Harmful Algae

Here is the raw data for the manuscript "Effects of ocean acidification and phosphate limitation on physiology and toxicity of dinoflagellate Karenia mikimotoi"

Being complement of our previous article recently published in Harmful algae (Wang et al., 2019, https://doi.org/10.1016/j.hal.2018.11.013), these data reveal the response of the toxic dinoflagellate K. mikimotoi to solar ultraviolet radiation (UVR) by transcriptome sequencing at molecular level.

All data comes from the experimental process

Growth rate data for the toxic dinoflagellate Alexandrium catenella and co-occurring dinoflagellate species Scrippsiella and Amphidinium carterae from the Gulf of Maine at 15°C and 20°C and pH 8.1 and 7.8.

The HAB-forming, toxic dinoflagellate Karenia mikimotoi, previously found to benefit from ocean acidification (OA), was cultivated to investigate its transcriptional response to simulated OA for 30 generations. Batch cultures were grown under two CO2 concentrations, 450 (control) and 1100 (simulated OA) μatm, and physiological parameters [growth, pigments, catalase (CAT), glutathione reductase (GR), and superoxide dismutase (SOD) activity], as well as transcriptomes (obtained via RNA-seq), were compared. Chlorophyll a (Chl a) and carotenoid (Caro) contents, as well as CAT and GR activities, were significantly increased under OA conditions. Transcriptomic analysis revealed 2,490 differentially expressed unigenes in response to OA, which comprised 1.54% of all unigenes. A total of 1,121 unigenes were upregulated, and 1,369 unigenes were downregulated in OA compared to control conditions. The downregulated expression of bicarbonate transporter and carbonic anhydrase genes was a landmark of OA acclimation. Key genes involved in energy metabolism, e.g., photosynthesis, tricarboxylic acid cycle, oxidative phosphorylation, and nitrogen metabolism, were highly upregulated under OA, contributing to increases in the Chl a (55.05%) and Caro (28.37%). The enhanced antioxidant enzyme activities (i.e. CAT, GR) and upregulated genes (i.e. glutathione peroxidase, ascorbate peroxidase, heat shock protein, 20S proteasome, aldehyde dehydrogenase, and apolipoprotein) benefit cells against the potential lower pH stress condition under OA. In addition, the downregulation of four genes associated with motility suggested that the preserved energy could further boost growth. In conclusion, the present study suggests that K. mikimotoi exhibits efficient gene expression regulation for the utilization of energy and resistance to OA-induced stress. Taken together, K. mikimotoi appeared as a tolerant species in response to OA. Thus, more extensive algal blooms that threaten marine organisms are likely in the future. These findings expand current knowledge on the gene expression of HAB-forming species in response to future OA.

The phycotoxin contents were measured in 2013 during a long-term mesocosm CO2 experiment in Gullmar Fjord (Sweden). The natural plankton community was enclosed in ten pelagic mesocosms and five of the mesocosms were enriched with CO2 to simulate end-of the century ocean acidification while the others served as controls. The data set was used to assess the impact of ocean acidification on harmful algal bloom species and toxins. The Fjord-sample data were taken in close proximity of the mesocosms and were used to assess the phycotoxin contents in the surrounding waters.

Concentrations of toxins in fish viscera

Data from NLA 2012 was used to assess biovolume results for cyanobacteria (phytoplankton) in relation to both landscape and in lake factors.

Matched chlorophyll a and microcystin measurements from Iowa reservoirs. National Lakes Assessment data available at the provided link.

This work demonstrated a 10-day batch culture experiment to test the physiology and toxicity of harmful dinoflagellate Karenia mikimotoi in response to ocean acidification (OA) under two different phosphate concentrations. Cells were previously acclimated in OA (pH = 7.8 and CO2 = 1100 μatm) condition for about three months before testing the responses of K. mikimotoi cells to a two-factorial combinations experimentation. This work measured the variation in physiological parameters (growth, rETR) and toxicity (hemolytic activity and its toxicity to zebrafish embryos) in four treatments, representing two factorial combinations of CO2 (450 and 1100 μatm) and phosphate concentration (37.75 and 4.67 umol l−1). Results: OA stimulated the faster growth, and the highest rETRmax in high phosphate (HP) treatment, low phosphate (LP) and a combination of high CO2 and low phosphate (HC*LP) inhibited the growth and Ek in comparison to low CO2*high phosphate (LCHP) treatment. The embryotoxicity of K. mikimotoi cells enhanced in all high CO2 (HC) conditions irrespective of phosphate concentration, but the EC50 of hemolytic activity increased in all high CO2 (HC) and low phosphate (LP) treatments in comparison of LCHP. Ocean acidification (high CO2 and lower pH) was probably the main factor that affected the rETRmax, hemolytic activity and embryotoxicity, but low phosphate was the main factor that affected the growth, α, and Ek. There were significant interactive effects of OA and low phosphate (LP) on growth, rETRmax, and hemolytic activity, but there were no significant effects on α, Ek, and embryotoxicity. If these results are extrapolated to the aquatic environment, it can be hypothesized that the K. mikimotoi cells were impacted significantly by future changing ocean (e.g., ocean acidification and nutrient stoichiometry).