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.

Isotopes.csv