JOHNSON, C.H.*; WENDT, D.E.; California Polytechnic State University; California Polytechnic State University: Assessing the energetic and ecological benefits of dissolved organic matter (DOM) for the marine bryozoan Bugula neritina

It is well known that dissolved organic matter (DOM), in the form of carbohydrates, lipids, and free amino acids, is an abundant energy source utilized by marine microorganisms for growth and reproduction. In contrast, there is much debate about the utilization of DOM by metazoan animals. Numerous studies have demonstrated that a variety of marine invertebrates are able to take up DOM. However, there is limited direct evidence demonstrating the energetic and ecological benefits of DOM transport for metazoans. The purpose of this study is to quantify the energetic and ecological benefits of DOM use by larvae of Bugula neritina. A critical initial step in conducting these experiments is obtaining �DOM-free� seawater. This was accomplished through constant exposure to UV light (1200 Watts, for 18 hours, at 222-366 nm), and verified by total organic carbon (TOC) analysis. The concentration of TOC was reduced from 290 &microM to 1 &microM, a value equal to blank controls and less than 1% of ambient DOM concentrations. It was also determined that treated water did not affect metabolic activity. Respiration rates for larvae (of Artemia sp.) were not significantly different in treated and untreated water (417 and 454 pmol O₂ ind^-1 hr^-1, respectively)(N=11 trials; p=.636) and there were no significant behavioral differences observed. Experiments are currently underway to determine performance differences (e.g., ability to prolong larval swimming duration, maintain metamorphic competence, postmetamorphic fitness) between larvae in the presence and absence of DOM.