SEMINAR: OI Seminar Series - Ylva Olsen

Title: Will climate change alter susceptibility of Mediterranean seagrasses Posidonia oceanica and Cymodocea nodosa to infection by Labyrinthula?

Abstract: Vulnerability of seagrasses to pathogens may be greater under certain environmental conditions and infections may become detrimental to seagrasses under stress. We examined the effect of temperature and acidification on infection by the protist Labyrinthula in Mediterranean seagrasses. In a first experiment, Posidonia oceanica and Cymodocea nodosa shoots were inoculated with Labyrinthula sp. in mesocosms under different temperatures (24, 26, 28, 30 and 32 °C). We used lesion area as a measure of degree of infection and examined the photosynthetic response of the plant using a PAM fluorometer. Lesions in P. oceanica were generally small compared to those in C. nodosa, but lesion area decreased with increasing temperature in both species. Temperature did not significantly affect photosynthetic performance in P. oceanica. The response of quantum yield to temperature in C. nodosa was bell-shaped, suggesting optimum performance at 30 °C, and was significantly reduced in Labyrinthula-infected shoots. In a second experiment we tested the effect of temperature and CO2 on Labyrinthula infection by exposing P. oceanica to two temperatures (24 and 30 °C) and two CO2 concentrations (360 and 1000 ppm). CO2 did not increase lesion area or alter photosynthetic performance of the plants. These results suggest that Labyrinthula infection in Mediterranean seagrasses is unlikely to increase in Mediterranean seagrasses under future scenarios of climate change.

Biography: Ylva Olsen is originally from Sweden, but moved to Plymouth in the UK to study for a BSc in Ocean Sciences with Marine Biology and a MSc in Applied Marine Science. She gained her PhD from the Boston University Marine Program in Woods Hole where she studied top-down and bottom-up controls on seagrasses and benthic food webs in temperate (Waquoit Bay, MA) and tropical (Puerto Rico) environments. Her first postdoctoral position was at Bangor University in Wales working as a research lecturer investigating the effects of cattle grazing on nutrient cycling in salt marshes. She currently holds a Marie Curie fellowhip at IMEDEA, Mallorca where she studies how climate change affects seagrass-pathogen interactions in the Mediterranean using Labyrinthula as a model organism.