Date of Award

Fall 2012

Project Type


Program or Major


Degree Name

Master of Science

First Advisor

Larry G Harris


The ecology of the sacoglossan Alderia modesta and its ability to retain active chloroplasts from the yellow-green alga Vaucheria spp. was examined with field and laboratory studies. Field surveys found no A. modesta, because Vaucheria spp. was absent or sparse in surveyed marshes. A grass removal experiment tested whether interspecific competition was causing the algal absence. The alga appeared in some plots, but did not promote A. modesta settlement. Absence of Vaucheria spp. is likely due to factors other than competition. Lack of animals prevented laboratory studies.

Placida dendritica and its food Codium fragile ssp. fragile were then chosen for ecology and photosynthesis studies. Field surveys indicated year-round presence, greatest abundance in summer, and preferential larval settlement on larger C. fragile thalli. Photosynthetic potential was evaluated through oxygen consumption, growth, and phototaxis experiments. Oxygen consumption and growth showed inactive chloroplasts from C. fragile, but behavior indicated the possibility for active chloroplasts from other algal species.