JOHNSON, C.H.; WENDT, D.E.; Cal Poly, San Luis Obispo; Cal Poly, San Luis Obispo: Does dissolved organic matter (DOM) offset the costs of an extended larval swimming phase 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. We previously reported that constant exposure of SW to UV irradiation was an effective means of reducing total organic carbon, and that this irradiation did not adversely affect larvae of the brine shrimp, Artemia sp. This bioassay was extended to include larvae of 3 additional species. It was found that larval respiration rates did not differ significantly in treated and untreated SW for the purple sea urchin, Strongylocentrotus purpuratus, the red abalone, Haliotis rufescens and the marine bryozoan, Bugula neritina. Experiments were then conducted with Bugula neritina to determine performance differences between larvae in the presence and absence of DOM. It is known that extending the larval swimming phase for larvae of B. neritina results in reduced rates of settlement and metamorphosis, smaller postmetamorphic size, slower adult growth, and a delayed onset of reproduction. Our study focused on whether access to DOM offset the deleterious affects associated with a prolonged larval swimming phase. In particular, we will report on whether the presence of DOM can offset the decrease in lophophore size that results from an increased larval swimming phase.