Dataset: N:P ratio experiment physiology and carbonate chemistry laboratory experiments with Pseudo-nitzschia australis conducted from 2021 to 2022

These experiments were conducted with a strain of (strain NWFSC 731) isolated from Long Beach, Washington State, USA on November 3, 2020. The temperature and salinity were 14°C and 27 ppt, respectively at the time of collection. The data was collected in laboratory experiments at the University of Southern California.  The experiments began in September 2021 and finished in July of 2022.

The following section provides a methodology summary for this dataset and references related datasets collected as part of the same experiment (see "Related Datasets" section for data access). A full methodology was published in "Simulated upwelling and marine heatwave events promote similar growth rates but differential domoic acid toxicity in Pseudo-nitzschia australis" in Harmful Algae (Kelly et al., 2023).

Pseudo-nitzschia australis was grown under upwelling heatwave, and extreme heatwave conditions (e.g., combined temperature, nutrient, and carbon dioxide levels specific to each condition) and in single-factor response curves for carbon dioxide, temperature, and varying nitrogen:phosphorus (N:P) ratios/total nutrient concentrations.

Samples for chlorophyll a (used to calculate growth rates) were filtered on GF/F filters, extracted in 6 mL of 90 % acetone at -20°C for 24 h, then analyzed using a Turner 10AU field fluorometer (Welschmeyer 1994; Fu et al. 2007).

For elemental analysis (particulate organic carbon and nitrogen, POC and PON), cells were filtered onto pre-combusted GF/F filters, dried, and analyzed on a Costech 4010 Elemental Analyzer (Fu et al. 2007). 

Samples for particulate domoic acid were filtered onto Supor 0.2 µm 47 mm PES filters. Samples were analyzed using LC-MS/MS on a Prominence UFLC system (Shimadzu, Kyoto, Japan) coupled to a SCIEX 4500 QTRAP mass spectrometer (AB Sciex, Framingham, MA, USA). Methods described in Wang et al. 2012.

Primary production was determined by measuring the uptake of radiolabeled bicar­bonate (Fu et al. 2008). 14C-bicarbonate was added to 45 mL sub-cultures at T24 h and incubated for 24 h (approximating net carbon fixation) under the respective experimental conditions. After the incubation period, cells were collected on GF/F filters and placed in a scintillation vial containing scintillation cocktail. Samples were stored for 24 h before being read on a Wallac System 1400 liquid scintillation counter.

pH measurements were made on a Mettler Toledo SevenCompact pH meter using a three-point calibration curve and total pH scale (Cooley and Yager 2006). Samples for total DIC analysis were collected at Tfinal. Seawater from undisturbed culture bottles was removed with a sterile syringe, ejected into pre-evacuated borosilicate Exetainers, and poisoned with 5% MgCl2. Total DIC was then measured using a Picarro cavity ring-down spectrophotometer according to Subhas et al. (2015).

For cell count samples (for normalizing cellular domoic acid), 1 mL of the final experimental culture was preserved with 40 ul glutaraldehyde and stored at 4°C in the dark. Cells were counted on a Olympus BX51 microscope using a Sedgewick Rafter Chamber.

Organism:
Pseudo-nitzschia australis, LSID (urn:lsid:marinespecies.org:taxname:246604)