Dataset: Counts of dead mussels, shell lengths of dead mussels, toxin data from LCMS, and histological results from mussel tissue from rocky intertidal sites on the Oregon coast in 2023 and 2024

Collection and analysis of "live" (unprocessed) water samples and separate preserved water samples for assessment of potential toxin-producing phytoplankton was done monthly. Samples were processed by Dr. Eli Meyer of Aquabiomics Inc. (Junction City, OR), by Dr. Ralph Elston of Aquatechnics (Carlsborg, WA), by Dr. Maria Kavanaugh of OSU's College of Earth, Ocean, and Atmospheric Sciences (Seascape Ecology Lab), and Dr. Manuel Garcia-Jaramillo in the Department of Environmental and Molecular Toxicology at OSU.

Mussel counts: All dead mussels within specific mussel beds were located and counted on each sampling date at each site. When mussel length was measured, it was total shell length in centimeters.

Mussel disturbance: Disturbed patches are obvious as gaps in the mussel bed showing bare rock and byssal threads left behind by the mussels torn loose by wave action. Disturbances were simply counted in each of the specific mussel beds listed.

Histology: To gain insight into mussel condition, in July 2023, twenty mussels from Fogarty Creek, ranging in shell length from 50 to 130 millimeters (mm) were examined histologically. We followed these with samples of five mussels each from five sites (FC, BB, YB, SH, and TK) in August, September, and October 2023 and June 2024. Mussels were dissected from their shells, preserved in formalin, and shipped to AquaTechnics Inc., in Sequim, Washington for processing. Sections were inspected for evidence of abnormal conditions of the digestive tubules and kidneys.

For LC-MS sampling, mussel tissue samples for the determination of toxin content using Liquid Chromatography-Mass Spectrometry (LC-MS) (King et al. 2021) (available in OSU's Mass Spectrometry center) were collected from September to December 2023. Sample size was 3 field sites (one per cape) x 3 mussels x 4 seasons = 36 mussels. Liquid chromatography was performed using an Acquity UPLC BEH C18 column (1.7 µm, 2.1 × 50 mm). Mobile phase A consisted of 6.7 mM ammonium hydroxide in water, and mobile phase B consisted of 6.7 mM ammonium hydroxide in acetonitrile. A 6-minute gradient method was used with the following conditions: 0–0.5 min, 70% A / 30% B; 3.5 min, 10% A / 90% B; and 4.1–6.0 min, 70% A / 30% B. The flow rate was 0.500 mL/min, the column temperature was maintained at 40 °C, and the injection volume was 3 µL. The retention time was 5.072 minutes.

Mass spectrometry was performed in negative ionization mode with a mass range of 50–1160 Da. Ion source gas pressures were set to 45 and 40 psi, the curtain gas pressure was 35 psi, the source temperature was 500 °C, the declustering potential was −80 V, the collision energy was −10 V, and the scan time was 0.518 s. An inclusion list containing yessotoxin (m/z = 1141.4700 Da) and 45-hydroxy-yessotoxin (m/z = 1157.4700 Da) was used. Instrument output consists of the intensity of the analyte m/z at its corresponding retention time. Extracted ion chromatograms (XICs) were generated by filtering the data by the target m/z values. Peaks in the XICs were integrated to obtain peak area, which was used to calculate analyte concentration based on the calibration curve.

A calibration curve was generated using standards at 10, 25, 50, 75, and 100 ppb. The limit of detection (LOD) and limit of quantification (LOQ) were determined using replicate injections of the 10 ppb standard. Using this method, all mussel sample extracts contained toxin concentrations below the LOD. Mussel tissue concentrations of yessotoxin were below 0.15 µg YTX/g mussel.

Histology and toxicology data are not spreadsheets but rather reports (see Supplemental Files). Relevant information is included in each report.