Sarah Henkel
Bachelor of Science: May 2000 College of William and Mary Williamsburg, Virginia
Research Projects:
Project Director: Dr. Joe Scott
Maintenance of single-celled algal cultures and use of transmission electron microscopy.
Project Director: Dr. Emmet Duffy at the Virginia Institute of Marine Science
Grazer Diversity and Ecosystem Function in Seagrass Beds
Expected graduation date: Summer 2003
Email: wmshenk@yahoo.com
Master's
Thesis:
Morphological Variation and Reproduction in the kelp Egregia menziesii
Egregia menziesii (O. Laminariales) is an important habitat-structuring component of shallow, benthic communities throughout central and southern California. Morphological variation in this species is high, particularly in the lateral blades that distichously cover the flattened branches. Fertile sporophylls are believed to be produced throughout the year, but to be most abundant between April and November. However, spatial and temporal patterns of thallus morphology and sporophyte reproduction have not been investigated in Southern California. We studied lower intertidal populations of E. menziesii at three southern California sites separated by <16 km. Growing axes (n = 9) were collected monthly to quantify sporophyll production and the frequencies of different types of lateral blades. Band transects were surveyed quarterly to determine temporal patterns of sporophyte recruitment. Sporophylls were found throughout the year, but sporophyll densities showed a strong peak in winter (December) at all three sites. Sporophyte recruitment began in late February and peaked in June, suggesting a gametophyte period of approximately 6 months. Lateral blade morphology at the three sites varied in a consistent pattern and was related to axis length; most thalli initially developed spatulate lateral blades and then produced narrower, filiform laterals. Thalli subjected to intense grazing pressure had shorter axes and were dominated by spatulate blades, while those growing under low grazing pressure exhibited longer branches, densely covered with filiform laterals. Observed changes in the frequencies of morphologically variable lateral blades along E. menziesii axes hypothetically affect productivity, susceptibility to grazing, and thallus drag in this shallow water kelp.
Presentations of Research:
Ocean Institute Symposium (Poster): Cabrillo, CA December 2002
Western Society of Naturalists: Monterey, CA November 2002
California and World Oceans Conference: Santa Barbara, CA October 2002
Phycological Society of America – Botany 2002 Conference: Madison, WI August 2002
Southern California Academy of Sciences: Claremont, CA June 2002
Northwest Algal Symposium: Humboldt, CA May 2002
Western Society of Naturalists (Poster): Ventura, CA November 2001