01902nas a2200181   4500008004100000245011100041210006900152260003900221490000900260520124000269653001901509653002401528653002601552653001801578100002601596700002901622856006901651       2020                        eng d00aResponse of microbial communities to climatic disturbances in Lake Bonney, McMurdo Dry Valleys, Antarctica0 aResponse of microbial communities to climatic disturbances in La  aOxford, OHbMiami Universityc20200 vM.S.3 a<p>The McMurdo Dry Valleys is a polar desert ecosystem which composes the largest ice-free area in Antarctica, with the exception of perennially ice-covered lakes and ponds. The lakes in the valleys are the only landscape unit that support metabolic activity year-round. Recent increases in air temperature and solar radiation have led to a chain of disturbances altering the environmental conditions of these lakes. In this study, we test the impact of climatic disturbances on microbial communities in Lake Bonney, one of the lakes in the MDV. Through an integrated approach of combining field studies on natural communities in the lake (in situ) and laboratory experiments on algal isolates (ex situ), this study will attempt to understand how phytoplankton, eukaryal and bacterial communities respond to simulated disturbances. Results from the in situ experiments showed that the moat is a unique and stressful environment for under-ice communities and that under-ice shallow communities are highly sensitive to climatic disturbances. The ex situ experiments showed that certain phytoplankton species, like the chlorophytes, are more resistant to environmental alterations and thus will outcompete other phytoplankton species.</p>10aclimate change10aMcMurdo Dry Valleys10amicrobial communities10aphytoplankton1 aSherwell, Shasten, S.1 aMorgan-Kiss, Rachael, M.  uhttp://rave.ohiolink.edu/etdc/view?acc_num=miami159595868836487702691nas a2200229   4500008004100000022001400041245015500055210006900210260001200279490000700291520189400298653003402192653001902226653002402245653002202269653002302291100002202314700001202336700002002348700002902368856006402397       2017                        eng d  a0722-406000aImpact of nitrogen and phosphorus on phytoplankton production and bacterial community structure in two stratified Antarctic lakes: a bioassay approach0 aImpact of nitrogen and phosphorus on phytoplankton production an  c05/20170 v403 a<p>Arctic, Antarctic, and alpine ecosystems are recognized as sensors and sentinels of global change. As a consequence of their high sensitivity to minor climatic perturbations, permanently ice-covered lakes located in the McMurdo Dry Valleys (MDV), Antarctica, represent end members in the global network of inland bodies of water. Episodic climatic events in the form of increased summer glacial melt result in inputs of organic sediment and nutrients from glacial streams to these closed basins. Phytoplankton communities residing in the oligotrophic water columns are highly responsive to pulses in nutrient availability; however, there is a lack of understanding on whether specific phytoplankton groups are more competitive during a summer flood event and how shifts in the phytoplankton community may influence heterotrophic bacteria. A bioassay approach in 3-l bottles was used to investigate the influence of inorganic nitrogen and phosphorus availability on planktonic communities from the oligotrophic upper waters of two chemically distinct MDV lakes (Lakes Bonney and Fryxell) which differ in their external inputs and water column N/P stoichiometry. While microbial community responses varied between lakes and were nutrient-dependent, stimulation of phytoplankton biomass and productivity across all treatments was strongly linked with increased abundance of a single phytoplankton phylum (Chlorophyta). Despite stimulation of phytoplankton growth, primary and bacterial productivity was generally uncoupled; however, shifts in bacterial community diversity were observed in bioassays amended with either P or NP. We suggest that climate-associated increases in phytoplankton production and concomitant shifts in diversity will influence MDV bacterial community structure by altering the availability and composition of autochthonous carbon for heterotrophic production.</p>10aAlgal–bacteria interactions10aclimate change10aMcMurdo Dry Valleys10aNutrient bioassay10aPrimary production1 aTeufel, Amber, G.1 aLi, Wei1 aKiss, Andor, J.1 aMorgan-Kiss, Rachael, M.  uhttps://link.springer.com/article/10.1007/s00300-016-2025-804197nas a2200253   4500008004100000245012900041210006900170260003900239490001000278520331600288653001503604653002503619653002903644653002903673653002103702653001903723653002403742653002303766653001703789653002303806100002203829700002903851856006303880       2016                        eng d00aInfluence of abiotic drivers (light and nutrients) on photobiology and diversity of Antarctic lake phytoplankton communities0 aInfluence of abiotic drivers light and nutrients on photobiology  aOxford, OHbMiami Universityc20160 vPh.D.3 a<p>Arctic, Antarctic, and alpine ecosystems are recognized as sensors and sentinels of global climate change. As a consequence of their high sensitivity to minor climatic perturbations, permanently ice-covered lakes located in the McMurdo Dry Valleys (MCM), Antarctica, represent end members in the global network of inland bodies of water. Episodic climatic events in the form of increased summer glacial melt result in inputs of organic sediment and nutrients from glacial streams to these closed basins. By better understanding how Antarctic lake communities respond to mimicked climate change, we can more accurately predict how they will react to further temperature changes in the future. We began by investigating the influence of inorganic nitrogen and phosphorus availability on planktonic communities residing in the oligotrophic upper waters of two chemically distinct MCM lakes (Lakes Bonney and Fryxell) which differ in their external inputs as well as water column N:P stoichiometry. Although microbial community responses varied between the lakes and were nutrient-dependent, stimulation of phytoplankton biomass and productivity across all treatments was strongly linked with increased abundance of a single phytoplankton phylum (Chlorophyta). Despite stimulation of phytoplankton growth, primary and bacterial productivity were largely uncoupled across all enrichments. We suggest that climate-associated shifts in phytoplankton diversity influence the bacterial community structure by altering the availability and composition of autochthonous carbon for heterotrophic production. To monitor the physiological adaptations that occur over time and depth, we then transplanted two dominant phytoplankton, <em>Chlamydomonas</em> sp. ICE- MDV and <em>Isochrysis</em> sp. MDV back into the Lake Bonney water column. Our results demonstrated that both organisms are specialists for surviving specific depths of the water column and are capable of acclimating to their native environment within a short period of time, and that the chlorophyte <em>Chlamydomonas</em> sp. ICE-MDV most likely makes this adjustment via photoacclimation and accumulating chlorophyll-a per cell. The final study presented here investigated whether or not the dominant chlorophyte, <em>Chlamydomonas</em> sp. ICE-MDV has retained the ability to respond to a diel 12-hour day/night cycle. Although light levels in MCM lakes remain low during the austral summers, daily irradiation varies by as much as tenfold during the course of the day, resulting in a circadian-like light cycle for organisms residing there. With decreased ice coverage on the lakes due to climate change and increased melt, it is likely that these light variations will become amplified over time. This study tested for the presence of a circadian rhythm under various light quality, light quantity, and temperature conditions and demonstrated that although a diel rhythm was maintained in terms of growth and several photochemical parameters, a true circadian rhythm was not identified. Although it is predicted that photosynthetic communities in polar regions will be more responsive to climate warming and episodic events, the complexity of these systems provides numerous challenges to understanding how these organism will adapt in the future.</p>10aAntarctica10abacterial production10aChlamydomonas sp ICE MDV10aChlorophyll fluorescence10acircadian rhythm10aclimate change10aMcMurdo Dry Valleys10anutrient amendment10aphotobiology10aPrimary production1 aTeufel, Amber, G.1 aMorgan-Kiss, Rachael, M.  uhttp://rave.ohiolink.edu/etdc/view?acc_num=miami1468411564