Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

This dataset contains observational and experimental stable isotope data.  Observational stable isotope data from infauna in sediment cores was collected at the “Jetty” dive site, Hutt Point, McMurdo Station, Antarctica. Seasonal sampling took place in September, November and February 2012-2013.  This dataset also includes stable isotope data from isotopic labeling and mesocosm experiments.

Methodology: 
Observational component: Sediment cores were collected at the “Jetty” dive site location in September, November and February 2012-2013.  These were sieved on a 300-micron sieve to collect macrofauna and sorted to putative species under a dissecting microscope, allowed to evacuate their guts overnight in 0.6 micron filtered seawater and then frozen at -80 C for later analysis.  All samples for these experiments were from the “Spiophanes beds” that are a dense infaunal community that is present at this location.

Manipulative experiment: 
Sediment cores were collected in mid September 2012 from four areas with dense Spiophanes beds and placed in the seawater tables at the Crary Lab at McMurdo station.  Treatments included with or without antibiotics (100 microgram l-1 Kanamycin) and with three different levels of food (freeze dried Phaeocystis antarctica) at levels of 0.04 grams to 0.17 grams representing different food stresses.  Replicate cores were sacrificed at time intervals (between 0.5 and 6 weeks) and kept in the dark.  At the termination of each core it was sieved and treated as above.

Pulse-chase experiment:
An additional selection of cores were taken in mid October and placed in the dark. Phaeocystis antarctica that had been grown on H13CO3 were added to the cores either with antibiotics or without and with 15NH4 to identify if antibiotics inhibited the uptake of NH4 and the routing of carbon through the macrofaunal community. At the termination of the experiment, all cores were sieved and fauna sorted as in the above observational and manipulative experiments.  
 
Sampling and analytical procedures:
All in dried overnight at 60 degrees, acidified using 1 M HCl, and their stable isotopic analysis measured at Washington State University on approximately 0.8 mg of tissue. Pulse chase and natural abundance samples were run separately. 

Isotopic analysis was measured on a Eurovector elemental analyzer interfaced with a continuous flow Micromass Isoprime isotope ratio mass spectrometer (irms) at Washington State University.

We are including raw data after eliminating data whose N and C peak response were insufficient for reliable isotopic data as they fell outside of the linear portion of the standard curve.

BCO-DMO Data Manager Processing Notes:
* added a conventional header with dataset name, PI name, version date
* modified parameter names to conform with BCO-DMO naming conventions
* parameter name modified for clarity: Concentration -> Fatty_Acid_Concentration
* updated coordinates in data for hutt point sample site based on correspondence with data contributor.

The biota of the world's seafloor is fueled by bursts of seasonal primary production. For food-limited sediment communities to persist, a balance must exist between metazoan consumption of and competition with bacteria, a balance which likely changes through the seasons. Polar marine ecosystems are ideal places to study such complex interactions due to stark seasonal shifts between heterotrophic and autotrophic communities, and temperatures that may limit microbial processing of organic matter. The research will test the following hypotheses: 1) heterotrophic bacteria compete with macrofauna for food; 2) as phytoplankton populations decline macrofauna increasingly consume microbial biomass to sustain their populations; and 3) in the absence of seasonal photosynthetic inputs, macrofaunal biodiversity will decrease unless supplied with microbially derived nutrition. Observational and empirical studies will test these hypotheses at McMurdo Station, Antarctica, where a high-abundance macro-infaunal community is adapted to this boom-and-bust cycle of productivity. The investigator will mentor undergraduates from a predominantly minority-serving institution, in the fields of invertebrate taxonomy and biogeochemistry. The general public and young scientists will be engaged through lectures at local K-12 venues and launch of an interactive website. The results will better inform scientists and managers about the effects of climate change on polar ecosystems and the mechanisms of changing productivity patterns on global biodiversity.