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Eelgrass wasting disease (EWD) is caused by the opportunistic pathogen, Labyrinthula zostera. In eelgrass (Zostera marina), Lz creates rather characteristic lesions of empty plant tissue surrounded by black, necrotic tissue. In the Harvell Lab we were interested in the different factors that influence Lz severity and prevalence, such as temperature, dosage, and pathogen and plant lineage. We combine field methods with laboratory experiments to understand the dynamics of EWD and its potential to harm vital eelgrass ecosystems. I am continuing my work on EWD in the Coastal Trophic Ecology Lab for my dissertation, focusing on the food web consequences of the disease in eelgrass ecosystems.

EElgrass Wasting Disease, CTELab & Harvell Lab

CHARLESTON, OR &

FRIDAY HARBOR, WA

My dissertation revolves around Lz's possible changes to eelgrass food webs through EWD. Seagrasses aren't typically considered important foodstuffs in their ecosystems and, if anything, mainly as detritus. However, EWD may change this relationship. There are four major mechanisms I will investigate in this work: I) fatty acids produced by Lz infecting eelgrass, II) detrital production driven by Lz infection, III) growth, nutrition, and population changes in harpacticoid copepods feeding on Lz, and IV) changes in palatability of eelgrass tissues due to Lz infection. 

The Labyrinthulomycota, the microbial group to which Lz belongs, is known for producing high quantities of valuable fatty acids (thraustochytrids are particularly well-known for it, but labyrinthulids do it as well). These fatty acids may make eelgrass a better food when infected with Lz (I).

EWD may drive the production of this detritus through partial mortality of eelgrass blades (II). This detritus is fed on by fauna such as harpacticoid copepods, which are important links from small organic particles to larger (and tastier) organisms such as salmon (III).

Lastly, Lz infection breaks down the tough cell walls of the eelgrass plant, which serve as a structural defense against herbivory. With the eelgrass left more soft and palatable (and possibly filled with fatty acids), the eelgrass may be more appealing to herbivores such as isopods, amphipods, and snails (IV).

Understanding how this disease affects eelgrass ecosystems is incredibly important. The balance between positive and negative outcomes of EWD should determine how we address the disease and manage eelgrass ecosystems.