McMurdo region meltwater ponds bacterioplankton survey

Study Extent

Sampling area; Bratina Island ponds located within 1km from the study camp on the McMurdo Ice Shelf. Miers Valley ponds within 1km of the eastern mouth of the valley Temporal - Samples were collected during the Austral summer in November 2009, January 2012 and January 2013, a single time point per pond per year

Sampling

Ponds were initially identified at Bratina Island using a map based on one produced by New Zealand Department of Land and Surveys, 1991. General pond surveys were also conducted from the edge of the pond, ponds suspected of having a stratified water column had samples collected from the approximate center of the pond using a micromanipulator sampling apparatus at increments ranging from 0.5 to 80 cm guided by changes in pH and conductivity in the water column. Up to 40 samples were collected from a single water column. Before sampling the tube was flushed with 2 void volumes (at each depth) before each sample was collected then 5-120 mL of sample was immediately filtered through syringe-mounted 0.22 μm filters (Whatman International Ltd, Kent, UK) until the filter clogged. A small amount of air was pushed through the filter to remove excess water, then gently flooded with a nucleic acid preservative/lysis buffer (CTAB - cetyltrimethylammonium bromide-polyvinylpyrrolidone-β-mecaptoethanol) and frozen for transport back to the laboratory. Thirteen mL of the filtrate was collected during sampling in 15 mL falcon tubes, and frozen immediately for later geochemical analysis. In situ measurement of water temperature, conductivity, pH and oxygen concentration were determined using a variety of regularly calibrated hand-held instruments. Sediment cores, four-centimeters in depth, were collected from the edge of 19 fully thawed meltwater ponds during the summer season in January 2012 (6 ponds) and January 2013 (7 ponds) from Bratina Island (78° 01' S, 165° 32' E) and the Miers Valley (6 ponds) (78° 07' S, 164° 12' E). A total of 26 samples were collected including triplicates from Huey (2012 and 2013) and P70E (2013) ponds, Bratina Island (Table 1). Sites were selected to encompass a broad range of surface water geochemistries (Chapter 3) from a comparative set of ponds at each location. Cores were aseptically collected using a disposable push-corer developed from a 50mL syringe (BD, Singapore). The corer (with the plunger removed) was inserted 4-6cm into the sediment, the plunger reinserted and corer removed carefully to retain the sediment structure. After excess sediment was removed each core was sub-sectioned into four one-centimeter samples into a sterile 15 oz whirlpack (Nasco, WI, USA) for individual DNA extraction then frozen for transportation to the laboratory. In-situ measurements of dissolved oxygen, pH, Temperature and conductivity were measured using an HQ40d portable multi-parameter meter (Hach Company, CO, USA).

Quality Control

All sampling apparatus was sterilised with ethanol and washed with MQ H20 to ensure environment and samples were not biologically contaminated. Hand held meters were calibrated before each sampling session to ensure accurate measurements.

Method steps

1. Sampling procedure

Bacteria

1. Bacteria

Bratina Island, Miers Valley