IMIS

The primary goal of the AMLR winter cruise was to establish the ecological importance of winter processes and plankton distributons particularly as related to sea ice and to capture the hydrography and winter distributions of krill for comparisons with summer conditions over this long times series study. The winter time study will help determine how the template for ecological success is set up for summertime production across all trophic levels. The picoplankton research will improve the understanding of winter distributions and provide sample collection opportunities for diversity and biogeochemical studies to create an integrated ecosystem picture that will be developed with the NOAA AMLR group. In particular, this effort will extend the geographic coverage of winter picoplankton in the South Shetland Islands region, both on and off the continental slope. This is important to test hypotheses concerning high latitude winter processes that were observed in coastal Antarctic Peninsula waters suggesting the relative importance of chemolithoautotrophy is a key winter-time metabolic process.
Geographic coverage: This is the U.S. Antarctic Marine Living Resources study area. Hydrographic surveys were conducted across three broad sub-areas in this region, around Elephant Island, in the Bransfield Strait, west of the South Shetland Islands.
Taxonomic coverage: Bacterial, archaeal, and eukaryotic diversity in seawater picoplankton (< 3.0 micron fraction) and the diversity of the sea ice microbial community were described based on small subunit ribosomal RNA amplicon sequencing.
Sampling method: Hydrographic surveys were conducted using CTD rossette outfitted with niskin bottle samplers to retrieve water samples at 15, 50, 75, 100, 200, and 750 m (or above the bottom if bottom depth was shallower than 750 m). Water was filtered immediately once on board the ship in a cold room at 0C. Samples for DNA extraction and subsequent sequencing were passed through in-line 2.7 micron filters to remove larger organisms, and the picoplankton fraction was collected on 0.2 micron Sterivex cartridge filters. A sucrose-Tris-EDTA buffer was added to the filters and they were stored frozen at -80C until extraction at our home institutions.
Quality control: Nucleic extraction blanks were carried out through amplification steps and sequence analysis quality control measures were followed on data analyzed. Oceanographic instruments were calibrated at SeaBird before the cruise and sample blanks were periodically run for chlorophyll and nutrient analyses.