Effect of ultraviolet radiation on biofilms and subsequent larval settlement of Hydroides elegans

Abstract

This study investigated the effect of UV-A and B (UVR) on larval settlement of the polychaete Hydroides elegans through their influence on biofilms. Multispecies biofilms were treated with 3 doses of UVR (10, ) at 2 environmentally realistic irradiance levels (4 and 2 W m -2 ) in the laboratory, and their ability to induce the settlement of H. elegans larvae was then examined in both laboratory and field conditions. For the field experiment, only 10 and 80 KJ m -2 doses under 4 W m -2 were used. In addition, this study evaluated the effects of UVR on monospecies bacterial biofilms and then their ability to induce larval settlement in the laboratory. Results demonstrated that the ability of multispecies biofilms to trigger larval settlement could be compromised as a result of enhanced UVR exposure. Although larval settlement on multispecies biofilms treated with the lowest UV dose (at both irradiance levels) was at the same level as that of the control, the exposure of biofilms to the highest dose significantly reduced their larval settlement triggering ability. Furthermore, UVR treatments decreased the percentage of metabolically active bacterial cells in monospecies biofilms; the effect increased with increasing UV dose. Larval settlement response to monospecies biofilms decreased with increasing UV dose, suggesting that the bacterial metabolic activity in biofilms is essential for the biofilms to have an inductive effect on larval settlement. This study suggests that enhanced UVR, which might occur due to ozone depletion, may have a significant effect on the larval settlement of H. elegans by affecting a biofilm's inductive cues. KEY WORDS: Hydroides elegans · Larval settlement · Biofilms · Ultraviolet radiation Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 304: [155][156][157][158][159][160][161][162][163][164][165][166] 2005 induce larval settlement. Consequently, biofilms play a key role in determining the recruitment success of invertebrates. The precise interactions among environmental conditions, biofilm dynamics and larval settlement, however, have been poorly investigated (Lau et al. 2005).Among all the potential environmental factors, ultraviolet radiation (UVR, 280 to 400 nm) is considered one of the most important variables in marine ecosystems. Although the ozone layer in the atmosphere filters out most of the biologically destructive UVR, depletion of ozone due to anthropogenic pollution results in an increase in short-wavelength UVR that reaches the earth's surface (Smith et al. 1992). This enhanced UVR causes significant unfavorable effects in marine ecosystems, as both UV-B (280 to 315 nm) and UV-A (315 to 400 nm) can penetrate to significant depths (Kirt 1994, Conde et al. 2000. For example, previous studies documented the negative effects of UVR on phytoplankton (e.g. Santas et al. 1998, Helbling et al. 2001 and references therein), bacterioplankton (e.g. Helbling et al. 1995, Jeffrey et al. 1996, Kaiser & Herndl 1997, Gustavson e...

Bacterial community succession and chemical profiles of subtidal biofilms in relation to larval settlement of the polychaete Hydroides elegans

“…First, the MilliQ water extracts of both studies induced larval settlement in a concentration-dependent manner, although the inductiveness of the MilliQ water extracts in both studies was dissimilar to that of the natural biofilm used as the positive control. In this study, the MilliQ water extracts from the 6d biofilm did not induce similar settlement to that induced by the 6d live natural biofilm control used in the study of Hung et al This observation further supports the hypothesis that cues from live biofilms are essential for H. elegans larval settlement (Hung et al, 2005) and that the inductive cues for H. elegans larval settlement are not restricted to the polar fraction. DCM extracts showed concentration-and biofilm-age-dependent inductiveness but induced abnormal metamorphosis at high concentrations (Figures 5b and c).…”

Manipulating thermal stress on rocky shores to predict patterns of recruitment of marine invertebrates under a changing climate

“…Alternatively, differences in biofilm composition produced by the different thermal regimes may be indirectly responsible for differences in larval settlement (Olivier et al 2000, Qian et al 2003. Similarly, Hung et al (2005) demonstrated that variation in UV exposure influences biofilm composition, which in turn influenced the larval settlement of the polychaete Hydroides elegans. Whether or not thermal variability indirectly influences larvae settlement by altering biofilm communities has yet to be empirically tested but could be an important indirect effect of changing temperature conditions.…”

Effect of Biofilm Formation by Pseudoalteromonas spongiae on Induction of Larval Settlement of the Polychaete Hydroides elegans

“…Larvae of H. elegans settle only in the presence of a metabolically active biofilm, however, not on a clean surface (21,27,51). Previous studies suggested that the bacterium-derived settlement cues were produced after bacteria attached to a surface and the cues were biofilm surface associated (11,13,19,25).…”