Seagrasses are flowering marine plants that form key ecosystems in coastal areas worldwide, where they provide numerous ecosystem services. Experimentation with this keystone species presents logistical issues, as the plants require flowing seawater for cultivation, and the density of shoots plays a role in organism survival (the “bed effect”). We constructed an aboveground mesocosm setup containing over 5000L of seawater with variable flow types (flow-through and circulating) and temperature (heated, chilled, or ambient). Over 700 shoots of eelgrass (<em>Zostera marina</em>) were grown in small buckets within larger tanks. We used this setup to test how eelgrass and its microbiome responded to a combination of three stressors: exposure to antibiotics, a simulated marine heat wave, and inoculation with a pathogen. Eelgrass shoots from Yaquina Bay (OR, USA) were transplanted into sediment and subjected to zero, one, two, or all three stressors. Over two months, we collected samples in a time series to track the plant and its microbiome’s immediate and long-term response to stressors using metagenomics and transcriptomics. We also measured metamorphic and physiological responses of the plant, such as growth rate, lesion area, and community respiration. Preliminary results show that the mesocosm setup is suitable for sustained experiments of an entire eelgrass ecosystem, and allows for control of the ecosystem using a variety of manipulations.

Primary Presenter: Mary English, Department of Microbiology (englimar@oregonstate.edu)

Authors:

Mary K English, Oregon State University  (englimar@oregonstate.edu)

Luis Gonzalo Egea, Universidad de Cádiz  (gonzalo.egea@uca.es)

Rocío Jiménez-Ramos, Universidad de Cádiz  (rocio.jimenez@uca.es)

Fiona Tomas Nash, Instituto Mediterráneo de Estudios Avanzados (CSIC-UIB)  (fiona@imedea.uib-csic.es)

Ryan Mueller, Oregon State University  (muellery@oregonstate.edu)