Merging in-situ and Discrete Sampling with Bioinformatics to Determine Cross-Reactivity of Pseudo-nitzschia spp. probes during Environmental Sample Processor Deployments in the Gulf of Maine

Harmful Algal Blooms (HABs) occur when phytoplankton produce toxins that can negatively impact human and animal health. The diatom Pseudo-nitzschia produces the neurotoxin domoic acid (DA), which can lead to Amnesic Shellfish Poisoning (ASP) in humans through consumption of contaminated shellfish. There are 52 documented Pseudo-nitzschia spp. globally; half produce DA. Certain HAB species including Pseudo-nitzschia spp. can be analyzed by Environmental Sample Processors (ESPs), in-situ genomic sensors that utilize specific probes to identify and quantify HAB species. Four ESPs were deployed in the Gulf of Maine in 2017 with an array of nine probes targeting variable regions on the large subunit of the ribosomal RNA (LSU rRNA), designed and validated for Pseudo-nitzschia spp. on the US West Coast (WC). At least fifteen species of Pseudo-nitzschia have been documented in the Gulf of Maine (GOM), including similar and unique species relative to the WC. We conducted an in silico study using the LSU rRNA to predict the hybridization of GOM Pseudo-nitzschia spp. with these probes by evaluating similarity across full and trimmed probe sequences. During the 2017 ESP time series, all probes were observed to hybridize, yet spatiotemporal variability was evident. Observations of species discrete samples collected near the ESPs as part of validation surveys and nearshore time series in the GOM were helpful for synthesizing computational and in situ findings. While our synthesis mirrors prior studies that show the variability in specificity across the probes used on the arrays, these data also indicate that Pseudo-nitzschia species composition is dynamic in the GOM and provide new insight into the utility of the ESP for detecting HABs there.