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4. AAS_4326_Toxicity_Metals_Metal-Mixtures_Rotifer

Description

This dataset contains results of toxicity testing with the Antarctic limno-terrestrial bdelloid rotifer Adineta editae. This study assessed the toxicity of copper, zinc, cadmium, lead and nickel, singly and in metal mixtures, to Adineta editae in aqueous exposures. Toxicity tests were done at Casey in the austral summer of 2017/18 using rotifers collected from the field and isolated in the laboratory.

Rotifer collection
Rotifers were sourced from Prassiola crispa algal mat collected from ephemeral melt-streams on Shirley Island in the Windmill Islands, East Antarctica Adineta editae were isolated into a single species aqueous culture prior to use in toxicity tests. Culture maintenance and toxicity testing was within temperature-controlled cabinet set at 5°C with 18/6 h light dark cycle.
Rotifer species identification was confirmed by DNA sequencing (BOLD sequence OZBOL4598-21) with a 99.52% match to haplotype Bd8_02.

Toxicity tests
Toxicity testing with A. editae rotifers was done in the Casey station laboratory during January and February of 2018. Exposures were with single metals cadmium, copper, nickel, lead, and zinc, and in metal mixtures of the five metals at two ratios, an Environmental mixture (EvM, Mixture 1) and Equitoxic mixture (EqM, Mixture 2) in aqueous exposures. Each mixture had a different fixed ratio of the five metals, which was multiplied by different factors to produce a concentration series.

Exposures were with single metals cadmium, copper, nickel, lead, and zinc, and in metal mixtures of the five metals at two ratios, an Environmental mixture (EvM, Mixture 1) and Equitoxic mixture (EqM, Mixture 2) in aqueous exposures. Each mixture had a different fixed ratio of the five metals, which was multiplied by different factors to produce a concentration series.
For EvM Mixture 1, the ratio was broadly based on metal concentrations reported in Brown Bay, a marine site adjacent to a legacy waste site near Casey station in East Antarctica. The metal ratio was 1 Cu: 0.1 Cd: 0.3 Ni: 0.3 Pb: 4.5 Zn, and this mixture was tested at multiples from 5 to 70 times. Mixture 2 was closer to an equimolar ratio, with lower concentrations of lead. This metal ratio was 1.1 Cu: 0.7 Cd: 0.8 Ni: 0.3 Pb: 1.0 Zn, and this mixture was tested at multiples from 0.2 to 2 times. Measured concentrations of each metal in each treatment were used in mixture toxicity modelling to give predicted toxicities, which are compared with observed toxicity using toxic units.

Metal stock solutions were prepared using analytical grade reagents in ultrapure water acidified to 0.2% with HCl (Suprapur, MilliporeSigma).

Exposures were in plastic microwell plates with 5 metal treatments plus controls, 3 replicate wells per treatment and 8 rotifers in each replicate. To add rotifers to test wells, collection dishes were viewed under the microscope and small, non-ovigerous individuals were selected. Using a micropipette, each organism was transferred from the collection dishes in an 8 µL aliquot of the culture water, with eight organisms added to each well, representing a single replicate. Following transfer of the organisms to a well, 236 µL of test solution was added, giving a final volume of 300 µL. Rotifers were not fed, although there was some suspended algal detritus carried over in the transfer water that provided a limited quantity of food during the test. Well plates were sealed with Parafilm and placed in trays in cabinets at 5°C with 18/6 h light dark cycle.

Rotifers were observed under a stereomicroscope at day 4 and day 7 of the test and assessed with survival and behavioural endpoints. Survival (Alive/Dead) was defined by body morphology and mobility. Dead rotifers had a distinct relaxed and flattened body morphology with no muscular contraction or movement evident. The individuals scored as Alive were also scored with a sub-lethal endpoint based on their movement behaviour (Active/Inactive). Active individuals showed normal movement behaviours (creeping, feeding) and Inactive individuals had their bodies fully contracted to form a tun, with no external body movement.

Chemical analysis
To measure the metal exposure concentrations in test treatments, two sets of sacrificial well plates containing a total of 6 mL of each exposure solution were prepared at the beginning of each toxicity test. These well plates were identical to well plates used for toxicity testing, but did not contain rotifers. One sacrificial well plate was sampled by syringe at the beginning (day 0) and end (day 7) of each toxicity test into clean polypropylene tubes. Subsamples were acidified to 0.2% HNO3 (Suprapur, MilliporeSigma) and stored at 4 °C until analysis by inductively coupled plasma-atomic emission spectrophotometry (ICP-AES; Varian 730-ES). The measured dissolved concentrations (µg/L) of each metal in tests was calculated as the geometric mean of initial and final concentrations for each treatment.

Statistical analyses
Single metal response data from day 4 and day 7 counts were modelled to estimate the effect concentrations (EC) and lethal concentrations (LC) for 10 and 50 percent response relative to controls (EC10 and EC50, LC10 and LC50) for each metal.
Response data and measured metal concentrations from toxicity tests are shown in spreadsheet
'Rotifer_toxicity test responses and metal conc.xlsx'

The R code used to model dose response and estimate the effect concentrations (EC) and lethal concentrations (LC) for 10 and 50 percent response relative to controls (EC10 and EC50, LC10 and LC50) are shown in file
'2023_Rotifer dose response modelling.R'
This R file also contains the code used to model mixture toxicity to give predicted toxicities, which are compared with observed toxicity using toxic units.
The dose response data file used as input to the R analysis is shown in file '2023 Antarctic Rotifer.csv'

The results of this study are described in the manuscript 'High sensitivity to metals of the Antarctic rotifer Adineta editae and their ecological relevance in contaminated site risk assessments'

Quality

No problems were encountered with data collection or analysis.

Access

These data are publicly available from the provided URL.

Temporal Coverages

• Start date: 2017-12-17 - Stop date: 2018-02-19

Spatial Coverages

Science Keywords

• EARTH SCIENCE > BIOSPHERE > ECOLOGICAL DYNAMICS > ECOTOXICOLOGY > TOXICITY LEVELS
• EARTH SCIENCE > HUMAN DIMENSIONS > ENVIRONMENTAL IMPACTS > HEAVY METALS CONCENTRATION
• EARTH SCIENCE > HUMAN DIMENSIONS > ENVIRONMENTAL IMPACTS > CONTAMINANT LEVELS/SPILLS
• EARTH SCIENCE > BIOLOGICAL CLASSIFICATION > ANIMALS/INVERTEBRATES > ROTIFERS

Use Constraints

This data set conforms to the CCBY Attribution License (http://creativecommons.org/licenses/by/4.0/).

Please follow instructions listed in the citation reference provided at http://data.aad.gov.au/aadc/metadata/citation.cfm?entry_id=AAS_4326_Toxicity_Metals_Metal-Mixtures_Rotifer when using these data.