In 2007 we established a multiple nutrient addition experiment to examine how biotic responses to stoichiometric manipulations are constrained by landscape history and native geochemistry, e.g., soil N:P ratios (Fig. 1).
We are investigating the effect of increased connectivity among dry valley habitats on lake biodiversity and biogeochemistry in the Lake Ice Connectivity Experiment (LICE). Under a scenario of increased connectivity, we expect lakes to experience increased input from streams, aeolian sediments and lake margin soils, fluvially deposited algal/cyanobacterial mats, and in general, increased nutrient input.
Our long-term “Relict Channel” experiment initiated during MCM I has yielded insights into the controls of flow regime on the microbial mat composition and in-stream nutrient cycling sustains their function as regulating connectivity across the Dry Valley landscapes (McKnight et al., 2007; Stanish et al., 2012, Kohler et al 2018, Wlostkowski et al 2019).
The open water lake margins or “moats” surrounding the lakes are highly dynamic and are a nexus of interaction with other habitats: connecting with inundated soils, interfacing and exchanging with the atmosphere, and mixing with stream inflows, and the under-ice lake water column. The moat systems are also one of the most rapidly changing habitats in the MDV.
The microbial mats in the streams regulate the fluvial flux of nutrients, dissolved organic matter (DOM) and coarse particulate matter (CPOM) from the landscape to the lakes (Gooseff et al 2004, Cullis et al. 2014). Thus, processes that control the persistence of these mats over varying flow influence connectivity across the landscape.
The human disturbance study addresses the third hypothesis (H3) of the MCM V proposal: ‘Disturbance increases connectivity and accelerates shifts towards homogeneity in ecosystem structure and functioning in the MDVs.’ By using historical research alongside soil sampling at sites of past human activity in the MDV, the human disturbance study sets out to assess the long term (30+ years) legacy of human activities on the MDV ecosystem.
tLICE was designed to consider the impact of increased connectivity between MCM landscapes on community stability. Natural planktonic communities of Lakes Bonney (east lobe) and Fryxell collected from either the liquid moats or the under-ice communities are transferred to dialysis bags and suspended in the water column at various locations.
The Permafrost Degradation Experiment (PDE) is designed to quantify the changes in stream and riparian communities and processes when permafrost degradation along streambanks causes significant input of sediment to streams (Gooseff et al., 2016; Sudman et al., 2015).
Although it may seem that the streams of the McMurdo Dry Valleys are not well connected to the surrounding dry soils, the aeolian transport of sediment, snow, particulate organic matter, and viable organisms into the stream channels may be an important vector of connectivity between soils and streams.
We are measuring the reflection of shortwave radiation across the MDV landscape to quantify how the reflectance evolves in a single season, and how it changes year to year.
Microbial eukaryotes play critical roles in the MCM ecosystems as the major primary producers at the base of the food webs through top predators. Our new focus on microbial eukaryotes contributes to addressing all 4 of our working hypotheses and are a critical part of several new and ongoing experiments (LICE, tLICE, SLIME).
In 2011 we initiated a long-term study to test hypotheses about how the MCM soil ecosystem will respond to climate-mediated changes to permafrost. Our objective was to simulate different frequencies of permafrost thawing events and characterize their associated impacts on soil communities and biogeochemical cycles.
In 2012, Doran, Priscu, and Takacs-Vesbach were awarded a NASA equipment grant under the Exobiology Program to purchase a suite of autonomous lake sampling and monitoring equipment to acquire year-round physical and biological data for the first time. This grant was followed by an NSF EAGER award to establish the equipment in Lake Bonney and keep it running for a number of years.
Beginning the 2010-2011 season, we have installed a telemetry network that utilizes the Iridium satellite network and radios to connect 14 meteorological stations, 8 stream gages, and five lake monitoring stations to transfer data year round.
Although the abundance and diversity MDV biota is low relative to most other ecosystems, recent and ongoing work reveals that representative taxa from most of the major lineages of the Tree of Life are present and functioning.
Ernest Shackleton’s Hut at Cape Royds is among the most famous historic sites on the Antarctic Continent. Recent years have seen Shackleton’s stature grow as the Antarctic explorer who led by example and “never lost a man,” largely at the expense of the reputation of Captain Scott who is often seen as having been somewhat aloof and distant from his men.
STEM Outreach: Through a partnership with CU’s 'Learn More About Climate' program, Ph. D. student Alex Mass has been engaging students in the Denver/Boulder area and beyond through their interest in Antarctica to promote learning in STEM fields. Alex held a Chancellor’s Fellowship for Excellence in STEM Education