In the 1930s, eelgrass (Zostera marina) beds were destroyed on the Atlantic coast of the US by eelgrass wasting disease. Eelgrass wasting disease is caused by a marine opportunist called Labyrinthula zosterae. While in recent history the outbreaks have remained localized, it is still not known what environmental factors create a suitable environment for an outbreak. Laby is thought to be an opportunist, acting as a decomposer, but given an opportunity, such as suitable environment or compromised host, it may become infectious.
This summer, I focused on the effects of herbivory on eelgrass susceptibility to Labyrinthula zosterae. Herbivory could affect eelgrass susceptibility to L. zosterae because herbivory induced phenolic acids, secondary compounds which are thought to help the plant resist herbivory and pathogens. Therefore, I hypothesized that eelgrass that had been affected by herbivory would be more resistant to Laby because the herbivores had induced phenolic acids. Eelgrass that had sustained long-term damage by invertebrate grazers for five weeks, eelgrass that was only exposed to short-term damage by mechanical damage one day before infection and a unmanipulated treatment of eelgrass were all exposed to two strains of Labyrinthula zosterae in laboratory culture. Although almost none of the plants showed signs of infection after 9 days, the plants began to decompose at different rates.
Using image analysis, I found that the decay rates of the short-term damaged eelgrass were significantly higher (p=0.0063) than the control or long-term damaged eelgrass, regardless of L. zostera inoculation. One possible explanation for this is that the environment had not been suitable for infection. Laby is only infectious if the conditions are right, otherwise it works as a decomposer.
Looking at the data, I wanted to examine decomposition rates more closely so I designed a new experiment. Three treatments of long-term damaged eelgrass (herbivory), short-term damaged eelgrass (mechanical scratching), long-term damaged and short-term damaged eelgrass, and a control (unmanipulated) are currently being monitored for decay rates. These samples will also be analyzed for phenolic acids compounds to look at plant resistance over time. These results will help to determine the effect of herbivory on resistance of eelgrass to opportunistic decomposing microbes.
I learned a lot this summer. Not just about eelgrasss, but science in general. I feel like I am better equipped for college and my future career. This experience taught me what to do in the face of failure and how to be persistent. Although things did not always go as planned, you always learn more from mistakes than when you do it right. I gained a lot from my time here this summer. Thank you COSEE, SPMC, and Dr. Sylvia Yang, my awesome mentor, for giving me this experience!