invertebrate identification, and Eric Parrish for updating the field site map. This research was conducted as part of the McMurdo dry valleys Long Term Ecological Research project, NSF OPP Grants 9211773, 9810219 and 1115245. Geospatial support for this work was provided by the Polar Geospatial Center under NSF OPP awards 1043681 and 1559691. Comments by three anonymous reviewers helped us improve the text.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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