Date of Award


Document Type

Campus Access Dissertation


Biological Sciences

First Advisor

Brian Helmuth


Marine intertidal organisms live in a habitat that is characterized by acute environmental gradients determined by tides, waves, and weather. Models that incorporate these parameters can be used to predict and understand the distributions of organisms on both local and latitudinal scales. Intertidal organisms oscillate between marine and terrestrial conditions, a phenomenon controlled by the timing and duration of the tide, so it is essential to understand the environment from both marine and terrestrial perspectives.

Oceanic influx characteristics: The marine component of the tidal cycle was quantified by deploying loggers in the intertidal that measure, in situ, the timing and duration of splash, surge, and submergence. It was also possible to calculate the return times to the marine conditions from these data. Results indicate that oceanic influx may influence intertidal community composition.

Patterns of risk in intertidal ecosystems: During terrestrial exposures, intertidal organisms are at risk for temperature stress. A model that combines tidal predictions and solar elevations was developed to determine risk of high temperature events when intertidal organisms are exposed to terrestrial conditions during low tide. Results showed that the timing of the tides in the northeast Pacific protects intertidal ecosystems from high temperatures.

Modeling mussel temperature using gridded weather data: Gridded weather data and local observational data were inputed into biophysical models of mussel body temperature and compared. Regional scale gridded data produced mussel temperatures most similar to local observational data and global scale gridded data produced promising results. The use of gridded weather data in biophysical models will greatly enhance the ability of ecologists to make continental-scale predictions of organism distributions.

Hindcasting Mytilus californianus survival: M. californianus mussels were surveyed at sites distributed along 1500 km of coastline in the northeast Pacific and survival during heat waves was measured in laboratory studies. I found that mussel mortality greatly increased when body temperatures reached 38°C for exposures greater than 30 minutes. An analysis of 10+ years of mussel temperatures from a biophysical model revealed occasional temperature-based M. californianus mortality.


© 2010, Katherine Allison Smith