Data from: Microcystins bioaccumulate but do not biomagnify in an experimental aquatic food chain
Data files
Dec 03, 2024 version files 17.44 KB
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Bioaccumulation_29Oct24.R
11 KB
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Data_2Dec24.csv
3.88 KB
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README.md
2.56 KB
Abstract
Microcystins-common hepatotoxins produced by cyanobacteria—have been detected in a wide range of organisms, though research examining the trophic transfer of microcystins and whether microcystins bioaccumulate or biomagnify in food webs has generated contradictory results. Here, we explored the trophic transfer of microcystins from the herbivorous water flea, Daphnia pulex, to the predatory larvae of a damselfly, Enallagma sp. We tested the hypotheses that microcystins transfer from the tissue of herbivorus zooplankton to that of predatory invertebrates and that these toxins biomagnify across trophic levels. We also assessed the relative contribution of toxin transfer from the gut and tissue of Daphnia pulex to Enallagma sp. We found that microcystins are effectively sequestered in the tissue of Daphnia pulex, and that these sequestered toxins are then transferred to the tissue of Enallagma sp. The contribution of gut contents to toxin transfer was negligible. Contrary to the pattern predicted by biomagnification, we found that the concentration of microcystins decreased with increasing trophic levels. Our results support the hypothesis that microcystins can be transferred trophically, but do not support the hypothesis that microcystins biomagnify from lower to higher trophic levels. Conversly, we observe biodilution in this system. These results have consequences for the impact of microcystins across trophic levels in a changing world with increasing intensity and duration of harmful algal blooms.
README: Data from: Microcystins bioaccumulate but do not biomagnify in an experimental aquatic food chain
https://doi.org/10.5061/dryad.280gb5n0n
Description of the data and file structure
This dataset includes measurements of microcystin in three trophic levels in an experimental aquatic food web including Microcystis, Daphnia, and Enallagma. The data were used to test for biomagnification, toxin transfer route, and trophic transfer efficiency across trophic levels. Data were collected as described in associated manuscript. Microcystins were measured using the MMPB technique. Final concentration of microcystin per dry weight (mg) for each sample is reported.
Files and variables
File: Data_29Oct24.csv
Description:
Variables
- Algae: One of two values:* Microcystis* (toxic algae) or* Scenedesmus* (non-toxic algae)
- Daphnia gut: Describes whether gut of *Daphnia *was full (including algae) or clear
- Enallagma gut: Describes whether gut of *Enallagma *was full (including algae) or clear
- Treatment: Treatment code incorporating information from three columns: Algae, Daphnia gut, and Enallagma gut. These treatment codes were used in the analysis in attached R script.
- Rep: Trial number (2, 3, 4, or 5)
- Density_cells/mL: Density of algae in cells/ml in trial
- ng MC/Daph: Amount of microcystin (in ng) per Daphnia individual
- No.Daphnia Eaten: Number of Daphnia consumed by* Enallagma* in corresponding trial
- MCEnall_ng/Enall: Amount of microcystis per* Enallagma* indicidual
- ngMC/mgTL: Concentration of microcystin (in ng) per dry weight (in mg)
- Trophic Level: One of three values indicating trophic level upon which measurements were made: 1 (algae), 2 (Daphnia), or 3 (Enallagma)
Further notes:
- 'NA' values indicate that a measurement was not made. For example, if the treatment was 'Microcystis', measurements were only made on Microcystis and not Daphnia. For that reason, 'ng MC/Daph' would have an 'NA' value.
- 'BDL' indicates 'below detection limit', which was 0.2 ng/mL
File: Bioaccumulation_29Oct24.R
Description: This R script includes all steps for reproducing figures and statistical tests using the associated dataset.
Code/software
Analysis was completed using attached R script.
Versions of R and loaded packages:
- R version 4.2.2
- rstatix_0.7.2
- cowplot_1.1.1
- ggplot2_3.5.1
- tidyverse_2.0.0
- forcats_1.0.0
Access information
No other publicly accessible locations of the data.
Methods
This dataset includes measurements of microcystin in three trophic levels in an experimental aquatic foodweb. Data were collected as described in associated manuscript. Microcystins were measured using the MMPB technique. Final concentration of microcystin per dry weight (mg) for each sample is reported in column labeled ngMC/mgTL. As described in the associated manuscript, in one of the five trials, microcystins were detected in Microcystis but not in the grazing Daphnia. Data from this trial have been omitted from the dataset, as they were not used in the reported analysis.
This R script includes all steps for reproducing figures and statistical tests using the associated dataset.