DIATOM POPULATION HEALTH UNDER PARASITIC INFECTION AND TEMPERATURE STRESS

Parasitic protists can spread rapidly during diatom blooms, impacting bloom dynamics and redirecting carbon flow through the marine food web. Our understanding of how these interactions vary across climates and in warming ecosystems is lacking. Specifically, the physiological response of diatoms to protist infection has not been adequately studied. Here, we investigated how a novel protistan parasite impacts pennate diatom transcription and growth under two thermal conditions. We coisolated a putative Oomycete parasite from the Scotian Shelf in October 2023 and infected a pennate diatom, Asterionella. Parasitism and temperature impacts on diatoms were assessed by growing infected and uninfected cultures at 15°C and 22°C. Infection was not evident during host exponential growth but proliferated in late exponential phase. Infection did not cause drastic host population decline yet persisted throughout the experiment. Micrographs revealed an increase in infected host cells as growth approached stationary phase, altering the morphology and behavior of individual cells. We expect a difference in host transcriptional profile between infection conditions, with downregulation of carbon fixation pathways in infected cultures. These data point to the important role of undescribed parasites as top-down controls on diatom populations, and their potential to impact bloom dynamics and marine carbon flow. This work illuminates important characteristics of a novel host-parasite system, with likely implications for diatom community responses to future climate change scenarios.

Presentation Preference: Oral

Primary Presenter: Katelyn Hickman, Woods Hole Oceanographic Institution, Massachusetts Institute of Technology (jhickman@mit.edu)

Authors:

KJE Hickman, MIT-WHOI Joint Program in Oceanography/Applied Ocean Science and Engineering  (jhickman@mit.edu)

Abigail McGarrigle, University of Massachusetts Dartmouth  (abigail.mcgarrigle@whoi.edu)

Sara Shapiro, Woods Hole Oceanographic Institution  (sara.shapiro@whoi.edu)

Arianna Krinos, MIT-WHOI Joint Program in Oceanography/Applied Ocean Science and Engineering  (akrinos@whoi.edu)

Christine Palermo, Woods Hole Oceanographic Institution  (christine.palermo@whoi.edu)

Harriet Alexander, Woods Hole Oceanographic Institution  (halexander@whoi.edu)