Seawater carbonate system in the experimental flasks.

<p>Data derived from DIC and pH_T, data are the means ± SD of three flasks sampled every three days before water exchange, along the 30 days duration of the experiment. (n = 10).</p

Growth of the bryozoan.

<p>Relative growth rate (RGR) of (<b>A</b>) <i>E. pilosa</i>, (<b>B</b>) <i>A. hirsutum</i> colonies during the 30 days of incubations at 460 µatm, 1200 µatm and 3150 µatm pCO₂. Data are the mean ± SE of the growth rates in % in n = 10 flasks. One-way ANOVAs, statistical significance: **: p≤0.01.</p

Experimental design.

<p>(<b>A</b>) Schematic representation of the incubation system. (<b>B</b>) Schematic representation of one experimental <i>F. serratus</i> section bearing the three epibionts, both sides of the thallus were bearing epibionts.</p

Seasonal variation in the antifouling defence of the temperate brown alga <i>Fucus vesiculosus</i>

<div><p>The important role of marine epibiotic biofilms in the interactions of the host with its environment has been acknowledged recently. Previous studies with the temperate brown macroalga <i>Fucus vesiculosus</i> have identified polar and non-polar compounds recovered from the algal surface that have the potential to control such biofilms. Furthermore, both the fouling pressure and the composition of the epibiotic bacterial communities on this macroalga varied seasonally. The extent to which this reflects a seasonal fluctuation of the fouling control mechanisms of the host is, however, unexplored in an ecological context. The present study investigated seasonal variation in the anti-settlement activity of surface extracts of <i>F. vesiculosus</i> against eight biofilm-forming bacteria isolated from rockweed-dominated habitats, including replication of two populations from two geographically distant sites. The anti-settlement activity at both sites was found to vary temporally, reaching a peak in summer/autumn. Anti-settlement activity also showed a consistent and strong difference between sites throughout the year. This study is the first to report temporal variation of antifouling defence originating from ecologically relevant surface-associated compounds.</p> </div

Growth of the juveniles of <i>S. spirorbis</i>.

<p>Growth in µm of the tubes of the juveniles of <i>S. spirorbis</i> during 24 h in light and dark condition exposed to pCO₂ of 460 µatm, 1200 µatm and 3150 µatm. Data are the mean ± SE newly formed tubes sections in µm per worm per flask Two-way ANOVA, n = 5, statistical significance: ***: p≤0.001.</p

Growth and reproduction of <i>S. spirorbis</i>.

<p>(<b>A</b>) Growth of the tubes of <i>S. spirorbis</i> during the 30 days of incubations at 460 µatm, 1200 µatm and 3150 µatm pCO₂, data are the mean ± SE of newly formed tubes sections in mm per worm per flask. (<b>B</b>) Settlement of <i>S. spirorbis</i> during the 30 days of incubations at 460 µatm, 1200 µatm and 3150 µatm pCO₂, data are the mean ± SE of the number of juveniles settled per adult between flasks. One-way ANOVAs, n = 10, statistical significance: ***: p≤0.001, **: p≤0.01, *: p≤0.05, •: p<0.1.</p

Results of distance-based linear model (DistLM).

<p>Relationship between <i>Fucus serratus</i> surface chemistry composition and the predictor variables. Model output contains only variables of the best fit.</p

Results of distance-based linear model (DistLM).

<p>Relationship between <i>Fucus vesiculosus</i> surface chemistry composition and the predictor variables. Model output contains only variables of the best fit.</p

MDS (multi-dimensional scaling) plot of the variance/similarity in <i>Fucus vesiculosus</i> surface extract composition originating from different seasons.

<p>Symbols represent single monthly samples of <i>F</i>. <i>vesiculosus</i> individuals within the four seasons (<i>n</i> = 18 per season; exceptions: spring <i>n</i> = 17, summer <i>n</i> = 15).</p

Pairwise test results (ANOSIM) for <i>Fucus serratus</i> chemical composition of surface extracts.

<p>Pairwise test results (ANOSIM) for <i>Fucus serratus</i> chemical composition of surface extracts.</p