A hierarchical, 3-level, nested design was used. The highest hierarchical level consisted of six locations. Two of these locations, Brown Bay and Shannon Bay, have been contaminated with heavy metals (Stark et al., 2003; Snape et al., 2001); Brown Bay has also been contaminated with petroleum hydrocarbons (Snape et al., 2001). The remaining four locations are more distant from Casey Station and were used as control locations. These locations were Denison Island, Odbert Island, O'Brien Bay and Sparkes Bay. A full description of these sites is given below. Within each location two sites were selected approximately 100 m apart. Within each site, two plots were sampled (~ 10 m apart). Although the sampling program had been designed for four replicates within each plot, the patchy distribution of bottom sediments in the Windmill Islands restricted this to two replicate samples (~ 1 m apart) per plot. Samples were collected using an Eckman grab sampler, deployed from a boat. To minimise the potential influence of water depth, all samples were collected from 8 m water depth. Samples were collected within a three day period in early February when no sea-ice was present. Diatom data are presented as the relative abundances of benthic species. Samples are identified xyz where x = first initial of sample location (or first 2 initials where 2 locations start with the same letter), y = plot number (plots 1 and 2 represent site 1, while plots 3 and 4 are from site 2), and z = replicate number (a or b). Abbreviations used for species are shown in the separate file sp_list. This work was completed as part of ASAC project 1130 (ASAC_1130) and project 2201 (ASAC_2201). Public summary from project 1130: Algal mats grow on sea floor in most shallow marine environments. They are thought to contribute more than half of the total primary production in many of these areas, making them a critical food source for invertebrates and some fish. We will establish how important they are in Antarctic marine environments and determine the effects of local sewerage and tip site pollution. We will also investigate the impact on the algal mats of the additional UV radiation which results from the ozone hole. Public summary from project 2201: As a signatory to the Protocol on Environmental Protection to the Antarctic Treaty Australia is committed to comprehensive protection of the Antarctic environment. This protocol requires that activities in the Antarctic shall be planned and conducted on the basis of information sufficient to make prior assessments of, and informed judgements about, their possible impacts on the Antarctic environment. Most of our activities in the Antarctic occur along the narrow fringe of ice-free rock adjacent to the sea and many of our activities have the potential to cause environmental harm to marine life. The Antarctic seas support the most complex and biologically diverse plant and animal communities of the region. However, very little is known about them and there is certainly not sufficient known to make informed judgements about possible environmental impacts The animals and plants of the sea-bed are widely accepted as being the most appropriate part of the marine ecosystem for indicating disturbance caused by local sources. Attached sea-bed organisms have a fixed spatial relationship with a given place so they must either endure conditions or die. Once lost from a site recolonisation takes some time, as a consequence the structure of sea-bed communities reflect not only present conditions but they can also integrate conditions in the past. In contrast, fish and planktonic organisms can move freely so their site of capture does not indicate a long residence time at that location. Because sea-bed communities are particularly diverse they contain species with widely differing life strategies, as a result different species can have very different levels of tolerance to stress; this leads to a range of subtle changes in community structure as a response to gradually increasing disturbance, rather than an all or nothing response. This project will examine sea-bed communities near our stations to determine how seriously they are affected by human activities. This information will be used to set priorities for improving operational procedures to reduce the risk of further environmental damage. The fields in this dataset are: Species Site Abundance Benthic

Sediment samples were collected from four locations within the Windmill Islands (Cloyd Island, Odbert Island, Shannon Bay and Brown Bay). Within each location three parallel transects were created, with samples taken at set depths along each transect. At the time of collection, both surface and benthic irradiance levels were measured, and the % of surface irradiance that reached the sediment-water interface was calculated. Samples were analysed for benthic diatom abundances (expressed as relative abundances), and grain-size (expressed as % of total weight). The diatom spreadsheet (diatom_data)lists the relative abundance of benthic species. The abbreviation used to identify species are explained in the separate file called sp_list. Samples are identified XTYZ where X is the first letter of the location, Y indicates the sampling position along the transect and z indicates the transect (a, b or c). The benthic sheet is the relative abundances of benthic species. The greater than 2% sheet lists all the species that reach abundances greater than2% in at least 1 sample. The table sheet has the same info as greater than 2% but arranged by the individual locations. In this sheet (tables), measurements in m represent the depth of the water column overlying the position where the sediment samples were collected. (ie it was at different locations, not different water depths in the one spot). Sampling positions reflect increasing depth. At Brown Bay and Odbert Island, sediment samples were collected below water columns/water depths of 1, 2, 4, 8 and 12 m. At Cloyd Island, samples were collected from 4,6,8 and 12 m water depths. At Shannon Bay samples were collected from 2, 4, 8, and 12 m water depths. Details of the environmental parameters examined (grainsize and light) are given in the file labelled 'env_data' This work was completed as part of ASAC project 1130 (ASAC_1130). Public summary from project 1130: Algal mats grow on sea floor in most shallow marine environments. They are thought to contribute more than half of the total primary production in many of these areas, making them a critical food source for invertebrates and some fish. We will establish how important they are in Antarctic marine environments and determine the effects of local sewerage and tip site pollution. We will also investigate the impact on the algal mats of the additional UV radiation which results from the ozone hole. The fields in this dataset are: Diatom Spreadsheet Species Site Location Transect Depth (m) Environmental Data Spreadsheet Location Transect Depth (m) Grain size Gravel Sand Mud Light

In situ measurements of ice and snow thickness, and freeboard along an irregular transect on the fast, complementing the repeat ROV (Remotely Operated Vehicle) transects. During our deployment at Davis in 2015 logistics and environmental conditions permitted measurements along 4 transects. The location of the reference grid (ROV box) had its origin (x=0, y=0) at (-68.568904 degrees N,+77.945439 degrees E). Transects 1 – 4 started at x=60, x=70, x=80 and x=90 m and were sampled at y-positions of 0m, 0.5m, 1m, 2m, 4m, 8m, 16m, 32m, 64m, 128m, (256m, and 512m), respectively. Depending on working conditions the overall transect lengths varied from 128 – 512 m. Sampling dates for in situ ice physcis: Transect ID Date of sampling Zice and FB measured at Ice core taken at Snowpit measured at T1 19/11/2015 0, 0.5, 1, 2, 4, 8, … 64m. 0m, 128m, 512m 0m, 128m, 512m T2 23/11/2015 0, 0.5, 1, 2, 4, 8, … 64m. 0m, 128m, 512m 0m, 128m T3 29/11/2015 0, 0.5, 1, 2, 4, 8, … 64m. 0m, 128m 0m, 128m T4 02/12/2015 0, 0.5, 1, 2, 4, 8, … 64m. 0m, 128m 0m, 128m Ice cores and snow pits were collected at the 0m, 50m and 100m mark along the transect, where possible. Additionally, ice cores for density analysis were taken at a few of the ice-core sites for independent verification of ice density.

Sediment samples were collected from nine points along 3 parallel transects within the contaminated Brown Bay. The diatom spreadsheet (diatom_data) contains both initial diatom counts and the relative abundance of benthic species. The abbreviation used to identify species are explained in the separate file called sp_list. Metal, Total Purgeable Hydrocarbons (TPH), and grain-size data are all presented as separate files. This work was completed as part of ASAC project 1130 (ASAC_1130) and project 2201 (ASAC_2201). Public summary from project 1130: Algal mats grow on sea floor in most shallow marine environments. They are thought to contribute more than half of the total primary production in many of these areas, making them a critical food source for invertebrates and some fish. We will establish how important they are in Antarctic marine environments and determine the effects of local sewerage and tip-site pollution. We will also investigate the impact on the algal mats of the additional UV radiation which results from the ozone hole. Public summary from project 2201: As a signatory to the Protocol on Environmental Protection to the Antarctic Treaty Australia is committed to comprehensive protection of the Antarctic environment. This protocol requires that activities in the Antarctic shall be planned and conducted on the basis of information sufficient to make prior assessments of, and informed judgements about, their possible impacts on the Antarctic environment. Most of our activities in the Antarctic occur along the narrow fringe of ice-free rock adjacent to the sea and many of our activities have the potential to cause environmental harm to marine life. The Antarctic seas support the most complex and biologically diverse plant and animal communities of the region. However, very little is known about them and there is certainly not sufficient known to make informed judgements about possible environmental impacts The animals and plants of the sea-bed are widely accepted as being the most appropriate part of the marine ecosystem for indicating disturbance caused by local sources. Attached sea-bed organisms have a fixed spatial relationship with a given place so they must either endure conditions or die. Once lost from a site recolonisation takes some time, as a consequence the structure of sea-bed communities reflect not only present conditions but they can also integrate conditions in the past. In contrast, fish and planktonic organisms can move freely so their site of capture does not indicate a long residence time at that location. Because sea-bed communities are particularly diverse they contain species with widely differing life strategies, as a result different species can have very different levels of tolerance to stress; this leads to a range of subtle changes in community structure as a response to gradually increasing disturbance, rather than an all or nothing response. This project will examine sea-bed communities near our stations to determine how seriously they are affected by human activities. This information will be used to set priorities for improving operational procedures to reduce the risk of further environmental damage. The fields in this dataset are: bbg_lat spreadsheet Site Latitude Longitude Easting Northing Diatoms spreadsheet Species Site Abundance Transect Metals Spreadsheet Sample Antimony Arsenic Cadmium Chromium Copper Iron Lead Manganese Mercury Nickel Silver Tin Zinc Total Organic Carbon Easting Northing TPH Spreadsheet Site Total Purgeable Hydrocarbons Fraction of Purgeable Hydrocarbons