Heat Stress and Behavioral Responses in Phyllaplysia taylori

Abstract

Marine heatwaves have caused thermal stress on many aquatic organisms of the Pacific Northwest. In 2013, the infamous “Blob” increased water temperatures by 2 to 4°C, resulting in mass die offs of marine mammals, fish, intertidal invertebrates, as well as many others (Cavole 2016). This also lead to the increase of algal blooms, which reduced productivity, especially for eelgrass Zostera marina (Bond, 2015). Z. marina, apart from being a nursery to many marine mammals, as well as a carbon sequestration tool, is home to sea hare Phyllaplysia taylori. This heterobranch is an intertidal species with a range from the NE Pacific all the way to Baja, California (Tanner, 2018). It feeds on the epiphytes residing on Z. marina, usually diatoms and various forms of algae. This interaction results in a mutually beneficial relationship between these organisms, as P. taylori essentially “cleans” the epiphytes off the eelgrass, resulting in increased productivity due to a decrease in shading on the blades (Tanner, 2018). They are also poikilotherms, meaning their body temperature is determined by the external environment and fluctuates with it. Little is known about how P. taylori specifically, responds to changes in temperature. Most studies have focused on feeding or grazing behavior over long periods of time, or the more popular Aplyssidae sea hare, A. californica. Righting time however, can be helpful for understanding short-term thermal stress, as it is a behavioral response that can integrate neuromuscular and metabolic changes.