This metadata record contains the results from 11 bioassays conducted with 2 species of Antarctic marine microalgae. Seven tests were conducted with Phaeocystis antarctica (Prymnesiophyceae), assessing the toxicity of copper, cadmium, lead, zinc and nickel. Four tests were conducted with Cryothecomonas armigera (Incertae sedis), assessing the toxicity of copper only.
Test conditions for both algae are described in the excel spreadsheets. In summary, tests for P. antarctica and C.armigera, were carried out at 0 plus or minus 2 degrees C, 20:4 h light:dark (150-200 micro mol/m2/s, cool white 36W/840 globes), in natural filtered (0.45 microns for P.antarctica and 0.22 microns filtered for C. armigera) seawater (salinity - 35 ppt, pH - 8.1 plus or minus 0.2). For both species, filtered seawater was supplemented with 1.5 mg/L NO3- and 0.15 mg/L of PO43-. All tests were carried out in silanised 250-mL glass flasks, with glass lids. Test volumes for P.antartica and C.armigera were 50 mL and 80 mL, respectively.
All tests consisted of 3-5 metal treatments, with 3 replicates per treatment, alongside 3 replicate controls (natural filtered seawater). Seawater was spiked with metal solutions to achieve required concentration. Concentrations tested are recorded in excel datasheets. The following replicate toxicity tests were completed for P. antarctica:
- 5 tests with copper (1-20 micro g/L)
- 4 tests with lead (10-500 micro g/L)
- 3 tests with cadmium (100-2000 micro g/L)
- 3 tests with zinc (100-2000 micro g/L)
- 3 tests with nickel (200-1000 micro g/L)
For C. armigera, 1 rangefinder test was carried out testing 6 concentrations (1-100 micro g/L), and 3 definitive test, with 5 concentrations (15-100 micro g/L).
The age of P. antarctica and C.armigera at test commencement was 8-12 days, and 25-30 days, respectively. Algal cells were centrifuged and washed to remove nutrient rich media, and test flasks were inoculated with between 1-3 x103 cells/mL.
Cell densities in all toxicity tests were determined by flow cytometry. The flow cytometer was also used to simultaneously measure change sin chlorophyll a fluorescence intensity, cell size and internal cell granularity.
Toxicity tests were continued until cell densities in the control treatments had increased 16-fold. Toxicity tests with P. antarctica were carried out over 10 days, with cell densities in each replicate flask measured every 2 days. Toxicity tests with C. armigera were carried out over 23-24 days, with cell densities determined twice a week. The growth rate (cell division; u) was calculated as the slope of the regression line from a plot of log10 (cell density) versus time (h). Growth rates for all treatments were expressed as a percentage of the control growth rates.
The pH in all treatments was measured on the first and last day of the test, as well as on day 6 for P. antarctica tests and an additional two times per week for C. armigera tests. Sub-samples (5 mL) for analysis of dissolved metal concentrations were taken from each treatment on days 0, 6 and 10 for P. antarctica tests, and on days 0, 7, 14, 21, and 24 for C. armigera tests. Sub-samples were filtered through an acid washed (10% HNO3, Merck) 0.45-micron membrane filter and syringe, and acidified to 0.2% with Tracepur nitric acid (Merck). All toxicity test results were calculated using measured dissolved metal concentrations, which were determined using inductively coupled plasma-atomic emission spectrometry (ICP-AES; Varian 730-ES) for Cu, Cd, Pb, Ni and Zn and using inductively coupled plasma-mass spectrometry (ICP-MS; Agilent 7500CE) for lowest concentration Cu samples (nominal concentration 1 micro g/L). Detection limits for Cu, Cd, Pb, Ni and Zn were 1, 0.12, 1.7, 1.2 and 0.1 micro g/L, respectively (ICP-AES) and 0.05 micro g/L (ICP-MS) for low concentration Cu samples.
The specific growth rates (u) and corresponding measured metal concentrations were used to calculate toxicity test values using Toxcalc (Version 5.0.23, TidePool Scientific Software, San Francisco, CA, USA). Data were tested for normal distribution using Shapiro-Wilk's test (p greater than 0.01); and equal variances using Bartlett's test (p = 0.09). The inhibitory concentration which reduced population growth rate by x% (ICx) compared to controls was calculated using linear interpolation. The Dunnett's multiple comparison test was used to determine which treatments were significantly different to the control (2 tailed, p less than or equal to 0.05), and to calculate the no observable effect concentration (NOEC) and the lowest observable effect concentration (LOEC).
Data for each toxicity test are provided in individual excel spreadsheets, identified by the species tested, the test number for that species and the date the test started. A summary table of details for the 11 tests is provided in the file: Summary table.xlsx. The first worksheet for each test file is titled "Test Conditions". This sheet provides information on the toxicity test e.g. species and metals tested, dates, test conditions, as well as explanation of abbreviations, definitions of toxicity values etc. The second worksheet includes the raw cell densities determined in each flask, the calculated growth rates, and the measured pH and metal concentrations. For C. armigera data sheets, there is an additional worksheet, "Measured Cu and pH" which includes all measured pH values and metal concentrations across the 24-day period. Following the growth rate sheets are the statistical outputs for each metal, which were all generated using Toxcalc. Finally, if additional cellular parameters were measured (Chlorophyll a fluorescence, cell size and internal cell granularity), the raw data for each parameter is include in a worksheet, "Metal cellular parameters".
Data were collected in an Australian laboratory (CSIRO Land and Water, Centre for Environmental Contaminants Research, Lucas Heights, 2234, NSW) during May 2013 - April 2014. The tests used microalgal strains that had been previously collected from the Southern Ocean and are cultured within the microalgal collection at the Australian Antarctic Division (AAD). Daughter daughter cultures were transferred to CSIRO, where they were cultured for this work.
