Meeting Abstract

P1.46  Saturday, Jan. 4 15:30  Effects of low tide conditions on the photosynthetic health of the kelp Saccharina sessilis NGUYEN, T.T*; HENDERSON, S.Y; BURNAFORD, J.L; University of Washington Friday Harbor Laboratories; Cerritos College; California State University, Fullerton vynguyen313@csu.fullerton.edu

Intertidal seaweeds experience different environmental conditions during high and low tides, and stressful low-tide conditions may directly impact photosynthesis. We used laboratory manipulations to examine the effects of light and desiccation on the health of the canopy-forming low-intertidal kelp Saccharina sessilis. We predicted that high light and desiccation would cause health to decline over a single low tide. We simulated a 2 hour low-tide exposure with one no-emersion treatment (low light, no desiccation), and 4 emersion treatments: low stress (low light, low desiccation), high light (high light, ambient desiccation), high light + desiccation (high light, constant wind), and high light + hydration (high light, saltwater spray every 5 minutes). We measured photosynthetic potential as dark-adapted Maximum Quantum Yield (MQY) using pulse-amplitude-modulated (PAM) fluorometry, assessed tissue damage by quantifying the proportion of discolored blade area, and evaluated biomass loss by quantifying wet mass. We made measurements for three consecutive days following low-tide exposure to assess damage and recovery. High light severely reduced kelp health during low tide, but hydrated blades showed a strong ability to recover from this damage while desiccated blades did not recover. Blades which did not recover lost biomass: thus damage from even a single low tide exposure can have lasting consequences for the individual and the community as it affects the provision of shade for other organisms. Understanding how intertidal organisms respond to multiple simultaneous stressors is important in predicting the response of these communities to a changing climate.