Meeting Abstract

P2.129  Jan. 5  Biofilms affect the behavior of polychaete larvae landing on surfaces in water currents and waves SISCHO, D.*; KOEHL, M.; HATA, T.; COOPER, T.; HADFIELD, M.; CSU, Fresno; UC Berkeley; UC Berkeley; UC Berkeley; UH dsischo@csufresno.edu

Many benthic marine animals release planktonic larvae that are dispersed by ocean currents. After becoming competent� to undergo metamorphosis, larvae can settle into benthic habitats. Organisms on the bottom can affect where larvae settle via chemical cues and alterations of ambient water flow. We studied the effects of benthic organisms on the initial touchdown behavior of competent larvae of the tubeworm Hydroides elegans, an abundant member of warm-water fouling communities. We videotaped behavior of larvae of H. elegans near substrata in a laboratory flume in which we produced water currents and waves (wind chop) similar to those recorded across fouling communities in Pearl Harbor, HI. Substrata tested represented early stages in fouling community succession: �clean� (unfouled glass), �biofilmed� (natural biofilm on a flat surface), and �fouled� (natural biofilm on a rough surface of tubes of H. elegans adults). Substratum type had no effect on mean downward velocities of larvae carried in the water near the bottom. Larvae lingered on substrata after contact, whereas neutrally-bouyant particles did not. In flowing water, the duration of larval touchdowns on the bottom correlated with the degree of fouling (mean touchdown duration = 1.6s on clean, 2.6s on biofilmed, and 3.6s on fouled surfaces). In contrast, there was no correlation between degree of fouling and the number of times larvae landed on the bottom per horizontal distance they traveled in the ambient flow. In waves, vertical transport was more variable and larval touchdown durations were longer than in unidirectional flow. Thus, in realistic water flow, substratum chemistry and roughness can affect larval touchdown behavior.