Predicting the effects of climate change: Effects of thermal stress on seaweed growth in the Galapagos rocky intertidal

TitlePredicting the effects of climate change: Effects of thermal stress on seaweed growth in the Galapagos rocky intertidal
Publication TypeThesis
Year of Publication2007
AuthorsHarris, Alyssa L.
Academic DepartmentBiology, College of Science
Thesis AdvisorHixon, Dr. Mark A.
DegreeBachelor of Arts in International Studies in Biology
Number of Pages49
Date Published06/2008
UniversityOregon State University
Thesis TypeUndergraduate
Keywordsbiology, Ecuador, gloabl warming, seaweed

Because global warming is predicted to increase the severity of El Niño events in the future, understanding how warmer temperature affect seaweed growth and the animals associated with seaweeds in important for predicting how marine ecosystems will change. The Galapagos Islands of Ecuador are considered a living laboratory for studying climate change and served as the experimental site for this study. An artificially induced average increase in temperature by 1.45°C significantly decreasing seaweed biomass in the intertidal of Tortuga Bay, Santa Cruz Island. The experiment utilized a block design with six treatments. Treatments consisted of 15cm x 15cm black (warm) and white (cool) plates to cause differential thermal stress, cross-factored with herbivore exclusion cages to study the effects of grazing, and a natural substratum control. Thermal stress (plate color) and grazing were both significant factors reducing seaweed biomass. Abundance, richness, and diversity of invertebrate animals living among the seaweeds showed declines in warmer treatments. Effects on small animals could reflect intolerance to thermal stress, loss of habitat (seaweed) or both, and future studies should investigate these factors. These results indicate that warmer conditions due to human induced climate change can decrease seaweed growth and affect animals that rely on seaweeds for food or habitat, possibly including the Galapagos marine iguana. Insight from the Galapagos might help predict seaweed response to climate change in other regions including the temperature Pacific Northwest.